HYDROPHOBIC VINYL ESTER COPOLYMER DISPERSIONS
An aqueous copolymer dispersion is obtained by emulsion polymerization of a monomer mixture comprising, as main monomers, 10 to 35 weight % of ethylene, 30 to 60 weight % of a vinyl ester of a carboxylic acid having 1 to 9 carbon atoms and 15 to 50 weight % of a vinyl ester of a branched carboxylic acid having 3 to 15 carbon atoms. The monomer mixture also contains 0.1 to 10 weight % of an ethylenically unsaturated monocarboxylic or dicarboxylic acid having 3 to 4 carbon atoms and 0.1 to 10 weight % of a methacrylic or acrylic acid ester modified with epoxide groups and/or hydroxyl groups. The dispersion is stabilized with 0.02 to 2 weight % of a protective colloid, 0.01 to 5 weight % of a non-ionic surfactant and 0.01 to 5 weight % of an anionic surfactant. All weight percentages are based on the total weight of the main monomers.
1 . An aqueous copolymer dispersion obtainable by free-radically initiated emulsion polymerization of an aqueous composition comprising:
(A) a monomer mixture comprising:
(i) 10 to 35 weight % of ethylene;
(ii) 30 to 60 weight % of a vinyl ester of a carboxylic acid having 1 to 9 carbon atoms, whose homopolymer has a glass transition temperature, Tg, greater than 0° C.;
(iii) 15 to 50 weight % of a vinyl ester of a branched carboxylic acid having 3 to 15 carbon atoms, whose homopolymer has a glass transition temperature, Tg, less than 0° C.;
(iv) 0.1 to 10 weight % of an ethylenically unsaturated monocarboxylic or dicarboxylic acid having 3 to 4 carbon atoms; and
(v) 0.1 to 10 weight % of a methacrylic or acrylic acid ester modified with one or more groups selected from epoxide groups and hydroxyl groups,
wherein the weight percentages of the monomers in the monomer mixture are based on the total weight of the monomers (i), (ii) and (iii); and
(B) a stabilizer system comprising:
(a) 0.02 to 2 weight % of a protective colloid;
(b) 0.01 to 5 weight % of a non-ionic surfactant; and
(c) 0.01 to 5 weight % of an anionic surfactant
wherein the weight percentages of the components of the stabilizer system are based on the total weight of the monomers (i), (ii) and (iii).
2 . The copolymer dispersion of claim 1 , wherein the monomer mixture comprises 15 to 30 weight % of ethylene.
3 . The copolymer dispersion of claim 1 , wherein the monomer mixture comprises 40 to 55 weight % of the vinyl ester (ii).
4 . The copolymer dispersion of claim 1 , wherein the monomer mixture comprises 20 to 40 weight % of the vinyl ester (iii).
5 . The copolymer dispersion of claim 1 , wherein the monomer mixture comprises 0.5 to 2 weight % of the ethylenically unsaturated monocarboxylic or dicarboxylic acid (iv).
6 . The copolymer dispersion of claim 1 , wherein the monomer mixture comprises 0.5 to 2 weight % of the methacrylic or acrylic acid ester (v).
7 . The copolymer dispersion of any claim 1 , wherein the vinyl ester (ii) comprises vinyl acetate.
8 . The copolymer dispersion of claim 1 , wherein the vinyl ester (iii) comprises a vinyl ester of a branched carboxylic acid having 8 to 13 carbon atoms.
9 . The copolymer dispersion of claim 8 , wherein the vinyl ester of a branched carboxylic acid having 3 to 15 carbon atoms comprises the following structure:
wherein R 1 and R 2 are alkyl groups containing a total of 7 or 8 carbon atoms.
10 . The copolymer dispersion of claim 1 , wherein the ethylenically unsaturated monocarboxylic or dicarboxylic acid (iv) comprises acrylic acid.
11 . The copolymer dispersion of claim 1 , wherein the modified methacrylic or acrylic acid ester (v) comprises glycidyl methacrylate.
12 . The copolymer dispersion of claim 1 , wherein the monomer mixture also comprises 0.01 to 5 weight %, preferably 0.2 to 1.5 weight %, based on the total weight of the monomers (i), (ii) and (iii), of an ethylenically unsaturated sulfonic acid, preferably vinyl sulfonic acid, or salt thereof.
13 . The copolymer dispersion of claim 1 , wherein the protective colloid comprises hydroxyethylcellulose.
14 . The copolymer dispersion of claim 1 and having a solids content of at least 60 weight %.
15 . A redispersible powder produced by drying the copolymer dispersion of claim 1 .
16 . An adhesive formulation comprising the copolymer dispersion of claim 1 .
17 . An adhesive formulation comprising the redispersible powder of claim 15 .