Permeable superabsorbent and process for production thereof

Patent metadata

Field	Value
Publication number	US-12403448-B2
Application number	US-202017624873-A
Country	US
Kind code	B2
Filing date	Jul 14, 2020
Priority date	Jul 24, 2019
Publication date	Sep 2, 2025
Grant date	Sep 2, 2025

Abstract

A highly permeable superabsorbent is prepared by a process comprising polymerizing an aqueous monomer solution comprising a) at least one ethylenically unsaturated monomer which bears acid groups and is optionally at least partly in salt form, b) at least one crosslinker, c) at least one initiator, d) optionally one or more ethylenically unsaturated monomers copolymerizable with the monomers mentioned under a), and e) optionally one or more water-soluble polymers; drying the resulting polymer, optionally grinding the dried polymer and sieving the ground polymer, optionally surface postcrosslinking the dried and optionally ground and sieved polymer, adding x-ray-amorphous aluminum hydroxide powder after drying, grinding or sieving, and, if surface postcrosslinking is conducted, during or after this surface postcrosslinking, adding 0.1% to 10% by weight, based on the amount of polymer prior to the addition of the x-ray-amorphous aluminum hydroxide powder, of water after the addition of x-ray-amorphous aluminum hydroxide powder, wherein the water is added to the superabsorbent in at least three portions.

First claim

The invention claimed is:

1. A process for producing a superabsorbent, comprising
polymerizing an aqueous monomer solution comprising:
a) at least one ethylenically unsaturated monomer which bears an acid group and is optionally at least partly in salt form,
b) at least one crosslinker,
c) at least one initiator,
d) optionally one or more ethylenically unsaturated monomer copolymerizable with the monomer mentioned under a), and
e) optionally one or more water-soluble polymer;
drying a resulting polymer,
adding x-ray-amorphous aluminum hydroxide powder after drying, and
adding 0.1% to 10% by weight, based on the amount of polymer prior to the addition of the x-ray-amorphous aluminum hydroxide powder, of water after the addition of x-ray-amorphous aluminum hydroxide powder to produce the superabsorbent,
wherein the water is added to the polymer in at least three portions such that the gel bed permeability of the superabsorbent obtained is greater than the gel bed permeability of the same superabsorbent obtained by adding the water to the polymer all at once or in two portions.

2. The process according to claim 1 , wherein a second and any consecutive portions of water are added after a time of at least 1 second following the addition of a previous portion.

3. The process according to claim 1 , wherein 0.01% to 1% by weight, based on the amount of polymer, of x-ray-amorphous aluminum hydroxide is added.

4. The process according to claim 3 , wherein 0.1% to 0.5% by weight, based on the amount of polymer, of x-ray-amorphous aluminum hydroxide is added.

5. The process according to claim 1 , wherein the dried polymer is surface postcrosslinked with a postcrosslinker that forms covalent bonds with polar groups at the surface of the superabsorbent and the x-ray-amorphous aluminum hydroxide powder is added during or after surface postcrosslinking.

6. The process according to claim 1 , further comprising grinding the dried polymer and sieving the ground polymer.

7. The process according to claim 6 , further comprising surface postcrosslinking the dried, ground and sieved polymer and adding said x-ray-amorphous aluminum hydroxide powder during or after surface postcrosslinking.

8. The process according to claim 7 , wherein the dried, ground and sieved polymer is surface postcrosslinked with a postcrosslinker that forms covalent bonds with polar groups at the surface of the superabsorbent.

9. The process according to claim 1 , wherein the water is added to the polymer in at least four portions such that the gel bed permeability of the superabsorbent obtained is greater than the gel bed permeability of the same superabsorbent obtained by adding the water to the polymer all at once or in two portions.

10. A superabsorbent obtained by the process of claim 1 .

11. An article for absorption of fluids, comprising a superabsorbent obtained by the process of claim 1 .

12. A process for producing an article for absorption of fluid, comprising addition of a superabsorbent obtained by the process of claim 1 .

Assignees

• Basf Se

Inventors

• Bauduin Christophe

Classifications

• C08L33/02

  Homopolymers or copolymers of acids; Metal or ammonium salts thereof · CPC title

• C08F220/06 Primary

  Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof · CPC title

• B01J20/3085

  Chemical treatments not covered by groups B01J20/3007 - B01J20/3078 · CPC title

• B01J20/3021

  Milling, crushing or grinding · CPC title

• C08J2333/02

  Homopolymers or copolymers of acids; Metal or ammonium salts thereof · CPC title