GB951450A - Abrasive articles - Google Patents

Abstract

<PICT:0951450/C3/1> A method for the production of an abrasive article from a mixture of descrete abrasive elements and a foamable hardenable liquid synthetic resin binder composition comprises initially concentrating the abrasive elements in a portion of the mixture, so that the elements in that portion are in a close substantially contacting relation, while the binder composition is substantially unhardened, causing foaming of the binder composition to separate the elements by foaming interposed gas cells and then hardening the binder to fix the elements in their slightly spaced apart relation. Initial concentration of the abrasive elements in the binder is effected by means of centrifugal force developed by rapid rotation of the materials about an axis. Suitable abrasives are silicon carbide, aluminium oxide, emery, garnet, talc, pumice, and lime silicon dioxide. As reinforcing materials there may be incorporated glass fibre, nylon, sisal, tampico fibre, steel wire and cotton. As binder these may be used phenolic, epoxy, natural rubber, polyisoprene, butadiene styrene, butadiene-acrylonitrile, polyvinyl chloride and polyurethane resins. In producing abrasive wheels fluid resin, such as polyurethane constituents is discharged into mould 1 through opening 10 and the turntable 3 is revolved to cause the resin to accumulate in portion 11. Granular abrasive is added and migrates to region 13. In the next stage resin is discharged into the central region to give a zone 14 containing resin without abrasive content. Rotation is then stopped, the mould is closed, and the resin is then foamed and set (or cured). Suitable polyurethanes are obtained by reacting a polyol, polyester or polyether with a polyisocyanate or from the corresponding prepolymer. In one example the reaction mixture comprises a polyester (from ricinoleic acid and polyethylene glycol), toluene diisocyanate, water, N-methylmorpholine, emery grit and glycerol monoricinoleate. Another foam is prepared by reacting epoxidised castor oil and refined castor oil with toluene diisocyanate to give a prepolymer which is converted to foam by reaction with a mixture of dimethyl siloxane, distilled water and buffered diethylethanolamine. The flexibility of the polymer may be regulated by choice of esters from reaction products of ricinoleic or stearic acid with glycol, glycerol, propylene glycol, polyethylene glycol, pentaerythritol or castor oil.ALSO:<PICT:0951450/C3/1> A method for the production of an abrasive article from a mixture of discrete abrasive elements and a foamable hardenable liquid synthetic resin binder composition comprises initially concentrating the abrasive elements in a portion of the mixture, so that the elements in that portion are in a close substantially contacting relation, while the binder composition is substantially unhardened, causing foaming of the binder composition to separate the elements by forming interposed gas cells and then hardening the binder to fix the elements in their slightly spaced apart relation. Initial concentration of the abrasive elements in the binder is effected by means of centrifugal force developed by rapid rotation of the materials about an axis. Suitable abrasives are silicon carbide, aluminium oxide, emery, garnet, talc, pumice and lime silicon dioxide. As reinforcing materials there may be incorporated glass fibre, nylon, sisal, tampico fibre, steel wire and cotton. As binder there may be used phenolic, epoxy, natural rubber, polyisoprene, butadiene styrene, butadiene-acrylontrile, polyvinyl chloride and polyurethane resins. In producing abrasive wheels, fluid resin, such as polyurethane constituents is discharged into mould 1 through opening 10 and the turntable 3 is revolved to cause the resin to accumulate in portion 11. Granular abrasive is added and migrates to region 13. In the next stage resin is discharged into the central region to give a zone 14 containing resin without abrasive content. Rotation is then stopped, the mould is closed, and the resin is then foamed and set (or cured). The wheels may be provided with a central hole, or annular face plates may be moulded and bonded as part of the finished article. The plates may be of sheet metal, strong paper, cardboard or plastic. Polishing or abrading blocks, pads, belts and tools of special shape can also be prepared. Sections cut from a portion of the grinding dises can also be used. Suitable polyurethanes are obtained by reacting a polyol, polyester or polyether with a polyisocyanate or from the corresponding prepolymer. In one example, the reaction mixture comprises a polyester (from ricinoleic acid and polyethylene glycol), toluene diisocyanate, water, N-methylmorpholine, emery grit and glycerol monoricinoleate. Another foam is prepared by reacting epoxidized castor oil and refined castor oil with toluene diisocyanate to give a prepolymer which is converted to foam by reaction with a mixture of dimethyl siloxane, distilled water and buffered diethyl-ethanolamine. The flexibility of the polymer may be regulated by choice of esters from reaction products of ricinoleic or stearic acid with glycol, glycerol, propylene glycol, polyethylene glycol, pentaerythritol or castor oil.