Process for making thin-wet absorbent foam materials for aqueous body fluids

In a process for the preparation of a collapsed, but expandable, absorbent polymeric foam material which comprises the steps of:

• A) forming a water-in-oil emulsion from:
• 1) an oil phase comprising:
• a) from about 67 to about 98% by weight of a monomer component comprising:
• i) from about 5 to about 40% by weight of a substantially water-insoluble, monofunctional glassy monomer;
• ii) from about 30 to about 80% by weight of a substantially water-insoluble, monofunctional rubbery comonomer;
• iii) from about 10 to about 40% by weight of a substantially water-insoluble, polyfunctional crosslinking agent, and
• b) from about 2 to about 33% by weight of an emulsifier component which is soluble in the oil phase and which is suitable for forming a stable water-in-oil emulsion;
• and
• 2) a water phase comprising an aqueous solution containing from about 0.2 to about 20% by weight of a water-soluble electrolyte;
• 3) the weight ratio of the water phase to the oil phase being in the range of from about 12:1 to about 100:1;
• B) polymerizing the monomer component in the oil phase of the water-in-oil emulsion to form a polymeric foam material;
• and
• C) dewatering the polymeric foam material to an extent such that a collapsed, polymeric foam material is formed that will re-expand upon contact with aqueous body fluids, the improvement which comprises carrying out said emulsion formation and polymerization steps (A) and (B) in a manner such that coalescence of the water droplets formed in the water-in-oil emulsion is reduced so that the number average cell size of the polymeric foam material is about 50 microns or less.