Method for producing water-absorbent polymer particles with a higher permeability by polymerising droplets of a monomer solution

Patent metadata

Field	Value
Publication number	US-10208149-B2
Application number	US-201615299922-A
Country	US
Kind code	B2
Filing date	Oct 21, 2016
Priority date	Jul 19, 2006
Publication date	Feb 19, 2019
Grant date	Feb 19, 2019

Abstract

A process for preparing water-absorbing polymer beads with high permeability by polymerizing droplets of a monomer solution, comprising monomers bearing acid groups, in a gas phase surrounding the droplets, wherein the monomer solution comprises polyvalent cations and the polymer beads have a mean diameter of at least 150 μm.

First claim

The invention claimed is:

1. A process for preparing water-absorbing polymer beads comprising polymerizing droplets of a monomer solution comprising
a) at least one ethylenically unsaturated monomer bearing acid groups,
b) at least one crosslinker,
c) at least one initiator, and
d) water,
in a gas phase surrounding each of the individual droplets, wherein the monomer solution comprises polyvalent cations and the polymer beads have a mean diameter of at least 150 μm.

2. The process according to claim 1 , wherein the monomer solution comprises from 0.001 to 0.25% by weight of polyvalent cations, based on monomer a).

3. The process according to claim 1 , wherein the polyvalent cation is at least trivalent.

4. The process according to claim 1 , wherein monomer a) is acrylic acid to an extent of at least 50 mol %.

5. The process according to claim 1 , wherein the polymer beads have a mean diameter of at least 200 μm.

6. The process according to claim 1 , wherein at least 90% by weight of the polymer beads have a diameter of from 100 to 800 μm.

7. The process according to claim 1 , wherein a carrier gas flows through a reaction chamber.

8. The process according to claim 7 , wherein the carrier gas leaving the reaction chamber is recycled at least partly after one pass.

9. The process according to claim 7 , wherein an oxygen content of the carrier gas is from 0.001 to 0.15% by volume.

10. The process according to claim 1 , wherein the polymer beads are dried and/or postcrosslinked in at least one further process step.

11. The process according to claim 1 , wherein the acid groups of the ethylenically unsaturated monomer are at least party neutralized.

12. The process according to claim 1 , wherein the ethylenically unsaturated monomer is acrylic acid to an extent of at least 50 mol %.

13. The process according to claim 1 wherein the water-absorbing polymer beads have a mean sphericity of at least 0.84, a content of hydrophobic solvents of less than 0.005%, by weight, and a permeability of at least 5×10 −7 cm 3 s/g.

14. The process according to claim 1 wherein the content of the hydrophobic solvents in the water-absorbing beads is less than 0.005%, by weight.

15. The process according to claim 1 wherein the water-absorbing beads are essentially free of the hydrophobic solvents.

16. The process according to claim 1 wherein the water-absorbing beads are free of the hydrophobic solvents.

17. The process according to claim 1 , wherein the water-absorbing beads have a permeability of at least 15×10 −7 cm 3 s/g.

18. The process according to claim 1 wherein the water-absorbing beads have a mean sphericity of at least 0.86.

19. The process according to claim 1 wherein the water-absorbing beads have a mean sphericity of at least 0.88.

20. The process according to claim 1 wherein the water-absorbing beads have a mean sphericity of at least 0.9.

Assignees

• Basf Se

Inventors

• Stueven Uwe
• Weismantel Matthias
• Heide Wilfried
• Krüger Marco
• Seidl Volker
• Blei Stefan
• Loesch Dennis
• Funk Rüdiger
• Hillebrecht Annemarie

Classifications

• C08F2500/24

  Polymer with special particle form or size · CPC title

• C08F2/34

  Polymerisation in gaseous state · CPC title

• C08F222/385

  Monomers containing two or more (meth)acrylamide groups, e.g. N,N'-methylenebisacrylamide · CPC title

• Y10T428/2982

  Particulate matter [e.g., sphere, flake, etc.] · CPC title

• C08F220/06

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