High temperature aqueous polymerization process

Claim 1

An aqueous process for polymerizing carboxylic acid monomers comprising: (a) forming a reaction mixture by feeding into a reactor containing water at a temperature in the range of from about 130° to about 240° C. under elevated pressure (i) one or more carboxylic acid monomers or aqueous solutions thereof selected from the group consisting of C 3 -C 6 monoethylenically unsaturated monocarboxylic acids, C 4 -C 6 monoethylenically unsaturated dicarboxylic acids, anhydrides of C 4 -C 6 monoethylenically unsaturated cis-dicarboxylic acids and the and ammonium salts thereof, (ii) initiator, or an aqueous solution thereof, in an effective amount for initiating free-radical polymerization of said monomers, and (iii) one or more monoethylenically unsaturated carboxyl-free monomers, or aqueous solutions thereof, at a level of from 0 to 20 percent by weight based on the total carboxylic acid monomers, such that water always makes up at least 35 percent by weight of the reaction mixture and wherein the reaction mixture is substantially free of metal ions and substantially free of organic solvent; and wherein substantially all carboxylic acid monomers used are fed into the reactor containing water at a temperature in the range of from about 130° to about 240° C., and (b) maintaining the reaction mixture in said temperature range to form a polymer product having M n below 10,000.