GB296514A - Improvements in the manufacture of phenolic resins - Google Patents

Abstract

296,514. British Dyestuffs Corporation, Ltd., Strafford, N., and Walker, E.E. July 7, 1927. Phenolic condensation prodructs.-Free phenol and soluble condensation products, usually of low molecular weight, are removed from resinous phenolic condensation products by incorporating the resins with an inert filler such as wood, meal or pulp, cotton &c. wastes, asbestos, china clay, fullers earth, &c. and extracting with a solvent such as water, benzene or ether. Instead of incorporating with a filler, the resin may be spread on paper or fabric, and after extraction of the phenolic impurities the sheets may be dried and pressed to form laminated products. The extraction may be preceded, accompanied or followed by adjustment of the pH, preferably to a value beween 3.5 and 7. Specification 259,046 is referred to in this respect. The liquid resole, or the solid obtained by evaporation of water, is incorporated with the filler or spread on sheets in thin layers, and suspended in water. The pH value is adjusted by the addition of soluble acids or alkalies, in the presence or absence of " buffer '' substances such as sodium salts of weak acids. It is preferable to adjust the pH value before extracting the phenolic impurities. After extraction, the resin may either be dissolved off the substratum and used as a varnish, or separated from water, dried and the whole used as a moulding powder. Catalysts, plastics, pigments, &c. may be added before use. Several examples are given.