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Very small amounts of certain metal ions promote copolymerization of aliphalic dicarboxylic acids with ab

Very small amounts of certain metal ions promote copolymerization of aliphalic dicarboxylic acids with ab

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In the process for the manufacture of water-soluble copolymers of a monoethylenically unsaturated dicarboxylic acid having from 4 to 6 carbon atoms and an ab2,000 to about 1,000,000, in which said dicarboxylic acid which is at least partially neutralized is reacted with an ab3 to 10 carbon atoms and

In the process for the manufacture of water-soluble copolymers of a monoethylenically unsaturated dicarboxylic acid having from 4 to 6 carbon atoms and an ab2,000 to about 1,000,000, in which said dicarboxylic acid which is at least partially neutralized is reacted with an ab3 to 10 carbon atoms and the alkali metal and ammonium salts thereof, (b) an organic sulfonic acid compound and the alkali metal and ammonium salts thereof, and (c) a vinyl monomer free of carboxyl and sulfonic acid groups, and mixtures of said (a), (b) and (c) monomers, at an elevated temperature in an aqueous polymerization system substantially free of an organic chain transfer agent, and in which said dicarboxylic acid is first dissolved in said aqueous polymerization system and is at least partially neutralized, and said ab3 to 10 hours, the total amount of monomers employed in said reaction comprising at least about 30 percent, by weight, of said aqueous polymerization system, the improvement which comprises reacting from about 25 to about 55 percent by weight, based on total weight of monomers, of said dicarboxylic acid with from about 45 to about 75 percent of any of said monomers (a), (b), and (c), and mixtures thereof, and carrying out said polymerization reaction at a temperature of from about 80°to about 100°C. in the presence of from about 1 to about 250 ppm, of a metal ion selected from the group consisting of Zn++, Co+++, Co++, Cu++, Mo++, Fe+++, Fe++, Cr+++, Ni++, Ce++++and Ce++, based on the total weight of the aqueous polymerization system, said concentration of said metal ions being increased proportionally with increase in the molar ratio of said dicarboxylic acid monomer to the total of said (a), (b) and/or (c) monomers, the pH of said polymerization system being maintained in the range of from about 2 to about 4 when the molar ratio of dicarboxylic acid monomer to other monomers is from about 1:4 to about 1:3, and from about 4 to about 6 when the molar ratio of dicarboxylic acid monomer to other monomers is from about 1:1.5 to about 1:1.