Absorbent structures comprising coated super-absorbent polymer particles
This invention is directed to super-absorbent material, which comprises a super absorbent polymer core that is coated with an organic, polar coating agent, and whereby the particulate super-absorbent material has a contact angle and a corresponding cos CA m (as defined herein), whereby the cos CA m is more than 0.3, and whereby, when said coating agent is in the form of particles, said coating agent particles have a (weight) mean particle size of from 0.001 to 1 micron. The material is useful for absorbent structures and absorbent articles (comprising such structures). The coated super-absorbent material is typically present in said absorbent structure at least at a concentration of 50% by weight of the structure, preferably even 80% or even 90%. The invention also provides a process for making the absorbent material.
1. A particulate super-absorbent material comprising a particulate core of super-absorbent polymers, said particulate core coated with a coating agent consisting essentially of an organic coating compound having from 2 to 14 carbon atoms which has one or more polar groups, wherein the particulate super-absorbent material has a contact angle and a corresponding cos CA m , wherein the cos CA m is greater than 0.3 and wherein said coating agent is the form of particles, said particles having a mean particle size of from 0.001 to 1 micron.
2. The particulate super-absorbent material according to claim 1 wherein said particulate core of super-absorbent polymer, before being coated with said coating agent, has a contact angle CA p and a cos CA p and the particulate super-absorbent material has a contact angle CA m and a cos CA m , wherein the ratio cos CA m /cos CA p is at least 1.5.
3. The particulate super-absorbent material according to claim 1 wherein said coating agent comprises an organic material having from 2 to 9 carbon atoms.
4. The particulate super-absorbent material according to claim 1 wherein said polar groups are selected from the group consisting of a hydroxyl group, a carboxylic acid polar group, sulphonic acid polar group, a phosphoric acid polar group, and combinations thereof.
5. The particulate super-absorbent material according to claim 1 wherein said particulate core of super-absorbent polymers has a mean particle size from 200 to 500 microns.
6. The particulate super-absorbent material according to claim 1 wherein at least part of said super-absorbent polymers are cross-linked to one another.
7. The particulate super-absorbent material according to claim 1 wherein said super-absorbent polymers are selected from the group consisting of water-swelling polyacrylates and derivatives, gelling polyacrylates and derivatives, and combinations thereof.
8. The particulate super-absorbent material according to claim 1 wherein the coating agent comprises an organic compound having a molecular weight of less than 500 g/mol.
9. The particulate super-absorbent material according to claim 1 wherein said particulate super-absorbent material comprises from 0.05% to 3%, by weight, of the coating agent.
10. The particulate super-absorbent material according to claim 1 , wherein said particulate super-absorbent material exhibits a 20 cm FHA value of at least 20g/g.
11. The particulate super-absorbent material according to claim 1 , wherein said super-absorbent material has a FHA coated (20 cm), wherein said super-absorbent polymer has a FHA uncoated (20 cm), and wherein a ratio of FHA coated (20 cm) to FHA uncoated (20 cm) is at least about 1.05.
12. A particulate super-absorbent material comprising a particulate core of super-absorbent polymers, said particulate core coated with a coating agent consisting essentially of an organic coating compound having from 2 to 14 carbon atoms which has one or more polar groups, wherein said coating agent of said particulate super-absorbent material provides a surface tension reduction of less than 10% and wherein said coating agent is in the form of particles having weight mean particle size of from 0.001 to 1 micron.