Patent GB-1283721-A (GB)
Title: Methods and apparatus for producing fibrous webs and the production of products therefrom
Inventor: BRIDGE FRANK
IPC: D04H1/72
Filed: 1969-07-22
Abstract: 1283721 Non woven fabrics ASSOCIATED PAPER MILLS Ltd 22 July 1969 36780/69 Headings D1N and D1R A web is made by feeding fibres directly from a fixed supply zone to a variable area suction zone 14 having a larger effective area than the supply zone so that lateral movement of the fibres occurs as they fall downwardly to produce zones of progressively decreasing fibre density. As shown, fibrous material is fed into the air passing along pipe 22 to hammer mill 4 which disintegrates the material into individual fibres. The fibre stream at superatmospheric pressure is fed downwardly through screen 5 into expansion zone 6 maintained at atmospheric pressure so that they fall downwardly in zones of progressively decreasing fibre density to the stationary or moving or rotating conveyor positioned over variable area suction zone 14 maintained at subatmospheric pressure. Preferably a reservoir zone is positioned in the air flow system so as to avoid fluctuations in pressure over the surface. The air stream can be simultaneously cycled in an alternative path back to the air stream from the suction zone 14. Some of the air from the suction zone may be expelled with or without recovery of the fibres in the air stream. Humidity in the expansion chamber can be controlled by admitting water to the recirculated air. The fibre-laden air stream falling through the expansion zone is controlled by movable side walls 113, 115 &c and a parabolic front wall. The area of the conveyor on which the fibres are laid can have the suction controlled by removable slats in a grid immediately below the conveyor (Figs. 5 and 6A). The air flow in the expansion chamber can also be controlled by feeding air into it under the side walls or via adjustable panels in the side walls. There may be a plurality of fibre supply zones feeding a single expansion zone, there being a corresponding number of suction zones 14 being disposed beneath the conveyor. The fibres may be of wood, cotton, glass, nylon, viscose polyvinyl alcohol or polyester or mixtures of different kinds and lengths thereof. Particulate material, e.g. china clay, kieselghur, activated carbon, carbon black, graphite, mica, aluminium, bronze, coconut shell fibre, sawdust, boric oxide or acid, boron nitride, silica gel, fullers earth or sodium chloride, can be added to the fibres in the expansion zone. The fibres and fillers can be fed to the different fibre supply zones and produce a layered web. Particulate binders, e.g. phenol-formaldehyde, urea-formaldehyde or melamine-formaldehyde resins or polyvinyl alcohol fibres, can be added to the fibres in the expansion zone. The polyvinyl alcohol fibres can be wetted with water to bond the web. Liquid binders can be used and may be natural rubber latex, neoprene, copolymers of styrene and butadiene, acrylonitrile and butadiene, acrylic methyl methacrylate, polyvinyl alcohol, polyvinyl acetate, melamine-formaldehyde resins, starch, carboxy methyl cellulose, methyl cellulose or sodium silicate. A scrim can be provided on the upper surface of the conveyor so that the layer of the fibres is formed thereon. A second scrim can be applied to the fibre layer. The scrim may be formed of nylon, glass, cotton, flannelette, polyester, polynosics or polyethylene. The web from the laydown zone is pressed between rolls and fed between two further conveyor belts (Fig. 2) and impregnated with liquid by roller. Excess liquid is collected by suction device 66 and tray 52 and is recirculated. The impregnated web is then fed to a further conveyor 72 and passed through an infra-red tunnel 78 and drying cylinders 82. The dried web can be calendered and glazed.