High permeability superabsorbent polymer compositions
View Patent ↗The invention relates to absorptive, crosslinked polymeric composition that are based on partly neutralized, monoethylenically unsaturated monomer carrying acid groups wherein the absorptive crosslinked polymer may be coated with a polymeric coating, and have improved properties, in particular in respect of their capacity for transportation of liquids in the swollen state, and which have a high capacity and a high gel bed permeability.
1. A high-capacity superabsorbent polymer composition comprising a superabsorbent polymer comprising:
a) from about 55% to about 99.9% by weight of polymerizable unsaturated acid group containing monomer, based on the superabsorbent polymer; and
b) from about 0.001% to about 5% by weight of internal crosslinking agent based on the polymerizable unsaturated acid group containing monomer; wherein the superabsorbent polymer has a degree of neutralization of greater than about 25%; wherein elements a) and b) are polymerized and prepared into superabsorbent polymer particles and further comprising the following surface additives to form surface treated superabsorbent polymer particles treated with i) from about 0.01 to about 2% by weight of an inorganic metal compound, wherein said inorganic metal compound is selected from calcium phosphate, aluminum phosphate, or iron phosphate, based on the dry superabsorbent polymer composition, and ii) from about 0.01% to about 0.5% by weight of cationic polymer based on the superabsorbent polymer composition and iii) from about 0.01% to about 0.5% of a thermoplastic polymer that is selected from polyolefin, polyethylene, linear low density polyethylene, ethylene acrylic acid copolymer, styrene copolymers, ethylene alkyl methacrylate copolymer, polypropylene, maleated polypropylene, ethylene vinyl acetate copolymer, polyamide, polyester, blends thereof, or copolymers thereof wherein the superabsorbent polymer composition exhibits a free swell gel bed permeability of from 10 Darcy to about 47 Darcy as measured by the Free Swell Gel Bed Permeability Test.
2. The high-capacity superabsorbent polymer composition according to claim 1 wherein the particles of inorganic metal compound have a median particle size of less than 2 μm.
3. The high-capacity superabsorbent polymer composition of claim 1 having a centrifuge retention capacity of at least about 32 g/g as measured by the Centrifuge Retention Capacity Test.
4. The high-capacity superabsorbent polymer composition of claim 1 wherein at least about 40% by weight of the dry superabsorbent polymer particles surface treated have a particle size from about 300 μm to about 600 μm.
5. The high-capacity superabsorbent polymer composition according to claim 1 wherein the particles of the water-insoluble inorganic metal compound have a mass median particle size of less than about 1 μm.
6. The high-capacity superabsorbent polymer composition according to claim 1 wherein the surface additives further comprise from about 0.01 wt % of the dry superabsorbent polymer composition of a silica.
7. The high-capacity superabsorbent polymer composition according to claim 1 wherein the surface additives further comprise an anti-caking additive.
8. The high-capacity superabsorbent polymer composition according to claim 1 wherein the surface additives further comprise a flow modification agent.
9. The high-capacity superabsorbent polymer composition according to claim 1 wherein the surface additives further comprise an odor-binding substance.
10. The high-capacity superabsorbent polymer composition according to claim 1 wherein the surface additives further comprise a viscosity modifier.