GB1088374A - Water dilutable surface coating alkyd resins - Google Patents

Abstract

Water-dilutable alkyd resins have a backbone comprising residues of polyols, of which at least 90% by weight are residues of hindered diols, and polycarboxylic acids having at least three carboxyl groups per molecule, the resin also containing residues containing b g -ethylenically unsaturated ether groups, and sufficient carboxyl groups to render the resin water dilutable. The hindered diols have at least three carbon atoms, a carbon atom next to each carbon atom carrying the hydroxyl groups being fully substituted by alkyl, aryl or aralkyl groups, preferably C1- 4 alkyl groups, and may be e.g. neopentyl glycol, 2-methyl-2-ethyl-propane-1,3-diol, 2,2 - diethylpropane - 1,3 - diol, 2,2 - dimethylpentane-1,3-diol 2,2-dimethylbutane-1,3 - diol and 2,2,4 - trimethylpentane - 1,3-diol. Suitable polycarboxylic acids are trimellitic, trimesic, hemimellitic, pyromellitic, tricarballylic and camphoronic acids. The unsaturated groups may be derived from mono- or polyhydric alcohols containing at least one b ,g -ethylenically unsaturated ether group, e.g. the monoallyl and diallyl ethers of glycerol, trimethylol ethane and trimethylol propane, and the monoallyl, diallyl and triallyl ethers of pentaerythritol, and the corresponding methallyl compounds. The resins have acid values of at least 30, preferably 50 to 100. The polycarboxylic acids and hindered diols may be replaced by up to 50 mol. per cent of mono- and dibasic acids, e.g. phthalic or maleic acid, and up to 10 wt. per cent of other polyols, respectively. The resin may also contain residues of saturated or unsaturated fatty acids, e.g. dehydrated castor oil acids. It may be prepared by partially esterifying the polycarboxylic acid with the unsaturated ether alcohol, esterifying the resulting ester having at least two free carboxyl groups per molecule, with the hindered diol, and further esterifying the product with more polycarboxylic acid. Fatty acid residues may be introduced at the same time as the hindered diol The polycarboxylic acids are preferably used as anhydrides. The resin is dissolved or dispersed in water or water containing a water-miscible organic solvent, e.g. ethanol, propanol or butanol, or the methyl, ethyl or butyl mono-ethers of ethylene glycol, in the presence of a base, which is preferably volatile, e.g. ammonium hydroxide or a volatile amine, e.g. triethylamine, to give a solution or emulsion which may be diluted with water. In examples, 1 mol. of trimellitic anhydride is reacted with 1 mol. of trimethylol propane diallyl ether to an acid value of 276, then esterified with 2 mols. of neopentyl glycol and 0.75 mols. of dehydrated castor oil fatty acids to an acid value of 5-10, and finally reacted with 0.5 or 0.54 mols. of trimellitic anhydride to an acid value of 64. The resins were dissolved in water containing triethylamine and a cobalt drier, and used to make surface coatings.