GB876525A - Improvements in or relating to power transmission and conveyor belting - Google Patents

Abstract

876,525. Coated multiple - ply fabrics. FENNER & CO. Ltd., J. H. Nov. 18, 1959 [Nov. 27, 1958], No. 38307/58. Addition to 821,059. Class 140. A method of reducing the surface resistivity of impregnated and/or coated multiple-ply textile fabric belting comprises applying a coating of electrically conductive carbon to an outer surface or surfaces of the belting after impregnation and/or coating of the multipleply textile fabric, the impregnating and/or coating material being at least partially gelled before the carbon is applied to the belting surface or surfaces. The impregnating and/or coating material, e.g. polyvinyl chloride, may be substantially fully gelled by heating, e.g. at 170‹ to 180‹ C., before the carbon is applied, and the carbon is applied immediately after the heating step, while the surface is still hot, semimobile or soft, and before the material has cooled e.g. to below 70‹ C. The impregnating and/or coating material, e.g. polyvinyl chloride, may be only partially gelled by heating to a temperature lower than that required for complete gellation, e.g. 90‹ to 100‹ C., before the carbon is applied, and gellation is completed, after the application of the carbon, by raising the temperature of the belting. After gellation is completed, the carbon coating may be consolidated by pressing the belting between rollers before the belting is cooled. The carbon may be applied as a powder by blowing or by spreading with a cloth or brush. As shown, solid woven multiple-ply textile fabric 1 passes through impregnating bath 3 containing a dispersion of approximately 45% by weight polyvinyl chloride powder and 55% by weight tricresyl phosphate, at a temperature of between 15‹ and 35‹ C., and is partially gelled in chamber 13. Carbon black from hopper 4 is supplied to well 5a of chamber 5 where heater 6 raises a cloud of carbon powder which is blown by fan 7 through spraying nozzles 5b and wire gauze screens 8, on to the impregnated fabric. The thus coated fabric is gelled in chamber 14 and passes through rollers 16 to consolidate the coating prior to cooling in chamber 18. When gelling is substantially completed prior to application of the carbon powder, chamber 14 is omitted. Specification 770,524 is referred to.