Process for the preparation of lattices of vinylacetate/olefin copolymers

Claim 2

A process for the preparation of a latex of a vinyl acetate/olefin copolymer comprising the step of copolymerizing vinyl acetate with at least one olefin in aqueous emulsion, in the presence of an initiator, an emulsifier and a protective colloid, said protective colloid comprising a water-soluble polymer (a) containing at least one monomer selected from the group consisting of acrylamide, methacrylamide, substituted or unsubstituted N-alkyl derivatives of acrylamide, and substituted or unsubstituted N-alkyl derivatives of methacrylamide, and a water-soluble polymer (b) of ethylene glycol, said polymer (b) having a molecular weight between 1,000 and 50,000.

Claim 3

The process of claim 1, wherein said vinyl acetate and said at least one olefin are copolymerized with at least one other copolymerizable monomer and wherein said water-soluble polymer (a) is selected from the group consisting of (a) at least one homopolymer containing a monomer selected from the group consisting of acrylamide, methacrylamide, N-alkyl (C 1 -C 4 ) derivatives of acrylamide which are unsubstituted or substituted by amine, hydroxyl or alkoxy (C 1 -C 4 ) groups and N-alkyl (C 1 -C 4 ) derivatives of methylacrylamide which are unsubstituted or substituted by amine, hydroxyl or alkoxy (C 1 -C 4 ) groups, (b) at least one copolymer containing at least two monomers selected from the group consisting of acrylamide, methacrylamide, N-alkyl (C 1 -C 4 ) derivatives of acrylamide which are unsubstituted or substituted by amine, hydroxyl or alkoxy (C 1 -C 4 ) groups and N-alkyl (C 1 -C 4 ) derivatives of methacrylamide which are unsubstituted or substituted by amine, hydroxyl or alkoxy (C 1 -C 4 ) groups and (c) mixtures thereof.

Claim 4

The process of claim 2, wherein said water-soluble polymer (a) is obtained by the polymerization of at least one of said amide monomers at a concentration of 0.1 to 7% by weight, in aqueous solution, at a temperature of 0° to 90° C. in the presence of an initiator selected from the group consisting of a water-soluble free-radical initiator, ultraviolet rays and a combination thereof.

Claim 5

The process of any one of claims 1 to 3, wherein said water-soluble polymer (a) is crosslinked by a water-soluble crosslinking agent.

Claim 6

The process of claim 1, wherein the polymer (b) of ethylene glycol is a homopolymer of ethylene glycol or a mixture of homopolymers of ethylene glycol.

Claim 7

The process of claim 1, wherein, in the protective colloid, said water-soluble polymer (a) represents 15 to 70% by weight protective colloid and said polymer (b) of ethylene glycol represents 30 to 85% by weight protective colloid.

Claim 8

The process of claim 1, wherein the protective colloid is used in an amount of 0.1 to 5% by weight of the monomers to be copolymerized.

Claim 9

The process of claim 1, wherein said olefin possesses 2 to 4 carbon atoms.

Claim 10

The process of claim 2, wherein said at least one other copolymerizable monomer is selected from the group consisting of vinyl esters of branched or unbranched monocarboxylic acids (C 1 -C 12 ), alkyl (C 1 -C 10 ) esters of unsaturated monocarboxylic or dicarboxylic acids (C 3 -C 6 ), vinyl halides and vinlidene halides.

Claim 11

The process of claim 1, wherein the amount of olefin is such that the copolymer obtained possesses a glass transition temperature between -30° and 50° C.

Claim 12

The process of claim 2, wherein the amount of olefin and other copolymerizable monomer is such that the copolymer obtained possesses a glass transition temperature between -30° and 50° C.

Claim 13

The process of claim 1, wherein the monomers are copolymerized in the presence of 0.1 to 3% by weight, relative to the monomers, of an emulsifier selected from the group consisting of anionic, non-ionic and a combination thereof.

Claim 14

The process of claim 1 or 2, wherein a seed polymer is present in the polymerization medium said seed polymer being identical to or different from said copolymer to be obtained.

Claim 15

A latex of vinyl acetate/olefin copolymer obtained in accordance with the process of claim 1, said latex containing particles of copolymer, said particles being present in said latex in a concentration of 10 to 70% by weight and having a size distribution between 0.05 and 1 μm, said copolymer having a glass transition temperature between -30° and 50° C., and said latex having a viscosity between about 50 mPa.s and 80,000 mPa.s.