Patent ID: 7858722

Claim:
A method for making a monomer having an ethylenically unsaturated group and two or more quaternary ammonium groups per molecule, comprising: (a) reacting an excess of a monomeric reactant having at least one ethylenically unsaturated group and at least one tertiary amino group per molecule with a halohydroxyalkyl(trialkyl)quaternary ammonium salt, in an aqueous medium, (b) monitoring the pH of the aqueous medium from at least as early as the time when all reactants have been added to aqueous medium until completion of the reaction, and (c) adjusting the pH of the aqueous medium to and maintaining the pH of the aqueous medium at a value greater than or equal to 9, from the time, after all reactants have been added to aqueous medium, that the reaction mixture exhibits an apparent pH minimum until completion of the reaction.