Superabsorbent Polymer Particles Having a Reduced Amount of Fine-Sized Particles, and Methods of Manufacturing the Same

[0099]

Base SAP particles: CRC = 40 g / gPSD: >850 μm:0.1%500-850 μm:33.8% 300-500 μm:32.6% 150-300 μm:26.5% 106-150 μm:5.7% 45-106 μm:1.3% 0.0%.The SAP particles1) (40 kg) were coated with 2 kg ofdeionized water, 2 kg of propylene glycol, 0.025 kgof polymer2), and 0.04 kg of ethylene glycol digly-cidyl ether (EGDGE). The SAP particles then werecured at 120° C. for 60 minutes.Finished product performance: CRC = 30.3 g / gPSD: >850 μm:0.3%500-850 μm:36.0% 300-500 μm:32.8% 150-300 μm:25.8% 106-150 μm:4.1% 45-106 μm:1.0%0.0%

1)The SAP particles were a crosslinked polyacrylic acid having a 75% neutralization; and

2)Added as an emulsion containing 50.5%, by weight of a methyl methacrylate / butyl acrylate copolymer, to provide 0.025 kg of the polymer.

[0103] To polyacrylic acid SAP particles (DN=75) was added 4.2% (by weight, based on the weight of the SAP particles) of a mixture of a 1 / 1 ratio of deionized (DI) water and propylene glycol that further contained 0.1% Polymer 1 latex. The mixture was applied by spraying onto 1,000 grams of SAP particles fluidized in a Lodige mixer. After applying Polymer 1, the SAP particles were heated to 120° C. and held for one hour. The initial SAP particles polymer had a 106 micron and smaller particle content of 20%. After application of Polymer 1, the particle distribution was measured and found to have 0% of particles having a size less than 106 micron. The CRC of the coated SAP particles was 32.7 g / g and the SAUL was 62 (0.01 AUL=50 g / g and 0.9 AUL=12 g / g). Target properties of SAP particles without added Polymer 1 are 30 g / g CRC and 64 SAUL. The finished product whiteness was 36.

[0104] To polyacrylic acid SAP particles (DN=75) was added 4.2% (by weight based on the weight of the SAP particles) of a mixture of a 1 / 1 ratio of DI water and propylene glycol that further contained 0.1% EGDGE, 0.05% Polymer 1, and 1% of kaolin clay. The mixture first was sheared in a Waring Blender at the “high speed” condition for three minutes to disperse Polymer 1 more uniformly. The mixture then was applied by spraying onto 1,000 grams of SAP particles that were fluidized in a Lodige mixer. After applying the mixture, the SAP particles were heated to 120° C. and held for one hour. After application of the polymer / kaolin clay coating, the mean PSD was measured and determined to be 43% higher than the control (330 μm versus 281 μm) indicating a shift in the particle distribution (PSD) towards the coarse end and a reduction of the amount of fine-sized SAP particles.