GB574792A - Phenol-formaldehyde resins - Google Patents

Abstract

Resins are made by heating a mixture comprising a monohydric phenol having an alkyl (other than methyl) or cycloalkyl substituent in the o-position as well as p-hydroxydiphenyl or o-hydroxydiphenyl or a mixture of p- and o-hydroxydiphenyls, the alkyl or cycloalkyl substituted phenol being from 20-90 per cent by weight of the mixture, with aqueous formaldehyde in the presence of a strongly alkaline catalyst until a low-molecular weight condensation product is formed and subjecting that product to dehydration, e.g. to further heating. Usually 0.9 to 1.1 mols. of formaldehyde are used per mols. of mixed phenols. Phenols specified are o-cyclohexyl phenol, o-tertiary butyl phenol and o-ethyl phenol. Catalysts specified are caustic soda (0.5 per cent), ammonia (2 per cent), caustic potash, calcium hydroxide and quaternary ammonium hydroxides such as trimethyl benzyl ammonium hydroxide. The resins are made by heating the ingredients under reflux till an oily resole has formed, separating and dehydrating the resole by heating in carbon dioxide to 120 DEG C., and hardening if desired by heating at 120-150 DEG C. Varnishes, paints and enamels may be made by blending the resins with drying oils such as tung oil, together with driers such as linoleates or naphthenates of cobalt or lead, and pigments. In examples, the following ingredients are heated with formaldehydes and caustic soda: (1) o-cyclohexyl phenol, o-phenyl phenol, and p-phenyl phenol; (2) o-cyclohexyl phenol and p-phenyl phenol. Specifications 334,572, [Class 2 (iii)], 347,737 and 417,122 are referred to.