Base-coat clear-coat process for multilayer coatings - uses water-thinnable basecoat compsn. contg. water, binder, pigment etc., and a polyamide as rheology-modifying additive

摘要

Process involves (1) applying a water-thinnable basecoat compsn. (A) contg. water, opt. organic solvent, water-thinnable binder, pigment particles and thickener, (2) producing a polymer film from (A) (3) applying a clear topcoat compsn. (B) and (4) stoving the two coatings, the novelty is that (A) contains a polyamide as rheology-modifying additive. Pref. (A) contains a water-thinnable PU resin binder, pref. (a) with 1-80 (esp. pref. 30-70) wt. % water-thinnable MF resin and pref. also with a water-thinnable polyester (PE) and/or polyacrylate (PA) resin with wt. ratio MF:PE/PA = (2:1)-(1:4) and wt. ratio (MF+PE/PA), (PU) = (4:1)-(1:4) pref. (2:1)-(1:2) esp. pref. (1.3:1)-(1:1.3) or (b) with a blocked polyisocyanate (PNCO) together with aq. resins (PE) and/or (PA), with wt. ratio (PNCO + PE/PA):(PU) = (4:1)-(1:4) pref. (2:1-(1:2). (A) contains metal flake pigments. USE/ADVANTAGE - The process is useful esp. for painting motor vehicles by the basecoat/clearcoat method. The process provides an aq. basecoat compsn. with improved shear stability, closed circuit stability and shelf life, which enables the prodn. of coatings with good mechanical strength and chemical resistance and esp. high moisture resistance. (6pp Dwg.No.0/0)