GB1095953A - Aqueous stoving lacquers - Google Patents

Abstract

Aqueous stoving lacquers comprise amine salts of tetrahydrophthalic or endomethylene-tetrahydrophthalic acid semiesters of alkyd resins which are fatty acid modified and contain free hydroxyl groups, said alkyd resins containing residues of polyols having three or more hydroxy groups, and optionally also of diols, and dicarboxylic acids in molar ratios of 1-1.3:1, and having acid numbers below 15 and hydroxy numbers of 90-300 before semi-esterification, the semi-esters having acid numbers of 30-80 and hydroxy numbers of 60-200. Suitable components of the alkyd are glycerol, trimethylolpropane, pentaerythritol, dipentaerythritol, and sorbitol, optionally with minor amounts of ethylene glycol, diethylene glycol, the butylene glycols and neopentylene glycol; adipic, isophthalic and phthalic acids. Suitable modifiers are castor, dehydrated castor, coconut, soya and linseed oils; soya, linseed, coconut and dehydrated castor oil fatty acids, ricinoleic and hydrogenated ricinoleic acids, natural and synthetic first runnings fatty acids and fatty acids from paraffins, and optionally also benzoic, t-butylbenzoic and resinic acids. Suitable amines are primary, secondary and tertiary alkylamines, aminoalcohols, amino-ethers, e.g. methyl-, diethyl-, triethyl-, ethanol-, diethanol-, triethanol-, N - methyl - ethanol-, N:N - dimethyl - ethanol-, 3 - propanol-, and 3 - methoxypropyl - amines and morpholine. The lacquers may also comprise water-miscible organic solvents, e.g. alcohols, ether-alcohols, esters, ketones, keto-alcohols and ethers, e.g. ethylene glycol methyl, ethyl or butyl monoethers. The neutralized product should have a pH of less than 8 in 30 solids per cent solution. In Example (1) a pentaerythritol/natural first runnings fatty acid (of A.N. 340-350)/phthalic anhydride alkyd of acid number (A.N.) 6 (molar ratios 1:0.9:0.9) is heated at 140 DEG C. for 30 minutes with tetrahydrophthalic anhydride to give a product of AN=40, which is treated with ethylene glycol monobutyl ether and dimethyl-ethanolamine and water to give a 55% lacquer solution, which is mixed with rutile TiO2 and a methylated melamine-formaldehyde solution to give a white stoving lacquer. In Example (5) the fatty acid used is a coconut/ricinoleic mixture, and in Example (6) the endomethylene tetrahydrophthalic acid semiester is prepared, the other components being the same.ALSO:Aqueous stoving lacquers contain at least one amine salt of tetrahydrophthalic acid or endomethylene tetrahydrophthalic acid semiesterified with an alkyd resin derived from at least one polyol having three or more hydroxy groups, and optionally also at least one diol, and a dicarboxylic acid, modified with a fatty acid and containing free hydroxy groups (see Division C3). In Examples lacquers are prepared from pentaerythritol-fatty acid-phthalic anhydride alkyds esterified with tetrahydrophthalic or endomethylene tetrahydrophthalic anhydride and dissolved in ethylene glycol monobutyl ether and aqueous dimethyl-ethanolamine. TiO2 and a methylated melamine resin are added and the lacquer is applied by spray gun to metal sheets, which are air-dried and stoved.