ONE COMPONENT HEAT-CURABLE POWDER COATING COMPOSITION
The invention relates to a one component heat-curable powder coating composition comprising a resin containing reactive unsaturations and wherein all said reactive unsaturations are carbon carbon double bonds connected directly to an electron withdrawing group, a thermal initiation system comprising a transition metal catalyst and a peroxide, wherein the peroxide is chosen from the group of peroxyesters, mono-peroxycarbonates and mixtures thereof and a co-crosslinker chosen from the group of vinylethers, vinylesters, vinylamides, itaconates, enamines and mixtures thereof.
1 . One component heat-curable powder coating composition comprising
a resin containing reactive unsaturations and wherein all said reactive unsaturations are carbon carbon double bonds connected directly to an electron withdrawing group
a thermal initiation system comprising a transition metal catalyst and a peroxide, wherein the peroxide is chosen from the group of peroxyesters, mono-peroxycarbonates and mixtures thereof and
a co-crosslinker chosen from the group of vinylethers, vinylesters, vinylamides, itaconates, enamines and mixtures thereof.
2 . Composition according to claim 1 , wherein the peroxide is a peroxyester or monoperoxycarbonate of formula (1)
wherein R 1 , R 2 and R 3 each independently stand for an alkyl, and wherein X stands for R 4 or for OR 4 , wherein R 4 stands for an alkyl, an aryl or for an oligomer or polymer.
3 . Composition according to claim 1 , wherein the peroxide is t-butyl peroxybenzoate, t-butyl peroxy-2-ethyl hexanoate, t-amyl peroxy (2-ethyl) hexanoate or t-butyl peroxy-2-ethylhexyl carbonate.
4 . Composition according to claim 1 , wherein the transition metal catalyst is a Mn, Fe, Co or Cu salt or complex.
5 . Composition according to claim 1 , wherein the co-crosslinker is chosen from the group of vinylethers, vinylesters and mixtures thereof.
6 . Composition according to claim 1 , wherein the resin is a polyester.
7 . Composition according to claim 1 , wherein the composition further comprises an inhibitor.
8 . Composition according to claim 7 , wherein the inhibitor is a hydroquinone or a catechol.
9 . Composition according to claim 1 , wherein the amount of thermal initiation system is chosen such that when the powder coating composition is applied to a substrate and cured at a temperature of 130° C. for 20 minutes, the resulting coating resists at least 50 acetone double rubs.
10 . Process for the preparation of a powder coating composition according to claim 1 comprising the steps of:
a. mixing the components of the powder coating composition to obtain a premix
b. heating the premix to obtain an extrudate
c. cooling down the extrudate to obtain a solidified extrudate and
d. breaking the solidified extrudate into smaller particles to obtain the powder coating composition.
11 . Process for coating a substrate comprising the following steps:
1) applying a powder coating composition according to claim 1 to a substrate
2) heating the substrate.
12 . Substrate that is fully or partially coated with a powder coating composition according to claim 1 .
13 . Use of a powder coating composition of claim 1 to coat a heat-sensitive substrate.
14 . Use according to claim 13 , wherein the heat-sensitive substrate is wood.