Granted Patent B2

US 7,300,973 · App. 10/251,006 · Granted Nov 27, 2007

Abstract

Claims (18)

1. A composition comprising a water-in-oil emulsion of highly cross linked expandable polymeric microparticles having an unexpanded volume average particle size diameter of from about 0.05 to about 10 microns and a cross linking agent content of about 6,000 to less than about 9,000 ppm of labile cross linkers and from 0 to about 300 ppm of non-labile cross linkers wherein said polymeric microparticle remains in an unexpanded state until expansion of the microparticle is triggered by heat, change in pH or a combination thereof.

2. The composition of claim 1 wherein the unexpanded volume average particle size diameter is from about 0.1 to about 3 microns.

3. The composition of claim 1 wherein the unexpanded volume average particle size diameter is from about 0.1 to about 1 microns.

4. The composition of claim 1 wherein the labile cross linker is selected from diacrylates and polyfunctional vinyl derivatives of a polyalcohol.

5. The composition of claim 1 wherein the polymeric microparticles are selected from the group consisting of cationic, anionic, amphoteric, ion-pair and betaine-containing polymeric microparticles.

6. The composition of claim 5 wherein the cross linked polymeric microparticle is anionic.

7. The composition of claim 6 wherein the polymeric microparticle comprises from about 95 to about 10 mole percent of nomonic monomers and from about 5 to about 90 mole percent anionic monomers.

8. The composition of claim 7 wherein the nonionic monomer is acrylamide.

9. The composition of claim 8 wherein the anionic monomer is 2-acrylamido-2-methyl-1-propanesulfonic acid.

10. The composition of claim 9 wherein the labile cross linker is polyethyleneglycol diacrylate.

11. The composition of claim 10 wherein the non-labile cross linker is methylene bisacrylamide.

12. A method of preparing a water-in-oil emulsion comprising highly cross linked expandable polymeric microparticles having an unexpanded volume average particle size diameter of from about 0.05 to about 10 microns comprising adding an aqueous monomer solution comprising one or more allylic, vinylic or acrylic monomers, about 6,000 to less than about 9,000 ppm of labile cross linkers and 0 to about 300 ppm of non-labile cross linkers to a hydrocarbon liquid containing a surfactant or surfactant mixture to form an inverse monomer microemulsion comprising small aqueous droplets dispersed in the continuous hydrocarbon liquid and subjecting the monomer microemulsion to free radical polymerization, wherein said polymeric microparticle remains in an unexpanded state until expansion of the microparticle is triggered by heat, change in pH or a combination thereof.

13. A method of preparing highly cross linked expandable polymeric microparticles having an unexpanded volume average particle size diameter of from about 0.05 to about 10 microns in dry form comprising

(a) adding a water-in-oil emulsion prepared according to the method of claim 12 to a solvent which precipitates the polymeric microparticles; and

(b) filtering and drying the precipitated polymeric microparticles, wherein said polymeric microparticle remains in an unexpanded state until expansion of the microparticle is triggered by heat, change in pH or a combination thereof.

14. Highly cross linked expandable polymeric microparticles prepared according to the method of claim 13 .

15. A method of preparing an aqueous suspension of highly cross linked expandable polymeric microparticles having an unexpanded volume average particle size diameter of from about 0.05 to about 10 microns comprising suspending precipitated polymeric microparticles prepared according to the method of claim 13 in water.

16. An aqueous suspension of highly cross linked expandable polymeric microparticles prepared according to the method of claim 15 .

Assignments (16)