Patent ID: 8138240
Filing Date: 2012-03-20
Classification: C09D,Y10S,Y10T

Abstract:
1. Process for the preparation of a powder coating composition having a glass transition temperature (Tg) at or above 20° C. and comprising (i) a resin having a Tg above 35° C. and functional groups through which the resin can react with a crosslinker, (ii) a crosslinker having functional groups which are able to react with the functional groups of the resin, (iii) a pigment powder, and (iv) a dispersant for dispersing the pigment powder in the powder coating composition, wherein the process comprises the steps of: (a) preparing the resin in a reactor; (b) adding the dispersant to the resin when the resin is in a liquid state at a temperature above the glass transition temperature (Tg) of the resin and at or below 270° C. just before the resin leaves the reactor or while the resin leaves the reactor in an amount of at least 0.01 to at most 10 w/w% based on the weight of dispersant in the resin to obtain a mixture of the resin and the dispersant; (c) solidifying the mixture of step (b); (d) mixing the pigment powder in an amount of more than 40 w/w% based on the weight of the powder coating composition and the crosslinker with the solidified mixture of step (c) to obtain a pigment-containing mixture; (e) homogenizing the pigment-containing mixture of step (d) to obtain a homogenized mixture; and (f) milling and sieving the homogenized mixture to obtain the powder coating composition.