Novolak type phenol!-formaldehyde! resin prepn. - by polycondensation of phenolic cpd. and formaldehyde with inorganic catalyst

摘要

Phenolformaldehyde resins of Novolak type are prepd. by polycondensation of a phenolic cpd. with HCHO at 96-100 degrees C with an inorganic catalyst, drying of the resins produced, heat treatment at 130-200 degrees C in presence of 0.1-0.5 wt. % (w.r.t. phenolic cpd.) oxalic acid. After heat treatment a stream of inert gas is passed over the resin. HCl is the catalyst. Used in phenolformaldehyde resin technology particularly in the Novolak range which is used in prepn. of light-stable spirit lacquers for applications in which high melting resins with low free phenol content are required. Lower consumption of raw materials and of steam and higher yield of pure prod. with good light stability is achieved, in comparison with the prior art.