A composition comprising an aqueous dispersion of copolymer particles having a z-average particle size in the range of from 50 nm to 500 nm, wherein z-average particle size is determined using dynamic light scattering at a scattering angle of 90° using Zetasizer software version 7.11 with a Malvern Zetasizer Nano ZS90, which polymer particles comprise, based on the weight of the copolymer particles, a) from 75 to 98.5 weight percent structural units of vinyl acetate; b) from 1 to 20 weight percent structural units of a cyclic ketene acetal monomer; and c) from 0.05 to 5 weight percent structural units of a 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 C 1 -C 6 -alkyl; R 1 and R 2 are each independently H, C 1 -C 12 -alkyl, phenyl, or vinyl; or R 1 and R 2 together with the carbon atoms to which they are attached, form a fused benzene ring or a fused C 3 -C 7 -cycloaliphatic ring; and R 1' and R 2' are each independently H or C 1 -C 12 -alkyl; or R 1 and R 1' and/or R 2 and R 2' form an exocyclic double bond; with the proviso that when n is 1: R 3 and R 3' are each independently H, C 1 -C 12 -alkyl, phenyl, or R 3 and R 3' 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 R 3 is H, C 1 -C 12 -alkyl, or together with the carbon atoms to which they are attached form a double bond, a fused benzene ring, or a fused C 3 -C 7 -cycloaliphatic ring. which polymer particles comprise, based on the weight of the copolymer particles, a) from 75 to 98.5 weight percent structural units of vinyl acetate; b) from 1 to 20 weight percent structural units of a cyclic ketene acetal monomer; and c) from 0.05 to 5 weight percent structural units of a 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 C 1 -C 6 -alkyl; R 1 and R 2 are each independently H, C 1 -C 12 -alkyl, phenyl, or vinyl; or R 1 and R 2 together with the carbon atoms to which they are attached, form a fused benzene ring or a fused C 3 -C 7 -cycloaliphatic ring; and R 1' and R 2' are each independently H or C 1 -C 12 -alkyl; or R 1 and R 1' and/or R 2 and R 2' form an exocyclic double bond; with the proviso that when n is 1: R 3 and R 3' are each independently H, C 1 -C 12 -alkyl, phenyl, or R 3 and R 3' 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 R 3 is H, C 1 -C 12 -alkyl, or together with the carbon atoms to which they are attached form a double bond, a fused benzene ring, or a fused C 3 -C 7 -cycloaliphatic ring. R 3 and R 3' are each independently H, C 1 -C 12 -alkyl, phenyl, or R 3 and R 3' 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 R 3 is H, C 1 -C 12 -alkyl, or together with the carbon atoms to which they are attached form a double bond, a fused benzene ring, or a fused C 3 -C 7 -cycloaliphatic ring.