GB323036A - Improvements in or relating to the manufacture of resinous compositions - Google Patents

Abstract

323,036. Wade, H., (Bakelite Corporation). Sept. 13, 1928. Impregnating-compositions for electric insulation.-Condensation products of phenols, including cresols, with furfural are dehydrated by heating in the presence of a non-reactive resin, whereby the tendency of phenol-furfural resins to gelatinize before complete dehydration is avoided and products having good electrically insulating properties, and suitable for use in the manufacture of varnishes and impregnating solutions are obtained. The non-reactive resin may be added before the initial condensation of phenol and furfural, or at any intermediate stage thereof. Suitable condensing agents are sodium hydroxide and carbonate, magnesium and calcium oxides and hydroxides, pyridine, and hexamethylenetetramine. The added resin is preferably one of the phenol-methylene type, which may, however, be wholly or partly replaced by a natural resin such as rosin. The quantity of added resin may be from 10 to 80 per cent of the phenol-furfural resin. The products are reactive resins, which may be hardened .in the usual manner with hexamethylenetetramine or other methylene-containing hardening agent. Varnishes and impregnating solutions suitable for purposes of electrical insulation, such as for impregnating coils, may be prepared from the dehydrated resins by dissolving them in suitable alcoholic or other solvents. Specification 253,519, [Class 2 (iii), Dyes &c.], is referred to.