GB619975A - Improvements in or relating to the production of oil-modified alkyd resins and to improved coating compositions prepared therefrom - Google Patents

Abstract

Oil-modified alkyd resins are prepared by heating a mixture of castor oil, a polyhydric alcohol and a polybasic acid or anhydride thereof at a temperature between 260 DEG and 270 DEG C. until the initial decrease in viscosity of the reaction mixture has substantially ceased, and, before there is any substantial increase in viscosity adding a sufficient quantity of polyhydric alcohol and/or polybasic acid or anhydride thereof at such a temperature as to reduce the temperature of the reaction mixture to a value not exceeding 230 DEG C., and continuing to react the added polyhydric alcohol and added polybasic acid or anhydride thereof at a temperature between 160 DEG and 230 DEG C. and adding any further polyhydric alcohol and/or polybasic acid or anhydride which may be necessary to produce a reaction product, the oil content of which does not exceed 50 per cent thereof and which contains a small amount of free polyhydric alcohol. Cooling means may be provided to remove the excess heat of the reaction vessel. Preferably, the initial reaction mixture contains 5-75 per cent excess of glycerol over the equivalent amount and contains 40-95 per cent of oil. Any further additions of polyhydric alcohol are preferably made before the addition of further polybasic-acid. Suitable alcohols are glycerol, pentaery, thritol, ethylene glycol, trimethylol propane mannitol, sorbitol and butyne-diol, and suitable acids are phthalic acid and anhydride, tetrahydrophthalic acid, tetrachlorophthalic anhydride, methylene di-salicylic acid, maleic, fumaric and citric acids, and maleic and fumaric acid adducts with terpenes and cyclo-olefines. In examples, castor oil, glycerol and phthalic anhydride are heated at 260-270 DEG C., and when the minimum viscosity is passed sufficient glycerol is added to reduce the temperature to 230 DEG C. Further phthalic anhydride is added, followed by further heating, firstly at 230 DEG C. and then at 180 DEG C.; (2) the procedure of (1) is followed, but a further addition of phthalic anhydride and glycerol is made whilst heating at 180 DEG C.; (3) castor oil, phthalic anhydride and glycerol are heated at 260-270 DEG C. and pentaerythritol added when the minimum viscosity is passed to reduce the temperature to 230 DEG C. Phthalic acid is added and heating continued at 220 DEG C.; (4) sorbitol replaces the pentaerythritol of (3). The products dissolved in xylene are p suitable as varnishes, and cobalt linoleate or naphthenate driers may be added. Specifications 431,495 and 474,620 are referred to. A sample has been furnished under Sect. 2 (5) of a product obtained by heating castor oil glycerol and phthalic anhydride, and when the minimum viscosity is reached adding more glycerol and phthalic anhydride and heating at 220 DEG C., then adding butyne diol and heating at 210 DEG C. The product at 200 DEG C. is dissolved in xylene.