EP1429703A2 - Structure absorbante, article absorbant, resine absorbant l'eau et sa production - Google Patents

Structure absorbante, article absorbant, resine absorbant l'eau et sa production

Info

Publication number
EP1429703A2
EP1429703A2 EP02799478A EP02799478A EP1429703A2 EP 1429703 A2 EP1429703 A2 EP 1429703A2 EP 02799478 A EP02799478 A EP 02799478A EP 02799478 A EP02799478 A EP 02799478A EP 1429703 A2 EP1429703 A2 EP 1429703A2
Authority
EP
European Patent Office
Prior art keywords
liquid
water
absorbent resin
absorbent
height
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02799478A
Other languages
German (de)
English (en)
Inventor
Kinya Nagasuna
Kenji Kadonaga
Akiko Mitsuhashi
Motohiro Imura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Shokubai Co Ltd
Original Assignee
Nippon Shokubai Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nippon Shokubai Co Ltd filed Critical Nippon Shokubai Co Ltd
Publication of EP1429703A2 publication Critical patent/EP1429703A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L101/00—Compositions of unspecified macromolecular compounds
    • C08L101/12—Compositions of unspecified macromolecular compounds characterised by physical features, e.g. anisotropy, viscosity or electrical conductivity
    • C08L101/14—Compositions of unspecified macromolecular compounds characterised by physical features, e.g. anisotropy, viscosity or electrical conductivity the macromolecular compounds being water soluble or water swellable, e.g. aqueous gels
    • 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
    • A61F13/15203—Properties of the article, e.g. stiffness or absorbency
    • 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
    • A61F13/537—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 characterised by a layer facilitating or inhibiting flow in one direction or plane, e.g. a wicking layer
    • A61F13/5376—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 characterised by a layer facilitating or inhibiting flow in one direction or plane, e.g. a wicking layer characterised by the performance of the layer, e.g. acquisition rate, distribution time, transfer time
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
    • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
    • A61L15/42—Use of materials characterised by their function or physical properties
    • A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/12—Powdering or granulating
    • 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
    • A61F13/15203—Properties of the article, e.g. stiffness or absorbency
    • A61F2013/15284—Properties of the article, e.g. stiffness or absorbency characterized by quantifiable properties
    • A61F2013/15463—Absorbency
    • 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
    • A61F13/15203—Properties of the article, e.g. stiffness or absorbency
    • A61F2013/15284—Properties of the article, e.g. stiffness or absorbency characterized by quantifiable properties
    • A61F2013/15487—Capillary properties, e.g. wicking
    • 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
    • A61F13/15203—Properties of the article, e.g. stiffness or absorbency
    • A61F2013/15284—Properties of the article, e.g. stiffness or absorbency characterized by quantifiable properties
    • A61F2013/15487—Capillary properties, e.g. wicking
    • A61F2013/1552—Capillary properties, e.g. wicking with specific diffusion velocity
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2300/00—Characterised by the use of unspecified polymers
    • C08J2300/14—Water soluble or water swellable polymers, e.g. aqueous gels
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
    • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
    • G01N5/02—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content
    • G01N5/025—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content for determining moisture content

Definitions

  • the present invention relates to: an absorbent structure, an absorbent article, and a water-absorbent resin, which are fitly used for such as sanitary materials (e.g. disposable diapers, sanitary napkins, and so-called incontinent pads), dew-absorbent sheets, water-retaining materials for agricultural and horticultural fields, water-holding materials for building fields, medical materials (e.g. medical sheets), freshness-retaining materials for foods, and drip-absorbing materials for foods; and its production process and evaluation method.
  • sanitary materials e.g. disposable diapers, sanitary napkins, and so-called incontinent pads
  • dew-absorbent sheets water-retaining materials for agricultural and horticultural fields
  • water-holding materials for building fields water-holding materials for building fields
  • medical materials e.g. medical sheets
  • freshness-retaining materials for foods e.g. medical sheets
  • drip-absorbing materials for foods e.g., and its production process and evaluation method.
  • hydrophilic fibers e.g. pulp
  • water-absorbent resins which are water-swellable crosslinked polymers as obtained from such as an acrylic acid (salt) as a major raw material
  • sanitary materials such as disposable diapers, sanitary napkins, and so-called incontinent pads
  • these sanitary materials improve in high function and thinning.
  • the amount of the water-absorbent resin as used per one sanitary material sheet and the weight ratio of the water-absorbent resin relative to the entire absorbent structure including such as the water-absorbent resin and the hydrophilic fiber tend to increase.
  • the ratio of the water-absorbent resin in the absorbent structure is increased by making the amount of the hydrophilic fiber having a small bulk density decrease, and by using the water-absorbent resin having excellent water absorbency and a large bulk density in a large amount. Thereby, the thinning of the sanitary material is attempted without lowering the water absorption quantity.
  • the above matter is a favorable course, from the viewpoint such that: the ratio of the hydrophilic fiber is lowered in such a manner; and the sanitary material in which the amount of the water-absorbent resin is increased simply stores a liquid, but on the contrary, it causes problems when the distribution and diffusion of the liquid are thought in a circumstance of practically using diapers.
  • the water-absorbent resin in a large amount becomes a soft gel due to absorbing water. Therefore, caused is so-called gel blocking, which is a phenomenon such that the diffusion of liquids is greatly hindered.
  • the ratio between the hydrophilic fiber and the water-absorbent resin is naturally limited, and the limitation of thinning the sanitary material is also caused.
  • methods for distributing and diffusing a liquid, or liquid-diffusing members have hitherto been variously considered, and absorbent articles including these members have been variously known.
  • Examples of these include: an absorbent pad in which a specific region of a hydrophilic fiber in an absorbent structure is compressed in a high density (USP 4,781,710); a liquid-distributing material having specific suction properties, which is obtained by molding and combining at least two kinds of fibers having different strength and specific surface area in a wet condition (WO 97/45087); a form-type absorbent material having continuous foam, which is produced by using a high-internal-phase emulsion (USP 5,387,207, USP 5,134,007, and USP 6,107,538); and an absorbent core, which favorably has a narrow crotch width including a form-type absorbent material having continuous foam, and in which the absorption ability of the crotch region is not more than 40 % of that of the entire absorption ability ofthe absorbent core (WO 98/43573 and JP-A-510365/2000).
  • a liquid-acquiring member examples include: crosslinked cellulose (JP-A-264971/1988); and an exhaust-treating layer having a specific liquid permeation ratio index (JP-A-261126/1993).
  • WO 99/47184 and USP 6107538 disclose a liquid-storing member having high capillary absorption ability, which is obtained by combining an absorbent material due to osmotic pressure (e.g. the above water-absorbent resin) with a material having a large surface area (e.g. a particulate porous-foam-type absorbent material which is produced by using the above high-internal-phase emulsion and has continuous foam, and a glass micro fiber).
  • an absorbent material due to osmotic pressure e.g. the above water-absorbent resin
  • a material having a large surface area e.g. a particulate porous-foam-type absorbent material which is produced by using the above high-internal-phase emulsion and has continuous foam, and a glass micro fiber.
  • the liquid is rapidly captured into the absorbent structure in an initial state by making the liquid-acquiring member to exist.
  • the absorbent structure including such as the water-absorbent resin and the hydrophilic fiber cannot absorb the liquid in the liquid-acquiring member, and the absorption rate becomes slow conversely, and the amount of wet back ofthe aqueous liquid is increased.
  • the weight thereof is yet still heavy, and the thickness thereof is thick. Therefore, it is yet still unsatisfactory for such as circulation of goods, displaying space, purchase, and outdoor use, and further thinning is requested.
  • Known examples of arts of using the water-absorbent resin layer including the water-absorbent resin in a major proportion as the liquid-storing member include: an absorbent core as equipped with a first structure and a second structure, wherein the first structure includes a first fiber material and a first super-absorbent material, and wherein the second structure includes a second fiber material and a second super-absorbent material of which the absorption rate is faster than that of the first super-absorbent material (JP-A-511973/1996); an absorbent structure having an upper constituted structure and a lower constituted structure having a special structure, wherein the upper constituted structure includes a liquid-capturing layer and a super-absorbent material layer that is comprised of a super-absorbent material having a gel layer permeation value of not less than a specific amount, and wherein the lower constituted structure includes an upper layer having an opening space for storing a liquid, and a lower layer storing a super-absorbent material layer of which
  • JP-A-511973/1996 and JP-A-511974/1996 disclosed are the art relating to the constitution of the absorbent structure, in which the liquid-storing position in the absorbent structure is transferred from downward to upward.
  • JP-A-286505/2000 disclosed is the art in which the roughness of a back sheet in a diaper is removed.
  • WO 01/30290 disclosed is the art in which the opening ratio of the absorbent structure in a swollen state is defined.
  • the distribution relationship of the liquid between the liquid-acquiring member and the water-absorbent resin layer that catch the liquid is not mentioned.
  • the polymer as used in this case is a polymer having a comparatively small bulk density and a high unshaping degree, and the so-called absorption rate of rapidly absorbing the liquid as retained in the pulp space around the polymer is regarded as an important matter, and similarly the distribution relationship of the liquid between the liquid-acquiring member and the water-absorbent resin layer is not disclosed.
  • an object of the present invention is to provide: an absorbent structure and an absorbent article, in which, in the absorbent structure and the absorbent article comprising a liquid-diffusing member and a water-absorbent resin, a liquid is sufficiently transferred and absorbed from the liquid-diffusing member to the water-absorbent resin even if an auxiliary material such as a material having a large surface area is not used, namely which are excellent in both liquid diffusion ability and liquid storage ability; and a water-absorbent resin fitly usable for the above absorbent structure and absorbent article, and the object is to provide: an absorbent structure and an absorbent article, in which, in the absorbent structure and the absorbent article comprising a liquid-acquiring member and a water-absorbent resin, a liquid is favorably transferred from the liquid-acquiring member to the water-absorbent resin even if the concentration of the
  • the water-absorbent resin can favorably absorb the liquid from the liquid-diffusing member and can favorably absorb the liquid from the liquid-acquiring member.
  • the capillary absorption ability is measured by an apparatus of which the rough drawing is shown in Fig. 1, and is obtained by a process including the steps of: arranging a measuring sample (water-absorbent resin) in a position higher than the liquid surface of a physiological saline in a liquid-storing receptacle by several tens centimeters; and measuring capillary absorption ability of sucking up a liquid against a negative pressure as caused by water column at the height.
  • the absorbent structure and the absorbent article are produced by using the water-absorbent resin having performance such that the above relationships are maintained depending upon the properties of the liquid-diffusing member or liquid-acquiring member, the system as called the diffusion to the storage of the liquid in the absorbent structure, the acquirement to the storage, or the acquirement to the storage and diffusion favorably works; and the absorbent structure and the absorbent article displaying very excellent liquid absorption ability can be provided by a very simple production process. Then, the present invention has been completed.
  • a water-absorbent resin fine powder can be extremely efficiently granulated, and water-absorbent resin particles having strong adhesion and re-diSpersibility and being fitly usable for the present invention absorbent structure and absorbent article are easily obtained and have excellent absorption properties.
  • an absorbent structure comprises a liquid-diffusing member and a water-absorbent resin, with the absorbent structure being characterized in that when the capillary absorption index of the liquid-diffusing member at a height of 40 cm is referred to as A (A ⁇ 0.10), the capillary absorption index B of the water-absorbent resin at a height of 40 cm satisfies the following equation:
  • Another absorbent structure comprises a liquid-diffusing member and a water-absorbent resin, with the absorbent structure being characterized in that when the capillary absorption capacity of the liquid-diffusing member at a height of 40 cm is referred to as C (C ⁇ 2.0 (g/g)), the capillary absorption capacity D of the water-absorbent resin at a height of 40 cm satisfies the following equation:
  • Yet another absorbent structure comprises a liquid-diffusing member and a liquid-storing member, with the absorbent structure being characterized in that: a member displaying a suction height of not lower than 30 cm is used as the liquid-diffusing member; and a water-absorbent resin displaying a capillary absorption capacity D of not less than 15 (g/g) at a height of 40 cm is used as the liquid-storing member.
  • Yet another absorbent structure comprises a liquid-diffusing member and a liquid-storing member, with the absorbent structure being characterized in that: a member displaying a suction height of not lower than 30 cm is used as the liquid-diffusing member; and a surface-crosslinking-treated water-absorbent resin having a weight-average particle diameter of not larger than 250 ⁇ m is used as the liquid-storing member.
  • Yet another absorbent structure comprises a liquid-diffusing member and a water-absorbent resin including a crosslinked poly(acrylic acid (salt)) polymer in a major proportion, with the absorbent structure being characterized in that: the liquid-diffusing member is a porous polymer obtained by a process including the step of polymerizing a high-internal-phase emulsion; and the weight ratio ofthe water-absorbent resin is in the range of 75 to 90 weight % relative to the total weight of the liquid-diffusing member and the water-absorbent resin.
  • Yet another absorbent structure comprises a liquid-acquiring member and a water-absorbent resin layer having a scattering amount of not smaller than 250 g/m 2 ofthe water-absorbent resin, with the absorbent structure being characterized in that when the capillary absorption index of the liquid-acquiring member at a height of 40 cm is referred to as E (E ⁇ 0.1), the capillary absorption index B of the water-absorbent resin at a height of 40 cm satisfies the following equation:
  • Yet another absorbent structure comprises a liquid-acquiring member and a water-absorbent resin layer having a scattering amount of not smaller than 250 g/m 2 ofthe water-absorbent resin, with the absorbent structure being characterized in that when the capillary absorption index of the liquid-acquiring member at a height of 40 cm is referred to as E (E ⁇ 0.1), the capillary absorption index F of the water-absorbent resin layer at a height of 40 cm satisfies the following equation: F/E ⁇ 10 (equation 4).
  • Yet another absorbent structure comprises a liquid-acquiring member and a water-absorbent resin layer having a scattering amount of not smaller than 250 g/m 2 ofthe water-absorbent resin, with the absorbent structure being characterized in that: the liquid-acquiring member displays a capillary absorption capacity G of not more than 1.0 (g/g) at a height of 40 cm; and a water-absorbent resin displaying a capillary absorption capacity D of not less than 5 (g/g) at a height of 40 cm is used as the water-absorbent resin.
  • Yet another absorbent structure comprises a liquid-acquiring member and a water-absorbent resin layer having a scattering amount of not smaller than 250 g/m 2 ofthe water-absorbent resin, with the absorbent structure being characterized in that: the liquid-acquiring member displays a capillary absorption capacity G of not more than 1.0 (g/g) at a height of 40 cm; and the water-absorbent resin layer displays a capillary absorption capacity H of not less than 5 (g/g) at a height of 40 cm.
  • An absorbent article comprises the absorbent structure according to the present invention.
  • Water-absorbent resin particles are obtained by a process including the step of granulating a water-absorbent resin having a weight-average particle diameter of 50 to 300 ⁇ m and displaying a space ratio of 30 to 50 % and an average space radius of 80 to 150 ⁇ m as to spaces between particles when saturation-swollen with a physiological saline (a 0.9 weight % aqueous NaCl solution) without load; with the water-absorbent resin particles being characterized by having a weight-average particle diameter as increased by not less than 50 % of that before the granulating step.
  • Another water-absorbent resin particles comprise a crosslinked poly(acrylic acid (salt)) polymer in a major proportion and display a capillary absorption capacity D of not less than 25 (g/g) at a height of 40 cm.
  • a production process for water-absorbent resin particles is characterized by comprising the step of adding a dispersion of water-dispersible fine particles to a water-absorbent resin, thereby increasing the weight-average particle diameter of the water-absorbent resin by not less than 50 %, wherein the water-absorbent resin has a weight-average particle diameter of 50 to 300 ⁇ m and displays a space ratio of 30 to 50 % and an average space radius of 80 to 150 ⁇ m as to spaces between particles when saturation-swollen with a physiological saline (a 0.9 weight % aqueous NaCl solution) without load.
  • An absorbent article comprises the water-absorbent resin particles according to the present invention.
  • a water-absorbent resin comprises a crosslinked poly(acrylic acid (salt)) polymer in a major proportion and displays a capillary absorption capacity D of not less than 25 (g/g) at a height of 40 cm.
  • An absorbent article comprises the water-absorbent resin according to the present invention.
  • An evaluation method for a water-absorbent resin comprises the step of measuring an absorption capacity for a liquid as absorbed by the water-absorbent resin within a predetermined time in a state where the liquid-absorbing position height HI is in a position higher than the liquid surface height H2 in a liquid-storing receptacle.
  • FIG. 1 is a schematic sectional view of a measurement apparatus as used for the measurement to determine the capillary absorption capacity and the capillary absorption index in the present invention.
  • the capillary absorption capacity at a height of 40 cm is measured with this apparatus.
  • Fig. 2 is a schematic sectional view of a measurement apparatus as used for the measurement to determine the capillary absorption capacity and the capillary absorption index in the present invention.
  • the capillary absorption capacity at a height of 0 cm and the absorption capacity of the water-absorbent resin under a load are measured with this apparatus.
  • Fig. 3 is a schematic perspective view of an absorbent article according to the present invention.
  • Fig. 4 is a schematic sectional view of an absorbent article according to the present invention.
  • Physiological saline 15 Liquid-storing receptacle
  • Plastic cylinder 10 Load (0.41 kPa (0.06 psi))
  • the capillary absorption ability as used in the present invention is generally an evaluation item that has been used hitherto in order to evaluate the absorbency of a material (e.g. paper and pulp) sucking up and absorbing a liquid by capillary action.
  • the liquid amount as absorbed per a unit weight of a sample is measured in a state where the liquid-absorbing position is changed to various heights by using an apparatus as mentioned below, and thereby evaluated are the capillary absorption capacity and liquid suction ability of the sample.
  • a specific measurement method of the capillary absorption capacity meaning the capillary absorption ability in the present invention is disclosed in examples as mentioned below in detail. Measurement methods based on the same principle are also disclosed in such as: Textile Research Journal Vol. 57, 356 (1967), "Absorbency” (Chatterjee, Textile, Science and Technology, Vol. 7, 1985), JP-A-052349/1996, and WO 99/47184.
  • an evaluation method for a water-absorbent resin in the present invention comprising the step of measuring an absorption capacity for a liquid as absorbed by the water-absorbent resin within a predetermined time in a state where the liquid-absorbing position height HI is in a position higher than the liquid surface height H2 in a liquid-storing receptacle, the above-mentioned method is applied first to the water-absorbent resin. From the resultant value, it is found that the liquid absorption ability of the water-absorbent resin from other base material such as a liquid-diffusing member or a liquid-acquiring member can be judged correctly.
  • the measurement is carried out in a state where the height difference between the liquid-absorbing position height HI and the liquid surface height H2 in the liquid-storing receptacle is favorably in the range of 20 to 60 cm, more favorably 30 to 50 cm
  • the capillary absorption ability in the present invention there are two kinds of a capillary absorption capacity and a capillary absorption index.
  • measured is an amount (capacity) of a liquid as absorbed by a sample within 30 minutes in a state where there is a height difference between the liquid-absorbing position and the liquid surface in a liquid-storing receptacle.
  • the capillary absorption index in the present invention can be calculated by dividing a value of the capillary absorption capacity (as absorbed by a sample within 30 minutes in a state where there is a height difference between the liquid-absorbing position and the liquid surface in the liquid-storing receptacle) by a value of the capillary absorption capacity at a height of 0 cm (as absorbed by the sample within 30 minutes when the height difference with the liquid surface in the liquid-storing receptacle is 0 cm).
  • the capillary absorption index at a height of 40 cm is calculated by dividing a value ofthe “capillary absorption capacity at a height of 40 cm” (when the height difference between the liquid-absorbing position and the liquid surface in the liquid-storing receptacle is 40 cm) by the value of the "capillary absorption capacity at a height of 0 cm” (when the height difference with the liquid surface in the liquid-storing receptacle is 0 cm).
  • Water-absorbent resins which are on a market at present and used for sanitary materials in a large amount, are crosslinked poly(acrylic acid (salt)) polymers of which the major raw material is an acrylic acid (salt).
  • the mechanism of absorbing a liquid is not by capillary absorption such as pulp, but it is fundamentally derived from the osmotic pressure difference between an absorbed liquid and the polymer itself that is a polymer electrolyte.
  • the ability of the water-absorbent resin to absorb a liquid from a liquid-diffusing member or liquid-acquiring member having excellent liquid suction ability in the vertical direction, wherein the liquid is kept in the above member could not be expected at all from only the absorption properties generally known as the ability of the water-absorbent resin hitherto, such as absorption capacity, absorption rate, absorption capacity under a load, and liquid permeability of gel layer.
  • the present inventors took note of and considered the ability as called the capillary absorption ability even in the water-absorbent resin similar to the liquid-diffusing member or liquid-acquiring member. Then, they found out that: the capillary absorption ability is greatly different due to the kinds of water-absorbent resins; and further, by using a combination of a water-absorbent resin and a liquid-diffusing member or liquid-acquiring member wherein the water-absorbent resin has capillary absorption ability specifically in relation to the capillary absorption ability of the above liquid-diffusing member or liquid-acquiring member, the water-absorbent resin can favorably absorb and store a liquid from the liquid-diffusing member or liquid-acquiring member.
  • an absorbent structure as planed to maintain this relationship displays very excellent liquid absorption efficiency; and, in an absorbent article (e.g. disposable diaper) including such an absorbent structure, a water-absorbent resin is spread all over and used very effectively, and therefore the absorption ability of the entire diaper can be very greatly enhanced; and a thin-type easily-movable diaper including fewer members can be produced by adjusting this high absorption ability to absorption ability in a desirable practical level.
  • the water-absorbent resin usable in the present invention is a water-absorbent resin wherein when the capillary absorption index of the liquid-diffusing member at a height of 40 cm is referred to as A (A ⁇ 0.10), the capillary absorption index B of the water-absorbent resin at a height of 40 cm satisfies the following equation: B/A ⁇ 0.7 (equation 1).
  • the value of the capillary absorption index B of the water-absorbent resin necessary in the present invention at a height of 40 cm is different depending upon the property ofthe liquid-diffusing member as used, namely, the capillary absorption index A of the liquid-diffusing member as used at a height of 40 cm. If the relationship B/A ⁇ 0.7 above is satisfied, a liquid from the liquid-diffusing member to the water-absorbent resin is favorably distributed, and the water-absorbent resin can favorably absorb and store the liquid.
  • the water-absorbent resin In the case where the B/A is less than 0.7, there are cases where: the water-absorbent resin difficultly absorbs the liquid from the liquid-diffusing member; and the liquid distribution ratio from the liquid-diffusing member is lowered; and the absorption quantity of the water-absorbent resin is not improved even if diapers include these absorbent structures. Therefore, the water-absorbent resin does not favorably work as the liquid-storing member.
  • the water-absorbent resin favorably satisfies B/A ⁇ 1.3, more favorably B/A ⁇ 1.5.
  • the value of the B/A may be referred to as a liquid-diffusion-and-storage coefficient 1.
  • another water-absorbent resin usable in the present invention is a water-absorbent wherein when the capillary absorption capacity of the liquid-diffusing member at a height of 40 cm is referred to as C (C ⁇ 2.0 (g/g)), the capillary absorption capacity D of the water-absorbent resin at a height of 40 cm satisfies the following equation:
  • the value of the capillary absorption capacity D of the water-absorbent resin necessary in the present invention at a height of 40 cm is different depending upon the property of the liquid-diffusing member as used, namely, the capillary absorption capacity C of the liquid-diffusing member as used at a height of 40 cm. Even if the relationship D/C ⁇ 0.7 above is satisfied, a liquid from the liquid-diffusing member to the water-absorbent resin is favorably distributed, and the water-absorbent resin can favorably absorb and store the liquid.
  • the water-absorbent resin difficultly absorbs the liquid from the liquid-diffusing member, and then the water-absorbent resin does not favorably work as the liquid-storing member.
  • the water-absorbent resin favorably satisfies D/C ⁇ 1.3, more favorably D/C ⁇ 1.5.
  • the D/C is more than 10
  • the liquid diffusion ratio of the liquid-diffusing member is lowered, and it is necessary to pay attention to this matter.
  • the value ofthe D/C may be referred to as a liquid-diffusion-and-storage coefficient 2.
  • both the liquid-diffusion-and-storage coefficient 1 and the liquid-diffusion-and-storage coefficient 2 as mentioned above satisfy the present invention range.
  • the liquid absorption ability of the water-absorbent resin from the liquid-diffusing member may not be displayed favorably due to a condition of use, and therefore it is necessary to pay attention to this matter.
  • the present invention relates to an absorbent structure comprising a liquid-diffusing member and a water-absorbent resin having a specific relationship, but the absorbent structure also works as a liquid-transfer-and-absorption system comprising a liquid-diffusing member and a water-absorbent resin having a specific relationship.
  • the present invention can also provide: a liquid-transfer-and-abso ⁇ tion system, which is an absorbent structure comprising a liquid-diffusing member and a water-absorbent resin, with the system being characterized in that when the capillary absorption index of the liquid-diffusing member at a height of 40 cm is referred to as A (A ⁇ 0.10), the capillary absorption index B of the water-absorbent resin at a height of 40 cm satisfies the following equation:
  • Equation 1 B/A ⁇ 0.7 (Equation 1); and a liquid-transfer-and-absorption system, which is an absorbent structure comprising a liquid-diffusing member and a water-absorbent resin, with the system being characterized in that when the capillary absorption capacity of the liquid-diffusing member at a height of 40 cm is referred to as C (C ⁇ 2.0 (g/g)), the capillary absorption capacity D at a height of 40 cm satisfies the following equation: D/C ⁇ 0.7 (Equation 2).
  • the liquid-diffusing member usable in the present invention is defined as a material displaying a capillary absorption index A of not less than 0.10 at a height of 40 cm and a capillary absorption capacity C of not less than 2.0 (g/g) at a height of 40 cm, and substantially having no hydrogel-formability.
  • the liquid-diffusing member is a material for diffusing a liquid as added to the absorbent structure or absorbent article having the absorbent structure, over a wider area in the absorbent structure. Particularly, even in a mode of practical use, in order to enable such a function to be displayed sufficiently, the liquid-diffusing member has a porous structure and excellent liquid suction ability in the vertical direction.
  • the liquid-diffusing member itself more favorably has a predetermined level of ability of retaining, absorbing and storing a liquid.
  • the liquid-diffusing member usable in the present invention is a member having excellent liquid diffusion ability and liquid suction ability, and it is necessary that the capillary absorption index A is not less than 0.10 at a height of 40 cm.
  • the capillary absorption index A of such as flap pulp as used for disposable diapers hitherto is not more than 0.05 at a height of 40 cm according to the measurement method in the present invention.
  • the capillary absorption index A is favorably not less than 0.20 at a height of 40 cm, more favorably not less than 0.30, most favorably not less than 0.40.
  • the liquid-diffusing member usable in the present invention favorably displays a capillary abso ⁇ tion capacity of not less than 10 (g/g) at a height of 0 cm.
  • the capillary absorption capacity is more favorably not less than 20 (g/g) at a height of 0 cm, still more favorably not less than 30 (g/g).
  • another liquid-diffusing member usable in the present invention displays a capillary absorption capacity C of not less than 2.0 (g/g) at a height of 40 cm.
  • the capillary absorption capacity C of such as flap pulp as used for disposable diapers hitherto is not more than 1.0 (g/g) at a height of 40 cm.
  • the liquid suction ability in the vertical direction is small, and it is difficult to diffuse a liquid over the entire face of the liquid-diffusing member or the entire absorbent structure, and the material ofthe entire absorbent structure cannot be efficiently used.
  • the capillary absorption capacity C is favorably not less than 5.0 (g/g) at a height of 40 cm, more favorably not less than 10.0 (g/g).
  • another liquid-diffusing member usable in the present invention favorably displays a capillary absorption capacity of not less than 10 (g/g) at a height of 0 cm.
  • the capillary absorption capacity is more favorably not less than 20 (g/g) at a height of 0 cm, still more favorably not less than 30 (g/g).
  • the liquid-diffusing member usable in the present invention satisfies the above conditions, and is used together with a water-absorbent resin, and thereby they are used as an absorbent structure.
  • A the capillary absorption index of the liquid-diffusing member at a height of 40 cm
  • B the capillary abso ⁇ tion index of the above water-absorbent resin at a height of 40 cm
  • C the capillary absorption capacity of the liquid-diffusing member at a height of 40 cm
  • C C ⁇ 2.0 (g/g)
  • the capillary absorption capacity D of the above water-absorbent resin at a height of 40 cm satisfies D/C ⁇ 0.7, favorably D/C ⁇ 1.3.
  • both of them more favorably satisfy the B/A ⁇
  • the liquid-diffusing member usable in the present invention favorably displays a suction height of not lower than 30 cm, more favorably not lower than 40 cm, still more favorably not lower than 50 cm, wherein the suction height is ability of sucking up a liquid in the vertical direction as mentioned below.
  • the suction height is not higher than 30 cm, the liquid diffusion ratio of the absorbent structure is low, and the entire absorbent structure cannot be utilized effectively.
  • the shape of the liquid-diffusing member can be a sheet, fibrous, particulate, or strip shape, but it is favorably a sheet shape in general. Then, the weight of the liquid-diffusing member per its unit area is in the range of about 50 to about 500 g /m 2 , about 100 to about 200 g /m 2 .
  • liquid-diffusing member has a difference of density, a slope of density, a difference of diffusion ability, and a slope of diffusion ability in the member, or when a second liquid-diffusing member not satisfying the present invention relationship is further used, it is favorable to make the capillary absorption ability of a portion of the liquid-diffusing member much closer to the water-absorbent resin satisfy the above relationship.
  • a liquid-diffusing member include: porous polymers obtained by a process including the step of polymerizing a high-internal-phase emulsion (HIPE); fibrous materials having a predetermined density (e.g. cellulose pulps or nonwoven fabrics); and foam materials (e.g. urethane sponges and cellulose sponges).
  • the liquid-diffusing member is favorably a member having excellent liquid suction ability, suction amount, and suction rate in the vertical direction.
  • the porous polymers obtained by a process including the step of polymerizing a high-internal-phase emulsion (HIPE) as explained below are favorable.
  • HIPE high-internal-phase emulsion
  • the porous polymer fitly usable as the liquid-diffusing member in the present invention can be obtained by a process including the step of polymerizing a high-internal-phase emulsion (HIPE), where the ratio of the water phase and the oil phase (W/O ratio) is not less than about 3/1 wherein the water phase is a dispersible (inner) phase and the oil phase is an outer phase.
  • HIPE high-internal-phase emulsion
  • W/O ratio the ratio of the water phase and the oil phase
  • the method for producing the porous polymer from the HIPE is, for example, described in such as USP 5,189,070, USP 5,250,576, USP 5,252,619, USP 5,290,820, USP 5,358,974, USP 5,252,619, USP 5,670,101, and USP 6,204,298.
  • the porous polymer as obtained in this way is in a state of low-density foam including continuous foam having a fine diameter. If conditions are selected, the polymer foam having desirable absorption properties (e.g. very excellent liquid diffusion and suction properties) can be produced.
  • the raw material of the HIPE as used includes: an oil phase containing a polymerizable monomer component and a surfactant; and a water phase containing water.
  • the polymerizable monomer component include: a polymerizable monomer having one polymerizable unsaturated group in its molecule wherein the monomer can form a crosslinked structure by polymerization; and/or a crosslinkable monomer having at least two polymerizable unsaturated groups in its molecule.
  • polymerization initiators, salts, and other additives may also be included as arbitrary components that are comprised in the oil phase and/or water phase.
  • the polymerizable monomer at least one portion thereof favorably includes a (meth)acrylate ester.
  • arylene monomers such as styrene
  • monoalkylene arylene monomers such as styrene, ethylstyrene, ⁇ -methylstyrene, vinyltoluene, and vinylethylbenzene
  • (meth)acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, isodecyl (meth)acrylate, 2-ethylehexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and benzyl (meth)acrylate; chlorine-containing monomers, such as vinyl chloride, vinylidene chloride,
  • the above crosslinkable monomer may be a compound having at least two polymerizable unsaturated groups in its molecule, or a compound that can form a crosslinked structure by polymerization.
  • the crosslinkable monomer if it is polymerizable in a dispersible emulsion or water-drop-in-oil-type high-dispersible-phase emulsion in the same way as of the above polymerizable monomer.
  • crosslinkable monomer examples include: aromatic monomers, such as divinylbenzene, trivinylbenzene, divinyltoluene, divinylxylene, p-ethyl-vinylbenzene, divinylnaphthalene, divinylalkylbenzenes, divinylphenathrene, divinylbiphenyl, divinyldiphenylmethane, divinylbenzil, divinyl phenyl ether, and divinyl phenyl sulfide; oxygen-containing monomers such as divinylfuran; sulfur-containing monomers, such as divinyl sulfide and divinyl sulfone; aliphatic monomers, such as butadiene, isoprene, and pentadiene; ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate,
  • the amount of the above crosslinkable monomer as used is favorably in the range of 0.1 to 90 weight %, more favorably 1 to 70 weight %, particularly favorably 5 to 50 weight %, of the weight of the entire polymerizable monomer component including the above polymerizable monomer and the above crosslinkable monomer.
  • the surfactant as used in the oil phase if it can emulsify the water phase.
  • Such as nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants that are publicly known hitherto can be used.
  • nonionic surfactants cationic surfactants, anionic surfactants, and amphoteric surfactants that are publicly known hitherto
  • amphoteric surfactants that are publicly known hitherto can be used.
  • the stability ofthe HIPE is improved when the nonionic surfactants are used together with the cationic surfactants.
  • the amount ofthe above surfactant as used is favorably in the range of 1 to 30 parts by weight, more favorably 3 to 15 parts by weight, per 100 parts by weight of the entire polymerizable monomer component including the polymerizable monomer and the crosslinkable monomer.
  • the porous ratio of the porous polymer is determined by changing the ratio of water phase/oil phase (W/O) of the HIPE. Therefore, the amount of the water as used is naturally determined if the W/O ratio is selected so that the porous ratio will accord with the aim.
  • the polymerization initiators may be initiators usable in ordinary polymerization, and any of water-soluble polymerization initiators (e.g. azo compounds such as 2,2'-azobis(2-amidinopropane) dihydrochloride; persulfate salts, such as ammonium persulfate, potassium persulfate, and sodium persulfate; peroxides, such as potassium peracetate, sodium peracetate, potassium percarbonate, and sodium percarbonate) and oil-soluble polymerization initiators can be used. Furthermore, a redox polymerization initiator system as obtained by combining the above polymerization initiator and a reductant may be used.
  • water-soluble polymerization initiators e.g. azo compounds such as 2,2'-azobis(2-amidinopropane) dihydrochloride
  • persulfate salts such as ammonium persulfate, potassium persulfate, and sodium persulfate
  • peroxides such as potassium pera
  • any of the water-soluble initiator or the oil-soluble initiator can be used, and the water-soluble redox polymerization initiator system may be used together with the oil-soluble redox polymerization initiator system.
  • the salts may be used if it is necessary to improve the stability ofthe HIPE.
  • Specific examples ofthe salts include water-soluble salts such as halides, sulfate salts, and nitrate salts of alkaline or alkaline earth metals (e.g. calcium chloride, sodium sulfate, sodium chloride, and magnesium sulfate). These salts may be used either alone respectively or in combinations with each other. These salts are favorably added to the water phase.
  • multivalent metal salts are favorable in view ofthe stability ofthe HIPE when the polymerization is carried out.
  • the amount of such salts as used is favorably in the range of 0.1 to 20 parts by weight, more favorably 0. 5 to 10 parts by weight, per 100 parts by weight of the water.
  • additives may fitly be used.
  • bases and/or buffers may be added in order to adjust a pH.
  • examples of such additives include active carbon, inorganic powders, organic powders, metal powders, deodorants, antimicrobial agents, anti-molding agents, perfumes, various polymers, and surfactants.
  • a uniform oil phase is prepared by stirring an oil-phase constituent component at a definite temperature wherein the component includes such as the polymerizable monomer component and surfactant, and the polymerization initiator and other additives that can be further added thereto if necessary.
  • a uniform water phase is prepared by: stirring water with an objective amount as used while a water-phase constituent component is further added to the water wherein the component includes such as the polymerization initiators, salts, and other additives that can be further added thereto if necessary; and heating them at a predetermined temperature of the HIPE.
  • the HIPE can stably be prepared by: combining the oil phase and the water phase, wherein the oil phase is a mixture of such as a polymerizable monomer component and surfactant, and the water phase is a mixture of such as water and a water-soluble salt as prepared in the above way; efficiently mix-stirring them at an emulsifying temperature of the HIPE to apply the optimum shearing stress; and then emulsifying them.
  • the ratio of water phase/oil phase (W/O) (weight ratio) can fitly be selected and is not especially limited.
  • the ratio may be not less than 3/1 as defined before, but it is favorably in the range of 10/1 to 250/1, particularly favorably 10/1 to 100/1.
  • the porous ratio of the porous polymer is determined by changing the W/O ratio, and thereby the liquid distribution ability, liquid suction ability, and liquid-retaining ability of the liquid-diffusing member can be changed. Therefore, when the liquid-diffusing member as an object of the present invention is produced, the W/O ratio is in the range of about 10/1 to about 100/1, more favorably about 20/1 to about 80/1. There is no especial limitation on production apparatuses of the above
  • HIPE HIPE
  • the hitherto known production apparatuses include stirrers having such as a propeller-type, paddle-type, and turbine-type blade, homomixers, pin mixers, line mixers, and static mixers. These may be used either alone respectively or in combinations with each other.
  • the emulsifying temperature ofthe HIPE in the emulsifying step in which the HIPE is formed is usually in the range of 40 to 110 °C.
  • the HIPE as obtained by mixing the polymerization initiator is formed in a desirable mode.
  • the molding shape is favorably a sheet shape in order to use the porous polymer as the liquid-diffusing member wherein the porous polymer is obtained in the present invention, but the HIPE is added to a cylindrical container to polymerize it and thereafter the resultant polymer may be cut into a sheet shape, or porous polymers having various modes (e.g. particulate, fibrous, and film shape) may be processed to a mode having liquid distribution ability as an end product.
  • the thickness thereof is not limited, but the thickness as the mode of the end product is favorably not more than about 10 mm, more favorably not more than about 5 mm, still more favorably not more than about 3 mm, particularly favorably not more than about 1 mm, most favorably not more than about 0.5 mm.
  • the attachment feeling may be lowered when it is used as a liquid-diffusing member for absorbent articles.
  • the HIPE is usually polymerized by heating with a static polymerization method under a condition that the structure in the HIPE is not destroyed.
  • the batchwise polymerization in which this HIPE is polymerized every batch, or the continuous polymerization in which this HIPE is continuously polymerized by casting, for example, while feeding it into a heating zone may be carried out.
  • the above polymerization temperature is usually in the range of 40 to 110 °C. However, when the productivity is considered, the above polymerization temperature is favorably higher (e.g.
  • the polymerization time is favorably in the range of several tens seconds to 30 minutes in order to obtain a porous polymer having uniform properties in view of the productivity.
  • the porous polymer as obtained after the polymerization is usually dehydrated by compression, aspiration under reduced pressure, or a combination of these, and the polymer can be pressed in a mode such that the polymer is compressed to one half or third of the original thickness depending upon the its kind.
  • the porous polymer may be washed in an aqueous solution or a solvent including pure water and an arbitrary additive, or thereafter if necessary, the polymer may be heat-dried by such as hot air, infrared ray, microwave.
  • the water content ofthe resultant polymer may be adjusted by adding humidity.
  • the polymer is cut to obtain a desirable shape and size for using as an end product, and then it may be processed to obtain a product in accordance with various uses.
  • Other liquid-diffusing member is usually dehydrated by compression, aspiration under reduced pressure, or a combination of these, and the polymer can be pressed in a mode such that the polymer is compressed to one half or third of the original thickness depending upon the its kind.
  • liquid-diffusing member examples include: foaming structures including synthetic polymers, such as polyurethanes, polystyrene, polyethylene, polypropylene, polyesters, poly(vinyl alcohol), butadiene-styrene rubbers (SBR), and nitrile-butadiene rubbers; fibrous aggregates as obtained by adhering to or combining with synthetic fibers, such as polyethylene, polypropylene, polyethylene terephtHalate, and nylon; rayon fibers; and fibrous aggregates as obtained by adhering to under a pressure, adhering to, or combining with hydrophilic fibers, such as cellulose fibers (e.g.
  • celluloses celluloses, cellulose acetate, and nitro cellulose
  • polyamide fibers The shape thereof can be a sheet, fibrous, or particulate shape, but it is favorably a sheet shape in general.
  • fibrous aggregates as obtained by adhering to under a pressure, adhering to, or combining with hydrophilic fibers, such as cellulose fibers and rayon fibers.
  • the present invention water-absorbent resin is a hydrophilic crosslinked polymer, namely a polymer (water-swellable water-insoluble hydrogel-formable polymer) having a property such that: when an aqueous liquid contact is in contact with such as a particulate polymer aforementioned, the above polymer particles are swollen by absorbing the above liquid in the particles, and a hydrogel including the aqueous liquid can be formed.
  • the water-absorbent resin may include a mixture as obtained by adding an additive to the water-swellable water-insoluble hydrogel-formable polymer, wherein the amount of the additive is not more than 30 weight % relative to the total amount of the above water-swellable water-insoluble hydrogel-formable polymer and the above additive.
  • Water-absorbent resins have hitherto been used as materials absorbing liquids due to the osmotic pressure difference between the inside and the outside of the resins, namely as liquid-storing members such as disposable diapers.
  • the present inventors took note of that: even if the properties of the water-absorbent resins as known hitherto (e.g. absorption capacity, absorption capacity under a load) are identical, the absorbing behaviors are greatly different due to the kinds of resins when liquids are absorbed from such as the liquid-diffusing member.
  • the capillary absorption ability is greatly different even in a water-absorbent resin itself; and the water-absorbent resin can receive and store a liquid from the liquid-diffusing member more favorably when the relationship between the capillary absorption ability of the liquid-diffusing member and the capillary absorption ability of the water-absorbent resin satisfies a specific condition.
  • the water-absorbent resin usable in the present invention is a water-absorbent resin, in which, as is mentioned above, when the capillary absorption index ofthe liquid-diffusing member at a height of 40 cm is referred to as A (A ⁇ 0.10), the capillary absorption index B of the above water-absorbent resin at a height of 40 cm satisfies B/A ⁇ 0.7, favorably B/A ⁇ 1.3, more favorably B/A ⁇ 1.40.
  • the value of the capillary absorption index B of the water-absorbent resin necessary in the present invention at a height of 40 cm is different depending upon the property ofthe liquid-diffusing member as used, namely, the capillary absorption index A of the liquid-diffusing member as used at a height of 40 cm. If the above relationship B/A ⁇ 0.7 is satisfied, a liquid from the liquid-diffusing member to the water-absorbent resin is favorably distributed, and the water-absorbent resin can favorably absorb and store the liquid.
  • the water-absorbent resin displays a capillary absorption index B of not less than 0.4 at a height of 40 cm, favorably not less than 0.5, more favorably not less than 0.6.
  • the water-absorbent resin as used in the present invention favorably displays a capillary absorption capacity of not less than 30 (g/g) at a height of 0 cm. If the capillary absorption capacity at a height of 0 cm is higher, the water-absorbent resin can retain a large amount of liquid as sucked up from the liquid-diffusing, member. Therefore, an excellent absorbent structure is obtained from the viewpoint of the liquid abso ⁇ tion ability.
  • the water-absorbent resin favorably displays a capillary absorption capacity of net less than 40 (g/g) at a height of 0 cm, more favorably not less than 50 (g/g).
  • another water-absorbent resin usable in the present invention is a water-absorbent resin, in which, when the capillary absorption capacity of the liquid-diffusing member at a height of 40 cm is referred to as C (C ⁇ 2.0 (g/g)), the capillary absorption capacity D of the above water-absorbent resin at a height of 40 cm satisfies D/C ⁇ 0.7, favorably D/C ⁇ 1.3, more favorably D/C ⁇ 1.40.
  • the value of the capillary absorption capacity D of another water-absorbent resin necessary in the present invention at a height of 40 cm is different depending upon the property of the liquid-diffusing member as used, namely, the capillary absorption capacity C ofthe liquid-diffusing member as used at a height of 40 cm. Even if the above relationship D/C ⁇ 0.7 is satisfied, a liquid from the liquid-diffusing member to the water-absorbent resin is favorably distributed, and the water-absorbent resin can favorably absorb and store the liquid.
  • the water-absorbent resin favorably displays a capillary absorption capacity D of not less than 15 (g/g) at a height of 40 cm, more favorably not less than 20 (g/g), still more favorably not less than 25 (g/g), most favorably not less than 30 (g/g).
  • the water-absorbent resin as used in the present invention favorably displays a capillary absorption capacity of not less than 30 (g/g) at a height of 0 cm. If the capillary absorption capacity at a height of 0 cm is higher, the water-absorbent resin can retain a large amount of liquid as sucked up from the liquid-diffusing member. Therefore, an excellent absorbent structure is obtained from the viewpoint of the liquid absorption ability.
  • the water-absorbent resin favorably displays a capillary absorption capacity of not less than 40 (g/g) at a height of 0 cm, more favorably not less than 50 (g/g).
  • the water-absorbent resin as used in the present invention displays an absorption capacity of 20 to 50 g/g under a load of 2.07 kPa (0.3 psi), there are advantages in that the absorbency can favorably be maintained even if the absorbent structure is in a pressurized state.
  • the water-absorbent resin more favorably displays an absorption capacity of 25 to 40 g/g.
  • the water-absorbent resin usable in the present invention satisfies the above conditions, and is used together with a liquid-diffusing member, and thereby they are used as an absorbent structure.
  • the shape of the water-absorbent resin can be a particulate, fibrous, sheet, or strip shape, but it is favorably a particulate shape in general.
  • the water-absorbent resin is favorably a particulate resin, of which the raw material is an acrylic acid (salt) in a major proportion, and of which the weight-average particle diameter of the fundamental particles is not larger than 250 ⁇ m, and the water-absorbent resin favorably has narrow particle diameter distribution.
  • aqueous solution polymerization or reversed-phase suspension polymerization can be carried out, but the water-absorbent resin is favorably a resin obtained by the reversed-phase suspension polymerization.
  • the water-absorbent resin comprised of the fundamental particles is granulated while the capillary absorption ability of the present invention is maintained, and the weight-average particle diameter may be outside ofthe above range.
  • a water-absorbent resin satisfying the above relationship and a water-absorbent resin not satisfying the above relationship may be used together as the water-absorbent resin, but only the water-absorbent resin satisfying the above relationship is favorably used in order to display the present invention effect to the maximum.
  • the resin is favorably arranged so that the capillary absorption ability of a portion of the water-absorbent resin will satisfy the above relationship, wherein the portion is much closer to the liquid-diffusing member.
  • water-absorbent resin usable in the present invention examples include water-swellable crosslinked polymers that can be obtained by polymerizing hydrophilic monomers.
  • crosslinked poly(acrylic acid (salt)) polymers of which the major component is derived from acrylic acid or its salt are favorable.
  • Specific examples thereof include: partially-neutralized crosslinked poly(acrylic acid) polymers (e.g.
  • the acid group in the polymers is favorably neutralized in a ratio of 50 to 90 mol %
  • the salt include alkaline metal salts, ammonium salts, and amine salts.
  • the water-absorbent resin usable in the present invention may be obtained by copolymerizing monomers as used in a major proportion (e.g. acrylic acid or its salt), and besides, other monomers together if necessary.
  • Examples of other monomers include: anionic unsaturated monomers, such as methacrylic acid, maleic acid, vinylsulfonic acid, styrenesulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, 2-(meth)acryloylethanesulfonic acid, and 2-(meth)acryloylpropanesulfonic acid, and salts thereof; nonionic hydrophilic-group-containing unsaturated monomers, such as acrylamide, methacrylamide, N-ethyl(meth)acrylamide, N-n-propyl(meth)acrylamide,
  • the amount of the other monomers other than the acrylic acid as used is favorably in the range of 0 to 30 mol %, more favorably
  • Examples of the method for introducing a crosslinked structure into the water-absorbent resin as used in the present invention include: a self-crosslinking-type method in which no crosslinking agent is used; and a method which involves copolymerizing or reacting with an internal-crosslinking agent having at least two polymerizable unsaturated groups or at least two reactive groups.
  • a self-crosslinking-type method in which no crosslinking agent is used
  • an internal-crosslinking agent having at least two polymerizable unsaturated groups or at least two reactive groups.
  • these internal-crosslinking agents include: N,N'-methylenebis(meth)acrylamide, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane di(meth)acrylate, glycerol tri(meth)acrylate, glycerol acrylate methacrylate, ethylene-oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly(meth)allyloxyalkanes, (poly)ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol
  • these internal-crosslinking agents may be used in combinations with each other.
  • the compound having at least two polymerizable unsaturated groups is essentially used.
  • the amount as used is favorably in the range of 0.005 to 3 mol %, more favorably 0.01 to 1.5 mol %, ofthe aforementioned monomer component.
  • hydrophilic polymers e.g. starch-cellulose, derivatives from starch-cellulose; polyvinyl alcohol, polyacrylic acid (salts), and crosslinked products of polyacrylic acid (salts)
  • chain transfer agents e.g. hypophosphorous acid (salts)
  • aqueous solution polymerization or reversed-phase suspension polymerization is favorably carried out by using the above monomer in the form of its aqueous solution.
  • the above polymerization method is publicly known hitherto and disclosed in such as USP 4,625,001, USP 4,769,427, USP 4,873,299, USP 4,093,776, USP 4,367,323, USP 4,446,261, USP 4,683,274, USP 4,690,996, USP 4,721,647, USP 4,738,867, and USP 4,748,076.
  • radical polymerization initiators e.g. potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, and 2,2'-azobis(2-amidinopropane) dihydrochloride
  • active energy rays e.g. ultraviolet rays and electron beams
  • reductants e.g. sodium sulfite, sodium hydrogensulfite, ferrous sulfate, and L-ascorbic acid
  • the amount of these polymerization initiators as used is usually in the range of 0.001 to 2 mol %, favorably 0.01 to 0.5 mol %.
  • the particle shape of the water-absorbent resin as obtained by the above polymerization is generally such as irregular pulverized, spherical, fibrous, bar, almost spherical, or flat shape.
  • the water-absorbent resin as used in the present invention wherein the water-absorbent resin displays an excellent capillary absorption index and a capillary absorption capacity at a height of 40 cm, its particle surface is favorably crosslinked with a surface-crosslinking agent.
  • Examples of the surface-crosslinking agent usable for surface-crosslinking the water-absorbent resin include: polyhydric alcohol compounds, such as ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-l,3-pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-l,4-diol, 1,3 -butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymers, pentaerythritol,
  • polyisocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate
  • polyoxazoline compounds such as 1,2-ethylenebisoxazoline
  • alkylene carbonate compounds such as l,3-dioxolan-2-one, 4-methyl- 1, 3 -dioxolan-2-one, 4,5-dimethyl-l,3-dioxolan-2-one, 4,4-dimethyl- 1 ,3 -dioxolan-2-one, 4-ethyl- 1 ,3 -dioxolan-2-one, 4-hydroxymethyl-l,3-dioxolan-2-one, l,3-dioxan-2-one, 4-methyl- 1, 3 -dioxan-2-one, 4,6-dimethyl-l,3-dioxan-2-one, and l,3-dioxopan-2-one; haloe
  • the surface-crosslinking agent favorably includes a combination of surface-crosslinking agents of which the solubility parameters are different each other.
  • the surface-crosslinking agent favorably includes a combination of: a first surface-crosslinking agent having a solubility parameter of not less than 25.6 [(J/cm 3 ) 172 ] (12.5 [(cal/cm 3 ) 1/2 ]); and a second surface-crosslinking agent having a solubility parameter of less than 25.6 [(J/cm ) ] (12.5 [(cal/cm ) ]).
  • the solubility parameter of the surface-crosslinking agent is disclosed in such as USP 5,422,405.
  • the amount of the surface-crosslinking agent as used is favorably in the range of about 0.001 to about 5 parts by weight per 100 parts by weight of the water-absorbent resin. In the case where the amount is larger than 5 parts by weight or smaller than 0.001 part by weight, there is a case where it is difficult to obtain the surface-crosslinked layer in the range ofthe present invention.
  • Water may be used when the present invention surface-crosslinking agent is blended with the water-absorbent resin.
  • the amount of water as used is also generally in the range of 0.5 to 10 parts by weight (excluding 0.5 part by weight), favorably 1 to 5 parts by weight, per 100 parts by weight ofthe water-absorbent resin in terms of solid content.
  • hydrophilic organic solvents or a third substance may be used.
  • examples of the hydrophilic organic solvents include: lower alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol; ketones such as acetone; ethers, such as dioxane, tetrahydrofuran, methoxy(poly)ethylene glycol; amides, such as ⁇ -caprolactam, and N,N-dimethylformamide; sulfoxides such as dimethyl sulfoxide; and polyhydric alcohols, such as ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3 -propanediol, dipropylene glycol
  • the amount of the hydrophilic organic solvent as used is different according to factors such as the kind, particle diameter, or water content of the water-absorbent resin, but it is favorably smaller than 50 parts by weight, more favorably 0.1 to 10 parts by weight, per 100 pars by weight ofthe water-absorbent resin in terms of solid content.
  • inorganic acids, organic acids, and poly(amino acids) shown in EP 0668080 may be allowed to exist as the third substance.
  • blending methods which involve blending the water-absorbent resin and the surface-crosslinking agent, but examples thereof include: a method which involves immersing a water-absorbent resin in a hydrophilic organic solvent, and if necessary blending a surface-crosslinking agent as dissolved in water and/or the hydrophilic organic solvent; and a blending method which involves spraywise or dropwise adding a surface-crosslinking agent directly to a water-absorbent resin wherein the surface-crosslinking agent is dissolved in water and/or a hydrophilic organic solvent.
  • the blending temperature namely, both the temperature of the water-absorbent resin powder before blending and the temperature of the treating agent including the surface-crosslinking agent are controlled in a specific range, and thereby there is a case where the thickness or the weight ratio of the crosslinked layer is easily controlled in the range of the present invention.
  • water such as water-insoluble fine particulate powders and surfactants may be allowed to exist together.
  • the above heat-treating temperature depends also upon the surface-crosslinking agent as used, but the temperature of the water-absorbent resin powder is favorably adjusted to the range of 40 to 250 °C. In the case where the treating temperature is lower than 40 °C, there is a case where a water-absorbing agent having excellent absorption properties cannot be obtained. In the case where the treating temperature is higher than 250 °C, there is a case where the deterioration of the water-absorbent resin is caused, and the performance is lowered. Therefore, it is necessary to pay attention to this matter.
  • the heat-treating time is in the range of about a minute to about 2 hours, favorably about 5 minutes to about an hour.
  • preferred examples of methods to obtain the water-absorbent resin which is usable in the present invention and displays an excellent capillary absorption index B and capillary absorption capacity D at a height of 40 cm include: (1) a method which involve heat-treating a carboxyl-group-containing water-absorbent resin precursor having a weight-average particle diameter of not larger than 250 ⁇ m (favorably in the range of 40 to 200 ⁇ m, more favorably 70 to 150 ⁇ m), in the presence of a first surface-crosslinking agent having a solubility parameter of not less than 25.6 [(J/cm 3 ) 1 2 ] (12.5 [(cal/cm 3 ) 1/2 ]) and a second surface-crosslinking agent having a solubility parameter of less than 25.6 [(J/cm 3 ) 1 2 ]
  • a water-absorbent resin displaying a capillary absorption capacity D of such as not less than 15 (g/g) at a height of 40 cm, favorably not less than 20 (g/g), most favorably not less than 25 (g/g), and it can favorably be used for the present invention.
  • a water-absorbent resin displaying a capillary absorption index B of such as not less than 0.4 at a height of 40 cm, favorably not less than 0.5, more favorably not less than 0.6, and it can favorably be used for the present invention.
  • the water-absorbent resin of which the major proportion is comprised of a crosslinked poly(acrylic acid (salt)) polymer which is surface-crosslinking-treated by the above method (2) and has a weight-average particle diameter of not larger than 250 ⁇ m and is obtained by reversed-phase suspension polymerization.
  • a hitherto unknown excellent resin displaying a capillary absorption capacity D of such as not less than 25 (g/g) at a height of 40 cm can be obtained.
  • whether the surface-crosslinking treatment is carried out or not can be distinguished by such as a method that is disclosed in Japanese Patent Application No. 309105/1999.
  • water-absorbent resin by further adding additives (e.g. water-insoluble fine-particulate inorganic powders, such as silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, barium phosphate, silicic acid or its salts, clay, diatom earth, zeolite, bentonite, kaolin, hydrotalcite, and active white salts; and deodorants, perfumes, antimicrobial agents, cationic polymer compounds such as polyamines, adhesives, pressure sensitive adhesives, foaming agents, pigments, dyes, manure, oxidants, reductants, and water) to the water-swellable water-insoluble hydrogel-formable polymer, and thereby by including the additives in the above water-swellable water-insoluble hydrogel-formable polymer or attaching them thereto.
  • additives e.g. water-insoluble fine-particulate inorganic powders, such as silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide,
  • the amount of the above additive as used is favorably smaller than 30 weight %, more favorably smaller than 10 weight %, still more favorably smaller than 5 weight %, particularly favorably smaller than 1 weight %, relative to the total of the water-swellable water-insoluble hydrogel-formable polymer and the additive.
  • the present invention absorbent structure is obtained by combining a liquid-diffusing member and a water-absorbent resin in order to satisfy liquid-diffusion-and-storage coefficient 1 and/or liquid-diffusion-and-storage coefficient 2 in the present invention.
  • the present invention absorbent structure is also obtained by using: a liquid-diffusing member displaying a suction height of not lower than 30 cm; and a water-absorbent resin, as a liquid-storing member, displaying a capillary absorption capacity D of not less than 15 (g/g) at a height of 40 cm.
  • the present invention absorbent structure is also obtained by using: a liquid-diffusing member displaying a suction height of not lower than 30 cm; and a water-absorbent resin as a liquid-storing member wherein the water-absorbent resin is surface-crosslinking-treated and has a weight-average particle diameter of not larger than 250 ⁇ m.
  • the present invention absorbent structure may comprise other materials in addition to the liquid-diffusing member and the water-absorbent resin, as long as the liquid-diffusion-and-storage system as aimed in the present invention is not hindered.
  • other materials include hydrophilic fibers, nonwoven fabrics, papers, and tissue papers.
  • hydrophilic fibers include: cellulose fibers as obtained from wood, such as mechamical pulps, chemical pulps, semi-chemical pulps, and dissolved pulps; and fibers, such as rayon and acetate.
  • the cellulose fibers are favorable.
  • the hydrophilic fibers may include synthetic fibers, such as polyamide, polyesters, and polyolefin.
  • the hydrophilic fibers are not limited to the above-exemplified fibers.
  • the nonwoven fabrics include nonwoven fabrics of such as polyesters, polyethylene, polypropylene, nylon, and rayon, having a spun bond, chemical bond, or spunlace system.
  • the weight ratio of the water-absorbent resin and the liquid-diffusing member in the absorbent structure can be selected in an arbitrarily range, but the weight ratio of the water-absorbent resin is favorably in the range of 5 to 99 weight %, more favorably 20 to 90 weight %, still more favorably 30 to 80 weight %, relative to the total weight of the water-absorbent resin and the liquid-diffusing member.
  • the weight ratio ofthe water-absorbent resin is in the range of 75 to 90 weight % relative to the total weight of the water-absorbent resin and the liquid-diffusing member, there are advantages in that: the amount of the liquid-diffusing member as used can be lowered relatively, and therefore a lighter and thinner absorbent structure can be produced in view of shape.
  • a water-absorbent resin displaying a capillary absorption capacity D of not less than 15 (g/g) at a height of 40 cm is more favorably used as the water-absorbent resin.
  • the transfer and diffusion of the liquid from the liquid-diffusing member to the water-absorbent resin is favorably carried out.
  • a porous polymer which is obtained by a process including the step of polymerizing a high-internal-phase emulsion and of which the suction height is not lower than 30 cm, is favorably used as the liquid-diffusing member.
  • Examples of the arranging position of the water-absorbent resin include: a back face ofthe liquid-diffusing member, a front face ofthe liquid-diffusing member, a portion of a back face side ofthe liquid-diffusing member, a portion of a front face side ofthe liquid-diffusing member, a portion between the liquid-diffusing members, and an inner portion of the liquid-diffusing member, and these arranging methods may be combined.
  • the water-absorbent resin is favorably arranged at a back face side of the liquid-diffusing member, the water-absorbent resin more favorably exists in a layer form.
  • the weight of the water-absorbent resin per its unit area is in the range of about 50 to about 500 g /m 2 .
  • the arranging state of the water-absorbent resin include: a state in which the water-absorbent resin uniformly exists over the entire surface of the liquid-diffusing member; a state in which the water-absorbent resin exists in a specific pattern; a state in which the water-absorbent resin exists with a slope of density; a state in which the water-absorbent resin exists only in the center of the liquid-diffusing member; and a state in which the water-absorbent resin exists only front and back the liquid-diffusing member.
  • the water-absorbent resin itself is converted to a sheet by the hitherto publicly known method, or scattered on a base material for fixing, or packed in a bag, or given adhesion. Thereafter, it may be combined with the liquid-diffusing member. Furthermore, the water-absorbent resin may adhere to the liquid-diffusing member by using an adhesive binder.
  • hot-melt adhesive fibers such as polyolefm fibers (e.g. polyethylene, polypropylene, ethylene-propylene copolymers, and 1-butene-ethylene copolymers), and adhesive emulsions, and hot-melt adhesives.
  • polyolefm fibers e.g. polyethylene, polypropylene, ethylene-propylene copolymers, and 1-butene-ethylene copolymers
  • adhesive binders may be used either alone respectively or in combinations with each other.
  • water-insoluble fme-particulate inorganic powders such as silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, barium phosphate, silicic acid or its salts, clay, diatom earth, zeolite, bentonite, kaolin, hydrotalcite, and active white salts; deodorants; perfumes; antimicrobial agents; cationic polymer compounds such as polyamines; foaming agents; pigments; dyes; hydrophilic short fibers; manure; oxidants; reductants; and water) are further added thereto, and further functions can also be given to the absorbent structure.
  • the water-absorbent resin layer as combined with the liquid-acquiring member favorably includes a water-absorbent resin in a scattering amount of not smaller than 250 g/m 2 , and it is composed so that the water-absorbent resin will form a substantially continuous layer when being swollen.
  • the scattering amount is smaller than 250 g/m 2 , there is a tendency such that: the saturated absorption quantity of the absorbent structure is decreased; the liquid-acquiring layer cannot be dried sufficiently; the dry feeling is deteriorated; and the amount of wet back ofthe aqueous liquid is increased.
  • the scattering amount in the water-absorbent resin layer is more favorably not smaller than 300 g m 2 , still more favorably not smaller than 350 g/m 2 , particularly favorably not smaller than 400 g/m 2 .
  • the water-absorbent resin layer comprises only the water-absorbent resin or a mixture of the water-absorbent resin and other water-absorbent or hydrophilic materials.
  • other water-absorbent or hydrophilic materials include: fibers, such as natural fibers, regenerated fibers, and synthetic fibers (e.g. pulps, rayon, polyesters, and nylon); and these hydrophilyzing-treated materials.
  • the ratio of the water-absorbent resin in the water-absorbent resin layer is favorably not less than 70 weight % in view of thinning the absorbent structure and enabling the absorption amount to increase, more favorably not less than 80 weight %, still more favorably not less than 90 weight %.
  • the water-absorbent resin layer particularly favorably comprises only the water-absorbent resin (namely, 100 weight %).
  • the water-absorbent resin usable in the present invention is a water-absorbent resin wherein when the capillary absorption index of the liquid- acquiring member at a height of 40 cm is referred to as E (E ⁇ 0.1), the capillary absorption index B of the water-absorbent resin at a height of 40 cm satisfies the following equation:
  • the water-absorbent resin layer usable in the present invention is a water-absorbent resin wherein when the capillary absorption index ofthe liquid- acquiring member at a height of 40 cm is referred to as E (E ⁇ 0.1), the capillary absorption index F of the water-absorbent resin layer at a height of 40 cm satisfies the following equation:
  • the value of the capillary absorption index B or F of the water-absorbent resin or water-absorbent resin layer necessary in the present invention at a height of 40 cm is different depending upon the property of the liquid-acquiring member as used, namely, the capillary absorption index E of the liquid-acquiring member as used at a height of 40 cm. If the above relationship B/E ⁇ 10 or F/E ⁇ 10 is satisfied, a liquid from the liquid-acquiring member to the water-absorbent resin is favorably absorbed, and the water-absorbent resin can dry the liquid-acquiring member sufficiently.
  • the water-absorbent resin favorably satisfies B/E ⁇ 20 or F/E ⁇ 20, more favorably B/E ⁇ 30 or F/E ⁇ 30.
  • the value of the B/E or F/E may be referred to as a liquid-acquirement-and-storage coefficient 1.
  • the B means a capillary absorption index as determined by using a single water-absorbent resin
  • the F means a capillary absorption index as determined by using a water-absorbent resin layer itself, when it is, for example, difficult to isolate the water-absorbent resin from the water-absorbent resin layer.
  • the liquid-acquiring member displays a capillary absorption capacity G of not more than
  • the liquid-acquiring member displays a capillary absorption capacity G of not more than 1.0 (g/g) at a height of 40 cm
  • the aforementioned water-absorbent resin layer displays a capillary absorption capacity H of not less than 5 (g/g) at a height of 40 cm.
  • liquid-acquiring member and the water-absorbent resin or water-absorbent resin layer satisfy these relationships, a liquid from the liquid-acquiring member to the water-absorbent resin is favorably distributed, and the water-absorbent resin can dry the liquid-acquiring member sufficiently, and the liquid can be absorbed and stored therein.
  • the water-absorbent resin difficultly absorbs the liquid from the liquid-acquiring member sufficiently, and the liquid-acquiring member is not dried, and the amount of wet back of the aqueous liquid is greatly increased.
  • the value ofthe capillary absorption capacity D or H of the water-absorbent resin or water-absorbent resin layer necessary in the present invention at a height of 40 cm is favorably not less than 10 (g/g), more favorably not less than 15 (g/g), most favorably not less than 20 (g/g).
  • liquid-acquirement-and-storage coefficient 2 when the value of the D/F or H/F may be referred to as a liquid-acquirement-and-storage coefficient 2, this value is favorably not less than 30, more favorably not less than 50. In the present invention, it is more favorable that both the values of the liquid-acquirement-and-storage coefficient 1, D and H as mentioned above satisfy the present invention range. When only the one value satisfies the range, the liquid absorption ability of the water-absorbent resin from the liquid-acquiring member may not be displayed favorably, and therefore it is necessary to pay attention to this matter.
  • the D means a capillary absorption capacity as determined by using a single water-absorbent resin
  • the H means a capillary absorption capacity as determined by using a water-absorbent resin layer itself, when it is, for example, difficult to isolate the water-absorbent resin from the water-absorbent resin layer.
  • the liquid-acquiring member usable in the present invention is a member that acts the part of: capturing a liquid as added to an absorbent structure or an absorbent article including the absorbent structure in a moment; and not leaking the liquid o ⁇ t of the absorbent structure.
  • the liquid-acquiring member is defined as a material displaying a capillary absorption index E of less than 0.10 at a height of 40 cm and a capillary absorption capacity G of not more than 1.0 (g/g) at a height of 40 cm. Generally, even after the liquid-acquiring member is loaded or absorbed, it has such a structure as can maintain a space for capturing the liquid.
  • the liquid-acquiring member usable in the present invention is a member having excellent liquid-acquiring and liquid-releasing ability, and it is necessary that the capillary absorption index E is less than 0.1 at a height of 40 cm.
  • the capillary absorption index E of such as flap pulp as used for disposable diapers hitherto is 0.04 at a height of 40 cm according to the measurement method in the present invention.
  • Such a material can also be used as the liquid-acquiring member of the present invention. If this value is smaller, it favorably has excellent liquid-acquiring and liquid-releasing ability.
  • a material displaying a capillary absorption index E of not less than 0.10 retains a liquid in the material comparatively strongly. When the material repeatedly absorbs the liquid, the liquid-acquiring performance is rapidly deteriorated.
  • the liquid-acquiring member favorably has a capillary absorption index E of not more than 0.03 at a height of 40 cm.
  • the liquid-acquiring member usable in the present invention favorably displays a capillary absorption capacity of not less than 5 (g/g) at a height of 0 cm.
  • the capillary abso ⁇ tion capacity is more favorably not less than 10 (g/g) at a height of 0 cm, still more favorably not less than
  • liquid-acquiring member usable in the present invention displays a capillary absorption capacity G of not more than 1.0 (g/g) at a height of 40 cm.
  • the capillary abso ⁇ tion capacity G of such as flap pulp as used for disposable diapers hitherto is about 0.5 (g/g) at a height of 40 cm.
  • Such a material can also be used as the liquid-acquiring member of the present invention. If this value is smaller, it favorably has excellent liquid-acquiring and liquid-releasing ability.
  • a material displaying a capillary abso ⁇ tion capacity G of more than 1.0 (g/g) at a height of 40 cm retains a liquid in the material comparatively strongly.
  • the liquid-acquiring member favorably has a capillary absorption capacity G of not more than 0.4 (g/g) at a height of 40 cm, more favorably not more than 0.2 (g/g).
  • another liquid-acquiring member usable in the present invention favorably displays a capillary absorption capacity of not less than 5 (g/g) at a height of 0 cm, but the above limitation is not applied if the retention ofthe liquid is not an important object.
  • the capillary absorption capacity is more favorably not less than 10 (g/g) at a height of 0 cm, still more favorably not less than 15 (g/g).
  • the liquid-acquiring member usable in the present invention satisfies the above conditions, and is used together with a water-absorbent resin (layer), and thereby they are used as an absorbent structure.
  • the capillary absorption index ofthe liquid-acquiring member at a height of 40 cm is referred to as E (E ⁇ 0.1)
  • the capillary absorption index B ofthe above water-absorbent resin at a height of 40 cm satisfies B/E ⁇ 10
  • the capillary absorption index F of the above water-absorbent resin layer at a height of 40 cm satisfies F/E ⁇ 10.
  • the shape of the liquid-acquiring member can be such as a sheet shape, a fibrous shape, a fibrous aggregate, a particulate shape, or a strip shape, but it is favorably a sheet shape in general.
  • the weight of the liquid-acquiring member per its unit area is favorably in the range of about 50 to about 500 g ⁇ n 2 , more favorably about 100 to about 200 g /m 2 .
  • liquid-acquiring member has a difference of density, a slope of density, a difference of acquisition ability, and a slope of acquisition ability in the member, or when a second liquid-acquiring member or liquid-diffusing member not satisfying the present invention relationship is further used, it is favorable to make the capillary absorption ability of a portion ofthe liquid-acquiring member much closer to the water-absorbent resin satisfy the above relationship.
  • liquid-acquiring member usable in the present invention examples include: flap pulps, crosslinking-treated cellulose fibers, synthetic fibers (e.g. nonwoven fabrics having a bulky structure), porous polymers obtained by a process including the step of polymerizing a high-internal-phase emulsion (HIPE), and foaming structures including synthetic polymers (e.g.
  • polyurethanes polystyrene, polyethylene, polypropylene, polyesters, poly(vinyl alcohol), butadiene-styrene rubbers (SB R), and nitrile-butadiene rubbers); fibrous aggregates as obtained by adhering to or combining with synthetic fibers, such as polyethylene, polypropylene, polyethylene terephthalate, and nylon; rayon fibers; and fibrous aggregates as obtained by adhering to under a pressure, adhering to, or combining with hydrophilic fibers, such as cellulose fibers (e.g. celluloses, cellulose acetate, and nitrocellulose) and polyamide fibers.
  • crosslinking-treated cellulose fibers, the synthetic fibers such as the nonwoven fabrics having a bulky structure, and the porous polymers obtained by a process including the step of polymerizing a high-internal-phase emulsion (HIPE) are favorable.
  • HIPE high-internal-phase emulsion
  • Water-absorbent resins have hitherto been used as materials absorbing liquids due to the osmotic pressure difference between the inside and the outside of the resins, and as liquid-storing members such as disposable diapers.
  • the present inventors took note of that: even if the properties of the water-absorbent resins as known hitherto (e.g. absorption capacity of water-absorbent resin, absorption capacity of water-absorbent resin under a load) are identical, the absorbing behaviors are greatly different due to the kinds of resins when liquids are absorbed from such as the liquid-acquiring member.
  • the capillary absorption ability is greatly different even in a water-absorbent resin itself; and the water-absorbent resin can receive and store a liquid from the liquid-acquiring member more favorably when the relationship between the capillary absorption ability of the liquid-acquiring member and the capillary absorption ability of the water-absorbent resin satisfies a specific condition.
  • the water-absorbent resin usable in the present invention is a water-absorbent resin, in which, as is mentioned above, when the capillary absorption index of the above liquid-acquiring member at a height of 40 cm is referred to as E (E ⁇ 0.10), the capillary absorption index B of the water-absorbent resin at a height of 40 cm satisfies B/E ⁇ 10, favorably B/E ⁇ 20, more favorably B/E ⁇ 30.
  • the water-absorbent resin may be measured in a state of a water-absorbent resin layer as taken out from the absorbent structure, and then the capillary abso ⁇ tion index F of the above water-absorbent resin layer at a height of 40 cm satisfies F/E ⁇ 10, favorably F/E ⁇ 20, more favorably F/E ⁇ 30.
  • the value of the capillary absorption index B of the water-absorbent resin necessary in the present invention or the capillary absorption index F of the water-absorbent resin layer at a height of 40 cm is different depending upon the property of the liquid-acquiring member as used, namely, the capillary absorption index E of the liquid-acquiring member as used at a height of 40 cm. If the above relationship B/E ⁇ 10 or F/E ⁇ 10 is satisfied, a liquid from the liquid-acquiring member to the water-absorbent resin or water-absorbent resin layer is favorably transferred. Then, the water-absorbent resin can favorably absorb and store the liquid, and the liquid-acquiring member can be dried.
  • the capillary absorption index B of the water-absorbent resin or the capillary absorption index F of the water-absorbent resin layer is favorably not less than 0.2 at a height of 40 cm, more favorably not less than 0.4, still more favorably not less than 0.6.
  • the water-absorbent resin as used in the present invention favorably displays a capillary absorption capacity of not less than 20 (g/g) at a height of 0 cm. If the capillary absorption capacity at a height of 0 cm is higher, the water-absorbent resin can retain a large amount of liquid as sucked up from the liquid-acquiring member. Therefore, an excellent absorbent structure is obtained from the viewpoint of the liquid absorption ability.
  • the water-absorbent resin favorably displays a capillary absorption capacity of not less than 30 (g/g) at a height of 0 cm, more favorably not less than 40 (g/g), still more favorably not less than 50 (g/g).
  • another water-absorbent resin usable in the present invention is a water-absorbent resin that favorably satisfies a capillary absorption capacity D of not less than 5 (g/g) at a height of 40 cm, more favorably not less than 10 (g/g), still more favorably not less than 15 (g/g), most favorably not less than 20 (g/g).
  • the water-absorbent resin may be measured in a state of a water-absorbent resin layer as talcen out from the absorbent structure, and then the capillary absorption capacity H of the above water-absorbent resin layer favorably satisfies not less than 5 (g/g) at a height of 40 cm, more favorably not less than 10 (g/g), still more favorably not less than 15 (g/g), most favorably not less than 20 (g/g).
  • the water-absorbent resin usable in the present invention satisfies the above conditions. It is used together with a liquid-acquiring member that satisfies the requisite in the present invention, and thereby they are used as an absorbent structure.
  • the shape ofthe water-absorbent resin can be such as a particulate, fibrous, sheet, or strip shape, but it is favorably a particulate shape in general.
  • aqueous solution polymerization or reversed-phase suspension polymerization can be carried out.
  • a water-absorbent resin satisfying the above relationship and a water-absorbent resin not satisfying the above relationship may be used together as the water-absorbent resin, but only the water-absorbent resin satisfying the above relationship is favorably used in order to display the present invention effect to the maximum.
  • the resin is favorably arranged so that the capillary absorption ability of a portion of the water-absorbent resin will satisfy the above relationship, wherein the portion is much closer to the liquid- acquiring member.
  • Examples of the water-absorbent resin usable in the present invention examples of monomers used as raw materials ofthe above water-absorbent resin and their amounts as used, methods for introducing a crosslinked structure, explanations as to internal crosslinking, examples of additives and their amounts as used when the polymerization is carried out, polymerization methods, the shape of the water-absorbent resin as obtained, explanations as to surface crosslinking, and explanations as to additives to give further functions to the water-absorbent resin are the same as mentioned in the previous (2-3) item.
  • Examples of preferred methods to obtain the water-absorbent resin usable in the present invention, which displays an excellent capillary absorption index B and capillary absorption capacity D at a height of 40 cm include:
  • (3) a method which involve: treating a carboxyl-group-containing water-absorbent resin precursor having a weight-average particle diameter of 100 to 600 ⁇ m in the presence of a polyhydric alcohol or an alkylene carbonate in order to have a specific surface-crosslinked layer; and thereafter classifying the resultant water-absorbent resin with a sieve having specific particle diameter distribution in order to obtain particles having a weight-average particle diameter of not larger than 400 ⁇ m (favorably in the range of 100 to 400 ⁇ m).
  • a water-absorbent resin displaying a capillary absorption capacity D of such as not less than 10 (g/g) at a height of 40 cm, favorably not less than 15 (g/g), most favorably not less than 25 (g/g), and it can favorably be used for the present invention.
  • a water-absorbent resin displaying a capillary absorption index B of such as not less than 0.2 at a height of 40 cm, favorably not less than 0.4, more favorably not less than 0.6, and it can favorably be used for the present invention.
  • the present invention absorbent structure is obtained by combining the liquid-acquiring member and the water-absorbent resin layer that satisfy the above properties.
  • the water-absorbent resin layer has the above-mentioned water-absorbent resin amount and structure.
  • the water-absorbent resin layer favorably has a scattering amount of not smaller than 250 g/m 2 , and the water-absorbent resin layer is composed so that the water-absorbent resin will be a substantially continuous layer when being swollen.
  • the scattering amount in the water-absorbent resin layer is favorably not smaller than 300 g/m 2 , more favorably not smaller than 350 g/m 2 , still more favorably not smaller than 400 g/m 2 .
  • the water-absorbent resin usable in the present invention may comprise other base material (e.g.
  • the present invention absorbent structure may comprise other materials in addition to the liquid-acquiring member and the water-absorbent resin as long as the objective liquid-acquisition-and-storage system in the present invention is not hindered. Examples of other materials include hydrophilic fibers, nonwoven fabrics, papers, and tissue papers.
  • hydrophilic fibers examples include: cellulose fibers as obtained from wood, such as mechamical pulps, chemical pulps, semi-chemical pulps, and dissolved pulps; and fibers, such as rayon and acetate.
  • the cellulose fibers are favorable.
  • the hydrophilic fibers may include synthetic fibers, such as polyamide, polyesters, and polyolefm.
  • the hydrophilic fibers are not limited to the above-exemplified fibers.
  • nonwoven fabrics include nonwoven fabrics of such as polyesters, polyethylene, polypropylene, nylon, and rayon, having a spun bond, chemical bond, or spunlace system.
  • absorbent structure the liquid-acquiring member and the water-absorbent resin layer are favorably comprised of one layer each.
  • the liquid-acquiring member is comprised of at least two layers, there is a case where: a liquid is not favorably absorbed from the entire liquid-acquiring member to the water-absorbent resin layer in the absorbent structure; and the dry feeling and the amount of wet back ofthe aqueous liquid are deteriorated.
  • the ratio of the water-absorbent resin layer and the liquid-acquiring member in the absorbent structure can be selected in an arbitrarily range, but the weight ratio of the water-absorbent resin layer is favorably not smaller than 70 weight %, more favorably in the range of 80 to 95 weight %, relative to the total weight ofthe liquid-acquiring member and the water-absorbent resin layer.
  • the weight ratio of the liquid absorption quantity of the water-absorbent resin layer is favorably not less than 80 weight %, more favorably in the range of 80 to 95 weight %, still more favorably in the range of 90 to 95 weight %, relative to the saturated liquid absorption quantity of the absorbent structure.
  • the amount of the liquid-acquiring member or the water-absorbent resin layer as used depends upon the size of an objective absorbent article.
  • the amount ofthe liquid-acquiring member is favorably 0.5 to 4 g, more favorably about 1 to about 2 g, and the amount of the water-absorbent resin layer is favorably 10 to 30 g, more favorably about 15 to about 20 g.
  • Examples of the arranging position of the water-absorbent resin layer include: a back face of the liquid-acquiring member (a liquid-impermeable back sheet side of an absorbent article), a front face of the liquid-acquiring member, a portion of a back face side of the liquid-acquiring member, a portion of a front face side ofthe liquid-acquiring member, a portion between the liquid-acquiring members, and an inner portion of the liquid-acquiring member, and these arranging methods may be combined.
  • the water-absorbent resin layer is favorably arranged at a back face side of the liquid-acquiring member.
  • Examples of the arranging state of the water-absorbent resin layer include: a state in which the water-absorbent resin uniformly exists over the whole surface of liquid-acquiring member; a state in which the water-absorbent resin exists in a specific pattern; a state in which the water-absorbent resin exists with stripes; a state in which the water-absorbent resin exists with a slope of density; a state in which the water-absorbent resin exists only in the center of the liquid-acquiring member; and a state in which the water-absorbent resin exists only front and back the liquid-acquiring member. It is favorable that the area where the water-absorbent resin layer exists is larger than that where the liquid-acquiring member exists.
  • the area ratio of the water-absorbent resin layer is favorably not less than 1.2, more favorably not less than 2, relative to the area 1 ofthe liquid-acquiring member.
  • the water-absorbent resin or water-absorbent resin layer itself is converted to a sheet by the hitherto publicly known method, or scattered on a base material for fixing, or packed in a bag, or given adhesion. Thereafter, it may be combined with the liquid-acquiring member.
  • the water-absorbent resin layer may adhere to the liquid-acquiring member by using an adhesive binder.
  • the above adhesive binder include: hot-melt adhesive fibers, such as polyolefm fibers (e.g.
  • adhesive binders may be used either alone respectively or in combinations with each other. In this case, it is more favorably that the capillary absorption ability of not only the water-absorbent resin itself but also the water-absorbent resin layer in a fixed state satisfies the present invention range.
  • materials e.g. water-insoluble fine-particulate inorganic powders, such as silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, barium phosphate, silicic acid or its salts, clay, diatom earth, zeolite, bentonite, kaolin, hydrotalcite, and active white salts; deodorants; perfumes; antimicrobial agents; cationic polymer compounds such as polyamines; foaming agents; pigments; dyes; hydrophilic short fibers; manure; oxidants; reductants; and water) are further added thereto, and further functions can also be given, to the absorbent structure.
  • materials e.g. water-insoluble fine-particulate inorganic powders, such as silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, barium phosphate, silicic acid or its salts, clay, diatom earth, zeolite, bentonite, kaolin, hydrotalcite
  • the aforementioned absorbent structure according to the present invention namely, the absorbent structure comprising the liquid-acquiring member and the water-absorbent resin layer may further comprise the aforementioned liquid-diffusing member.
  • an absorbent structure having both the above-mentioned characteristic (which the present invention absorbent structure comprising the liquid-diffusing member and the water-absorbent resin has) and the characteristic (which the present invention absorbent structure comprising the liquid-acquiring member and the water-absorbent resin layer has) together is favorable because the present invention effect can be displayed further more.
  • the present invention absorbent article generally comprises: the present invention absorbent structure having the above constitution, namely, the absorbent structure including the liquid-diffusing member and the water-absorbent resin, or the absorbent structure including the liquid-acquiring member and the water-absorbent resin layer; a liquid-permeable sheet; and a liquid-impermeable sheet, wherein the absorbent structure is sandwiched between the liquid-permeable sheet and the liquid-impermeable sheet.
  • the above absorbent article has excellent water absorption properties as mentioned above because it comprises the absorbent structure having the above constitution.
  • the above absorbent article include: sanitary materials such as disposable diapers, sanitary napkins, and so-called incontinent pads; medical sheets; and dew-absorbent sheets, but there is no especial limitation thereto.
  • the present invention absorbent article has excellent absorption properties. Therefore, when the above absorbent article is, for example, a disposable diaper, the liquid absorption efficiency is increased very much, and the leakage of urine can be inhibited, and besides, the so-called dry feeling can be given, and the thinning and lightening can be realized.
  • the material referred to as the above liquid-permeable sheet is a material having a property of permeating an aqueous liquid, and examples thereof include: nonwoven fabrics; woven fabrics; and porous synthetic resin films comprised of polyethylene, polypropylene, polyesters, or polyamides.
  • the above liquid-impermeable sheet is a material having a property of not permeating an aqueous liquid, and examples thereof include: synthetic resin films of polyethylene, polypropylene, ethylene vinyl acetate, and polyvinyl chloride; films of combined materials of these synthetic resins with nonwoven fabrics; and films of combined materials of the above synthetic resins with woven fabrics.
  • the liquid-impermeable sheet may have a property of making vapor permeate.
  • the water-absorbent resin which displays a capillary absorption ability having a specific relationship with that of the liquid-diffusing member or liquid-acquiring member, is combined and used with the above liquid-diffusing member or liquid-acquiring member. Therefore, the water-absorbent resin can favorably absorb or store a liquid from the liquid-diffusing member or liquid-acquiring member, and it displays very excellent liquid abso ⁇ tion efficiency.
  • the present invention makes the system as called the diffusion to the storage of the liquid favorably work, and can provide the absorbent structure and the absorbent article displaying very excellent liquid diffusion and storage ability by a very simple production process. In the absorbent article as produced by using such an absorbent structure
  • the water-absorbent resin usable for the present invention absorbent structure and absorbent article is mentioned above.
  • the present invention also provides: water-absorbent resin particles as a particularly favorable water-absorbent resin; and a production process therefore, as explained below.
  • the production process for water-absorbent resin particles is characterized by comprising the step of adding a dispersion of water-dispersible fine particles to a water-absorbent resin, thereby increasing the weight-average particle diameter of the water-absorbent resin by not less than 50 %, wherein the water-absorbent resin has a weight-average particle diameter of 50 to 300 ⁇ m and displays a space ratio of 30 to 50 % and an average space radius of 80 to 150 ⁇ m as to spaces between particles when saturation-swollen with a physiological saline (a 0.9 weight % aqueous NaCl solution) without load.
  • the water-absorbent resin usable in the present invention production process for water-absorbent resin particles has a weight-average particle diameter of 50 to 300 ⁇ m, and displays a space ratio of 30 to 50 % and average space radius of 80 to 150 ⁇ m as to spaces between particles when saturation-swollen with a physiological saline (a 0.9 weight % aqueous NaCl solution) without load.
  • the method of measuring the thickness of the surface-crosslinked layer is disclosed in such as Japanese Patent Application No. 329501/2000.
  • the cationic polymer is exemplified in such as JP-A-031360/1993 and JP-A-000370/1994.
  • the water-absorbent resin as obtained in this method which displays a space ratio of 30 to 50 % and an average space radius of 80 to 150 ⁇ m as to spaces between particles when saturation-swollen without load, is used as a raw material powder.
  • the present invention water-absorbent resin particles have firm granulation ability when they are dry. However, when they contact a large quantity of liquid, the bond is broken and therefore they have re-dispersibility.
  • granule particles are, for example, saturation-swollen with a physiological saline (a 0.9 weight % aqueous NaCl solution), it results in a state where the particles are dispersed again, and freely absorb a liquid and are swollen, and then the particles display a space ratio of 30 to 50 % and an average space radius of 80 to 150 ⁇ m as to spaces between particles when saturation-swollen without load.
  • the water-absorbent resin usable in the present invention production process for water-absorbent resin particles has a weight-average particle diameter of 50 to 300 ⁇ m, but it favorably has a weight-average particle diameter of 100 to 300 ⁇ m, more favorably 150 to 250 ⁇ m in order to more effectively obtain the water-absorbent resin particles according to the present invention.
  • the water-absorbent resin usable in the present invention production process for water-absorbent resin particles displays a space ratio of 30 to 50 % as to spaces between particles when saturation-swollen with a physiological saline (a 0.9 weight % aqueous NaCl solution) without load, but it favorably displays a space ratio of 35 to 45 % in order to more effectively obtain the water-absorbent resin particles according to the present invention.
  • the water-absorbent resin usable in the present invention production process for water-absorbent resin particles displays an average space radius of 80 to 150 ⁇ m as to spaces between particles when saturation-swollen without load.
  • the present invention production process for water-absorbent resin particles is characterized by comprising the step of adding a dispersion of water-dispersible fine particles to the water-absorbent resin having the above-mentioned characteristics, thereby increasing the weight-average particle diameter ofthe water-absorbent resin by not less than 50 %.
  • examples of powdery inorganic substances include: water-insoluble fine-particulate inorganic powders (e.g. silicon dioxide, aluminum oxide, zinc oxide, magnesium oxide, titanium dioxide, calcium phosphate, barium phosphate, calcium carbonate, talc, magnesium phosphate, calcium sulfate, silicic acid or its salts, clay, diatom earth, bentonite, zeolite, kaolin, hydrotalcite, and active white salts), and other metal oxides.
  • water-insoluble fine-particulate inorganic powders e.g. silicon dioxide, aluminum oxide, zinc oxide, magnesium oxide, titanium dioxide, calcium phosphate, barium phosphate, calcium carbonate, talc, magnesium phosphate, calcium sulfate, silicic acid or its salts, clay, diatom earth, bentonite, zeolite, kaolin, hydrotalcite, and active white salts
  • the silicon dioxide, aluminum oxide, and titanium dioxide are favorable.
  • These water-dispersible fine particles favorably have a weight-average primary particle diameter (a weight-average particle diameter of individual particles, a weight-average particle diameter of individual particles before aggregation or granulation when the at least two particles are aggregated or granulated) of not larger than 3.0 ⁇ m in general, more favorably in the range of 3.0 to 0.005 ⁇ m, and they are favorably extremely fine particles having particle diameters of not larger than 0.1 ⁇ m on average.
  • the amount of the above water-dispersible fine particles as contained and used is generally in the range of favorably 0.1 to 5 parts by weight, more favorably 0.3 to 2.0 parts by weight, per 100 parts by weight of the water-absorbent resin.
  • the amount of the powdery inorganic substance as added is generally smaller than 0.1 part by weight, granules cannot be obtained, or the effect is poor even if granules can be obtained.
  • the amount of the water-dispersible fine particles is larger than 5 parts by weight, lumps are obtained as the granules, or, even if granules are obtained, they are coarse particles and have a bad influence upon absorption performance.
  • the further effect for the addition cannot be expected, and therefore it is not economical.
  • Particles having arbitrary particle diameters in a narrow range of particle diameter distribution are obtained by changing the amount as added in these ranges.
  • the water-dispersible fine particles as used in the present invention have such a property of not inhibiting permeability of water and swellability of water-absorbent resins, and do not prevent the component as combined from permeating and absorbing ofthe liquid. In addition, they do not cause the blocking when being swollen, and display the absorption ability of the water-absorbent resin sufficiently.
  • the granulated water-absorbent resin particles have firm granulation ability and no powdery dust when they are dry; when they absorb a liquid, the water-dispersible fine particles introduce and distribute water, and besides, the bond is broken; and the water-absorbent resin has a property of freely absorbing a liquid and swelling.
  • the aforementioned water-dispersible fine particles are used as a dispersion obtained by dispersing them in water or an aqueous medium.
  • the amount of the dispersion as used is favorably in the range of 3 to 100 parts by weight per 100 parts by weight of the water-absorbent resin.
  • the amount ofthe dispersion is smaller than 3 parts by weight, granules cannot be obtained, or the effect is poor even if granules can be obtained.
  • the amount of the dispersion is larger than 100 parts by weight, there are disadvantages in that lumps are obtained as the granules, or, even if granules are obtained, they are coarse particles.
  • the water-dispersible fine particles when they are dispersed in an aqueous medium, they display a so-called structural viscosity and the viscosity of the dispersion having a concentration of 6.7 weight % is not less than 0.5 Pa s (Brookfield rotary viscometer, 6 rpm, and 25 °C).
  • the amount of the water-dispersible fine particles and the amount of water in the dispersion it is necessary that the amount as added is each determined and selected, in order to obtain the optimum granulation state, depending upon the particle surface area or surface state ofthe water-absorbent resin.
  • the present invention water-absorbent resin particles are obtained by a process including the steps of: blending a water-absorbent resin and a dispersion of water-dispersible fine particles; and then heat-drying the resultant mixture.
  • the method for blending the water-absorbent resin and the dispersion of the water-dispersible fine particles general is a method of spraywise or dropwise adding the above treating solution to the water-absorbent resin powder, and then blending them.
  • the blender as used for blending is favorably a blender having large blendability to carry out blending uniformly, but conventional blenders or kneaders can be used.
  • Examples thereof include cylinder type blenders, double ⁇ -wall cone type blenders, V-character-shaped blenders, ribbon type blenders, screw type blenders, fluidizing type blenders, rotary disk type blenders, air blow type blenders, twin-arm type kneaders, internal mixers, roll mixers, and screw type extruders.
  • Conventional dryers or heating furnaces can be used in order to heat a mixture as obtained by blending the water-absorbent resin powder with these treating solution.
  • Examples thereof include channel type blending dryers, rotary dryers, disk dryers, kneading dryers, fluidized-bed dryers, air blow type dryers, infrared dryers, and dielectric-heating dryer.
  • the heat-treating temperature is favorably in the range of 40 to 250 °C, more favorably 80 to 200 °C.
  • the weight-average particle diameter of the water-absorbent resin particles as obtained increases by not less than 50 % by adding the above dispersion of the water-dispersible fine particles.
  • the present invention water-absorbent resin particles as obtained by the above production process have an absorption property (e.g. high capillary aspiration ability) that water-absorbent resin particles as obtained by conventional methods could not obtain. Furthermore, the dispersion ofthe water-dispersible fine particles works as an excellent binder. Therefore, the mechanical strength ofthe particles as obtained is remarkably improved and the scatter of the water-absorbent resin particles can be remarkably suppressed when they are practically used.
  • absorption property e.g. high capillary aspiration ability
  • the present invention water-absorbent resin particles are water-absorbent resin particles as obtained by a process including the step of granulating a water-absorbent resin having a weight-average particle diameter of 50 to 300 ⁇ m and displaying a space ratio of 30 to 50 % and an average space radius of 80 to 150 ⁇ m as to spaces between particles when saturation-swollen with a physiological saline (a 0.9 weight % aqueous NaCl solution) without load, wherein the water-absorbent resin particles have a weight-average particle diameter as increased by not less than 50 % of that before the granulating step.
  • the weight-average particle diameter of the present invention water-absorbent resin particles is favorably 150 to 600 ⁇ m, more favorably 200 to 500 ⁇ m, still more favorably 200 to 400 ⁇ m.
  • the present invention water-absorbent resin particles favorably display a capillary abso ⁇ tion capacity of not less than 7 g/g at a height of 40 cm, more favorably not less than 15 g/g, still more favorably not less than 25 g/g.
  • the present invention water-absorbent resin particles are blended and used with such as a pulverized pulp because of their improved absorption properties. Thereby, they display particularly excellent effects. Its mixture including the pulverized pulp is molded in a mat shape, and thereby it can favorably be used as the water-absorbent resin layer of the absorbent structure of such as disposable diapers and sanitary napkins.
  • the present inventors certified that making the absorption rate fast without limit conversely leads to lowering the absorption rate under the load. Therefore, the absorption rate is favorably controlled in a suitable range for this use particularly. Controlling a capillary absorption capacity of not less than 7 (g/g) at a height of 40 cm is a critical meaning in the present invention.
  • the present invention water-absorbent resin particles, the ratio of particles passing through a wire net of 150 ⁇ m is not more than 50 % of that before the granulation. Therefore, the present invention also has a merit of little scattering a powdery dust, and provides novel water-absorbent resin particles as hitherto unknown.
  • the present invention is more specifically illustrated by the following examples in comparison with comparative examples.
  • the invention is not limited to these examples.
  • the various performances of the liquid-diffusing members, liquid-acquiring members, water-absorbent resins, absorbent structures, and absorbent articles were measured by the following methods.
  • the absorption abilities of a liquid between a water-absorbent resin and a liquid-diffusing member or liquid-acquiring member are measured under a load of 0.419 kPa (0.06 psi) within a predetermined time at 0 cm (equivalent water level) and at a negative pressure slope of 40 cm.
  • the apparatus and method for measuring these capillary absorption abilities are mentioned with referring to Figs. 1 and 2.
  • a introducing tube 3 is connected to a lower portion of a glass filter 2 (glass filter particle number: #3, Buchner type filter produced by Sogo Rikagaku Glass Seisakusho Co., Ltd., TOP17G-3 (Code No. 1175-03)) having a diameter of 60 mm and a liquid-absorbing face comprised of a porous glass plate 1, and then this introducing tube 3 is connected to a mouth as equipped in a lower portion of a liquid-storing receptacle 4 having a diameter of 10 cm. Then, the porous glass plate in the glass filter has an average porosity diameter of 20 to 30 ⁇ m.
  • a supporting ring 5 for adjusting the height of glass filter 2 is put in, and the system is filled with a physiological saline 6 (a 0.9 weight % aqueous NaCl solution), and the liquid-storing receptacle is put on a balance 7.
  • the glass filter After confi ⁇ ning that there is no air in the introducing tube and at the lower portion of the porous glass plate in the glass filter, the glass filter is adjusted and fixed on a stand 8, so that the height difference between the liquid surface level of an upper portion of the physiological saline 6 in the liquid-storing receptacle and the level of an upper portion of the porous glass plate 1 will be 40 cm.
  • a measuring sample 9 (water-absorbent resin, liquid-diffusing member, or liquid-acquiring member) is put on the porous glass plate 1 under a condition as mentioned below, and a load 10 having a diameter of 59 mm (0.06 psi) is further put thereon, and the value (W 40 ) ofthe physiological saline as absorbed by the measuring sample 9 is measured after 30 minutes.
  • the measuring sample 9 is a water-absorbent resin: 0.44 g of the sample is uniformly and rapidly spread on the glass filter in the funnel.
  • measuring sample 9 is a liquid-diffusing member or liquid-acquiring member: a sample having a diameter of 57 mm and being circularly stamped out is prepared and put on the porous glass plate 1 after its weight (Wi) is measured in a drying state, and then it is measured.
  • Fig.2 Capillary absorption ability at a height of 0 cm
  • a filter paper 17 was put on a glass filter 13 of a measurement apparatus equipped with an open-air-aspirating pipe 11, an introducing tube 12, a glass filter 13, a liquid-storing receptacle 15 for storing a physiological saline 14, and a balance 16 (where, the lower end of the open-air-aspirating pipe 11 sinks in the physiological saline, and the position of the glass filter 13 is fixed very slightly higher than the lower end ofthe open-air-aspirating pipe 11) as shown in Fig. 2.
  • the entire surface ofthe filter paper 17 is in a wet condition with the physiological saline.
  • the measuring sample 9 is put on a wire net of a plastic cylinder 19 having a diameter of 60 mm wherein the bottom of the plastic cylinder 19 is attached by fusion to the wire net 18 of 400 mesh (mesh opening size: 38 ⁇ m) under the above condition, and further a liquid-absorbing instrument on which a load 10 (0.06 psi) having a diameter of 59 mm is mounted is prepared thereon.
  • This liquid-absorbing instrument is put on the filter paper 17 on the glass filter 13, and the value (Wo) of the physiological saline as absorbed by the measuring sample 9 is measured after 30 minutes.
  • capillary absorption capacity G (g/g) of liquid-acquiring member at a height of 40 cm absorption quantity (W 40 ) (g) / weight of measuring sample before absorbing a liquid (Wi) (g)
  • capillary absorption capacity D (g/g) of water-absorbent resin at a height of 40 cm absorption quantity (W 40 ) (g) / 0.44 (g)
  • capillary absorption capacity (g/g) of liquid-diffusing member at a height of 0 cm absorption quantity (Wo) (g) / weight of measuring sample before absorbing a liquid (Wi) (g)
  • a liquid-diffusing member is prepared in a state where the liquid-diffusing member has a width of 2 cm and a length of 90 cm.
  • the liquid-diffusing member is stood vertically at an angle of 90° in such a manner that the lower end of the liquid-diffusing member is immersed in a physiological saline by about 2 cm.
  • the height ofthe liquid as absorbed is measured after 72 hours in such a manner that the liquid is not vaporized.
  • the absorption capacity of the lower end (0 to 10 cm) of the liquid-diffusing member is referred to as 100, and the abso ⁇ tion capacity is each calculated by cutting the member 2 cm by 2 cm with a cutter knife in a direction of height, and the height displaying an absorption capacity that is 90 % of the absorption capacity of the lower end is defined as a suction height of the liquid-diffusing member (cm).
  • the absorption capacity under a load was measured by using the same apparatus of Fig. 2 as of 1-B.
  • the load 20 and the load 21 as adjusted were prepared so that the weight will be each increased instead of the load 10, and the pressure will be 2.07 lcPa (0.3 psi) and 4.83 kPa (0.7 psi).
  • the liquid-diffusing member was beforehand dried and weighed out (Wd) (g). Thereafter, this liquid-diffusing member was immersed into a sufficient amount of a physiological saline (0.9 weight % aqueous NaCl solution). The sample as swollen by absorbing a liquid was taken out from a receptacle, and a portion ofthe sample was supported, and the sample was pulled for 1 minute to drain the liquid off. Thereafter, the weight (We (g)) of the sample that absorbed the liquid was measured at once.
  • Wd physiological saline
  • liquid distribution ratio (%) (We - Wf) / (We - Wd) x 100
  • water-absorbent resin About 14 g was uniformly scattered on Haetlon paper (produced by Teikoku Pulp Industry, GSP-22, and weight per unit area: 22.4 g/m 2 ) in a range of 11 x 38 cm. Thereafter, the water-absorbent resin was sprayed with 5 to 10 weight % of deionized water to moisturize it, and then the water-absorbent resin was molded to form a sheet.
  • Haetlon paper produced by Teikoku Pulp Industry, GSP-22, and weight per unit area: 22.4 g/m 2
  • a poly(vinyl chloride) tube having a diameter of 14.7 cm and a length of 46 cm was cut half in the vertical direction, and plates having a size of 20 x 30 cm were stuck to both ends of the resultant half cylinder in the horizontal direction to prepare a U-shaped instrument.
  • This U-shaped instrument was arranged in a state where the instrument was angled at 90° (shape of C), and then the above model diaper was fixed therein. This state is assumption of a state where a child sleeps on his face and wears the diaper.
  • This diaper was kept at 37 °C together with the above instrument, and 50 cc of a physiological saline continued to be added at an interval of 20 minutes from the center of the diaper in this state assuming sleep-on-face until the leakage was caused.
  • a liquid diffusion ratio of the liquid-diffusing member (%), a total absorption quantity ofthe diaper when the leakage is caused (final weight of diaper - weight of diaper before absorbing a liquid) (g), a liquid absorption quantity of the water-absorbent resin in the diaper (g), and a liquid absorption quantity of the water-absorbent resin in an upper half portion of the diaper (at a side assuming sleep-on-face) (g).
  • the liquid-acquiring member was taken out from the absorbent article, and its weight was measured. The residual liquid amount in the liquid-acquiring member was calculated by subtracting the value from the original weight of the liquid-acquiring member. After the measurement, the liquid-acquiring member was returned to the original absorbent article.
  • Space ratio and average space radius of water-absorbent resin as to spaces between particles when being saturation-swollen, and space ratio and average space radius of water-absorbent resin particles when being saturation-swollen were measured by using the measurement apparatus as shown in Fig. 1
  • the head difference between a tank and a measuring cell in the apparatus of Fig. 1 is lifted from 0 to h (cm).
  • space water preserved in R ( ⁇ m) that is a larger radius than a capillary radius (space) is discharged and gets away.
  • R ( ⁇ m) space water preserved in R ( ⁇ m) that is a larger radius than a capillary radius (space)
  • a saturation-swollen gel of which the spaces are completely filled with a liquid rises from a height of 0 cm, and the remaining amount of the liquid as to spaces is measured each at a predetermined height, thus obtaining the distribution of the space radius (capillary radius) in the swollen gel.
  • the head difference between the tank and the measuring cell is lifted from 0 to 60 (cm), stepwise to 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 30 cm, and 60 cm.
  • a liquid as preserved in a space having a R value that corresponds to each height is discharged.
  • the distribution of the space radius (capillary radius) of the sample can be calculated by measuring this amount of the liquid as discharged, and the values are plotted on logarithmic probability paper, and then the value of d50 is defined as an average space radius.
  • a introducing tube 3 is connected to a lower portion of a glass filter 2 having a diameter of 60 mm, which is equipped with a liquid-absorbing face comprised of a porous glass plate 1 (having a glass filter particle number of #3 and an average porosity diameter of about 20 to about 30 ⁇ , and not introducing air in a state where there is a height difference of 60 cm).
  • This introducing tube 3 is connected to a mouth as equipped in a lower portion of a liquid-storing receptacle 4 having a diameter of 10 cm.
  • a supporting ring 5 for adjusting the height of glass filter 2 is put in, and the system is filled with a physiological saline 6 and the liquid-storing receptacle is put on a balance 7.
  • the glass filter After confirming that there is no air in the introducing tube and at the lower portion of the porous glass plate in the glass filter, the glass filter is adjusted and fixed on a stand 8 so that the height difference between the liquid surface level of an upper portion of the physiological saline 6 in the liquid-storing receptacle and the level of an upper portion ofthe porous glass plate 1 will be 60 cm, and then the value ofthe balance is adjusted to 0.
  • a measuring sample 9 (water-absorbent resin, liquid-diffusing member, or liquid-acquiring member) is put on the porous glass plate 1 under a condition as mentioned below.
  • the measuring sample 9 is a water-absorbent resin: about 0.9 g (W) of the sample is uniformly and rapidly scattered over the glass filter.
  • the measuring sample 9 is an absorbent structure: a sample having a diameter of 57 mm and being circularly stamped out is prepared, and put on the porous glass plate 1 after its weight (W) is measured in a drying state, and then it is measured.
  • the height difference between the liquid surface of the upper portion of the physiological saline 6 in the liquid-storing receptacle 4 and the level of the upper portion in the porous glass plate 1 is adjusted to 0 cm, and the sample is allowed to stand for 40 minutes in order to carrying out saturation and swelling, and then the value of the balance is recorded (A0). Incidentally, the time may be prolonged if the sample is not saturation-swollen for 40 minutes.
  • the height difference between the liquid surface of the upper portion of the physiological saline 6 in the liquid-storing receptacle 4 and the level of the upper portion in the porous glass plate 1 is adjusted to 1 cm, and the value ofthe balance is recorded after 7 minutes (Al). Depending upon the space radius of the sample, there is a case where the equilibrium time until this space water is discharged is favorably prolonged.
  • the height difference between the liquid surface of the upper portion of the physiological saline 6 in the liquid-storing receptacle 4 and the level of the upper portion in the porous glass plate 1 is raised to 2 cm, 5 cm, 10 cm, 20 cm, 30 cm and 60 cm, and then and the value of the balance is each recorded after 7 minutes (A2, A5, A10, A20, A30, and A60).
  • the value (A0 - B) is an amount ofthe total space water in the sample, the values as obtained by subtracting the respective B value from the values (Al, A2, A5, A10,
  • A20, A30, and A60 are accumulated amounts of space water at heights of 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 30 cm and 60 cm. As is mentioned above, it is calculated that the liquids as preserved at positions of 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 30 cm, and 60 cm are preserved at space radiuses (capillary radiuses) of 1,485, 743, 297, 149, 74.3, 49.5, and 24.8 ⁇ m, respectively.
  • the percentage of the accumulated amount of space water relative to the amount of the total space water (A0 - B) is calculated at each height, and then this value and the above capillary radius are plotted on logarithmic probability paper (for example, the value (A2 - B) / (A0 - B) 100 is plotted on 743 ⁇ m in the graph).
  • the value of the space radius corresponding to 50 % of the accumulated space amount (d50) is determined and defined as an average space radius ( ⁇ m) ofthe sample.
  • aqueous monomer solution having a monomer concentration of 35 weight % and a neutralization ratio of 75 % was obtained by using 21.6 parts of acrylic acid, 228.6 parts of 37 weight % aqueous sodium acrylate solution, 0.0185 part of N, N'-methylenebisacrylamide (0.01 mol % relative to monomer), 0.106 part of hydroxyethyl cellulose, and 53 parts of deionized water. Then, 0.09 part of potassium persulfate was dissolved in this aqueous monomer solution, and a nitrogen gas was blo ⁇ vn thereto to remove dissolved oxygen.
  • the resultant particles were transferred to the same separable flask as of that mentioned above, and methanol having an amount (weight) that was 5 times larger than that of the particles was added thereto, and the resultant mixture was stirred at 60 °C for 10 minutes. Subsequently, the mixture was filtrated with a filter paper to separate the particles, and thereafter the particles were dried at 60 °C for 2 hours under a reduced pressure of 50 to 100 mmHg, thus obtaining a water-absorbent resin (1).
  • the water-absorbent resin (1) had a weight-average particle diameter of 105 ⁇ m.
  • the water-absorbent resin displayed a capillary absorption capacity of 45.5 (g/g) at a height of 0 cm, a capillary absorption capacity D of 27.4 (g/g) at a height of 40 cm, and a capillary absorption index B of 0.60 at a height of 40 cm.
  • the crosslinked hydrogel polymer as obtained was in finely divided pieces having a diameter of about 5 mm.
  • This finely divided crosslinked hydrogel polymer was spread on a wire net having 50 mesh, and hot-wind-dried at 150 °C for 90 minutes.
  • the resultant dry material was pulverized with a vibration mill, and further classified with a wire net having 20 mesh, thus obtaining an unshaped pulverized resin having a weight-average particle diameter of 360 ⁇ m, in which the ratio of particles having particle diameters of smaller than 106 ⁇ m was 3 weight %.
  • a surface-crosslinking agent solution including 0.05 part of ethylene glycol diglycidyl ether, 0.75 part of glycerin, 3 parts of water, 0.3 part of lactic acid, and 1 part of isopropyl alcohol was blended.
  • the above mixture was heat-treated at 195 °C for 40 minutes, thus obtaining a water-absorbent resin ( ).
  • the water-absorbent resin (2') as obtained was passed through a wire net having a mesh opening size of 250 ⁇ m, thus obtaining a water-absorbent resin (2) under the sieve.
  • the water-absorbent resin (2) had a weight-average particle diameter of 120 ⁇ m.
  • the water-absorbent resin displayed a capillary absorption capacity of 33.8 (g/g) at a height of 0 cm, a capillary absorption capacity D of 19.4 (g/g) at a height of 40 cm, and a capillary absorption index B of 0.57 at a height of 40 cm.
  • the particle diameter distribution of the water-absorbent resin (2) the ratio of particles having particle diameters of 150 to 850 ⁇ m, and that of particles having particle diameters of not larger than 150 ⁇ m were 31 % and 69 % respectively.
  • the crosslinked hydrogel polymer as obtained was in finely divided pieces having a diameter of about 5 mm.
  • This finely divided crosslinked hydrogel polymer was spread on a wire net having 50 mesh, and hot- wind-dried at 150 °C for 90 minutes.
  • the resultant dry material was pulverized with a vibration mill, thus obtaining an unshaped pulverized resin having a weight-average particle diameter of 400 ⁇ m, which was further passed through a sieve having a mesh opening size of 850. ⁇ m and left on a sieve having a mesh opening size of 106 ⁇ m.
  • a surface-crosslinking agent solution including 0.3 part of 1,4-butanediol, 0.5 part of propylene glycol, and 3 parts of water was blended.
  • the above mixture was heat-treated at 210 °C for 30 minutes, thus obtaining a water-absorbent resin (3).
  • the water-absorbent resin (3) had a weight-average particle diameter of 420 ⁇ m.
  • the water-absorbent resin displayed a capillary absorption capacity of 37.8 (g/g) at a height of 0 cm, a capillary abso ⁇ tion capacity D of 4.30 (g/g) at a height of 40 cm, and a capillary absorption index B of 0.11 at a height of 40 cm.
  • the particle diameter distribution of the water-absorbent resin (3) the ratio of particles having particle diameters of 150 to 850 ⁇ m, and that of particles having particle diameters of not larger than 150 ⁇ m were 95 % and 5 % respectively.
  • a liquid-diffusing member comprised of a porous crosslinked polymer was produced by using a high-internal-phase water-in-oil-type emulsion (HIPE).
  • HIPE high-internal-phase water-in-oil-type emulsion
  • 20.7 parts of anhydrous calcium chloride and 0.415 part of potassium persulfate were dissolved in 394 parts of pure water.
  • 0.654 part of diglycerol monooleate was added to a mixture including 0.438 part of styrene, 5.449 parts of 2-ethylhexyl acrylate, and 3.459 parts of 55 % divinylbenzene, thus obtaining an oil phase.
  • the water phase and the oil phase were continuously supplied to a blending apparatus having two pin type stirring blades, at 80 °C at a feeding rate of 75.2 cm 3 /s, and at 22 °C at a feeding rate of 1.88 g/s, respectively. They were blended with stirring at 1,600 ⁇ m, thus obtaining a high-internal-phase water-in-oil-type emulsion having a temperature of 79 °C.
  • the high-internal-phase water-in-oil-type emulsion as obtained was molded on a driving belt covered with a PET film to obtain a thickness of 5 mm, and the resultant upper face was further covered with a PET film.
  • a curing furnace of which the internal temperature was adjusted to 95 °C was passed at a moving rate of 1.5 m min to polymerize the molded product for 10 minutes, thus obtaining a porous crosslinked polymer in a wet condition.
  • This wet porous crosslinked polymer was dehydrated and dried until its water content was adjusted to 20 %, thus obtaining a liquid-diffusing member (1) comprised of the porous crosslinked polymer having a thickness of 1 mm.
  • the liquid-diffusing member (1) displayed a capillary absorption capacity of 33.6 (g/g) at a height of 0 cm, a capillary absorption capacity C of 14.2 (g/g) at a height of 40 cm, and a capillary absorption index A of 0.42 at a height of 40 cm. In addition, the liquid-diffusing member (1) displayed a suction height of 45 cm.
  • a liquid-diffusing member (2) having a water content of 22 % and a thickness of 1 mm was obtained by the similar procedure except that the oil phase as used in the production process for the liquid-diffusing member (1) was changed to an oil phase obtained by adding 0,654 part of diglycerol monooleate to a mixture including 1.649 parts of styrene, 5.449 parts of 2-ethylhexyl acrylate, and 2.248 parts of 55 % divinylbenzene.
  • the liquid-diffusing member (2) displayed a capillary absorption capacity of 27.0 (g/g) at a height of 0 cm, a capillary absorption capacity C of 7.6 (g/g) at a height of 40 cm, and a capillary absorption index A of 0.28 at a height of 40 cm. In addition, the liquid-diffusing member (2) displayed a suction height of 35 cm.
  • a cotton pulp used for disposable diapers for children was wet and compressed after aspiration, thus obtaining a laminated liquid-diffusing member (3) having a density of 0.03 g/cm 3 and a weight per its unit area of 260 g/m 2 .
  • the liquid-diffusing member (3) displayed a capillary absorption capacity of 6.6 (g/g) at a height of 0 cm, a capillary absorption capacity C of 2.1 (g/g) at a height of 40 cm, and a capillary absorption index A of 0.32 at a height of 40 cm.
  • the liquid-diffusing member (3) displayed a suction height of 30 cm.
  • An absorbent structure (1) was obtained by combining the water-absorbent resin (1) with the liquid-diffusing member (1) according to the method as mentioned in Production Examples of the absorbent structure and absorbent article comprising the liquid-diffusing member.
  • the capillary absorption indexes and capillary absorption capacities of the water-absorbent resin (1) and the liquid-diffusing member (1) as comprised in the above absorbent structure were as shown in each Referential Example.
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (1) at a height of 40 cm to the capillary absorption index A of the liquid-diffusing member (1) at a height of 40 cm
  • the D/C ratio of the capillary absorption capacity D of the water-absorbent resin (1) at a height of 40 cm to the capillary absorption capacity C of the liquid -diffusing member (1) at a height of 40 cm
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was determined by using the absorbent structure (1), and further an absorbent article (1) was produced as a model diaper by using the absorbent structure (1), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount of the diaper when the leakage was caused, the liquid absorption quantity of the water-absorbent resin in the diaper, and the liquid absorption quantity ofthe water-absorbent resin in a half upper portion of the diaper.
  • Example 2 An absorbent structure (2) was obtained by combining the water-absorbent resin (2) with the liquid-diffusing member (1).
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (2) at a height of 40 cm to the capillary absorption index A ofthe liquid-diffusing member (1) at a height of 40 cm
  • the D/C ratio of the capillary absorption capacity D of the water-absorbent resin (2) at a height of 40 cm to the capillary abso ⁇ tion capacity C ofthe liquid-diffusing member (1) at a height of 40 cm
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was determined by using the absorbent structure (2), and further an absorbent article (2) was produced as a model diaper by using the absorbent structure (2), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount ofthe diaper when the leakage was caused, the liquid absorption quantity of the water-absorbent resin in the diaper, and the liquid absorption quantity of the water-absorbent resin in a half upper portion of the diaper.
  • An absorbent structure (3) was obtained by combining the water-absorbent resin (3) with the liquid-diffusing member (1).
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (3) at a height of 40 cm to the capillary absorption index A ofthe liquid-diffusing member (1) at a height of 40 cm
  • the D/C ratio of the capillary absorption capacity D of the water-absorbent resin (3) at a height of 40 cm to the capillary abso ⁇ tion capacity C ofthe liquid-diffusing member (1) at a height of 40 cm
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was determined by using the absorbent structure (3), and further an absorbent article (3) was produced as a model diaper by using the absorbent structure (3), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount of the diaper when the leakage was caused, the liquid absorption quantity of the water-absorbent resin in the diaper, and the liquid absorption quantity ofthe water-absorbent resin in a half upper portion of the diaper.
  • a liquid-diffusing member (1') having a thickness of about 0.5 mm was obtained by slicing up the liquid-diffusing member (1) so that the thickness of the liquid-diffusing member (1') will be a half thickness ofthe liquid-diffusing member (1), and an absorbent structure (4) was obtained by combining the water-absorbent resin (1) therewith.
  • the B/A ratio of the capillary abso ⁇ tion index B of the water-absorbent resin (1) at a height of 40 cm to the capillary absorption index A of the liquid-diffusing member (1') at a height of 40 cm
  • the D/C ratio of the capillary absorption capacity D of the water-absorbent resin (1) at a height of 40 cm to the capillary absorption capacity C of the liquid-diffusing member (1 ') at a height of 40 cm
  • the weight ratio of the water-absorbent resin was 80 weight % relative to the total weight of the water-absorbent resin and the liquid-diffusing member.
  • water-absorbent resin was determined by using the absorbent structure (4), and further an absorbent article (4) was produced as a model diaper by using the absorbent structure (4), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount of the diaper when the leakage was caused, the liquid abso ⁇ tion quantity ofthe water-absorbent resin in the diaper, and the liquid absorption quantity ofthe water-absorbent resin in a half upper portion of the diaper.
  • An absorbent structure (5) was obtained by combining the water-absorbent resin (1) with the liquid-diffusing member (2).
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (1) at a height of 40 cm to the capillary absorption index A ofthe liquid-diffusing member (2) at a height of 40 cm
  • the D/C ratio of the capillary absorption capacity D of the water-absorbent resin (1) at a height of 40 cm to the capillary abso ⁇ tion capacity C ofthe liquid-diffusing member (2) at a height of 40 cm
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was determined by using the absorbent structure (5), and further an absorbent article (5) was produced as a model diaper by using the absorbent structure (5), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount of the diaper when the leakage was caused, the liquid absorption quantity of the water-absorbent resin in the diaper, and the liquid absorption quantity ofthe water-absorbent resin in a half upper portion of the diaper.
  • An absorbent structure (6) was obtained by combining the water-absorbent resin (3) with the liquid-diffusing member (2).
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (3) at a height of 40 cm to the capillary absorption index A ofthe liquid-diffusing member (2) at a height of 40 cm
  • the D/C ratio of the capillary absorption capacity D of the water-absorbent resin (3) at a height of 40 cm to the capillary abso ⁇ tion capacity C ofthe liquid-diffusing member (2) at a height of 40 cm
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was determined by using the absorbent structure (6), and further an absorbent article (6) was produced as a model diaper by using the absorbent structure (6), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount of the diaper when the leakage was caused, the liquid absorption quantity of the water-absorbent resin in the diaper, and the liquid absorption quantity of the water-absorbent resin in a half upper portion of the diaper.
  • Example 4 Comparative Example 2, it would be understood that the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin and the absorption amount of the water-absorbent resin in the diaper are greatly different between absorbent structures which comprise the same liquid-diffusing member but in which the relationship with the capillary absorption ability ofthe water-absorbent resin satisfies the present invention relationship or not.
  • Example 5 Comparative Example 5
  • An absorbent structure (7) was obtained by combining the water-absorbent resin (1) with the liquid-diffusing member (3).
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (1) at a height of 40 cm to the capillary absorption index A ofthe liquid-diffusing member (3) at a height of 40 cm
  • the D/C ratio of the capillary absorption capacity D of the water-absorbent resin (1) at a height of 40 cm to the capillary abso ⁇ tion capacity C ofthe liquid-diffusing member (3) at a height of 40 cm
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was determined by using the absorbent structure (7), and further an absorbent article (7) was produced as a model diaper by using the absorbent structure (7), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount of the diaper when the leakage was caused, the liquid absorption quantity of the water-absorbent resin in the diaper, and the liquid absorption quantity ofthe water-absorbent resin in a half upper portion of the diaper.
  • An absorbent structure (8) was obtained by combining the water-absorbent resin (2) with the liquid-diffusing member (3).
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (2) at a height of 40 cm to the capillary absorption index A ofthe liquid-diffusing member (3) at a height of 40 cm
  • the D/C ratio of the capillary absorption capacity D of the water-absorbent resin (2) at a height of 40 cm to the capillary abso ⁇ tion capacity C ofthe liquid-diffusing member (3) at a height of 40 cm
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was determined by using the absorbent structure (8), and further an absorbent article (8) was produced as a model diaper by using the absorbent structure (8), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount ofthe diaper when the leakage was caused, the liquid absorption quantity of the water-absorbent resin in the diaper, and the liquid absorption quantity ofthe water-absorbent resin in a half upper portion of the diaper.
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (3) at a height of 40 cm to the capillary absorption index A ofthe liquid-diffusing member (3) at a height of 40 cm
  • the D/C ratio of the capillary absorption capacity D of the water-absorbent resin (3) at a height of 40 cm to the capillary abso ⁇ tion capacity C ofthe liquid-diffusing member (3) at a height of 40 cm
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was determined by using the absorbent structure (9), and further an absorbent article (9) was produced as a model diaper by using the absorbent structure (9), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount of the diaper when the leakage was caused, the liquid absorption quantity of the water-absorbent resin in the diaper, and the liquid absorption quantity ofthe water-absorbent resin in a half upper portion of the diaper.
  • the results were listed in Table 2.
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was 66 %, but the liquid absorption ability of the water-absorbent resin from the liquid-diffusing member in a half upper portion of the diaper assumed sleep-on-face was 33 g. From this fact, the liquid absorption ability of the water-absorbent resin may be difficultly displayed in the combination of the water-absorbent resin (3) and the liquid-diffusing member (3) depending upon usage thereof, and therefore it is necessary to pay attention to this matter.
  • Examples 5 to 7 relate to examples in which a liquid-diffusing member having low capillary absorption capacities at heights of 0 and 40 cm was used.
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin is high, and the absorption quantity of the water-absorbent resin in the diaper is large.
  • Example 7 is an example in which only the liquid-diffusion-and-storage coefficient 2 is in the range ofthe present invention.
  • the liquid-diffusing member has low capillary absorption capacities at heights of 0 and 40 cm in Examples 5 to 7, and therefore the total absorption amount ofthe diaper is low. (Comparative Example 3)
  • An absorbent structure (10) was obtained by combining the water-absorbent resin (3) with the liquid-diffusing member (4). It was high that the B/A (ratio of the capillary absorption index B of the water-absorbent resin (3) at a height of 40 cm to the capillary absorption index A of the liquid-diffusing member (4) at a height of 40 cm) was 2.9, and that the D/C (ratio of the capillary absorption capacity D of the water-absorbent resin (3) at a height of 40 cm to the capillary absorption capacity C of the liquid-diffusing member (4) at a height of 40 cm) was 8.1.
  • the capillary abso ⁇ tion capacity C of the liquid-diffusing member (4) was 0.5 (g/g) at a height of 40 cm, and that the capillary absorption index A of the liquid-diffusing member (4) was 0.04 (g/g) at a height of 40 cm, and therefore the liquid diffusion ability was low.
  • the liquid distribution ratio from the liquid-diffusing member to the water-absorbent resin was determined by using the absorbent structure (10), and further an absorbent article (10) was produced as a model diaper by using the absorbent structure (10), and determined were the liquid diffusion ratio in the liquid-diffusing member, the total absorption amount of the diaper when the leakage was caused, the liquid absorption quantity of the water-absorbent resin in the diaper, and the liquid absorption quantity ofthe water-absorbent resin in a half upper portion of the diaper.
  • the results were listed in Table 2.
  • absorbent structure a diaper for children on the market (“Pampers Sarasara Care”; size: L; weight of diaper: 57 g; weight of absorbent structure: 24.0 g; weight of water-absorbent resin: 12.4 g; and weight of cotton pulp: 12.2 g) was used as an absorbent article (11). Determined were the liquid diffusion ratio in the liquid-diffusing member, and the total abso ⁇ tion amount ofthe diaper when the leakage was caused. The results were listed in Table 2, but it was low that the liquid diffusion ratio in the diaper was 62 %.
  • the crosslinked hydrogel polymer as obtained was in finely divided pieces having a diameter of about 5 mm.
  • This finely divided crosslinked hydrogel polymer was spread on a wire net having 50 mesh, and hot- wind-dried at 150 °C for 90 minutes.
  • the resultant dry material was pulverized with a vibration mill, and further classified with a wire net having 20 mesh, thus obtaining an unshaped pulverized resin having a weight-average particle diameter of 340 ⁇ m, in which the ratio of particles having particle diameters of smaller than 106 ⁇ m was 3 weight %.
  • a surface-crosslinldng agent solution including 0.05 part of ethylene glycol diglycidyl ether, 0.9 part of propylene glycol, 3 parts of water, and 1 part of isopropyl alcohol was blended.
  • the above mixture was heat-treated at 195 °C for 40 minutes, thus obtaining a water-absorbent resin (4).
  • the water-absorbent resin (4) had a weight-average particle diameter of 347 ⁇ m.
  • the water-absorbent resin (4) displayed a capillary absorption capacity of 39.9 (g/g) at a height of 0 cm, a capillary absorption capacity D of 11.4 (g/g) at a height of 40 cm, and a capillary absorption index B of 0.29 at a height of 40 cm.
  • the crosslinked hydrogel polymer as obtained was in finely divided pieces having a diameter of about 5 mm.
  • This finely divided crosslinked hydrogel polymer was spread on a wire net having 50 mesh, and hot- wind-dried at 150 °C for 90 minutes.
  • the resultant dry material was pulverized with a vibration mill, and further classified with a wire net having 20 mesh, thus obtaining an unshaped pulverized resin having a weight-average particle diameter of 400 ⁇ m, which was further passed through a sieve having a mesh opening size of 850 ⁇ m and left on a sieve having a mesh opening size of 106 ⁇ m.
  • a surface-crosslinking agent solution including 0.3 part of 1,4-butanediol, 0.5 part of propylene glycol, and 3 parts of water was blended. The above mixture was heat-treated at 210 °C for 30 minutes. Thereafter, 0.5 part of hydrophilic silicon dioxide fine powder (Aerosil 200, produced by Nippon Aerosil Co., Ltd.) was added thereto in order to coat the surface portion therewith, thus obtaining a water-absorbent resin (5).
  • the water-absorbent resin (5) had a weight-average particle diameter of 500 ⁇ m.
  • the water-absorbent resin (5) displayed a capillary absorption capacity of 37.4 (g/g) at a height of 0 cm, a capillary absorption capacity D of 2.8 (g/g) at a height of 40 cm, and a capillary absorption index B of 0.08 at a height of 40 cm.
  • liquid-acquiring member (1) having a size of 8 cm x 30 cm, wherein the crosslinked cellulose was in a state where its upper and lower portions were covered with nonwoven fabrics.
  • the liquid-acquiring member (1) displayed a capillary absorption capacity of 14.4 (g/g) at a height of 0 cm, a capillary absorption capacity C of 0.18 (g/g) at a height of 40 cm, and a capillary absorption index A of
  • the liquid-acquiring member (2) displayed a capillary absorption capacity of 13.8 (g/g) at a height of 0 cm, a capillary absorption capacity C of 0.53 (g/g) at a height of 40 cm, and a capillary absorption index A of 0.038 at a height of 40 cm.
  • Example 8 A water-absorbent resin layer having a scattering amount of 360 g/m was formed by scattering 16.4 g of the water-absorbent resin (4) over an area of 12 cm 38 cm, and then the liquid-acquiring member (1) (12 cm x 24 cm, and weight: 3.8 g) was mounted thereon according to the aforementioned preparation method, thus obtaining an absorbent structure (12).
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (4) at a height of 40 cm to the capillary absorption index A ofthe liquid-acquiring member (1) at a height of 40 cm
  • the capillary abso ⁇ tion capacity C of the liquid-acquiring member (1) was 0.18 (g/g) at a height of 40 cm
  • the capillary absorption capacity D of the water-absorbent resin (4) was 11.4 (g/g) at a height of 40 cm.
  • An absorbent article (12) was produced as a model diaper by using the absorbent structure (12) according to the aforementioned preparation method, and determined were the liquid-absorbing time, the whitening time, the residual liquid amount in the liquid-acquiring member, and the amount of wet back of the aqueous liquid.
  • the results were listed in Table 3, and it would be understood that the water-absorbent resin layer absorbs favorably a liquid from the liquid-acquiring member, and the diaper having excellent dry feeling is obtained, because the whitening time was also fast, and the residual liquid amount in the liquid-acquiring member was small, and the amount of wet back ofthe aqueous liquid was also small.
  • Example 9 An absorbent structure (13) was obtained by combining the water-absorbent resin (2) with the liquid-acquiring member (1) in the same way as of Example 8.
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (2) at a height of 40 cm to the capillary absorption index A of the liquid-acquiring member (1) at a height of 40 cm
  • the capillary absorption capacity of the liquid-acquiring member (1) was 0.18 (g/g) at a height of 40 cm
  • the capillary absorption capacity D of the water-absorbent resin (2) was 19.4 (g/g) at a height of 40 cm.
  • An absorbent article (13) was produced as a model diaper by using the absorbent structure (13) according to the aforementioned preparation method, and determined were the liquid-absorbing time, the whitening time, the residual liquid amount in the liquid-acquiring member, and the amount of wet back of the aqueous liquid.
  • the results were listed in Table 3, and it would be understood that the water-absorbent resin layer absorbs favorably a liquid from the liquid-acquiring member, and the diaper having excellent dry feeling is obtained, because the whitening time was also fast, and the residual liquid amount in the liquid-acquiring member was small, and the amount of wet back ofthe aqueous liquid was also small. (Example 10)
  • An absorbent structure (14) was obtained by combining the water-absorbent resin (1) with the liquid-acquiring member (1) in the same way as of Example 8.
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (1) at a height of 40 cm to the capillary absorption index A of the liquid-acquiring member (1) at a height of 40 cm
  • the capillary abso ⁇ tion capacity of the liquid-acquiring member (1) was 0.18 (g/g) at a height of 40 cm
  • the capillary absorption capacity D of the water-absorbent resin (1) was 27.4 (g/g) at a height of 40 cm.
  • An absorbent article (14) was produced as a model diaper by using the absorbent structure (14) according to the aforementioned preparation method, and determined were the liquid-absorbing time, the whitening time, the residual liquid amount in the liquid-acquiring member, and the amount of wet back of the aqueous liquid.
  • the results were listed in Table 3, and it would be understood that the water-absorbent resin layer absorbs favorably a liquid from the liquid-acquiring member, and the diaper having excellent dry feeling is obtained, because the whitening time was also fast, and the residual liquid amount in the liquid-acquiring member was small, and the amount of wet back ofthe aqueous liquid was also small.
  • An absorbent structure (15) was obtained by combining the water-absorbent resin (4) with the liquid-acquiring member (2) in the same way as of Example 8.
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (4) at a height of 40 cm to the capillary absorption index A of the liquid-acquiring member (2) at a height of 40 cm
  • the capillary abso ⁇ tion capacity of the liquid-acquiring member (2) was 0.53 (g/g) at a height of 40 cm
  • the capillary abso ⁇ tion capacity D of the water-absorbent resin (4) was 11.4 (g/g) at a height of 40 cm.
  • An absorbent article (15) was produced as a model diaper by using the absorbent structure (15) according to the aforementioned preparation method, and determined were the liquid-absorbing time, the whitening time, the residual liquid amount in the liquid-acquiring member, and the amount of wet back of the aqueous liquid.
  • the results were listed in Table 3, and it would be understood that the water-absorbent resin layer absorbs favorably a liquid from the liquid-acquiring member, and the diaper having excellent dry feeling is obtained, because the whitening time was also fast, and the residual liquid amount in the liquid-acquiring member was small, and the amount of wet back ofthe aqueous liquid was also small.
  • An absorbent article (16) was produced as a model diaper by using the absorbent structure (16) according to the aforementioned preparation method, and determined were the liquid-absorbing time, the whitening time, the residual liquid amount in the liquid-acquiring member, and the amount of wet back of the aqueous liquid.
  • the results were listed in Table 4, and it would be understood that the liquid absorption cannot smoothly be carried out from the liquid-acquiring member to the water-absorbent resin layer, because the whitening time was late, and the residual liquid amount in the liquid-acquiring member and the amount of wet back of the aqueous liquid were also large.
  • ⁇ Comparative Example 6
  • An absorbent structure (17) was obtained by combining the water-absorbent resin (3) with the liquid-acquiring member (1) in the same way as of Example 8.
  • the B/A ratio of the capillary absorption index B of the water-absorbent resin (3) at a height of 40 cm to the capillary absorption index A of the liquid-acquiring member (1) at a height of 40 cm
  • the capillary abso ⁇ tion capacity of the liquid-acquiring member (1) was 0.18 (g/g) at a height of 40 cm
  • the capillary absorption capacity D of the water-absorbent resin (3) was 4.3 (g/g) at a height of 40 cm.
  • An absorbent article (17) was produced as a model diaper by using the absorbent structure (17) according to the aforementioned preparation method, and determined were the liquid-absorbing time, the whitening time, the residual liquid amount in the liquid-acquiring member, and the amount of wet back of the aqueous liquid. The results were listed in Table 4, and it would be understood that the liquid absorption cannot smoothly be carried out from the liquid-acquiring member to the water-absorbent resin layer, because the whitening time was late, and the amount of wet back ofthe aqueous liquid was also large.
  • Comparative Example 7 A blended core having a size of 12 cm 38 cm was prepared by blending 8.2 g o the water-absorbent resin (4) with 8.2 g of cotton pulp used for disposable diapers for children.
  • the capillary absorption abilities of these materials were listed in Table 4.
  • the liquid-acquiring member (1) and the above blended core were combined in using amounts as mentioned in Table 4, thus obtaining an absorbent structure (18).
  • the B/A ratio of the capillary abso ⁇ tion index B of the above blended core at a height of 40 cm to the capillary absorption index A of the liquid-acquiring member (1) at a height of 40 cm
  • the capillary absorption capacity of the liquid-acquiring member (1) was 0.18 (g/g) at a height of 40 cm
  • the capillary absorption capacity D of the above blended core was 2.3 (g/g) at a height of 40 cm.
  • An absorbent article (18) was produced as a model diaper by using the absorbent structure (18) according to the aforementioned preparation method, and determined were the liquid absorption rate, the rate of drying the liquid-diffusing member, the residual liquid amount in the liquid-acquiring member after 1 hour, and the amount of wet back of the aqueous liquid.
  • the results were listed in Table 4, and it would be understood that the liquid absorption cannot smoothly be carried out from the liquid-acquiring member to the water-absorbent resin layer, because the whitening time was late, and the residual liquid amount in the liquid-acquiring member and the amount of wet back ofthe aqueous liquid were also large. (Comparative Example 8)
  • An absorbent structure (19) was prepared in the same way as of Example 8 except for not using the liquid-diffusing member, and determined were the liquid absorption rate, the rate of drying the liquid-diffusing member, the residual liquid amount in the liquid-acquiring member after 1 hour, and the amount of wet back of the aqueous liquid. The results were listed in Table 4, and it would be understood that the liquid-absorbing time is very late, and the liquid is not smoothly absorbed. Table 3
  • Water-absorbent resin 82 g+cotton pulp 82 g (Referential Example 12): Production process for water-absorbent resin
  • the resultant dry material was pulverized with a vibration mill, and further classified with a wire net having 30 mesh, thus obtaining an unshaped pulverized water-absorbent resin precursor having a weight-average particle diameter of 280 ⁇ m, in which the ratio of particles having particle diameters of smaller than 106 ⁇ m was 5 weight %.
  • a surface-crosslinking agent solution including 0.05 part of ethylene glycol diglycidyl ether, 0.9 part of propylene glycol, 3 parts of water, and 1 part of isopropyl alcohol was blended.
  • the above mixture was heat-treated at 195 °C for 40 minutes, thus obtaining a water-absorbent resin (6).
  • the water-absorbent resin (6) had a weight-average particle diameter of 265 ⁇ m.
  • the water-absorbent resin (6) displayed a capillary absorption capacity D of 11.4 (g/g) at a height of 40 cm.
  • D capillary absorption capacity
  • Dispersion of water-dispersible fine particles Five parts by weight of Aerosil 200 (super-fine particles of silicon dioxide, produced by Nippon Aerosil Co., Ltd.) as water-dispersible fine particles was blended into 70 parts by weight of deionized water with a high-speed continuous blender (2,000 ⁇ m) for 2 hours. After the blending, the resultant mixture was allowed to stand at room temperature for 24 hours, thus obtaining a dispersion ofthe water-dispersible fine particles. The viscosity ofthe water-dispersible fine particles was 1,000 cps.
  • Example 12 To 100 parts by weight of the water-absorbent resin (6), 7 parts by weight of the dispersion of the water-dispersible fine particles as obtained in Referential Example 13 was added and blended. After the resultant mixture was allowed to stand at 60 °C for 30 minutes, the mixture was ground, and the entire particles was passed through a wire net with a mesh opening size of 850 ⁇ m, thus obtaining water-absorbent resin particles (1) according to the present invention. As to the particle diameter distribution of these particles, particles having particle diameters of 150 to 850 ⁇ m and particles having particle diameters of smaller than 150 ⁇ m accounted for 97 weight % and 3 weight % respectively. In addition, the particles have a weight-average particle diameter of 500 ⁇ m. The results were listed in Table 5.
  • An absorbent article (20) was produced as a model diaper by using the water-absorbent resin particles (1) and the liquid-acquiring member (2) as obtained according to the aforementioned method.
  • the liquid-absorbing time, the diffusion area, and the amount of wet back of the aqueous liquid were evaluated according to the above evaluation method, and the results were listed in Table 5.
  • Example 13 A dispersion was obtained by blending 7 parts by weight of the dispersion of the water-dispersible fine particles as obtained in Referential Example 13 and 13 parts by weight of deionized water. To 100 parts by weight of the water-absorbent resin (2), 20 parts by weight of the dispersion was added and blended.
  • the resultant mixture was allowed to stand at 60 °C for 30 minutes, the mixture was ground, and the entire particles was passed through a wire net with a mesh opening size of 850 ⁇ m, thus obtaining water-absorbent resin particles (2) according to the present invention.
  • particles having particle diameters of 150 to 850 ⁇ m and particles having particle diameters of smaller than 150 ⁇ m accounted for 85 weight % and 15 weight % respectively.
  • the particles have a weight-average particle diameter of 308 ⁇ m.
  • An absorbent article (21) was produced as a model diaper by using the water-absorbent resin particles (2) and the liquid-acquiring member (2) as obtained according to the aforementioned method.
  • the liquid-absorbing time, the diffusion area, and the amount of wet back of the aqueous liquid were evaluated according to the above evaluation method, and the results were listed in Table 5. (Comparative Example 9)
  • the water-absorbent resin (2) To 100 parts by weight ofthe water-absorbent resin (2), 0.5 part by weight of Aerosil 200 (silicon dioxide fine powder, produced by Nippon Aerosil Co., Ltd.) was added to blend the water-absorbent resin, and further 20 parts by weight of deionized water was added thereto and blended. After the resultant mixture was allowed to stand at 60 °C for 30 minutes, the mixture was ground, and the entire particles was passed through a wire net with a mesh opening size of 850 ⁇ m, thus obtaining water-absorbent resin particles (3). As to the particle diameter distribution of these particles, particles having particle diameters of 150 to 850 ⁇ m and particles having particle diameters of smaller than 150 ⁇ m accounted for 59 weight % and 41 weight % respectively. In addition, the particles have a weight- average particle diameter of 174 ⁇ m.
  • Aerosil 200 silicon dioxide fine powder, produced by Nippon Aerosil Co., Ltd.
  • An absorbent article (22) was produced as a model diaper by using the water-absorbent resin particles (3) and the liquid-acquiring member (2) as obtained according to the aforementioned method.
  • the liquid-absorbing time, the diffusion area, and the amount of wet back of the aqueous liquid were evaluated according to the above evaluation method, and the results were listed in Table 5. (Comparative Example 10)
  • the water-absorbent resin (2) To 100 parts by weight ofthe water-absorbent resin (2), 20 parts by weight of deionized water was added thereto and blended. After the resultant mixture was allowed to stand at 60 °C for 30 minutes, the mixture was ground, and the entire particles was passed through a wire net with a mesh opening size of 850 ⁇ m, thus obtaining water-absorbent resin particles (4).
  • the particle diameter distribution of these particles particles having particle diameters of 150 to 850 ⁇ m and particles having particle diameters of smaller than 150 ⁇ m accounted for 61 weight % and 39 weight % respectively. In addition, the particles have a weight-average particle diameter of 180 ⁇ m, but they were fragile and easily destroyed.
  • An absorbent article (23) was produced as a model diaper by using the water-absorbent resin particles (4) and the liquid-acquiring member (2) as obtained according to the aforementioned method.
  • the liquid-absorbing time, the diffusion area, and the amount of wet back of the aqueous liquid were evaluated according to the above evaluation method, and the results were listed in Table 5. (Comparative Example 11)
  • An absorbent article (24) was produced as a model diaper by using the water-absorbent resin (2) and the liquid-acquiring member (2) as obtained according to the aforementioned method.
  • the liquid-absorbing time, the diffusion area, and the amount of wet back of the aqueous liquid were evaluated according to the above evaluation method, and the results were listed in Table 5.
  • dusts were scattered and its handling was difficult.
  • An absorbent article (25) was produced as a model diaper by using the water-absorbent resin (3) and the liquid-acquiring member (2) as obtained according to the aforementioned method.
  • the liquid-absorbing time, the diffusion area, and the amount of wet back of the aqueous liquid were evaluated according to the above evaluation method, and the results were listed in Table 5.
  • the present invention can provide: an absorbent structure and an absorbent article, in which, in the absorbent structure and the absorbent article comprising a liquid-diffusing member and a water-absorbent resin, a liquid is sufficiently transferred and absorbed from the liquid-diffusing member to the water-absorbent resin even if an auxiliary material such as a material having a large surface area is not used, namely which are excellent in both liquid diffusion ability and liquid storage ability; and a water-absorbent resin fitly usable for the above absorbent structure and absorbent article.
  • the present invention can provide: an absorbent structure and an absorbent article, in which, in the absorbent structure and the absorbent article comprising a liquid-acquiring member and a water-absorbent resin, a liquid is favorably transferred from the liquid-acquiring member to the water-absorbent resin even if the concentration of the water-absorbent resin is raised more, and the liquid-acquiring function is not lowered so much even if the liquid is repeatedly absorbed, and which are excellent in the dry feeling and the amount of wet back of the aqueous liquid, and which can realize the thinning and lightening more; and a water-absorbent resin fitly usable for the above absorbent structure and absorbent article.

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  • Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Epidemiology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Vascular Medicine (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Biomedical Technology (AREA)
  • Organic Chemistry (AREA)
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  • Polymers & Plastics (AREA)
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  • Dispersion Chemistry (AREA)
  • Materials Engineering (AREA)
  • Hematology (AREA)
  • Absorbent Articles And Supports Therefor (AREA)

Abstract

La présente invention concerne une structure absorbante ainsi qu'un article absorbant, lesquels présentent une excellente capacité à la fois de diffusion de liquide et de conservation de liquide, et lesquels présentent une excellente sensation à sec de même que dans la quantité de remouillage du liquide aqueux, et dont la minceur et la légèreté sont améliorées ; ainsi qu'une résine absorbant l'eau pouvant être utilisée avantageusement pour la structure absorbante ainsi que l'article absorbant précités. La structure absorbante, selon la présente invention, comprend un élément diffusant le liquide ainsi qu'une résine absorbant l'eau, la structure absorbante étant caractérisée en ce que lorsque l'indice d'absorption capillaire de l'élément diffusant le liquide, à une hauteur de 40 cm, se présente ainsi A (A ≥ 0,10), l'indice B d'absorption capillaire de la résine absorbant l'eau, à une hauteur de 40 cm, satisfait l'équation suivante : B/A ≥ 0,7.
EP02799478A 2001-09-19 2002-09-18 Structure absorbante, article absorbant, resine absorbant l'eau et sa production Withdrawn EP1429703A2 (fr)

Applications Claiming Priority (9)

Application Number Priority Date Filing Date Title
JP2001285752 2001-09-19
JP2001285752 2001-09-19
JP2001375375 2001-12-10
JP2001375375 2001-12-10
JP2002072476 2002-03-15
JP2002072476 2002-03-15
JP2002106565 2002-04-09
JP2002106565 2002-04-09
PCT/JP2002/009567 WO2003026707A2 (fr) 2001-09-19 2002-09-18 Structure absorbante, article absorbant, resine absorbant l'eau et sa production

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JP4340564B2 (ja) * 2004-03-15 2009-10-07 株式会社リブドゥコーポレーション 使い捨て吸収性物品
AU2005210411B2 (en) 2004-02-05 2008-01-31 Nippon Shokubai Co., Ltd. Particulate water absorbing agent and method for production thereof, and water absorbing article
DE602006021004D1 (de) 2005-05-13 2011-05-12 Asahi Kasei Chemicals Corp Absorbierendes verbundmaterial und herstellungsverfahren dafür
TWI394789B (zh) 2005-12-22 2013-05-01 Nippon Catalytic Chem Ind 吸水性樹脂組成物及其製造方法、吸收性物品
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CN108348385B (zh) 2015-11-04 2021-06-15 宝洁公司 吸收结构
RU2693630C1 (ru) 2015-11-04 2019-07-03 Дзе Проктер Энд Гэмбл Компани Абсорбирующая структура
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