WO2021107159A1 - 吸水性シートおよびそれを含む吸収性物品 - Google Patents

吸水性シートおよびそれを含む吸収性物品 Download PDF

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Publication number
WO2021107159A1
WO2021107159A1 PCT/JP2020/044517 JP2020044517W WO2021107159A1 WO 2021107159 A1 WO2021107159 A1 WO 2021107159A1 JP 2020044517 W JP2020044517 W JP 2020044517W WO 2021107159 A1 WO2021107159 A1 WO 2021107159A1
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Prior art keywords
water
base material
absorbent
absorbing agent
absorbing
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PCT/JP2020/044517
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English (en)
French (fr)
Japanese (ja)
Inventor
達史 平内
遼亮 藤川
貞巖 ▲より▼元
貴洋 北野
Original Assignee
株式会社日本触媒
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Application filed by 株式会社日本触媒 filed Critical 株式会社日本触媒
Priority to CN202311262915.5A priority Critical patent/CN117257553A/zh
Priority to CN202080082864.6A priority patent/CN114746058A/zh
Priority to JP2021561588A priority patent/JP7410175B2/ja
Publication of WO2021107159A1 publication Critical patent/WO2021107159A1/ja
Priority to ZA2022/05800A priority patent/ZA202205800B/en
Priority to JP2023215752A priority patent/JP7617238B2/ja

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F13/534—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having an inhomogeneous composition through the thickness of the pad
    • A61F13/535—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having an inhomogeneous composition through the thickness of the pad inhomogeneous in the plane of the pad, e.g. core absorbent layers being of different sizes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F13/534—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having an inhomogeneous composition through the thickness of the pad
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B01J20/261—Synthetic macromolecular compounds obtained by reactions only involving carbon to carbon unsaturated bonds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
    • B01J20/28016—Particle form
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/44—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties the fleeces or layers being consolidated by mechanical means, e.g. by rolling
    • D04H1/46—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties the fleeces or layers being consolidated by mechanical means, e.g. by rolling by needling or like operations to cause entanglement of fibres
    • D04H1/492—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties the fleeces or layers being consolidated by mechanical means, e.g. by rolling by needling or like operations to cause entanglement of fibres by fluid jet
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F2013/530131—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium being made in fibre but being not pulp
    • A61F2013/530226—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium being made in fibre but being not pulp with polymeric fibres
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F2013/530131—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium being made in fibre but being not pulp
    • A61F2013/530379—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium being made in fibre but being not pulp comprising mixtures of fibres
    • A61F2013/530386—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium being made in fibre but being not pulp comprising mixtures of fibres with pulp and polymeric
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F2013/530481—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F2013/530481—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials
    • A61F2013/530489—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials being randomly mixed in with other material
    • A61F2013/530496—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials being randomly mixed in with other material being fixed to fibres
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F2013/530868—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium characterized by the liquid distribution or transport means other than wicking layer
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F13/534—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having an inhomogeneous composition through the thickness of the pad
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Definitions

  • the present invention relates to a water-absorbent sheet and an absorbent article containing the same.
  • Water-absorbent resin (SAP / Super Absorbent polymer) is a water-swellable water-insoluble polymer gelling agent, which is a sanitary material such as disposable diapers, sanitary napkins and incontinence products for adults, and a soil water-retaining agent for agriculture and gardening. , Industrial water-stopping agent, etc., are used for various purposes.
  • absorbent articles are generally manufactured in a paper diaper manufacturing factory as an absorber in which a water-absorbent resin and a fiber material are mixed and individually molded for each absorbent article, and have various shapes depending on the purpose. (For example, it is processed into an hourglass type, a diaper type, an oval type, etc. when viewed on a flat surface). Since these absorbents are individually molded, they can be processed into any shape, and the amount of fibers and water-absorbent resin can be easily adjusted for each absorbent article, which is the mainstream of the current paper diapers.
  • the water-absorbent sheet has a structure in which water-absorbent resin particles are sandwiched and fixed between the upper and lower sheets (particularly a non-woven fabric sheet), and after usually producing a long continuous sheet, the long continuous sheet is cut to have a width of about 10 cm. Make a rectangle with a length of several tens of centimeters and incorporate it into a paper diaper (for example, International Publication No. 2010/143635).
  • paper diapers made of water-absorbent sheets have a short history, and there have been few developments of water-absorbent resins suitable for water-absorbent sheets or proposals for parameters.
  • the conventional water-absorbent resin for disposable diapers is used as it is for the water-absorbent sheet.
  • the present inventors release the absorbed liquid in the introduction direction of the absorbed liquid when pressure is applied to the water-absorbent sheet. It was found that "backtracking” is likely to occur. “Return” is also called Re-wet. Then, it was found that the problem of the occurrence of reversion becomes remarkable when the liquid is introduced intermittently a plurality of times (particularly three times or more) and the amount of the liquid introduced is large. When reversion occurs, the skin in contact with the water-absorbent sheet comes into contact with the reverted liquid and is exposed to a high humidity condition. Therefore, the user not only causes discomfort, but also tends to cause a rash on the skin in contact with the water-absorbent sheet.
  • the present invention has been made in view of the above circumstances, and even if the liquid is intermittently introduced a plurality of times (particularly three or more times), the liquid discharge from the water-absorbent sheet due to reversion is significantly reduced. It is an object of the present invention to provide a novel water-absorbent sheet capable of providing a new water-absorbent sheet.
  • the present inventors have made extensive studies in order to solve the above problems. As a result, it is a water-absorbent sheet having a first base material, a second base material, a water-absorbing layer located between the first base material and the second base material.
  • the water-absorbing layer contains a particulate water-absorbing agent, the surface of the first base material forms a liquid-absorbing surface that directly absorbs the liquid, and the thickness (mm) of the second base material is relative to the above.
  • the water-absorbent sheet according to another embodiment of the present invention is a water-absorbent sheet located between a first base material, a second base material, the first base material, and the second base material.
  • a water-absorbing sheet having a layer, wherein the water-absorbing layer contains a particulate water-absorbing agent, the water-absorbing layer is not arranged on the first base material, and the thickness of the second base material is When the ratio of the thickness (mm) of the first base material to (mm) (thickness of the first base material (mm) / thickness of the second base material (mm)) is 1.5 or more and less than 14. is there.
  • the water-absorbent sheet according to another embodiment of the present invention is a water-absorbent sheet located between the first base material, the second base material, the first base material, and the second base material.
  • the water-absorbent sheet according to still another embodiment of the present invention is a water-absorbent layer located between a first base material, a second base material, the first base material, and the second base material.
  • a water-absorbent sheet comprising, and a wrapping sheet to be arranged on the surface of the first base material, wherein the water-absorbent layer contains a particulate water-absorbing agent, and the surface of the wrapping sheet directly absorbs a liquid.
  • a liquid absorbing surface is formed to absorb, and the ratio of the thickness of the first base material to the thickness of the second base material (thickness of the first base material (mm) / thickness of the second base material (mm). )) Is 1.5 or more and less than 14.
  • the water-absorbent sheet of the first invention has a first base material, a second base material, and a water-absorbent layer located between the first base material and the second base material.
  • a water-absorbing sheet wherein the water-absorbing layer contains a particulate water-absorbing agent, and the surface of the first base material forms a liquid-absorbing surface that directly absorbs the liquid, and the second base material has a water-absorbing surface.
  • the ratio of the thickness (mm) of the first base material to the thickness (mm) is 1.5 or more and less than 14. Is.
  • Water-absorbent sheet refers to a structure in which a water-absorbent resin (particulate water-absorbent agent) is supported between two or more long base materials.
  • the water-absorbent sheet may use an adhesive or a hot-melt adhesive for adhering the base materials to each other and / or adhering the base material to the particulate water-absorbing agent.
  • the water-absorbent sheet may contain other components (fiber component, antibacterial agent, deodorant, etc.) in addition to the particulate water-absorbing agent.
  • a water absorbing sheet that contains other sheets.
  • a water-absorbent sheet containing another sheet in addition to the two base materials sandwiching the particulate water-absorbing agent or the like, as long as it does not hinder the solution of the problem of the present invention. May be good.
  • a water-absorbent sheet in which a particulate water-absorbing agent or the like is sandwiched between two base materials is a preferred embodiment.
  • the water-absorbent sheet is in the form of a continuous sheet or in the form of a roll obtained by winding the continuous sheet.
  • the continuous sheet is cut into an appropriate shape (rectangular shape, etc.) and then incorporated into an absorbent article (paper diaper, sanitary napkin, incontinence pad, etc.).
  • Absorbent items such as disposable diapers, sanitary napkins, and incontinence pads are placed on the side that comes into contact with the body and the absorber that absorbs and retains body fluids such as urine and menstrual blood excreted from the body.
  • the water-absorbent sheet can be used as the absorber.
  • a conventional disposable diaper is an absorbent article that is individually molded for each disposable diaper and has a shape that fits the buttocks. Therefore, such an absorber differs from the water-absorbent sheet of the present invention in technical properties.
  • water-absorbent resin refers to a water-soluble component having a water swelling property (CRC) of 5 g / g or more as defined by ERT441.2-02 and a water-soluble component defined by ERT470.2-02.
  • Ext refers to a polymer gelling agent having an Ext) of 50% by mass or less.
  • the water-absorbent resin is preferably a hydrophilic crosslinked polymer obtained by crosslinking and polymerizing an unsaturated monomer having a carboxyl group.
  • the shape of the water-absorbent resin is sheet-like, fibrous, film-like, particle-like, gel-like, or the like.
  • the water-absorbent sheet according to the embodiment of the present invention uses a particulate water-absorbent resin.
  • the "water-absorbent resin” is not limited to the embodiment in which the total amount (100% by mass) is only the water-absorbent resin.
  • a water-absorbent resin composition containing additives and the like may be used as long as the above-mentioned CRC and Ext are satisfied.
  • the "water-absorbent resin” is a concept including an intermediate in the manufacturing process of the water-absorbent resin. For example, a water-containing gel-like crosslinked polymer after polymerization, a dried polymer after drying, a water-absorbent resin powder before surface cross-linking, and the like may also be referred to as "water-absorbent resin".
  • water-absorbent resin in addition to the water-absorbent resin itself, the water-absorbent resin composition and the intermediate may be generically referred to as "water-absorbent resin”.
  • water-absorbing agent means an absorbing gelling agent for absorbing an aqueous liquid (liquid) containing a water-absorbing resin as a main component.
  • the aqueous liquid (liquid) is not particularly limited as long as it is a liquid containing water as well as water.
  • the aqueous liquid absorbed by the water-absorbent sheet according to the embodiment of the present invention is urine, menstrual blood, sweat, or other body fluid.
  • the "particulate water-absorbing agent” means a particulate (powder-like) water-absorbing agent (corresponding to a particulate water-absorbing resin because the water-absorbing agent contains a water-absorbent resin as a main component). ..
  • the concept of "particulate water-absorbing agent” includes both a single particle-like water-absorbing agent and an aggregate of a plurality of particulate water-absorbing agents.
  • the term “particulate” means having the form of particles.
  • particle refers to a relatively small fragment of a substance, and has a size of several ⁇ to several mm (“particle”, edited by the editorial committee of the McGraw-Hill Science and Technology Glossary Dictionary, "Maglow Hill Science”.
  • the form of the water absorbing agent is not limited to the particulate water absorbing agent.
  • the present invention will be described by taking a particulate water-absorbing agent as an example, but the “particulate water-absorbing agent” can be read as a “water-absorbing agent”.
  • “particulate water absorption agent” may be simply referred to as "water absorption agent”.
  • the weight average particle size of the particulate water-absorbent is 200 to 600 ⁇ m.
  • the weight average particle size of the particulate water absorbing agent is less than 200 ⁇ m, the handleability may be deteriorated.
  • the weight average particle diameter of the particulate water absorbing agent exceeds 600 ⁇ m, the texture of the water absorbing sheet may deteriorate.
  • the weight average particle size of the particulate water-absorbing agent is preferably 250 to 500 ⁇ m, more preferably 300 to 450 ⁇ m.
  • 95% by mass or more of the entire particulate water-absorbing agent preferably has a particle size of 850 ⁇ m or less, and 98% by mass or more of the entire particulate water-absorbent agent has a particle size of 850 ⁇ m or less. It is more preferable that substantially 100% by mass of the entire particulate water absorbing agent has a particle size of 850 ⁇ m or less. In the examples of the present application, substantially 100% by mass of the entire particulate water absorbing agent has a particle size of 850 ⁇ m or less.
  • the method for measuring the weight average particle size is described in US Pat. No.
  • the particulate water-absorbing agent contains a water-absorbent resin as a polymer (also referred to as a particulate water-absorbent resin or water-absorbent resin particles) as a main component.
  • the particulate water absorbing agent contains 60 to 100% by mass, preferably 70 to 100% by mass, more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass, particularly preferably a water absorbing resin as a polymer. Contains 95-100% by mass.
  • the remainder of the particulate water absorbing agent may optionally contain water, additives (inorganic fine particles, polyvalent metal cations, etc.) and the like.
  • the particulate water-absorbing agent used in the examples of the present application contains 80 to 100% by mass of a water-absorbent resin.
  • the upper limit of the water-absorbent resin in the particulate water-absorbing agent is, for example, 100% by mass, 99% by mass, 97% by mass, 95% by mass, and 90% by mass. Then, preferably, in addition to the water-absorbent resin, 0 to 10% by mass of components, particularly water, additives (inorganic fine particles, polyvalent metal cations) and the like are further contained.
  • the preferable water content of the particulate water absorbent is 0.2 to 30% by mass.
  • the water-absorbent resin composition in which components such as water and additives are integrated with and / or mixed with the water-absorbent resin is also included in the "particulate water-absorbent agent". ..
  • water-absorbent resins that are the main components of particulate water-absorbents include polyacrylic acid (salt) -based resins, polysulfonic acid (salt) -based resins, maleic anhydride (salt) -based resins, polyacrylamide-based resins, and polyvinyl alcohol.
  • examples thereof include based resins, polyethylene oxide-based resins, polyaspartic acid (salt) -based resins, polyglutamic acid (salt) -based resins, polyarginic acid (salt) -based resins, starch-based resins, and cellulose-based resins.
  • a polyacrylic acid (salt) -based resin is preferably used as the water-absorbent resin.
  • polyacrylic acid (salt) refers to polyacrylic acid and / or a salt thereof.
  • the polyacrylic acid (salt) is a polymer containing a repeating unit of acrylic acid and / or a salt thereof (hereinafter referred to as "acrylic acid (salt)”) as a main component and further containing a graft component as an optional component.
  • the polyacrylic acid (salt) is obtained by polymerization of acrylic acid (salt), hydrolysis of polyacrylamide, polyacrylonitrile, or the like.
  • the polyacrylic acid (salt) is obtained by polymerization of acrylic acid (salt).
  • “included as a main component” means that the amount of acrylic acid (salt) used when polymerizing polyacrylic acid (salt) is the entire monomer (however, excluding the internal cross-linking agent) used for polymerization. On the other hand, it is usually 50 to 100 mol%, preferably 70 to 100 mol%, more preferably 90 to 100 mol%, still more preferably substantially 100 mol%.
  • EDANA is an abbreviation for European Disposables and Nonwovens Associations.
  • ERT is an abbreviation for EDANA Recommended Test Methods, which is a European standard (substantially a global standard) for measuring water-absorbent resins. In this specification, unless otherwise specified, the physical characteristics of the water-absorbent resin are measured in accordance with the 2002 version of ERT.
  • salt means “-acid and / or a salt thereof”.
  • (Meta) acrylic means "acrylic and / or methacrylic”.
  • the unit of volume "liter” may be expressed as “l” or “L”.
  • Mass% may be expressed as "wt%”.
  • the water-absorbent sheet of the present invention has a first base material, a second base material, and a water-absorbent layer located between the first base material and the second base material.
  • the water absorbing layer contains a particulate water absorbing agent
  • the surface of the first base material forms a liquid absorbing surface that directly absorbs the liquid
  • the thickness of the second base material is 1.5 or more and less than 14.
  • the thickness (mm) of the first base material forming the liquid-absorbing surface that directly absorbs the liquid is 1.5 or more with respect to the thickness (mm) of the second base material. It is less than 14. That is, the first substrate is significantly thicker than the second substrate. A liquid absorbing surface that directly absorbs the liquid is formed on the surface of the first base material that is significantly thicker than the second base material.
  • the water-absorbent sheet absorbs water located between the first base material, the second base material, the first base material, and the second base material.
  • a water-absorbing sheet having a layer, wherein the water-absorbing layer contains a particulate water-absorbing agent, the water-absorbing layer is not arranged on the first base material, and the thickness of the second base material is The ratio of the thickness of the first base material to the thickness of the first base material (thickness of the first base material (mm) / thickness of the second base material (mm)) is 1.5 or more and less than 14.
  • the water-absorbing layer is arranged. Not considered to be done. It is assumed that the cause of the movement is, for example, vibration generated when the water-absorbent sheet is the final product and is transported or transported.
  • the particulate water absorbing agent is intentionally sprayed or arranged on the first base material, it is not in the category of this embodiment.
  • the present inventors carry out the present application in a conventional water-absorbent sheet (for example, a water-absorbent sheet having the same thickness of the first base material and the second base material in order to obtain a thin water-absorbent sheet).
  • a conventional water-absorbent sheet for example, a water-absorbent sheet having the same thickness of the first base material and the second base material in order to obtain a thin water-absorbent sheet.
  • the distance between the liquid absorption surface of the first base material and the water absorption layer is increased by making the first base material on the liquid introduction side significantly thicker than the second base material. It can be lengthened so that the liquid introduced from the water absorption surface does not stay on the water absorption surface (furthermore, the introduced liquid does not stay locally), and the lower layer is responsible for the water absorption function.
  • the liquid can be efficiently delivered to the water absorption layer. Specifically, when the liquid passes through the first base material, the liquid has high diffusivity in the surface direction, and the diffused liquid (for example, urine) is widely and uniformly transferred to the entire surface of the water absorption layer. It is thought that it is because of (migrating).
  • the liquid when the absorbed liquid reaches the water absorption layer, the liquid is diffused in the surface direction. Therefore, even if a large amount of the liquid is introduced into the water absorption layer, the water absorption layer spreads in the surface direction instead of locally. It will absorb the liquid. Therefore, the liquid can be sufficiently absorbed and retained in the water absorption layer. It is also considered that the liquid diffusible function of the hydrophilic pulp contained in the conventional absorber is imparted to the first base material. Then, once the liquid is absorbed by the water-absorbing layer, since the first base material is significantly thick, the liquid absorbed by the water-absorbing layer reverts and returns to the liquid-absorbing surface of the first base material.
  • the water-absorbing agent is mainly responsible for the water-absorbing function in the water-absorbing layer.
  • the role of the water-absorbing agent becomes even more important.
  • the first base material is significantly thick, it is difficult for the liquid once introduced into the water absorbing agent to return to the liquid absorbing surface of the first base material.
  • the lateral leakage is a phenomenon in which the liquid that could not be absorbed instantly after reaching the water absorption layer leaks from the water absorption sheet in the surface direction.
  • the particle water absorbing agent being formed in the form of a sheet (layer) and maximizing the liquid diffusion in the surface direction of the water absorbing layer, it is possible to revert to the first base material. It is configured to suppress leakage (lateral leakage) in the surface direction from the water-absorbent sheet while suppressing it.
  • the diffusivity of the liquid in the surface direction when the liquid passes through the first base material is high.
  • High and diffused liquids eg, urine
  • a particulate water absorbent that has a significantly higher absorption rate and acts like a tank. That is, when the absorbed liquid reaches the water absorption layer, the liquid is diffused in the surface direction. Therefore, even if a large amount of the liquid is introduced into the water absorption layer, the water absorption layer spreads in the surface direction instead of locally. It will absorb the liquid.
  • the liquid can be sufficiently absorbed and retained in the water absorbing layer, and the leakage from the water absorbing sheet in the plane direction is significantly low. Then, even if the liquid that could not be absorbed by the water absorption layer tries to revert, the first base material is significantly thicker than the second base material, so that the liquid can be prevented from rising to the skin. Therefore, the "specific return amount evaluation" can be made excellent, and leakage in the plane direction can be suppressed.
  • a water-absorbent sheet or an absorbent article designed to suppress the amount of reversion under general conditions does not always give excellent results in the "specific return amount evaluation" of the present application.
  • the water-absorbent sheet according to the embodiment of the present invention is an absorbent article (for example, an absorbent article used during a time when an infant whose bladder is still small is actively moving around, such as in the daytime, when he / she begins to learn to run. It is suitable as a diaper), but of course the usage pattern is not limited to this.
  • the mechanisms and the like described herein do not limit the technical scope of the claims of the present application.
  • FIG. 1 is a schematic view showing a cross section of the water-absorbent sheet 10 according to the embodiment of the present invention.
  • 2 to 4 are schematic views showing a cross section of the water-absorbent sheet 10 according to another embodiment of the present invention.
  • the arrow indicates the direction in which the absorbed liquid is introduced.
  • the first base material 11 is located on the side where the liquid absorbed by the water absorbing layer 12 (the liquid to be absorbed) is introduced. That is, the first base material 11 is arranged on the liquid discharge side (for example, the skin side in the case of paper diapers). As a result, the first base material 11 forms a liquid absorbing surface that directly absorbs the liquid.
  • the water absorption layer 12 is arranged between the first base material 11 and the second base material 13.
  • the water absorbing layer 12 contains the particulate water absorbing agent 14.
  • the water absorbing layer 12 shows a state in which the particulate water absorbing agent 14 is present between the first base material 11 and the second base material 13.
  • the water absorption layer 12 is a particle that is in contact with (or is adhered to) the first base material 11 and is in contact with (or is adhered to) the particulate water absorbing agent 14 and the second base material 13.
  • the state water absorbing agent 14 is contained. Some of the particulate water absorbing agents 14 may not be in contact with (or may not be adhered to) the respective base materials 11 and 13, and may be detached from the respective base materials 11 and 13.
  • the water-absorbing "layer” does not mean only a continuum such as a sheet, but any one that exists between the first base material 11 and the second base material 13 with a certain thickness. It may be in the form.
  • an adhesive may be used.
  • the particulate water absorbing agent 14 may be present in the first base material 11.
  • the particulate water absorbing agent 14 in the first base material 11 is, for example, in contact with the particulate water absorbing agent 14 that has come into contact with (or has been fixed to) the first base material 11 or the second base material 13.
  • the particulate water-absorbing agent 14 (or fixed) may be desorbed and captured in the first base material 11.
  • the content ratio of the particulate water absorbing agent 14 in the first base material 11 is based on the particulate water absorbing agent 14 contained in the entire water absorbing sheet 10. It is preferably 5% or more, more preferably 10% or more, still more preferably 20% or more, and even more preferably 30% or more.
  • the upper limit is not particularly limited, but is 90% or less, 70% or less, and 50% or less in the preferred order.
  • the content ratio of the particulate water absorbing agent 14 in the first base material 11 to the particulate water absorbing agent 14 contained in the entire water absorbing sheet 10 is calculated by the method of Examples described later.
  • the water-absorbent sheet 10 has a wrapping sheet 16.
  • the wrapping sheet 16 is a first group for the purpose of maintaining the shape of the water-absorbent sheet 10, which is a structure in which the particulate water-absorbing agent 14 is supported between the first base material 11 and the second base material 13.
  • the particulate water absorbing agent 14 is the first.
  • the wrapping sheet 16 When the wrapping sheet 16 is not provided, for example, by a method of sealing by adhering the base materials 11 and 13 to each other, and by surface treatment of the first base material 11, the outer surface of the first base material 11 ( There is a method of suppressing the transfer to the liquid absorption surface) that directly absorbs the liquid. It is preferable to have the wrapping sheet 16 as a method of preventing the particulate water absorbing agent 14 from falling off from the water absorbing sheet 10 while maintaining the effect of the present application.
  • the wrapping sheet 16 is arranged on the first base material 11, and is folded so as to wrap the entire water absorbing layer 12 and the second base material 13. Therefore, the wrapping sheet 16 covers the entire first base material 11, the water absorption layer 12, and the second base material 13. With such a configuration, it is possible to prevent the particulate water absorbing agent 14 from falling off from the water absorbing sheet 10.
  • the wrapping sheet 16 does not need to cover the entire first base material 11, the water absorption layer 12, and the second base material 13.
  • the wrapping sheet 16 is arranged on the first base material 11, bent so as to wrap the side surface of the water absorbing layer 12 and the side surface of the second base material 13, and absorbs the liquid of the second base material 13.
  • the wrapping sheet 16 may be folded on the surface opposite to the surface to be formed (that is, the surface provided with the water absorption layer 12). That is, in the wrapping sheet 16, one end of the wrapping sheet 16 and the other end of the wrapping sheet 16 overlap on the surface of the second base material 13 opposite to the surface on which the water absorption layer 12 is provided.
  • the wrapping sheet 16 covers the liquid absorbing surface and the side surface of the first base material 11, the side surface of the water absorbing layer 12, and the side surface of the second base material 13, and the water absorbing layer of the second base material 13. It covers all or part of the surface opposite to the surface on which the 12 is provided.
  • one end of the wrapping sheet 16 and the other end of the wrapping sheet 16 may be separated from each other on the surface of the second base material 13 opposite to the surface on which the water absorption layer 12 is provided. ..
  • the wrapping sheet 16 is placed on the first base material 11, bent so as to wrap the side surface of the water absorption layer 12 and the side surface of the second base material 13, and the second base material.
  • One end of the wrapping sheet 16 and the other end of the wrapping sheet 16 are arranged apart from each other on the surface opposite to the liquid absorbing surface (that is, the surface provided with the water absorbing layer 12) that directly absorbs the liquid of 13. ing.
  • the wrapping sheet 16 covers the liquid absorbing surface and the side surface of the first base material 11, the side surface of the water absorbing layer 12, and the side surface of the second base material 13, and the water absorbing layer of the second base material 13. It covers a part of the surface opposite to the surface on which the 12 is provided.
  • the wrapping sheet 16 is not an essential configuration in the water absorbing sheet 10 according to the present invention
  • the water absorbing sheet 10 according to the present invention is provided with the wrapping sheet 16 in such a configuration so that the particulate water absorbing agent 14 absorbs water. It is possible to prevent the sex sheet 10 from falling off.
  • the water-absorbent sheet 10 has at least a wrapping sheet 16 to be arranged on the surface of the first base material 11.
  • the first base material 11 forms a liquid absorbing surface that directly absorbs the liquid.
  • the water-absorbent sheet 10 having the wrapping sheet 16 if the wrapping sheet 16 forms a liquid-absorbing surface that directly absorbs the liquid, it can be paraphrased as follows; A water-absorbent sheet having a base material, a water-absorbent layer located between the first base material and the second base material, and a wrapping sheet arranged on the surface of the first base material.
  • the water absorbing layer contains a particulate water absorbing agent, the surface of the wrapping sheet forms a liquid absorbing surface that directly absorbs the liquid, and the first base material has a thickness relative to the thickness of the second base material.
  • the ratio of the thickness of the base material is 1.5 or more and less than 14.
  • an adhesive may be used as a method of fixing the wrapping sheet 16 to the base materials 11 and 13, for example.
  • the first base material 11 and the particulate water absorbing agent 14 in the water absorbing layer 12 are preferably in contact with each other directly or via an adhesive, and / or the second base material 13 and the water absorbing layer 13 are in contact with each other. It is preferable that the particulate water absorbing agent 14 in No. 12 is in contact with the water absorbing agent 14 directly or via an adhesive.
  • the water-absorbent sheet of the present invention is substantially a particulate water-absorbing agent sandwiched between the first base material and the second base material; the first base material and the second base material.
  • More preferred embodiments include a first substrate; a second substrate; a first substrate, a particulate water absorbent sandwiched between the second substrates; a particulate water absorbent and a second substrate. It has a simple structure consisting only of an adhesive that adheres a particulate water-absorbing agent to the base material to the second base material; and a wrapping sheet that wraps all of them. That is, although the water-absorbent sheet of the present invention has a simple structure, the specific return amount can be effectively reduced.
  • the ratio of the thickness (mm) of the first base material to the thickness (mm) of the second base material is 1.5 or more and less than 14.
  • the ratio of the thickness (mm) of the first base material to the thickness (mm) of the second base material is less than 1.5, the liquid absorption surface of the first base material, the water absorption layer, and the second base material The distance between the water absorption layer and the second base material may not be sufficiently secured, and the liquid once reaching the water absorption layer and the second base material may return.
  • the ratio of the thickness (mm) of the first base material to the thickness (mm) of the second base material is 14 or more, the liquid absorption surface of the first base material and the water absorption layer are separated. As a result, leakage in the surface direction may occur before the liquid absorbed from the liquid absorbing surface of the first base material reaches the water absorbing layer.
  • the lower limit of the ratio of the thickness (mm) of the first base material to the thickness (mm) of the second base material is preferably 1.7 or more, more preferably 2.5 or more, still more preferably 3. It is .2 or more, even more preferably 3.4 or more, particularly preferably 3.5 or more, and most preferably 3.6 or more.
  • the upper limit of the ratio of the thickness (mm) of the first base material to the thickness (mm) of the second base material is preferably 12 or less, more preferably 10 or less, still more preferably 9 or less. Even more preferably, it is 8 or less. When the ratio of the thickness (mm) of the first base material to the thickness (mm) of the second base material is within such a range, the reversion can be significantly reduced.
  • the ratio of the thickness (mm) of the first base material to the thickness (mm) of the second base material is 1.5 or more and less than 14. Further, in the water-absorbent sheet according to the embodiment of the present invention, the ratio of the thickness (mm) of the first base material to the thickness (mm) of the second base material is 1.7 or more and less than 14. It is preferably 3 or more and 12 or less, and more preferably 3.4 or more and 10 or less.
  • the water-absorbent sheet according to the embodiment of the present invention may have a first base material having a low density and a bulky form, but can be made thinner than an absorber used for a conventional absorbent article.
  • the thickness thereof is, for example, 40% RH to 50% RH, preferably 15 mm or less, more preferably 10 mm or less, still more preferably 7 mm or less, and particularly preferably 5 mm. Below, it is most preferably 4 mm or less.
  • the lower limit of the thickness is preferably 0.2 mm or more, more preferably 0.3 mm or more, still more preferably 0.5 mm or more, in consideration of the strength of the water absorbing sheet and the diameter of the particulate water absorbing agent.
  • the thickness of the water-absorbent sheet used in the examples of the present application was 2 to 5 mm.
  • the thickness of the first base material, the second base material, the lapping sheet, and the water-absorbent sheet in the present application is a dial thickness gauge large type (thickness measuring instrument) (manufactured by Ozaki Seisakusho Co., Ltd., model number: JB, measurement). Child: Measured using an anvil top and bottom ⁇ 50 mm). The number of measurement points was 5 points at different points on the sheet to be measured, and the measurement was performed twice at each point, and the measured values were the average value of a total of 5 points. When measuring the thickness, the thickness was measured by slowly releasing the hand from the handle so that pressure was not applied to the sheet to be measured as much as possible.
  • the sheet to be measured is pasted flat on a plate having a constant thickness so that wrinkles and distortion do not occur at the measurement location, and the plate is set on the lower stylus of the thickness measuring instrument. To do. Next, after bringing the upper stylus of the thickness measuring instrument close to a height position of 2 to 3 mm from the sheet to be measured, slowly release the hand from the handle to measure the combined thickness of the sheet and the plate to be measured.
  • the content of the particulate water-absorbing agent contained in the water-absorbent sheet is preferably 50 to 400 g / m 2 , more preferably 100 to 350 g / m 2 , and even more preferably 125 to 250 g / m. It is 2.
  • the ratio of the region containing the particulate water absorbing agent (hereinafter, also referred to as "the ratio of the region where the particulate water absorbing agent 14 exists").
  • the area is preferably more than 75%, more preferably more than 80%, and even more preferably more than 90%.
  • the upper limit of the ratio of the region containing the particulate water absorbing agent on the surface of the first base material on the water absorbing layer side is not particularly limited, but is practically 99.5% or less in terms of area.
  • the particulate water-absorbing agent By providing the particulate water-absorbing agent in such a range, the particulate water-absorbing agent is arranged in a well-balanced manner, and the effect of reducing the amount of return is further exhibited.
  • the ratio of the region containing the particulate water-absorbing agent on the surface of the first base material on the water-absorbing layer side is the particle on the surface of the second base material on the water-absorbing layer side (the surface on which the particulate water-absorbing agent is arranged). It is the same as the ratio of the region containing the water absorbing agent.
  • the ratio of the region containing the particulate water-absorbing agent on the surface of the first base material on the water-absorbing layer side can be controlled by adjusting the spraying region of the particulate water-absorbing agent during the production of the water-absorbent sheet. ..
  • the ratio of the region containing the particulate water-absorbing agent on the surface of the first base material on the water-absorbent layer side. can be calculated.
  • the cross section of the water-absorbent sheet is photographed, and the interface between the first base material or the second base material and the water-absorbing layer is a region where the particulate water-absorbing agent is present and the particle-like water-absorbing agent is not present.
  • the ratio of the region containing the particulate water absorbing agent can be calculated by classifying the regions into regions, summing each region, and calculating the ratio thereof.
  • the region to be embossed may be the entire surface of the water-absorbent sheet surface or a part thereof.
  • the liquid can be easily diffused in the longitudinal direction.
  • the region serves as a passage (liquid transport passage) for flowing a large amount of liquid.
  • the embossed region may be provided linearly, curvedly, or corrugated.
  • the particulate water absorbing agent may be sprayed on the entire surface of the water absorbing sheet, or a region where the particulate water absorbing agent does not exist may be provided in a part thereof. That is, in the water absorbing layer between the first base material and the second base material, the particulate water absorbing agent may be sprayed on the entire surface of the water absorbing layer, and the particulate water absorbing agent is not applied to a part of the water absorbing layer. An existing area may be provided.
  • the non-existent region of the particulate water-absorbing agent is preferably provided in a channel shape (streak shape) in the longitudinal direction of the water-absorbing sheet.
  • the region serves as a passage (liquid transport passage) for flowing a large amount of liquid.
  • the non-existent region of the particulate water absorbing agent may be provided linearly, curvedly, or corrugated.
  • the first base material When a region in which the particulate water absorbing agent does not exist is provided in a part of the water absorbing layer, the first base material preferably has elasticity, and the elongation rate of the first base material is 10% or more. Is more preferable.
  • the region containing the particulate water-absorbing agent in the water-absorbing layer between the first base material and the second base material, is substantially a particulate water-absorbing agent. It is arranged with a gap not included, and the elongation rate of the first base material is 10% or more.
  • the particulate water absorbent is particles on a portion of the first or second substrate. A non-existent area of the water absorbing agent is provided and sprayed. As a result, the particulate water-absorbing agent is arranged with a gap substantially free of the particulate water-absorbing agent.
  • the water-absorbent resin particles swell, which weakens the fixation of the water-absorbent resin particles to the upper and lower sheets, and the water-absorbent resin particles may move in the sheet. Then, the water-absorbent resin particles are biased in the sheet, and the shape of the water-absorbent sheet is deformed. In this case, the liquid absorbency of the water-absorbent sheet becomes uneven, which causes leakage. In some cases, the water-absorbent resin particles may fall off from the inside of the sheet to the outside.
  • the elongation rate of the first base material is 10% or more and a region in which the particulate water-absorbing agent does not exist is provided in a part of the water-absorbing layer, the specific return Not only can the amount be effectively reduced, but the sheet shape is retained even after liquid absorption (the sheet has high shape retention).
  • FIG. 3 is a schematic view showing a cross section of the water-absorbent sheet 10 according to another embodiment of the present invention.
  • FIG. 3 shows three forms ((a) to (c)) of the water-absorbent sheet 10.
  • the arrows indicate the direction in which the absorbed liquid is introduced.
  • the first base material 11 is located on the side where the liquid absorbed by the water absorbing layer 12 (the liquid to be absorbed) is introduced. That is, the first base material 11 is arranged on the liquid discharge side (for example, the skin side in the case of paper diapers).
  • the water absorption layer 12 is arranged between the first base material 11 and the second base material 13.
  • the water absorbing layer 12 contains the particulate water absorbing agent 14.
  • the water absorbing layer 12 shows a state in which the particulate water absorbing agent 14 is present between the first base material 11 and the second base material 13. A part of the particulate water absorbing agent 14 may be detached from each of the base materials 11 and 13.
  • the particulate water-absorbing agent 14 (the region containing the particulate water-absorbing agent 14) is arranged with a gap 15 that does not substantially contain the particulate water-absorbing agent 14. Therefore, the water-absorbing "layer” does not mean only a continuum such as a sheet, but if it exists between the first base material 11 and the second base material 13 with a constant thickness and length.
  • the water absorption layer 12 may be intermittently present between the first base material 11 and the second base material 13 with a constant thickness and length.
  • an adhesive may be used.
  • the gap 15 is formed between the first base material 11 and the second base material 13, but the gap 15 in the present invention is shown in FIG. 3B. And the form of FIG. 3 (c) is also included.
  • the region containing the particulate water absorbing agent 14 is separated by the contact between the first base material 11 and the second base material 13. Although the first base material and the second base material are in contact with each other, it is regarded as a gap because the liquid passage is maintained. Further, since the water absorption layer 12 is separated by the first base material 11 (in some cases, the first base material 11 and the second base material 13) entering the water absorption layer 12, the water absorption layer 12 in the present embodiment. Exists intermittently. In FIG.
  • the end portion of the first base material 11 and the end portion of the second base material 13 are overlapped so that the end portion of the water-absorbent sheet 10 becomes the first base material 11 and the second base material 11. It is closed by the base material 13 of the above. Also in this case, the first base material 11 (in some cases, the first base material 11 and the second base material 13) enters at the end portion of the water absorption layer 12, so that the end portion of the water absorption layer 12 The water absorption layer 12 does not exist.
  • the particulate water absorbing agent 14 may be present in the first base material 11.
  • the particulate water absorbing agent 14 in the first base material 11 is, for example, in contact with the particulate water absorbing agent 14 that has come into contact with (or has been fixed to) the first base material 11 or the second base material 13.
  • the particulate water-absorbing agent 14 (or fixed) may be desorbed and captured in the first base material 11.
  • the content ratio of the particulate water absorbing agent 14 in the first base material 11 is the particle water absorbing agent 14 contained in the entire water absorbing sheet 10. On the other hand, it is preferably 5% or more, more preferably 10% or more, still more preferably 20% or more, and even more preferably 30% or more.
  • the upper limit is not particularly limited, but is 90% or less, 70% or less, and 50% or less in the preferred order.
  • the content ratio of the particulate water absorbing agent 14 in the first base material 11 to the particulate water absorbing agent 14 contained in the entire water absorbing sheet 10 is calculated by the method of Examples described later.
  • the region of the gap 15 does not substantially contain the particulate water absorbing agent 14.
  • Additives other than the particulate water absorbing agent 14 may be contained in the region of the gap 15.
  • the gap 15 may be formed by contacting the first base material 11 and the second base material 13 directly or via an adhesive. Since the first base material 11 has elasticity, the first base material 11 contains the particulate water absorbing agent 14 when there is a region on the second base material 13 containing the particulate water absorbing agent 14. It expands and contracts according to the area.
  • the first base material 11 has a shape that covers the region containing the particulate water absorbing agent 14 on the region containing the particulate water absorbing agent 14, and contains the particulate water absorbing agent 14 on the gap 15. After being along the upper side surface of the region, the shape is such that it sinks toward the second base material 13.
  • the particulate water-absorbing agent 14 is contained with respect to the thickness (La) from the liquid-absorbing surface of the first base material 11 to the surface of the second base material 13 on the water-absorbing layer 12 side in the gap 15.
  • the ratio (Lb / La) of the thickness (Lb) from the liquid absorbing surface of the first base material 11 to the surface of the second base material 13 on the water absorbing layer 12 side in the region is 1.05 or less. preferable.
  • the shape of the region containing the particulate water absorbing agent 14 (that is, the first base material) in the portion where the first base material 11 is in contact with the particulate water absorbing agent 14
  • the particle-like water-absorbing agent 14 in contact has a shape that follows (that is, the shape of the particle-like water-absorbing agent 14 on the side in contact with the first base material 11) (that is, expands and contracts accordingly). Therefore, the first base material 11 can be brought into close contact with the particulate water absorbing agent 14 (the region containing the particulate water absorbing agent 14), whereby the first base material 11 can be brought into close contact with the particulate water absorbing agent 14 (particulate).
  • Lb / La is usually 1 or more.
  • a gap 15 is formed by providing a non-existent region of the particulate water-absorbing agent 14 on a part of the second base material 13.
  • the gap 15 (that is, the non-existent region of the particulate water absorbing agent 14) is continuously provided along one direction on the liquid absorbing surface of the first base material 11, so that the function as a liquid passing path is further enhanced.
  • the shape in which the gaps 15 are continuously provided may be, for example, linear, curved, or corrugated, but it is preferable that the gaps 15 are linearly provided in parallel.
  • the region and the gap 15 containing the particulate water-absorbing agent 14 are in one direction on the liquid-absorbing surface of the first base material 11 (the plane direction perpendicular to the direction in which the liquid is absorbed). It is preferable that it has a shape extending along the above and is arranged in parallel. That is, the regions containing the particulate water absorbing agent 14 are arranged in a streak (striped) pattern. As a result, the gaps 15 are also formed in stripes, so that the gaps 15 can be easily maintained even when the particulate water absorbing agent 14 swells, and as a result, reversion can be further reduced.
  • the "one direction” is any direction parallel to the surface direction on the liquid absorbing surface of the first base material 11, excluding the thickness direction, that is, on the liquid absorbing surface of the first base material 11. It may be in the longitudinal direction, the lateral direction, or the direction inclined with respect to these directions. From the viewpoint of the balance between the role of the gap 15 and the role of the particulate water absorbing agent 14, in the water absorbing sheet 10, the region containing the particulate water absorbing agent 14 and the gap 15 are the liquid absorbing surfaces of the first base material 11. It is preferable that the particles have a shape extending along the longitudinal direction and are arranged in parallel.
  • the ratio of the region containing the particulate water absorbing agent 14 is preferably 90% or less in terms of area. , 80% or less, and even more preferably 75% or less. Further, the ratio of the region containing the particulate water absorbing agent 14 on the surface of the first base material 11 on the water absorbing layer 12 side is preferably 10% or more, more preferably 20% or more in terms of area.
  • the ratio of the region containing the particulate water absorbing agent 14 on the surface of the first base material 11 on the water absorbing layer 12 side is the surface of the second base material 13 on the water absorbing layer 12 side (the particulate water absorbing agent 14 is arranged). It is the same as the ratio of the region containing the particulate water absorbing agent 14 on the surface).
  • the water-absorbent sheet 10 has a wrapping sheet 16.
  • the wrapping sheet 16 is a first base material for the purpose of maintaining the shape of the water absorbing sheet 10, which is a structure in which the particulate water absorbing agent 14 is supported between the first base material 11 and the second base material 13.
  • the particulate water absorbing agent 14 is the first.
  • the purpose is to prevent the particulate water absorbent 14 from coming into direct contact with the skin when it permeates through the base material 11 and migrates to the outer surface (the surface with which the liquid comes into direct contact) of the first base material 11.
  • the wrapping sheet 16 When the wrapping sheet 16 is not provided, for example, by a method of sealing by adhering the base materials 11 and 13 to each other, and by surface treatment of the first base material 11, the outer surface of the first base material 11 is formed. There is a method of suppressing the transition to. It is preferable to have the wrapping sheet 16 as a method of preventing the particulate water absorbing agent 14 from falling off from the water absorbing sheet 10 while maintaining the effect of the present application. The configuration of the wrapping sheet 16 is omitted because it has been described with reference to FIGS. 1 and 2.
  • the water-absorbent sheet 10 of the present invention has at least a wrapping sheet 16 to be arranged on the surface of the first base material 11 (that is, on the liquid-absorbing surface of the first base material 11).
  • the first base material 11 forms a water absorbing surface that directly absorbs the liquid.
  • the water-absorbent sheet having the wrapping sheet 16 if the wrapping sheet 16 forms a liquid-absorbing surface that directly absorbs the liquid, it can be paraphrased as follows; A water-absorbent sheet having a base material, a water-absorbent layer located between the first base material and the second base material, and a wrapping sheet arranged on the surface of the first base material.
  • the water-absorbing layer contains the particulate water-absorbing agent, and the region containing the particulate water-absorbing agent is arranged with a gap substantially free of the particulate water-absorbing agent so that the surface of the wrapping sheet is formed.
  • a liquid absorption surface that directly absorbs the liquid is formed, and the ratio of the thickness of the first base material to the thickness of the second base material (thickness of the first base material (mm) / second The thickness (mm) of the base material is 1.5 or more and less than 14, and the first base material has an elongation rate of 10% or more.
  • the first base material 11 and the particulate water-absorbing agent 14 in the water-absorbing layer 12 are preferably in contact with each other directly or via an adhesive, and / or the second base material. It is preferable that 13 and the particulate water absorbing agent 14 in the water absorbing layer 12 are in contact with each other directly or via an adhesive.
  • the water-absorbent sheet of the present invention is substantially a particulate water-absorbing agent sandwiched between a first base material, a second base material, and a first base material and a second base material.
  • More preferred embodiments include a first substrate; a second substrate; a first substrate, a particulate water absorbent sandwiched between the second substrates; a particulate water absorbent and a second substrate. It has a simple structure consisting only of an adhesive that adheres a particulate water-absorbing agent to the base material to the second base material; and a wrapping sheet that wraps all of them. That is, although the water-absorbent sheet of the present invention has a simple structure, the specific return amount can be effectively reduced.
  • the elongation rate of the first base material is 10% or more, preferably 15% or more, more preferably 17% or more, still more preferably 20% or more, still more preferably. It is 22% or more.
  • the upper limit of the elongation rate of the first base material is not particularly limited, but is preferably 60% or less. When the elongation rate of the first base material is within such a range, the first base material can easily follow the shape of the particulate water absorbing agent, and as a result, the shape retention of the water absorbing sheet is further enhanced, and the water absorbing sheet reverts. The amount can be further reduced.
  • the elongation rate of the first base material a value measured by the method described in Examples described later is adopted.
  • the "elongation rate of the non-woven fabric (first base material)" is a numerical value when the elongation rate is measured in the direction of maximum elongation. Further, the elongation rate of the first base material can be controlled by the bulk density, the basis weight, the material, the mesh structure, the manufacturing process conditions, and the like.
  • the extending direction of the first base material is not particularly limited as long as it extends in any one direction parallel to the surface direction of the first base material, excluding the thickness direction.
  • any one direction from any angle direction such as the long side direction, the short side direction, and the diagonal direction of the sheet plane may be stretched at the elongation rate in the above range.
  • it is a substrate that can extend from all directions (isotropic).
  • the surface of the first base material 11 may be brushed in order to further impart liquid permeability, diffusibility, flexibility, etc. to the water-absorbent sheet 10. That is, in one embodiment of the present invention, the first base material 11 is a surface opposite to the liquid absorbing surface that directly absorbs the liquid, that is, a surface provided with the water absorbing layer 12 (on the water absorbing layer 12 side). The surface) is brushed.
  • the term "raised" means a state in which the fibers on the surface are fluffed.
  • the water-absorbent sheet of the present invention when the surface of the first base material on the water-absorbent layer side is brushed, not only the specific return amount can be effectively reduced, but also the water-absorbent sheet once absorbs the liquid. After that, it is possible to effectively prevent the particulate water-absorbing agent from falling off from the water-absorbing sheet.
  • FIG. 4 shows a water-absorbent sheet having a first base material 11 whose surface on the water-absorbent layer 12 side is raised.
  • the first base material 11 fibers are raised toward the water absorption layer 12 on the surface on the water absorption layer 12 side.
  • a part of the raised fibers of the first base material 11 exceeds the particulate water absorbing agent 14 and comes into contact with and adheres to the second base material 13 to which the adhesive is applied.
  • the particulate water absorbing agent 14 absorbs water and swells, the first base material 11 and the second base material 13 continue to adhere to each other via the raised fibers of the first base material 11. This makes it possible to retain the particulate water absorbing agent 14 between the first base material 11 and the second base material 13. Therefore, by adhering the first base material 11 and the second base material 13, the particulate water absorbing agent 14 is retained even after the water absorbing sheet 10 absorbs water, and the gel dropout rate can be reduced.
  • the surface of the first base material 11 on the water absorption layer 12 side is brushed, and the first base material does not support the particulate water absorption agent 14 by the adhesive. That is, the first base material 11 and the particulate water absorbing agent 14 in the water absorbing layer 12 are in direct contact with each other. In this case, the particulate water absorbing agent 14 is fixed to the second base material 13 by an adhesive. Therefore, in one embodiment, it is preferable that the first base material 11 and the particulate water absorbing agent 14 in the water absorbing layer 12 are in direct contact with each other, and the second base material 13 and the particulate water absorbing agent in the water absorbing layer 12 are in direct contact with each other. It is preferable that the agent 14 is in contact with the agent 14 via an adhesive.
  • the surface of the first base material 11 on the water absorbing layer 12 side is brushed and the first base material does not support the particulate water absorbing agent 14 by the adhesive is unknown in detail, but in Examples.
  • the effect is proved by the specific amount of return. That is, the first base material 11 has a form in which no adhesive is applied to the raised surface of the water absorbing layer 12 side of the first base material 11 and the first base material does not support the particulate water absorbing agent 14 by the adhesive.
  • the specific return amount is smaller than in the form in which the adhesive is applied to the brushed surface of the base material 11 on the water absorbing layer 12 side and the first base material carries the particulate water absorbing agent 14 by the adhesive. ..
  • the adhesive applied to the surface of the second base material 13 on the water absorption layer 12 side is preferably a hot melt adhesive. Since the adhesive is a hot melt adhesive, the brushed fibers of the first base material 11 and the second base material 13 adhere well to each other, and even after the water-absorbent sheet 10 absorbs water, the first base material The 11 and the second base material 13 continue to adhere to each other, and the particulate water absorbing agent 14 between the first base material 11 and the second base material 13 is retained.
  • the water-absorbent sheet 10 has a wrapping sheet 16.
  • the wrapping sheet 16 is not an essential configuration in the water-absorbent sheet 10 according to the present invention
  • the water-absorbent sheet 10 includes a first base material 11 having a brushed surface on the water-absorbent layer 12 side and a wrapping sheet 16. By doing so, it is possible to effectively suppress the particulate water absorbing agent 14 from falling off from the water absorbing sheet 10.
  • the configuration of the wrapping sheet 16 will be omitted because it has been described above.
  • the water-absorbent sheet 10 of the present invention has at least a wrapping sheet 16 to be arranged on the surface of the first base material 11 (that is, on the liquid-absorbing surface of the first base material 11).
  • the first base material 11 forms a water absorbing surface that directly absorbs the liquid.
  • the water-absorbent sheet having the wrapping sheet 16 if the wrapping sheet 16 forms a liquid-absorbing surface that directly absorbs the liquid, it can be paraphrased as follows; A water-absorbent sheet having a base material, a water-absorbent layer located between the first base material and the second base material, and a wrapping sheet arranged on the surface of the first base material.
  • the water-absorbing layer contains a particulate water-absorbing agent, and the surface of the wrapping sheet forms a liquid-absorbing surface that directly absorbs the liquid, and the first one with respect to the thickness of the second base material.
  • the ratio of the thickness of the base material is 1.5 or more and less than 14, and the first base material 11 is a water absorption layer.
  • the surface provided with 12 (the surface on the water absorption layer 12 side) is brushed.
  • the first base material 11 and the particulate water-absorbing agent 14 in the water-absorbing layer 12 are preferably in direct contact with each other or via an adhesive, and more preferably in direct contact with each other.
  • the second base material 13 and the particulate water absorbing agent 14 in the water absorbing layer 12 are preferably in contact with each other directly or via an adhesive, and more preferably through an adhesive.
  • the water-absorbent sheet of the present invention is substantially a particulate water-absorbing agent sandwiched between a first base material, a second base material, and a first base material and a second base material.
  • More preferred embodiments include a first substrate; a second substrate; a first substrate, a particulate water absorbent sandwiched between the second substrates; a particulate water absorbent and a second substrate. It has a simple structure consisting only of an adhesive that adheres a particulate water-absorbing agent to the base material to the second base material; and a wrapping sheet that wraps all of them. That is, although the water-absorbent sheet of the present invention has a simple structure, the specific return amount can be effectively reduced.
  • the content of the particulate water absorbing agent 14 contained in the sex sheet 10 can be 200 g / m 2. Therefore, in the water-absorbent sheet 10 having the first base material 11 whose surface on the water-absorbent layer 12 side is raised, the content of the particulate water-absorbent agent 14 contained in the water-absorbent sheet 10 is preferably 200 g / m.
  • the upper limit of the content of the particulate water absorbing agent 14 contained in the water absorbing sheet 10 is not particularly limited, but from the viewpoint of retaining the water absorbing agent 14, it is preferably 360 g / m 2 or less, more preferably 350 g /. It is m 2 or less, more preferably 325 g / m 2 or less.
  • the content of the adhesive sprayed on the second base material 13 is preferably 1 to 50 g / g.
  • m 2 more preferably 5 to 50 g / m 2 , even more preferably 10 to 45 g / m 2 , particularly preferably 15 to 30 g / m 2 , and most preferably 15 to 25 g / m. It is 2.
  • the mass ratio of the particulate water absorbent to the adhesive is preferably 80:20 to 99: 1, more preferably 85:15 to 98: 2, and even more preferably 90:10 to 90:10. It is 98: 2, particularly preferably 91: 9 to 97: 3, and most preferably 92: 8 to 96: 4. Since the surface of the first base material on the water absorption layer side is raised, the raised fibers of the first base material are entangled with the particulate water absorbing agent, and the particulate water absorbing agent is held by the first base material. Therefore, the amount of the adhesive to the particulate water absorbent can be reduced. As a result, the effect of reducing the specific return amount is further exhibited.
  • the brushed area ratio in the brushed area measurement test of the brushed surface is preferably 5% or more.
  • the raised area ratio of the raised surface of the first base material is preferably 5% or more, 7% or more, and 10% or more in that order.
  • the upper limit of the raised area ratio of the raised surface of the first base material is not particularly limited, but is preferably 30% or less, more preferably 28% or less, still more preferably, from the viewpoint of controlling the swelling of the particulate water absorbing agent. Is 25% or less.
  • the raised area ratio in the raised area measurement test is calculated by the method described in Examples described later.
  • the dropout of the agent can be effectively suppressed.
  • the dropout rate of the particulate water absorbing agent calculated in the examples of the present invention is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less. preferable. Such an effect is effectively exhibited by raising the surface of the first base material on the water absorption layer side.
  • the first base material is a water-permeable sheet located on the side where the liquid to be absorbed is introduced.
  • the liquid to be absorbed is not limited to water, but urine, blood, sweat, feces, waste liquid, moisture, vapor, ice, a mixture of water and an organic solvent and / or an inorganic solvent, rainwater, groundwater, etc. However, it is not particularly limited as long as it contains water.
  • urine, menstrual blood, sweat and other body fluids can be mentioned.
  • the water permeability of the water-permeable sheet preferably has a water permeability coefficient (JIS A1218: 2009) of 1 ⁇ 10-5 cm / sec or more.
  • the hydraulic conductivity is more preferably 1 ⁇ 10 -4 cm / sec or more, even more preferably 1 ⁇ 10 -3 cm / sec or more, particularly preferably 1 ⁇ 10 ⁇ 2 cm / sec or more, and most preferably 1 ⁇ It is 10 -1 cm / sec or more.
  • the hydraulic conductivity of the first substrate used in the examples of the present application was 1 ⁇ 10-5 cm / sec or more.
  • the first substrate has a bulk density is preferably at 0.1 g / cm 3 or less, more preferably at 0.08 g / cm 3 or less, is 0.05 g / cm 3 or less Is even more preferable.
  • the bulk density of the first substrate preferably being 0.001 g / cm 3 or more, more preferably 0.005 g / cm 3 or more, further preferably 0.01 g / cm 3 or more.
  • the bulk density is the mass with respect to the unit volume, and is not the density when the base material is compressed under high pressure (when the voids are eliminated), but the density obtained from the volume of the base material including the volume of the voids. Is.
  • the bulk density of the first base material is 0.1 g / cm 3 or less, it means that the first base material is light. Bulky means low bulk density and significantly thicker.
  • the absorbed liquid in contact with the liquid absorption surface of the first base material quickly flows into the lower water absorption layer and the second base material. The amount of liquid remaining on the liquid absorbing surface of the first base material can be reduced. Further, when the absorbed liquid reaches the water absorption layer, the liquid is diffused in the surface direction. Therefore, even if a large amount of the liquid is introduced into the water absorption layer, the water absorption layer spreads in the surface direction instead of locally. It will absorb the liquid.
  • the bulky first base material has low water absorption, high liquid permeability, and high liquid diffusivity. As a result, the amount of reversion in the water-absorbent sheet can be reduced. The humidity of the liquid absorbing surface of the first base material can be suppressed, and the discomfort to the skin can be reduced.
  • the bulk density of the first base material is preferably 0.1 g / cm 3 or less. In this specification, the bulk density is a value calculated in Examples described later.
  • the first base material preferably has a basis weight of 3 to 80 g / m 2 , more preferably 5 to 70 g / m 2 , and even more preferably 10 to 60 g / m 2. ..
  • the basis weight of the first base material is within such a range, the amount of reversion can be further reduced, and the particulate water absorbing agent can be easily taken into the first base material, and as a result, the water absorbing sheet is retained. The shape is further enhanced.
  • the thickness of the first substrate is, for example, 40% RH to 50% RH, preferably 0.7 mm or more, more preferably 1.0 mm or more, still more preferably 1.2 mm or more, and particularly preferably 1.3 mm or more. , Most preferably 1.4 mm or more.
  • the upper limit of the thickness of the first base material is, for example, 40% RH to 50% RH, preferably 5 mm or less, more preferably 4 mm or less, still more preferably 3 mm or less, and particularly preferably 2.5 mm or less. It is preferably 2 mm or less.
  • the thickness of the first base material is within such a range, a sufficient distance between the liquid absorbing surface of the first base material and the water absorbing layer and the second base material can be sufficiently secured, and once the water absorbing layer and the second base material are used. It is possible to significantly reduce the reversion of the liquid that has reached the base material of No. 2 and reduce the leakage in the plane direction.
  • the thickness, bulk density, and basis weight of the first base material can be controlled by the material constituting the first base material, the manufacturing method of the first base material, and the like. The thickness and bulk density are determined.
  • the first base material has a particulate water absorbing agent transmittance (permeability of the particulate water absorbing agent with respect to the first base material) of preferably 40% by mass or more, more preferably 50% by mass or more. More preferably, it is 60% by mass or more, 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more, in the order of preference.
  • the upper limit of the transmittance is not particularly limited, but is preferably 97% by mass or less. Since the transmittance of the particulate water-absorbing agent with respect to the first base material is within such a range, the particulate water-absorbing agent easily enters the first base material on the side in contact with the water-absorbing layer of the first base material. Become.
  • the water-absorbing agent in the form of particles can absorb the water contained in the first base material, and the reversion is further reduced.
  • the transmittance of the particulate water-absorbing agent with respect to the first base material is the ratio of the particulate water-absorbing agent that permeates the first base material, and the granular water absorption existing on the first base material. A value determined by the weight of the particulate water-absorbing agent that has passed through the first substrate when the agent is shaken under predetermined conditions described later, and specifically, a value calculated by the method described in Examples described later. Is.
  • the transmittance of the first base material is determined by the properties of the members constituting the first base material, the surface state thereof, the complexity of the network structure, the fiber diameter, and the fibers when the first base material is a non-woven fabric. It can be adjusted to a desired range by appropriately adjusting the fused state, basis weight, thickness, etc. between them. For example, if an air-through non-woven fabric is used as the first base material as described later, the transmittance can be adjusted by changing the heat treatment conditions, fiber diameter and density of the air-through non-woven fabric.
  • the surface of the first base material on the water absorption layer side is brushed.
  • the material constituting the first base material examples include paper (sanitary paper, for example, tissue paper, toilet paper and towel paper), net, non-woven fabric, woven cloth, film and the like. Above all, from the viewpoint of water permeability, a non-woven fabric is preferably used as at least the first base material.
  • the non-woven fabric used is not particularly limited, but from the viewpoint of liquid permeability, flexibility and strength when made into a water-absorbent sheet, polyolefin fibers such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), and the like.
  • Non-woven fabrics made of polyester fibers such as polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN), polyamide fibers such as nylon, rayon fibers, and other synthetic fibers, cotton, silk, linen, pulp (cellulose) fibers, etc. Examples thereof include non-woven fabrics produced by mixing.
  • rayon fiber, polyolefin fiber, polyester fiber, pulp fiber and a fiber in which these are mixed are preferable, and polyolefin fiber is more preferable.
  • These fibers may be hydrophilized.
  • the non-woven fabric that can be used as the first base material is not particularly limited, and may be obtained by any method such as an air-through method; an air-laid method; a spunbond method; a spunlace method. Is preferably obtained by the air-through method or the air-laid method, and is preferably obtained by the air-through method (air-through non-woven fabric).
  • the air-laid method is a method in which air is placed on an air flow to uniformly disperse it and then absorbed onto a wire mesh to form a non-woven fabric. Since air is used to disperse pulp fibers, the volume is increased and the density is reduced. can do. Since the first base material is an air-through non-woven fabric, the absorbed liquid is likely to be quickly introduced into the first base material after coming into contact with the liquid absorbing surface of the first base material. That is, by using the air-through non-woven fabric as the first base material, it is possible to use the first base material having low water absorption and high liquid permeability, and the amount of reversion in the water absorption sheet can be significantly reduced. ..
  • the second base material is a water-permeable sheet and is located on the opposite side to the side where the liquid is absorbed, the performance of the water-absorbent sheet (return amount, leakage in the plane direction, etc.), which is the effect of the present invention, is achieved. Can be fully demonstrated.
  • the water permeability of the water-permeable sheet preferably has a water permeability coefficient (JIS A1218: 2009) of 1 ⁇ 10-5 cm / sec or more.
  • the hydraulic conductivity is more preferably 1 ⁇ 10 -4 cm / sec or more, even more preferably 1 ⁇ 10 -3 cm / sec or more, particularly preferably 1 ⁇ 10 ⁇ 2 cm / sec or more, and most preferably 1 ⁇ It is 10 -1 cm / sec or more.
  • the thickness of the second substrate is, for example, 40% RH to 50% RH, preferably 0.05 mm or more, more preferably 0.08 mm or more, still more preferably 0.1 mm or more, and particularly preferably 0. It is 2 mm or more, most preferably 0.3 mm or more.
  • the thickness of the second substrate is, for example, 40% RH to 50% RH, preferably 0.9 mm or less, more preferably 0.8 mm or less, still more preferably 0.7 mm or less, and particularly preferably 0.6 mm or less. Most preferably, it is 0.5 mm or less.
  • the thickness of the first base material is 0.7 mm or more and 5 mm or less
  • the thickness of the second base material is 0.05 mm or more and 0.9 mm or less.
  • the thickness of the first base material is preferably 1.0 mm or more and 4 mm or less
  • the thickness of the second base material is 0.08 mm or more and 0.8 mm or less.
  • the thickness of the first base material is 1.2 mm or more and 3 mm or less
  • the thickness of the second base material is 0.1 mm or more and 0.7 mm or less, and even more preferably the thickness of the first base material.
  • the thickness is 1.3 mm or more and 2.5 mm or less
  • the thickness of the second base material is 0.2 mm or more and 0.6 mm or less, and particularly preferably the thickness of the first base material is 1.4 mm or more and 2 mm or less.
  • the thickness of the second base material is 0.3 mm or more and 0.5 mm or less.
  • the bulk density of the second substrate is preferably at 1 g / cm 3 or less, more preferably at 0.5 g / cm 3 or less, that is 0.3 g / cm 3 or less More preferred.
  • the bulk density of the second substrate is preferably 0.05 g / cm 3 or more, more preferably 0.07 g / cm 3 or more, further preferably 0.08 g / cm 3 or more.
  • the second base material preferably has a basis weight of 5 to 100 g / m 2 , more preferably 10 to 70 g / m 2 , and further preferably 15 to 65 g / m 2. Preferred.
  • the thickness, bulk density, and basis weight of the second base material can be controlled by the material constituting the second base material, the manufacturing method of the second base material, and the like. The thickness and bulk density are determined.
  • the porosity of the first base material, the second base material and the wrapping sheet can be measured by the following formula.
  • Poleolefin) density C (g / cm 3 ) Porosity (%) of the base material (or sheet) 100- ⁇ (A / 10000) / (B / 10) ⁇ / C * 100
  • the second substrate is preferably a liquid distribution area is 1000 mm 2 or more, more preferably 3000 mm 2 or more, more preferably at 6000 mm 2 or more, and particularly preferably 7000 mm 2 or more.
  • the upper limit of the liquid diffusion area of the second base material is not particularly limited, but is preferably 10,000 mm 2 or less, for example.
  • the liquid diffusion area of the second base material is within the above range, when the absorbed liquid reaches the second base material, the liquid can be sufficiently diffused in the plane direction on the second base material.
  • the second base material absorbs the liquid while spreading in the plane direction instead of locally. Therefore, the liquid can be sufficiently absorbed and retained in the second base material, the amount of reversion in the water-absorbent sheet can be significantly reduced, and the leakage in the plane direction can be significantly reduced.
  • the liquid diffusion area diffuses when the liquid comes into contact with a base material (for example, a non-woven fabric) and / or when the liquid passes through the base material in a direction perpendicular to the surface direction of the base material. It means the area in the plane direction, and is a value calculated by the method described in Examples described later. The larger the liquid diffusion area of the base material, the higher the liquid diffusibility of the base material in the plane direction.
  • a non-woven fabric is preferably used as the material constituting the second base material.
  • the same material as that of the first base material can be applied, and for example, rayon fiber, polyolefin fiber, polyester fiber, pulp fiber and fiber in which these are mixed are preferable, and the non-woven fabric is more preferable. preferable.
  • the non-woven fabric that can be used as the second base material is not particularly limited, and may be obtained by any method such as an air-through method; an air-laid method; a spunbond method; a spunlace method. However, it is preferable that the material is obtained by the air-laid method (air-laid non-woven fabric) or the spun-lace method (spun-laced non-woven fabric).
  • the spunlace method is a method in which fibers are entangled with a high-pressure water stream and does not use an adhesive.
  • the water-absorbing layer in the water-absorbing sheet according to the embodiment of the present invention has a particulate water-absorbing agent.
  • the water absorption layer contains a particulate water absorption agent.
  • the water absorbing agent is a mixture of a plurality of types of particulate water absorbing agents
  • the following description is a description of the physical properties of the mixture. That is, the physical characteristics of the particulate water-absorbing agent are the physical characteristics when all the particulate water-absorbing agents contained in the water-absorbing layer are mixed. Further, the physical characteristics of the particulate water-absorbing agent may be measured by taking out only the particulate water-absorbing agent from the water-absorbent sheet so that cotton-like pulp or the like is not mixed.
  • surface tension is the work (free energy) required to increase the surface area of a solid or liquid, expressed per unit area.
  • the surface tension referred to in the present application refers to the surface tension of the aqueous solution when the particulate water absorbent is dispersed in the 0.90 mass% sodium chloride aqueous solution.
  • the surface tension of the water absorbing agent is measured by the following procedure. That is, 50 ml of physiological saline adjusted to 20 ° C. was placed in a thoroughly washed 100 ml beaker, and the surface tension of the physiological saline was first measured using a surface tension meter (K11 automatic surface tension meter manufactured by KRUSS). To measure.
  • a fully washed 25 mm long fluororesin rotor and 0.5 g of a particulate water absorbent were placed in a beaker containing a physiological saline solution adjusted to 20 ° C. after measuring the surface tension, at 500 rpm. Stir for 4 minutes under the conditions. After 4 minutes, the stirring is stopped, and after the water-containing particulate water absorbent has settled, the surface tension of the supernatant is measured again by performing the same operation.
  • a plate method using a platinum plate is adopted, and the plate is sufficiently washed with deionized water before each measurement and heated and washed with a gas burner before use.
  • the surface tension of the particulate water-absorbing agent is 60 mN / m or more, 65 mN / m or more, 66 mN / m or more, 67 mN / m or more, 69 mN / m or more, in the following order. It is preferably 70 mN / m or more, 71 mN / m or more, and most preferably 72 mN / m or more.
  • the effect of surface tension is more likely to appear than with conventional paper diapers, and when the surface tension satisfies the above conditions, the amount of reversion in the water-absorbent sheet can be reduced. Moreover, leakage in the surface direction can be reduced.
  • the upper limit of the surface tension of the particulate water-absorbent is not particularly limited, but is actually 73 mN / m or less.
  • the CRC (water absorption ratio under no pressure) of the particulate water-absorbing agent is 30 g / g or more, 32 g / g or more, 33 g / g or more, 34 g / g or more in the following order. Is preferable, and most preferably 35 g / g or more.
  • the CRC of the particulate water absorbing agent is an abbreviation for Centrifuge Retention Capacity (centrifuge holding capacity) defined by ERT441.2-02, and the water absorption ratio of the particulate water absorbing agent under no pressure (“water absorption ratio””. It may also be called). Specifically, 0.2 g of the particulate water absorbent is placed in a non-woven fabric bag, and then immersed in a large excess of 0.9 mass% sodium chloride aqueous solution for 30 minutes for free swelling, and then a centrifuge (centrifuge). It refers to the water absorption ratio (unit: g / g) after draining with 250G).
  • the AAP (water absorption ratio under pressure) of the particulate water-absorbing agent is preferably 25 g in the following order from the viewpoint of improving the performance of the water-absorbing sheet (reducing the amount of return). / G or more, more preferably 28 g / g or more, particularly preferably 30 g / g or more, and most preferably 33 g / g or more.
  • the AAP of the particulate water-absorbing agent is an abbreviation for Absorption against Pressure defined by ERT442.2.20, and means the water absorption ratio under pressure of the particulate water-absorbing agent.
  • 0.9 g of the particulate water absorbent was swollen with a large excess of 0.9 mass% sodium chloride aqueous solution for 1 hour under a load of 2.06 kPa (21 g / cm 2 , 0.3 psi). It refers to the subsequent water absorption ratio (unit: g / g). Further, in ERT442.2-02, although it is described as Absorption Under Pressure (AUP), it has substantially the same contents.
  • AUP Absorption Under Pressure
  • the DRC 5 min (immersion holding capacity 5 minutes value) of the particulate water-absorbing agent is in the following order from the viewpoint of improving the performance of the water-absorbent sheet (reducing the specific return amount). It is preferably 25 to 50 g / g, more preferably 30 to 45 g / g, and particularly preferably 30 to 40 g / g.
  • the DRC5min of the particulate water-absorbing agent means the water absorption ratio under no pressurization for 5 minutes, and the larger the value of DRC5min, the faster the absorption rate.
  • the GPR of the particulate water-absorbing agent is preferably 20 g / min because it is excellent in shortening the water absorption time in the evaluation of the specific pressure return amount described later, that is, improving the water absorption rate.
  • the above is more preferably 50 g / min or more, still more preferably 70 or more, still more preferably 100 g / min or more, and particularly preferably 150 / min or more. That is, when the GPR of the particulate water absorbing agent is 20 g / min or more, the water absorption time can be shortened in the pressure specific return amount evaluation, and thus the water absorption rate is improved. Thereby, the discomfort of the user can be reduced.
  • the GPR of the particulate water absorbent is preferably 1000 g / min or less.
  • the GPR of the particulate water-absorbing agent is an abbreviation for Gel Permeation Rate (gel permeation rate), and the flow velocity of the liquid passing between the particles of the swelling gel when the particulate water-absorbing agent is swollen under a load (Gel Permeation Rate). Unit: g / min).
  • the particle-like water-absorbent is not limited in its particle shape, and may be, for example, a spherical particle-like water-absorbent (and its granulated product).
  • the particulate water absorbent is preferably in the form of amorphous crushed material.
  • the amorphous crushed particles are crushed particles having a non-constant shape. This is because the amorphous crushed particles can be easily fixed to the substrate as compared with the spherical particles obtained by reverse phase suspension polymerization or vapor phase polymerization.
  • the particulate water absorbent according to one embodiment of the present invention is preferably a pulverized product in aqueous solution polymerization.
  • spherical particles or granulated products of spherical particles obtained by reverse phase suspension polymerization or droplet polymerization such as spraying and polymerizing a polymerization monomer are typically crushed into an indefinite form. Not in shape.
  • the shape of the particulate water absorbing agent is amorphous and crushed, the shape of the water absorbing sheet is more likely to be maintained as compared with the one having a high average roundness (for example, a spherical one).
  • the average roundness of the particulate water absorbent is preferably 0.70 or less, more preferably 0.60 or less, and further preferably 0.55 or less.
  • the calculation method of the average roundness is as follows. 100 or more particulate water absorbents are randomly selected, and each particulate water absorbent is photographed with an electron microscope (VE-9800 manufactured by Keyence Co., Ltd.) (magnification 50 times) to obtain an image of the particulate water absorbent. , The peripheral length and area were calculated for each particle using the attached image analysis software. The following formula:
  • the roundness of each particle is obtained with, and the average value of the obtained values is calculated as the average roundness.
  • particle size The particle size of the particulate water-absorbing agent (or particulate water-absorbent resin, water-absorbent resin particles) according to the embodiment of the present invention is obtained according to the measurement method of "PSD" specified in ERT420.2-02.
  • PSD the measurement method of "PSD” specified in ERT420.2-02.
  • the weight average particle size is 150 to 600 ⁇ m.
  • the method for producing the particulate water-absorbing agent is not particularly limited as long as it is a method for producing the water-absorbing agent having desired physical properties, and for example, it can be appropriately produced in consideration of the publications described in the examples.
  • the water-absorbent sheet it is preferable to have at least a wrapping sheet to be arranged on the surface of the first base material.
  • the wrapping sheet may be arranged on the surface of the first base material, but it is more preferable that the wrapping sheet is arranged so as to cover the side surface of the first base material and the side surface of the water absorption layer. A part of the side surface of the first base material, the side surface of the water absorption layer, and the side surface of the second base material, which are opposite to the side on which the liquid to be absorbed of the second base material is introduced. Or it is more preferable to cover the whole.
  • the water-absorbent sheet includes a wrapping sheet, and the wrapping sheet is a water-permeable sheet and is located at least on the surface (the side to be absorbed) of the first base material. ..
  • the thickness of the wrapping sheet is, for example, 40% RH to 50% RH, preferably 0.001 mm or more, more preferably 0.005 mm or more, still more preferably 0.01 mm or more, and particularly preferably 0.1 mm or more. Most preferably, it is 0.2 mm or more.
  • the thickness of the wrapping sheet is, for example, 40% RH to 50% RH, preferably less than 0.9 mm, more preferably 0.8 mm or less, still more preferably 0.7 mm or less, particularly preferably 0.6 mm or less, most preferably. Is 0.5 mm or less.
  • the bulk density of the wrapping sheet is preferably at 1 g / cm 3 or less, more preferably at 0.5 g / cm 3 or less, even more preferably at 0.3 g / cm 3 or less.
  • the bulk density of the wrapping sheet is preferably 0.1 g / cm 3 or more, more preferably 0.12 g / cm 3 or more, further preferably 0.13 g / cm 3 or more.
  • the basis weight of the wrapping sheet is preferably 5 to 100 g / m 2 , more preferably 5 to 70 g / m 2 , and even more preferably 10 to 65 g / m 2 .
  • the thickness, bulk density, and basis weight of the wrapping sheet can be controlled by the material constituting the wrapping sheet, the manufacturing method of the wrapping sheet, etc., and the thickness and bulk density of the wrapping sheet are determined by these balances.
  • the material constituting the wrapping sheet is not particularly limited as long as the above-mentioned purpose of providing the wrapping sheet can be achieved, and for example, paper (sanitary paper such as tissue paper, toilet paper and towel paper), net, non-woven fabric, woven cloth. , Film and the like.
  • the non-woven fabric used is not particularly limited, but from the viewpoint of liquid permeability, flexibility and strength when made into a water-absorbent sheet, polyolefin fibers such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), and the like.
  • Non-woven fabrics made of polyester fibers such as polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN), polyamide fibers such as nylon, rayon fibers, and other synthetic fibers, cotton, silk, linen, pulp (cellulose) fibers, etc. Examples thereof include non-woven fabrics produced by mixing.
  • rayon fiber, polyolefin fiber, polyester fiber, pulp fiber and a fiber in which these are mixed are preferable, and polyolefin fiber is more preferable.
  • These fibers may be hydrophilized.
  • the non-woven fabric that can be used as the wrapping sheet is not particularly limited, and may be obtained by any method such as an air-through method; an air-laid method; a spunbond method; a spunlace method, but the spunbond method. It is preferable that it is the one obtained in (Spunbonded non-woven fabric).
  • the urine water absorbed by the water-absorbent sheet is absorbed even when the water-absorbent sheet is loaded (even when it is pressurized), such as when an infant wearing an absorbent item such as a disposable diaper is sitting.
  • a wrapping sheet having water repellency so as not to ooze out from the sheet is preferable, and for example, a spunbonded non-woven fabric is preferable.
  • the method for producing a spunbonded non-woven fabric is a method of directly accumulating long continuous fibers obtained by melting and spinning a raw material resin to form a fleece. Examples of the raw material resin include polyethylene, polypropylene, polylactic acid and the like.
  • the method for producing the first base material, the method for producing the second base material, and the method for producing the wrapping sheet are different.
  • the first base material is an air-through non-woven fabric
  • the second base material is an air-laid non-woven fabric and a spunlace non-woven fabric
  • the wrapping sheet is a spunbond non-woven fabric, which are different non-woven fabrics. Is. With such a form, the desired effect of the present invention can be efficiently achieved.
  • the method for producing a water-absorbent sheet according to an embodiment of the present invention includes (1) a step of spraying a particulate water-absorbing agent on a first base material, and (2) a particle-like water-absorbing agent on a second base material. Includes at least one of the spraying steps.
  • the following manufacturing methods (a) to (d) can be mentioned.
  • one side of the first base material may be raised before the manufacturing methods (a) to (d).
  • the method of raising the surface of the first base material on the water absorption side is not particularly limited, and a known method can be used, for example, a method using a needle, a thistle fruit (teasel), or a brush (brush). Can be mentioned. Industrially, it is possible to raise the first substrate by rotating a roller wrapped with needle cloth or thistle fruit and running the cloth on it to scrape fibers from the spun yarn on the surface of the cloth. it can.
  • a non-woven fabric of 60 cm is allowed to stand on a horizontal surface, and a weight of 10 kg, which is larger than the width of the non-woven fabric, is placed on both ends in the winding length direction to fix the non-woven fabric.
  • a brushed non-woven fabric can be obtained by removing the brush and the weight from the non-woven fabric and cutting off the non-woven fabric on the surface to which the brush is moved.
  • the conditions for obtaining the brushed non-woven fabric for example, the following conditions are preferable.
  • the particulate water absorbing agent is evenly sprayed on the first base material.
  • the adhesive is evenly sprayed onto the second substrate.
  • the surface on which the particulate water absorbing agent of the first base material is sprayed and the surface on which the adhesive of the second base material is sprayed are overlapped and pressure-bonded so as to face each other.
  • the crimping is preferably heat crimping in the vicinity of the melting temperature of the adhesive.
  • a particulate water-absorbing agent and preferably an adhesive are sprayed on the second base material, passed through a heating furnace, and fixed to such an extent that the particulate water-absorbing agent does not dissipate.
  • the first base material is superposed on the surface of the second base material on which the particulate water absorbing agent is sprayed, and heat-bonded.
  • the particulate water-absorbing agent is uniformly sprayed to form a layer.
  • the first base material is placed on the surface of the second base material on which the particulate water absorbing agent is sprayed, and pressure-bonded using a roll press or the like.
  • the method (d) is preferable from the viewpoint of uniformly applying the adhesive.
  • the water-absorbent sheet can also be produced by using the methods (a) to (d) in combination.
  • the particulate water absorbing agent may be sprayed in a streak pattern by the methods (a) to (d) above. Specifically, the particulate water-absorbing agent is sprayed on the adhesive sprayed in a streak pattern on the base material (for example, the first base material), and the particulate water-absorbing agent of the base material is sprayed.
  • Another base material may be superposed on the surface and heat-bonded, or a base material (for example, a second base material) facing the base material (for example, the first base material) on which the particulate water absorbing agent is sprayed in a streak pattern may be used.
  • the adhesive is sprayed on the material) in a streak pattern, and the two base materials are placed on top of each other so that the surface on which the particulate water absorbent is sprayed and the surface on which the adhesive is sprayed face each other and heated. It may be crimped. That is, the following manufacturing methods (a') to (d') can be mentioned.
  • (A') Sprinkle the particulate water absorbent on the first base material in a streak pattern.
  • the adhesive is evenly sprayed onto the second substrate.
  • the surface on which the particulate water absorbing agent of the first base material is sprayed and the surface on which the adhesive of the second base material is sprayed are overlapped and pressure-bonded so as to face each other.
  • the crimping is preferably heat crimping in the vicinity of the melting temperature of the adhesive.
  • the particulate water absorbent is sprayed in a streak pattern, and preferably the adhesive is evenly sprayed and passed through a heating furnace so that the particulate water absorbent does not dissipate. Stick to a degree.
  • the first base material is superposed on the surface of the second base material on which the particulate water absorbing agent is sprayed, and heat-bonded.
  • the particulate water-absorbing agent is sprayed in a streak pattern to form a layer.
  • the first base material is placed on the surface of the second base material on which the particulate water absorbing agent is sprayed, and pressure-bonded using a roll press or the like.
  • the method of spraying the particulate water absorbing agent in a streak pattern is not particularly limited, but for example, it can be sprayed in a streak pattern by using a paper pattern.
  • a plate having the same size as the water-absorbent sheet and hollowed out in a striped pattern arranged in a certain width and length is used as a paper pattern.
  • This paper pattern is placed on a base material on which the particulate water absorbing agent is to be sprayed, and the particulate water absorbing agent is sprayed on the hollowed-out holes.
  • the paper pattern is removed after spraying the particulate water-absorbing agent, the particulate water-absorbing agent is sprayed in a streak pattern on the base material.
  • the adhesive is applied in stripes on the base material by screen printing or the like, the particulate water absorbent is sprayed on the base material, and then the particulate water absorbent that is not in contact with the adhesive on the base material is removed. By dropping it, the particulate water-absorbing agent can be sprayed on the base material in a streak pattern.
  • the water-absorbent sheet includes the wrapping sheet as shown in FIGS. 1 to 4, (3) the first base material, the water-absorbent layer, and the second base material are placed on the first base material.
  • a sheet obtained by crimping the first base material, the water absorption layer, and the second base material obtained through the steps (a) or (b) above is wrapped with the first base material facing down. Place it on the sheet, spray the adhesive on the second base material (the side where the water absorption layer is not crimped), which is the upper surface, and bend the remaining part of the wrapping sheet that protrudes from the first base material.
  • the adhesive surface of the second base material and the wrapping sheet are wrapped so as to be in contact with each other, turned upside down, and then pressure-bonded to obtain a water-absorbent sheet having the wrapping sheet. it can.
  • the water-absorbent sheet may be embossed for the purpose of improving the tactile sensation of the water-absorbent sheet and improving the liquid absorption performance.
  • the embossing may be performed at the same time when the first base material and the second base material are crimped, or may be performed after the sheet is manufactured. Further, the wrapping sheet may be embossed.
  • additives deodorant, fiber, antibacterial agent, gel stabilizer, etc.
  • the blending amount of the additive is preferably 0 to 50% by mass, and more preferably 1 to 10% by mass with respect to the mass of the particulate water absorbing agent.
  • a particulate water-absorbing agent mixed with an additive in advance may be used, or an additive may be added in the middle of the production process.
  • the dimensions of the manufactured water-absorbent sheet can be designed as appropriate. Usually, the width is 3 to 10 m and the length is several tens to several thousand m (in the state of continuous sheet or roll).
  • the manufactured water-absorbent sheet is cut and used according to the purpose (size of the absorbent body used).
  • the base materials as a method of fixing the base materials to each other or between the base materials and the particulate water-absorbing agent, (i) crimping may be used, and (ii) water or a water-soluble polymer.
  • Various binders dissolved or dispersed in a solvent may be used, the base materials may be heat-sealed at the melting point of the material of the base material itself (iii), or the base materials may be fixed by using an adhesive (iv).
  • the base materials, or the base material and the particulate water absorbent are preferably fixed using an (iv) adhesive.
  • the adhesive used may be a solution type, but a hot melt adhesive having high productivity and no problem of residual solvent is preferable because of the trouble of removing the solvent, the problem of the residual solvent, and the problem of productivity.
  • the hot melt adhesive may be contained in advance on the surface of the base material or the particulate water absorbent, or the hot melt adhesive may be separately used in the process of manufacturing the water absorbent sheet.
  • the form and melting point of the hot melt adhesive can be appropriately selected, and may be in the form of particles, fibers, nets, films, or liquids melted by heating. From the viewpoint of uniformly applying the adhesive, it is preferable to spray the melted hot melt adhesive.
  • the hot melt adhesive is sprayed on the second base material.
  • the first base material on which the particulate water absorbent was sprayed and the second base material on which the hot melt adhesive was sprayed were sprayed on the surface on which the particulate water absorbent was sprayed and the hot melt adhesive was sprayed.
  • a water-absorbent sheet can be manufactured by stacking the particles so as to face each other and pressure-bonding them under pressure.
  • the hot melt adhesive used in the present invention can be appropriately selected, but is preferably selected from ethylene-vinyl acetate copolymer adhesive, styrene elastomer adhesive, polyolefin adhesive, polyester adhesive and the like1 More than seeds can be used as appropriate.
  • polystyrene-based adhesive examples include polyethylene, polypropylene, and atactic polypropylene
  • examples of the styrene-based elastomer adhesive include a styrene-isoprene block copolymer (SIS) and a styrene-butadiene block copolymer (SBS).
  • SIS styrene-isoprene block copolymer
  • SBS styrene-butadiene block copolymer
  • styrene block copolymers such as styrene-isobutylene block copolymer (SIBS) and styrene-ethylene-butylene-styrene block copolymer (SEBS)
  • PET polyethylene terephthalate
  • ethylene-vinyl acetate copolymer adhesive an ethylene-vinyl acetate copolymer (EVA) adhesive; an ethylene-ethyl acrylate copolymer ( EEA), ethylene-butyl acrylate copolymer (EBA) and the like can be mentioned.
  • hot melt adhesives include, for example, Jaour Melt 3889U (JAOUR HOT MELT ADHESIVE, main component: styrene block copolymer, hydrocarbon resin, white mineral oil), Morescomelt TN-640Z (MORESCO, Inc.), Examples thereof include Morescomelt TN-781Z (manufactured by MORESCO Co., Ltd.) and Morescomelt TN-262Z (manufactured by MORESCO Co., Ltd.).
  • Jaour Melt 3889U JAOUR HOT MELT ADHESIVE, main component: styrene block copolymer, hydrocarbon resin, white mineral oil
  • Morescomelt TN-640Z MORESCO, Inc.
  • Morescomelt TN-781Z manufactured by MORESCO Co., Ltd.
  • Morescomelt TN-262Z manufactured by MORESCO Co., Ltd.
  • the water-absorbent sheet preferably contains an adhesive, and the adhesive is preferably a hot-melt adhesive, and the adhesive (for example, the amount (content) of the hot melt adhesive) is preferably 3.0 times or less, more preferably 0.01 to 2.5 times, the mass of the particulate water absorbent. , 0.05 to 2.0 times, more preferably. If the content of the adhesive (especially hot melt melt adhesive) is too high, not only is it disadvantageous in terms of cost and the mass of the water-absorbent sheet (increased mass of the paper diaper), but also the particulate water-absorbing agent regulates swelling. In response, it may reduce the water absorption capacity of the water-absorbent sheet.
  • the adhesive is preferably a hot-melt adhesive
  • the adhesive is preferably 3.0 times or less, more preferably 0.01 to 2.5 times, the mass of the particulate water absorbent. , 0.05 to 2.0 times, more preferably. If the content of the adhesive (especially hot melt melt adhesive) is too high, not only is it disadvantageous in
  • the absorbent article according to one embodiment of the present invention has a structure in which the water-absorbent sheet described in [2] is sandwiched between a liquid-permeable sheet and a liquid-impermeable sheet.
  • the liquid permeable sheet is located on the first base material side
  • the liquid permeable sheet is located on the second base material side. That is, the absorbent article according to the embodiment of the present invention is obtained by sandwiching the water-absorbent sheet of the present invention between the liquid-permeable sheet and the liquid-impermeable sheet, and the liquid-permeable sheet is the first.
  • the liquid impermeable sheet is located on the base material side and is located on the second base material side.
  • Specific examples of the absorbent article include paper diapers, incontinence pads, sanitary napkins, pet sheets, food drip sheets, water blocking agents for electric power cables, and the like.
  • liquid permeable sheet and the liquid permeable sheet those known in the technical field of absorbent articles can be used without particular limitation.
  • the absorbent article can be produced by a known method.
  • Acrylic acid production example Commercially available acrylic acid (acrylic acid dimer 2000 ppm, acetic acid 500 ppm, propionic acid 500 ppm, p-methoxyphenol 200 ppm) is supplied to the bottom of a high boiling point impurity separation tower having 50 steps of a dam-free perforated plate, and the reflux ratio is set to 1.
  • Acrylic acid (acrylic acid dimer 20 ppm, acetic acid 50 ppm, propionic acid 50 ppm, furfural 1 ppm or less) by distilling as, after removing dimer (acrylic acid dimer) composed of maleic acid and acrylic acid, and further performing crystallization. , Protoanemonin (1 ppm or less) was obtained, and 50 ppm of p-methoxyphenol was further added after distillation.
  • the above reaction solution was supplied to a reactor formed by attaching a lid to a stainless steel double-armed kneader with an internal volume of 10 L having two sigma type blades, and the system was nitrogenized while keeping the reaction solution at 30 ° C. Gas replacement was performed to remove dissolved oxygen in the reaction solution. Subsequently, 28.66 g of a 10 mass% aqueous solution of sodium persulfate and 35.28 g of a 1 mass% aqueous solution of L-ascorbic acid were added while stirring the reaction solution, and the polymerization started after about 1 minute. 40 minutes after the start of the polymerization, the hydrogel polymer was taken out.
  • the obtained hydrogel polymer was subdivided into particles having a size of about 2 to 4 mm.
  • the subdivided hydrogel polymer was spread on a wire mesh of 50 mesh (mesh size 300 ⁇ m) and dried with hot air at 175 ° C. for 65 minutes.
  • the dried product was pulverized using a roll mill, further classified and blended with a wire mesh having a mesh size of 600 ⁇ m to obtain an amorphous crushed water-absorbent resin (1-1) having an average particle diameter of 350 ⁇ m.
  • a surface cross-linking agent aqueous solution containing 0.03 parts by mass of ethylene glycol diglycidyl ether, 1.0 part by mass of propylene glycol, and 3.0 parts by mass of water in 100 parts by mass of the obtained water-absorbent resin (1-1) 4.03.
  • the parts by mass were spray-mixed.
  • the above mixture was heat-treated at a heat medium temperature of 100 ° C. for 40 minutes using a paddle-type mixing heat treatment machine to obtain a surface-crosslinked water-absorbent resin (1-2). 3.0 parts by mass of water was spray-mixed with 100 parts by mass of the obtained surface-crosslinked water-absorbent resin (1-2) and cured at 60 ° C.
  • a water-absorbent resin (1-3) was obtained by passing through a sieve.
  • the above reaction solution was supplied to a reactor formed by attaching a lid to a stainless steel double-armed kneader with an internal volume of 10 L having two sigma type blades, and the system was nitrogenized while keeping the reaction solution at 30 ° C. Gas replacement was performed to remove dissolved oxygen in the reaction solution. Subsequently, 29.07 g of a 10 mass% aqueous solution of sodium persulfate and 35.78 g of a 1 mass% aqueous solution of L-ascorbic acid were added while stirring the reaction solution, and the polymerization started after about 1 minute. 40 minutes after the start of the polymerization, the hydrogel polymer was taken out.
  • the obtained hydrogel polymer was subdivided into particles having a size of about 2 to 4 mm.
  • the subdivided hydrogel polymer was spread on a wire mesh of 50 mesh (mesh size 300 ⁇ m) and dried with hot air at 175 ° C. for 65 minutes.
  • the dried product was pulverized using a roll mill, further classified and blended with a wire mesh having a mesh size of 600 ⁇ m to obtain an amorphous crushed water-absorbent resin (2-1) having an average particle diameter of 350 ⁇ m.
  • a surface cross-linking agent aqueous solution containing 0.03 parts by mass of ethylene glycol diglycidyl ether, 1.0 part by mass of propylene glycol, and 3.0 parts by mass of water in 100 parts by mass of the obtained water-absorbent resin (2-1) 4.03.
  • the parts by mass were spray-mixed.
  • the above mixture was heat-treated at a heat medium temperature of 100 ° C. for 40 minutes using a paddle-type mixing heat treatment machine to obtain a surface-crosslinked water-absorbent resin (2-2). 3.0 parts by mass of water was spray-mixed with 100 parts by mass of the obtained surface-crosslinked water-absorbent resin (2-2) and cured at 60 ° C.
  • a water-absorbent resin (2-3) was obtained by passing through a sieve.
  • the above reaction solution was supplied to a reactor formed by attaching a lid to a stainless steel double-armed kneader with an internal volume of 10 L having two sigma type blades, and the system was nitrogenized while keeping the reaction solution at 30 ° C. Gas replacement was performed to remove dissolved oxygen in the reaction solution. Subsequently, 30.68 g of a 10 mass% aqueous solution of sodium persulfate and 37.76 g of a 1 mass% aqueous solution of L-ascorbic acid were added while stirring the reaction solution, and the polymerization started after about 1 minute. 40 minutes after the start of the polymerization, the hydrogel polymer was taken out.
  • the obtained hydrogel polymer was subdivided into particles having a size of about 2 to 4 mm.
  • the subdivided hydrogel polymer was spread on a wire mesh of 50 mesh (mesh size 300 ⁇ m) and dried with hot air at 175 ° C. for 65 minutes.
  • the dried product was pulverized using a roll mill, further classified and blended with a wire mesh having a mesh size of 600 ⁇ m to obtain an amorphous crushed water-absorbent resin (3-1) having an average particle diameter of 350 ⁇ m.
  • the surface tension means the surface tension of the aqueous solution when the particulate water absorbent is dispersed in the 0.90 mass% sodium chloride aqueous solution.
  • a plate method using a platinum plate is adopted, and the plate is sufficiently washed with deionized water before each measurement and heated and washed with a gas burner before use.
  • Non-woven fabric E with a length of 10 cm and a width of 40 cm (mainly composed of pulp fiber. Thickness 0.4 mm. Made by the airlaid method. Corresponds to the second base material. Grain amount: 47 g / m 2 ) and styrene. After uniformly spraying 0.5 to 0.7 g of an adhesive containing butadiene rubber (spray glue 77, manufactured by 3M Japan Ltd.) (spray amount: 12.5 to 17.5 g / m 2 ), the adhesive sprayed surface. In addition, 9.0 g (spray amount: 225 g / m 2 ) of the particulate water absorbing agent (1) was uniformly sprayed.
  • spray glue 77 an adhesive containing butadiene rubber
  • an air-through non-woven fabric A (corresponding to the first base material, having a basis weight: 41 g / m 2 ) having a thickness of 1.4 mm and containing olefin as a main component, which was cut into a length of 10 cm and a width of 40 cm, was applied to the non-woven fabric E.
  • the intermediate sheet X was obtained by placing it on the surface on which the particulate water absorbing agent was sprayed and pressure-bonding it.
  • a spunbonded non-woven fabric having a thickness of 0.1 mm and having an olefin as a main component, cut into a length of 24 cm and a width of 40 cm (corresponding to a wrapping sheet, a texture amount of 13 g / m 2 , a bulk density of 0.13 g / cm 3 ).
  • the non-woven fabric A side of the intermediate sheet X was placed so as to face and contact the spunbonded non-woven fabric.
  • Example 2 A spunbonded non-woven fabric (corresponding to a wrapping sheet) having a thickness of 0.1 mm and containing olefin as a main component, which was cut into a length of 24 cm and a width of 40 cm, was laid, and an olefin cut into a length of 10 cm and a width of 40 cm was placed on the spunbonded non-woven fabric (corresponding to a wrapping sheet).
  • An air-through non-woven fabric A (corresponding to the first base material) having a thickness of 1.4 mm, which is the main component, is placed, and 9.0 g (spray amount: 225 g / m) of the particulate water absorbent (1) is placed on the surface of the non-woven fabric A. 2 ) It was sprayed evenly.
  • the non-woven fabric E cut into a length of 10 cm and a width of 40 cm (mainly composed of pulp fiber. Thickness 0.4 mm. Made by the airlaid method. Corresponds to the second base material. Grain amount: 47 g / m
  • An adhesive containing styrene-butadiene rubber (spray glue 77, manufactured by 3M Japan Ltd.) was uniformly sprayed on the surface of 2) in an amount of 0.5 to 0.7 g (spray amount: 12.5 to 17.5 g / m). 2 ).
  • the surface of the non-woven fabric A sprayed with the particulate water absorbent and the surface of the non-woven fabric E sprayed with the adhesive are overlapped so as to face each other (contact), pressure-bonded, and then styrene-butadiene is further applied to the non-woven fabric E.
  • the remaining portion of the spunbonded non-woven fabric located in the lowermost layer is bent so that the non-woven fabric E of the intermediate sheet Y (the surface of the intermediate sheet Y on the non-woven fabric E side) comes into contact with the spunbonded non-woven fabric.
  • pressure-bonding was performed to obtain a water-absorbent sheet (2).
  • Example 3 A water-absorbing sheet (3) was obtained in the same manner as in Example 2 except that the particulate water-absorbing agent (2) was used instead of the particulate water-absorbing agent (1).
  • Example 4 A water-absorbing sheet (4) was obtained in the same manner as in Example 2 except that the particulate water-absorbing agent (3) was used instead of the particulate water-absorbing agent (1).
  • Example 5 A water-absorbing sheet (5) was obtained in the same manner as in Example 2 except that the particulate water-absorbing agent (4) was used instead of the particulate water-absorbing agent (1).
  • Example 6 A water-absorbent sheet (6) was obtained in the same manner as in Example 2 except that an air-through nonwoven fabric B (with a basis weight: 43 g / m 2) having a thickness of 2.0 mm was used instead of the air-through nonwoven fabric A.
  • Example 7 A water-absorbent sheet (7) was obtained in the same manner as in Example 2 except that an air-through nonwoven fabric C (with a basis weight: 37 g / m 2) having a thickness of 1.5 mm was used instead of the air-through nonwoven fabric A.
  • Example 8 A water-absorbent sheet (8) was obtained in the same manner as in Example 2 except that an air-through nonwoven fabric D (weight: 45 g / m 2) having a thickness of 1.5 mm was used instead of the air-through nonwoven fabric A.
  • Example 9 Water absorption in the same manner as in Example 2 except that a spunlace non-woven fabric F (composed of PET resin and pulp, having a thickness of 0.4 mm and a grain size of 45 g / m 2) was used instead of the non-woven fabric E. Sheet (9) was obtained.
  • a spunlace non-woven fabric F composed of PET resin and pulp, having a thickness of 0.4 mm and a grain size of 45 g / m 2
  • Sheet (9) was obtained.
  • Example 10 A water-absorbent sheet (10) was obtained in the same manner as in Example 2 except that an air-through nonwoven fabric G (weight: 20 g / m 2) having a thickness of 0.7 mm was used instead of the nonwoven fabric A.
  • an air-through nonwoven fabric G weight: 20 g / m 2 having a thickness of 0.7 mm was used instead of the nonwoven fabric A.
  • the non-woven fabric E cut into a length of 10 cm and a width of 40 cm (mainly composed of pulp fiber. Thickness 0.4 mm. Made by the airlaid method. Corresponds to the second base material. Grain amount: 47 g / m
  • An adhesive containing styrene-butadiene rubber (spray glue 77, manufactured by 3M Japan Ltd.) was uniformly sprayed on the surface of 2) in an amount of 0.5 to 0.7 g (spray amount: 12.5 to 17.5 g / m). 2 ). Then, the surface of the non-woven fabric A on which the particulate water-absorbing agent was sprayed and the surface of the non-woven fabric E on which the adhesive was sprayed were overlapped (contacted) and pressure-bonded.
  • an adhesive containing styrene-butadiene rubber on the surface of the non-woven fabric E (similar to the non-woven fabric E used above (thickness 0.4 mm), which corresponds to the first base material) cut into a length of 10 cm and a width of 40 cm.
  • (Spray glue 77, manufactured by 3M Japan Ltd.) was uniformly sprayed in an amount of 0.5 to 0.7 g (spray amount: 12.5 to 17.5 g / m 2 ).
  • the surface of the non-woven fabric A on which the particulate water-absorbing agent was sprayed and the surface of the non-woven fabric E on which the adhesive was sprayed were overlapped (contacting each other) and pressure-bonded to obtain an intermediate sheet Z. ..
  • an adhesive containing styrene-butadiene rubber (spray glue 77, manufactured by 3M Japan Ltd.) was applied to the non-woven fabric E of the intermediate sheet Z (the non-woven fabric side on which the particulate water absorbent was sprayed for the first time) from 0.1 to 0. .2 g was uniformly sprayed (spray amount: 2.5 to 5.0 g / m 2 ), then cut into 24 cm in length and 40 cm in width, wrapped in a spunbonded non-woven fabric containing olefin as a main component and having a thickness of 0.1 mm.
  • a water-absorbent sheet (11) was obtained by pressure-bonding.
  • Comparative Example 1 the transmittance of the particulate water-absorbing agent of the non-woven fabric E corresponding to the first base material was 0.3% by mass, and the content ratio of the particulate water-absorbing agent was 0%. Further, in the water-absorbent sheet obtained in Comparative Example 1, "thickness of the first base material / thickness of the second base material" was 1.
  • nonwoven fabric A2 styrene-butadiene was placed on the surface of an air-through non-woven fabric A having a thickness of 1.4 mm (corresponding to a second base material.
  • the non-woven fabric A is referred to as "nonwoven fabric A2" for convenience) cut into a length of 10 cm and a width of 40 cm.
  • An adhesive containing rubber spray glue 77, manufactured by 3M Japan Ltd.
  • Adhesive containing styrene-butadiene rubber (spray glue 77, manufactured by 3M Japan Ltd.) is evenly sprayed at 0.1 to 0.2 g (spray amount: 2.5 to 5.0 g / m 2 ), and the intermediate Sheet Z2 was obtained.
  • the excess portion of the spunbonded non-woven fabric located in the bottom layer is bent and wrapped so that the surface of the non-woven fabric sprinkled with the particulate water absorbent (1) is in contact with the spunbonded non-woven fabric so that the top and bottom are turned upside down.
  • pressure-bonding was performed to obtain a water-absorbent sheet (13).
  • An adhesive containing styrene-butadiene rubber (spray glue 77, manufactured by 3M Japan Ltd.) was applied only to the portion of the spunbonded non-woven fabric in contact with the surface of the non-woven fabric sprinkled with the particulate water-absorbing agent (1). 7 g was evenly sprayed and then wrapped.
  • Example 4 The same as in Example 2 except that the spunlace non-woven fabric F (composed of PET resin and pulp, having a thickness of 0.4 mm and a grain size of 45 g / m 2) was used instead of the air-through non-woven fabric A. , A water-absorbent sheet (14) was obtained.
  • the spunlace non-woven fabric F composed of PET resin and pulp, having a thickness of 0.4 mm and a grain size of 45 g / m 2
  • a water-absorbent sheet (14) was obtained.
  • the transmittance of the particulate water-absorbing agent of the non-woven fabric F corresponding to the first base material was 1% by mass, and the content ratio of the particulate water-absorbing agent was 0%. Further, in the water-absorbent sheet obtained in Comparative Example 4, the "thickness of the first base material / the thickness of the second base material" was 1.
  • the non-woven fabrics A to G used in this example were all water permeable sheets.
  • Dial thickness gauge Measured using a large type (thickness measuring instrument) (manufactured by Ozaki Seisakusho Co., Ltd., model number: JB, stylus: anvil top and bottom ⁇ 50 mm). The number of measurement points was 5 times at different points, and the measured value was an average value of 5 points. When measuring the thickness, the thickness was measured by slowly releasing the hand from the handle so that pressure was not applied to the non-woven fabric as much as possible.
  • ⁇ Calculation method of bulk density of non-woven fabric> The weight of the non-woven fabric cut into a size of 10 cm or more in length and 40 cm or more in width was measured.
  • the volume of the non-woven fabric was calculated by multiplying the vertical and horizontal lengths of the non-woven fabric and the thickness measured from ⁇ thickness measurement>, respectively, and the bulk density was calculated by dividing the weight of the non-woven fabric by the volume of the non-woven fabric.
  • the mesh of the sieve and the flat surface were sufficiently separated from each other so that the non-woven fabric and the physiological saline passing through the mesh did not come into contact with the mesh.
  • the non-woven fabric absorbed the physiological saline and the diffusion of the liquid was completed, the area where the physiological saline was diffused was measured.
  • a JIS standard sieve (The IIDA TESTING SIEVE: inner diameter 80 mm; JIS Z8801-1 (2000)) having a mesh 32 with an opening of 850 ⁇ m, or a non-woven fabric cut to a diameter of 80 mm in a sieve 31 corresponding to the JIS standard sieve (No. 1).
  • the base material 11) of No. 1 was installed as shown in FIG. 5, and the periphery was fastened with a tape 33 (at least a diameter of 75 mm or more secures an area through which particles can permeate).
  • the non-woven fabric first base material 11
  • one taken out from the water-absorbent sheet by the method described later may be used.
  • the particulate water absorbent 14 (weight average particle diameter: 367 ⁇ m, particle size distribution: 850 ⁇ m to 600 ⁇ m is 6.1% 600 ⁇ m).
  • ⁇ 500 ⁇ m is 14.5% 500 ⁇ m ⁇ 300 ⁇ m is 50% 300 ⁇ m ⁇ 150 ⁇ m is 27.6% 150 ⁇ m ⁇ 45 ⁇ m is 1.9% 45 ⁇ m or less 0.1%) 10.0 g is added and a low tap type sieve shaker (stock) Using an ES-65 type sieve shaker manufactured by Iida Seisakusho Co., Ltd .; rotation speed 230 rpm, impact number 130 rpm), the particles were shaken for 5 minutes under the conditions of room temperature (20 to 25 ° C.) and relative humidity of 50% RH.
  • the particulate water absorbing agent 14 (that is, particles existing in the portion 31a below the mesh 32 of the sieve 31) has passed through the non-woven fabric (first base material 11) and the mesh 32 of the sieve 31 corresponding to the JIS standard sieve.
  • the mass (W (g)) of the water absorbing agent 14) was measured, and the transmittance of the particulate water absorbing agent was calculated according to the following formula (i). The measurement was performed three times, and the average value was calculated. In Table 1, the transmittance (mass%) of the particulate water absorbent is shown as "transmittance (mass%)".
  • the fibers of the non-woven fabric and the structural thickness can be taken out without changing, and the transmittance can be measured accurately.
  • Various means can be considered for cooling the water-absorbent sheet, such as putting it in a constant temperature bath at -10 ° C or lower for a certain period of time, spraying a cooling spray, or spraying liquid nitrogen, but without changing the fiber, structure, or thickness of the non-woven fabric.
  • it is not particularly limited as long as it is carried out under the condition that the particulate water absorbing agent contained in the water absorbing sheet does not absorb moisture.
  • the water content is adjusted to 10% by mass or less, preferably 5 ⁇ 2% by mass, and the above-mentioned transmittance and various specifications specified in the present application. Physical properties may be measured.
  • the drying conditions for adjusting the water content are not particularly limited as long as the water-absorbent resin (particulate water-absorbing agent) is not decomposed or modified, but vacuum drying is preferable.
  • the content ratio (%) of the particulate water absorbing agent in the first base material was calculated by the following formula.
  • Content ratio (%) of particulate water-absorbing agent in the first base material particle-like water-absorbing agent area (I) in the first base material / total particle-like water-absorbing agent area (II) ⁇ 100 That is, the content ratio of the particulate water absorbing agent in the first base material is represented by the area% with respect to the total area of the particulate water absorbing agent. Since the particulate water absorbing agent is less than a few percent on the surface of the first base material on the side where the liquid to be absorbed is introduced, it can be considered that it is not present.
  • the acrylic plate 63 had a length of 400 mm in the direction of the inclined surface, and was fixed by a gantry 60 so as to form an angle of 20 ° with respect to the horizontal.
  • the acrylic plate 63 had a width of 200 mm and a thickness of 3 mm. Since the surface of the acrylic plate 63 is smooth, the liquid did not stay or be absorbed by the plate.
  • the funnel 64 was fixed vertically above the inclined acrylic plate 63 using the gantry 60.
  • the funnel 64 used was one in which the liquid was added at 7 mL / sec.
  • a metal tray 65 was installed at the bottom of the acrylic plate 63, and received all the test liquid that flowed down as a leak, and recorded its mass with an accuracy of 0.1 g.
  • the leak test on the slope using such a device was performed according to the following procedure. As shown in FIG. 10, the back surface of the water-absorbent sheet 10 cut into a size of 100 mm in length and 100 mm in width was attached onto the acrylic plate 63.
  • a mark was placed 1.5 cm below the top of the water-absorbent sheet, and the funnel inlet was fixed so that the distance vertically above the mark was 15 ⁇ 2 mm.
  • the amount of leakage in the table is the total value of the amount of leakage from the first to the third time.
  • Table 1 shows the configurations and evaluation results of the water-absorbent sheets of Examples 1 to 10 and Comparative Examples 1 to 4.
  • the water-absorbent sheets of Examples 1 to 10 had a significantly smaller amount of reversion as compared with the water-absorbent sheets of Comparative Examples 1 to 4, and the leakage from the water-absorbent sheets was also significantly reduced. It was a thing.
  • Comparative Example 1 having a multi-layer structure
  • Comparative Example 2 and Comparative Example 4 in which the thickness ratio of the first base material to the second base material was 1, the amount of reversion was significantly increased.
  • Example 11 A spunbonded non-woven fabric (corresponding to a wrapping sheet) having a thickness of 0.1 mm and mainly composed of polyolefin fiber, which was cut into a length of 24 cm and a width of 40 cm, was laid, and a polyolefin cut into a length of 10 cm and a width of 40 cm was laid in the center thereof. 9.
  • a raised air-through non-woven fabric A (corresponding to the first base material) having a thickness of 1.4 mm and containing fibers as a main component is placed on the raised surface of the non-woven fabric A, and the particulate water absorbent (2) is applied. 0 g (spray amount: 225 g / m 2 ) was uniformly sprayed. The brushing treatment of the non-woven fabric A was performed according to the method described later.
  • the non-woven fabric E cut into a length of 10 cm and a width of 40 cm (mainly composed of pulp fiber. Thickness 0.4 mm. Prepared by the air-laid method. Corresponds to the second base material. Grain amount: 47 g / m 2 )
  • 0.8 g of a hot melt adhesive manufactured by Jaour Melt 3889U, JAOUR HOT MELT ADHESIVE, main component: styrene block copolymer, hydrocarbon resin, white mineral oil
  • spray amount 20.0 g / m 2 ).
  • the surface of the nonwoven fabric A on which the particulate water absorbing agent was sprayed and the surface of the nonwoven fabric E on which the adhesive was sprayed were overlapped so as to face each other (contacting each other) and pressure-bonded to obtain an intermediate sheet Y.
  • a hot melt adhesive manufactured by Jaour Melt 3889U, JAOUR HOT MELT ADHESIVE heated to 135 ° C., main component: styrene block copolymer, hydrocarbon resin, white mineral oil ) 0.3 g was sprayed (spray amount: 7.5 g / m 2 ).
  • the excess portion of the spunbonded non-woven fabric is bent, wrapped so that the surface of the non-woven fabric E of the intermediate sheet Y and the spunbonded non-woven fabric are in contact with each other, turned upside down, and then pressurized. It was worn to obtain a water-absorbent sheet (21).
  • Example 12 A water-absorbing sheet (22) was obtained in the same manner as in Example 1 except that the spraying amount of the particulate water-absorbing agent was 12.0 g (spraying amount: 300 g / m 2).
  • Example 13 A water-absorbent sheet (23) was obtained in the same manner as in Example 2 except that the non-woven fabric A which had not been brushed was used instead of the non-woven fabric A which had been brushed.
  • Example 14 Example 1 except that the adhesive to be sprayed on the non-woven fabric E was 0.8 g (spray amount: 20.0 g / m 2) of an adhesive containing styrene-butadiene rubber (spray glue 77, manufactured by 3M Japan Ltd.). In the same manner as above, a water-absorbent sheet (24) was obtained.
  • Example 15 A water-absorbing sheet (25) was obtained in the same manner as in Example 12 except that the particulate water-absorbing agent (5) obtained by the following production method was used.
  • the above reaction solution was supplied to a reactor formed by attaching a lid to a stainless steel double-armed kneader with an internal volume of 10 L having two sigma type blades, and the system was nitrogenized while keeping the reaction solution at 30 ° C. Gas replacement was performed to remove dissolved oxygen in the reaction solution. Subsequently, 30.68 g of a 10 mass% aqueous solution of sodium persulfate and 37.76 g of a 1 mass% aqueous solution of L-ascorbic acid were added while stirring the reaction solution, and the polymerization started after about 1 minute. 40 minutes after the start of the polymerization, the hydrogel polymer was taken out.
  • the obtained hydrogel polymer was subdivided into particles having a size of about 2 to 4 mm.
  • the subdivided hydrogel polymer was spread on a wire mesh of 50 mesh (mesh size 300 ⁇ m) and dried with hot air at 175 ° C. for 65 minutes.
  • the dried product was pulverized using a roll mill, further classified and blended with a wire mesh having a mesh size of 600 ⁇ m to obtain an amorphous crushed water-absorbent resin (5-1) having an average particle size of 380 ⁇ m.
  • Example 16 A water-absorbing sheet (26) was obtained in the same manner as in Example 12 except that the particulate water-absorbing agent (6) obtained by the following production method was used.
  • the above reaction solution was supplied to a reactor formed by attaching a lid to a stainless steel double-armed kneader with an internal volume of 10 L having two sigma type blades, and the system was nitrogenized while keeping the reaction solution at 30 ° C. Gas replacement was performed to remove dissolved oxygen in the reaction solution. Subsequently, 28.66 g of a 10 mass% aqueous solution of sodium persulfate and 35.28 g of a 1 mass% aqueous solution of L-ascorbic acid were added while stirring the reaction solution, and the polymerization started after about 1 minute.
  • the dried product was pulverized using a roll mill, further classified and blended with a wire mesh having a mesh size of 600 ⁇ m to obtain an amorphous crushed water-absorbent resin (6-1) having an average particle diameter of 350 ⁇ m.
  • a surface cross-linking agent aqueous solution 4.03 consisting of 0.03 parts by mass of ethylene glycol diglycidyl ether, 1.0 part by mass of propylene glycol, and 3.0 parts by mass of water in 100 parts by mass of the obtained water-absorbent resin (6-1).
  • the parts by mass were spray-mixed.
  • the above mixture was heat-treated at a heat medium temperature of 100 ° C. for 40 minutes using a paddle-type mixing heat treatment machine to obtain a surface-crosslinked water-absorbent resin (6-2). 3.0 parts by mass of water was spray-mixed with 100 parts by mass of the obtained surface-crosslinked water-absorbent resin (6-2) and cured at 60 ° C.
  • a water-absorbent resin (6-3) was obtained by passing through a sieve.
  • Example 17 A water-absorbing sheet (27) was obtained in the same manner as in Example 12 except that the particulate water-absorbing agent (7) obtained by the following production method was used.
  • Particular water absorbent (7) In a polypropylene container with a capacity of 2 liters, 351.7 g of acrylic acid, 0.860 g of polyethylene glycol diacrylate (molecular weight 523) as an internal cross-linking agent (0.034 mol% with respect to a carboxyl group-containing unsaturated monomer), 1 Add 2.15 g of a 0.0 wt% diethylenetriamine-5 acetic acid / 3 sodium (DTPA / 3Na) aqueous solution, 149.0 g of a 48.5 wt% sodium hydroxide aqueous solution, and 336.2 g of deionized water (ion-exchanged water). The mixture was mixed to prepare a monomer aqueous solution (a').
  • DTPA / 3Na diethylenetriamine-5 acetic acid / 3 sodium
  • deionized water ion-exchanged water
  • the monomer aqueous solution (a') was cooled with stirring.
  • 144.8 g of a 48.5% by weight sodium hydroxide aqueous solution adjusted to 40 ° C. was added and mixed to prepare a monomer aqueous solution (a).
  • the temperature of the monomer aqueous solution (a) was raised to 78.2 ° C. by the heat of neutralization in the second stage immediately after the production.
  • precipitates were observed, but they gradually dissolved to become a transparent uniform solution.
  • a stainless steel bat-shaped container bottom surface 340 ⁇ 340 mm, height 25 mm, inner surface
  • pour into Teflon® coating in an open system.
  • the time from the start of neutralization in the second stage to the pouring of the monomer aqueous solution (a) into the vat-type container was 55 seconds, and the vat-type container was a hot plate (NEO HOTPLATE HI-1000 / Inuchi Seieidou Co., Ltd.). The company) was used to heat the surface until the surface temperature reached 40 ° C.
  • the polymerization reaction started 60 seconds after the above-mentioned monomer aqueous solution (a) was poured into the vat-shaped container.
  • the polymerization reaction proceeded by expanding and foaming in all directions while generating water vapor, and then contracted to a size slightly larger than that of the vat-shaped container.
  • a hydrogel-like crosslinked polymer hereinafter referred to as “hydrogen gel”) (7-1) was taken out.
  • the hydrogel (7-1) obtained by the above polymerization reaction was cut into strips, supplied to a screw extruder and pulverized to obtain a particulate hydrogel (7-2).
  • the screw extruder is provided with a perforated plate having a diameter of 100 mm, a hole diameter of 11.0 mm, a number of holes of 40, an aperture ratio of 62.5%, and a thickness of 10 mm at the tip, and the outer diameter of the screw shaft is 86 mm. It was.
  • the gel crushing is performed by simultaneously supplying the strip-shaped hydrogel (7-1) and water vapor from different supply ports in a state where the rotation speed of the screw shaft of the screw extruder is 130 rpm. It was.
  • the supply amount of the hydrogel (7-1) was 4640 g / min, and the supply amount of water vapor was 83 g / min.
  • This particulate hydrogel (7-2) is spread on a 50-mesh wire mesh, dried with hot air at 190 ° C. for 30 minutes, and the dried product is crushed using a roll mill (WML type roll crusher / Inoguchi Giken Co., Ltd.). Then, by further sieving with a JIS sieve having a mesh size of 850 ⁇ m, 600 ⁇ m, 500 ⁇ m, 300 ⁇ m, and 150 ⁇ m and then preparing the mixture, the weight average particle size (D50) is 305 ⁇ m and the logarithmic standard deviation ( ⁇ ) of the particle size distribution is 0.35. An amorphous crushed precursor water-absorbent resin (A) was obtained. The centrifuge holding capacity (CRC) of the precursor water-absorbent resin (A) was 48.4 (g / g).
  • CRC centrifuge holding capacity
  • a surface cross-linking agent solution consisting of 0.03 parts by weight of ethylene glycol diglycidyl ether, 1.5 parts by weight of propylene glycol and 3.5 parts by weight of deionized water was uniformly applied to 100 parts by weight of the precursor water-absorbent resin (A).
  • the precursor water-absorbent resin (A) was uniformly applied to 100 parts by weight of the precursor water-absorbent resin (A).
  • cooling was performed, and an aqueous solution consisting of 1 part by weight of deionized water and 0.05 part by weight of diethylenetriamine-5 acetic acid / 3 sodium (DTPA / 3Na) was uniformly mixed with 100 parts by weight of the water-absorbent resin.
  • DTPA / 3Na diethylenetriamine-5 acetic acid / 3 sodium
  • the mixture After drying at 60 ° C. for 1 hour, the mixture was passed through a JIS standard sieve having an opening of 850 ⁇ m, and 0.3 parts by weight of silicon dioxide (trade name: Leoloseal QS-20, manufactured by Tokuyama Corporation) was mixed.
  • silicon dioxide trade name: Leoloseal QS-20, manufactured by Tokuyama Corporation
  • 30 g of water-absorbent resin was put into a mayonnaise bottle having a capacity of 225 mL together with silicon dioxide, and the mixture was mixed for 60 minutes by vibration of a Tarbra shaker mixer T2F type (manufactured by Simmal Enterprises Co., Ltd.), and the water-absorbent resin particles (7) were mixed. Obtained.
  • Example 18 A 0.1 mm thick spunbonded non-woven fabric (corresponding to a wrapping sheet) mainly composed of polyolefin fiber cut into a length of 24 cm and a width of 40 cm is laid, and a polyolefin cut into a length of 10 cm and a width of 40 cm is laid in the center thereof.
  • a 1.4 mm thick brushed air-through non-woven fabric A (corresponding to the first base material) containing fibers as the main component is placed on the brushed surface of the non-woven fabric A and heated to 135 ° C. to make it liquid.
  • the non-woven fabric E cut into a length of 10 cm and a width of 40 cm (mainly composed of pulp fiber. Thickness 0.4 mm. Made by the airlaid method. Corresponds to the second base material. Grain amount: 47 g / m 2 ) and the surfaces sprayed with the adhesive and the particulate water absorbent of the non-woven fabric A were overlapped so as to face each other (contact each other) and pressure-bonded to obtain an intermediate sheet Y.
  • Hot melt adhesive manufactured by Jaour Melt 3889U, JAOUR HOT MELT ADHESIVE
  • styrene block copolymer hydrocarbon resin, white mineral oil.
  • 0.3 g was uniformly sprayed (spray amount: 7.5 g / m 2 ).
  • the excess portion of the spunbonded non-woven fabric is bent, wrapped so that the surface of the non-woven fabric E of the intermediate sheet Y and the spunbonded non-woven fabric are in contact with each other, turned upside down, and then pressurized. It was worn to obtain a water-absorbent sheet (28).
  • the non-woven fabric is placed on a desk having a horizontal and smooth surface, and 10 kg weights are placed on both ends of the non-woven fabric in the long axis direction to fix the non-woven fabric.
  • Hold the brush (length: 100 mm, hair length: 25 mm, brush material: polybutylene terephthalate resin, brush diameter: 0.2 mm) perpendicular to the long axis of the non-woven fabric from above, and point vertically downward toward the surface of the non-woven fabric. Lower it and push the non-woven fabric with the tip of the brush as it is, and insert it until it touches the surface of the desk. Then, the brush is horizontally moved to a desired length without applying a load in the longitudinal direction of the non-woven fabric. The brush and weight are removed, and the non-woven fabric in the portion where the brush is moved is cut off to obtain a brushed non-woven fabric.
  • the brushed non-woven fabric is cut into a size of 20 cm ⁇ 10 cm, and a smooth plastic plate having a width of 3 cm is inserted under the non-woven fabric perpendicularly to the long axis of the non-woven fabric (see FIG. 11 (a)).
  • Both ends of the long shaft of the hanging non-woven fabric are clipped from below with clips having a weight of 70 g and a pinch opening of 10 cm or more (see FIG. 11B).
  • a photograph of the upper surface of the non-woven fabric stretched on the plastic plate is taken from the direction perpendicular to the short axis of the non-woven fabric (taken from the direction of the arrow in FIG. 11B).
  • the water-absorbent sheet 10 produced in a length of 10 cm and a width of 40 cm was wrapped with a liquid-impermeable sheet 21 having a length of 14 cm and a width of 40 cm so as to have an opening at the top.
  • a water-absorbent sheet 10 wrapped with a liquid-impermeable sheet 21 is placed on a flat surface, and a liquid injection cylinder 45 (inner diameter 26 mm, outer diameter 30 mm, length 150 mm, weight 34 g) is placed on the liquid injection cylinder 45 (inner diameter 30 mm, outer diameter 30 mm, length 150 mm, weight 34 g).
  • a weight having a diameter of 60 mm, a length of 62 mm, and a weight of 1030 g was attached, and a weight (FIG. 12) was placed in the center of the water-absorbent sheet 10 as shown in FIG.
  • 0.9 wt% sodium chloride and 0.002 wt% edible blue No. 1 (Tokyo Chemical Industry) at 23 ° C. were put into the liquid injection cylinder 45 using a funnel 42 capable of charging the liquid at a flow velocity of 7 ml / sec. 80 g of an aqueous solution containing (Co., Ltd.) was added (FIG. 14).
  • the weight 44 was removed, and the first reversion amount (g) was measured from the weight increment of the filter paper 43. 1 minute after removing the weight 44, the same operation (adding the liquid ⁇ measuring the water absorption time of the liquid ⁇ 10 minutes after adding the filter paper 43 and the weight 44 (1200 g), holding for 1 minute ⁇ 1 minute later Holding ⁇ removing the weight, measuring the amount of reversion) was repeated, and the amount of reversion was measured the second time (g) and the amount of reversion was measured the third time (g). Table 1 shows the total of the measured water absorption time and the amount of reversion from the first to the third.
  • the dropout rate of the particulate water absorbent was calculated as follows. After measuring the weight of a 40 cm x 10 cm water-absorbent sheet, the surface on the second base material side and the entire measurement surface, and the surface on the first base material side from the outer circumference to the inside up to 1 cm are covered. It was covered with a vinyl sheet and fixed with tape. 300 ml of physiological saline (0.9% sodium chloride aqueous solution) was evenly poured on the surface of the water-absorbent sheet covered with a vinyl sheet.
  • a muff (ASS ONE, 360 ° rotary type with muff claws) is attached to each of the two support rods of the electromagnetic sieve shaker (Resch, AS200), and one SUS pipe (diameter 13 mm, inner diameter 13 mm, inner diameter) is attached to each muff.
  • a water-absorbent sheet (10 mm, length 290 mm) was fixed parallel to the ground, and a water-absorbent sheet was sandwiched together with a plastic bag with a large clip (sandwich opening 150 mm) attached to a SUS pipe, and vibrated for 1 minute with a vibration width of 3 mm.
  • the water-absorbent sheet together with the plastic bag was removed from the large clip of the electromagnetic sieve shaker, and the weight of the particulate water-absorbent that fell into the plastic bag from the water-absorbent sheet was measured.
  • Table 2 shows the configurations and evaluation results of the water-absorbent sheets of Examples 11 to 18.
  • Example B In the following examples, a single layer in which only one layer of the first base material is laminated on the water absorbing layer (region containing the particulate water absorbing agent) is laminated on the second base material.
  • a form and a two-layered form in which a laminate in which a first base material is laminated on a water absorbing layer (a region containing a particulate water absorbing agent) is laminated in two layers on a second base material.
  • the term "upper nonwoven fabric” means a first substrate having a liquid-absorbing surface that directly absorbs the liquid
  • the term "lower nonwoven fabric” is used.
  • the base material other than the first base material having a liquid absorbing surface that directly absorbs the liquid in the two-layer form is an intermediate base material, and is referred to here as an "intermediate non-woven fabric".
  • Acrylic acid production example Commercially available acrylic acid (acrylic acid dimer 2000 ppm, acetic acid 500 ppm, propionic acid 500 ppm, p-methoxyphenol 200 ppm) is supplied to the bottom of a high boiling point impurity separation tower having 50 steps of a dam-free perforated plate, and the reflux ratio is set to 1.
  • Acrylic acid (acrylic acid dimer 20 ppm, acetic acid 50 ppm, propionic acid 50 ppm, furfural 1 ppm or less) by distilling as, after removing dimer (acrylic acid dimer) composed of maleic acid and acrylic acid, and further performing crystallization. , Protoanemonin (1 ppm or less) was obtained, and 50 ppm of p-methoxyphenol was further added after distillation.
  • the above reaction solution was supplied to a reactor formed by attaching a lid to a stainless steel double-armed kneader with an internal volume of 10 L having two sigma type blades, and the system was nitrogenized while keeping the reaction solution at 30 ° C. Gas replacement was performed to remove dissolved oxygen in the reaction solution. Subsequently, 28.66 g of a 10 mass% aqueous solution of sodium persulfate and 35.28 g of a 1 mass% aqueous solution of L-ascorbic acid were added while stirring the reaction solution, and the polymerization started after about 1 minute.
  • This subdivided hydrogel polymer was spread on a wire mesh of 50 mesh (mesh size 300 ⁇ m) and dried with hot air at 175 ° C. for 65 minutes.
  • the dried product was pulverized using a roll mill, further classified and blended with a wire mesh having a mesh size of 600 ⁇ m to obtain an amorphous crushed water-absorbent resin (1-1) having an average particle diameter of 350 ⁇ m.
  • a surface cross-linking agent aqueous solution containing 0.03 parts by mass of ethylene glycol diglycidyl ether, 1.0 part by mass of propylene glycol, and 3.0 parts by mass of water in 100 parts by mass of the obtained water-absorbent resin (1-1) 4.03. The parts by mass were spray-mixed.
  • the above mixture was heat-treated at a heat medium temperature of 100 ° C. for 40 minutes using a paddle-type mixing heat treatment machine to obtain a surface-crosslinked water-absorbent resin (1-2). 3.0 parts by mass of water was spray-mixed with 100 parts by mass of the obtained surface-crosslinked water-absorbent resin (1-2) and cured at 60 ° C. for 1 hour in a closed container, and then the opening was 710 ⁇ m.
  • a water-absorbent resin (1-3) was obtained by passing through a sieve.
  • Aerosil 90G hydrophilic amorphous silica, manufactured by Nippon Aerosil Co., Ltd.
  • ⁇ CRC Unpressurized Water Absorption Magnification
  • ERT441.2-02 0.2 g of the particulate water absorbent (weight before water absorption) is placed in a non-woven bag, and then immersed in a large excess of 0.9 mass% sodium chloride aqueous solution for 30 minutes for free swelling, and then a centrifuge (centrifugal separator). The weight of the particulate water-absorbing agent after draining with 250G) is measured.
  • the water absorption ratio (unit: g / g) is determined by "(weight of the particulate water absorbent after water absorption-weight of the particulate water absorbent before water absorption) / (weight of the particulate water absorbent before water absorption) x 100".
  • the CRC of each particulate water absorbent is shown in Tables 4 and 6.
  • the surface tension means the surface tension of the aqueous solution when the particulate water absorbent is dispersed in the 0.90 mass% sodium chloride aqueous solution.
  • a plate method using a platinum plate is adopted, and the plate is sufficiently washed with deionized water before each measurement and heated and washed with a gas burner before use.
  • Patterns 1 to 6 were prepared in order to spray the particulate water absorbing agent on the non-woven fabric in a streak pattern.
  • the patterns 1 to 6 are particles such that a region in which the particulate water-absorbing agent is present and a region in which the particulate water-absorbing agent is not present are formed linearly along the longitudinal direction on a paper having a length of 14 cm and a width of 44 cm. A hole was made in the area where the water absorbent was present.
  • the outer circumference 2 cm thereof shall be a frame, and the paper shall not be cut (that is, the paper pattern shall be a region in which the particulate water absorbing agent is present in the region excluding the frame, in order from the end in the lateral direction. Cut out the part to make a hole).
  • the shapes (S-1) to (S-6) formed by the patterns 1 to 6 will be described with reference to FIGS. 15 (a) to 15 (c) and FIGS. 16 (a) to 16 (c).
  • 15 (a) to 15 (c) and 16 (a) to 16 (c) are schematic cross-sectional views of a single-layer water-absorbent sheet cut along the lateral direction.
  • the shapes (S-1) to (S-6) have a region containing the particulate water absorbing agent 14 and a gap 15 so as to be symmetrical with respect to the central portion of the water absorbing sheet in the lateral direction. It is formed. Therefore, the region ratio between the "particulate water absorbing agent 14" and the "gap 15" shown below may be from either the left or right along the lateral direction.
  • FIG. 15 (a) is a (S-1) shape formed by the paper pattern 1.
  • the shape of (S-1) is as follows: "Particular water absorbing agent 14:15 mm, gap 15:25 mm, particulate water absorbing agent 14:20 mm, gap 15" between the first base material 11 and the second base material 13. : 25 mm, particulate water absorbing agent 14:15 mm ”are formed in order along the lateral direction.
  • FIG. 15 (b) is a (S-2) shape formed by the paper pattern 2.
  • the shape of (S-2) is as follows: "Particular water absorbing agent 14:20 mm, gap 15:20 mm, particulate water absorbing agent 14:20 mm, gap 15" between the first base material 11 and the second base material 13. : 20 mm, particulate water absorbing agent 14:20 mm ”are formed in order along the lateral direction.
  • FIG. 15 (c) is a (S-3) shape formed by the paper pattern 3.
  • the shape of (S-3) is as follows: "Particular water absorbing agent 14:10 mm, gap 15:35 mm, particulate water absorbing agent 14:10 mm, gap 15" between the first base material 11 and the second base material 13. : 35 mm, particulate water absorbent 14:10 mm ”are formed in order along the lateral direction.
  • FIG. 16A is a (S-4) shape formed by the paper pattern 4.
  • the shape of (S-4) is as follows: "Particular water absorbing agent 14:25 mm, gap 15:10 mm, particulate water absorbing agent 14:30 mm, gap 15" between the first base material 11 and the second base material 13. : 10 mm, particulate water absorbing agent 14:25 mm ”are formed in order along the lateral direction.
  • FIG. 16B is a (S-5) shape formed by the paper pattern 5.
  • the shape of (S-5) is such that between the first base material 11 and the second base material 13, "particulate water absorbing agent 14: 17.5 mm, gap 15:10 mm, particulate water absorbing agent 14:17. "5 mm, gap 15:10 mm, particulate water absorbing agent 14: 17.5 mm, gap 15:10 mm, particulate water absorbing agent 14: 17.5 mm" are formed in this order along the lateral direction.
  • FIG. 16 (c) is a (S-6) shape formed by the paper pattern 6.
  • the shape of (S-6) is as follows: "Particular water absorbing agent 14:10 mm, gap 15: 5 mm, particulate water absorbing agent 14:10 mm, gap 15" between the first base material 11 and the second base material 13.
  • Pattern 1 (see FIG. 15 (a)) is placed on non-woven fabric A (made by the air-through method, which is mainly composed of olefin and has a thickness of 1.4 mm, which corresponds to an intermediate non-woven fabric) cut into a length of 10 cm and a width of 40 cm. It was.
  • the pattern 1 has three rectangular holes, and the positions are adjusted so that the non-woven fabric A under the pattern 1 can be seen as much as possible from the holes. Calculate the area ratio of each hole to the total area of all the holes of the pattern 1, and divide 4.5 g (spray amount: 112.5 g / m 2 ) of the particulate water absorbent (1) by the area ratio of each hole.
  • the non-woven fabric A Separately from the non-woven fabric A, the non-woven fabric A cut into a length of 10 cm and a width of 40 cm (the same as the non-woven fabric A (thickness 1.4 mm). Hereinafter referred to as non-woven fabric A2.
  • First base material upper non-woven fabric
  • an adhesive containing styrene butadiene rubber spray glue 77, manufactured by 3M Japan Co., Ltd.
  • Pattern 1 (see FIG. 15A) was placed on the surface of the non-woven fabric A on the side not facing the particulate water absorbing agent (1). The position was adjusted so that the non-woven fabric A under the pattern 1 could be seen to the maximum through the three rectangular holes of the pattern 1. Calculate the area ratio of each hole to the total area of all the holes of the paper pattern 1, measure 4.5 g of the particulate water absorbent (1) separately by the area ratio of each hole, and measure the non-woven fabric A that can be seen from each hole. was sprayed evenly.
  • the paper pattern 1 When a part of the particulate water absorbing agent (1) is sprayed on the paper pattern, the paper pattern 1 is tilted toward the non-woven fabric A on which the particulate water absorbing agent (1) is sprayed, and the particulate water absorbing agent is applied to the paper pattern 1. I dropped it in the hole. Then, the paper pattern 1 was removed from the non-woven fabric A.
  • Non-woven fabric E with a length of 10 cm and a width of 40 cm (made by the airlaid method.
  • the main component is pulp fiber. Thickness 0.4 mm. Metsuke amount: 47 g / m 2.
  • the second base material lower non-woven fabric.
  • the non-woven fabric F (made by the spunbond method) obtained by cutting the intermediate sheet X into a length of 24 cm and a width of 40 cm.
  • the main component is olefin, the thickness is 0.1 mm, the basis weight: 13 g / m 2, and the bulk density: 0. .15 g / cm 3 (corresponding to a wrapping sheet) was wrapped to obtain a water-absorbent sheet (1).
  • Non-woven fabric F (corresponding to a wrapping sheet) cut into a length of 24 cm and a width of 40 cm is laid, and non-woven fabric A (corresponding to a first base material) cut into a length of 10 cm and a width of 40 cm is placed on the non-woven fabric F.
  • a pattern 1 (see FIG. 15 (a)) was placed on the surface. The position was adjusted so that the non-woven fabric A under the pattern 1 could be seen to the maximum through the three rectangular holes of the pattern 1. Calculate the area ratio of each hole to the total area of all the holes of the paper pattern 1, and measure 9.0 g (spray amount: 225 g / m 2 ) of the particulate water absorbent (1) by dividing it by the area ratio of each hole.
  • an adhesive containing styrene-butadiene rubber (spray glue 77, manufactured by 3M Japan Co., Ltd.) is uniformly sprayed (sprayed) on a non-woven fabric E (corresponding to the second base material) having a length of 10 cm and a width of 40 cm. Amount: 17.5 to 21.5 g / m), so that the surface of the non-woven fabric A sprayed with the particulate water absorbent (1) and the surface sprayed with the adhesive of the non-woven fabric E face each other (contact each other). ) Stacking and pressure crimping to obtain an intermediate sheet Y.
  • styrene-butadiene rubber spray glue 77, manufactured by 3M Japan Co., Ltd.
  • Example 3 A water-absorbent sheet (3) was obtained in the same manner as in Example 2 except that the air-through nonwoven fabric G having a thickness of 0.7 mm was used instead of the air-through nonwoven fabric A.
  • Example 4 A water-absorbent sheet (4) was obtained in the same manner as in Example 2 except that the paper pattern 2 (see FIG. 15B) was used instead of the paper pattern 1.
  • Example 5 A water-absorbent sheet (5) was obtained in the same manner as in Example 2 except that the pattern 3 (see FIG. 15 (c)) was used instead of the pattern 1.
  • Example 6 A water-absorbent sheet (6) was obtained in the same manner as in Example 2 except that the paper pattern 4 (see FIG. 16A) was used instead of the paper pattern 1.
  • Example 7 A water-absorbent sheet (7) was obtained in the same manner as in Example 2 except that the pattern 5 (see FIG. 16B) was used instead of the pattern 1.
  • Example 8 A water-absorbent sheet (8) was obtained in the same manner as in Example 2 except that the paper pattern 6 (see FIG. 16C) was used instead of the paper pattern 1.
  • Example 9 The water-absorbent sheet (9) was prepared in the same manner as in Example 2 except that the non-woven fabric B (produced by the air-through method. The main component was olefin and the thickness was 2.0 mm) was used instead of the non-woven fabric A. Obtained.
  • Example 10 The water-absorbent sheet (10) was prepared in the same manner as in Example 2 except that the non-woven fabric C (manufactured by the air-through method. The main component was olefin and the thickness was 1.5 mm) was used instead of the non-woven fabric A. Obtained.
  • an adhesive containing styrene-butadiene rubber (Spray Glue 77, manufactured by 3M Japan Ltd.) is uniformly sprayed on a non-woven fabric E (corresponding to the first base material) having a length of 10 cm and a width of 40 cm. (Spray amount: 17.5 to 21.5 g / m), the surface on which the particulate water absorbing agent (1) of the non-woven fabric A is sprayed and the surface on which the adhesive of the non-woven fabric E is sprayed face each other (contact). (Like) and pressure-bonded.
  • non-woven fabric E2 Apart from the non-woven fabric E, 0.7 to 0.9 g of the adhesive is uniformly applied to the non-woven fabric E having a length of 10 cm and a width of 40 cm (hereinafter referred to as non-woven fabric E2, which corresponds to a second base material).
  • the surface on which the particulate water absorbing agent (1) of the non-woven fabric A is sprayed and the surface on which the adhesive of the non-woven fabric E2 is sprayed are overlapped so as to face each other (contact), and pressure-bonded to form an intermediate sheet. I got Z. Finally, the intermediate sheet Z was wrapped with the non-woven fabric F and pressure-bonded to obtain a water-absorbent sheet (11).
  • Example 2 A water-absorbent sheet (12) was obtained in the same manner as in Example 1 except that the particulate water-absorbent agent (1) was uniformly sprayed on the entire surface of the non-woven fabric A without using the paper pattern 1.
  • Example 3 A water-absorbent sheet (13) was obtained in the same manner as in Example 1 except that the non-woven fabric E was used instead of the non-woven fabric A2. As the intermediate non-woven fabric, the non-woven fabric A is used.
  • a water-absorbent sheet (14) was obtained in the same manner as in Example 2 except that the non-woven fabric E was used instead of the non-woven fabric A.
  • the non-woven fabrics A to C and G used in this example were all water permeable sheets.
  • the non-woven fabric for measuring the elongation was cut into a rectangle having a long side of 100 mm and a short side of 30 mm. At this time, the long side is in the width direction of the non-woven fabric roll, and the short side is in the winding length direction of the non-woven fabric roll.
  • the non-woven fabric having a length (short side) of 100 mm and a width (long side) of 400 mm used for the water-absorbent sheet in this embodiment the length (short side) is the width direction of the non-woven fabric roll and the width (long side) is the width direction.
  • the winding length direction of the non-woven fabric roll is used. As shown in FIG.
  • reference lines were drawn at positions 5 mm from both ends of the cut non-woven fabric for measuring the elongation rate so as to be parallel to the short sides. Each was sandwiched between double clips so as to overlap the reference line (FIG. 17 (b)).
  • the double clip used had a claw length of 30 mm or more.
  • a weight was attached to one of the double clips, and the total weight of the double clip to which the weight was attached and the weight was 110 g. In a room temperature atmosphere, a double clip without a weight was held, and the weight attached to the other double clip was lifted so as to float in the air, and the non-woven fabric was kept stretched by the weight of the double clip and the weight for 20 seconds.
  • Dial thickness gauge Measured using a large type (thickness measuring instrument) (manufactured by Ozaki Seisakusho Co., Ltd., model number: JB, stylus: anvil top and bottom ⁇ 50 mm). The number of measurement points was 5 times at different points, and the measured value was an average value of 5 points. When measuring the thickness, the thickness was measured by slowly releasing the hand from the handle so that pressure was not applied to the non-woven fabric as much as possible.
  • ⁇ Calculation method of bulk density of non-woven fabric> The weight of the non-woven fabric cut into a size of 10 cm or more in length and 40 cm or more in width was measured.
  • the volume of the non-woven fabric was calculated by multiplying the vertical and horizontal lengths of the non-woven fabric and the thickness measured from ⁇ thickness measurement>, respectively, and the bulk density was calculated by dividing the weight of the non-woven fabric by the volume of the non-woven fabric.
  • the mesh of the sieve and the flat surface were sufficiently separated from each other so that the non-woven fabric and the physiological saline passing through the mesh did not come into contact with the mesh.
  • the non-woven fabric absorbed the physiological saline and the diffusion of the liquid was completed, the area where the physiological saline was diffused was measured.
  • a JIS standard sieve (The IIDA TESTING SIEVE: inner diameter 80 mm; JIS Z8801-1 (2000)) having a mesh 32 with an opening of 850 ⁇ m, or a non-woven fabric cut to a diameter of 80 mm in a sieve 31 corresponding to the JIS standard sieve (No. 1).
  • the base material 11) of No. 1 was installed as shown in FIG. 5, and the periphery was fastened with a tape 33 (at least a diameter of 75 mm or more secures an area through which particles can permeate).
  • the non-woven fabric first base material 11
  • one taken out from the water-absorbent sheet by the method described later may be used.
  • the particulate water absorbent 14 (weight average particle diameter: 367 ⁇ m, particle size distribution: 850 ⁇ m to 600 ⁇ m is 6.1% 600 ⁇ m).
  • ⁇ 500 ⁇ m is 14.5% 500 ⁇ m ⁇ 300 ⁇ m is 50% 300 ⁇ m ⁇ 150 ⁇ m is 27.6% 150 ⁇ m ⁇ 45 ⁇ m is 1.9% 45 ⁇ m or less 0.1%) 10.0 g is added and a low tap type sieve shaker (stock) Using an ES-65 type sieve shaker manufactured by Iida Seisakusho Co., Ltd .; rotation speed 230 rpm, impact number 130 rpm), the particles were shaken for 5 minutes under the conditions of room temperature (20 to 25 ° C.) and relative humidity of 50% RH.
  • the particulate water absorbing agent 14 (that is, particles existing in the portion 31a below the mesh 32 of the sieve 31) has passed through the non-woven fabric (first base material 11) and the mesh 32 of the sieve 31 corresponding to the JIS standard sieve.
  • the mass (W (g)) of the water absorbing agent 14) was measured, and the transmittance of the particulate water absorbing agent 14 was calculated according to the following formula (i). The measurement was performed twice, and the average value was calculated.
  • the particulate water absorbent used for measuring the transmittance is a particulate water absorbent containing 90% by weight or more of the particulate water absorbent having a weight average particle diameter of 300 to 450 ⁇ m and a particle size distribution of 850 ⁇ m to 150 ⁇ m. Therefore, the transmittance of the particulate water-absorbing agent for the first base material calculated in this example also corresponds to the transmittance of the specific particulate water-absorbing agent for the first base material.
  • the fibers of the non-woven fabric and the structural thickness can be taken out without changing, and the transmittance can be measured accurately.
  • Various means can be considered for cooling the water-absorbent sheet, such as putting it in a constant temperature bath at -10 ° C or lower for a certain period of time, spraying a cooling spray, or spraying liquid nitrogen, but without changing the fiber, structure, or thickness of the non-woven fabric.
  • it is not particularly limited as long as it is carried out under the condition that the particulate water absorbing agent contained in the water absorbing sheet does not absorb moisture.
  • the water content is adjusted to 10% by mass or less, preferably 5 ⁇ 2% by mass, and the above-mentioned transmittance and various specifications specified in the present application. Physical properties may be measured.
  • the drying conditions for adjusting the water content are not particularly limited as long as the water-absorbent resin (particulate water-absorbing agent) is not decomposed or modified, but vacuum drying is preferable.
  • the content ratio (%) of the particulate water absorbing agent in the first base material was calculated by the following formula.
  • Content ratio (%) of particulate water-absorbing agent in the first base material particle-like water-absorbing agent area (I) in the first base material / total particle-like water-absorbing agent area (II) ⁇ 100 That is, the content ratio of the particulate water absorbing agent in the first base material is represented by the area% with respect to the total area of the particulate water absorbing agent.
  • the particulate water absorbent is less than a few percent even if it is present on the liquid absorbing surface that directly absorbs the liquid of the first base material (the surface on the side where the liquid to be absorbed by the upper non-woven fabric is introduced). Therefore, it can be considered that it does not exist.
  • the content ratio of the particulate water absorbing agent in the first base material was 5% or more with respect to the particulate water absorbing agent contained in the entire water absorbing sheet.
  • the weight 44 was removed, and the first reversion amount (g) was measured from the weight increment of the filter paper 43. 1 minute after removing the weight 44, the same operation (adding the liquid ⁇ 10 minutes after adding the liquid, placing the filter paper 43 and the weight 44 (1200 g), holding for 1 minute ⁇ holding after 1 minute ⁇ removing the weight, reversing (Measurement of amount) was repeated, and the second reversion amount (g) and the third reversion amount (g) were measured. Tables 4 and 6 show the total of the measured reversion amounts from the first to the third.
  • La is the thickness from the liquid absorbing surface of the upper nonwoven fabric (liquid absorbing surface of the first substrate) to the surface of the lower nonwoven fabric (second substrate) on the water absorbing layer side in the gap
  • Lb is the particulate water absorption. It is the thickness from the liquid-absorbing surface of the upper non-woven fabric (the liquid-absorbing surface of the first base material) to the surface of the lower non-woven fabric (the second base material) on the water-absorbing layer side in the region containing the agent.
  • the thickness from the liquid-absorbing surface of the upper non-woven fabric to the surface of the lower non-woven fabric on the water-absorbing layer side in the gap under the upper non-woven fabric is La
  • the thickness of the upper non-woven fabric in the region under the upper non-woven fabric containing the particulate water-absorbing agent is defined as La
  • the thickness from the liquid absorbing surface to the surface of the lower nonwoven fabric on the water absorbing layer side was defined as Lb.
  • the upper non-woven fabric and the lower non-woven fabric are mainly present.
  • X Regions containing a small amount of gaps and parallel particulate water absorbents are connected (not separated by gaps). (That is, the particulate water-absorbing agent enters the region that was the gap, and the proportion of the base material that holds the water-absorbing layer is reduced).
  • Tables 3 to 6 below show the configurations of the water-absorbent sheets produced in Examples 1 to 10 and Comparative Examples 1 to 4, the evaluation results of the physical properties of the base material used in each water-absorbent sheet, and the evaluation results of the water-absorbent sheet. Is shown.
  • SAP means a particulate water absorbing agent.
  • the SAP arrangement region (%) in Tables 3 and 5 is the area ratio of the region containing the particulate water absorbent to the total area of the base material on which the particulate water absorbent is arranged in the plane direction of the upper non-woven fabric.
  • the SAP non-arranged region (%) is the area ratio of the region (that is, the gap) not containing the particulate water-absorbing agent to the total area of the base material on which the particulate water-absorbing agent is arranged in the plane direction of the upper non-woven fabric.
  • the base material on which the particulate water absorbing agent is arranged means a base material on which the particulate water absorbing agent is sprayed.
  • the upper non-woven fabric, the intermediate non-woven fabric, and the lower non-woven fabric have the same size.
  • the water-absorbent sheets of Examples 2 to 10 had higher shape retention and a significantly smaller amount of reversion as compared with the water-absorbent sheets of Comparative Examples 1 to 4. That is, it was confirmed that in the single-layer and two-layer water-absorbent sheets, the amount of reversion can be reduced and the shape-retaining property is high by providing a gap in the water-absorbent layer by using an upper non-woven fabric having elasticity. ..
  • the amount of reversion tends to be larger in the two-layer form than in the single-layer form.
  • the amount of the particulate water-absorbing agent for the two-layered upper-layer non-woven fabric that is, the amount of the particulate water-absorbing agent located between the upper nonwoven fabric and the intermediate nonwoven fabric
  • the particulate water-absorbing agent for the single-layered upper-layer nonwoven fabric is the particulate water-absorbing agent for the single-layered upper-layer nonwoven fabric. (That is, the amount of the particulate water-absorbing agent located between the upper non-woven fabric and the lower non-woven fabric) may be one of the factors. Therefore, it is difficult to make a general comparison of the difference in the effect of reducing the amount of reversion between the single-layer form and the two-layer form.
  • the water-absorbent sheet of the second invention has a first base material, a second base material, and a water-absorbent layer located between the first base material and the second base material.
  • the water-absorbing layer contains a particulate water-absorbing agent, and a region containing the particulate water-absorbing agent is arranged with a gap substantially free of the particulate water-absorbing agent.
  • the surface of the first base material forms a liquid absorbing surface that directly absorbs the liquid, and the first base material has an elongation rate of 10% or more.
  • Water-absorbent resin (SAP / Super Absorbent polymer) is a water-swellable water-insoluble polymer gelling agent, which is a sanitary material such as disposable diapers, sanitary napkins and incontinence products for adults, and a soil water-retaining agent for agriculture and gardening. , Industrial water-stopping agent, etc., are used for various purposes.
  • absorbent articles are generally manufactured in a paper diaper manufacturing factory as an absorber in which a water-absorbent resin and a fiber material are mixed and individually molded for each absorbent article, and have various shapes depending on the purpose. (For example, it is processed into an hourglass type, a diaper type, an oval type, etc. when viewed on a flat surface). Since these absorbents are individually molded, they can be processed into any shape, and the amount of fibers and water-absorbent resin can be easily adjusted for each absorbent article, which is the mainstream of the current paper diapers.
  • the water-absorbent sheet has a structure in which water-absorbent resin particles are sandwiched and fixed between the upper and lower sheets (particularly a non-woven fabric sheet), and after usually producing a long continuous sheet, the long continuous sheet is cut to have a width of about 10 cm. Make a rectangle with a length of several tens of centimeters and incorporate it into a paper diaper (for example, International Publication No. 2010/143635).
  • paper diapers made of water-absorbent sheets have a short history, and there have been few developments of water-absorbent resins suitable for water-absorbent sheets or proposals for parameters.
  • the conventional water-absorbent resin for disposable diapers is used as it is for the water-absorbent sheet.
  • the water-absorbent resin particles swell to weaken the fixation of the water-absorbent resin particles to the upper and lower sheets, and the water-absorbent resin particles move in the sheet. It may end up. Then, the water-absorbent resin particles are biased in the sheet, and the shape of the water-absorbent sheet is deformed. In this case, the liquid absorbency of the water-absorbent sheet becomes uneven, which causes leakage. In some cases, the water-absorbent resin particles may fall off from the inside of the sheet to the outside.
  • the present invention has been made in view of the above circumstances, and even if the liquid is intermittently introduced a plurality of times (particularly three or more times), the liquid discharge from the water-absorbent sheet due to reversion is significantly reduced. It is an object of the present invention to provide a novel water-absorbent sheet capable of maintaining the sheet shape (highly shape-retaining property of the sheet) even after liquid absorption.
  • the present inventors have made extensive studies in order to solve the above problems. As a result, it is a water-absorbent sheet having a first base material, a second base material, a water-absorbing layer located between the first base material and the second base material.
  • the water-absorbing layer contains the particulate water-absorbing agent, and the region containing the particulate water-absorbing agent is arranged with a gap substantially free of the particulate water-absorbing agent, and the surface of the first base material is formed.
  • a water-absorbent sheet which forms a water-absorbing surface that directly absorbs the liquid and has an elongation rate of 10% or more for the first base material.
  • the water-absorbent sheet in the water-absorbent sheet according to another embodiment of the present invention, only the laminate in which the first base material is laminated on the water-absorbent layer is on the second base material. , Laminated.
  • the water-absorbent sheet according to another embodiment of the present invention includes a laminated body in which the first base material is laminated on the water-absorbent layer and an intermediate base material on the water-absorbent layer.
  • the laminated structure is laminated on the second base material.
  • FIG. 18 is a schematic view showing a cross section of a water-absorbent sheet according to the first embodiment of the present invention.
  • FIG. 19 is a schematic view showing a cross section of a water-absorbent sheet according to a second embodiment of the present invention.
  • Fig. 20 is a schematic view showing a cross section of the water-absorbent sheet for explaining the morphology of the particulate water-absorbent and the gap in the water-absorbent sheet produced in the example.
  • FIG. 21 is a schematic view showing a cross section of the water-absorbent sheet for explaining the morphology of the particulate water-absorbent and the gap in the water-absorbent sheet produced in the example.
  • FIG. 22 It is a schematic diagram explaining a method of measuring the elongation rate of a non-woven fabric.
  • FIG. 23 is a schematic diagram illustrating a method of measuring the transmittance of a particulate water absorbing agent with respect to a non-woven fabric.
  • FIG. 24 It is a plan view and a right side view showing a sample used for evaluating the amount of reversion, and is a view showing how the water-absorbent sheet produced in the example is wrapped with a liquid-impermeable sheet.
  • FIG. 25 It is a plan view and a front view of the liquid injection cylinder used for evaluating the amount of reversion.
  • FIG. 26 is a front view showing a state in which a liquid injection cylinder is placed on the water-absorbent sheet used in the embodiment of the present application.
  • FIG. 27 It is a front view showing a state in which an aqueous sodium chloride solution is poured into a water-absorbent sheet from a liquid injection cylinder using a funnel.
  • the water-absorbent sheet of the present invention has a first base material, a second base material, and a water-absorbent layer located between the first base material and the second base material.
  • the water-absorbing layer contains a particulate water-absorbing agent, and a region containing the particulate water-absorbing agent is arranged with a gap substantially free of the particulate water-absorbing agent.
  • the surface of the base material forms a water-absorbing surface that directly absorbs the liquid, and the first base material has an elongation rate of 10% or more.
  • the liquid discharge from the water-absorbent sheet due to reversion can be significantly reduced. Moreover, it has high shape retention after absorbing liquid.
  • the elongation rate of the first base material forming the liquid-absorbing surface that directly absorbs the liquid is 10% or more. That is, the first base material has elasticity. A liquid absorbing surface that directly absorbs the liquid is formed on the surface of the first stretchable base material.
  • the “liquid absorbing surface” means the surface of the base material on the side that absorbs the liquid, that is, the surface on the side where the liquid is introduced. Further, in the present specification, “directly” does not include a form in which a liquid that has permeated another base material or the like is sequentially absorbed. In the present specification, even when the wrapping sheet described later is arranged on the surface of the first base material, the surface of the first base material forms a liquid absorbing surface that directly absorbs the liquid. Included.
  • the water-absorbent sheet absorbs water located between the first base material, the second base material, the first base material, and the second base material.
  • the water-absorbing layer is arranged. Not considered to be done. It is assumed that the cause of the movement is, for example, vibration generated when the water-absorbent sheet is the final product and is transported or transported.
  • the particulate water absorbing agent is intentionally sprayed or arranged on the first base material, it is not in the category of this embodiment.
  • the present inventors have a conventional water-absorbing sheet (for example, a water-absorbing sheet located between a first base material and a second base material, such as the water-absorbing sheet described in Japanese Patent Application Publication No. 105380752).
  • a conventional water-absorbing sheet for example, a water-absorbing sheet located between a first base material and a second base material, such as the water-absorbing sheet described in Japanese Patent Application Publication No. 105380752.
  • the water-absorbent sheet provided with a guide groove (corresponding to a gap) in the layer, in the measurement of the amount of reversion under specific conditions (also referred to as "specific return amount evaluation" in the present specification) in the embodiment of the present application, reversion is performed. It was found that the shape retention was poor even if the amount could be reduced.
  • the gap existing between the regions containing the particulate water-absorbing agent functions as a liquid passage when the liquid is introduced from the first base material to the water-absorbing layer when the liquid is introduced. can do. That is, due to the existence of the liquid passage, the liquid introduced from the liquid absorption surface does not stay on the liquid absorption surface (furthermore, the introduced liquid does not stay locally) and has a water absorption function.
  • the liquid can be efficiently delivered to the lower water absorption layer.
  • the liquid for example, urine
  • the liquid for example, urine
  • the liquid introduced into the gap has no particulate water-absorbing agent that hinders the passage of the liquid with respect to the region containing the particulate water-absorbing agent, and is absorbed slowly by the particulate water-absorbing agent, so that it is easy to diffuse.
  • the amount of liquid absorbed by the particulate water-absorbing agent at the site where the liquid was introduced is large, and the amount of liquid absorbed by the particulate water-absorbing agent at the site away from the liquid-introduced part is small. Prevents the birth of.
  • the particulate water-absorbing agent absorbs the liquid and swells
  • the volume of the region containing the particulate water-absorbing agent increases, so that the swelled particulate water-absorbing agent invades into the region that was the gap.
  • the gap is reduced.
  • the liquid absorption capacity gradually decreases as the gap decreases.
  • the particulate water-absorbing agent tends to partially saturate and swell, so that the first base material absorbs the liquid.
  • the amount of water returning to the liquid level will gradually increase. As a result, the retreated liquid rises to the skin (contacts the skin), causing discomfort.
  • the swelling of the particulate water-absorbing agent causes the first base material and / Or the fixation of the particulate water-absorbing agent to the second substrate may be weakened, and the particulate water-absorbing agent may move in the water-absorbing layer. Then, the particulate water-absorbing agent is biased in the water-absorbing layer, and the shape of the water-absorbing sheet collapses (shape retention is lowered).
  • the water-absorbent sheet of the present invention can buffer the increase in the volume of the region containing the particulate water-absorbent because the first base material has elasticity. That is, when the particulate water absorbing agent swells, the first base material expands in response to the swelling, so that the decrease in the gap can be suppressed, and thus the shape of the gap can be maintained. As a result, even if the liquid is introduced a plurality of times intermittently, the amount of reversion can be reduced without reducing the diffusion ability of the liquid.
  • the fixation of the particulate water absorbing agent to the first base material and / or the second base material is not weakened.
  • the first base material in contact with the particulate water-absorbing agent extends into a shape that follows the swollen particulate water-absorbing agent due to the swelling of the particulate water-absorbing agent.
  • the first base material and the particulate water absorbing agent are entangled with each other, and the particulate water absorbing agent is more strongly held between the first base material and the second base material.
  • the water-absorbent sheet of the present invention can suppress the movement of the particulate water-absorbent agent from the region containing the particulate water-absorbent agent in the water-absorbent layer, and can maintain the shape of the water-absorbent sheet. , High shape retention.
  • the laminate in which the first base material is laminated on the water absorption layer and the structure in which the intermediate base material is laminated on the water absorption layer are the second base materials.
  • a multi-layered (two-layered) water-absorbing sheet, which is laminated (with the water-absorbing layer located on the side of the second base material), and the first base material are laminated on the water-absorbing layer.
  • the single-layer water-absorbent sheet in which only one layer is laminated on the second base material, the single-layer water-absorbent sheet has a greater effect of reducing reversion.
  • the reason is unknown, in other words, it can be said to be an unexpected effect for those skilled in the art.
  • the water-absorbing function in the water-absorbing layer is mainly carried out by the water-absorbing agent (particulate water-absorbing agent).
  • the role of the water-absorbing agent becomes even more important.
  • the first base material has elasticity, the shape of the gap provided between the water absorbing layer and the region containing the particulate water absorbing agent can be maintained, and the water absorbing agent can be maintained. It is difficult for the liquid once introduced into the first base material to return to the water absorption surface of the first base material.
  • the shape of the water-absorbent sheet can be maintained (that is, the shape retention is high), and the "specific return amount evaluation" can be made excellent.
  • a water-absorbent sheet or an absorbent article designed to suppress the amount of reversion under general conditions does not always give excellent results in the "specific return amount evaluation" of the present application.
  • the water-absorbent sheet according to the embodiment of the present invention is an absorbent article (for example, an absorbent article used during a time when an infant whose bladder is still small is actively moving around, such as in the daytime, when he / she begins to learn to run. It is suitable as a diaper), but of course the usage pattern is not limited to this.
  • the mechanisms and the like described herein do not limit the technical scope of the claims of the present application.
  • the water-absorbent sheet according to the first embodiment of the present invention is formed by laminating only a laminate in which the first base material is laminated on the water-absorbent layer on the second base material. That is, in the first embodiment, the water absorption layer has a structure sandwiched between the first base material and the second base material.
  • FIG. 18 is a schematic view showing a cross section of the water-absorbent sheet 10 according to the first embodiment of the present invention.
  • FIG. 18 shows three forms ((a) to (c)) of the water-absorbent sheet 10.
  • the arrows indicate the direction in which the absorbed liquid is introduced.
  • the first base material 11 is located on the side where the liquid absorbed by the water absorbing layer 12 (the liquid to be absorbed) is introduced. That is, the first base material is arranged on the liquid discharge side (for example, the skin side in the case of paper diapers).
  • the water absorption layer 12 is arranged between the first base material 11 and the second base material 13. That is, the laminate 18 in which the first base material 11 is laminated on the water absorption layer 12 is laminated on the second base material 13.
  • the water absorbing layer 12 contains the particulate water absorbing agent 14.
  • the water absorption layer 12 shows a state in which the particulate water absorption agent 14 is present between the first base material 11 and the second base material 13. A part of the particulate water absorbing agent 14 may be detached from each of the base materials 11 and 13.
  • the particulate water-absorbing agent 14 (the region containing the particulate water-absorbing agent 14) is arranged with a gap 15 that does not substantially contain the particulate water-absorbing agent 14. Therefore, the water-absorbing "layer” does not mean only a continuum such as a sheet, but if it exists between the first base material 11 and the second base material 13 with a constant thickness and length.
  • the water absorption layer 12 may be intermittently present between the first base material 11 and the second base material 13 with a constant thickness and length.
  • an adhesive may be used.
  • FIG. 18A the gap 15 is formed between the first base material 11 and the second base material 13, but the gap 15 in the present invention is shown in FIG. 18B. And the form of FIG. 18 (c) is also included.
  • FIG. 18B the region containing the particulate water absorbing agent 14 is separated by the contact between the first base material 11 and the second base material 13. Although the first base material and the second base material are in contact with each other, it is regarded as a gap because the liquid passage is maintained. Further, since the water absorption layer 12 is separated by the first base material 11 (in some cases, the first base material 11 and the second base material 13) entering the water absorption layer 12, the water absorption layer 12 in the present embodiment. Exists intermittently. In FIG.
  • the end portion of the first base material 11 and the end portion of the second base material 13 are overlapped so that the end portion of the water-absorbent sheet 10 becomes the first base material 11 and the second base material 11. It is closed by the base material 13 of the above. Also in this case, the first base material 11 (in some cases, the first base material 11 and the second base material 13) enters at the end portion of the water absorption layer 12, so that the end portion of the water absorption layer 12 The water absorption layer 12 does not exist.
  • the form of the water absorption layer 12 and the gap 15 is similarly applied to the second embodiment described later.
  • the particulate water absorbing agent 14 may be present in the first base material 11.
  • the particulate water absorbing agent 14 in the first base material 11 is, for example, in contact with the particulate water absorbing agent 14 that has come into contact with (or has been fixed to) the first base material 11 or the second base material 13.
  • the particulate water-absorbing agent 14 (or fixed) may be desorbed and captured in the first base material 11.
  • the content ratio of the particulate water absorbing agent 14 in the first base material 11 is the particle water absorbing agent 14 contained in the entire water absorbing sheet 10. On the other hand, it is preferably 5% or more, more preferably 10% or more, still more preferably 20% or more, and even more preferably 30% or more.
  • the upper limit is not particularly limited, but is 90% or less, 70% or less, and 50% or less in the preferred order.
  • the content ratio of the particulate water absorbing agent 14 in the first base material 11 to the particulate water absorbing agent 14 contained in the entire water absorbing sheet 10 is calculated by the method of Examples described later.
  • the region of the gap 15 does not substantially contain the particulate water absorbing agent 14.
  • Additives other than the particulate water absorbing agent 14 may be contained in the region of the gap 15.
  • the gap 15 may be formed by contacting the first base material 11 and the second base material 13 directly or via an adhesive. Since the first base material 11 has elasticity, the first base material 11 contains the particulate water absorbing agent 14 when there is a region on the second base material 13 containing the particulate water absorbing agent 14. It expands and contracts according to the area.
  • the first base material 11 has a shape that covers the region containing the particulate water absorbing agent 14 on the region containing the particulate water absorbing agent 14, and contains the particulate water absorbing agent 14 on the gap 15. After being along the upper side surface of the region, the shape is such that it sinks toward the second base material 13.
  • the ratio (Lb / La) of the thickness (Lb) from the liquid absorbing surface of the first base material 11 to the surface of the second base material on the water absorbing layer 12 side in the region containing the water absorbing agent 14 is 1.05. It is preferably as follows.
  • the shape of the region containing the particulate water absorbing agent 14 (that is, the first base material) in the portion where the first base material 11 is in contact with the particulate water absorbing agent 14
  • the particle-like water-absorbing agent 14 in contact has a shape that follows (that is, the shape of the particle-like water-absorbing agent 14 on the side in contact with the first base material 11) (that is, expands and contracts accordingly). Therefore, the first base material 11 can be brought into close contact with the particulate water absorbing agent 14 (the region containing the particulate water absorbing agent 14), whereby the first base material 11 can be brought into close contact with the particulate water absorbing agent 14 (particulate).
  • Lb / La is usually 1 or more.
  • a gap 15 is formed by providing a non-existent region of the particulate water-absorbing agent 14 on a part of the second base material 13.
  • the gap 15 (that is, the non-existent region of the particulate water absorbing agent 14) is continuously provided along one direction on the liquid absorbing surface of the first base material 11, so that the function as a liquid passing path is further enhanced.
  • the shape in which the gaps 15 are continuously provided may be, for example, linear, curved, or corrugated, but it is preferable that the gaps 15 are linearly provided in parallel.
  • the region and the gap 15 containing the particulate water-absorbing agent 14 are in one direction on the liquid-absorbing surface of the first base material 11 (the plane direction perpendicular to the direction in which the liquid is absorbed). It is preferable that it has a shape extending along the above and is arranged in parallel. That is, the regions containing the particulate water absorbing agent 14 are arranged in a streak (striped) pattern. As a result, the gaps 15 are also formed in stripes, so that the gaps 15 can be easily maintained even when the particulate water absorbing agent 14 swells, and as a result, reversion can be further reduced.
  • the "one direction” is any direction parallel to the surface direction on the liquid absorbing surface of the first base material 11, excluding the thickness direction, that is, on the liquid absorbing surface of the first base material 11. It may be in the longitudinal direction, the lateral direction, or the direction inclined with respect to these directions. From the viewpoint of the balance between the role of the gap 15 and the role of the particulate water absorbing agent 14, in the water absorbing sheet 10, the region containing the particulate water absorbing agent 14 and the gap 15 are the liquid absorbing surfaces of the first base material 11. It is preferable that the particles have a shape extending along the longitudinal direction and are arranged in parallel.
  • the ratio of the region containing the particulate water absorbing agent 14 on the surface of the first base material 11 on the water absorbing layer 12 side (hereinafter, "the region where the particulate water absorbing agent 14 exists").
  • the ratio (also referred to as “ratio") is preferably 90% or less, more preferably 80% or less, and even more preferably 75% or less in terms of area.
  • the ratio of the region containing the particulate water absorbing agent 14 on the surface of the first base material 11 on the water absorbing layer 12 side is preferably 10% or more, more preferably 20% or more in terms of area.
  • the ratio of the region containing the particulate water absorbing agent 14 on the surface of the first base material 11 on the water absorbing layer 12 side is the surface of the second base material 13 on the water absorbing layer 12 side (the particulate water absorbing agent 14 is arranged). It is the same as the ratio of the region containing the particulate water absorbing agent 14 on the surface).
  • the ratio of the region containing the particulate water absorbing agent 14 on the surface of the first base material 11 on the water absorbing layer 12 side is determined by adjusting the spraying region of the particulate water absorbing agent 14 at the time of manufacturing the water absorbing sheet 10. Can be controlled.
  • particulate water absorption on the surface of the first base material 11 on the water-absorbent layer 12 side is performed.
  • the ratio of the region containing the agent 14 can be calculated.
  • a cross section of the water-absorbent sheet 10 is photographed, and the interface between the first base material 11 or the second base material 13 and the water-absorbing layer 12 is formed into a region in which the particulate water-absorbing agent 14 is present and a particle-like shape.
  • the ratio of the region containing the particulate water absorbing agent 14 can be calculated by classifying the region into a region in which the water absorbing agent 14 does not exist, summing each region, and calculating the ratio thereof. In addition, three or more cross sections of the water absorbing sheet 10 in the short direction were photographed, the ratio of the region containing the particulate water absorbing agent 14 was calculated, and the region containing the particulate water absorbing agent 14 obtained from each cross section was calculated. The value obtained by averaging the ratios is defined as "the ratio of the region containing the particulate water absorbing agent 14".
  • the content of the particulate water absorbing agent 14 contained in the water absorbing sheet 10 is preferably 200 to 360 g / m 2 , more preferably 250 to 350 g / m 2 , and further preferably 300 to 325 g / m 2. Is.
  • the water-absorbent sheet 10 has a wrapping sheet 16.
  • the wrapping sheet 16 is a first base material for the purpose of maintaining the shape of the water absorbing sheet 10, which is a structure in which the particulate water absorbing agent 14 is supported between the first base material 11 and the second base material 13.
  • the particulate water absorbing agent 14 is the first.
  • the purpose is to prevent the particulate water absorbent 14 from coming into direct contact with the skin when it permeates through the base material 11 and migrates to the outer surface (the surface with which the liquid comes into direct contact) of the first base material 11.
  • the wrapping sheet 16 When the wrapping sheet 16 is not provided, for example, by a method of sealing by adhering the base materials 11 and 13 to each other, and by surface treatment of the first base material 11, the outer surface of the first base material 11 is formed. There is a method of suppressing the transition to. It is preferable to have the wrapping sheet 16 as a method of preventing the particulate water absorbing agent 14 from falling off from the water absorbing sheet 10 while maintaining the effect of the present application.
  • the wrapping sheet 16 is arranged on the first base material 11, and is folded so as to wrap the entire water absorbing layer 12 and the second base material 13. Therefore, the wrapping sheet 16 covers the entire first base material 11, the water absorption layer 12, and the second base material 13. With such a configuration, it is possible to prevent the particulate water absorbing agent 14 from falling off from the water absorbing sheet 10.
  • the wrapping sheet 16 does not need to cover the entire first base material 11, the water absorption layer 12, and the second base material 13.
  • the wrapping sheet 16 is arranged on the first base material 11, bent so as to wrap the side surface of the water absorbing layer 12 and the side surface of the second base material 13, and absorbs the liquid of the second base material 13.
  • the wrapping sheet 16 may be folded on the surface opposite to the surface to be formed (that is, the surface provided with the water absorption layer 12). That is, in the wrapping sheet 16, one end of the wrapping sheet 16 and the other end of the wrapping sheet 16 overlap on the surface of the second base material 13 opposite to the surface on which the water absorption layer 12 is provided.
  • the wrapping sheet 16 covers the first base material 11, the water absorption layer 12, and the side surface of the second base material 13, and is opposite to the surface of the second base material 13 on which the water absorption layer 12 is provided. Covers all or part of the side surface.
  • the wrapping sheet 16 is placed on the first base material 11, bent so as to wrap the side surface of the water absorption layer 12 and the side surface of the second base material 13, and is absorbed by the second base material 13.
  • One end of the wrapping sheet 16 and the other end of the wrapping sheet 16 may be arranged apart from each other on the surface opposite to the surface (that is, the surface provided with the water absorption layer 12).
  • the wrapping sheet 16 covers the liquid absorbing surface and the side surface of the first base material 11, the side surface of the water absorbing layer 12, and the side surface of the second base material 13, and the water absorbing layer of the second base material 13. It covers a part of the surface opposite to the surface on which the 12 is provided.
  • the wrapping sheet 16 is not an essential configuration in the water-absorbent sheet according to the present invention, the water-absorbent sheet 10 according to the present invention is provided with the wrapping sheet 16 in such a configuration so that the water-absorbing agent 14 can absorb water. It is possible to prevent the sheet 10 from falling off.
  • the wrapping sheet 16 to be arranged on the surface of the first base material 11 (that is, on the liquid-absorbing surface of the first base material 11) is placed. It is preferable to have.
  • the first base material 11 forms a water absorbing surface that directly absorbs the liquid.
  • the water-absorbing layer contains the particulate water-absorbing agent, and the region containing the particulate water-absorbing agent is arranged with a gap substantially free of the particulate water-absorbing agent, and the surface of the wrapping sheet. However, it forms a water-absorbing surface that directly absorbs the liquid, and the first base material has an elongation rate of 10% or more.
  • an adhesive may be used as a method of fixing the wrapping sheet 16 to the base materials 11 and 13, for example.
  • the first base material 11 and the particulate water-absorbing agent 14 in the water-absorbing layer 12 are preferably in contact with each other directly or via an adhesive, and / Alternatively, it is preferable that the second base material 13 and the particulate water absorbing agent 14 in the water absorbing layer 12 are in contact with each other directly or via an adhesive.
  • the water-absorbent sheet of the present invention is substantially a particulate water-absorbing agent sandwiched between a first base material, a second base material, and a first base material and a second base material.
  • More preferred embodiments include a first substrate; a second substrate; a first substrate, a particulate water absorbent sandwiched between the second substrates; a particulate water absorbent and a second substrate. It has a simple structure consisting only of an adhesive that adheres a particulate water-absorbing agent to the base material to the second base material; and a wrapping sheet that wraps all of them. That is, although the water-absorbent sheet of the present invention has a simple structure, the specific return amount can be effectively reduced.
  • the water-absorbent sheet according to the second embodiment of the present invention includes a laminate in which the first base material is laminated on the water-absorbent layer A and a structure in which an intermediate base material is laminated on the water-absorbent layer B. , (The water absorption layer is located on the side of the second base material), and is laminated on the second base material.
  • the second embodiment will be described with reference to FIG. 19, but in the second embodiment, the requirements to which the same configuration as that of the first embodiment can be applied will be omitted.
  • FIG. 19 is a schematic view showing a cross section of the water-absorbent sheet 20 according to the second embodiment of the present invention.
  • the water-absorbing sheet 20 has the first base material 11a and the water-absorbing layer 12a (water-absorbing layer A) in order from the direction in which the liquid to be absorbed is introduced (in the direction of the arrow in FIG. 19).
  • the intermediate base material 11b and the water absorption layer 12b (water absorption layer B) are laminated on the second base material 13. That is, the water-absorbent sheet 20 has a laminated body 18a in which the first base material 11a is laminated on the water-absorbent layer 12a on the second base material 13, and an intermediate base material 11b is laminated on the water-absorbent layer 12b.
  • the structure 18b is laminated on the second base material 13 with the water absorption layers 12a and 12b positioned on the side of the second base material 13.
  • the particulate water absorbing agent 14 in the laminated body 18a will be referred to as a particulate water absorbing agent 14a
  • the gap 15 will be referred to as a gap 15a
  • the particulate water absorbing agent 14 in the structure 18b will be referred to as a particulate water absorbing agent 14b
  • the gap 15 will be referred to as a gap 15b. .
  • the first base material 11a in the second embodiment is the same as the first base material 11 in the first embodiment, it may be abbreviated as the first base material 11.
  • the particulate water absorbing agent 14a and the gap 15a in the second embodiment may also be simply referred to as the particulate water absorbing agent 14 and the gap 15.
  • the water absorbing layers 12a and 12b are composed of the particulate water absorbing agents 14a and 14b, respectively, as in the first embodiment.
  • the water absorbing layer 12a is composed of a particulate water absorbing agent 14a fixed to the first base material 11a and a particulate water absorbing agent 14a fixed to the intermediate base material 11b
  • the water absorbing layer 12b is composed of a particulate water absorbing agent 14a. It is composed of a particulate water absorbing agent 14b fixed to the intermediate base material 11b and a particulate water absorbing agent 14b fixed to the second base material 13.
  • the regions containing the particulate water absorbing agents 14a and 14b are arranged so as to be separated by gaps 15a and 15b, respectively.
  • the gaps 15a and 15b regions in which the particulate water-absorbing agent 14 does not exist
  • the regions containing the particulate water absorbing agents 14a and 14b and the gaps 15a and 15b have a shape extending along one direction on the liquid absorbing surface of the first base material and are arranged in parallel. Is preferable.
  • the region of the laminated body 18a containing the particulate water absorbing agent 14a and the region of the constituent 18b containing the particulate water absorbing agent 14b are overlapped with each other in the plane direction of the first base material 11a. Although they are arranged at the same position (that is, at the same position in the direction perpendicular to the liquid absorption surface of the first base material 11a) with the same thickness and width, the positional relationship, the thickness, and the width relationship are not limited thereto.
  • the region of the laminated body 18a containing the particulate water absorbing agent 14a and the region of the constituent 18b containing the particulate water absorbing agent 14b may be arranged so as not to overlap in the plane direction. Further, the region of the laminated body 18a containing the particulate water-absorbing agent 14a may be wider or narrower, or thicker or thinner than the region of the structure 18b containing the particulate water-absorbing agent 14b.
  • Particley water absorbents 14a and 14b may be present in the first base material 11a and the intermediate base material 11b.
  • the first base material 11a may contain the particulate water absorbing agent 14a, but in the intermediate base material 11b, the particulate water absorbing agent 14a is intermediate on the surface of the intermediate base material 11b on the liquid absorbing surface side.
  • the particulate water absorbing agent 14b may be present on the surface of the base material 11b on the side of the second base material 13.
  • the first base material 11, the water-absorbent layer 12, the particulate water-absorbent agent 14, and the gap 15 of the first embodiment are liquid. Is read as the first base material 11a, the water absorption layer 12b, the particulate water absorption agent 14a, and the gap 15a of the laminate 18a arranged on the side where is introduced; (1) Content ratio of particulate water absorbing agent 14 in the first base material 11 (2) From the liquid absorbing surface of the first base material 11 to the surface of the second base material 13 on the water absorbing layer 12 side in the gap 15. The ratio of the thickness (Lb) from the liquid absorbing surface of the first base material 11 to the surface of the second base material 13 on the water absorbing layer 12 side in the region containing the particulate water absorbing agent 14 (La). Lb / La).
  • the region containing the particulate water absorbing agents 14a and 14b of the laminated body 18a and the constituent body 18b and the gaps 15a and 15b are in the plane direction of the first base material 11a. It may be formed without overlapping.
  • the gap 15 of "in the gap 15" which is the reference of La is the gap 15a close to the liquid absorbing surface of the first base material 11a (that is, in the laminated body 11a), and is the reference of Lb.
  • the region containing the particulate water absorbing agent 14 in the region containing the particulate water absorbing agent 14 is the region where the particulate water absorbing agent 14a close to the liquid absorbing surface of the first base material 11a (that is, in the laminated body 11a) is used. This is the area that is included.
  • the particulate water-absorbing agent 14 in the first base material 11a when the particulate water-absorbing agent 14 is present in the first base material 11a, the particulate water-absorbing agent 14 in the first base material 11a
  • the content ratio is preferably 5% or more with respect to the particulate water absorbing agent 14 contained in the entire water absorbing sheet 20.
  • the thickness (La) from the liquid-absorbing surface of the first base material 11a in the gap 15a to the surface of the second base material 13 on the water-absorbing layer 12b side is preferably 1.05 or less.
  • the content ratio of the particulate water-absorbent 14a in the first base material 11a and Lb / La can be similarly applied to the preferable range of the water-absorbent sheet 10 according to the first embodiment.
  • the water-absorbent sheet 20 has a wrapping sheet 16.
  • the wrapping sheet 16 is arranged on the first base material 11a, and is folded so as to wrap the entire laminated body 18a, the constituent body 18b, and the second base material 13. Therefore, the water-absorbent sheet 20 according to the second embodiment of the present invention has at least a wrapping sheet 16 to be arranged on the surface of the first base material 11a (that is, the liquid-absorbent surface of the first base material). Is preferable.
  • a water-absorbent sheet having a first base material, an intermediate base material, a second base material, a water-absorbent layer, and a wrapping sheet.
  • a laminate in which the first base material is laminated on the water absorption layer and a structure in which the intermediate base material is laminated on the water absorption layer are formed on the second base material.
  • the wrapping sheet is arranged on the surface of the first base material, and the water absorbing layer contains a particulate water absorbing agent and is in the form of particles.
  • the region containing the water absorbing agent is arranged with a gap substantially free of the particulate water absorbing agent, and the surface of the wrapping sheet forms a liquid absorbing surface that directly absorbs the liquid, and the first
  • the base material of No. 1 has an elongation rate of 10% or more.
  • the first base material 11a and the particulate water-absorbing agent 14a in the water-absorbing layer 12a are preferably in contact with each other directly or via an adhesive, and an intermediate group is used.
  • the material 11b and the particulate water absorbing agent 14a in the water absorbing layer 12a are preferably in contact with each other directly or via an adhesive, and the intermediate base material 11b and the particulate water absorbing agent 14b in the water absorbing layer 12b are directly or adhesive.
  • the second base material 13 and the particulate water absorbing agent 14b in the water absorbing layer 12b are preferably brought into contact with each other directly or via an adhesive.
  • the ratio of the region containing the particulate water absorbing agent 14b on the water absorbing layer 12b side (the surface on which the particulate water absorbing agent 14b is arranged) of the intermediate base material 11b is preferably 90% or less in terms of area, preferably 80%. It is more preferably less than or equal to, and even more preferably 75% or less.
  • the ratio of the region containing the particulate water absorbing agent 14a on the surface of the first base material 11a on the water absorbing layer 12a side and the ratio of the region containing the particulate water absorbing agent 14b on the water absorbing layer 12b side of the intermediate base material 11b. is preferably 10% or more in area, and more preferably 20% or more.
  • the ratio of the region containing the particulate water absorbing agent 14a on the surface of the first base material 11a on the water absorbing layer 12a side is such that the surface of the intermediate base material 11b on the water absorbing layer 12a side (the particulate water absorbing agent 14a is arranged).
  • the ratio of the region containing the particulate water absorbing agent 14a in the surface) is the same as the ratio of the region containing the particulate water absorbing agent 14b in the water absorbing layer 12b of the intermediate base material 11b, and the ratio of the region containing the particulate water absorbing agent 14b is the water absorbing layer of the second base material 13. It is the same as the ratio of the region containing the particulate water absorbing agent 14b in 12b (the surface on which the particulate water absorbing agent 14b is arranged).
  • the ratio of the regions where the particulate water-absorbents 14a and 14b are present in the first base material 11 or the second base material 13 can be calculated in the same manner as in the water-absorbent sheet 10.
  • the content of the particulate water absorbing agent 14 contained in the water absorbing sheet 20 is preferably 200 to 360 g / m 2 , more preferably 210 to 350 g / m 2 , and further preferably 225 to 325 g. / M 2 .
  • the total amount of the particulate water-absorbing agents 14a and 12b existing in the water-absorbing layers 12a and 12b may be adjusted to be within the above range, and preferably, the particulate water-absorbing agents existing in the water-absorbing layers 12a and 12b may be adjusted.
  • the amounts of the agents 14a and 12b are preferably 2: 1 to 1: 2, and more preferably 1.5: 1 to 1: 1.5.
  • the first base material 11 can be in a bulky form (a form having a low bulk density and a significantly thick form). However, it can be made thinner than the absorber used in the conventional absorbent article.
  • the thickness thereof is, for example, 40% RH to 50% RH, preferably 15 mm or less, more preferably 10 mm or less, still more preferably 7 mm or less, particularly. It is preferably 5 mm or less, and most preferably 4 mm or less.
  • the lower limit of the thickness is preferably 0.2 mm or more, more preferably 0.3 mm or more, still more preferably 0.5 mm in consideration of the strength of the water absorbing sheets 10 and 20 and the diameter of the particulate water absorbing agent 14. That is all.
  • the thickness of the water-absorbent sheets 10 and 20 used in the examples of the present application was 2 to 5 mm.
  • the thickness of the first base material 11, the intermediate base material 11b, the second base material 13, the lapping sheet 16, and the water absorbing sheets 10 and 20 in the present application is a dial thickness gauge large type (thickness measuring instrument) (Co., Ltd.). Measurement was performed using a manufacturer of Ozaki Seisakusho, model number: JB, stylus: anvil top and bottom ⁇ 50 mm). The number of measurement points was 5 points at different points on the sheet to be measured, and the measurement was performed twice at each point, and the measured values were the average value of a total of 5 points. When measuring the thickness, the thickness was measured by slowly releasing the hand from the handle so that pressure was not applied to the sheet to be measured as much as possible.
  • the sheet to be measured is pasted flat on a plate having a constant thickness so that wrinkles and distortion do not occur at the measurement location, and the plate is set on the lower stylus of the thickness measuring instrument. To do. Next, after bringing the upper stylus of the thickness measuring instrument close to a height position of 2 to 3 mm from the sheet to be measured, slowly release the hand from the handle to measure the combined thickness of the sheet and the plate to be measured.
  • the surface of the water-absorbent sheets 10 and 20 (the liquid-absorbing surface that directly absorbs the liquid of the first base material 11) in order to further impart liquid permeability, diffusivity, flexibility, etc. to the water-absorbent sheets 10 and 20.
  • the surface of the wrapping sheet 16 may be appropriately embossed.
  • the region to be embossed may be the entire surface of the water-absorbent sheets 10 and 20 or a part thereof. By providing a continuous embossed region in the longitudinal direction of the water-absorbent sheets 10 and 20, the liquid can be easily diffused in the longitudinal direction.
  • the water-absorbing layer 12 has a gap 15 in which the particulate water-absorbing agent 14 does not exist.
  • the region serves as a liquid passage (liquid transport passage) for flowing a large amount of liquid.
  • the embossed region may be provided linearly, curvedly, or corrugated.
  • the first base material is a water-permeable sheet located on the side where the liquid to be absorbed is introduced.
  • the liquid to be absorbed is not limited to water, but urine, blood, sweat, feces, waste liquid, moisture, vapor, ice, a mixture of water and an organic solvent and / or an inorganic solvent, rainwater, groundwater, etc. However, it is not particularly limited as long as it contains water.
  • urine, menstrual blood, sweat and other body fluids can be mentioned.
  • the water permeability of the water-permeable sheet preferably has a water permeability coefficient (JIS A1218: 2009) of 1 ⁇ 10-5 cm / sec or more.
  • the hydraulic conductivity is more preferably 1 ⁇ 10 -4 cm / sec or more, even more preferably 1 ⁇ 10 -3 cm / sec or more, particularly preferably 1 ⁇ 10 ⁇ 2 cm / sec or more, and most preferably 1 ⁇ It is 10 -1 cm / sec or more.
  • the hydraulic conductivity of the first substrate used in the examples of the present application was 1 ⁇ 10-5 cm / sec or more.
  • the elongation rate of the first base material is 10% or more, preferably 15% or more, more preferably 17% or more, still more preferably 20% or more, still more preferably. Is 22% or more.
  • the upper limit of the elongation rate of the first base material is not particularly limited, but is preferably 60% or less.
  • the first base material can easily follow the shape of the particulate water absorbing agent, and as a result, the shape retention of the water absorbing sheet is further enhanced, and the water absorbing sheet reverts. The amount can be further reduced.
  • the elongation rate of the first base material a value measured by the method described in Examples described later is adopted.
  • the "elongation rate of the non-woven fabric (first base material)" is a numerical value when the elongation rate is measured in the direction of maximum elongation. Further, the elongation rate of the first base material can be controlled by the bulk density, the basis weight, the material, the mesh structure, the manufacturing process conditions, and the like.
  • the extending direction of the first base material is not particularly limited as long as it extends in any one direction parallel to the surface direction of the first base material, excluding the thickness direction.
  • any one direction from any angle direction such as the long side direction, the short side direction, and the diagonal direction of the sheet plane may be stretched at the elongation rate in the above range.
  • it is a substrate that can extend from all directions (isotropic).
  • the first base material preferably has a basis weight of 3 to 80 g / m 2 , more preferably 5 to 70 g / m 2 , and even more preferably 10 to 60 g / m 2. ..
  • the basis weight of the first base material is within such a range, it becomes easy to take in the particulate water-absorbing agent into the first base material, and as a result, the shape-retaining property of the water-absorbent sheet is further enhanced, and the amount of reversion is increased. It can be further reduced.
  • the first substrate has a bulk density is preferably at 0.1 g / cm 3 or less, more preferably at 0.08 g / cm 3 or less, is 0.05 g / cm 3 or less Is even more preferable.
  • the bulk density of the first substrate preferably being 0.001 g / cm 3 or more, more preferably 0.005 g / cm 3 or more, further preferably 0.01 g / cm 3 or more.
  • the bulk density is the mass with respect to the unit volume, and is not the density when the base material is compressed under high pressure (when the voids are eliminated), but the density obtained from the volume of the base material including the volume of the voids. Is.
  • the bulk density of the first base material is 0.1 g / cm 3 or less, it means that the first base material is light. Bulky means low bulk density and significantly thicker.
  • the first base material is bulky, it becomes easy to incorporate the particulate water absorbing agent into the first base material, and as a result, the shape retention of the water absorbing sheet is further enhanced, and the amount of reversion can be further reduced. .. Further, in the present invention, the following effects can be expected due to the bulkiness of the first base material. That is, since the first base material is bulky, the absorbed liquid in contact with the liquid absorption surface of the first base material quickly flows into the lower water absorption layer and the second base material, and the first base material is used.
  • the amount of liquid remaining on the liquid absorbing surface of the base material can be reduced. Further, when the absorbed liquid reaches the water absorption layer, the liquid is diffused in the surface direction. Therefore, even if a large amount of the liquid is introduced into the water absorption layer, the water absorption layer spreads in the surface direction instead of locally. It will absorb the liquid. That is, the bulky first base material has low water absorption, high liquid permeability, and high liquid diffusivity. As a result, the amount of reversion in the water-absorbent sheet can be reduced. The humidity of the liquid absorbing surface of the first base material can be suppressed, and the discomfort to the skin can be reduced.
  • the bulk density of the first base material is preferably 0.1 g / cm 3 or less. In this specification, the bulk density is a value calculated in Examples described later.
  • the thickness of the first substrate is, for example, 40% RH to 50% RH, preferably 0.3 mm or more, more preferably 0.4 mm or more, still more preferably 0.5 mm or more, and particularly preferably 0.6 mm or more. Most preferably, it is 0.7 mm or more.
  • the thickness of the first substrate is, for example, 40% RH to 50% RH, preferably 5 mm or less, more preferably 4 mm or less, even more preferably 3 mm or less, particularly preferably 2.5 mm or less, and most preferably 2 mm or less. Is.
  • the thickness of the first base material is within such a range, a sufficient distance between the liquid absorbing surface of the first base material and the water absorbing layer and the second base material can be sufficiently secured, and the water absorbing layer and the first base material are once used. It is possible to significantly reduce the reversion of the liquid that has reached the base material of 2.
  • the thickness and bulk density of the first base material can be controlled by the material constituting the first base material, the manufacturing method of the first base material, and the like, and the thickness and bulk of the first base material are balanced by these factors.
  • the density is fixed.
  • the first base material has a particulate water absorbing agent transmittance (permeability of the particulate water absorbing agent with respect to the first base material) of preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably. In this order, it is 60% by mass or more, 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more.
  • the upper limit of the transmittance is not particularly limited, but is preferably 99% by mass or less. Since the transmittance of the particulate water-absorbing agent with respect to the first base material is within such a range, the particulate water-absorbing agent easily enters the first base material on the side in contact with the water-absorbing layer of the first base material. Become.
  • the water-absorbing agent in the form of particles can absorb the water contained in the first base material, and the reversion is further reduced.
  • the transmittance of the particulate water-absorbing agent with respect to the first base material is the ratio of the particulate water-absorbing agent that permeates the first base material, and as shown in FIG. 23, on the first base material.
  • the granular water-absorbing agent present in the above is determined by the weight of the particulate water-absorbing agent that has passed through the first base material when it is shaken under predetermined conditions described later, and more specifically, the method described in Examples described later. It is a value calculated by.
  • the particulate water absorbing agent used for the transmittance when a plurality of water absorbing layers are present as in the second embodiment, the entire particulate water absorbing agent contained in each water absorbing layer is used.
  • the transmittance of the particulate water absorbing agent with respect to the first base material is determined by the properties of the members constituting the first base material, the surface state thereof, and the complexity of the network structure when the first base material is a non-woven fabric. , Fiber diameter, fusion state between fibers, basis weight, thickness, etc. can be adjusted to a desired range. For example, if an air-through non-woven fabric is used as the first base material as described later, the transmittance can be adjusted by changing the heat treatment conditions, fiber diameter and density of the air-through non-woven fabric.
  • the material constituting the first base material examples include paper (sanitary paper, for example, tissue paper, toilet paper and towel paper), net, non-woven fabric, woven cloth, film and the like. Above all, from the viewpoint of water permeability, a non-woven fabric is preferably used as at least the first base material.
  • the non-woven fabric used is not particularly limited, but from the viewpoint of liquid permeability, flexibility and strength when made into a water-absorbent sheet, polyolefin fibers such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), and the like.
  • Non-woven fabrics made of polyester fibers such as polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN), polyamide fibers such as nylon, rayon fibers, and other synthetic fibers, cotton, silk, linen, pulp (cellulose) fibers, etc. Examples thereof include non-woven fabrics produced by mixing.
  • rayon fiber, polyolefin fiber, polyester fiber, pulp fiber and a fiber in which these are mixed are preferable, and polyolefin fiber is more preferable.
  • These fibers may be hydrophilized.
  • the non-woven fabric that can be used as the first base material is not particularly limited, and may be obtained by any method such as an air-through method; an air-laid method; a spunbond method; a spunlace method. Is preferably obtained by the air-through method or the air-laid method, and is preferably obtained by the air-through method (air-through non-woven fabric).
  • the air-laid method is a method in which air is placed on an air flow to uniformly disperse it and then absorbed onto a wire mesh to form a non-woven fabric. Since air is used to disperse pulp fibers, the volume is increased and the density is reduced. can do. Since the first base material is an air-through non-woven fabric, the absorbed liquid is likely to be quickly introduced into the first base material after coming into contact with the liquid absorbing surface of the first base material. That is, by using the air-through non-woven fabric as the first base material, it is possible to use the first base material having low water absorption and high liquid permeability, and the amount of reversion in the water absorption sheet can be significantly reduced. ..
  • the intermediate base material is an arbitrary base material arranged between the first base material and the second base material, and is a water permeable sheet.
  • the preferred range of the hydraulic conductivity of the intermediate substrate is the same as that described in the column of the first substrate.
  • the water permeability coefficient of the intermediate base material (intermediate non-woven fabric) used in the examples of the present application was 1 ⁇ 10-5 cm / sec or more.
  • the elongation rates of the intermediate base materials are 10% or more, 15% or more, 17% or more, 20% or more, and 22% or more in the preferred order.
  • the upper limit of the elongation rate of the intermediate base material is not particularly limited, but is preferably 60% or less. When the elongation rate of the intermediate base material is within such a range, the intermediate base material can easily follow the shape of the particulate water absorbent, and as a result, the shape retention of the water-absorbent sheet is further improved and the amount of reversion is further reduced. it can.
  • the preferable ranges regarding the amount of grain, bulk density, thickness, permeability of the particulate water absorbent, and the transmittance of the specific particulate water absorbent of the intermediate base material are the same as those described in the column of the first base material. Is.
  • the materials constituting the intermediate base material are the same as those described in the column of the first base material above.
  • the second base material is a water-permeable sheet and is located on the opposite side to the side where the liquid is absorbed, the performance of the water-absorbent sheet (return amount, leakage in the plane direction, etc.), which is the effect of the present invention, is achieved. Can be fully demonstrated.
  • the water permeability of the water-permeable sheet preferably has a water permeability coefficient (JIS A1218: 2009) of 1 ⁇ 10-5 cm / sec or more.
  • the hydraulic conductivity is more preferably 1 ⁇ 10 -4 cm / sec or more, even more preferably 1 ⁇ 10 -3 cm / sec or more, particularly preferably 1 ⁇ 10 ⁇ 2 cm / sec or more, and most preferably 1 ⁇ It is 10 -1 cm / sec or more.
  • the thickness of the second substrate is, for example, 40% RH to 50% RH, preferably 0.05 mm or more, more preferably 0.08 mm or more, still more preferably 0.1 mm or more, and particularly preferably 0. It is 2 mm or more, most preferably 0.3 mm or more.
  • the thickness of the second substrate is, for example, 40% RH to 50% RH, preferably less than 0.9 mm, more preferably 0.8 mm or less, still more preferably 0.7 mm or less, and particularly preferably 0.6 mm or less. Most preferably, it is 0.5 mm or less.
  • the thickness of the first base material is 0.3 mm or more and 5 mm or less, and the thickness of the second base material is 0.05 mm or more and less than 0.9 mm.
  • the thickness of the first base material is preferably 0.4 mm or more and 4 mm or less, and the thickness of the second base material is 0.08 mm or more and 0.8 mm or less.
  • the thickness of the first base material is 0.5 mm or more and 3 mm or less
  • the thickness of the second base material is 0.1 mm or more and 0.7 mm or less, and even more preferably the thickness of the first base material.
  • the thickness is 0.6 mm or more and 2.5 mm or less
  • the thickness of the second base material is 0.2 mm or more and 0.6 mm or less, and particularly preferably the thickness of the first base material is 0.7 mm or more and 2 mm or less.
  • the thickness of the second base material is 0.3 mm or more and 0.5 mm or less.
  • the bulk density of the second substrate is preferably at 1 g / cm 3 or less, more preferably at 0.5 g / cm 3 or less, that is 0.3 g / cm 3 or less More preferred.
  • the bulk density of the second substrate is preferably 0.05 g / cm 3 or more, more preferably 0.07 g / cm 3 or more, further preferably 0.08 g / cm 3 or more.
  • the second base material preferably has a basis weight of 5 to 100 g / m 2 , more preferably 10 to 70 g / m 2 , and further preferably 15 to 65 g / m 2. Preferred.
  • the thickness, bulk density, and basis weight of the second base material can be controlled by the material constituting the second base material, the manufacturing method of the second base material, and the like. The thickness and bulk density are determined.
  • the porosity of the first base material, the second base material and the wrapping sheet can be measured by the following formula.
  • Poleolefin) density C (g / cm 3 ) Porosity (%) of the base material (or sheet) 100- ⁇ (A / 10000) / (B / 10) ⁇ / C * 100
  • the second substrate is preferably a liquid distribution area is 1000 mm 2 or more, more preferably 3000 mm 2 or more, more preferably at 6000 mm 2 or more, and particularly preferably 7000 mm 2 or more.
  • the upper limit of the liquid diffusion area of the second base material is not particularly limited, but is preferably 10,000 mm 2 or less, for example.
  • the liquid diffusion area of the second base material is within the above range, when the absorbed liquid reaches the second base material, the liquid can be sufficiently diffused in the plane direction on the second base material.
  • the second base material absorbs the liquid while spreading in the plane direction instead of locally. Therefore, the liquid can be sufficiently absorbed and retained in the second base material, and the amount of reversion in the water-absorbent sheet can be significantly reduced.
  • the liquid diffusion area diffuses when the liquid comes into contact with a base material (for example, a non-woven fabric) and / or when the liquid passes through the base material in a direction perpendicular to the surface direction of the base material. It means the area in the plane direction, and is a value calculated by the method described in Examples described later. The larger the liquid diffusion area of the base material, the higher the liquid diffusibility of the base material in the plane direction.
  • a non-woven fabric is preferably used as the material constituting the second base material.
  • the same material as that of the first base material can be applied, and for example, rayon fiber, polyolefin fiber, polyester fiber, pulp fiber and fiber in which these are mixed are preferable, and the non-woven fabric is more preferable. preferable.
  • the non-woven fabric that can be used as the second base material is not particularly limited, and may be obtained by any method such as an air-through method; an air-laid method; a spunbond method; a spunlace method. However, it is preferable that the material is obtained by the air-laid method (air-laid non-woven fabric) or the spun-lace method (spun-laced non-woven fabric).
  • the spunlace method is a method in which fibers are entangled with a high-pressure water stream and does not use an adhesive.
  • the water-absorbing layer in the water-absorbing sheet according to the embodiment of the present invention has a particulate water-absorbing agent.
  • the water absorbing layers may have the same composition or different compositions.
  • the water absorption layer contains a particulate water absorption agent.
  • the water absorbing agent is a mixture of a plurality of types of particulate water absorbing agents
  • the following description is a description of the physical properties of the mixture. That is, the physical characteristics of the particulate water-absorbing agent are the physical characteristics when all the particulate water-absorbing agents contained in the water-absorbing layer are mixed. Further, the physical characteristics of the particulate water-absorbing agent may be measured by taking out only the particulate water-absorbing agent from the water-absorbent sheet so that cotton-like pulp or the like is not mixed.
  • surface tension is the work (free energy) required to increase the surface area of a solid or liquid, expressed per unit area.
  • the surface tension referred to in the present application refers to the surface tension of the aqueous solution when the particulate water absorbent is dispersed in the 0.90 mass% sodium chloride aqueous solution.
  • the surface tension of the water absorbing agent is measured by the following procedure. That is, 50 ml of physiological saline adjusted to 20 ° C. was placed in a thoroughly washed 100 ml beaker, and the surface tension of the physiological saline was first measured using a surface tension meter (K11 automatic surface tension meter manufactured by KRUSS). To measure.
  • a fully washed 25 mm long fluororesin rotor and 0.5 g of a particulate water absorbent were placed in a beaker containing a physiological saline solution adjusted to 20 ° C. after measuring the surface tension, at 500 rpm. Stir for 4 minutes under the conditions. After 4 minutes, the stirring is stopped, and after the water-containing particulate water absorbent has settled, the surface tension of the supernatant is measured again by performing the same operation.
  • a plate method using a platinum plate is adopted, and the plate is sufficiently washed with deionized water before each measurement and heated and washed with a gas burner before use.
  • the surface tension of the particulate water-absorbing agent is 60 mN / m or more, 65 mN / m or more, 66 mN / m or more, 67 mN / m or more, 69 mN / m or more, in the following order. It is preferably 70 mN / m or more, 71 mN / m or more, and most preferably 72 mN / m or more.
  • the particulate water-absorbing agent When the particulate water-absorbing agent is applied to a water-absorbent sheet, the influence of surface tension is more likely to appear than that of conventional paper diapers, and when the surface tension satisfies the above conditions, the amount of reversion in the water-absorbent sheet can be reduced.
  • the upper limit of the surface tension of the particulate water-absorbent is not particularly limited, but is actually 73 mN / m or less.
  • the CRC (water absorption ratio under no pressure) of the particulate water-absorbing agent is 30 g / g or more, 32 g / g or more, 33 g / g or more, 34 g / g or more in the following order. Is preferable, and most preferably 35 g / g or more.
  • the CRC of the particulate water absorbing agent is an abbreviation for Centrifuge Retention Capacity (centrifuge holding capacity) defined by ERT441.2-02, and the water absorption ratio of the particulate water absorbing agent under no pressure (“water absorption ratio””. It may also be called). Specifically, 0.2 g of the particulate water absorbent is placed in a non-woven fabric bag, and then immersed in a large excess of 0.9 mass% sodium chloride aqueous solution for 30 minutes for free swelling, and then a centrifuge (centrifuge). It refers to the water absorption ratio (unit: g / g) after draining with 250G).
  • the particle-like water-absorbent is not limited in its particle shape, and may be, for example, a spherical particle-like water-absorbent (and its granulated product).
  • the particulate water absorbent is preferably in the form of amorphous crushed material.
  • the amorphous crushed particles are crushed particles having a non-constant shape. This is because the amorphous crushed particles can be easily fixed to the substrate as compared with the spherical particles obtained by reverse phase suspension polymerization or vapor phase polymerization.
  • the particulate water absorbent according to one embodiment of the present invention is preferably a pulverized product in aqueous solution polymerization.
  • spherical particles or granulated products of spherical particles obtained by reverse phase suspension polymerization or droplet polymerization such as spraying and polymerizing a polymerization monomer are typically crushed into an indefinite form. Not in shape.
  • the shape of the particulate water absorbing agent is amorphous and crushed, the shape of the water absorbing sheet is more likely to be maintained as compared with the one having a high average roundness (for example, a spherical one).
  • the average roundness of the particulate water absorbent is preferably 0.70 or less, more preferably 0.60 or less, and further preferably 0.55 or less.
  • the calculation method of the average roundness is as follows. 100 or more particulate water absorbents are randomly selected, and each particulate water absorbent is photographed with an electron microscope (VE-9800 manufactured by Keyence Co., Ltd.) (magnification 50 times) to obtain an image of the particulate water absorbent. , The peripheral length and area were calculated for each particle using the attached image analysis software. The following formula:
  • the roundness of each particle is obtained with, and the average value of the obtained values is calculated as the average roundness.
  • particle size The particle size of the particulate water-absorbing agent (or particulate water-absorbent resin, water-absorbent resin particles) according to the embodiment of the present invention is obtained according to the measurement method of "PSD" specified in ERT420.2-02.
  • PSD the measurement method of "PSD" specified in ERT420.2-02.
  • the weight average particle size is 150 to 600 ⁇ m. In the present invention, the weight average particle size is a value calculated by the method described in Examples described later.
  • the method for producing the particulate water-absorbing agent is not particularly limited as long as it is a method for producing the water-absorbing agent having desired physical properties, and for example, it can be appropriately produced in consideration of the publications described in the examples.
  • the water-absorbent sheet it is preferable to have at least a wrapping sheet to be arranged on the surface of the first base material.
  • the wrapping sheet may be arranged on the surface of the first base material, but it is more preferable that the wrapping sheet is arranged so as to cover the side surface of the first base material and the side surface of the water absorption layer. A part of the side surface of the first base material, the side surface of the water absorption layer, and the side surface of the second base material, which are opposite to the side on which the liquid to be absorbed of the second base material is introduced. Or it is more preferable to cover the whole.
  • the water-absorbent sheet includes a wrapping sheet, and the wrapping sheet is a water-permeable sheet and is located at least on the surface (the side to be absorbed) of the first base material. ..
  • the thickness of the wrapping sheet is, for example, 40% RH to 50% RH, preferably 0.001 mm or more, more preferably 0.005 mm or more, still more preferably 0.01 mm or more, and particularly preferably 0.1 mm or more. Most preferably, it is 0.2 mm or more.
  • the thickness of the wrapping sheet is, for example, 40% RH to 50% RH, preferably less than 0.9 mm, more preferably 0.8 mm or less, still more preferably 0.7 mm or less, particularly preferably 0.6 mm or less, most preferably. Is 0.5 mm or less.
  • the bulk density of the wrapping sheet is preferably at 1 g / cm 3 or less, more preferably at 0.5 g / cm 3 or less, even more preferably at 0.3 g / cm 3 or less.
  • the bulk density of the wrapping sheet is preferably 0.1 g / cm 3 or more, more preferably 0.12 g / cm 3 or more, further preferably 0.13 g / cm 3 or more.
  • the basis weight of the wrapping sheet is preferably 5 to 100 g / m 2 , more preferably 5 to 70 g / m 2 , and even more preferably 10 to 65 g / m 2 .
  • the thickness, bulk density, and basis weight of the wrapping sheet can be controlled by the material constituting the wrapping sheet, the manufacturing method of the wrapping sheet, etc., and the thickness and bulk density of the wrapping sheet are determined by these balances.
  • the material constituting the wrapping sheet is not particularly limited as long as the above-mentioned purpose of providing the wrapping sheet can be achieved, and for example, paper (sanitary paper such as tissue paper, toilet paper and towel paper), net, non-woven fabric, woven cloth. , Film and the like.
  • the non-woven fabric used is not particularly limited, but from the viewpoint of liquid permeability, flexibility and strength when made into a water-absorbent sheet, polyolefin fibers such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), and the like.
  • Non-woven fabrics made of polyester fibers such as polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN), polyamide fibers such as nylon, rayon fibers, and other synthetic fibers, cotton, silk, linen, pulp (cellulose) fibers, etc. Examples thereof include non-woven fabrics produced by mixing.
  • rayon fiber, polyolefin fiber, polyester fiber, pulp fiber and a fiber in which these are mixed are preferable, and polyolefin fiber is more preferable.
  • These fibers may be hydrophilized.
  • the non-woven fabric that can be used as the wrapping sheet is not particularly limited, and may be obtained by any method such as an air-through method; an air-laid method; a spunbond method; a spunlace method, but the spunbond method. It is preferable that it is the one obtained in (Spunbonded non-woven fabric).
  • the urine water absorbed by the water-absorbent sheet is absorbed even when the water-absorbent sheet is loaded (even when it is pressurized), such as when an infant wearing an absorbent item such as a disposable diaper is sitting.
  • a wrapping sheet having water repellency so as not to ooze out from the sheet is preferable, and for example, a spunbonded non-woven fabric is preferable.
  • the method for producing a spunbonded non-woven fabric is a method of directly accumulating long continuous fibers obtained by melting and spinning a raw material resin to form a fleece. Examples of the raw material resin include polyethylene, polypropylene, polylactic acid and the like.
  • the method for producing the first base material, the method for producing the second base material, and the method for producing the wrapping sheet are different.
  • the first base material is an air-through non-woven fabric
  • the second base material is an air-laid non-woven fabric and a spunlace non-woven fabric
  • the wrapping sheet is a spunbond non-woven fabric, which are different non-woven fabrics. Is. With such a form, the desired effect of the present invention can be efficiently achieved.
  • the method for producing a water-absorbent sheet according to the first and second embodiments of the present invention includes (1) a step of spraying a particulate water-absorbing agent on a first base material, and (2) a second base material. Includes at least one step of spraying the particulate water absorbent.
  • the following manufacturing methods (a) to (d) can be mentioned for the water-absorbent sheet according to the first embodiment.
  • Examples of the water-absorbent sheet according to the second embodiment include the following production methods (e) to (h).
  • (A) Sprinkle the particulate water absorbent on the first base material in a streak pattern.
  • the adhesive is evenly sprayed onto the second substrate.
  • the surface on which the particulate water absorbing agent of the first base material is sprayed and the surface on which the adhesive of the second base material is sprayed are overlapped and pressure-bonded so as to face each other.
  • the crimping is preferably heat crimping in the vicinity of the melting temperature of the adhesive.
  • the particulate water absorbent is sprayed in a streak pattern, and preferably the adhesive is uniformly sprayed and passed through a heating furnace so that the particulate water absorbent does not dissipate.
  • the first base material is superposed on the surface of the second base material on which the particulate water absorbing agent is sprayed, and heat-bonded.
  • the particulate water-absorbing agent is sprayed in a streak pattern to form a layer.
  • the first base material is placed on the surface of the second base material on which the particulate water absorbing agent is sprayed, and pressure-bonded using a roll press or the like.
  • (E) Sprinkle the particulate water absorbent on the first base material (or intermediate base material) in a streak pattern.
  • the adhesive is evenly sprayed onto the intermediate substrate (or the first substrate).
  • the surface of the first base material (or intermediate base material) on which the particulate water absorbing agent is sprayed and the surface of the intermediate base material (or the first base material) on which the adhesive is sprayed face each other.
  • the particulate water absorbent is sprayed in a streak pattern on the intermediate base material of the bonded body of the first base material and the intermediate base material.
  • the adhesive is evenly sprayed onto the second substrate.
  • the surface of the joint between the first base material and the intermediate base material on which the particulate water-absorbing agent is sprayed and the surface on which the adhesive of the second base material is sprayed are overlapped so as to face each other.
  • Crimping is preferably heat crimping in the vicinity of the melting temperature of the adhesive.
  • the particulate water absorbent is sprayed in a streak pattern.
  • the intermediate base material is superposed on the surface of the second base material on which the particulate water absorbing agent is sprayed, and heat-pressed to obtain a bonded body of the intermediate base material and the second base material.
  • the particulate water absorbent is sprayed in a streak pattern on the intermediate base material of the composite of the intermediate base material and the second base material.
  • the adhesive is evenly sprayed onto the first substrate.
  • the surface of the joint of the intermediate base material and the second base material on which the particulate water absorbing agent is sprayed and the surface on which the adhesive of the first base material is sprayed are overlapped and pressure-bonded so as to face each other. To do.
  • the particulate water absorbent is sprayed in a streak pattern, and preferably the adhesive is evenly sprayed and passed through a heating furnace so that the particulate water absorbent does not dissipate.
  • the first base material is superposed on the surface of the second base material on which the particulate water absorbing agent is sprayed, and heat-pressed to obtain a bonded body of the intermediate base material and the second base material.
  • the particulate water absorbent is sprayed in a streak pattern, and preferably the adhesive is uniformly sprayed and passed through a heating furnace. Fix the particulate water absorbent to the extent that it does not dissipate.
  • the first base material is superposed on the surface of the intermediate base material and the joint of the second base material on which the particulate water absorbing agent is sprayed, and heat-bonded.
  • the particulate water-absorbing agent is sprayed in a streak pattern to form a layer.
  • the intermediate base material is superposed on the surface of the second base material on which the particulate water absorbing agent is sprayed, and pressure-bonded using a roll press or the like to obtain a bonded body of the intermediate base material and the second base material.
  • the particulate water absorbent is sprayed in a streak pattern to form a layer.
  • the first base material is placed on the surface of the intermediate base material and the joint of the second base material on which the particulate water absorbing agent is sprayed, and pressure-bonded using a roll press or the like.
  • the methods (a) and (b) are preferable in the first embodiment, and the methods (e) and (e) and (in the second embodiment) are preferable from the viewpoint of simplicity of the manufacturing method and high manufacturing efficiency.
  • the method of f) is preferable.
  • the water-absorbent sheet can also be produced by using the methods (a) to (d) in the first embodiment and the methods (e) to (h) in the second embodiment in combination.
  • the method of spraying the particulate water absorbing agent in a streak pattern is not particularly limited, but for example, it can be sprayed in a streak pattern by using a paper pattern.
  • a plate having the same size as the water-absorbent sheet and hollowed out in a striped pattern arranged in a certain width and length is used as a paper pattern.
  • This paper pattern is placed on a base material on which the particulate water absorbing agent is to be sprayed, and the particulate water absorbing agent is sprayed on the hollowed-out holes.
  • the paper pattern is removed after spraying the particulate water-absorbing agent, the particulate water-absorbing agent is sprayed in a streak pattern on the base material.
  • the adhesive is applied in stripes on the base material by screen printing or the like, the particulate water absorbent is sprayed on the base material, and then the particulate water absorbent that is not in contact with the adhesive on the base material is removed. By dropping it, the particulate water-absorbing agent can be sprayed on the base material in a streak pattern.
  • the water-absorbent sheet includes the wrapping sheet as shown in FIGS. 18 and 19, (3) the first base material, the water-absorbent layer, the second base material, or the first base material.
  • the step of covering the water absorption layer, the intermediate base material, the water absorption layer, and the second base material with a wrapping sheet arranged on the first base material is included.
  • a sheet in which the first base material, the water absorption layer, and the second base material obtained through the steps (a) or (b) or (e) or (f) are pressure-bonded, or the first base material.
  • a sheet in which a base material, a water absorption layer, an intermediate base material, a water absorption layer, and a second base material are pressure-bonded is placed on a wrapping sheet with the first base material facing down, and a second base which is an upper surface.
  • the adhesive is sprayed on the material (the surface on the side where the water absorption layer is not crimped), and the remaining part of the wrapping sheet protruding from the first base material is bent to form the adhesive surface and the wrapping sheet of the second base material.
  • a water-absorbent sheet having a wrapping sheet can be obtained by wrapping the sheets so that they come into contact with each other, turning them upside down, and then pressure-bonding them.
  • the water-absorbent sheet may be embossed for the purpose of improving the tactile sensation of the water-absorbent sheet and improving the liquid absorption performance.
  • the embossing may be performed at the same time when the first base material and the second base material are crimped, or may be performed after the sheet is manufactured. Further, the wrapping sheet may be embossed.
  • additives deodorant, fiber, antibacterial agent, gel stabilizer, etc.
  • the blending amount of the additive is preferably 0 to 50% by mass, and more preferably 1 to 10% by mass with respect to the mass of the particulate water absorbing agent.
  • a particulate water-absorbing agent mixed with an additive in advance may be used, or an additive may be added in the middle of the production process.
  • the dimensions of the manufactured water-absorbent sheet can be designed as appropriate. Usually, the width is 3 to 10 m and the length is several tens to several thousand m (in the state of continuous sheet or roll).
  • the manufactured water-absorbent sheet is cut and used according to the purpose (size of the absorbent body used).
  • the base materials as a method of fixing the base materials to each other or between the base materials and the particulate water-absorbing agent, (i) crimping may be used, and (ii) water or a water-soluble polymer.
  • Various binders dissolved or dispersed in a solvent may be used, the base materials may be heat-sealed at the melting point of the material of the base material itself (iii), or the base materials may be fixed by using an adhesive (iv).
  • the base materials, or the base material and the particulate water absorbent are preferably fixed using an (iv) adhesive.
  • the adhesive used may be a solution type, but a hot melt adhesive having high productivity and no problem of residual solvent is preferable because of the trouble of removing the solvent, the problem of the residual solvent, and the problem of productivity.
  • the hot melt adhesive may be contained in advance on the surface of the base material or the particulate water absorbent, or the hot melt adhesive may be separately used in the process of manufacturing the water absorbent sheet.
  • the form and melting point of the hot melt adhesive can be appropriately selected, and may be in the form of particles, fibers, nets, films, or liquids melted by heating.
  • the melting temperature or softening point of the hot melt adhesive is preferably 50 to 200 ° C. and 60 to 180 ° C.
  • a particulate adhesive When a particulate adhesive is used, its particle size is 0.01 to 2 times, 0.02 to 1 times, and 0.05 to 0.5 times the average particle size of the particulate water absorbent.
  • Adhesive is used.
  • a hot melt adhesive When a hot melt adhesive is used in the production of the water absorbing sheet according to the embodiment of the present invention, a mixture of the particulate water absorbing agent and the hot melt adhesive is uniformly spread on a base material (for example, a non-woven fabric).
  • a water-absorbent sheet can be produced by spraying, laminating another base material, and then heat-pressing the hot melt adhesive near the melting temperature.
  • the hot melt adhesive used in the present invention can be appropriately selected, but is preferably selected from ethylene-vinyl acetate copolymer adhesive, styrene elastomer adhesive, polyolefin adhesive, polyester adhesive and the like1 More than seeds can be used as appropriate.
  • polystyrene-based adhesive examples include polyethylene, polypropylene, and atactic polypropylene
  • examples of the styrene-based elastomer adhesive include a styrene-isoprene block copolymer (SIS) and a styrene-butadiene block copolymer (SBS).
  • SIS styrene-isoprene block copolymer
  • SBS styrene-butadiene block copolymer
  • SIBS styrene-isobutylene block copolymer
  • SEBS styrene-ethylene-butylene-styrene block copolymer
  • Copolymerized polyolefins and the like polyethylene terephthalate (PET) and polypropylene terephthalate (PET) as polyester-based adhesives ( PBT), copolymerized polyester, etc.
  • examples thereof include ethylene-vinyl acetate copolymer (EVA) adhesive; ethylene-ethyl acrylate copolymer (EEA), ethylene-acrylic.
  • EVA ethylene-vinyl acetate copolymer
  • EAA ethylene-ethyl acrylate copolymer
  • EBA acid butyl copolymer
  • the water-absorbent sheet preferably contains an adhesive, and the adhesive is preferably a hot-melt adhesive, and the adhesive (for example, the amount (content) of the hot melt adhesive) is preferably 3.0 times or less, more preferably 0.01 to 2.5 times, the mass of the particulate water absorbent. , 0.05 to 2.0 times, more preferably. If the content of the adhesive (especially hot melt melt adhesive) is too high, not only is it disadvantageous in terms of cost and the mass of the water-absorbent sheet (increased mass of the paper diaper), but also the particulate water-absorbing agent swells. In response, it may reduce the water absorption capacity of the water-absorbent sheet.
  • the adhesive is preferably a hot-melt adhesive
  • the adhesive is preferably 3.0 times or less, more preferably 0.01 to 2.5 times, the mass of the particulate water absorbent. , 0.05 to 2.0 times, more preferably. If the content of the adhesive (especially hot melt melt adhesive) is too high, not only is it disadvantageous
  • the absorbent article according to one embodiment of the present invention has a structure in which the water-absorbent sheet described in [2] is sandwiched between a liquid-permeable sheet and a liquid-impermeable sheet.
  • the liquid permeable sheet is located on the first base material side
  • the liquid permeable sheet is located on the second base material side. That is, the absorbent article according to the embodiment of the present invention is obtained by sandwiching the water-absorbent sheet of the present invention between the liquid-permeable sheet and the liquid-impermeable sheet, and the liquid-permeable sheet is the first.
  • the liquid impermeable sheet is located on the base material side and is located on the second base material side.
  • Specific examples of the absorbent article include paper diapers, incontinence pads, sanitary napkins, pet sheets, food drip sheets, water blocking agents for electric power cables, and the like.
  • liquid permeable sheet and the liquid permeable sheet those known in the technical field of absorbent articles can be used without particular limitation.
  • the absorbent article can be produced by a known method.
  • Example The present invention will be described in more detail with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Further, in the following examples, unless otherwise specified, the operation was performed under the conditions of room temperature (25 ° C.) / relative humidity of 40 to 50% RH.
  • the term "upper nonwoven fabric” means a first substrate having a liquid-absorbing surface that directly absorbs the liquid
  • the term "lower nonwoven fabric” is used.
  • the base material other than the first base material having a liquid absorbing surface that directly absorbs the liquid in the two-layer form is an intermediate base material, and is referred to here as an "intermediate nonwoven fabric".
  • Acrylic acid production example Commercially available acrylic acid (acrylic acid dimer 2000 ppm, acetic acid 500 ppm, propionic acid 500 ppm, p-methoxyphenol 200 ppm) is supplied to the bottom of a high boiling point impurity separation tower having 50 steps of a dam-free perforated plate, and the reflux ratio is set to 1.
  • Acrylic acid (acrylic acid dimer 20 ppm, acetic acid 50 ppm, propionic acid 50 ppm, furfural 1 ppm or less) by distilling as, after removing dimer (acrylic acid dimer) composed of maleic acid and acrylic acid, and further performing crystallization. , Protoanemonin (1 ppm or less) was obtained, and 50 ppm of p-methoxyphenol was further added after distillation.
  • the above reaction solution was supplied to a reactor formed by attaching a lid to a stainless steel double-armed kneader with an internal volume of 10 L having two sigma type blades, and the system was nitrogenized while keeping the reaction solution at 30 ° C. Gas replacement was performed to remove dissolved oxygen in the reaction solution. Subsequently, 28.66 g of a 10 mass% aqueous solution of sodium persulfate and 35.28 g of a 1 mass% aqueous solution of L-ascorbic acid were added while stirring the reaction solution, and the polymerization started after about 1 minute.
  • This subdivided hydrogel polymer was spread on a wire mesh of 50 mesh (mesh size 300 ⁇ m) and dried with hot air at 175 ° C. for 65 minutes.
  • the dried product was pulverized using a roll mill, further classified and blended with a wire mesh having a mesh size of 600 ⁇ m to obtain an amorphous crushed water-absorbent resin (1-1) having an average particle diameter of 350 ⁇ m.
  • a surface cross-linking agent aqueous solution containing 0.03 parts by mass of ethylene glycol diglycidyl ether, 1.0 part by mass of propylene glycol, and 3.0 parts by mass of water in 100 parts by mass of the obtained water-absorbent resin (1-1) 4.03. The parts by mass were spray-mixed.
  • the above mixture was heat-treated at a heat medium temperature of 100 ° C. for 40 minutes using a paddle-type mixing heat treatment machine to obtain a surface-crosslinked water-absorbent resin (1-2). 3.0 parts by mass of water was spray-mixed with 100 parts by mass of the obtained surface-crosslinked water-absorbent resin (1-2) and cured at 60 ° C. for 1 hour in a closed container, and then the opening was 710 ⁇ m.
  • a water-absorbent resin (1-3) was obtained by passing through a sieve.
  • Aerosil 90G hydrophilic amorphous silica, manufactured by Nippon Aerosil Co., Ltd.
  • the surface tension means the surface tension of the aqueous solution when the particulate water absorbent is dispersed in the 0.90 mass% sodium chloride aqueous solution.
  • a plate method using a platinum plate is adopted, and the plate is sufficiently washed with deionized water before each measurement and heated and washed with a gas burner before use.
  • Patterns 1 to 6 were prepared in order to spray the particulate water absorbing agent on the non-woven fabric in a streak pattern.
  • the patterns 1 to 6 are particles such that a region in which the particulate water-absorbing agent is present and a region in which the particulate water-absorbing agent is not present are formed linearly along the longitudinal direction on a paper having a length of 14 cm and a width of 44 cm. A hole was made in the area where the water absorbent was present.
  • the outer circumference 2 cm thereof shall be a frame, and the paper shall not be cut (that is, the paper pattern shall be a region in which the particulate water absorbing agent is present in the region excluding the frame, in order from the end in the lateral direction. Cut out the part to make a hole).
  • the shapes (S-1) to (S-6) formed by the patterns 1 to 6 will be described with reference to FIGS. 20 (a) to 20 (c) and 21 (a) to 21 (c).
  • 20 (a) to 20 (c) and 21 (a) to 21 (c) are schematic cross-sectional views of a single-layer water-absorbent sheet cut along the lateral direction.
  • the shapes (S-1) to (S-6) have a region containing the particulate water absorbing agent 14 and a gap 15 so as to be symmetrical with respect to the central portion of the water absorbing sheet in the lateral direction. It is formed. Therefore, the region ratio between the "particulate water absorbing agent 14" and the "gap 15" shown below may be from either the left or right along the lateral direction.
  • FIG. 20A is a (S-1) shape formed by the pattern 1.
  • the shape of (S-1) is as follows: "Particular water absorbing agent 14:15 mm, gap 15:25 mm, particulate water absorbing agent 14:20 mm, gap 15" between the first base material 11 and the second base material 13. : 25 mm, particulate water absorbing agent 14:15 mm ”are formed in order along the lateral direction.
  • FIG. 20 (b) is a (S-2) shape formed by the paper pattern 2.
  • the shape of (S-2) is as follows: "Particular water absorbing agent 14:20 mm, gap 15:20 mm, particulate water absorbing agent 14:20 mm, gap 15" between the first base material 11 and the second base material 13. : 20 mm, particulate water absorbing agent 14:20 mm ”are formed in order along the lateral direction.
  • FIG. 20 (c) is a (S-3) shape formed by the paper pattern 3.
  • the shape of (S-3) is as follows: "Particular water absorbing agent 14:10 mm, gap 15:35 mm, particulate water absorbing agent 14:10 mm, gap 15" between the first base material 11 and the second base material 13. : 35 mm, particulate water absorbent 14:10 mm ”are formed in order along the lateral direction.
  • FIG. 21 (a) is a (S-4) shape formed by the paper pattern 4.
  • the shape of (S-4) is as follows: "Particular water absorbing agent 14:25 mm, gap 15:10 mm, particulate water absorbing agent 14:30 mm, gap 15" between the first base material 11 and the second base material 13. : 10 mm, particulate water absorbing agent 14:25 mm ”are formed in order along the lateral direction.
  • FIG. 21 (b) is a (S-5) shape formed by the paper pattern 5.
  • the shape of (S-5) is such that between the first base material 11 and the second base material 13, "particulate water absorbing agent 14: 17.5 mm, gap 15:10 mm, particulate water absorbing agent 14:17. "5 mm, gap 15:10 mm, particulate water absorbing agent 14: 17.5 mm, gap 15:10 mm, particulate water absorbing agent 14: 17.5 mm" are formed in this order along the lateral direction.
  • FIG. 21 (c) is a (S-6) shape formed by the paper pattern 6.
  • the shape of (S-6) is as follows: "Particular water absorbing agent 14:10 mm, gap 15: 5 mm, particulate water absorbing agent 14:10 mm, gap 15" between the first base material 11 and the second base material 13.
  • Pattern 1 (see FIG. 20 (a)) is placed on non-woven fabric A (made by the air-through method, which is mainly composed of olefin and has a thickness of 1.4 mm, which corresponds to an intermediate non-woven fabric) cut into a length of 10 cm and a width of 40 cm. It was.
  • the pattern 1 has three rectangular holes, and the positions are adjusted so that the non-woven fabric A under the pattern 1 can be seen as much as possible from the holes. Calculate the area ratio of each hole to the total area of all the holes of the pattern 1, and divide 4.5 g (spray amount: 112.5 g / m 2 ) of the particulate water absorbent (1) by the area ratio of each hole.
  • the non-woven fabric A Separately from the non-woven fabric A, the non-woven fabric A cut into a length of 10 cm and a width of 40 cm (the same as the non-woven fabric A (thickness 1.4 mm). Hereinafter referred to as non-woven fabric A2.
  • First base material upper non-woven fabric
  • an adhesive containing styrene butadiene rubber spray glue 77, manufactured by 3M Japan Co., Ltd.
  • Pattern 1 (see FIG. 20A) was placed on the surface of the non-woven fabric A on the side not facing the particulate water absorbing agent (1). The position was adjusted so that the non-woven fabric A under the pattern 1 could be seen to the maximum through the three rectangular holes of the pattern 1. Calculate the area ratio of each hole to the total area of all the holes of the paper pattern 1, measure 4.5 g of the particulate water absorbent (1) separately by the area ratio of each hole, and measure the non-woven fabric A that can be seen from each hole. was sprayed evenly.
  • the paper pattern 1 When a part of the particulate water absorbing agent (1) is sprayed on the paper pattern, the paper pattern 1 is tilted toward the non-woven fabric A on which the particulate water absorbing agent (1) is sprayed, and the particulate water absorbing agent is applied to the paper pattern 1. I dropped it in the hole. Then, the paper pattern 1 was removed from the non-woven fabric A.
  • Non-woven fabric E with a length of 10 cm and a width of 40 cm (made by the airlaid method.
  • the main component is pulp fiber. Thickness 0.4 mm. Metsuke amount: 47 g / m 2.
  • the second base material lower non-woven fabric.
  • the non-woven fabric F (made by the spunbond method) obtained by cutting the intermediate sheet X into a length of 24 cm and a width of 40 cm.
  • the main component is olefin, the thickness is 0.1 mm, the basis weight: 13 g / m 2, and the bulk density: 0. .15 g / cm 3 (corresponding to a wrapping sheet) was wrapped to obtain a water-absorbent sheet (1).
  • Non-woven fabric F (corresponding to a wrapping sheet) cut into a length of 24 cm and a width of 40 cm is laid, and non-woven fabric A (corresponding to a first base material) cut into a length of 10 cm and a width of 40 cm is placed on the non-woven fabric F.
  • a pattern 1 (see FIG. 20 (a)) was placed on the surface. The position was adjusted so that the non-woven fabric A under the pattern 1 could be seen to the maximum through the three rectangular holes of the pattern 1. Calculate the area ratio of each hole to the total area of all the holes of the paper pattern 1, and measure 9.0 g (spray amount: 225 g / m 2 ) of the particulate water absorbent (1) by dividing it by the area ratio of each hole.
  • an adhesive containing styrene-butadiene rubber (spray glue 77, manufactured by 3M Japan Co., Ltd.) is uniformly sprayed (sprayed) on a non-woven fabric E (corresponding to the second base material) having a length of 10 cm and a width of 40 cm. Amount: 17.5 to 21.5 g / m), so that the surface of the non-woven fabric A sprayed with the particulate water absorbent (1) and the surface sprayed with the adhesive of the non-woven fabric E face each other (contact each other). ) Stacking and pressure crimping to obtain an intermediate sheet Y.
  • styrene-butadiene rubber spray glue 77, manufactured by 3M Japan Co., Ltd.
  • Example 3 A water-absorbent sheet (3) was obtained in the same manner as in Example 2 except that the air-through nonwoven fabric G having a thickness of 0.7 mm was used instead of the air-through nonwoven fabric A.
  • Example 4 A water-absorbent sheet (4) was obtained in the same manner as in Example 2 except that the pattern 2 (see FIG. 20B) was used instead of the pattern 1.
  • Example 5 A water-absorbent sheet (5) was obtained in the same manner as in Example 2 except that the pattern 3 (see FIG. 20 (c)) was used instead of the pattern 1.
  • Example 6 A water-absorbent sheet (6) was obtained in the same manner as in Example 2 except that the paper pattern 4 (see FIG. 21 (a)) was used instead of the paper pattern 1.
  • Example 7 A water-absorbent sheet (7) was obtained in the same manner as in Example 2 except that the pattern 5 (see FIG. 21 (b)) was used instead of the pattern 1.
  • Example 8 A water-absorbent sheet (8) was obtained in the same manner as in Example 2 except that the paper pattern 6 (see FIG. 21 (c)) was used instead of the paper pattern 1.
  • Example 9 The water-absorbent sheet (9) was prepared in the same manner as in Example 2 except that the non-woven fabric B (produced by the air-through method. The main component was olefin and the thickness was 2.0 mm) was used instead of the non-woven fabric A. Obtained.
  • Example 10 The water-absorbent sheet (10) was prepared in the same manner as in Example 2 except that the non-woven fabric C (manufactured by the air-through method. The main component was olefin and the thickness was 1.5 mm) was used instead of the non-woven fabric A. Obtained.
  • an adhesive containing styrene-butadiene rubber (Spray Glue 77, manufactured by 3M Japan Ltd.) is uniformly sprayed on a non-woven fabric E (corresponding to the first base material) having a length of 10 cm and a width of 40 cm. (Spray amount: 17.5 to 21.5 g / m), the surface on which the particulate water absorbing agent (1) of the non-woven fabric A is sprayed and the surface on which the adhesive of the non-woven fabric E is sprayed face each other (contact). (Like) and pressure-bonded.
  • non-woven fabric E2 Apart from the non-woven fabric E, 0.7 to 0.9 g of the adhesive is uniformly applied to the non-woven fabric E having a length of 10 cm and a width of 40 cm (hereinafter referred to as non-woven fabric E2, which corresponds to a second base material).
  • the surface on which the particulate water absorbing agent (1) of the non-woven fabric A is sprayed and the surface on which the adhesive of the non-woven fabric E2 is sprayed are overlapped so as to face each other (contact), and pressure-bonded to form an intermediate sheet. I got Z. Finally, the intermediate sheet Z was wrapped with the non-woven fabric F and pressure-bonded to obtain a water-absorbent sheet (11).
  • Example 2 A water-absorbent sheet (12) was obtained in the same manner as in Example 1 except that the particulate water-absorbent agent (1) was uniformly sprayed on the entire surface of the non-woven fabric A without using the paper pattern 1.
  • Example 3 A water-absorbent sheet (13) was obtained in the same manner as in Example 1 except that the non-woven fabric E was used instead of the non-woven fabric A2. As the intermediate non-woven fabric, the non-woven fabric A is used.
  • a water-absorbent sheet (14) was obtained in the same manner as in Example 2 except that the non-woven fabric E was used instead of the non-woven fabric A.
  • the non-woven fabrics A to C and G used in this example were all water permeable sheets.
  • the non-woven fabric for measuring the elongation was cut into a rectangle having a long side of 100 mm and a short side of 30 mm. At this time, the long side is in the width direction of the non-woven fabric roll, and the short side is in the winding length direction of the non-woven fabric roll.
  • the non-woven fabric having a length (short side) of 100 mm and a width (long side) of 400 mm used for the water-absorbent sheet in this embodiment the length (short side) is the width direction of the non-woven fabric roll and the width (long side) is the width direction.
  • the winding length direction of the non-woven fabric roll is used. As shown in FIG.
  • reference lines were drawn at positions 5 mm from both ends of the cut non-woven fabric for measuring the elongation rate so as to be parallel to the short sides. Each was sandwiched between double clips so as to overlap the reference line (FIG. 22 (b)).
  • the double clip used had a claw length of 30 mm or more.
  • a weight was attached to one of the double clips, and the total weight of the double clip to which the weight was attached and the weight was 110 g. In a room temperature atmosphere, a double clip without a weight was held, and the weight attached to the other double clip was lifted so as to float in the air, and the non-woven fabric was kept stretched by the weight of the double clip and the weight for 20 seconds.
  • Dial thickness gauge Measured using a large type (thickness measuring instrument) (manufactured by Ozaki Seisakusho Co., Ltd., model number: JB, stylus: anvil top and bottom ⁇ 50 mm). The number of measurement points was 5 times at different points, and the measured value was an average value of 5 points. When measuring the thickness, the thickness was measured by slowly releasing the hand from the handle so that pressure was not applied to the non-woven fabric as much as possible.
  • ⁇ Calculation method of bulk density of non-woven fabric> The weight of the non-woven fabric cut into a size of 10 cm or more in length and 40 cm or more in width was measured.
  • the volume of the non-woven fabric was calculated by multiplying the vertical and horizontal lengths of the non-woven fabric and the thickness measured from ⁇ thickness measurement>, respectively, and the bulk density was calculated by dividing the weight of the non-woven fabric by the volume of the non-woven fabric.
  • the mesh of the sieve and the flat surface were sufficiently separated from each other so that the non-woven fabric and the physiological saline passing through the mesh did not come into contact with the mesh.
  • the non-woven fabric absorbed the physiological saline and the diffusion of the liquid was completed, the area where the physiological saline was diffused was measured.
  • a JIS standard sieve (The IIDA TESTING SIEVE: inner diameter 80 mm; JIS Z8801-1 (2000)) having a mesh 32 with an opening of 850 ⁇ m, or a non-woven fabric cut to a diameter of 80 mm in a sieve 31 corresponding to the JIS standard sieve (No. 1).
  • the base material 11) of No. 1 was installed as shown in FIG. 23, and the periphery was fastened with a tape 33 (at least a diameter of 75 mm or more secures an area through which particles can permeate).
  • the non-woven fabric first base material 11
  • one taken out from the water-absorbent sheet by the method described later may be used.
  • the particulate water absorbent 14 (weight average particle diameter: 367 ⁇ m, particle size distribution: 850 ⁇ m to 600 ⁇ m is 6.1% 600 ⁇ m).
  • ⁇ 500 ⁇ m is 14.5% 500 ⁇ m ⁇ 300 ⁇ m is 50% 300 ⁇ m ⁇ 150 ⁇ m is 27.6% 150 ⁇ m ⁇ 45 ⁇ m is 1.9% 45 ⁇ m or less 0.1%) 10.0 g is added and a low tap type sieve shaker (stock) Using an ES-65 type sieve shaker manufactured by Iida Seisakusho Co., Ltd .; rotation speed 230 rpm, impact number 130 rpm), the particles were shaken for 5 minutes under the conditions of room temperature (20 to 25 ° C.) and relative humidity of 50% RH.
  • the particulate water absorbing agent 14 (that is, particles existing in the portion 31a below the mesh 32 of the sieve 31) has passed through the non-woven fabric (first base material 11) and the mesh 32 of the sieve 31 corresponding to the JIS standard sieve.
  • the mass (W (g)) of the water absorbing agent 14) was measured, and the transmittance of the particulate water absorbing agent 14 was calculated according to the following formula (i). The measurement was performed twice, and the average value was calculated.
  • the particulate water absorbent used for measuring the transmittance is a particulate water absorbent containing 90% by weight or more of the particulate water absorbent having a weight average particle diameter of 300 to 450 ⁇ m and a particle size distribution of 850 ⁇ m to 150 ⁇ m. Therefore, the transmittance of the particulate water-absorbing agent for the first base material calculated in this example also corresponds to the transmittance of the specific particulate water-absorbing agent for the first base material.
  • the water content is adjusted to 10% by mass or less, preferably 5 ⁇ 2% by mass, and the above-mentioned transmittance and various specifications specified in the present application. Physical properties may be measured.
  • the drying conditions for adjusting the water content are not particularly limited as long as the water-absorbent resin (particulate water-absorbing agent) is not decomposed or modified, but vacuum drying is preferable.
  • the content ratio (%) of the particulate water absorbing agent in the first base material was calculated by the following formula.
  • Content ratio (%) of particulate water-absorbing agent in the first base material particle-like water-absorbing agent area (I) in the first base material / total particle-like water-absorbing agent area (II) ⁇ 100 That is, the content ratio of the particulate water absorbing agent in the first base material is represented by the area% with respect to the total area of the particulate water absorbing agent.
  • the particulate water absorbent is less than a few percent even if it is present on the liquid absorbing surface that directly absorbs the liquid of the first base material (the surface on the side where the liquid to be absorbed by the upper non-woven fabric is introduced). Therefore, it can be considered that it does not exist.
  • the content ratio of the particulate water absorbing agent in the first base material was 5% or more with respect to the particulate water absorbing agent contained in the entire water absorbing sheet.
  • the weight 44 was removed, and the first reversion amount (g) was measured from the weight increment of the filter paper 43. 1 minute after removing the weight 44, the same operation (adding the liquid ⁇ 10 minutes after adding the liquid, placing the filter paper 43 and the weight 44 (1200 g), holding for 1 minute ⁇ holding after 1 minute ⁇ removing the weight, reversing (Measurement of amount) was repeated, and the second reversion amount (g) and the third reversion amount (g) were measured. Tables 8 and 10 show the total of the measured reversion amounts from the first to the third.
  • La is the thickness from the liquid absorbing surface of the upper nonwoven fabric (liquid absorbing surface of the first substrate) to the surface of the lower nonwoven fabric (second substrate) on the water absorbing layer side in the gap
  • Lb is the particulate water absorption. It is the thickness from the liquid-absorbing surface of the upper non-woven fabric (the liquid-absorbing surface of the first base material) to the surface of the lower non-woven fabric (the second base material) on the water-absorbing layer side in the region containing the agent.
  • the thickness from the liquid-absorbing surface of the upper non-woven fabric to the surface of the lower non-woven fabric on the water-absorbing layer side in the gap under the upper non-woven fabric is La
  • the thickness of the upper non-woven fabric in the region under the upper non-woven fabric containing the particulate water-absorbing agent is defined as La
  • the thickness from the liquid absorbing surface to the surface of the lower nonwoven fabric on the water absorbing layer side was defined as Lb.
  • the upper non-woven fabric and the lower non-woven fabric are mainly present.
  • X Regions containing a small amount of gaps and parallel particulate water absorbents are connected (not separated by gaps). (That is, the particle-like water-absorbing agent has entered the region that was the gap, and the proportion of the base material that holds the water-absorbing layer has decreased.)
  • Tables 7 to 10 below show the configurations of the water-absorbent sheets produced in Examples 1 to 10 and Comparative Examples 1 to 4, the evaluation results of the physical properties of the base material used in each water-absorbent sheet, and the evaluation results of the water-absorbent sheet. Is shown.
  • SAP means a particulate water absorbing agent.
  • the SAP arrangement region (%) in Tables 7 and 9 is the area ratio of the region containing the particulate water absorbent to the total area of the base material on which the particulate water absorbent is arranged in the plane direction of the upper non-woven fabric.
  • the SAP non-arranged region (%) is the area ratio of the region (that is, the gap) not containing the particulate water-absorbing agent to the total area of the base material on which the particulate water-absorbing agent is arranged in the plane direction of the upper non-woven fabric.
  • the base material on which the particulate water absorbing agent is arranged means a base material on which the particulate water absorbing agent is sprayed.
  • the upper non-woven fabric, the intermediate non-woven fabric, and the lower non-woven fabric have the same size.
  • the water-absorbent sheets of Examples 1 to 10 had higher shape retention and a significantly smaller amount of reversion as compared with the water-absorbent sheets of Comparative Examples 1 to 4. That is, it was confirmed that in the single-layer and two-layer water-absorbent sheets, the amount of reversion can be reduced and the shape-retaining property is high by providing a gap in the water-absorbent layer by using an upper non-woven fabric having elasticity. ..
  • the amount of reversion tends to be larger in the two-layer form than in the single-layer form.
  • the amount of the particulate water-absorbing agent for the two-layered upper-layer non-woven fabric that is, the amount of the particulate water-absorbing agent located between the upper nonwoven fabric and the intermediate nonwoven fabric
  • the particulate water-absorbing agent for the single-layered upper-layer nonwoven fabric is the particulate water-absorbing agent for the single-layered upper-layer nonwoven fabric. (That is, the amount of the particulate water-absorbing agent located between the upper non-woven fabric and the lower non-woven fabric) may be one of the factors. Therefore, it is difficult to make a general comparison of the difference in the effect of reducing the amount of reversion between the single-layer form and the two-layer form.
  • Water-absorbent sheet 11 11a First base material, 11b Intermediate base material, 12, 12a, 12b water absorption layer, 13 Second base material, 14, 14a, 14b particulate water absorbent, 15, 15a, 15b gap 16 wrapping sheet, 18, 18a laminate, 18b construct, 20 water-absorbent sheet, 21 Liquid opaque sheet, 31 sieve, 31a Below the mesh of the sieve, 32 mesh, 33 Tape 41 Liquid injection tube, 42 funnel, 43 Filter paper 44 Weight, 45 liquid injection tube, 60 pedestals, 61 pipe, 63 Acrylic board, 64 funnel, 65 Metal tray.

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