Patent ID: 7615579

Claim:
A method of preparing superabsorbent polymers comprising the steps of a) dissolving at least one acrylic acid monomer and/or its sodium salt and a cross-linking agent in an aqueous solution to form a monomer solution; b) adding to the monomer solution a resin encapsulated carbonate blowing agent in sufficient amount to form, when polymerized to a hydrogel, a microcellular expanded polymer gel, wherein said resin is selected from natural or synthetic resins, acrylonitrile-butadiene rubbers, viscous settable ceramic materials, polyolefins, polyethylene gylcol, olefin copolymers, polyaromatic olefins, styrenic compounds or polymerized halo-diolefins, and wherein the resin encapsulated blowing agent provides a controllable delayed release of the blowing agent; and c) initiating polymerization by adding to the monomer solution either immediately before or immediately after, or simultaneously with the addition of the encapsulated blowing agent, an effective amount of at least one free radical initiator and polymerizing at temperatures ranging from about 0° C. to about 130° C. to form a microcellular hydrogel wherein said superabsorbent polymers have a vortex time of about 32 seconds of less, a AUL (0.9 psi) of about 10 g/g or more and a tea bag retention of about 20 g/g or more.