Polyvinyl acetate latex
AssigneeRohm and Haas Company
InventorsKebede Beshah, James C. Bohling, Pu Luo
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Abstract
The present invention relates to a process for preparing an aqueous dispersion of a vinyl acetate polymer comprising the step of polymerizing vinyl acetate under emulsion polymerization conditions in the presence of a chain transfer agent which is a hypophosphite salt or X—R1—SH, where R1 is a C1-C4 alkyl group and X is sulfonate, hydroxyl, sulfate, phosphate, phosphonate, carboxylic acid or a salt thereof, or C1-C3-alkyl carboxylate. The process provides a way of lowering the viscosity of the vinyl acetate polymer at a given solids content.
Claims7
A composition comprising vinyl acetate polymer particles dispersed in an aqueous phase, wherein the aqueous phase comprises, based on the weight of the aqueous phase 1) 0.01 to 1 weight percent of a chain transfer agent;
- and 2) 0.05 to 2.5 weight percent of a vinyl acetate oligomer comprising:
- a) from 40 to 90 weight percent structural units of vinyl acetate,
- b) from 5 to 40 weight percent structural units of butyl acrylate,
- c) from 0.2 to 3 weight percent structural units of phosphoethyl methacrylate, and
- d) from 0.1 to 3 weight percent, based on the weight of the aqueous phase, structural units of a sulfur acid monomer selected from the group consisting of 2-acrylamido-2-methylpropane sulfonic acid, a salt of 2-acrylamido-2-methylpropane sulfonic acid, and sodium vinyl sulfonate;
- wherein the chain transfer agent is selected from the group consisting of sodium hypophosphite, potassium hypophosphite, mercaptoethanesulfonate, mercaptopropionic acid, a salt of mercaptopropionic acid, mercaptoethanol, and methyl mercaptoproprionate;
- and wherein the vinyl acetate oligomer has a weight average molecular weight (Mw) in the range of from 1000 to 7000 Daltons.
Dependencies are inferred from the claim text.