Synthetic resinous coating materials

摘要

A thermoplastic coating or laminating composition comprise a fused blend of between 95 and 30 weight per cent of a thermoplastic copolyester having a glass temperature between 40 DEG and 120 DEG C. and 5 and 70 weight per cent of a thermoplastic copolyester having a glass temperature between -50 DEG and 40 DEG C., the difference between the glass temperatures of the two resins being at least 15 DEG C. Suitable copolyesters are linear polymers of glycols and dicarboxylic acids, which are usually aromatic or aromatic-aliphatic mixtures. The glycols may be polymethylene glycols of 2-10 C atoms, or, e.g. dimethylol cyclohexane or 2,2,-bis-[4-(b -hydroxyethoxy) phenyl]-propane, and suitable acids are terephthalic, isophthalic, 1,5-, 2,6- and 2,7-naphthalene dicarboxylic acids, adipic, azelaic and sebacic acids. The polyester of higher glass temperature may be a copolymer of ethylene glycol and neopentylene glycol terephthalates in 80/20 to 20/80 molar ratios, of ethylene glycol tere- and iso-phthalates in 75/25 to 50/50 molar ratios, or of ethylene and neopentylene glycol tere- and iso-phthalates in 80/20 to 30/70 and 70/30 to 30/70 molar ratios of glycols and acids respectively. The polyester of lower glass temperature may be a copolymer of ethylene glycol and neopentylene glycol terephthalate and sebacate in which the glycol and acid molar ratios are 95/5 to 30/70 and 95/5 to 60/40 respectively, or of ethylene glycol terephthalate and sebacate in 85/15 to 60/40 molar ratios. Fillers and pigments may be added, e.g. TiO2, Cr2O3 and finely divided silica, up to 50 weight per cent of the resins.ALSO:An article e.g. aluminium, zinc, zinc-coated steel, cast iron, and ceramic is coated by forming a suspension, e.g. fluidized bed, of particles of a fused blend of resins comprising between 95 and 30 weight % of a thermoplastic copolyester resin having a glass temperature between 40 DEG C. and 120 DEG C. and between 5 and 70 weight % of a thermoplastic copolyester resin having a glass temperature between -50 DEG C. and 40 DEG C., the difference between the glass temperatures of the two resins being at least 15 DEG C., heating the article to at least the fusion temperature of the blend, contacting it with the particles for a time sufficient for the resin to coat the article, and removing the article when a coating of the required thickness has been deposited, and fusing the coating, and cooling the coated article. Suitable copolyesters may be derived from ethylene and neopentylene glycols and terephthalic acid and isophthalic acid (for the higher glass temperature) or terephthalic acid and sebacic acid (for the lower glass temperature) (see Division C3). In examples steel panels heated to 300 DEG C. are immersed for 3 seconds in beds of particles of blends of such resins fluidized by a stream of dry air, or the panel may be immersed at 232 DEG C. and maintained at 232 DEG C. after immersion to fuse the adhered particles.