초록 ▼

This invention is directed to a process for making solid, typically particulate, water-swellable material comprising coated water-swellable, preferably hydrogel-forming polymers, which are coated with a coating agent, which is such that it does not rupture when the polymers swell in a liquid, e.g.,

This invention is directed to a process for making solid, typically particulate, water-swellable material comprising coated water-swellable, preferably hydrogel-forming polymers, which are coated with a coating agent, which is such that it does not rupture when the polymers swell in a liquid, e.g., water or saline water. Hereto, the coating agent is extensible in wet state and comprises thereto a wet-extensible material that has a wet-elongation of at least 400%, or even more preferably at least 500%, and preferably a tensile stress at break in the wet state of at least 1 MPa. Typically, the coating agent comprises thereto an elastomeric polymeric material. The invention also relates to solid (particulate) water-swellable material obtainable by the process of the invention.

대표청구항 ▼

What is claimed is: 1. A process for making a water-swellable material comprising coated water-swellable polymers, the process comprising the steps of: a) obtaining water-swellable polymers; and b) applying a coating agent, said coating agent comprising a material that is wet-extensible and has a w

What is claimed is: 1. A process for making a water-swellable material comprising coated water-swellable polymers, the process comprising the steps of: a) obtaining water-swellable polymers; and b) applying a coating agent, said coating agent comprising a material that is wet-extensible and has a wet-elongation to break of more than 1000%, to at least part of said water-swellable polymers to obtain the water-swellable material comprising the coated water-swellable polymers. 2. A process according to claim 1, wherein the water-swellable polymers of step a) are in particulate form. 3. A process according to claim 1, wherein step (b) is conducted subsequent to step (a). 4. A process according to claim 1, wherein the coating agent has a tensile stress at break in the wet state of at least 1 MPa. 5. A process according to claim 1, wherein the coating agent has, in the wet state, a wet secant elastic modulus at 400% elongation (SMwet400%) of at least 0.5 MPa. 6. A process according to claim 1 wherein the coating agent in step b) is applied in a fluid form, the form being selected from the group consisting of a solution, a dispersion, and a hotmelt. 7. A process according to claim 1, wherein the wet-extensible material has a first glass transition temperature of 20�� C. or less. 8. A process according to claim 1, wherein said process further comprises an annealing step of submitting the resulting coated water-swellable polymers of step b) to a heat treatment at a temperature of at least 70�� C. 9. A process according to claim 1, wherein the water-swellable polymers have a CCRC value of at least 30 g/g. 10. A process according to claim 1, wherein the water-swellable polymers of step a) are liquid-containing and at least partially swollen, comprising said liquid at a level of from 0.5 g/g to about 20 g/g. 11. A water-swellable material comprising coated water-swellable polymers, made by the process of claim 1. 12. A water-swellable material according to claim 11 wherein the coating agent forms a continuous shell around at least some of said water-swellable polymers, said shell having an average caliper of 1 μm to 50 μm. 13. A process for making a water-swellable material comprising coated water-swellable polymers, the process comprising the steps of: a) obtaining water-swellable polymers; b) applying a coating agent, said coating agent comprising a material that is wet-extensible and has a wet-elongation to break of more than 1000%, to at least part of said water-swellable polymers; and c) heat treating the resulting coated water-swellable polymers of step b) to obtain the water-swellable material comprising the coated water-swellable polymers. 14. A process according to claim 13, wherein the water-swellable polymers of step a) are in particulate form. 15. A process according to claim 13, wherein step (b) is conducted subsequent to step (a). 16. A process according to claim 13 comprising wherein said heat treating step involves submitting the coated water-swellable polymers to a temperature of at least 140�� C. for a predetermined time. 17. A water-swellable material comprising coated water-swellable polymers, made by the process of claim 13. 18. A water-swellable material according to claim 17, wherein the coating agent forms a continuous shell around at least some of said water-swellable polymers, said shell having an average caliper of 1 μm to 50 μm. 19. A process for making a water-swellable material, comprising coated water-swellable polymers, the process comprising the steps of: a) obtaining water-swellable polymers comprising less than 15% extractable by weight of the polymers; b) surface crosslinking said water-swellable polymers; and c) applying a non-water-swellable coating agent that is wet-extensible and has a wet-elongation to break of more than 1000%, to at least part of said water-swellable polymers, the coating agent comprising polyurethane to obtain the water-swellable material comprising the coated water-swellable polymers.