In a method of preparing an
aqueous dispersion selected from drilling fluids, hydraulic
cement compositions, mineral
pigment containing coatings, and
papermaking furnishes or in a method of preparing a melt extrudate, the improvement comprising: a) producing a
copolymer of
vinyl alcohol (VOH) and 2-acrylamido-2-methyl
propane sulfonic acid or a salt of such acid (AMPS) by steps including continuously feeding with agitation,
vinyl acetate (VAM) and AMPS as comonomers, a free radical yielding
polymerization initiator, and a
solvent for said comonomers, initiator, and
copolymer resulting from the copolymerization of said comonomers, maintaining the resulting reaction
mass in said first
reaction zone under
polymerization conditions for a
residence time sufficient for a major proportion of AMPS fed to said first
reaction zone to polymerize, continuously feeding reaction
mass from said first
reaction zone with an additional supply of AMPS to a second reaction zone, maintaining the reaction
mass in the second reaction zone for a
residence time sufficient to polymerize a major proportion of the AMPS added to the second reaction zone, continuously withdrawing reaction mass from the second reaction zone, separating
copolymer of VAM and AMPS from the latter reaction mass, and saponifying by
hydrolysis and / or alcoholysis a major proportion of the acetate groups in said copolymer to form a copolymer of VOH and AMPS; and b) incorporating the saponified copolymer into the
aqueous dispersion or melt extrudate.