Search

EP-4741446-A1 - PARTICLE-LIKE WATER-ABSORBING AGENT COMPOSITION PRODUCTION METHOD, PARTICLE-LIKE WATER-ABSORBING AGENT COMPOSITION, AND ABSORBENT ARTICLE

EP4741446A1EP 4741446 A1EP4741446 A1EP 4741446A1EP-4741446-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

  • TAKEDA, DAISUKE
  • OGURA, Tadayuki
  • UEDA, MANABU

Assignees

  • Nippon Shokubai Co., Ltd.

Dates

Publication Date
20260513
Application Date
20240705

Claims (13)

  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. 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. 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. 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. 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, the particulate water-absorbing agent composition having a mass proportion of particles having a particle diameter of 300 µm or more and less than 850 µm of 50 mass% or more, the particulate water-absorbing agent composition satisfying 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. The particulate water-absorbing agent composition according to claim 5, the particulate water-absorbing agent composition having a surface tension of 45 mN/m or more.
  7. The particulate water-absorbing agent composition according to claim 5, the particulate water-absorbing agent composition having an absorption against pressure (AAP) of 20 g/g or more under pressure of 0.7 psi.
  8. The particulate water-absorbing agent composition according to claim 5, the particulate water-absorbing agent composition having a fixed height absorption (FHA) at a height of 20 cm of 20 g/g or more.
  9. The particulate water-absorbing agent composition according to claim 5, the particulate water-absorbing agent composition having a CRC of 25 g/g or more.
  10. The particulate water-absorbing agent composition according to claim 5, the particulate water-absorbing agent composition having a moisture absorption blocking ratio <1> (B. R. <1>) of 80 mass% or less.
  11. The particulate water-absorbing agent composition according to claim 5, the particulate water-absorbing agent composition having a mass-average particle diameter (D50) of 300 µm or more and 600 µm or less.
  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. An absorbent article comprising a particulate water-absorbing agent composition, as the particulate water-absorbing agent composition, the absorbent article comprising the particulate water-absorbing agent composition described in any one of claims 5 to 12.

Description

Technical Field The present invention relates to a particulate water-absorbing agent composition production method, a particulate water-absorbing agent composition, and an absorbent article. Background Art 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 (Patent Documents 1 to 7). As an anti-caking agent other than inorganic fine particles, a technique of adding a polyvalent metal salt of an organic acid (Patent Document 8), various surfactants, or a hydrophobic polymer such as polysiloxane (Patent Documents 9 to 11) 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 (Non-Patent Literature 1). 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 (Patent Documents 12 to 17). Citation List Patent Document Patent Document 1: JP 2002-523526 TPatent Document 2: JP 2001-137704 APatent Document 3: JP S59-080459 APatent Document 4: JP 2009-510177 TPatent Document 5: JP 2000-093792 APatent Document 6: JP H11-286611 APatent Document 7: JP 2017-509757 TPatent Document 8: JP 2004-261796 APatent Document 9: JP 2004-512165 TPatent Document 10: WO 95/033558Patent Document 11: JP 2003-082250 APatent Document 12: JP H06-016822 APatent Document 13: WO 2002/005949Patent Document 14: JP 2003-225565 APatent Document 15: JP 2005-095759 APatent Document 16: WO 2008/015980Patent Document 17: JP 2010-521577 T Non-Patent Literature Non-Patent Literature 1: Modern Superabsorbent Polymer Technology (1998) pp. 69 to 103 Summary of Invention Technical Problem 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 invention 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. Solution to Problem To solve the above problem, one aspect of the present invention 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