High permeability superabsorbent polymer compositions
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
i) from about 0.001% to about 5% by weight of surface crosslinking agent based on the superabsorbent polymer composition;
ii) from about 0.01% to about 2% by weight of a water-insoluble inorganic metal compound, based on the superabsorbent polymer composition wherein said water-insoluble inorganic metal compound is selected from a calcium phosphate, titanium phosphate, aluminum phosphate, iron phosphate, titanium borate, aluminum borate, iron borate magnesium borate, manganese borate, or calcium borate;
iii) from about 0.01% to about 0.5% cationic polymer based on the superabsorbent polymer composition; and
iv) 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.
2. The high-capacity superabsorbent polymer composition according to claim 1 wherein the superabsorbent polymer composition exhibits a centrifuge retention capacity as measured by the Centrifuge Retention Capacity Test of at least about 30 g/g and a free swell gel bed permeability of at least about 10 Darcy as measured by the Free Swell Gel Bed Permeability Test.
3. 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 2 μm.
4. The high-capacity superabsorbent polymer composition of claim 1 wherein the cationic polymer is a polyvinylamine.
5. 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, and a free swell gel bed permeability of at least about 20 Darcy as measured by the Free Swell Gel Bed Permeability Test.
6. The high-capacity superabsorbent polymer composition of claim 1 wherein the thermoplastic polymer is a maleated polypropylene.
7. The high-capacity superabsorbent polymer composition of claim 1 having a centrifuge retention capacity from about 32 g/g to about 40 g/g as measured by the Centrifuge Retention Capacity Test, and a free swell gel bed permeability of at least about 40 Darcy as measured by the Free Swell Gel Bed Permeability Test.
8. The high-capacity superabsorbent polymer composition of claim 1 wherein at least about 40% by weight of the surface treated superabsorbent polymer particles have a particle size from about 300 μm to about 600 μm.
9. The high-capacity superabsorbent polymer composition of claim 1 wherein at least about 50% by weight of the surface treated superabsorbent polymer particles have a particle size from about 300 μm to about 600 μm.
10. The high-capacity superabsorbent polymer composition according to claim 1 wherein the surface treated superabsorbent polymer particles are heat-treated.
11. 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.