Water-swellable crosslinked polymer composition and production

A water-swellable crosslinked polymer composition, which comprises a blend of a water-swellable crosslinked polymer of acidity in water and a water-swellable crosslinked polymer of basicity in water, with the composition being characterized by exhibiting a saltwater absorption capacity of at least 40 g/g under a load of 21 g/cm2 in 10 hours, and absorbing 60% of the 10-hour saltwater absorption capacity under the load of 21 g/cm2 in less than 5 minutes.

A water-swellable crosslinked polymer composition, which comprises a blend of water-swellable crosslinked polymer particles of acidity in water and water-swellable crosslinked polymer particles of basicity in water, with the composition being characterized in that the water-swellable crosslinked polymer particles of acidity in water are unified with the water-swellable crosslinked polymer particles of basicity in water through ionic bondings in a state where water is present between the particles, and further characterized by exhibiting a saltwater absorption capacity of not less than 33 g/g in 60 minutes.

A water-swellable crosslinked polymer composition, which comprises a blend of water-swellable crosslinked polymer particles of acidity in water and water-swellable crosslinked polymer particles of basicity in water, with the composition being characterized in that ionic bondings are formed in a state where water is present between the particles by neutralization of at least part of acid groups of the water-swellable crosslinked polymer particles of acidity in water with the water-swellable crosslinked polymer particles of basicity in water, and further characterized by exhibiting an absorption capacity of not less than 25 g/g under a load.

A water-swellable crosslinked polymer composition, which comprises a blend of a water-swellable crosslinked polymer of acidity in water and a water-swellable crosslinked polymer of basicity in water, with the composition being characterized in that the water-swellable crosslinked polymer of acidity in water is a crosslinked polyacrylic acid, and in that the water-swellable crosslinked polymer of basicity in water is a crosslinked polyethylenimine or a crosslinked polyallylamine, and further characterized by exhibiting a desalting amount of not less than 0.35 g/g.

A production process for a water-swellable crosslinked polymer composition including a blend of water-swellable crosslinked polymer particles of acidity in water and water-swellable crosslinked polymer particles of basicity in water, with the process being characterized by comprising the step of adding the water-swellable crosslinked polymer particles of basicity in water to the water-swellable crosslinked polymer particles of acidity in water, thereby neutralizing at least part of acid groups of the water-swellable crosslinked polymer particles of acidity in water to form ionic bondings in a state where water is present between the particles.

A production process for a water-swellable crosslinked polymer composition including a blend of a water-swellable crosslinked polymer of acidity in water and a water-swellable crosslinked polymer of basicity in water, with the process being characterized by comprising the step of blending the water-swellable crosslinked polymer of acidity in water and the water-swellable crosslinked polymer of basicity in water under conditions where at least one of the water-swellable crosslinked polymer of acidity in water and the water-swellable crosslinked polymer of basicity in water is in a hydrogelled state, and further characterized in that both the water-swellable crosslinked polymer of acidity in water and the water-swellable crosslinked polymer of basicity in water have an extractable content of not more than 10 weight % before blending.

A production process according to 10, wherein the water-swellable crosslinked polymer of acidity in water and the water-swellable crosslinked polymer of basicity in water are blended so that the applied force due to blending may be a facial pressure less than 50 kg/cm2 or a linear pressure less than 25 kg/cm.

A production process according to 10, wherein the water-swellable crosslinked polymer of acidity in water is in a hydrogelled state before blending, when this polymer has an average gel particle diameter of 100˜1,500 μm.

A production process according to 10, wherein the water-swellable crosslinked polymer of acidity in water has a water content of 1˜20 weight % before blending, when this polymer has an average particle diameter of not less than 300 μm.

A production process for a water-swellable crosslinked polymer of acidity in water, comprising the steps of:

• carrying out aqueous solution polymerization of a polymerizable monomer in the presence of a copolymerizable crosslinking agent, wherein the polymerizable monomer contains at least one acid group selected from the group consisting of carboxylic acid groups, sulfonic acid groups, and phosphoric acid groups, and 80 to 100 mol % of the acid groups in the polymerizable monomer are present in the acid form;
• and heating the resultant hydrogelled polymer at a temperature of not lower than 100° C. so that the water content in the polymer will be in the range of 1 to 20 weight % (but not including 20 weight %);
• and further, if necessary, pulverizing the heated polymer.