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US-20260124601-A1 - PARTICULATE WATER-ABSORBING AGENT COMPOSITION PRODUCTION METHOD, PARTICULATE WATER-ABSORBING AGENT COMPOSITION, AND ABSORBENT ARTICLE

US20260124601A1US 20260124601 A1US20260124601 A1US 20260124601A1US-20260124601-A1

Abstract

A particulate water-absorbing agent composition having a high caking resistance performance can be obtained without deteriorating water-absorbing performance under pressure by a method for producing a particulate water-absorbing agent composition, the method including, in at least one step selected from a monomer aqueous solution preparation step, a polymerization step, and an optional hydrogel grinding step, adding a water-soluble polyalkylene glycol having a mass-average molecular weight of 3000 or less in an amount of from 0.01 mass % to 0.25 mass % with respect to a total mass of monomers contained in the monomer aqueous solution, and after the surface crosslinking step, adding a nonionic polymer having a polyalkylene glycol chain in a structure and having a mass-average molecular weight of from 300 to 15000 in an amount of from 0.02 mass % to 0.40 mass % with respect to a water-absorbent resin that has been surface-crosslinked.

Inventors

  • Daisuke Takeda
  • Tadayuki Ogura
  • Manabu Ueda

Assignees

  • NIPPON SHOKUBAI CO., LTD.

Dates

Publication Date
20260507
Application Date
20251230
Priority Date
20230707

Claims (13)

  1. 1 . A method for producing a particulate water-absorbing agent composition including a poly(meth)acrylic acid (salt)-based water-absorbent resin, the method comprising: a monomer aqueous solution preparation step of preparing a (meth)acrylic acid (salt)-based monomer aqueous solution; a polymerization step of polymerizing the (meth)acrylic acid (salt)-based monomer aqueous solution; as an optional step, a hydrogel grinding step of subjecting a resulting crosslinked hydrogel polymer to gel grinding during polymerization or after polymerization; a drying step of drying a particulate hydrogel; as optional steps, a pulverizing step and a classification step of pulverizing and classifying a dried polymer; and a surface crosslinking step of performing surface crosslinking on a water-absorbent resin before surface crosslinking, wherein the particulate hydrogel is obtained through the polymerization step or both the polymerization step and the hydrogel grinding step, the dried polymer is obtained through the drying step, the water-absorbent resin before surface crosslinking is the dried polymer or a water-absorbent resin obtained by pulverizing and/or classifying the dried polymer, at least one step selected from the monomer aqueous solution preparation step, the polymerization step, and the optional hydrogel grinding step includes adding a water-soluble polyalkylene glycol having a mass-average molecular weight of 3000 or less in an amount of from 0.01 mass % to 0.25 mass % with respect to a total mass of monomers contained in the (meth)acrylic acid (salt)-based monomer aqueous solution, and after the surface crosslinking step, a nonionic polymer having a polyalkylene glycol chain in a structure thereof and having a mass-average molecular weight of from 300 to 15000 is added in an amount of from 0.02 mass % to 0.40 mass % with respect to the water-absorbent resin that has been surface-crosslinked.
  2. 2 . The production method according to claim 1 , wherein the particulate water-absorbing agent composition has a surface tension of 45 mN/m or more.
  3. 3 . The production method according to claim 1 , wherein the particulate water-absorbing agent composition has an absorption against pressure (AAP) of 20 g/g or more under pressure of 0.7 psi.
  4. 4 . The production method according to claim 1 , wherein the particulate water-absorbing agent composition has a fixed height absorption (FHA) at a height of 20 cm of 20 g/g or more.
  5. 5 . A particulate water-absorbing agent composition comprising a poly(meth)acrylic acid (salt)-based water-absorbent resin as a main component and a nonionic polymer having a polyalkylene glycol chain in a structure, wherein the particulate water-absorbing agent composition has a mass proportion of particles having a particle diameter of 300 μm or more and less than 850 μm of 50 mass % or more, and wherein the particulate water-absorbing agent composition satisfies all of (1) to (4) shown below when: (a) the nonionic polymer contained in the particulate water-absorbing agent composition is defined as A1, and a content of the nonionic polymer is defined as C1; (b) the particulate water-absorbing agent composition is subjected to a predetermined impact test; (c) the particulate water-absorbing agent composition that has been subjected to the impact test is sieved into a particle group a having a particle diameter of 300 μm or more and a particle group b having a particle diameter of less than 300 μm with a JIS standard sieve; and (d) the nonionic polymer present in the particle group a is defined as A2, and a content of the nonionic polymer is defined as C2: (1) A1 is a water-soluble polyalkylene glycol having a mass-average molecular weight of 3000 or less and a nonionic polymer having a polyalkylene glycol chain in the structure and having a mass-average molecular weight from 300 to 15000; (2) A2 is a water-soluble polyalkylene glycol having a mass-average molecular weight of 3000 or less; (3) C2 is 0.005 mass % or more and 0.15 mass % or less; and (4) C1-C2 is 0.02 mass % or more and 0.40 mass % or less.
  6. 6 . The particulate water-absorbing agent composition according to claim 5 , wherein the particulate water-absorbing agent composition has a surface tension of 45 mN/m or more.
  7. 7 . The particulate water-absorbing agent composition according to claim 5 , wherein the particulate water-absorbing agent composition has an absorption against pressure (AAP) of 20 g/g or more under pressure of 0.7 psi.
  8. 8 . The particulate water-absorbing agent composition according to claim 5 , wherein the particulate water-absorbing agent composition has a fixed height absorption (FHA) at a height of 20 cm of 20 g/g or more.
  9. 9 . The particulate water-absorbing agent composition according to claim 5 , wherein the particulate water-absorbing agent composition has a CRC of 25 g/g or more.
  10. 10 . The particulate water-absorbing agent composition according to claim 5 , wherein the particulate water-absorbing agent composition has a moisture absorption blocking ratio <1>(B. R. <1>) of 80 mass % or less.
  11. 11 . The particulate water-absorbing agent composition according to claim 5 , wherein the particulate water-absorbing agent composition has a mass-average particle diameter (D50) of 300 μm or more and 600 μm or less.
  12. 12 . The particulate water-absorbing agent composition according to claim 5 , wherein a mass proportion of particles having a particle diameter of 850 μm or more in the particulate water-absorbing agent composition is 3 mass % or less, and a mass proportion of particles having a particle diameter less than 150 μm is 5 mass % or less.
  13. 13 . An absorbent article comprising the particulate water-absorbing agent composition according to claim 5 .

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of International Application No. PCT/JP2024/024366, filed on Jul. 5, 2024, which claims foreign priority to Japanese Patent Application 2023-112533, filed on Jul. 7, 2023, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a particulate water-absorbing agent composition production method, a particulate water-absorbing agent composition, and an absorbent article. BACKGROUND A particulate water-absorbing agent composition (hereinafter, in the present specification, it may be simply referred to as “water-absorbing agent”) containing a water-absorbent resin as a main component is used for absorbers contained in absorbent articles such as disposable diapers, sanitary napkins, and incontinence pads. In the applications described above, the water-absorbing agent absorbs an aqueous liquid such as urine and swells to seal the aqueous liquid. Since the absorbent article is normally used in a state in which a weight is applied, the absorbent article is required to include a water-absorbing agent having high water-absorbing performance under pressure to improve the absorption performance of the absorbent article. Examples of a physical property value representing the water-absorbing performance under pressure of the water-absorbing agent include AAP (absorption against pressure) and FHA (fixed height absorption at a height of 20 cm). Further, from the viewpoint of the handleability of the water-absorbing agent in the production of the absorbent article, the water-absorbing agent is also required to have high caking resistance performance. Physical properties indicating the caking resistance performance include B. R. (moisture absorption blocking ratio). As a method for reducing B. R., that is, improving caking resistance performance, a technique of adding inorganic fine particles such as silicon dioxide, kaolin, or alumina as an anti-caking agent with respect to the surface of a water-absorbent resin is known (JP 2002-523526 T, JP 2001-137704 A, JP S59-080459 A, JP 2009-510177 T, JP 2000-093792 A, JP H11-286611 A, and JP 2017-509757 T). As an anti-caking agent other than inorganic fine particles, a technique of adding a polyvalent metal salt of an organic acid (JP 2004-261796 A), various surfactants, or a hydrophobic polymer such as polysiloxane (JP 2004-512165 T, WO 95/033558, and JP 2003-082250 A) to the surface of a water-absorbent resin is also known. A water-absorbent resin is generally obtained through polymerization, drying, and surface crosslinking after drying, and it is known that various surface modifiers are added during or after the surface crosslinking (Modern Superabsorbent Polymer Technology (1998) pp. 69 to 103). Among these surface modifiers, the inorganic fine particles are widely used not only as an anti-caking agent but also for the purpose of improving physical properties such as liquid permeability and gel strength of a water-absorbent resin (JP H06-016822 A, WO 2002/005949, JP 2003-225565 A, JP 2005-095759 A, WO 2008/015980, and JP 2010-521577 T). SUMMARY However, the known surface modification technique described above has room for improvement in terms of providing a water-absorbing agent having high caking resistance performance without deteriorating water-absorbing performance under pressure. An object of one aspect of the present disclosure is to provide a method for producing a water-absorbing agent having high caking resistance performance without deteriorating water-absorbing performance under pressure, a water-absorbing agent, and an absorbent article. To solve the above problem, one aspect of the present disclosure includes the following configurations. [1]A method for producing a particulate water-absorbing agent composition containing a poly(meth)acrylic acid (salt)-based water-absorbent resin, the method including: a monomer aqueous solution preparation step of preparing a (meth)acrylic acid (salt)-based monomer aqueous solution;a polymerization step of polymerizing the (meth)acrylic acid (salt)-based monomer aqueous solution;as an optional step, a hydrogel grinding step of subjecting a resulting crosslinked hydrogel polymer to gel grinding during polymerization or after polymerization;a drying step of drying a particulate hydrogel;as optional steps, a pulverizing step and a classification step of pulverizing and classifying a dried polymer; anda surface crosslinking step of performing surface crosslinking on a water-absorbent resin before surface crosslinking,in whichthe particulate hydrogel is obtained through the polymerization step or both the polymerization step and the hydrogel grinding step,the dried polymer is obtained through the drying step,the water-absorbent resin before surface crosslinking is the dried polymer or a water-absorbent resin obtained by pulverizing and/or classifying the dried polymer,at least one step selected from the