Superabsorbent composition and process

An ionically cross-linked poly (alkali metal acrylate) superabsorbent composition comprising a foam product resulting from the process of uniformly reacting acrylic acid, an alkali metal salt of carbonic acid, aluminum acetate, sodium persulfate and water at a temperature of at least 70.degree. C. said composition being substantially neutral and water insoluble and is an alkali metal polyacrylate having a total residual monomer content of both acrylic acid and alkali metal acrylate monomers of less than about 800 ppm.

An ionically cross-linked poly (alkali metal acrylate) superabsorbent composition comprising the reaction product of about 100 parts of acrylic acid by weight, sufficient parts of an alkali metal salt of carbonic acid to substantially neutralize said acrylic acid, from about 1 to about 7 parts of aluminum acetate, from about 0.2 to about 2 parts of sodium persulfate, and from about 75 to about 175 parts of water reacted in a microwave oven at a temperature of at least 70.degree. C., said reaction product being an alkali metal polyacrylate in the form of a foam having a residual total monomer content of less than about 800 ppm.

A free radical polymerization process for preparing a poly (alkali metal acrylate) using a chemical free-radical initiator, an ionic crosslinking agent, acrylic acid, an alkali metal salt of carbonic acid, and water comprising the steps of:

• conducting the polymerization reaction by treatment with ultra high frequency waves to obtain a temperature of at least 70.degree. C. for a time sufficient to obtain polymerization whereby the polymerization reaction occurs virtually simultaneously throughout the reaction mixture, thereby obtaining a poly (alkali metal acrylate) having a total residual monomer content below 800 ppm.