US20220071818A9 - Thin fluid absorbent core-absorbent paper - Google Patents

Thin fluid absorbent core-absorbent paper Download PDF

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Publication number
US20220071818A9
US20220071818A9 US17/048,354 US201917048354A US2022071818A9 US 20220071818 A9 US20220071818 A9 US 20220071818A9 US 201917048354 A US201917048354 A US 201917048354A US 2022071818 A9 US2022071818 A9 US 2022071818A9
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Prior art keywords
water
polymer particles
absorbent
weight
fluid
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US20210169709A1 (en
Inventor
Stephan Bauer
Katrin Baumann
Norbert Herfert
Li Guo DUAN
Le Li
Xiao Yan LIU
Gao Min SUN
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BASF SE
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BASF SE
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Assigned to BASF SE reassignment BASF SE ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BASF ADVANCED CHEMICALS CO., LTD.
Assigned to BASF SE reassignment BASF SE ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BASF (CHINA) COMPANY LIMITED
Assigned to BASF ADVANCED CHEMICALS CO., LTD. reassignment BASF ADVANCED CHEMICALS CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DUAN, Li Guo, HERFERT, NORBERT
Assigned to BASF (CHINA) COMPANY LIMITED reassignment BASF (CHINA) COMPANY LIMITED ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LI, LE, LIU, XIAO YAN, SUN, Gao Min
Assigned to BASF SE reassignment BASF SE ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BAUER, STEPHAN, BAUMANN, KATRIN
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • 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
    • A61L15/22—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing macromolecular materials
    • A61L15/24—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof
    • 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
    • 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
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F2013/530437—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 a part with elevated absorption means
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F2013/530481—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F2013/530481—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials
    • A61F2013/530583—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials characterized by the form
    • A61F2013/530591—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials characterized by the form in granules or particles
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F2013/530481—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials
    • A61F2013/530708—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials characterized by the absorbency properties

Definitions

  • the present invention relates to fluid absorbent cores ( 80 ) comprising at least one absorption layer, the layer comprising at least 80% by weight of water-absorbent polymer particles, 0 to 10% by weight of an adhesive and from 0 to 10% by weight of fibrous material, wherein the water-absorbent polymer particles within the absorption layer are water-absorbent polymer particles H having a vortex of 40 s or less and having a roundness of 0.79 to 0.85 and/or a CRC of 38 g/g to 85 g/g.
  • the current commercially available disposable diapers consist typically of a liquid-pervious topsheet ( 89 ), a liquid-impervious backsheet ( 83 ), a water-absorbing storage layer (absorbent core) ( 80 ) between layers ( 89 ) and ( 83 ), and an acquisition distribution layer ( 70 ) between layers ( 89 ) and ( 80 ).
  • the several layers of fluid-absorbent articles fulfill definite functions such as dryness for the upper liquid-pervious layer, vapor permeability without wetting through for the lower liquid-impervious layer, a flexible, vapor permeable and fluid-absorbent core, showing fast absorption rates and being able to retain quantities of body fluids and an optional acquisition-distribution layer between the upper layer and the core, acting as transport and distribution layer of the discharged body fluids.
  • water-absorbing polymer particles The preparation of water-absorbing polymer particles is generally described in the monograph “Modern Superabsorbent Polymer Technology”, F. L. Buchholz and A. T. Graham, Wiley-VCH, 1998, pages 71 to 103.
  • the water-absorbing polymer particles are also referred to as “fluid-absorbing polymer particles”, “superabsorbent polymers” or “superabsorbents”.
  • a core-structure for thin fluid-absorbent products can be formed from absorbent paper.
  • absorbent paper Such structures are for example described in WO2011/086842, EP 2 565 031 A1, EP 2 668 936 A1.
  • the known thin fluid-absorbent products comprising absorbent paper structures have deficiencies in respect to fluid acquisition, leakage and rewet properties.
  • Another problem is gel blocking as the low amount of fibers or even the absence of fibers within the absorbent core. Upon absorption of liquid the water absorbent polymer particles form a soft gel so that liquid permeation into an internal of the absorbent material is blocked.
  • the reduction of fibers mal lead to problems with fixing the water-absorbent polymer particles and to reduce the shape retaining ability of the core so that deformation occur before or after liquid absorption.
  • It is therefore an object of the present invention prevent gel blocking to provide a fluid-absorbent core for fluid-absorbent products with an improved performance even when containing no or only a small amount of fibers (at maximum 10% by weight of fibrous material).
  • the extractables ( 16 h ) content is low as extractables are leaking out of the swollen gel particles over time, thereby reducing the absorbency of the SAP. As a result the rewet increases over time.
  • a fluid-absorbent core ( 80 ) comprising at least one absorption layer, the layer comprising at least 80% by weight of water-absorbent polymer particles, 0 to 10% by weight of an adhesive and from 0 to 10% by weight of fibrous material, wherein the water-absorbent polymer particles within the absorption layer are water-absorbent polymer particles H having a vortex of 40 s or less and having a roundness of 0.79 to 0.85 and/or a CRC of 38 g/g to 85 g/g.
  • the water-absorbent polymer particles H are surface post-crosslinked.
  • the fluid-absorbent core ( 80 ) comprises at least two absorption layers, an upper layer ( 91 ) and a bottom layer ( 92 ), wherein at least the bottom layer ( 92 ) comprises water-absorbent polymer particles H.
  • At least one layer of nonwoven material ( 94 ) is sandwiched between the upper layer ( 91 ) and the lower layer ( 92 ).
  • the water-absorbent polymer particles H having a CRC of 38 g/g to 85 g/g, preferably of 40 g/g to 80 g/g, more preferably of 42 g/g to 75 g/g.
  • the Water Pouring Time of the inventive the flu-id absorbent core ( 80 ) is 28 s or less and the Water Pouring Rewet the fluid absorbent core ( 80 ) is 3.5 g or less measured according to the method “Water pouring test” disclosed herein.
  • the fluid absorbent core ( 80 ) having a Liquid Diffusion Length of at least 245 mm, a total strike-thru time of 45 s or less and a Total Rewet of 40 g or less measured according to the method “Strike-thru/Rewet” disclosed in the description.
  • the inventive fluid-absorbent core may be part of absorbent articles.
  • an inventive absorbent article comprising
  • fluid-absorbent article refers to any three-dimensional solid material being able to acquire and store fluids discharged from the body.
  • Preferred fluid-absorbent articles are disposable fluid-absorbent articles that are designed to be worn in contact with the body of a user such as disposable fluid-absorbent pantyliners, sanitary napkins, catamenials, incontinence inserts/pads, diapers, training pant diapers, breast pads, interlabial inserts/pads or other articles useful for absorbing body fluids.
  • fluid-absorbent composition refers to a component of the fluid-absorbent article which is primarily responsible for the fluid handling of the fluid-absorbent article including acquisition, transport, distribution and storage of body fluids.
  • fluid-absorbent core refers to a fluid-absorbent composition comprising at least one, preferably at least two layers including an upper layer and a lower layer of water-absorbent polymer particles and optionally fibrous material (at maximum 10% by weight of fibrous material); nonwoven material and tissue material and optionally adhesive.
  • the fluid-absorbent core is primarily responsible for the fluid handling of the fluid-absorbent article including acquisition, transport, distribution and storage of body fluids.
  • a fluid absorbent core according to the invention is shown in FIG. 2 .
  • a layer refers to a fluid-absorbent composition whose primary dimension is along its length and width.
  • a layer usually comprises water-absorbent polymer particles and optionally fibrous material, a layer can comprise laminates, composites, combinations of several sheets or webs of different materials.
  • x-dimension refers to the length
  • y-dimension refers to the width of the fluid-absorbent composition, layer, core or article.
  • x-y-dimension refers to the plane, orthogonal to the height or thickness of the fluid-absorbent composition, layer, core or article.
  • z-dimension refers to the dimension orthogonal to the length and width of the fluid absorbent composition, layer, core or article. Generally, the term “z-dimension” refers to the height of the fluid-absorbent composition, layer, core or article.
  • the term “basis weight” indicates the weight of the fluid-absorbent core or any tissue per square meter and does not include the chassis of the fluid-absorbent article.
  • the basis weight is determined at least at two different regions of the fluid-absorbent core or any tissue respectively and is taken as the average of the at least two results.
  • the term “upper” refers to fluid-absorbent composition which are nearer to the wearer of the fluid-absorbent article.
  • the topsheet in an absorbent article is the nearest composition to the wearer of the fluid-absorbent article, hereinafter described as “upper liquid-pervious layer”.
  • the term “lower” refers to fluid-absorbent compositions which are away from the wearer of the fluid-absorbent article.
  • the backsheet is the component which is furthermost away from the wearer of the fluid-absorbent article, hereinafter described as “lower liquid-impervious layer”.
  • liquid-pervious refers to a substrate, layer or a laminate thus permitting liquids, i.e. body fluids such as urine, menses and/or vaginal fluids to readily penetrate through its thick-ness.
  • liquid-impervious refers to a substrate, layer or a laminate that does not allow body fluids to pass through in a direction generally perpendicular to the plane of the layer at the point of liquid contact under ordinary use conditions.
  • hydrophobic refers to fibers showing a contact angle of greater than 90° or no spontaneously spreading of the liquid across the surface of the fiber.
  • body fluids refers to any fluid produced and discharged by human or animal body, such as urine, menstrual fluids, faeces, vaginal secretions and the like.
  • the term “longitudinal” refers to a direction running perpendicular from a waist edge to an opposing waist edge of the fluid-absorbent article.
  • the monomers a) are preferably water-soluble, i.e. the solubility in water at 23° C. is typically at least 1 g/100 g of water, preferably at least 5 g/100 g of water, more preferably at least 25 g/100 g of water, most preferably at least 35 g/100 g of water.
  • Suitable monomers a) are, for example, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid. Particularly preferred monomers are acrylic acid and methacrylic acid. Very particular preference is given to acrylic acid having a concentration of diacrylic acid from 0 to 2% by weight, more preferably 0.0001 to 1% by weight, most preferably from 0.0002 to 0.5% by weight.
  • the acid groups of the monomers a) are typically partly neutralized, preferably to an extent of from 25 to 85 mol %, preferentially to an extent of from 50 to 80 mol %, more preferably from 60 to 75 mol %, for which the customary neutralizing agents can be used, preferably alkali metal hydroxides, alkali metal oxides, alkali metal carbonates or alkali metal hydrogen carbonates, and mixtures thereof.
  • Acrylic acid typically comprises polymerization inhibitors, preferably hydroquinone monoethers, as storage stabilizers.
  • Suitable crosslinkers b) are compounds having at least two groups suitable for crosslinking. Such groups are, for example, ethylenically unsaturated groups which can be polymerized by a free-radical mechanism into the polymer chain and functional groups which can form covalent bonds with the acid groups of monomer a). In addition, polyvalent metal ions which can form coordinate bond with at least two acid groups of monomer a) are also suitable crosslinkers b).
  • the crosslinkers b) are preferably compounds having at least two free-radically polymerizable groups which can be polymerized by a free-radical mechanism into the polymer network.
  • Suitable crosslinkers b) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallylammonium chloride, tetraallyloxyethane, as described in EP 0 530 438 A1, di- and tri-acrylates, as described in EP 0 547 847 A1, EP 0 559 476 A1, EP 0 632 068 A1, WO 93/21237 A1, WO 2003/104299 A1, WO 2003/104300 A1, WO 2003/104301 A1 and in DE 103 31 450 A1, mixed acrylates which, as well as acrylate groups, comprise further ethylenically unsaturated groups, as described in DE 103 314 56 A1 and DE 103 55 401 A1, or crosslinker mixtures, as described, for example, in DE 195 43 368 A1, DE 196 46 4
  • the amount of crosslinker b) is preferably from 0.0001 to 0.6% by weight, more preferably from 0.0015 to 0.2% by weight, most preferably from 0.01 to 0.06% by weight, based in each case on monomer a).
  • the centrifuge retention capacity (CRC) decreases and the absorption under a pressure of 21.0 g/cm 2 (AUL) passes through a maximum.
  • the initiators c) used may be all compounds which disintegrate into free radicals under the polymerization conditions, for example peroxides, hydroperoxides, hydrogen peroxide, persulfates, azo compounds and redox initiators. Preference is given to the use of water-soluble initiators. In some cases, it is advantageous to use mixtures of various initiators, for example mixtures of hydrogen peroxide and sodium or potassium peroxodisulfate. Mixtures of hydrogen peroxide and sodium peroxodisulfate can be used in any proportion.
  • the initiators c) should be water-soluble.
  • the reducing component used is, however, preferably a mixture of the sodium salt of 2-hydroxy-2-sulfinatoacetic acid, the disodium salt of 2-hydroxy-2-sulfonatoacetic acid and sodium bisulfite.
  • Such mixtures are obtainable as Bruggolite® FF6 and Bruggolite® FF7 (Brüggemann Chemicals; Heilbronn; Germany).
  • Bruggolite® FF6 and Bruggolite® FF7 Bruggolite® FF7
  • a combination of at least one persulfate c1) and at least one azo initiator c2) is used as initiator c).
  • the amount of persulfate c1) to be used is preferably from 0.01 to 0.25% by weight, more preferably from 0.05 to 0.2% by weight, most preferably from 0.1 to 0.15% by weight, each based on monomer a). If the amount of persulfate is too low, a sufficient low level of residual monomers cannot be achieved. If the amount of persulfate is too high, the water-absorbent polymer particles do not have a sufficient whiteness and may suffer degradation upon heating.
  • the amount of azo initiator c2) to be used is preferably from 0.1 to 2% by weight, more preferably from 0.15 to 1% by weight, most preferably from 0.2 to 0.5% by weight, each based on monomer a). If the amount of azo initiator is too low, a high centrifuge retention capacity (CRC) cannot be achieved. If the amount of azo initiator is too high, the process becomes too expensive.
  • CRC centrifuge retention capacity
  • a combination of at least one persulfate c1), a reducing component, and at least one azo initiator c2) is used as initiator c).
  • the amount of reducing component to be used is preferably from 0.0002 to 1% by weight, more preferably from 0.0001 to 0.8% by weight, more preferably from 0.0005 to 0.6% by weight, most preferably from 0.001 to 0.4% by weight, each based on monomer a).
  • the preferred polymerization inhibitors require dissolved oxygen. Therefore, the monomer solution can be freed of dissolved oxygen before the polymerization by inertization, i.e. flowing through with an inert gas, preferably nitrogen. It is also possible to reduce the concentration of dissolved oxygen by adding a reducing agent.
  • the oxygen content of the monomer solution is preferably lowered before the polymerization to less than 1 ppm by weight, more preferably to less than 0.5 ppm by weight.
  • the water content of the monomer solution is preferably less than 65% by weight, preferentially less than 62% by weight, more preferably less than 60% by weight, most preferably less than 58% by weight.
  • the monomer solution has, at 20° C., a dynamic viscosity of preferably from 0.002 to 0.02 Pas, more preferably from 0.004 to 0.015 Pas, most preferably from 0.005 to 0.01 Pas.
  • the mean droplet diameter in the droplet generation rises with rising dynamic viscosity.
  • the monomer solution has, at 20° C., a density of preferably from 1 to 1.3 g/cm 3 , more preferably from 1.05 to 1.25 g/cm 3 , most preferably from 1.1 to 1.2 g/cm 3 .
  • the monomer solution has, at 20° C., a surface tension of from 0.02 to 0.06 N/m, more preferably from 0.03 to 0.05 N/m, most preferably from 0.035 to 0.045 N/m.
  • the mean droplet diameter in the droplet generation rises with rising surface tension.
  • Additives for colour stability and additives for reducing residual monomers can also be added to the monomer solution.
  • the preferred amount of the additive for colour stability in the monomer solution is at least of 0.001%, preferably from 0.005% to 5% by weight, more preferably from 0.01 to 3% by weight, most preferably from 0.02 to 2% by weight, each based on monomer a).
  • the water-absorbent polymer particles are produced by polymerizing droplets of the monomer in a surrounding heated gas phase, for example using a system described in WO 2008/040715 A2, WO 2008/052971 A1, WO 2008/069639 A1 and WO 2008/086976 A1, or in a surrounding hydrophobic solvent, for example using a system described in WO 2008/068208 A1 and WO 2008/084031 A1.
  • the underside of the droplet plate has at least in part a contact angle preferably of at least 60°, more preferably at least 75° and most preferably at least 90° with regard to water.
  • the droplet plate may consist of a material having a lower contact angle with regard to water, for example a steel having the German construction material code number of 1.4571, and be coated with a material having a larger contact angle with regard to water.
  • the spacing of the bores is usually from 2 to 50 mm, preferably from 3 to 40 mm, more preferably from 4 to 30 mm, most preferably from 5 to 25 mm, preferentially 4 to 9 mm. Smaller spacings of the bores may cause agglomeration of the polymerizing droplets.
  • the diameter of the bores size area is 1900 to 22300 ⁇ m 2 , more preferably from 7800 to 20100 ⁇ m 2 , most preferably from 11300 to 17700 ⁇ m 2 .
  • Circular bores are preferred with a bore size from 50 to 170 ⁇ m, more preferably from 100 to 160 ⁇ m, most preferably from 120 to 150 ⁇ m.
  • droplet plates with different bore diameters can be used.
  • the variation can be done by different bores on one plate or by using different plates, where each plate has a different bore diameter.
  • the average particle size distribution can be monomodal, bimodal or multimodal. Most preferably it is monomodal or bimodal.
  • a carrier gas flows through the reaction zone.
  • the carrier gas may be conducted through the reaction zone in cocurrent to the free-falling droplets of the monomer solution, i.e. from the top downward.
  • the gas is preferably recycled at least partly, preferably to an extent of at least 50%, more preferably to an extent of at least 75%, into the reaction zone as cycle gas.
  • a portion of the carrier gas is discharged after each pass, preferably up to 10%, more preferably up to 3% and most preferably up to 1%.
  • the oxygen content of the carrier gas is preferably from 0.1 to 25% by volume, more preferably from 1 to 10% by volume, most preferably from 2 to 7% by weight.
  • a carrier gas which is free of oxygen it is also possible to use a carrier gas which is free of oxygen.
  • the carrier gas preferably comprises nitrogen.
  • the nitrogen content of the gas is preferably at least 80% by volume, more preferably at least 90% by volume, most preferably at least 95% by volume.
  • Other possible carrier gases may be selected from carbon dioxide, argon, xenon, krypton, neon, helium, sulfurhexafluoride. Any mixture of carrier gases may be used. It is also possible to use air as carrier gas.
  • the carrier gas may also become loaded with water and/or acrylic acid vapors.
  • the gas velocity is preferably adjusted such that the flow in the reaction zone ( 5 ) is directed, for example no convection currents opposed to the general flow direction are present, and is preferably from 0.1 to 2.5 m/s, more preferably from 0.3 to 1.5 m/s, even more preferably from 0.5 to 1.2 m/s, most preferably from 0.7 to 0.9 m/s.
  • the gas entrance temperature i.e. the temperature with which the gas enters the reaction zone, is preferably from 160 to 200° C., more preferably from 165 to 195° C., even more preferably from 170 to 190° C., most preferably from 175 to 185° C.
  • the gas entrance temperature is controlled in such a way that the gas exit temperature, i.e. the temperature with which the gas leaves the reaction zone, is less than 150° C., preferably from 90 to 140° C., more preferably from 100 to 130° C., even more preferably from 105 to 125° C., most preferably from 110 to 120° C.
  • the gas entrance temperature is from 175 to 185° C. and the temperature with which the gas leaves the reaction zone preferably from 110 to 120° C.
  • the water-absorbent polymer particles can be divided into three categories: water-absorbent polymer particles of Type 1 are particles with one cavity, water-absorbent polymer particles of Type 2 are particles with more than one cavity, and water-absorbent polymer particles of Type 3 are solid particles with no visible cavity.
  • the morphology of the water-absorbent polymer particles can be controlled by the reaction conditions during polymerization.
  • Water-absorbent polymer particles having a high amount of particles with one cavity (Type 1) can be prepared by using low gas velocities and high gas exit temperatures.
  • Water-absorbent polymer particles having a high amount of particles with more than one cavity (Type 2) can be prepared by using high gas velocities and low gas exit temperatures.
  • the reaction can be carried out under elevated pressure or under reduced pressure, preferably from 1 to 100 mbar below ambient pressure, more preferably from 1.5 to 50 mbar below ambient pressure, most preferably from 2 to 10 mbar below ambient pressure.
  • the reaction off-gas i.e. the gas leaving the reaction zone, may be cooled in a heat exchanger. This condenses water and unconverted monomer a).
  • the reaction off-gas can then be reheated at least partly and recycled into the reaction zone as cycle gas. A portion of the reaction off-gas can be discharged and replaced by fresh gas, in which case water and unconverted monomers a) present in the reaction off-gas can be removed and recycled.
  • thermally integrated system i.e. a portion of the waste heat in the cooling of the off-gas is used to heat the cycle gas.
  • the residual monomers can be removed during the thermal posttreatment. What is important here is that the water-absorbent polymer particles are not too dry. In the case of excessively dry particles, the residual monomers decrease only insignificantly. A too high water content increases the caking tendency of the water-absorbent polymer particles.
  • the kinetic energy of the polymer particles is greater than the cohesion or adhesion potential between the polymer particles.
  • the fluidized state can be achieved by a fluidized bed.
  • a fluidized bed In this bed, there is upward flow toward the water-absorbing polymer particles, so that the particles form a fluidized bed.
  • the height of the fluidized bed is adjusted by gas rate and gas velocity, i.e. via the pressure drop of the fluidized bed (kinetic energy of the gas).
  • the velocity of the gas stream in the fluidized bed is preferably from 0.3 to 2.5 m/s, more preferably from 0.4 to 2.0 m/s, most preferably from 0.5 to 1.5 m/s.
  • the moisture content of the water-absorbent polymer particles at the end of the thermal post-treatment is preferably from 1 to 20% by weight, more preferably from 2 to 15% by weight, even more preferably from 3 to 12% by weight, most preferably 6 to 9% by weight.
  • the average residence time in the internal fluidized bed is from 10 to 300 minutes, preferably from 60 to 270 minutes, more preferably from 40 to 250 minutes, most preferably from 120 to 240 minutes.
  • the thermal posttreatment is completely or at least partially done in an external fluidized bed.
  • the operating conditions of the external fluidized bed are within the scope for the internal fluidized bed as described above.
  • the level of residual monomers can be further reduced by an additional thermal posttreatment in a mixer with rotating mixing tools as described in WO 2011/117215 A1.
  • the morphology of the water-absorbent polymer particles can also be controlled by the reaction conditions during thermal posttreatment.
  • Water-absorbent polymer particles having a high amount of particles with one cavity (Type 1) can be prepared by using high product temperatures and short residence times.
  • Water-absorbent polymer particles having a high amount of particles with more than one cavity (Type 2) can be prepared by using low product temperatures and long residence times.
  • the polymer particles may subsequently be thermally surface post-crosslinked.
  • Surface-postcrosslinkers are compounds which comprise groups which can form at least two covalent bonds with the carboxylate groups of the polymer particles.
  • Suitable compounds are, for example, polyfunctional amines, polyfunctional amidoamines, polyfunctional epoxides, as described in EP 0 083 022 A2, EP 0 543 303 A1 and EP 0 937 736 A2, di- or polyfunctional alcohols as described in DE 33 14 019 A1, DE 35 23 617 A1 and EP 0 450 922 A2, or ⁇ -hydro-xyalkylamides, as described in DE 102 04 938 A1 and U.S. Pat. No. 6,239,230.
  • ethyleneoxide, aziridine, glycidol, oxetane and its derivatives may be used.
  • Polyvinylamine, polyamidoamines and polyvinylalcohole are examples of multifunctional polymeric surface-postcrosslinkers.
  • DE 40 20 780 C1 describes alkylene carbonates
  • DE 198 07 502 A1 describes 1,3-oxazolidin-2-one and its derivatives such as 2-hydroxyethyl-1,3-oxazolidin-2-one
  • DE 198 07 992 C1 describes bis- and poly-1,3-oxazolidin-2-ones
  • EP 0 999 238 A1 describes bis- and poly-1,3-oxazolidines
  • DE 198 54 573 A1 describes 2-oxotetrahydro-1,3-oxazine and its derivatives
  • DE 198 54 574 A1 describes N-acyl-1,3-oxazolidin-2-ones
  • DE 102 04 937 A1 describes cyclic ureas
  • DE 103 34 584 A1 describes bicyclic amide acetals
  • EP 1 199 327 A2 describes oxetanes and cyclic ureas
  • WO 2003/31482 A1 describes morpholine-2
  • the at least one surface-postcrosslinker is selected from alkylene carbonates, 1,3-oxazolidin-2-ones, bis- and poly-1,3-oxazolidin-2-ones, bis- and poly-1,3-oxazolidines, 2-oxotetrahydro-1,3-oxazines, N-acyl-1,3-oxazolidin-2-ones, N-hydroxyethyl-1,3-oxazolidin-2-ones, cyclic ureas, bicyclic amide acetals, oxetanes, and morpholine-2,3-diones.
  • At least one alkylene carbonate is used as surface-postcrosslinker.
  • Suitable alkylene carbonates are 1,3-dioxolan-2-on (ethylene carbonate), 4-methyl-1,3-dioxolan-2-on (propylene carbonate), 4,5-dimethyl-1,3-dioxolan-2-on, most preferably 1,3-dioxolan-2-on (ethylene carbonate).
  • a mixture of ethylene carbonate and diglycidyl ethers for example mono-, di- and polyethylene glycol diglycidyl ether, is used as surface-postcrossl inker.
  • the amount of surface-postcrosslinker is preferably from 0.01 to 10% by weight, more preferably from 0.5 to 7.5% by weight, most preferably from 1 to 5% by weight, based in each case on the polymer.
  • the content of residual monomers in the water-absorbent polymer particles prior to the coating with the surface-postcrosslinker is in the range from 0.03 to 15% by weight, preferably from 0.05 to 12% by weight, more preferably from 0.1 to 10% by weight, even more preferably from 0.15 to 7.5% by weight, most preferably from 0.2 to 5% by weight, even most preferably from 0.25 to 2.5% by weight.
  • the moisture content of the water-absorbent polymer particles prior to the thermal surface-postcrosslinking is preferably from 1 to 20% by weight, more preferably from 2 to 15% by weight, most preferably from 3 to 10% by weight.
  • polyvalent cations are applied to the particle surface in addition to the surface-postcrosslinkers before, during or after the thermal surface-postcrosslinking.
  • the polyvalent cations usable in the process according to the invention are, for example, trivalent cations such as the cations of aluminum, iron, chromium, rare earths and manganese, tetravalent cations such as the cations of titanium and zirconium, and mixtures thereof.
  • Possible counterions are chloride, bromide, sulfate, hydrogensulfate, carbonate, hydrogencarbonate, nitrate, hydroxide, phosphate, hydrogenphosphate, dihydrogenphosphate and carboxylate, such as acetate, glycolate, tartrate, formiate, propionate, 3-hydroxypropionate, lactamide and lactate, and mixtures thereof.
  • Aluminum sulfate, aluminum acetate, and aluminum lactate are preferred.
  • a single metal salt can be used as well as any mixture of the metal salts and/or the polyamines above.
  • Preferred polyvalent cations and corresponding anions are disclosed in WO 2012/045705 A1 and are expressly incorporated herein by reference.
  • Preferred polyvinylamines are disclosed in WO 2004/024816 A1 and are expressly incorporated herein by reference.
  • the amount of polyvalent cation used is, for example, from 0.001 to 1.5% by weight, preferably from 0.005 to 1% by weight, more preferably from 0.02 to 0.8% by weight, based in each case on the polymer.
  • polyvalent metal cation can take place prior, after, or cocurrently with the surface-postcrosslinking.
  • the formulation and operating conditions employed it is possible to obtain a homogeneous surface coating and distribution of the polyvalent cation or an inhomogenous typically spotty coating. Both types of coatings and any mixes between them are useful within the scope of the present invention.
  • the surface-postcrosslinking is typically performed in such a way that a solution of the surface-postcrosslinker is sprayed onto the hydrogel or the dry polymer particles. After the spraying, the polymer particles coated with the surface-postcrosslinker are dried thermally and cooled.
  • the spraying of a solution of the surface-postcrosslinker is preferably performed in mixers with moving mixing tools, such as screw mixers, disk mixers and paddle mixers.
  • Suitable mixers are, for example, vertical Schugi Flexomix® mixers (Hosokawa Micron BV; Doetinchem; the Netherlands), Turbolizers® mixers (Hosokawa Micron BV; Doetinchem; the Netherlands), horizontal Pflugschar® plowshare mixers (Gebr.
  • the solution of the surface-postcrosslinker can also be sprayed on the water-absorbent polymer particles during the thermal posttreatment.
  • the surface-postcrosslinker can be added as one portion or in several portions along the axis of thermal posttreatment mixer.
  • the surface-postcrosslinkers are typically used as an aqueous solution.
  • the addition of nonaqueous solvent can be used to adjust the penetration depth of the surface-postcrosslinker into the polymer particles.
  • the thermal surface-postcrosslinking is preferably carried out in contact dryers, more preferably paddle dryers, most preferably disk dryers.
  • Suitable driers are, for example, Hosokawa Bepex® horizontal paddle driers (Hosokawa Micron GmbH; Leingart; Germany), Hosokawa Bepex® disk driers (Hosokawa Micron GmbH; Leingart; Germany), Holo-Flite® dryers (Metso Minerals Industries Inc.; Danville; U.S.A.) and Nara paddle driers (NARA Machinery Europe; Frechen; Germany).
  • Nara paddle driers and, in the case of low process temperatures ( ⁇ 160° C.) for example, when using polyfunctional epoxides, Holo-Flite® dryers are preferred. Moreover, it is also possible to use fluidized bed dryers. In the latter case the reaction times may be shorter compared to other embodiments.
  • the angle can be fixed or may be adjustable and is typically between 0 to 10 degrees, preferably 1 to 6 degrees, most preferably 2 to 4 degrees.
  • a contact dryer is used that has two different heating zones in one apparatus.
  • Nara paddle driers are available with just one heated zone or alternatively with two heated zones.
  • the advantage of using a two or more heated zone dryer is that different phases of the thermal post-treatment and/or of the post-surface-crosslinking can be combined.
  • a contact dryer with a hot first heating zone is used which is followed by a temperature holding zone in the same dryer. This set up allows a quick rise of the product temperature and evaporation of surplus liquid in the first heating zone, whereas the rest of the dryer is just holding the product temperature stable to complete the reaction.
  • a contact dryer with a warm first heating zone is used which is then followed by a hot heating zone.
  • the thermal post-treatment is affected or completed whereas the surface-postcrosslinking takes place in the subsequential hot zone.
  • a paddle heater with just one temperature zone is employed.
  • the thermal surface-postcrosslinking can be effected in the mixer itself, by heating the jacket, blowing in warm air or steam.
  • a downstream dryer for example a shelf dryer, a rotary tube oven or a heatable screw. It is particularly advantageous to mix and dry in a fluidized bed dryer.
  • Preferred thermal surface-postcrosslinking temperatures are in the range from 100 to 180° C., preferably from 120 to 170° C., more preferably from 130 to 165° C., most preferably from 140 to 160° C.
  • the preferred residence time at this temperature in the reaction mixer or dryer is preferably at least 5 minutes, more preferably at least 20 minutes, most preferably at least 40 minutes, and typically at most 120 minutes.
  • the cooling is preferably carried out in contact coolers, more preferably paddle coolers, most preferably disk coolers.
  • Suitable coolers are, for example, Hosokawa Bepex® horizontal paddle coolers (Hosokawa Micron GmbH; Leingart; Germany), Hosokawa Bepex® disk coolers (Hosokawa Micron GmbH; Leingart; Germany), Holo-Flite® coolers (Metso Minerals Industries Inc.; Danville; U.S.A.) and Nara paddle coolers (NARA Machinery Europe; Frechen; Germany).
  • the polymer particles are cooled to temperatures of in the range from 20 to 150° C., preferably from 40 to 120° C., more preferably from 60 to 100° C., most preferably from 70 to 90° C. Cooling using warm water is preferred, especially when contact coolers are used.
  • the water-absorbent polymer particles can be coated and/or optionally moistened as e.g. described in WO2016124905.
  • the internal fluidized bed, the external fluidized bed and/or the external mixer used for the thermal posttreatment and/or a separate coater (mixer) can be used for coating of the water-absorbent polymer particles.
  • the cooler and/or a separate coater (mixer) can be used for coating/moistening of the surface-post-crosslinked water-absorbent polymer particles.
  • the water-absorbent polymer particles can further be selectively agglomerated. The agglomeration can take place after any process step after the polymerization,
  • the water-absorbent polymer particles can further be moistened with water and/or steam to improve the damage stability their tendency to static charging.
  • the moisture content is preferably at least 1% by weight, more preferably from 2 to 20% by weight, most preferably 5 to 12% by weight, based on the water-absorbent polymer particles.
  • Preferred coatings are aluminium dihydroxy monoacetate, aluminium sulfate, aluminium lactate, aluminium 3-hydroxypropionate, zirconium acetate, citric acid or its water soluble salts, di- and mono-phosphoric acid or their water soluble salts, Blancolen®, Bruggolite® FF7, Cublen®, Plantacare® 818 UP and Span® 20.
  • the drying gas is fed via a gas distributor ( 3 ) at the top of the spray dryer as shown in FIG. 6 .
  • the drying gas is partly recycled (drying gas loop) via a baghouse filter or cyclone unit ( 9 ) and a condenser column ( 12 ).
  • the pressure inside the spray dryer is below ambient pressure.
  • the spray dryer outlet temperature is preferably measured at three points around the circumference at the end of the cylindrical part as shown in FIG. 7 .
  • the single measurements ( 43 ) are used to calculate the average cylindrical spray dryer outlet temperature.
  • a monomer separator unit ( 38 ) is used for recycling of the monomers from the condenser column ( 12 ) into the monomer feed ( 35 ).
  • This monomer separator unit is for example especially a combination of micro-, ultra-, nanofiltration and osmose membrane units, to separate the monomer from water and polymer particles.
  • Suitable membrane separator systems are described, for example, in the monograph “Membranen: Klan, Aid und Industrielle füren”, K. Ohlrogge and K. Ebert, Wiley-VCH, 2012 (ISBN: 978-3-527-66033-9).
  • Conditioned internal fluidized bed gas is fed to the internal fluidized bed ( 27 ) via line ( 25 ).
  • the gas preferably having a temperature of 105° C., more preferably of 106° C.
  • the relative humidity of the internal fluidized bed gas is preferably controlled by the temperature in the condensor column ( 12 ) and using the Mollier diagram.
  • the spray dryer offgas is filtered in a dust separation unit ( 9 ) and sent to a condenser column ( 12 ) for quenching/cooling.
  • a recuperation heat exchanger system for preheating the gas after the condenser column ( 12 ) can be used.
  • the dust separation unit ( 9 ) may be heat-traced on a temperature of preferably from 80 to 180° C., more preferably from 90 to 150° C., most preferably from 100 to 140° C.
  • Example for the dust separation unit are baghouse filter, membranes, cyclones, dust compactors and for examples described, for example, in the monographs “Staubabscheiden”, F. Löffler, Georg Thieme Verlag, Stuttgart, 1988 (ISBN 978-3137122012) and “Staubabschreibung mit Schlauchfiltern und Taschenfiltern”, F. Löffler, H. Dietrich and W. Flatt, Vieweg, Braunschweig, 1991 (ISBN 978-3540670629).
  • cyclones for example, cyclones/centrifugal separators of the types ZSA/ZSB/ZSC from LTG Aktiengesellschaft and cyclone separators from Ventilatorenfabrik Oelde GmbH, Camfil Farr International and MikroPul GmbH.
  • Excess water is pumped out of the condenser column ( 12 ) by controlling the (constant) filling level in the condenser column ( 12 ).
  • the water in the condenser column ( 12 ) is pumped counter-current to the gas via quench nozzles ( 11 ) and cooled by a heat exchanger ( 13 ) so that the temperature in the condenser column ( 12 ) is preferably from 40 to 71° C., more preferably from 46 to 69° C., most preferably from 49 to 65° C. and more even preferably from 51 to 60° C.
  • the water in the condenser column ( 12 ) is set to an alkaline pH by dosing a neutralizing agent to wash out vapors of monomer a).
  • Aqueous solution from the condenser column ( 12 ) can be sent back for preparation of the monomer solution.
  • the condenser column offgas may be split to the gas drying unit ( 37 ) and the conditioned internal fluidized bed gas ( 27 ).
  • gas drying unit can be used, for example, an air gas cooling system in combination with a gas mist eliminators or droplet separator (demister), for examples, droplet vane type separator for horizontal flow (e.g. type DH 5000 from Munters AB, Sweden) or vertical flow (e.g. type DV 270 from Munters AB, Sweden).
  • Vane type demisters remove liquid droplets from continuous gas flows by inertial impaction.
  • any gas/gas or gas/liquid heat exchanger can be used. Preferred are sealed plate heat exchangers.
  • the water, which is condensed in the gas drying unit ( 37 ) can be partially used as wash water for the condenser column ( 12 ) or disposed.
  • the gas temperatures are controlled via heat exchangers ( 20 ) and ( 22 ).
  • the hot drying gas is fed to the cocurrent spray dryer via gas distributor ( 3 ).
  • the gas distributor ( 3 ) consists preferably of a set of plates providing a pressure drop of preferably 1 to 100 mbar, more preferably 2 to 30 mbar, most preferably 4 to 20 mbar, depending on the drying gas amount. Turbulences and/or a centrifugal velocity can also be introduced into the drying gas if desired by using gas nozzles or baffle plates.
  • Conditioned internal fluidized bed gas is fed to the internal fluidized bed ( 27 ) via line ( 25 ).
  • the steam content of the fluidized bed gas can be controlled by the temperature in the condenser column ( 12 ).
  • the product holdup in the internal fluidized bed ( 27 ) can be controlled via rotational speed of the rotary valve ( 28 ).
  • the amount of gas in the internal fluidized bed ( 27 ) is selected so that the particles move free and turbulent in the internal fluidized bed ( 27 ).
  • the product height in the internal fluidized bed ( 27 ) is with gas preferably at least 10%, more preferably at least 20%, more preferably at least 30%, even more preferably at least 40% higher than without gas.
  • the product is discharged from the internal fluidized bed ( 27 ) via rotary valve ( 28 ).
  • the product holdup in the internal fluidized bed ( 27 ) can be controlled via rotational speed of the rotary valve ( 28 ).
  • the sieve ( 29 ) is used for sieving off overs/lumps.
  • the monomer solution is preferably prepared by mixing first monomer a) with a neutralization agent and secondly with crosslinker b).
  • the temperature during neutralization is controlled to preferably from 5 to 60° C., more preferably from 8 to 40° C., most preferably from 10 to 30° C., by using a heat exchanger and pumping in a loop.
  • a filter unit is preferably used in the loop after the pump.
  • the initiators are metered into the monomer solution upstream of the dropletizer by means of static mixers ( 31 ) and ( 32 ) via lines ( 33 ) and ( 34 ) as shown in FIG. 6 .
  • Each initiator is preferably pumped in a loop and dosed via control valves to each dropletizer unit.
  • a second filter unit is preferably used after the static mixer ( 32 ).
  • the mean residence time of the monomer solution admixed with the full initiator package in the piping before dropletization is preferably less than 60 s, more preferably less than 30 s, most preferably less than 10 s.
  • preferably three dropletizer units are used as shown in FIG. 4 of WO 2016/134905 A1.
  • any number of dropletizers can be used that is required to optimize the throughput of the process and the quality of the product.
  • at least one dropletizer is employed, and as many dropletizers as geometrically allowed may be used.
  • a dropletizer unit consists of an outer pipe ( 47 ) having an opening for the dropletizer cassette ( 49 ) as shown in FIG. 7 of WO2016/134905A1.
  • the dropletizer cassette ( 49 ) is connected with an inner pipe ( 48 ).
  • the inner pipe ( 48 ) having a PTFE block ( 50 ) at the end as sealing can be pushed in and out of the outer pipe ( 51 ) during operation of the process for maintenance purposes.
  • the temperature of the dropletizer cassette ( 57 ) is controlled to preferably 5 to 80° C., more preferably 10 to 70° C., most preferably 30 to 60° C., by water in flow channels ( 55 ) as shown in FIG. 8 of WO2016/134905A1.
  • the dropletizer cassette has preferably from 10 to 2000 bores, more preferably from 50 to 1500 bores, most preferably from 100 to 1000 bores.
  • the diameter of the bores size area is 1900 to 22300 ⁇ 2 , more preferably from 7800 to 20100 ⁇ m 2 , most preferably from 11300 to 17700 ⁇ m 2 .
  • the bores can be of circular, rectangular, triangular or any other shape. Circular bores are preferred with a bore size from 50 to 170 ⁇ m, more preferably from 100 to 160 ⁇ m, most preferably from 120 to 150 ⁇ m.
  • the ratio of bore length to bore diameter is preferably from 0.5 to 10, more preferably from 0.8 to 5, most preferably from 1 to 3.
  • the droplet plate ( 53 ) can have a greater thickness than the bore length when using an inlet bore channel.
  • the droplet plate ( 53 ) is preferably long and narrow as disclosed in WO 2008/086976 A1. Multiple rows of bores per droplet plate can be used, preferably from 1 to 20 rows, more preferably from 2 to 5 rows.
  • the dropletizer cassette ( 57 ) consists of a flow channel ( 56 ) having essential no stagnant volume for homogeneous distribution of the premixed monomer and initiator solutions and two droplet plates ( 53 ).
  • the droplet plates ( 53 ) have an angled configuration with an angle of preferably from 1 to 90°, more preferably from 3 to 45°, most preferably from 5 to 20°.
  • Each droplet plate ( 53 ) is preferably made of a heat and/or chemically resistant material, such as stainless steel, polyether ether ketone, polycarbonate, polyarylsulfone, such as polysulfone, or polyphenylsulfone, or fluorous polymers, such as perfluoroalkoxyethylene, polytetrafluoroethylene, polyvinylidenfluorid, ethylene-chlorotrifluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers and fluorinated polyethylene.
  • Coated droplet plates as disclosed in WO 2007/031441 A1 can also be used.
  • the choice of material for the droplet plate is not limited except that droplet formation must work and it is preferable to use materials which do not catalyze the start of polymerization on its surface.
  • the arrangement of dropletizer cassettes is preferably rotationally symmetric or evenly distributed in the spray dryer (for example see FIGS. 4 to 5 of WO 2016/134905 A1).
  • the throughput of monomer including initiator solutions per dropletizer unit is preferably from 10 to 4000 kg/h, more preferably from 100 to 1000 kg/h, most preferably from 200 to 600 kg/h.
  • the throughput per bore is preferably from 0.1 to 10 kg/h, more preferably from 0.5 to 5 kg/h, most preferably from 0.7 to 2 kg/h.
  • the present invention provides water-absorbent polymer particles H.
  • the water-absorbent polymer particles H having a CRC of 38 g/g to 85 g/g, preferably of 40 g/g to 80 g/g, more preferably of 42 g/g to 75 g/g.
  • the water-absorbent polymer particles H having a vortex of 40 s or less, preferably of 35 s or less, more preferably of 30 s or less.
  • the water-absorbent polymer particles H having a vortex of 5 to 40 s, preferably of 8 to 35 s.
  • the water-absorbent polymer particles H having an AUL (21 g cm ⁇ 2 ) of 22 g/g to 60 g/g, preferably of 25 g/g to 60 g/g, more preferably of 27 g/g to 58 g/g, most preferably of at least 28 g/g to 55 g/g
  • the water-absorbent polymer particles H within the absorbent core ( 80 ) having a VAUL (i 21 g cm ⁇ 2 ) of 1000 s or less, preferable of 700 s or less, more preferable of 500 s or less.
  • the fluid absorbent core ( 80 ) comprising water-absorbent polymer particles H having a T 20 of 1000 s or less, preferably of 900 s or less, more preferable of 800 s or less, most preferable of 700 s or less.
  • the inventive fluid absorbent core ( 80 ) comprising water-absorbent polymer particles H having a FSC (1 min) of at least 25 g/g/s, preferably at least 27 g/g/s, more preferably at least 28 g/g/s, most preferably at least 30 g/g/s.
  • the water-absorbent polymer particles H having a roundness from 0.79 to 0.85, preferably from 0.80 to 0.85, more preferably from 0.80 to 0.84 most preferably from 0.80 to 0.83.
  • the roundness is the volume-average roundness.
  • the water-absorbent polymer particles H are surface-crosslinked.
  • the water-absorbent polymer particles H particularly suitable for a fluid absorbent core ( 80 ) according to any of claims 1 to 12 .
  • An absorbent core ( 80 ) comprises at least one preferably at least two layers of water-absorbent polymer particles.
  • a first water-absorbent polymer or a blend of water absorbent polymers ( 91 ) is dropped onto one side of a nonwoven material ( 94 ).
  • An adhesive ( 93 ) is applied to the upper layer (top tissue layer) ( 95 ).
  • the tissue layer ( 95 ) is laminated with the side of the nonwoven ( 94 ) carrying the water-absorbent polymer ( 91 ).
  • a second water-absorbent polymer ( 92 ) is dropped onto the other side of the nonwoven ( 94 ).
  • An adhesive ( 93 ) is applied to the bottom layer (lower tissue layer) ( 96 ).
  • the tissue layer ( 96 ) is laminated with the side of the nonwoven ( 94 ) carrying the water-absorbent polymer ( 92 ).
  • FIG. 4 illustrates an absorbent core according to the invention.
  • the core may optionally provided with a cover ( 86 ) (e.g. tissue wrap).
  • This cover ( 86 ) may be at the top and/or at the bottom of the fluid-absorbent core ( 80 ) with bonding at lateral juncture and/or bonding at the distal juncture by hot-melt, ultrasonic bonding, thermal bonding or combination of bonding techniques know to persons skilled in the art. Further, this cover ( 86 ) may include the whole fluid-absorbent core with a unitary sheet of material and thus function as a wrap. Wrapping is possible as a full wrap, a partial wrap or as a C-Wrap.
  • FIG. 4 A schematic view of one embodiment of the inventive absorbent core ( 80 ) is shown in FIG. 4 .
  • the material of the core cover ( 86 ) may comprise any known type of substrate, including nonwovens, webs, garments, textiles, films, tissues and laminates of two or more substrates or webs.
  • the core cover material may comprise natural fibers, such as cellulose, cotton, flax, linen, hemp, wool, silk, fur, hair and naturally occurring mineral fibers.
  • the core cover material may also comprise synthetic fibers such as rayon and lyocell (derived from cellulose), polysaccharides (starch), polyolefin fibers (polypropylene, polyethylene), polyamides, polyester, butadienestyrene block copolymers, polyurethane and combinations there-of.
  • the core cover ( 86 ) comprises synthetic fibers or tissue.
  • the fibers may be mono- or multicomponent.
  • Multicomponent fibers may comprise a homo-polymer, a copolymer or blends thereof.
  • the absorbent core ( 80 ) comprises at least two thin and flexible single layers ( 91 , 92 ) of suitable absorbent material.
  • Each of these layers is macroscopically two-dimensional and planar and of very low thickness compared to the other dimensions.
  • Said layer may incorporate superabsorbent material throughout the layer.
  • the layers may have different concentrations and different water-absorbent polymer material showing concentrations in the range from about 90 to 100% by weight, preferably 95 to 100% by weight, more preferably 98 to 100% by weight.
  • the layers ( 91 , 92 ) are preferably joined to the upper and/or bottom layer ( 95 , 96 ) respectively e.g. by addition of adhesives ( 93 ) or by mechanical, thermal or ultrasonic bonding or combinations thereof, whereas adhesives are preferred.
  • At least one of the layers ( 91 ) and/or ( 92 ) containing a blend of at least two kinds of water-absorbent polymer particles is not limited.
  • the water-absorbent polymer particles are placed within the core ( 80 ), especially within each layer ( 91 , 92 ) in discrete regions, chambers or pockets, e.g. supported by at least an adhesive.
  • Techniques of application of the water-absorbent polymer materials into the absorbent core especially in the respective layers ( 91 , 92 ) are known to persons skilled in the art and may be volumetric, loss-in-weight or gravimetric. Known techniques include the application by vibrating systems, single and multiple auger systems, dosing roll, weigh belt, fluid bed volumetric systems and gravitational sprinkle and/or spray systems. Further techniques of insertion are falling dosage systems consensus and contradictory pneumatic application or vacuum printing method of applying the fluid absorbent polymer materials.
  • the quantity of water-absorbent polymer particles within the fluid-absorbent core ( 80 ) is from 100 to 500 gsm, preferably 200 to 400 gsm, more preferably 250 to 300 gsm in case of maxi diapers (size L), wherein each layer contains at least 50 gsm water absorbent polymer particles preferably at least 100 gsm water absorbent polymer particles
  • the absorbent core ( 80 ) may comprise also at least one layer of other material such as short-fiber air-laid nonwoven materials ( 94 ); nonwoven materials such as polyethylene, polypropylene, nylon, polyester, and the like; cellulosic fibrous materials such as paper tissue or towels known in the art, wax-coated papers, corrugated paper materials, and the like; or fluff pulp. Said layer may further incorporate bi-component binding fibers.
  • the nonwoven ( 94 ) within in the absorbent core ( 80 ) is typically a single layer, e.g. made by air-thru bonded process. Its total basis weight is around 10 to 100 gsm, preferably 40 to 60.
  • the absorbent core ( 80 ) additionally may comprise at least two tissue layers ( 95 , 96 ).
  • the tissue layers are not restricted to tissue material such as paper it also refers to nonwovens.
  • the material of the layers ( 95 , 96 ) may comprise any known type of substrate, including webs, garments, textiles and films.
  • the tissue layers ( 95 , 96 ) may comprise natural fibers, such as cellulose, cotton, flax, linen, hemp, wool, silk, fur, hair and naturally occurring mineral fibers.
  • the tissue layer ( 95 , 96 ) may also comprise synthetic fibers such as rayon and lyocell (de-rived from cellulose), polysaccharides (starch), polyolefin fibers (polypropylene, polyethylene), polyamides, polyester, butadiene-styrene block copolymers, polyurethane and combinations thereof.
  • the tissue layer comprises cellulose fibers. It is preferred that the tissue layer is made from ca. 50% wood pulp and 50% chemical viscose fibers at >45 gsm to provide tensile strength and integrity.
  • the upper and lower tissue layers ( 95 , 96 ) each total basis weight is from 10 to 100 gsm, preferably 30 to 80 gsm.
  • the fluid-absorbent core ( 80 ) comprises not more than 20% by weight of an adhesive, preferably not more than 10% by weight of an adhesive, more preferably not more than 5% by weight.
  • the adhesive is a hotmelt adhesive.
  • the absorbent core ( 80 ) respectively has a total basis weight ranging from about 150 gsm to about 2000 gsm, preferably from about 300 gsm to about 750 gsm, and more preferably from about 500 gsm to about 650 gsm.
  • the fluid absorbent core ( 80 ) comprising at least one absorption layer, the layer comprising at least 80% by weight of water-absorbent polymer particles, preferably at least 90% by weight, more preferably at least 95% by weight, most preferably at least 98% by weight of water-absorbent polymer particles; 0 to 10% by weight of an adhesive, preferably 0 to 5% by weight of an adhesive and from 0 to 10% by weight, preferably 0 to 5% by weight, more preferably 0 to 2% by weight of fibrous material, wherein the water-absorbent polymer particles within the absorption layer are water-absorbent polymer particles H having a vortex of 40 s or less and having a roundness of 0.79 to 0.85 and/or a CRC of 38 g/g to 85 g/g.
  • the fluid-absorbent core ( 80 ) comprises at least two absorption layers, an upper layer ( 91 ) and a bottom layer ( 92 ), wherein at least the bottom layer ( 92 ) comprises water-absorbent polymer particles H having a vortex of 40 s or less and having a roundness of 0.79 to 0.85 and/or a CRC of 38 g/g to 85 g/g.
  • Each of the layers upper layer ( 91 ) and bottom (lower) layer ( 92 ) comprising at least 80% by weight of water-absorbent polymer particles, preferably at least 90% by weight, more preferably at least 95% by weight, most preferably at least 98% by weight of water-absorbent polymer particles; 0 to 10% by weight of an adhesive, preferably 0 to 5% by weight of an adhesive and from 0 to 10% by weight, preferably 0 to 5% by weight, more preferably 0 to 2% by weight of fibrous material.
  • the water-absorbent polymer particles H having a CRC of 38 g/g to 85 g/g, preferably of 40 g/g to 80 g/g, more preferably of 42 g/g to 75 g/g.
  • the water-absorbent polymer particles H having a vortex of 40 s or less, preferably of 35 s or less, more preferably of 30 s or less.
  • the water-absorbent polymer particles H having a vortex of 5 to 40 s, preferably of 8 to 35 s.
  • the water-absorbent polymer particles H having an AUL (21 g cm ⁇ 2 ) of 22 g/g to 60 g/g, preferably of at least 25 g/g to 60 g/g, more preferably of 27 g/g to 58 g/g, most preferably of at least 28 g/g to 55 g/g.
  • the water-absorbent polymer particles H within the absorbent core ( 80 ) having a VAUL (i 21 g cm ⁇ 2 ) of 1000 s or less, preferable of 700 s or less, more preferable of 500 s or less.
  • the fluid absorbent core ( 80 ) comprising water-absorbent polymer particles H having a T 20 of 1000 s or less, preferably of 900 s or less, more preferable of 800 s or less, most preferable of 700 s or less.
  • the inventive fluid absorbent core ( 80 ) comprising water-absorbent polymer particles H having a FSC (1 min) of at least 25 g/g/s, preferable at least 27 g/g/s, more preferable at least 28 g/g/s, most preferably at least 30 g/g/s.
  • the inventive fluid absorbent core ( 80 ) comprising water-absorbent polymer particles H having a roundness from 0.79 to 0.85, preferably from 0.80 to 0.85, more preferably from 0.80 to 0.84 most preferably from 0.80 to 0.83.
  • the roundness is the volume-average roundness.
  • the water-absorbent polymer particles H are surface-crosslinked.
  • One preferred fluid-absorbent core ( 80 ) comprises within the lower layer ( 92 ) water-absorbent polymer particles H with a CRC of 38 g/g to 85 g/g and a vortex of 40 s or less, preferably with a CRC of 40 g/g to 80 g/g and a vortex of 35 s or less, more preferably with a CRC of 42 g/g to 75 g/g and a vortex of 35 s or less.
  • a fluid-absorbent core ( 80 ) comprising within the lower layer ( 92 ) water-absorbent polymer particles H with a vortex of 40 s or less and a roundness from 0.79 to 0.85, preferably with a vortex of 35 s or less and a roundness from 0.80 to 0.85, more preferably with a vortex of 35 s or less and a roundness from 0.80 to 0.84.
  • Another preferred fluid-absorbent core ( 80 ) comprises within the lower layer ( 92 ) water-absorbent polymer particles H with a CRC of 38 g/g to 85 g/g and a vortex of 40 s or less and a roundness from 0.79 to 0.85, preferably with a CRC of 40 g/g to 80 g/g and a vortex of 35 s or less and a roundness from 0.80 to 0.85, more preferably with a CRC of 42 g/g to 75 g/g and a vortex of 35 s or less and a roundness from 0.80 to 0.84.
  • Vortex and CRC could be e.g. adapted by modifying crosslink density or particle size distribution of the water-absorbent polymer particles.
  • the Water Pouring Time of the inventive the flu-id absorbent core ( 80 ) is 28 s or less, preferably 26 s, more preferably 25 s or less and the Water Pouring Rewet the fluid absorbent core ( 80 ) is 3.5 g or less, preferably 3.3 or less, measured according to the method “Water pouring test” disclosed herein.
  • the inventive absorbent core absorbs a fluid very fast (Water Pouring Time) coupled with a low rewet. This means the absorbed fluid is quickly absorbed and hold within the core even under pressure.
  • the fluid absorbent core ( 80 ) having a Liquid Diffusion Length of at least 245 mm, preferably at least 250 mm, more preferably above 260 mm, most preferably above 270 mm, a total strike-thru time of 50 s or less, preferably of 48 s or less, more preferably of 45 s or less and a Total Rewet of 40 g or less, preferably of 35 g or less, more preferably of 30 g or less measured according to the method “Strike-thru/Rewet” disclosed in the description.
  • the Liquid Diffusion Length of at least 245 mm shows that the fluid within the inventive absorbent core is distributed throughout the core.
  • the fluid does not stick in only a small part of the core. So the whole core area is used and gel blocking is prevented.
  • the fluid-absorbent core ( 80 ) typically has a uniform size or profile. Suitable fluid-absorbent cores can also have profiled structures, concerning the shape of the core and/or the content of water-absorbent polymer particles and/or the distribution of the water-absorbent polymer particles and/or the dimensions of the different layers if a layered fluid-absorbent core is present.
  • the shape of the core in view from above can be rectangular, anatomical shaped with a narrower crotch area or any other shapes.
  • the top view area of the fluid-absorbent core ( 80 ) is preferably at least 200 cm 2 , more preferably at least 250 cm 2 , most preferably at least 300 cm 2 .
  • the top view area is the part of the core that is face-to-face to the upper liquid-pervious layer.
  • the fluid-absorbent core may comprise additional additives typically present in fluid absorbent articles known in the art.
  • Exemplary additives are fibers for reinforcing and stabilizing the fluid-absorbent core.
  • Preferably polyethylene is used for reinforcing the fluid-absorbent core.
  • Further suitable stabilizer for reinforcing the fluid-absorbent core are materials acting as binder.
  • binder material e.g. the lower melting one in the central region of the core, and the higher melting in the distal regions.
  • Suitable binder materials may be adhesive or non-adhesive fibers, continuously or discontinuously extruded fibers, bi-component staple fibers, non-elastomeric fibers and sprayed liquid binder or any combination of these binder materials.
  • thermoplastic compositions usually are added to increase the integrity of the core layer.
  • Thermoplastic compositions may comprise a single type of thermoplastic polymers or a blend of thermoplastic polymers.
  • the thermoplastic composition may comprise hot melt adhesives comprising at least one thermoplastic polymer together with thermoplastic diluents such as tackifiers, plasticizers or other additives, e.g. antioxidants.
  • the thermoplastic composition may further comprise pressure sensitive hot melt adhesives comprising e.g. crystalline polypropylene and an amorphous polyalphaolefin or styrene block copolymer and mixture of waxes.
  • Suitable odor control additives are all substances of reducing odor developed in carrying fluid-absorbent articles over time known in the art.
  • suitable odor control additives are inorganic materials, such as zeolites, activated carbon, bentonite, silica, aerosile, kieselguhr, clay; chelants such as ethylenediamine tetraacetic acid (EDTA), cyclodextrins, aminopolycarbonic acids, ethylenediamine tetramethylene phosphonic acid, aminophosphate, polyfunctional aromates, N,N-disuccinic acid.
  • Suitable odor control additives are further antimi-crobial agents.
  • Suitable odor control additives are further compounds with anhydride groups such as maleic-, itaconic-, polymaleic- or polyitaconic anhydride, copolymers of maleic acid with C2-C8 olefins or styrene, polymaleic anhydride or copolymers of maleic anhydride with isobutene, di-isobutene or styrene, compounds with acid groups such as ascorbic, benzoic, citric, salicylic or sorbic acid and fluid-soluble polymers of monomers with acid groups, homo- or co-polymers of C3-C5 mono-unsaturated carboxylic acids.
  • anhydride groups such as maleic-, itaconic-, polymaleic- or polyitaconic anhydride, copolymers of maleic acid with C2-C8 olefins or styrene, polymaleic anhydride or copolymers of maleic anhydride with isobutene, di
  • Suitable wetness indication additives comprising a mixture of sorbitan monooleate and polyethoxylated hydrogenated castor oil.
  • the amount of the wetness indication additive is in the range of about 0.0001 to 2% by weight related to the weight of the fluid-absorbent core.
  • an absorbent core ( 80 ) comprises top ( 91 ) and bottom ( 92 ) layers of water-absorbing polymer particles containing each 100 to 200 per square meter (g/m 2 or gsm), preferably 120 to 160 gsm, most preferably 130 to 150 gsm
  • Both layers are glued ( 93 ) with 1 to 0.2 gsm, preferably 0.7 to 0.3 gsm, more preferably 0.6 to 0.4 gsm hot melt adhesive on 100 to 30 gsm, preferably 80 to 40 gsm, more preferably 45 to 60 gsm air-thru-bond nonwoven material ( 94 ) and are then sandwiched with two layers of 70 to 20 gsm, preferably 60 to 30 gsm, more preferably 40 to 50 gsm condensed tissue layers on the top ( 95 ) and bottom ( 96 ) using hot-melt glue applied to the surface at 2.4 to 1.0 gsm, preferably 2.3 to 1.5 gsm,
  • Adhesive (preferably hot melt adhesive) is sprayed on to tissue ( 1 ) (e. g. condensed tissue).
  • tissue ( 1 ) e. g. condensed tissue.
  • Superabsorbent SAP ( 3 ) or ( 4 ) or both is applied on to high loft nonwoven material ATB ( 7 ) (e. g. air-through bond nonwoven of polyester) using roller feeder (commercially available SAP feeder roller type).
  • the nonwoven containing SAP is then laminated with the tissue layer ( 1 ) on which the adhesive was applied, at position ( 10 ).
  • Adhesive ( 8 ) (preferably hot melt adhesive) is sprayed on to tissue ( 9 ).
  • Superabsorbent SAP ( 5 ) or ( 6 ) or both is applied on to the other side of the high loft nonwoven material ATB ( 7 ).
  • the nonwoven containing SAP is then laminated with the tissue layer ( 9 ) on which the adhesive was applied, at position ( 15 ).
  • a preferred absorbent core ( 80 ) comprises top ( 91 ) and bottom ( 92 ) layers of water-absorbing polymer particles containing each 130 grams per square meter (g/m 2 or gsm) with a 50 g/m 2 air-thru-bond nonwoven material ( 94 ) in between the two layers ( 91 ) and ( 92 ). Both layers are then sandwiched with two layers of 45 g/m 2 condensed tissue layers on the top ( 95 ) and bottom ( 96 ) using hot-melt glue ( 93 ) applied to the surface at 2.5 g/m 2 . Total hot-melt glue used is 2.5 g/m 2 each for both top and bottom layers. The numbers refer to FIG. 4 .
  • the density of the fluid-absorbent core is in the range of 0.1 to 0.25 g/cm 3 , preferably 0.1 to 0.28 g/cm 3 .
  • the thickness of the fluid-absorbent core is in the case of diapers in the range of 1 to 8 mm, preferably 1 to 5 mm, more preferably 1.5 to 3 mm, in the case of adult-incontinence products in the range of 3 to 15 mm.
  • the inventive fluid-absorbent core is part of a fluid-absorbent article.
  • a fluid-absorbent article comprises
  • the fluid-absorbent core ( 80 ) is disposed between the upper liquid-pervious sheet ( 89 ) and the lower liquid-impervious sheet ( 83 ).
  • Fluid-absorbent articles are understood to mean, for example, incontinence pads and incontinence briefs for adults or diapers and training pants for babies.
  • Suitable fluid-absorbent articles including fluid-absorbent compositions comprising fibrous materials and optionally water-absorbent polymer particles to form fibrous webs or matrices for the substrates, layers, sheets and/or the fluid-absorbent core.
  • Suitable fluid-absorbent articles are composed of several layers whose individual elements must show preferably definite functional parameter such as dryness for the upper liquid-pervious layer ( 89 ), vapor permeability without wetting through for the lower liquid-impervious layer ( 83 ), a flexible, vapor permeable and thin fluid-absorbent core ( 80 ), showing fast absorption rates and being able to retain highest quantities of body fluids, and an optional acquisition-distribution layer ( 70 ) between the upper layer ( 89 ) and the core ( 80 ), acting as transport and distribution layer of the discharged body fluids.
  • a functional parameter such as dryness for the upper liquid-pervious layer ( 89 ), vapor permeability without wetting through for the lower liquid-impervious layer ( 83 ), a flexible, vapor permeable and thin fluid-absorbent core ( 80 ), showing fast absorption rates and being able to retain highest quantities of body fluids, and an optional acquisition-distribution layer ( 70 ) between the upper layer
  • the resultant fluid-absorbent article meets overall criteria such as flexibility, water vapor breath-ability, dryness, wearing comfort and protection on the user facing side, and concerning liquid retention, rewet and prevention of wet through on the garment side.
  • the specific combination of these layers provides a fluid-absorbent article delivering both high protection levels as well as high comfort to the consumer.
  • FIG. 5 is a schematic view of a fluid absorbent article according to the invention:
  • the fluid-absorbent article comprises an absorbent core ( 80 ) comprising at least two layers of water-absorbent polymer particles, top ( 91 ), bottom ( 92 ) optionally sandwiched by at least two tissue layers, top ( 95 ) and bottom ( 96 ) and at least one nonwoven ( 94 ) (e.g. high loft air thru bond nonwoven) sandwiched by the at least two layers of water-absorbent polymer particles ( 91 , 92 ).
  • the layers optionally be connected to each other ( 93 ), e. g. by adhesive, ultrasonic bonding or any other suitable method.
  • the total core structure ( 80 ) is optionally sur-rounded/wrapped by a further nonwoven sheet or tissue layer ( 86 ), the so called core wrap, also optionally connected by an adhesive to the sandwich structured absorbent core ( 80 ).
  • the absorbent article comprises an acquisition distribution layer ( 70 ) on top of the core ( 80 ) or core wrap ( 86 ) respectively below the upper liquid-pervious sheet ( 89 ) (e. g. embossed spunbond nonwoven), and a lower liquid-impervious sheet ( 83 ).
  • the upper liquid-pervious sheet ( 89 ) e. g. embossed spunbond nonwoven
  • a lower liquid-impervious sheet 83
  • Leg cuffs ( 81 ) and some elastics ( 88 ) may be also present.
  • the liquid-pervious sheet ( 89 ) is the layer which is in direct contact with the skin.
  • the liq-uid-pervious sheet ( 89 ) is preferably compliant, soft feeling and non-irritating to the consumer's skin.
  • the term “liquid-pervious” is understood thus permitting liquids, i.e. body fluids such as urine, menses and/or vaginal fluids to readily penetrate through its thick-ness.
  • the principle function of the liquid-pervious sheet ( 89 ) is the acquisition and transport of body fluids from the wearer towards the fluid-absorbent core.
  • liquid pervious layers ( 89 ) are formed from any materials known in the art such as nonwoven material, films or combinations thereof.
  • Suitable liquid-pervious sheets consist of customary synthetic or semisynthetic fibers or bi-component fibers or films of polyester, polyolefins, rayon or natural fibers or any combinations thereof. In the case of nonwoven materials, the fibers should generally be bound by binders such as polyacrylates. Additionally, the liquid-pervious sheet may contain elastic compositions thus showing elastic characteristics allowing to be stretched in one or two directions.
  • Suitable synthetic fibers are made from polyvinyl chloride, polyvinyl fluoride, polytetrafluorethylene, polyvinylidene chloride, polyacrylics, polyvinyl acetate, polyethylvinyl acetate, non-soluble or soluble polyvinyl alcohol, polyolefins such as polyethylene, polypropylene, polyamides, poly-esters, polyurethanes, polystyrenes and the like
  • films are apertured formed thermoplastic films, apertured plastic films, hydro-formed thermoplastic films, reticulated thermoplastic films, porous foams, reticulated foams, and thermoplastic scrims.
  • suitable modified or unmodified natural fibers include cotton, bagasse, kemp, flax, silk, wool, wood pulp, chemically modified wood pulp, jute, rayon, ethyl cellulose, and cellulose acetate.
  • the fibrous material may comprise only natural fibers or synthetic fibers or any combination thereof. Preferred materials are polyester, rayon and blends thereof, polyethylene, and polypropylene.
  • the fibrous material as a component of the fluid-absorbent compositions may be hydrophilic, hydrophobic or can be a combination of both hydrophilic and hydrophobic fibers.
  • hydrophilic/hydrophobic and accordingly the amount of hydrophilic and hydrophobic fibers within fluid-absorbent composition will depend upon fluid handling properties and the amount of water-absorbent polymer particles of the resulting fluid-absorbent composition.
  • hydrophilic fibers examples are cellulosic fibers, modified cellulosic fibers, rayon, polyester fibers such as polyethylen terephthalate, hydrophilic nylon and the like.
  • Hydrophilic fibers can also be obtained from hydrophobic fibers which are hydrophilized by e. g. surfactant-treating or silica-treating.
  • hydrophilic thermoplastic fibers derived from polyolefins such as polypropylene, polyamides, polystyrenes or the like by surfactant-treating or silica-treating.
  • the fibers should generally show bonding sites, which act as crosslinks between the fibers within the layer.
  • Preferred means of increasing the integrity are thermal bonding, spunbonding, resin bonding, through-air bonding and/or spunlace.
  • thermoplastic material is added to the fibers. Upon thermal treatment at least a portion of this thermoplastic material is melting and migrates to intersections of the fibers caused by capillary effects. These intersections solidify to bond sites after cooling and increase the integrity of the fibrous matrix. Moreover, in the case of chemically stiffened cellulosic fibers, melting and migration of the thermoplastic material has the effect of increasing the pore size of the resultant fibrous layer while maintaining its density and basis weight. Upon wetting, the structure and integrity of the layer remains stable. In summary, the addition of thermoplastic material leads to improved fluid permeability of discharged body fluids and thus to improved acquisition properties.
  • thermoplastic materials including polyolefins such as polyethylene and polypropylene, polyesters, copolyesters, polyvinyl acetate, polyethylvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylics, polyamides, copolyamides, polystyrenes, polyurethanes and copolymers of any of the mentioned polymers.
  • thermoplastic fibers can be made from a single polymer that is a monocomponent fiber. Alternatively, they can be made from more than one polymer, e.g., bi-component or multi-component fibers.
  • the term “bicomponent fibers” refers to thermoplastic fibers that comprise a core fiber made from a different fiber material than the shell. Typically, both fiber materials have different melting points, wherein generally the sheath melts at lower temperatures.
  • Bi-component fibers can be concentric or eccentric depending whether the sheath has a thickness that is even or uneven through the cross-sectional area of the bi-component fiber. Advantage is given for eccentric bi-component fibers showing a higher compressive strength at lower fiber thickness. Further bi-component fibers can show the feature “uncrimped” (unbent) or “crimped” (bent), further bi-component fibers can demonstrate differing aspects of surface lubricity.
  • bi-component fibers include the following polymer combinations: polyethylene/polypropylene, polyethylvinyl acetate/polypropylene, polyethylene/polyester, polypropylene/polyester, copolyester/polyester and the like.
  • thermoplastic materials have a melting point of lower temperatures that will damage the fibers of the layer; but not lower than temperatures, where usually the fluid-absorbent articles are stored. Preferably the melting point is between about 75° C. and 175° C.
  • the typical length of thermoplastic fibers is from about 0.4 to 6 cm, preferably from about 0.5 to 1 cm.
  • the diameter of thermoplastic fibers is defined in terms of either denier (grams per 9000 meters) or dtex (grams per 10 000 meters).
  • Typical thermoplastic fibers have a dtex in the range from about 1.2 to 20, preferably from about 1.4 to 10.
  • a further mean of increasing the integrity of the fluid-absorbent composition is the spunbonding technology.
  • the nature of the production of fibrous layers by means of spunbonding is based on the direct spinning of polymeric granulates into continuous filaments and subsequently manufacturing the fibrous layer.
  • Spunbond fabrics are produced by depositing extruded, spun fibers onto a moving belt in a uniform random manner followed by thermal bonding the fibers.
  • the fibers are separated during the web laying process by air jets.
  • Fiber bonds are generated by applying heated rolls or hot needles to partially melt the polymer and fuse the fibers together. Since molecular orientation increases the melting point, fibers that are not highly drawn can be used as thermal binding fibers.
  • Polyethylene or random ethylene/propylene copolymers are used as low melting bonding sites.
  • the technology of resin bonding also belongs to thermal bonding sub-jects. Using this technology to generate bonding sites, specific adhesives, based on e.g. epoxy, polyurethane and acrylic are added to the fibrous material and the resulting matrix is thermically treated. Thus the web is bonded with resin and/or thermal plastic resins dispersed within the fibrous material.
  • through-air bonding involves the application of hot air to the surface of the fibrous fabric.
  • the hot air is circulated just above the fibrous fabric, but does not push through the fibrous fabric. Bonding sites are generated by the addition of binders.
  • Suitable binders used in through-air thermal bonding include crystalline binder fibers, bi-component binder fibers, and powders. When using crystalline binder fibers or powders, the binder melts entirely and forms molten droplets throughout the nonwoven's cross-section. Bonding occurs at these points upon cooling. In the case of sheath/core binder fibers, the sheath is the binder and the core is the carrier fiber.
  • Products manufactured using through-air ovens tend to be bulky, open, soft, strong, extensible, breathable and absorbent.
  • Through-air bonding followed by immediate cold calendering results in a thick-ness between a hot roll calendered product and one that has been though-air bonded without compression. Even after cold calendering, this product is softer, more flexible and more extensible than area-bond hot-calendered material.
  • Spunlacing (“hydroentanglement”) is a further method of increasing the integrity of a web.
  • the formed web of loose fibers (usually air-laid or wet-laid) is first compacted and prewetted to eliminate air pockets.
  • the technology of spunlacing uses multiple rows of fine high-speed jets of water to strike the web on a porous belt or moving perforated or patterned screen so that the fibers knot about one another.
  • the water pressure generally increases from the first to the last injectors. Pressures as high as 150 bar are used to direct the water jets onto the web. This pressure is sufficient for most of the nonwoven fibers, although higher pressures are used in specialized applications.
  • the spunlace process is a nonwovens manufacturing system that employs jets of water to entangle fibers and thereby provide fabric integrity. Softness, drape, conformability, and relatively high strength are the major characteristics of spunlace nonwoven
  • the thickness of the layer is very important and influences together with its x-y dimension the acquisition-distribution behaviour of the layer. If there is further some profiled structure integrated, the acquisition-distribution behaviour can be directed depending on the three-dimensional structure of the layer.
  • 3D-polyethylene in the function of liquid-pervious layer is preferred. Suitable techniques to create such 3D structures are e.g. embossing, needle-punching, or stitching.
  • suitable liquid-pervious sheets ( 89 ) are nonwoven layers formed from the fibers above by thermal bonding, spunbonding, resin bonding or through-air bonding. Further suitable liquid-pervious layers are 3D-polyethylene layers and spunlace.
  • the 3D-polyethylene layers and spunlace show basis weights from 12 to 22 gsm.
  • Acquisition-distribution layer is optional. Many Absorbent Paper diapers do not have an ADL, but advanced topsheets (air-thru bond nonwovens with 3D structure; often a combination of 2 topsheets).
  • Preferred topsheets which may also substitute an acquisition-distribution layer are air-thru nonwovens with 3D structure.
  • topsheets Most preferred are the use of 2 layers of topsheets.
  • the outer layer having a 3D structure, the inner one without 3D structure. Both sheets are glued together to prevent that the 3D structure of the outer topsheet layer is destroyed by e.g. any stretching steps during the production process of the fluid-absorbent article e.g. a diaper.
  • liquid-pervious sheets ( 89 ) extend partially or wholly across the fluid-absorbent structure and can extend into and/or form part of all the preferred sideflaps, side wrapping elements, wings and ears.
  • the liquid-impervious sheet ( 83 ) prevents the exudates absorbed and retained by the flu-id-absorbent core from wetting articles which are in contact with the fluid-absorbent article, as for example bedsheets, pants, pyjamas and undergarments.
  • the liquid-impervious sheet ( 83 ) may thus comprise a woven or a nonwoven material, polymeric films such as thermoplastic film of polyethylene or polypropylene, or composite materials such as film-coated nonwoven material.
  • Suitable liquid-impervious sheets ( 83 ) include nonwoven, plastics and/or laminates of plastic and nonwoven. Both, the plastics and/or laminates of plastic and nonwoven may appropriately be breathable, that is, the liquid-impervious layer ( 83 ) can permit vapors to escape from the fluid-absorbent material. Thus the liquid-impervious sheet has to have a definite water vapor transmission rate and at the same time the level of impermeability.
  • suitable liquid-impervious layers including at least two layers, e.g. laminates from fibrous nonwoven having a specified basis weight and pore size, and a continuous three-dimensional film of e.g.
  • suitable liquid-impervious layers comprising at least a first breathable layer of a porous web which is a fibrous nonwoven, e.g. a composite web of a meltblown nonwoven layer or of a spunbonded nonwoven layer made from synthetic fibers and at least a second layer of a resilient three dimensional web consisting of a liquid-impervious polymeric film, e.g. plastics optionally having pores acting as capillaries, which are preferably not perpendicular to the plane of the film but are disposed at an angle of less than 90° relative to the plane of the film.
  • Suitable liquid-impervious sheets are permeable for vapor.
  • the liquid-impervious sheet is constructed from vapor permeable material showing a water vapor transmission rate (WVTR) of at least about 100 gsm per 24 hours, preferably at least about 250 gsm per 24 hours and most preferred at least about 500 gsm per 24 hours.
  • WVTR water vapor transmission rate
  • the liquid-impervious sheet ( 83 ) is made of nonwoven comprising hydrophobic materials, e.g. synthetic fibers or a liquid-impervious polymeric film comprising plastics e.g. polyethylene.
  • the thickness of the liquid-impervious sheet is preferably 15 to 30 ⁇ m.
  • liquid-impervious sheet ( 83 ) is preferably made of a laminate of nonwoven and plastics comprising a nonwoven having a density of 12 to 15 gsm and a polyethylene layer having a thickness of about 10 to 20 ⁇ m.
  • the typically liquid-impervious sheet ( 83 ) extends partially or wholly across the fluid-absorbent structure and can extend into and/or form part of all the preferred sideflaps, side wrapping elements, wings and ears.
  • fluid-absorbent articles it is advantageous especially in respect to fluid distribution to have acquisition-distribution layers.
  • a fluid-absorbent core comprising very permeable water-absorbent polymer particles
  • a small and thin acquisition-distribution layer ( 70 ) can be used.
  • the acquisition-distribution layer ( 70 ) acts as transport and distribution layer of the discharged body fluids and is typically optimized to affect efficient liquid distribution with the underlying fluid-absorbent core. Hence, for quick temporary liquid retention it provides the necessary void space while its area coverage of the underlying fluid-absorbent core must affect the necessary liquid distribution and is adopted to the ability of the fluid-absorbent core to quickly dewater the acquisition-distribution layer.
  • An acquisition-distribution layer ( 70 ) is located between the upper layer (A) ( 89 ) and the fluid-absorbent core ( 80 ) and is preferably constructed to efficiently acquire discharged body fluids and to transfer and distribute them to other regions of the fluid-absorbent composition or to other layers, where the body fluids are immobilized and stored.
  • the upper layer transfers the discharged liquid to the acquisition-distribution layer (D) for distributing it to the flu-id-absorbent core.
  • the acquisition-distribution layer ( 70 ) comprises fibrous material and optionally water-absorbent polymer particles.
  • the fibrous material may be hydrophilic, hydrophobic or can be a combination of both hydrophilic and hydrophobic fibers. It may be derived from natural fibers, synthetic fibers or a combination of both.
  • Suitable acquisition-distribution layers are formed from cellulosic fibers and/or modified cellulosic fibers and/or synthetics or combinations thereof.
  • suitable acquisition-distribution layers may contain cellulosic fibers, in particular wood pulp fluff.
  • suitable hydrophilic, hydrophobic fibers, as well as modified or unmodified natural fibers are given in the chapter “Liquid-pervious sheet or liquid pervious layer ( 89 )” above.
  • modified cellulosic fibers are preferred.
  • modified cellulosic fibers are chemically treated cellulosic fibers, especially chemically stiffened cellulosic fibers.
  • chemically stiffened cellulosic fibers means cellulosic fibers that have been stiffened by chemical means to increase the stiffness of the fibers. Such means include the addition of chemical stiffening agent in the form of surface coatings, surface cross-linking and impregnates.
  • Suitable polymeric stiffening agents can include: cationic modified starches having nitrogen-containing groups, latexes, wet strength resins such as polyamide-epichlorohydrin resin, polyacrylamide, urea formaldehyde and melamine formaldehyde resins and polyethylenimine resins
  • Stiffening may also include altering the chemical structure, e.g. by crosslinking polymer chains.
  • crosslinking agents can be applied to the fibers that are caused to chemically form intrafiber crosslink bonds.
  • Further cellulosic fibers may be stiffened by crosslink bonds in individualized form.
  • Suitable chemical stiffening agents are typically monomeric crosslinking agents including C2-C8 dialdehyde, C2-C8 monoaldehyde having an acid functionality, and especially C2-C9 polycarboxylic acids.
  • the modified cellulosic fibers are chemically treated cellulosic fibers.
  • curly fibers which can be obtained by treating cellulosic fibers with citric acid.
  • the basis weight of cellulosic fibers and modified cellulosic fibers is from 50 to 200 gsm.
  • Suitable acquisition-distribution layers further include synthetic fibers.
  • synthetic fibers are found in the Chapter “Liquid-pervious sheet or liquid pervious layer ( 89 )” above.
  • Another possibility available is 3D-polyethylene film with dual function as a liquid-pervious layer ( 89 ) and acquisition-distribution layer.
  • hydrophilic synthetic fibers may be obtained by chemical modification of hydrophobic fibers.
  • hydrophilization is carried out by surfactant treatment of hydrophobic fibers.
  • the surface of the hydrophobic fiber can be rendered hydrophilic by treatment with a nonionic or ionic surfactant, e.g., by spraying the fiber with a surfactant or by dipping the fiber into a surfactant.
  • a nonionic or ionic surfactant e.g., by spraying the fiber with a surfactant or by dipping the fiber into a surfactant.
  • permanent hydrophilic synthetic fibers are permanent hydrophilic synthetic fibers.
  • the fibrous material of the acquisition-distribution layer may be fixed to increase the strength and the integrity of the layer.
  • Technologies for consolidating fibers in a web are mechanical bonding, thermal bonding and chemical bonding. Detailed description of the different methods of increasing the integrity of the web is given in the Chapter “Liquid-pervious sheet or liquid pervious layer ( 89 )” above.
  • Preferred acquisition-distribution layers comprise fibrous material and water-absorbent polymer particles distributed within.
  • the water-absorbent polymer particles may be added during the process of forming the layer from loose fibers, or, alternatively, it is possible to add monomer solution after the formation of the layer and polymerize the coating solution by means of UV-induced polymerisation technologies.
  • “in situ”-polymerisation is a further meth-od for the application of water-absorbent polymers.
  • suitable acquisition-distribution layers comprising from 80 to 100% by weight a fibrous material and from 0 to 20% by weight water-absorbent polymer particles; preferably from 85 to 99.9% by weight a fibrous material and from 0.1 to 15% by weight water-absorbent polymer particles; more preferably from 90 to 99.5% by weight a fibrous material and from 0.5 to 10% by weight water-absorbent polymer particles; and most preferably from 95 to 99% by weight a fibrous material and from 1 to 5% by weight water-absorbent polymer particles
  • a liquid-impervious layer comprising a synthetic resin film between ( 89 ) and ( 80 ) acting as a distribution layer ( 70 ) and quickly transporting the supplied urine along the surface to the upper lateral portion of the fluid-absorbent core ( 80 ).
  • the upper liquid-impervious layer ( 70 ) is smaller than the underlaying fluid-absorbent core ( 80 ).
  • Such a film made of a resin such as polyethylene, polypropylene, polyethylene therephthalate, polyurethane, or crosslinked polyvinyl alcohol and an air-permeable, but liquid-impervious, so-called: “breathable” film made of above described resin, may be used.
  • the upper liquid-impervious layer ( 70 ) comprises a porous polyethylene film for both quick acquisition and distribution of flu-id.
  • a bundle of synthetic fibers acting as acquisition-distribution layer loosely distributed on top of the fluid-absorbent core may be used.
  • Suitable synthetic fibers are of copolyester, polyamide, copolyamide, polylactic acid, polypropylene or polyethylene, viscose or blends thereof.
  • Further bicomponent fibers can be used.
  • the synthetic fiber component may be composed of either a single fiber type with a circular cross-section or a blend of two fibre types with different cross-sectional shapes. Synthetic fibers arranged in that way ensuring a very fast liquid transport and change. Preferably bundles of polyethylene fibers are used.
  • fluid-absorbent articles without an Acquisition distribution layer.
  • these articles have some advantages such as they are thinner, softer and cheaper than articles with an ADL present.
  • the production process of absorbent articles is less cost efficient and comprise less steps e.g. no cutting and placing of the ADL is necessary.
  • Typical leg cuffs comprising nonwoven materials which can be formed by direct extrusion processes during which the fibers and the nonwoven materials are formed at the same time, or by laying processes of preformed fibers which can be laid into nonwoven materials at a later point of time.
  • Examples for direct extrusion processes include spunbonding, melt-blowing, solvent spinning, electrospinning and combinations thereof.
  • Examples of laying processes include wet-laying and dry-laying (e.g. air-laying, carding) methods.
  • Combinations of the processes above include spunbond-meltblown-spunbond (sms), spunbond-meltblow-meltblown-spunbond (smms), spunbond-carded (sc), spunbond-airlaid (sa), melt-blown-airlaid (ma) and combinations thereof.
  • the combinations including direct extrusion can be combined at the same point in time or at a subsequent point in time.
  • one or more individual layers can be produced by each process.
  • “sms” means a three layer nonwoven material
  • smsms” or “ssmms” means a five layer nonwoven material.
  • small type letters (sms) designate individual layers
  • SMS capital letters
  • leg cuffs are provided with elastic strands.
  • leg cuffs from synthetic fibers showing the layer combinations sms, smms or smsms. Preferred are nonwovens with the density of 13 to 17 gsm. Preferably leg cuffs are provided with two elastic strands.
  • the measurements should, unless stated otherwise, be carried out at an ambient temperature of 23 ⁇ 2° C. and a relative atmospheric humidity of 50 ⁇ 10%.
  • the superabsorbent polymers are mixed thoroughly before the measurement.
  • the absorbency under no load of the superabsorbent polymer particles is determined analogously to the EDANA recommended test method No. WSP 242.2 (05) “Gravimetric Determinetion of Absorption Under Pressure”, except using a weight of 0.0 g/cm 2 instead of a weight of 21.0 g/cm 2 .
  • the absorbency under load of the superabsorbent polymer particles is determined by the EDANA recommended test method No. WSP 242.2 (05) “Gravimetric Determination of Absorption Under Pressure”.
  • the absorbency under high load of the superabsorbent polymer particles is determined analogously to the EDANA recommended test method No. WSP 242.2 (05) “Gravimetric Determination of Absorption Under Pressure”, except using a weight of 49.2 g/cm 2 instead of a weight of 21.0 g/cm 2 .
  • the bulk density of the superabsorbent polymer particles is determined by the EDANA recommended test method No. WSP 260.2 (05) “Gravimetric Determination of Density”.
  • the percent of the particles which are non-caking is then determined by the following formula:
  • W d is the weight of aluminum dish
  • W HYD is the weight of hydrated polymer plus aluminum dish before sifting
  • W PAN is the weight of the collection pan
  • W UNC is the weight of collection pan and hydrated polymer.
  • the centrifuge retention capacity of superabsorbent polymer particles is determined by the EDANA recommended test method No. WSP 241.2 (05) “Gravimetric Determination of Flu-id Retention Capacity in Saline Solution After Centrifugation”, wherein for higher values of the centrifuge retention capacity lager tea bags have to be used.
  • the Hunter 60 value (HC60) is a measure of the whiteness of surfaces and is defined as:
  • the measurement of the color value is in agreement with the tristimulus method according to DIN 5033-6.
  • the content of extractable constituents in superabsorbent polymer particles is determined analogously to the EDANA recommended test method No. WSP 270.2 (05) “Determination of Extractable Polymer Content by Potentiometric Titration”, except stirring for 1 hour instead of stirring for 16 hours.
  • the content of extractable constituents in superabsorbent polymer particles is determined by the EDANA recommended test method No. WSP 270.2 (05) “Determination of Extractable Polymer Content by Potentiometric Titration”.
  • FSC free swell capacity
  • m si is the mass, expressed in grams, of dry test portion
  • m b is the average mass, expressed in grams, of the 2 wet blank bags
  • Time to reach a liquid uptake of 20 g/g is determined by the method disclosed in EP 2 535 027 A1 on pages 13 to 18, “K(t) Test Method (Dynamic Effective Permeability and Uptake Kinetics Measurement Test Method)”.
  • the particle size distribution of the superabsorbent polymer particles is determined by the EDANA recommended test method No. WSP 220.2 (05) “Determination of Polyacrylate Superabsorbent Powders and Particle Size Distribution—Sieve Fractionation”.
  • the roundness is determined with the PartAn® 3001 L Particle Analyzer (Microtrac Europe GmbH; Meerbusch; Germany). The roundness is defined as
  • A is the cross-sectional area and U is the cross-sectional circumference of the polymer particles.
  • the roundness is the volume-average roundness.
  • the volume of the particles is determined via the minimal Feret diameter X Fmin .
  • the minimal Feret diameter X Fmin is the smallest distance between two parallel tangents applicable to the shape of the particle.
  • VAUL Volumetric Absorption Under Load
  • aqueous saline solution (0.9% by weight) are added into the PTFE cell ( 86 ) with a syringe and the recording is started. During the swelling, the water-absorbent polymer particles push the cylinder ( 87 ) up and the changes in the distance between the metal reflector ( 88 ) and the sensor ( 85 ) are recorded.
  • the measurements are repeated for different pressures (0.1 psi, 0.3 psi, 0.5 psi and 0.7 psi) using combinations of cylinder and ring weights.
  • the dosing position is 5 cm from center toward front of product.
  • the dosing position is 2.5 cm from center toward front of product.
  • the liquid diffusion length should be measured after 5 min from the liquid dosing into the specimen each time.
  • the water pouring rewet is calculated as: m 2 ⁇ m 1 .
  • the process was performed in a concurrent spray drying plant with an integrated fluidized bed ( 27 ) as shown in FIG. 6 .
  • the reaction zone ( 5 ) had a height of 22 m and a diameter of 3.4 m.
  • the internal fluidized bed (IFB) had a diameter of 3 m and a weir height of 0.25 m.
  • the drying gas was fed via a gas distributor ( 3 ) at the top of the spray dryer.
  • the drying gas was partly recycled (drying gas loop) via a cyclone as dust separation unit ( 9 ) and a condenser column ( 12 ).
  • the drying gas was nitrogen that comprises from 1% to 4% by volume of residual oxygen. Prior to the start of polymerization the drying gas loop was filled with nitrogen until the residual oxygen was below 4% by volume.
  • the gas velocity of the drying gas in the reaction zone ( 5 ) was 0.79 m/s.
  • the pressure inside the spray dryer was 4 mbar below ambient pressure.
  • the temperature of the gas leaving the reaction zone ( 5 ) was measured at three points around the circumference at the end of the cylindrical part of the spray dryer as shown in FIG. 7 .
  • Three single measurements ( 43 ) were used to calculate the average temperature (spray dryer outlet temperature).
  • the drying gas loop was heated up and the dosage of monomer solution is started up. From this time the spray dryer outlet temperature was controlled to 114° C. by adjusting the gas inlet temperature via the heat exchanger ( 20 ).
  • the gas inlet temperature was 167° C. and the steam content of the drying gas is shown in table 1.
  • the product accumulated in the internal fluidized bed ( 27 ) until the weir height was reached.
  • Conditioned internal fluidized bed gas having a temperature of 105° was fed to the internal fluidized bed ( 27 ) via line ( 25 ).
  • the gas velocity of the internal fluidized bed gas in the internal fluidized bed ( 27 ) was 0.65 m/s.
  • the residence time of the product was 150 min.
  • the temperature of the superabsorbent polymer particles in the internal fluidized bed ( 27 ) was 71° C.
  • the spray dryer off-gas was filtered in cyclone as dust separation unit ( 9 ) and sent to a condenser column ( 12 ) for quenching/cooling. Excess water was pumped out of the condenser column ( 12 ) by controlling the (constant) filling level inside the condenser column ( 12 ). The water inside the condenser column ( 12 ) was cooled by a heat exchanger ( 13 ) and pumped counter-current to the gas. The temperature and the steam content of the gas leaving the condenser column ( 12 ) are shown in table 5. The water inside the condenser column ( 12 ) was set to an alkaline pH by dosing sodium hydroxide solution to wash out acrylic acid vapors.
  • the gas leaving the condenser column ( 12 ) was split to the drying gas inlet pipe ( 1 ) and the conditioned internal fluidized bed gas ( 25 ).
  • the gas temperatures were controlled via heat exchangers ( 20 ) and ( 22 ).
  • the hot drying gas was fed to the concurrent spray dryer via gas distributor ( 3 ).
  • the gas distributor ( 3 ) consists of a set of plates providing a pressure drop of 2 to 4 mbar depending on the drying gas amount.
  • the product was discharged from the internal fluidized bed ( 27 ) via rotary valve ( 28 ) into sieve ( 29 ).
  • the sieve ( 29 ) was used for sieving off overs/lumps having a particle diameter of more than 800 ⁇ m.
  • the monomer solution was prepared by mixing first acrylic acid with 3-tuply ethoxylated glycerol triacrylate (internal crosslinker), secondly with 37.3% by weight sodium acrylate solution and thirdly with aqueous of disodium 1-hydroxyethane-1,1-diphosphonic acid (HDPA).
  • the temperature of the resulting monomer solution was controlled to 10° C. by using a heat exchanger and pumping in a loop.
  • a filter unit having a mesh size of 250 ⁇ m was used in the loop after the pump.
  • the initiators were metered into the monomer solution upstream of the dropletizer by means of static mixers ( 31 ) and ( 32 ) via lines ( 33 ) and ( 34 ) as shown in FIG. 6 .
  • a dropletizer unit consisted of an outer pipe ( 47 ) having an opening for the dropletizer cassette ( 49 ) as shown in FIG. 5 of WO 2016/134905 A1.
  • the dropletizer cassette ( 49 ) was connected with an inner pipe ( 48 ).
  • the inner pipe ( 48 ) having a PTFE block ( 50 ) at the end as sealing can be pushed in and out of the outer pipe ( 47 ) during operation of the process for maintenance purposes.
  • the temperature of the dropletizer cassette ( 49 ) was controlled to 8° C. by water in flow channels ( 55 ) as shown in FIG. 8 of WO 2016/134905 A1
  • the dropletizer cassette ( 49 ) had 256 bores having a diameter of 170 ⁇ m and a bore spacing of 15 mm.
  • the dropletizer cassette ( 49 ) consisted of a flow channel ( 56 ) having essential no stagnant volume for homogeneous distribution of the premixed monomer and initiator solutions and one droplet plate ( 53 ).
  • the droplet plate ( 53 ) had an angled configuration with an angle of 3°.
  • the droplet plate ( 53 ) was made of stainless steel and had a length of 630 mm, a width of 128 mm and a thickness of 1 mm.
  • the feed to the spray dryer consisted of 10.45% by weight of acrylic acid, 33.40% by weight of sodium acrylate, 0.018% by weight of 3-tuply ethoxylated glycerol triacrylate, 0.108% by weight of disodium 1-hydroxyethane-1,1-diphosphonic acid (HDPA), 0.072% by weight of [2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 0.072% by weight of sodiumperoxodisulfate solution (15% by weight in water) and water. The degree of neutralization was 71%.
  • the feed per bore was 1.4 kg/h.
  • the process was performed in a concurrent spray drying plant with an integrated fluidized bed ( 27 ) as shown in FIG. 6 .
  • the reaction zone ( 5 ) had a height of 22 m and a diameter of 3.4 m.
  • the internal fluidized bed (IFB) had a diameter of 3 m and a weir height of 0.25 m.
  • the dropletizer cassette ( 49 ) had 508 bores having a diameter of 120 ⁇ m and a bore spacing of 8 mm.
  • the drying gas was fed via a gas distributor ( 3 ) at the top of the spray dryer.
  • the drying gas was partly recycled (drying gas loop) via a cyclone as dust separation unit ( 9 ) and a condenser column ( 12 ).
  • the drying gas was nitrogen that comprises from 1% to 4% by volume of residual oxygen. Prior to the start of polymerization the drying gas loop was filled with nitrogen until the residual oxygen was below 4% by volume.
  • the gas velocity of the drying gas in the reaction zone ( 5 ) was 0.79 m/s.
  • the pressure inside the spray dryer was 4 mbar below ambient pressure.
  • the temperature of the gas leaving the reaction zone ( 5 ) was measured at three points around the circumference at the end of the cylindrical part of the spray dryer as shown in FIG. 7 .
  • Three single measurements ( 43 ) were used to calculate the average temperature (spray dryer outlet temperature).
  • the drying gas loop was heated up and the dosage of monomer solution is started up. From this time the spray dryer outlet temperature was controlled to 118° C. by adjusting the gas inlet temperature via the heat exchanger ( 20 ).
  • the gas inlet temperature was 179° C. and the steam content of the drying gas is shown in table 1.
  • the product accumulated in the internal fluidized bed ( 27 ) until the weir height was reached.
  • Conditioned internal fluidized bed gas having a temperature of 106° was fed to the internal fluidized bed ( 27 ) via line ( 25 ).
  • the gas velocity of the internal fluidized bed gas in the internal fluidized bed ( 27 ) was 0.65 m/s.
  • the residence time of the product was 150 min.
  • the temperature of the superabsorbent polymer particles in the internal fluidized bed ( 27 ) was 78° C.
  • the spray dryer off-gas was filtered in cyclone as dust separation unit ( 9 ) and sent to a condenser column ( 12 ) for quenching/cooling. Excess water was pumped out of the condenser column ( 12 ) by controlling the (constant) filling level inside the condenser column ( 12 ). The water inside the condenser column ( 12 ) was cooled by a heat exchanger ( 13 ) and pumped counter-current to the gas. The temperature and the steam content of the gas leaving the condenser column ( 12 ) are shown in table 5. The water inside the condenser column ( 12 ) was set to an alkaline pH by dosing sodium hydroxide solution to wash out acrylic acid vapors.
  • the gas leaving the condenser column ( 12 ) was split to the drying gas inlet pipe ( 1 ) and the conditioned internal fluidized bed gas ( 25 ).
  • the gas temperatures were controlled via heat exchangers ( 20 ) and ( 22 ).
  • the hot drying gas was fed to the concurrent spray dryer via gas distributor ( 3 ).
  • the gas distributor ( 3 ) consists of a set of plates providing a pressure drop of 2 to 4 mbar depending on the drying gas amount.
  • the product was discharged from the internal fluidized bed ( 27 ) via rotary valve ( 28 ) into sieve ( 29 ).
  • the sieve ( 29 ) was used for sieving off overs/lumps having a particle diameter of more than 800 ⁇ m.
  • the monomer solution was prepared by mixing first acrylic acid with 3-tuply ethoxylated glycerol triacrylate (internal crosslinker), secondly with 37.3% by weight sodium acrylate solution and thirdly with aqueous of disodium 1-hydroxyethane-1,1-diphosphonic acid (HDPA).
  • the temperature of the resulting monomer solution was controlled to 10° C. by using a heat exchanger and pumping in a loop.
  • a filter unit having a mesh size of 250 ⁇ m was used in the loop after the pump.
  • the initiators were metered into the monomer solution upstream of the dropletizer by means of static mixers ( 31 ) and ( 32 ) via lines ( 33 ) and ( 34 ) as shown in FIG. 6 .
  • a dropletizer unit consisted of an outer pipe ( 47 ) having an opening for the dropletizer cassette ( 49 ) as shown in FIG. 5 of WO 2016/134905 A1.
  • the dropletizer cassette ( 49 ) was connected with an inner pipe ( 48 ).
  • the inner pipe ( 48 ) having a PTFE block ( 50 ) at the end as sealing can be pushed in and out of the outer pipe ( 47 ) during operation of the process for maintenance pur-poses.
  • the dropletizer cassette ( 49 ) had 508 bores having a diameter of 120 ⁇ m and a bore spacing of 8 mm.
  • the dropletizer cassette ( 49 ) consisted of a flow channel ( 56 ) having essential no stagnant volume for homogeneous distribution of the premixed monomer and initiator solutions and one droplet plate ( 53 ).
  • the droplet plate ( 53 ) had an angled configuration with an angle of 3°.
  • the droplet plate ( 53 ) was made of stainless steel and had a length of 630 mm, a width of 128 mm and a thickness of 1 mm.
  • the feed to the spray dryer consisted of 10.45% by weight of acrylic acid, 33.40% by weight of sodium acrylate, 0.018% by weight of 3-tuply ethoxylated glycerol triacrylate, 0.108% by weight of disodium 1-hydroxyethane-1,1-diphosphonic acid (HDPA), 0.072% by weight of [2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 0.072% by weight of sodiumperoxodisulfate solution (15% by weight in water) and water. The degree of neutralization was 71%.
  • the feed per bore was 1.4 kg/h.
  • the example was performed analogous to example 3.
  • the feed to the spray dryer consisted of 10.45% by weight of acrylic acid, 33.40% by weight of sodium acrylate, 0.018% by weight of 3-tuply ethoxylated glycerol triacrylate, 0.216% by weight of disodium 1-hydroxyethane-1,1-diphosphonic acid (HDPA), 0.072% by weight of [2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 0.072% by weight of sodiumperoxodisulfate solution (15% by weight in water) and water.
  • HDPA disodium 1-hydroxyethane-1,1-diphosphonic acid
  • the example was performed analogous to example 3.
  • the feed to the spray dryer consisted of 10.45% by weight of acrylic acid, 33.40% by weight of sodium acrylate, 0.018% by weight of 3-tuply ethoxylated glycerol triacrylate, 0.216% by weight of disodium 1-hydroxyethane-1,1-diphosphonic acid (HDPA), 0.018% by weight of disodium 2-hydroxy-2-sulfonato acetic acid (HSAA), 0.072% by weight of [2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 0.072% by weight of sodiumperoxodisulfate solution (15% by weight in water) and water.
  • HDPA disodium 1-hydroxyethane-1,1-diphosphonic acid
  • HSAA disodium 2-hydroxy-2-sulfonato acetic acid
  • the example was performed analogous to example 3.
  • the feed to the spray dryer consisted of 10.45% by weight of acrylic acid, 33.40% by weight of sodium acrylate, 0.018% by weight of 3-tuply ethoxylated glycerol triacrylate, 0.216% by weight of disodium 1-hydroxyethane-1,1-diphosphonic acid (HDPA), 0.036% by weight of disodium 2-hydroxy-2-sulfonato acetic acid (HSAA), 0.072% by weight of [2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 0.072% by weight of sodiumperoxodisulfate solution (15% by weight in water) and water.
  • HDPA disodium 1-hydroxyethane-1,1-diphosphonic acid
  • HSAA disodium 2-hydroxy-2-sulfonato acetic acid
  • the example was performed analogous to example 3.
  • the feed to the spray dryer consisted of 10.45% by weight of acrylic acid, 33.40% by weight of sodium acrylate, 0.018% by weight of 3-tuply ethoxylated glycerol triacrylate, 0.216% by weight of disodium 1-hydroxyethane-1,1-diphosphonic acid (HDPA), 0.072% by weight of disodium 2-hydroxy-2-sulfonato acetic acid (HSAA), 0.072% by weight of [2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 0.072% by weight of sodiumperoxodisulfate solution (15% by weight in water) and water.
  • HDPA disodium 1-hydroxyethane-1,1-diphosphonic acid
  • HSAA disodium 2-hydroxy-2-sulfonato acetic acid
  • the thermal dryer ( 65 ) has two paddles with a shaft offset of 90° ( 80 ) and a fixed discharge zone ( 71 ) with two flexible weir plates ( 73 ). Each weir has a weir opening with a minimal weir height at 50% ( 75 ) and a maximal weir opening at 100% ( 74 ) as shown in FIG. 15 of WO 2015/110321 A1.
  • the inclination angle ⁇ ( 78 ) between the floor plate and the thermal dryer was approx. 3°.
  • the weir height of the thermal dryer was between 50 to 100%, corresponding to a residence time of approx. 40 to 150 min, by a product density of approx. 700 to 750 kg/m 3 .
  • the product temperature in the thermal dryer was in a range of 120 to 165° C.
  • the surface-postcross-linked polymer was transported over discharge cone ( 77 ) in a cooler (model NPD 5W-18, manufactured by GMF Gouda, Waddinxveen, the Netherlands), to cool down the surface postcross-linked polymer to approx. 60° C. with a speed of 11 rpm and a weir height of 145 mm. After cooling, the material was sieved with a minimum cut size of 150 ⁇ m and a maximum cut size of 850 ⁇ m.
  • the material was sieved with only with a maximum cut size of 850 ⁇ m. No additional minimum cut sieve was used.
  • TABLE 1 Process conditions of the polymerization Bore T T T Size gas gas gas gas T T T T Diameter inlet outlet IFB IFB CC GDU Example ⁇ m ° C. ° C. ° C. ° C. ° C. 1 170 167 114 105 71 56 47 2 120 167 114 105 71 56 47 3-7 120 179 118 106 78 56 47
  • T gas inlet temperature of the gas prior to the gas distributor (3)
  • T gas outlet temperature of the gas leaving the reaction zone (5)
  • T IFB temperature of the superabsorbent polymer particles in the fluidized bed (27)
  • T CC temperature of the gas leaving the condenser column (12)
  • T GDU temperature of the gas leaving the gas drying unit (37)
  • Example 45 45-150 150-200 200-250 250-300 300-400 400-500 500-600 600-710 710-850 >850 D50 Roundness Unit ⁇ m ⁇ m ⁇ m ⁇ m ⁇ m ⁇ m ⁇ m ⁇ m ⁇ m ⁇ m ⁇ m ⁇ m 8*) 0.0 0.2 0.9 4.4 8.3 37.2 37.6 8.5 2.6 0.2 0.1 379 0.83 9*) 0.1 0.3 2.5 10.9 18.0 46.0 18.4 3.0 0.7 0.0 0.0 305 0.82 10 0.0 0.8 3.4 11.7 15.3 38.2 24.2 4.8 1.4 0.1 0.0 308 0.80 11 0.0 0.9 3.6 12.1 15.8 38.5 22.6 4.7 1.6 0.2 0.0 304 0.81 12 0.0 0.8 3.2 11.2 14.6 37.7 25.8 5.1 1.3 0.1 0.0 313 0.80 13 0.0 1.1 3.6 12.1 15.5
  • Hot melt glue (3.0 gsm) (construction hot melt adhesive by Bostik) is sprayed on to tissue bottom layer (40 gsm) (condensed tissue made by Fujian Qiao Dong Paper Co., Ltd.), Superabsorbent (bottom layer) (“SAP 2”) is then applied on to the tissue at 130 gsm loading using roller feeder (commercially available SAP feeder roller type).
  • High loft nonwoven material 40-45 gsm
  • hot melt glue is sprayed on to the nonwoven (0.5 gsm).
  • the nonwoven containing hot melt glue is then laminated with the tissue layer, hot melt glue, and Superabsorbent (SAP 2). This gives the bottom layer of the Absorbent Paper laminate.
  • Another layer is prepared by spraying hot melt glue (3.0 gsm) on to another tissue layer (top layer) (condensed tissue made by Fujian Qiao Dong Paper Co., Ltd.), and then another type of superabsorbent (130 gsm) (“SAP 1”) is applied on to the tissue layer.
  • top layer condensed tissue made by Fujian Qiao Dong Paper Co., Ltd.
  • SAP 1 superabsorbent
  • the first layer and second layer are then laminated together using hot melt glue (0.5 gsm) (construction hot melt adhesive by Bostik) by passing through compression rolls (commercially available metal compression rollers). This results in a complete Absorbent Paper laminate.
  • hot melt glue 0.5 gsm
  • Bostik construction hot melt adhesive by Bostik
  • An Absorbent Paper laminate consists of two layers of superabsorbent polymers (SAP); one of which laid on top side “SAP 1” ( 91 ) and another laid on the bottom of the layer “SAP 2”( 92 ). Both top and bottom SAP layers contain 130 grams per square meter (g/m 2 ). Both layers are in contact with 40-45 g/m 2 air-thru-bond nonwoven material ( 94 ) and are then sandwiched with two layers of 40 g/m 2 condensed tissue layers on the top ( 95 ) and bottom ( 96 ) using hot-melt glue ( 93 ) applied to the surface at 3.0 g/m 2 . Total hot-melt glue used is 3.0 g/m 2 for both top and bottom layers.
  • the laminate (hereunder called specimen) is cut to give 95 mm width and 400 mm length.
  • absorbent paper laminates are produced:
  • inventive examples show improved Water pouring time and/or Water pouring rewet.
  • Hot melt adhesive ( 2 ) (2.5-3.0 gsm) (construction hot melt adhesive by Bostik) is sprayed on to tissue ( 1 ) (40 gsm) (condensed tissue made by Fujian Qiao Dong Paper Co., Ltd.)
  • Superabsorbent SAP ( 3 ) or ( 4 ) or both is applied on to high loft nonwoven material ATB ( 7 )(40-45 gsm) (air-through bond nonwoven of polyester by Fujian Qiao Dong Paper Co., Ltd) at 130 gsm loading using roller feeder (commercially available SAP feeder roller type).
  • roller feeder commercially available SAP feeder roller type.
  • the nonwoven containing SAP is then laminated with the tissue layer at position ( 10 ).
  • Hot melt adhesive ( 8 ) (2.5-3.0 gsm) (construction hot melt adhesive by Bostik) is sprayed on to tissue ( 9 ) (40 gsm).
  • Superabsorbent SAP ( 5 ) or ( 6 ) or both is applied on to the other side of the high loft nonwoven material ATB ( 7 ).
  • the nonwoven containing SAP is then laminated with the tissue layer at position ( 15 ). This gives the 5-layer absorbent paper structure; the laminate is then cut into desired width by slitter ( 11 ).
  • the numbers refer to FIG. 2 .
  • HySorb T 5400 X is produced by BASF Corp., Freeport, Texas, US.
  • Nuoer NR610S is manufactured by Shandong Nuoer Biological Technology Co., Ltd., Shandong Province, Dongying Port Economic Development Zone, P.R. China.
  • Sanwet IM-930 NP is produced at San-Dia Polymers (Nantong) Co., Ltd., No. 5, Xinkai Road (S), Nantong, Economic & Technological Development Area, Jiangsu, P.R. China.
  • SAVIVA ® Transform B3, SAVIVA ® B400, ASAP 535 and ASAP 720 are produced by BASF Antwerpen NV, Belgium.
  • Sumitomo SA60SXII and SA60S are produced by Sumitomo Seika Chemicals Co, Ltd.
  • CAW2020 is produced by Nippon Shokubai Co. Ltd.
  • the inventive examples show improved core utilization (higher liquid diffusion lengths) in the Strike-thru/Rewet test.

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  • Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Veterinary Medicine (AREA)
  • Epidemiology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Public Health (AREA)
  • Hematology (AREA)
  • Materials Engineering (AREA)
  • Dispersion Chemistry (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Absorbent Articles And Supports Therefor (AREA)
US17/048,354 2018-04-20 2019-04-09 Thin fluid absorbent core-absorbent paper Pending US20220071818A9 (en)

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CNPCT/CN2019/074788 2019-02-11
PCT/EP2019/058925 WO2019201668A1 (en) 2018-04-20 2019-04-09 Thin fluid absorbent core-absorbent paper

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EP4190843A4 (en) * 2020-12-18 2024-02-21 Lg Chemical Ltd SUPERABSORBENT POLYMER AND PREPARATION METHOD THEREFOR
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