GB883211A - Improvements in or relating to a method of coating substrates - Google Patents

Abstract

A method of surface coating substrates comprises applying either directly on to a substrate or on to an initially applied primer coat of reactive polyisocyanate polymer as herein defined a coat of an unsaturated polyester resin diluted with a monomeric vinyl compound or with an a ,-b -unsaturated dicarboxylic acid ester co-polymerisable therewith followed by a top mist coat of reactive polyisocyanate polymer or where a primer coat is initially applied to the substrate employing a top mist coat of either a reactive polyisocyanate polymer or an epoxy resin fatty acid ester each of said coats being applied to the preceding coat while it is still wet. Suitable co-polymerisable vinyl monomers include styrene, vinyl toluene, dibutyl fumarate, diethyl maleate, 2-ethyl hexyl acrylate, diallyl phthalate, diallyl maleate, methyl methacrylate, acrylonitrile, vinyl pyrrolidone, triallyl citrate, and 3,9-divinylspiroli metadioxane. The epoxy resin ester may be an unsaturated fatty acid ester of an epoxy resin having an epoxy equivalent of 1 gram equivalent of epoxy groups to 190-4000 grams of resin. By reactive polyisocyanate polymer is meant a reaction product of a diisocyanate and an organic molecule containing unreacted groups reactive with the isocyanate group to form urethane groups, the reaction product having one unreacted isocyanate equivalent group for each urethane group in the polyisocyanate polymer. Examples are given of the preparation of unsaturated polyester resins and of polyisocyanates. The substrate to be coated may be of wood, aluminium, steel or fibre board. The coatings may be applied by spraying. When all the coats have been applied the substrate may be allowed to air dry for about 15 minutes and is then cured for example at 140 DEG F. for about 1 hour. The polyester layer may contain a catalyst of the cobalt organic oil-soluble salt type plus a peroxide. The compositions may also contain driers containing lead and cobalt.ALSO:A method of surface coating substrates comprises applying either directly on to a substrate or on to an initially applied primer coat of reactive polyisocyanate polymer as herein defined a coat of unsaturated polyester resin diluted with a monomeric vinyl compound or with an a -b unsaturated dicarboxylic acid ester co-polymerisable therewith followed by a top mist coat of reactive polyisocyanate polymer or where a primer coat is initially applied to the substrate employing a top mist coat of either a reactive polyisocyanate polymer or an epoxy resin fatty acid ester each of said coats being applied to the preceding coat while it is still wet. Suitable co-polymerisable vinyl monomers include styrene, vinyl toluene, dibutyl fumarate, diethyl maleate, 2-ethyl hexyl acrylate, diallyl phthalate, diallyl maleate, methyl methacrylate, acrylonitrile, vinyl pyrrolidone, triallyl citrate, and 3,9-divinylspiroli (meta-dioxane). The epoxy resin ester may be an unsaturated fatty acid ester of an epoxy resin having an epoxy equivalent of 1 gram equivalent of epoxy groups to 190-4000 grams of resin. By reactive polyisocyanate polymer is meant a reaction product of diisocyanate and an organic molecule containing unreacted groups reactive with the isocyanate group to form urethane groups, the reaction product having one unreacted isocyanate equivalent group for each urethane group in the polyisocyanate polymer. Examples are given of the preparation of unsaturated polyester resins and of polyisocyanates. The substrate to be coated may be of wood, aluminium, steel or fibre board. The coatings may be applied by spraying. When all the coats have been applied the substrate may be allowed to air dry for about 15 minutes and is then cured for example at 140 DEG F. for about 1 hour. The polyester layer may contain as catalyst a cobalt organic oil-soluble salt plus a peroxide, e.g. MEK peroxide. The compositions may also contain driers containing lead and cobalt. Unsaturated polyester resins. The polyester resins mentioned are the polycondensation products of an unsaturated polycarboxylic acid and a polyhydric alcohol. Up to 90% of the unsaturated acid may be replaced by a saturated acid. Specified components are:- Unsaturated acids: maleic, itaconic, citraconic, mesaconic and aconitic. Saturated acids: phthalic, isophthalic, 3,6-cis-endomethylene-delta-4-tetrahydrophthalic tetra- and hexa-hydrophthalic, tetrachlorophthalic, endochloro-methylene-tetrahydrophthalic, the methyl and ethyl esters of the above acids, adipic, pimelic and azelaic. Polyhydric alcohols: Several alkylene glycols, abietyl alcohol, p, p1-isopropylidene bisphenol and its ethylene and propylene adducts. The polyester resins may be dissolved in the comononer and further diluted with ethyl or butyl acetate, acetone, methylethyl ketone, naphtha, turpentine or cyclohexane.