GB454251A - Improvements in or relating to the manufacture of porous bonded abrasive articles - Google Patents

Abstract

Porous moulded abrasive articles such as grinding wheels are made by forming a flowable mix containing abrasive grains, e.g. fused alumina, and a binder constituted by or admixed with a viscous pore-forming liquid comprising an artificial resin, adding a gas-generating material, e.g. hydrogen peroxide, moulding, drying, and curing. The bonding material may be heat-hardenable artificial resin, e.g. the substances known under the Registered Trade Marks "Glyptal" or "Redmanol," or liquid containing relatively thermoplastic synthetic resin. The viscous poreforming material, the function of which is to form with the gas spherical bubbles which retain their form until the mass sets, may be a quick-setting normally liquid phenol condensation product catalyzed by the addition of hydrochloric acid dissolved in alcohol, or a water solution of the initial condensation product of urea and/or thiourea and formaldehyde, or other artificial resin solution, dispersion or emulsion, alone or mixed with rubber dispersion. Emulsifying agents such as casein solutions, bentonite, triethanolamine oleate, or cellulose acetate or nitrate solutions, may be used to distribute the hydrogen peroxide solution throughout the mix. Agents which retard decomposition of the gas-generating material may be used, e.g. when using percompounds as gas-generator, acetanilide, magnesium sulphate, sodium pyrophosphate, or sodium stannate, alone or in combination. Gas generation may also be restrained by coating the abrasive grain, wetted with furfural, with powdered heat-hardenable phenolic condensation product, thereby removing from the zone of action materials ordinarily associated with abrasive grain which tend to catalyze the formation of gas. Specifications 384,854, 416,614, and 420,912, [all in Group V], are referred to.ALSO:Porous moulded abrasive articles such as grinding-wheels are made by forming a flowable mix containing abrasive grains, e.g. fused alumina, garnet, silicon carbide, emery, or corundum and a p binder constituted by or admixed with a viscous pore-forming liquid comprising an artificial resin, adding a gas-generating material, e.g. hydrogen peroxide, whiting and lactic acid, or per-compounds, moulding, drying and curing. The binder may be heat-hardenable artificial resin, e.g. the substances known under the Registered Trade Marks "Glyptal" or "Redmanol," starches, casein, gum arabic, linseed oil, waxes, natural gums, or liquid containing relatively thermoplastic synthetic resin. The viscous pore-forming material, the function of which is to form with the gas spherical bubbles which retain their form until the mass sets, may be a quick-setting normally liquid phenol condensation product, or a water solution of the initial condensation product of urea and/or thiourea and formaldehyde, or other artificial resin solution, dispersion or emulsion, alone or mixed with rubber dispersion. Emulsifying agents such as casein solutions, bentonite, triethanolamine oleate, or cellulose acetate or nitrate nitrate solutions, may be used to distribute the hydrogen peroxide solution throughout the mix. Agents which retard decomposition of the gas-generating material may be used, e.g. when using per-compounds as gas-generator, acetanilide, magnesium sulphate, sodium pyrophosphate, or sodium stannate, alone or in combination. Gas generation may also be restrained by coating the abrasive grain with heat-hardenable phenolic condensation product, thereby removing from the zone of action materials ordinarily associated with abrasive grain which tend to catalyze the formation of gas. Specifications 384,854, 416,614, and 420,912 are referred to.