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. An absorbent article comprising an absorbent structure, the absorbent structure comprising a particulate super-absorbent material, the super-absorbent material comprising a plurality of particulate cores, the particulate cores comprising super-absorbent polymers, wherein a plurality of the particulate cores are coated with a coating agent, the coating agent comprising an organic coating compound comprising one or more polar groups, and 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, wherein the coating agent is in the form of particles, wherein the coating agent particles have a mean particle size from about 0.001 microns to about 1 micron, and wherein the coated particulate cores reduce surface tension of water by less than about 10%.
2. The absorbent article of claim 1 wherein the absorbent structure further comprises cellulose fibers.
3. The absorbent article of claim 1 wherein the absorbent article is selected from the group consisting of a sanitary napkin, a panty liner, a diaper, a training pant, and an adult incontinence article.
4. The absorbent article of claim 1 wherein the absorbent structure comprises at least a first area and a second area, wherein each of the first and second areas comprise the super-absorbent material, wherein the super-absorbent material within the first area is different from the super-absorbent material in the second area.
5. The absorbent article of claim 1 , wherein the plurality of coated particulate cores have a surface area of at least about 0.01 m 2 gram.
6. The absorbent article of claim 5 , wherein the plurality of particulate cores have a mean particle size from about 45 to about 850 microns.
7. The absorbent article of claim 6 , wherein the organic coating compound makes up at least about 85% by weight of the coating agent.
8. The absorbent article of claim 5 , wherein the plurality of particulate cores have a mean particle size from about 250 to about 450 microns.
9. The absorbent article of claim 1 , wherein the plurality of coated particulate cores have a surface area of at least about 0.25 m 2 gram.
10. The absorbent article of claim 1 , wherein the organic coating compound makes up at least about 60% by weight of the coating agent.
11. The absorbent article of claim 1 , wherein the coating agent coats the particulate cores in a substantially permanent manner.
12. The absorbent article of claim 1 , wherein the coating agent reduces a surface tension of the super-absorbent material by less than about 5%.
13. The absorbent article of claim 1 , wherein the coating agent generally does nor reduce a surface tension of the super-absorbent material.
14. The absorbent article of claim 1 , wherein none of the coating agent particles are more than about 50 microns.
15. The absorbent article of claim 1 , wherein one or more of the polar groups have a molecular weight less than about 500 mol.
16. The absorbent article of claim 15 , wherein the coating agent comprises at least one cationic polar group and at least one anionic polar group.
17. The absorbent article of claim 1 , wherein the coating agent is applied to the plurality of particulate cores via dry mixing.
18. The absorbent article of claim 17 , wherein the coating agent is mixed with the plurality of particulate cores for at least about 30 minutes.
19. The absorbent article of claim 1 , wherein the coating agent compounds selected from the group consisting of N-(2-Acetamido)-2-aminoethansulfonic-acid, N-(2-Acetamido)-imino-di-acetic-acid, N-acetyl-glycin, β-Alanine, Aluminum-hydroxy-acetate, N-Amidino-glycine, 2-Amino-ethyl-hydrogenphosphate, 2-Amino-ethyl-hydrogensulfate, Amino-methan-sulfonic-acid, Maleinic-acid, Arginine, Asparaginic-acid, Butane-di-acid, Bis(1-aminoguanidinium)-sulfate, 2-Oxo-propionic-acid, Tri-Calcium-di-citrate, Calciumgluconate, Calcium-saccharate, Calcium-Titriplex®, Carnitine, Cellobiose, Citrulline, Creatine, Dimethylaminoacetic acid, Than-1,2-disulfonic-acid, Ethylendiammoniumsulfate, Fructose, Fumaric-acid, Galactose, Glucosamine, Gluconic-acid, Glutamine, 2-Amino-glutaric-acid, Glutaric-acid, Glycine, Glycylglycine, Imino-di-acetic-acid, Magnesium-glycerophosphate, Oxalicacid, Tetrahydroxy-adipinic-acid, Taurine, N-Methyl-taurin, Tris-(hydroxymethyl)-aminomethane, and N-(Tris-(hydroxymethyl)-methyl)-2-aminoethansulfonicacid.
20. The absorbent article of claim 1 , wherein the organic coating compound further comprises an oxygen atom bound to a hydrogen atom.
21. The absorbent article of claim 1 , wherein the organic coating compound is an organic derivates of an oxo acid, or salt or ester thereof.
22. The absorbent article of claim 1 , wherein the organic coating compound has from 2 to 9 carbon atoms.