GB587303A - Improvements in or relating to compositions containing primary aromatic amine-aldehyde resins - Google Patents

Abstract

A heat-hardened resin composition is made by mixing a primary p aromatic amine-aldehyde resin with a wetting and plasticising compound having the formula <FORM:0587303/IV/1> where R is hydrogen or an aryl, alky or aralkyl group containing 7 carbon atoms or less, or is a heterocyclic carbon radical containing 4 carbon atoms, namely di-2-chlorethyl formal, di - 2 - chlorethyl benzal, di - 2 - chlorethyl enanthal, di-2-chlorethyl propanal, di-2-chlorethyl furfural or di-2-chlorethyl butyral, shaping and heat-treating the shaped mix. A filler such as abrasive grains, for example emery, corundum, dense "regular" fused alumina, porous white fused alumina, silicon carbide and other hard carbides, quartz, glass, garnet or diamonds may be included in the dry mix. The primary aromatic amine, such as aniline, ortho, meta- or para-toluidine or diamino diphenyl methane is reacted with excess of formaldehyde, e.g. 20 per cent above the stoichiometric proportions, or some of the formaldehyde is added after the initial condensation as paraformaldehyde or hexamethylene tetramine, to yield a thermoplastic resin. An organic compound containing chlorine, bromine or iodine and capable of splitting off hydrogen halide at elevated temperatures, such as polyvinyl chloride, polyvinylidene dichloride, rubber hydrochloride, chlorinated rubber, chlorinated polyisobutylene, halogen substituted paraffins and aliphatic chlorhydrins containing less than six carbon atoms, may be added to the mix as additional cross-linking agents. Abrasive wheels are made by wetting abrasive grains in a mixing pan with the wetting liquid, adding powdered fusible resin, mixing, charging the "dry granular mix" into moulds and curing the "green" wheel produced in an oven. In the examples, grinding wheels are made employing di-2-chlorethyl formal as the wetting and cross-linking agent for the primary aromatic amine-formaldehyde resins halogenated cross-linking agents are employed. Specifications 538,406, 561,902 and 563,344 are referred to.