Method of making high performance superabsorbent material

• US 5,849,816 A
• Filed: 01/31/1996
• Issued: 12/15/1998
• Est. Priority Date: 08/01/1994
• Status: Expired due to Fees

• Current Assignee: Leonard Pearlstein
• Original Assignee: Leonard Pearlstein
• Inventors: Pearlstein, Leonard, Suskind, Stuart P.
• Primary Examiner(s): Weiss, John G.
• Assistant Examiner(s): RUHL, DENNIS WILLIAM
• Application Number:
  US08/593,332
• Time in Patent Office: 1,049 Days
• Field of Search: 523/200-205, 523/209, 428/407
• US Class Current: 523/201
• CPC Class Codes: A61F 13/534 having an inhomogeneous composition through the thickness of the pad A61F13/538, A61F13/539 take precedence; homogeneous cores with tissue wrapping A61F13/53
• CPC Class Codes: A61F 2013/15463 Absorbency
• CPC Class Codes: A61F 2013/530489 being randomly mixed in with other material
• CPC Class Codes: A61F 2013/530547 positioned in a separate layer or layers
• CPC Class Codes: A61F 2013/530569 characterized by the particle size
• CPC Class Codes: A61F 2013/530583 characterized by the form
• CPC Class Codes: A61F 2013/5307 characterized by the quantity or ratio of superabsorbent material
• CPC Class Codes: A61F 2013/530766 by the cross-link factor
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: C08F 251/00 Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof
• CPC Class Codes: C08F 292/00 Macromolecular compounds obtained by polymerising monomers on to inorganic materials
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer

Abstract

A high performance absorbent particulate composition and a method of preparation in which a non-colloidal solid filler core is substantially encapsulated within a layer of hydrogel forming polymer is disclosed. Also disclosed are absorbent devices using the high performance absorbent particulate composition and methods of making these devices.

Claims

1. A method for preparing a plurality of individual and discrete absorbent particles comprising the steps of:

a) suspending an aqueous solution comprising an ethylenically unsaturated monomer capable of polymerization into a hydrogel forming polymer and an initiator in a water immiscible solvent in the presence of a surface active agent;

b) initiating the polymerization of the ethylenically unsaturated monomer while suspended in said water immiscible solvent; and

c) co-suspending water resistant solid core particles in said water immiscible solvent for a time sufficient to permit the individual and substantial encapsulation of the water resistant solid core particles by said hydrogel forming polymer to form said absorbent particles.

2. The method of claim 1, further comprising the step of removing all or a portion of any water present in said absorbent particles by azeotropic distillation.

3. The method of claim 1, further comprising isolating said absorbent particles formed and removing any water present in said particles by heating.

4. The method of claim 1, further comprising cross-linking the surface of the absorbent particle formed in step c).

5. The method of claim 4, further comprising the step of removing all or a portion of any water present in said absorbent particles by azeotropic distillation.

6. The method of claim 4, further comprising isolating said absorbent particles formed and removing any water present in said particles by heating.

7. The method of claim 1, wherein said hydrogel forming polymer has a coating thickness of from about 2 μ

to about 3000 μ

.

8. The method of claim 7, wherein said coating thickness is from about 10 μ

to about 300 μ

.

9. The method of claim 1, wherein said hydrogel forming polymer has a number average molecular weight of at least about 250,000.

10. The method of claim 1, wherein said solid core particle is a hollow, mineral sphere.

11. The method of claim 1, wherein said co-suspending of said water resistant solid core particles occurs after a reaction exotherm has occurred.

12. The method of claim 1, wherein said surface active agent has an HLB factor of from about 2 to about 12.

13. The method of claim 12, wherein said surface active agent has an HLB value of from about 3 to about 7.

14. The method of claim 1, wherein said surface active agent is a fatty ester of a sugar optionally reacted with ethylene oxide.

15. The method of claim 1, wherein said water immiscible solvent is cyclohexane.

16. The method of claim 1, wherein said ethylenically unsaturated monomer is acrylic acid.

17. The method of claim 1, wherein said ethylenically unsaturated monomer is a partially neutralized acrylate-acrylic acid mixture.

18. The method of claim 1, wherein said initiator is potassium persulfate.

19. The method of claim 1, wherein said solid core particle is an inorganic mineral in particulate form.

20. The method of claim 1, wherein said solid core particle is silicon dioxide, titanium dioxide, magnesium oxide, antimony oxide, clay, talc, wollastonite, synthetic amorphous silica, or calcium carbonate.

21. The method of claim 1, wherein said solid core particle is sand.

22. The method of claim 1, wherein said solid core particle is cereal, wood flour, ground nut shells, cellulose, or gelatin in particulate form.

23. The method of claim 1, wherein said solid core particle is starch in particulate form.

24. The method of claim 1, wherein said solid core particle is silica and has a particle size of from about 50 microns to about 1000 microns.

25. The method of claim 24, wherein said particle size is from about 75 microns to about 500 microns.

26. The method of claim 1, wherein said hydrogel forming polymer has a thickness of from about 40 microns to about 150 microns.

27. The method of claim 1, wherein said water immiscible solvent is heptane.

28. The method of claim 1, wherein each absorbent particle comprises one water-resistant solid core particle with a size of from about 10 microns to about 1500 microns, substantially encapsulated by a composition consisting essentially of said hydrogel forming polymer, wherein said plurality of individual and discrete absorbent particles are in the substantial absence of absorbent particles containing none or more than one water resistant solid core particle.