GB600662A - Improvements in or relating to synthetic resins and stoving enamels - Google Patents

Abstract

In preparing phenol-formaldehyde liquid resins, for use in water and acid resistant stoving enamels, as described in Specification 597,034 by condensing under reflux approximately equimolecular proportions of phenol and aqueous formaldehyde in increasing temperature stages, the temperature of the final stage being 70-85 DEG C. and the temperature and time of the stage being co-ordinated so that "pin holing" is absent on storing a catalyst in proportion of 0.6-1.9 per cent (calculated on the phenol) comprising ammonia or an equivalent quantity of triethanolamine, pyridine or trimethylamine is used in effecting the condensation which is stopped when the viscosity of the resin is 800-1500 centistokes at 25 DEG C. Enamels are produced as in the above Specification by mixing the resins with the solvent medium having a boiling range of 78-170 DEG C. and having constituents such as industrial methylated spirit, butyl alcohol, butyl acetate, diacetone alcohol, ethyl lactate, benzyl alcohol and ethylene glycol mono-butyl ether. Fillers such as mixtures of titanium dioxide and china clay, green chromium oxide and china clay or barium sulphate, china clay and carbon black, aluminium powder and quartz and dyes such as Monastral Green, Monastral Blue, Monolite Red, Monolite Yellow, Lithol Scarlet and Caledon R (Blue) may be added. In the example a resin was prepared from phenol, 40 per cent formaldehyde and aqueous ammonia (0.880 S.G.) in stages of 55 DEG C. for 1 1/2 hours, 60 DEG C. for 2 hours and 80 DEG C. for 1 3/4 hours (the rise from 60 DEG to 80 DEG C. taking 15 minutes). The solids content of the resin was standardized to 60 per cent with industrial methylated spirit and enamels made from the resin, a water-miscible solvent mixture and (a) green chromium oxide, china clay and light mineral oil, and (b) china clay, barium sulpha e, carbon black and light mineral oil.