GB893677A - Improved phenol-aldehyde resin-bonded abrasives - Google Patents

Abstract

An abrasive article contains 50-64% by volume of abrasive grains, 12-30% by volume of a heat-hardenable phenol-aldehyde resin bond and 0,8-25%, based on the weight of the total bond, of a condensation product, having a molecular weight between 2000 and 7500, of ethylene oxide and a hydrophobic base formed by the condensation of propylene oxide with propylene glycol. The total bond refers to the whole composition less the abrasive. Abrasives specified are silicon carbide and other hard carbides, diamonds, glass and any of the varieties of alumina such as emery, corundum or fused alumina, quartz and garnet. The phenol-aldehyde resins may be those prepared from phenol and formaldehyde or furfural, and these may be modified by urea, melaminec or amines; the resin may be used in the form of a liquid or a powder, in the latter case a wetting agent, e.g. furfuraldehyde being necessary. Lime or a filler such as cryolite, feldspar, iron oxide and calcined kaolin may be included in the composition for making the article. In Example 1, the abrasive is aluminium oxide, the particles of which are of three specific sizes. A suitable ethylene oxide condensation product is prepared by reacting with ethylene oxide in the presence of sodium hydroxide the water insoluble polyoxypropylene glycol having an average molecular weight of 1620 and prepared by reacting propylene glycol with propylene oxide in the presence of sodium hydroxide. U.S.A. Specifications 2,674,619 and 2,677,700 are referred to.ALSO:An abrasive article contains 50-64% by volume of a brasive grains, 12-30% by volume of a heat-hardenable phenol-aldehyde resin bond and 0,8-25%, based on the weight of the total band, of a condensation product, having a molecular weight between 2000 and 7500, of ethylene oxide and a hydrophobic base formed by the condensation of propylene oxide with propylene glycol. The total band is the whole composition less the abrasive. Abrasives specified are silicon carbide and other hard carbides, diamonds, glass and any of the varieties of alumina such as emery, corundum or fused alumina, quartz and garnet. The phenol-aldehyde resins may be those prepared from phenol and formaldehyde or furfural, and these may be modified by urea, melamine or amines; the resin may be used in the form of a liquid or a powder, in the latter ease a wetting agent, e.g. furfuraldehyde, being necessary. Lime on a filler such as cryolite, feldspar, iron oxide and calcined kaolin may be included in the composition for making the abrasive article. In Example 1, the abrasive is aluminium oxide, the particles of which are of three specific sizes.