Preparation of an aqueous dispersion of copolymer particles of vinyl acetate and a cyclic ketene acetal monomer

A method comprising the steps of:

• a) contacting under emulsion polymerization conditions at a temperature in the range of from 30° C. to 55° C., and at a pH in the range of from 6.0 to 9.0:
• 1) 75 to 98.5 parts by weight of vinyl acetate;
• 2) 1 to 20 parts by weight of a cyclic ketene acetal monomer;
• and
• 3) 0.05 to 5 parts by weight of a monoethylenically unsaturated acid monomer or a salt thereof;
• to form an aqueous dispersion of copolymer particles comprising structural units of vinyl acetate, the cyclic ketene acetal, and the monoethylenically unsaturated acid monomer or a salt thereof;
• wherein the cyclic ketene acetal monomer is characterized by following structure:
• where n is 0, 1, or 2;
• R is H or C1-C6-alkyl;
• R1 and R2 are each independently H, C1-C12-alkyl, phenyl, or vinyl;
• or R1 and R2 together with the carbon atoms to which they are attached, form a fused benzene ring or a fused C3-C7-cycloaliphatic ring;
• and
• R1′ and R2′ are each independently H or C1-C12-alkyl;
• or R1 and R1′ and/or R2 and R2′ form an exocyclic double bond;
• with the proviso that when n is 1:
• R3 and R3′ are each independently H, C1-C12-alkyl, phenyl, or R3 and R3′ form an exocyclic double bond or a spirocycloaliphatic group or spiro-2-methylene-1,3-dioxepane group;
• with the further proviso that when n is 2:
• each R3 is H, C1-C12-alkyl, or together with the carbon atoms to which they are attached form a double bond, a fused benzene ring, or a fused C3-C7-cycloaliphatic ring.