Powder coating composition

1. A composition comprising

a) at least 50 wt. % of TiO 2 particles and

b) at least 10 wt. % of a component which comprises

b1) at least one epoxy resin having at least one carbon-carbon double bond and/or at least one carbon-carbon triple bond which are not terminal,

wherein component b1) is obtained by the reaction of an epoxy resin with an unsaturated component (B), which has at least one carbon-carbon double bond and/or at least one carbon-carbon triple bond which are not terminal and at least one functional group selected from the group consisting of amino, hydroxyl, carboxy and anhydride, and the unsaturated component (B) is an unsaturated fatty acid, a dimerized or trimerized unsaturated fatty acid, polyamidoamine based on an unsaturated fatty acid dimer or trimer, tetrahydrophthalic acid, tetrahydrophthalic anhydride, acetylene dicarboxylic acid, butene diol, a functionalized homopolymer of butadiene or a copolymer of a butadiene with a vinyl or allyl compound selected from the group consisting of acrylonitrile, acrylic acid, methacrylic acid, acrylic or methacrylic acid esters, maleic acid and maleic acid anhydride;

or

b2) a mixture of

i) at least one epoxy resin without a carbon-carbon double bond and without a carbon-carbon triple bond and

ii) at least one unsaturated organic compound (A) wherein compound (A) is selected from a polybutadiene homopolymer having no functional group capable of reacting with an epoxide group, a polybutadiene copolymer having no functional group capable of reacting with an epoxide group, a partly epoxidized polybutadiene, 4,4′-bismaleimidodiphenylmethane and a mixture thereof and does not react with the epoxy resin b2i) and the weight ratio of component i) to ii) ranges from 1000:1 to 10:5; or

b3) any mixture of b1) and b2),

wherein the weight % is based on the total weight of the composition.

2. The composition according to claim 1 wherein the TiO 2 particles are present in an amount ranging from 60 to 90 wt.-%, based on the total weight of the composition.

3. The composition according to claim 1 wherein component b) is present in an amount ranging from 10 to 45 wt.-%, based on the total weight of the composition.

4. The composition according to claim 1 wherein the unsaturated component (B) is selected from the group consisting of unsaturated fatty acid, dimerized or trimerized unsaturated fatty acid, amine terminated butadiene, acrylonitrile copolymer, carboxyl terminated butadiene acrylonitrile copolymer, functionalized and partly epoxidised polybutadiene, polyamidoamine derivatives of unsaturated fatty acid dimer or trimer, tetrahydrophthalic acid anhydride, acetylene dicarboxylic acid, butyne diol, or any mixture or reaction product thereof.

5. The composition according to claim 1 wherein component b1) and/or epoxy resin b2)-i) have a softening temperature of at least 60° C. determined according to DIN 51920 on a Mettler apparatus.

6. A method for the preparation of a masterbatch composition comprising the steps:

a) providing the composition according to claim 1 and

b) melt mixing the composition provided in step a) at a temperature of at least 60 C.

7. A masterbatch composition obtained by the method according to claim 6 .

8. A method for the preparation of a powder coating composition comprising the steps:

a) preparing the masterbatch composition as defined in claim 6 and

b) mixing the masterbatch composition obtained in step a) with a composition comprising na organic compound containing at least one functional group selected from the group consisting of carboxy, anhydride and phenolic hydroxy.

9. A powder coating composition obtained by the method according to claim 8 .

10. A cured powder coating obtained by heating the powder coating composition according to claim 9 .

11. A resin component b) which comprises

b1) at least one epoxy resin having at least one carbon-carbon double bond and/or at least one carbon-carbon triple bond which are not terminal, wherein component b1) is obtained by the reaction of an epoxy resin with an unsaturated component (B), which has at least one carbon-carbon double bond and/or at least one carbon-carbon triple bond which are not terminal and at least one functional group selected from the group consisting of amino, hydroxyl, carboxy and anhydride, and the unsaturated component (B) is an unsaturated fatty acid, a dimerized or trimerized unsaturated fatty acid, polyamidoamine based on an unsaturated fatty acid dimer or trimer, tetrahydrophthalic acid, tetrahydrophthalic anhydride, acetylene dicarboxylic acid, butene diol, a functionalized homopolymer of butadiene or a copolymer of a butadiene with a vinyl or allyl compound selected from the group consisting of acrylonitrile, acrylic acid, methacrylic acid, acrylic or methacrylic acid esters, maleic acid and maleic acid anhydride;

or

b2) a mixture of

i) at least one epoxy resin without a carbon-carbon double bond and without a carbon-carbon triple bond and

ii) at least one unsaturated organic compound (A) wherein compound (A) is selected from a polybutadiene homopolymer having no functional group capable of reacting with an epoxide group, a polybutadiene copolymer having no functional group capable of reacting with an epoxide group, a partly epoxidized polybutadiene, 4,4′-bismaleimidodiphenylmethane and a mixture thereof and does not react with the epoxy resin b2i) and the weight ratio of component i) to ii) ranges from 1000:1 to 10:5; or

b3) any mixture of b1) and b2),

wherein the weight % is based on the total weight of the composition.