Low molecular weight monoalkyl substituted phosphinate and phosphonate copolymers

A process for preparing a polymer mixture containing polymeric monoalkyl phosphinates and polymeric monoalkyl phosphonates comprising:

• i) forming a reaction mixture by feeding linearly into an aqueous solution of at least one C.sub.4 -C.sub.8 monoethylenically unsaturated dicarboxylic acid which is up to about 50 percent neutralized, anhydride, or C.sub.1 -C.sub.4 mono-ester thereof, at a temperature of from 60.degree. to 120.degree. C.
• a) hypophosphorous acid chain transfer agent or a salt thereof,
• b) at least one monoethylenically unsaturated monocarboxylic acid or salts thereof, and optionally
• c) non-carboxylic acid monomers;
• wherein the at least one C.sub.4 -C.sub.8 monoethylenically unsaturated dicarboxylic acid which is up to about 50 percent neutralized, anhydride, or C.sub.1 -C.sub.4 mono-ester thereof, is present at a level of from about 5 to about 95 percent by weight based on the total weight of the at least one C.sub.4 -C.sub.8 monoethylenically unsaturated dicarboxylic acid which is up to about 50 percent neutralized, anhydride, or C.sub.1 -C.sub.4 mono-ester thereof, the at least one monoethylenically unsaturated monocarboxylic acid or salts thereof, and the optional non-carboxylic acid monomers;
• ii) polymerizing the reaction mixture to provide a polymer mixture in which at least 40 percent of incorporated phosphorus is in the form of polymeric monoalkyl phosphinate and polymeric monoalkyl phosphonate and wherein the residual monomer level, based on the total amount used, of the at least one C.sub.4 -C.sub.8 monoethylenically unsaturated dicarboxylic acid which is up to about 50 percent neutralized, anhydride, or C.sub.1 -C.sub.4 mono-ester thereof is less than 1 percent by weight.