Patent ID: 6809126
Filing Date: 2004-10-26
Classification: C08G,C09D,Y10T

Abstract:
A binder for a powder coating composition comprising at least one urethane acrylate having a glass transition temperature of between 45 and 80Â° C. which is curable with high energy radiation and which, without the additives conventional in a coating formulation, exhibits a melt viscosity &eegr; at 100Â° C. of less than 1000 PaÂ·s, provided that the urethane acrylate is not the reaction product of 1 mole of trimethylol-propane, 3 moles of toluene diisocyanate and 3 moles of hydroxyethyl methacrylate; wherein the binder composition comprises the reaction product ofA) one or more di- or polyisocyanates or mixtures thereof, optionally with the addition of one or more monoisocyanates; B) one or more di- or polyfunctional isocyanate-reactive compounds or mixtures thereof; and C) one or more monofunctional isocyanate-reactive compounds; wherein 1) the ratio of NCO groups in A) to the sum of the equivalents of isocyanate-reactive groups in B) and C) is between 0.8 and 1.2 and (meth)acryloyl groups are present either in B) or C) or in both B) and C), such that 2) the ratio of the equivalents of isocyanate-reactive groups on monofunctional compounds C) to the equivalents of isocyanate-reactive groups on the di or polyfunctional compounds B) is less than 1.2 and 3) the di or polyfunctional isocyanate-reactive compounds B) have an average functionality of less than 2.5; and 4.) the proportion by weight of soft groups in the di- or polyfunctional isocyanates and in the di- or polyisocyanate-reactive components is less than 25 wt. %, based on the total weight of A), B) and C).