Method for the agglomeration of superabsorber particles

Patent metadata

Field	Value
Publication number	US-10835634-B2
Application number	US-201615564212-A
Country	US
Kind code	B2
Filing date	Mar 24, 2016
Priority date	Apr 7, 2015
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

A process for agglomerating superabsorbent particles, wherein polymer particles having a particle size of 250 μm or less are dispersed in a hydrophobic organic solvent, the dispersed polymer particles are mixed with an aqueous monomer solution, the total amount of water applied to the dispersed polymer particles being at least 100% by weight, based on the dispersed polymer particles, and the monomer solution is polymerized.

First claim

The invention claimed is:

1. A process for agglomerating superabsorbent particles comprising (A) polymerizing a first aqueous monomer solution comprising
a) at least one ethylenically unsaturated monomer which bears an acid group and optionally at least partly neutralized,
b) optionally one or more 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 to provide polymer particles,
optionally drying and/or comminuting the polymer particles, removing polymer particles having a particle size of 250 μm or less,
dispersing the polymer particles having a particle size of 250 μm or less in a hydrophobic organic solvent,
mixing the dispersed polymer particles with a second aqueous monomer solution comprising
a) at least one ethylenically unsaturated monomer which bears an acid group and optionally at least partly neutralized,
b) optionally one or more 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,
wherein the first aqueous monomer solution and the second aqueous monomer solution may be the same or different and a total amount of water applied to the dispersed polymer particles with the second aqueous monomer solution being at least 100% by weight, based on the dispersed polymer particles, and
polymerizing the second aqueous monomer solution to provide agglomerated particle superabsorbent.

2. The process according to claim 1 , wherein polymer particles having a particle size of 200 μm or less are removed and dispersed in the hydrophobic organic solvent.

3. The process according to claim 1 , wherein polymer particles having a particle size of 150 μm or less are removed and dispersed in the hydrophobic organic solvent.

4. The process according to claim 1 , wherein the amount of water applied with the second monomer solution is at least 150% by weight, based on the dispersed polymer particles.

5. The process according to claim 1 , wherein the amount of water applied with the second monomer solution is at least 175% by weight, based on the dispersed polymer particles.

6. The process according to claim 1 , wherein the second monomer solution comprises from 0.01 to 0.50 mmol of crosslinker b), based on 1 mol of monomer a).

7. The process according to claim 1 , wherein the second monomer solution comprises from 0.02 to 0.25 mmol of crosslinker b), based on 1 mol of monomer a).

8. The process according to claim 1 , wherein the second monomer solution comprises from 0.05 to 0.15 mmol of crosslinker b), based on 1 mol of monomer a).

9. The process according to claim 1 , wherein the first monomer solution is polymerized by dropletizing polymerization.

10. The process according to claim 9 , wherein the polymer particles are removed from an offgas of the dropletizing polymerization by means of a filter or cyclone.

11. The process according to claim 1 , wherein the first monomer solution is polymerized by suspension polymerization and the resulting polymer particles are dried.

12. The process according to claim 1 , wherein the first monomer solution is polymerized by solution polymerization and the resulting polymer particles are dried and comminuted.

13. The process according to claim 11 , wherein the polymer particles are removed by means of a sieve having a mesh size of 250 μm or less.

14. The process according to claim 11 , wherein the polymer particles are removed by means of a sieve having a mesh size of 200 μm or less.

15. The process according to claim 11 , wherein the polymer particles are removed by means of a sieve having a mesh size of 150 μm or less.

16. The process according to claim 12 , wherein the polymer particles are removed by means of a sieve having a mesh size of 250 μm or less.

17. The process according to claim 12 , wherein the polymer particles are removed by means of a sieve having a mesh size of 200 μm or less.

18. The process according to claim 12 , wherein the polymer particles are removed by means of a sieve having a mesh size of 150 μm or less.

19. A process for agglomerating superabsorbent particles comprising:
(a) providing superabsorbent particles having a particle size of 250 μm or less;
(b) dispersing superabsorbent particles in a hydrophobic organic solvent;
(c) mixing the dispersed superabsorbent particles with an aqueous monomer solution comprising:
i) at least one ethylenically unsaturated monomer which bears an acid group and optionally at least partly neutralized,
ii) optionally one or more crosslinker,
iii) at least one initiator,
iv) optionally one or more ethylenically unsaturated monomer copolymerizable with the monomer mentioned under i), and
v) optionally one or more water-soluble polymer,

wherein a total amount of water applied to the dispersed superabsorbent particles with the aqueous monomer solution being at least 100% by weight, based on the dispersed polymer superabsorbent particles, and
polymerizing the second monomer solution to provide agglomerated superabsorbent particles.

20. The process of claim 19 comprising providing superabsorbent particles having a particle size of 200 μm or less.

Assignees

• Basf Se

Inventors

• Mark Tina
• Daniel Thomas
• Lutz Erich
• Molter Stefan

Classifications

• C08F265/04

  on to polymers of esters · CPC title

• C08L51/003

  grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds (C08L51/04, C08L51/06 take precedence) · CPC title

• C08F6/18

  Increasing the size of the dispersed particles · CPC title

• C08F265/06

  Polymerisation of acrylate or methacrylate esters on to polymers thereof · CPC title

• C08L101/14

  the macromolecular compounds being water soluble or water swellable, e.g. aqueous gels · CPC title