Resins for use in paint powders - by treating solution of thermosetting resin precursor in thin layer evaporator

摘要

Resin powders esp. for use in paint powders for application by electrostatic projection, fluidised bed techniques, etc are prepd. by (a) continuously treating solns. of (I) precursors of thermosetting resins, these precursors already having a mol. wt. several times greater than that of the initial matl. in a thin layer evaporator at an elevated temp., until the desired mol. wt. is obtd. but without effecting complete curing, and with simultaneous evaporation of the solvent until the molten mass contains at least 95 esp. 99 wt % solids, (b) solidifying the molten mass, and (c) converting the solid mass into a powder. (I) is pref. a polyester, polyurethane, or acrylic, epoxy or melamine resin. Accurate control of the mol. wt. of the resin powder, and of the solids content. are obtd. with high productivity.