Aqueous dispersion of acrylic polymer

Claim 2

An aqueous dispersion according to claim 1 wherein polymer (A) has a glass transition temperature (Tg A ) of from -20°C to less than 5°C.

Claim 3

An aqueous dispersion according to claim 1 or 2 wherein polymer (B) has a glass transition temperature (Tg B ) of from -100°C to -20°C.

Claim 4

An aqueous dispersion according to claim 1, 2 or 3 wherein Tg A is higher than Tg B by 10°C or more.

Claim 5

An aqueous dispersion according to any one of the preceding claims wherein the particles contain from 60 to 90 weight % of polymer (A) and from 40 to 10 weight % of polymer (B) based on the weight of the particles.

Claim 6

An aqueous dispersion according to any one of the preceding claims wherein polymer (A) contains from 2.5 to 150 mg equivalent of carboxyl groups per 100 g of the polymer (A).

Claim 7

An aqueous dispersion according to any one of the preceding claims wherein polymer (A) is obtainable by copolymerizing: (M-1) from 40 to 99.5 weight % of an acrylic acid alkyl ester of formula (I) CH 2 = CH-COOR 1 (I) wherein R 1 is straight-chain or branched chain C 2 -C₁₂ alkyl and wherein the glass transition temperature of a homopolymer thereof is -20°C or less; (M-2) from 0.5 to 20 weight % of a C 3 -C 5 α,β-unsaturated mono- or dicarboxylic acid; (M-3) from 0 to 59.5 weight % of a (meth)acrylic monomer other than the above (M-1) which other monomer is of formula (II) wherein R 2 is hydrogen or methyl, and X is C 6 -C 8 aryl, nitrile, -COOR 3 or -OCOR 4 , wherein R 3 is straight-chain or branched-chain C 1 -C₂₀ alkyl, straight-chain or branched-chain C₁₀-C₂₀ alkenyl, C 6 -C 8 cycloalkyl or C 7 -C₂₀ aralkyl and R 4 is hydrogen or straight-chain or branched-chain C 1 -C₁₂ alkyl; and (M-4) from 0 to 5 weight % of another monomer having at least one radical-polymerizable unsaturated group in the molecule.

Claim 8

An aqueous dispersion according to any one of the preceding claims wherein polymer (B) is obtainable by copolymerizing: from 50 to 100 weight % of a monomer (M-1); from 0 to 10 weight % of a monomer (M-2); from 0 to 50 weight % of a monomer (M-3); and from 0 to 5 weight % of a monomer (M-4); wherein the monomers (M-1) to (M-4) are as defined in claim 7, and each of which monomers may be the same or different to those for polymer (A).

Claim 9

An aqueous dispersion according to claim 8 when dependent upon claim 7 wherein the total amounts of the said monomers (M-1) to (M-4) are from 40 to 90 weight % of monomer (M-1), from 0.5 to 10 weight % of monomer (M-2), from 0 to 60 weight % of monomer (M-3) and from 0 to 5 weight % of monomer (M-4).

Claim 10

An aqueous dispersion according to any one of the preceding claims wherein the particles have an average particle size of from 0.05 to 0.5 microns.

Claim 11

An aqueous dispersion according to any one of the preceding claims wherein the particles contain from 5 to 150 mg equivalents of carboxyl groups per 100 g of the particles.

Claim 12

An aqueous dispersion according to any one of the preceding claims wherein the concentration of solid components is from 10 to 70 weight %.

Claim 13

A process for preparing the aqueous dispersion as claimed in any one of the preceding claims which process comprises (1) emulsion polymerizing monomers (M-1), (M-2), optionally monomer (M-3) and optionally monomer (M-4) (wherein (M-1) to (M-4) are as defined in claim 7) in an aqueous medium in the presence of a surfactant and/or a protective colloid to form an emulsion of polymer (A), and (2) continuing emulsion polymerization with one stage or multi-stage addition of monomer (M-1) and optionally monomers (M-2), (M-3) and (M-4) (wherein (M-1) to (M-4) are as defined in claim 8) in a rate necessary for forming a polymer (B).

Claim 14

An aqueous coating composition comprising an aqueous dispersion as defined in any one of claims 1 to 12 and an inorganic filler.

Claim 15

A composition according to claim 14 wherein the inorganic filler is selected from calcium carbonate, silica, alumina, kaolin, clay, talc, diaton earth, mica, aluminum hydroxide, glass powder, barium sulfate and magnesium carbonate.

Claim 16

A composition according to claim 14 or 15 containing the inorganic filler in an amount of from 100 to 390 weight parts per 100 weight parts of solid components in the aqueous dispersion.

Claim 17

A composition according to claim 14, 15 or 16 wherein the inorganic filler has an average particle size of from 1 to 50 microns.

Claim 18

A composition according to any one of claims 14 to 17 wherein the aqueous coating composition is capable of forming a chip-resistant coat.

Claim 19

An article coated with a composition as defined in any one of claims 14 to 18.