Boron-containing phenolic novolacs - with improved thermal stability useful as binders for brake linings

摘要

Thermosetting phenolic novolacs of formula (RO)n-B-(OX)3-n in which R = straight for branched 1-4C alkyl group, n = 1-2, and X = high molecular residue consisting of a phenol- and/or creso-formaldehyde resin which may contain free OH gps., with a B content =15% pref. 1.5-5%, are made by reacting a phenol- and/or cresol formaldehyde resin with boric acid alkyl esters of formula B(OR)3 at elevated temps. Prods. cure at 120-350 degrees C, with or without the addition of formaldehyde-releasing agents to give prods., with high thermal stability, useful e.g. in the prodn. of brake and clutch linings and as reinforcing agents in rubbers for high temp. applications.