GB1082303A - New polyesters - Google Patents

Abstract

Polyesters are prepared by heating one or more benzene-o-dicarboxylic acids with one or more monohydric alcohols of at least 5 C atoms and a mixture of polyhydric alcohols such that more than 2/3 of the hydroxyl groups therein are primary, and optionally one or more monobasic carboxylic acids, provided that at most 30 wt. per cent of the reagents contributing the carbonyl portion of the ester groups are acids whose ethyl esters have an alkaline hydrolysis constant in water at 25 DEG C. greater than 10-2 litre/mole/sec. The heating is preferably continued until the product has an acid value below 50, the proportions of reagents being such that the hydroxy value is then 50-250. The preferred major acid component is phthalic acid with a -substituted alkanoic acids, e.g. 2-methylnonanoic acid, or benzoic acid as monocarboxylic acids; suitable minor acid components (i.e. those limited to 30 wt. per cent) are castor, dehydrated castor, perilla, coconut, cottonseed, train, soybean and tall oil fatty acids, stearin, succinic, adipic, maleic, acrylic, isophthalic and trimellitic acids. Suitable polyols are ethylene-, diethylene-, propylene- and polypropylene-glycols, butane-1:4-, pentane-1:5-, butene-1:3- and 2-methylpentane-2:4-diols, glycerol, hexane-1:2:6-triol, trimethylol propane, trimethylolethane and pentaerythritol dipentaerythritol and sorbitol. Monohydric alcohols that may be used include amyl, cyclohexyl, decyl, lauryl and stearyl alcohols and oxo or natural oil alcohols. Compositions may include a polyester of the invention, a curable aminoplast resin and a volatile organic solvent. Suitable aminoplasts are methylol derivatives of urea, ethyleneurea, uron, acetoguanamine, benzoguanomine, melamine and ethers of these with e.g. ethanol, butanol, butenol, allyl alcohol, ethylene glycol, glycerol, and ethylene glycol monoethyl ether. Preferred proportions of polyester: aminoplast lie in the range 9:1-1:1. In examples polyesters are prepared from phthalic anhydride and a mixture of trimethylolpropane and hexane-1:2:6-triol or of pentaerythritol and ethylene glycol, and isodecyl alcohol or a synthetic mixture of alcohols. They are mixed with a methylated or butylated methylol melamine resin, rutile TiO2 and a xylene/n-butanol mixture, to give a varnish.ALSO:Tinplate or steel is coated with a varnish comprising a volatile organic solvent, an aminoplast resin, and a polyester derived from a benzene-o-dicarboxylic acid, a mono hydric alcohol of 5 or more C atoms, and a mixture of polyols (see Division C3). In Examples the polyesters derived from phthalic anhydride, isodecanol or an 'oxo' mixture of alcohols, and a trimethylolpropane/hexanetriol or penta erythritol/ethylene glycol mixture; they are mixed with butylated or methylated methylol melamine and TiO2 in xylene/butanol mixture.