Method for Producing Water-Absorbent Polymer Particles with a Higher Permeability by Polymerising Droplets of a Monomer Solution

• US 20090192035A1
• Filed: 07/12/2007
• Published: 07/30/2009
• Est. Priority Date: 07/19/2006
• Status: Active Grant

• Current Assignee: BASF SE
• Original Assignee: BASF SE
• Inventors: Hillebrecht, Annemarie, Stueven, Uwe, Funk, Rüdiger, Weismantel, Matthias, Krüger, Marco, Blei, Stefan, Seidl, Volker, Heide, Wilfried, Lösch, Dennis
• Granted Patent: US 8,748,000 B2
• Time in Patent Office: Days
• US Class Current: 502/402
• CPC Class Codes: A61L 15/24 Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof A61L15/225 takes precedence
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: B01J 10/002 carried out in foam, aerosol or bubbles
• CPC Class Codes: C08F 2/00 Processes of polymerisation
• CPC Class Codes: C08F 2/10 Aqueous solvent
• CPC Class Codes: C08F 2/44 Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers
• CPC Class Codes: C08F 220/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 222/103 of trialcohols, e.g. trimethylolpropane tri(meth)acrylate
• CPC Class Codes: C08L 33/02 Homopolymers or copolymers of acids; Metal or ammonium salts thereof
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2989 Microcapsule with solid core [includes liposome]

Abstract

A process for preparing water-absorbing polymer beads with high permeability by polymerizing droplets of a monomer solution in a gas phase surrounding the droplets, wherein a water-insoluble inorganic salt is suspended in the monomer solution and the polymer beads have a mean diameter of at least 150 μm.

Claims

1. A process for preparing water-absorbing polymer beads comprising polymerizing droplets of a monomer solution comprising

a) at least one ethylenically unsaturated monomer,

b) at least one crosslinker,

c) at least one initiator, and

d) water,

in a gas phase surrounding the droplets, wherein a water-insoluble inorganic salt is suspended in the monomer solution and the polymer beads have a mean diameter of at least 150 um.

2. The process according to claim 1, wherein the monomer a) has at least one acid group.

3. The process according to claim 2, wherein the acid groups of the monomer a) are at least partly neutralized.

4. The process according to any of claims 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 μ

m.

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 ∥

m.

7. The process according to claim 1, wherein a carrier gas flows through the 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. Water-absorbing polymer beads prepared according to the process of claim 1.

22. A hygiene article comprising polymer beads prepared according to the process of claim 1.

12. Water-absorbing polymer beads having 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<sup>−

7</sup> cm³s/g.

13. Polymer beads according to claim 12, having a centrifuge retention capacity of at least 10 g/g.

15. Polymer beads according to claim 12, wherein at least 90%, by weight, of the polymer beads have a diameter of from 100 to 800 μ

m.

16. Polymer beads according to claim 12, comprising at least partly of polymerized ethylenically unsaturated acid-bearing monomers).

17. Polymer beads according to claim 16, wherein the acid groups of the polymerized monomer are at least partly neutralized.

18. Polymer beads according to claim 16, wherein the ethyleneically unsaturated monomer is acrylic acid to an extent of at least 50 mol %.

19. Polymer beads according to claim 12, which comprise water-insoluble inorganic salts.

21. A hygiene article comprising polymer beads according to claim 12.

14. Polymer beads according to claim, having a mean diameter of at least 200 μ

m.

20. (canceled)