GB1327792A - Manufacture of reinforced asbestos cement products - Google Patents

Abstract

1327792 Asbestos-cement products TAC CONSTRUCTION MATERIALS Ltd 28 May 1971 [1 June 1970] 26245/70 Headings D2A and D2B A method of making an asbestos-cement product comprises distributing reinforcing fibres at least 10 m.m. long over a layer of wet asbestos-cement on a conveyor felt and thereafter winding the layer on a rotating cylinder. The fibres are formed by cutting a roving 4 of continuous glass filaments by means of a rotary cutter 19 having blades 20, the roving passing from a container 5 between a driven hard rubber roller 8 and a spring-biased roller 9 and then between the rotary cutter 19 and the roller 8. The fibres which may be 25 to 50 m.m. long are carried downward by a stream of air produced by a fan 24 and passing steam or electrically heated rods 25 and are distributed by a driven, speed adjustable, rotating bladed device 30. In a modification, Fig. 3 (not shown), a wider layer of wet asbestoscement is served by a plurality of fibre producing and distributing apparatuses. In a further modification. Fig. 4 (not shown), the distributing device of each apparatus is a driven, rotating, horizontally disposed bladed disc. The layer of wet asbestos-cement is transferred to the felt from the vat of a Hatschek machine and after receiving the reinforcing fibres is transferred to the accumulation bowl of the machine so that a plurality of layers are built up to form a sheet “" thick which is cut axially and removed from the bowl to form a flat sheet. Water may be sprayed on the layer after deposition of the reinforcing fibres, and the water may contain constituents such as chemicals which modify the setting properties of the cement or the final properties of the product. The product may be taken from the forming cylinder in the form of a tube. The reinforcing fibres may be distributed to give random or preferential orientation, and the glass may be alkali-resistant, e.g. zirconium glass consisting of a composite silicate of zirconium, aluminium and sodium in which the amount of zirconium expressed as zirconia is from 10% to 25% by weight of the glass, or it may be protected against alkali by a surface coating, e.g. polyvinyl acetate or epoxy resin. The reinforcing fibres may be of steel, rock wool, carbon or asbestos, or they may be of nylon, polyethylene or polypropylene. The total of asbestos and reinforcing fibres is between 5.5% and 25% of the asbestos, fibre and cement, the reinforcing fibres being at least 0.5% and the asbestos fibres being at least 5%.