GB569115A - Improvements in and relating to the manufacture of composite or multiply web or sheet material or articles - Google Patents

Abstract

Compound sheet material is made by subjecting to heat and pressure between pairs of rolls 27, 28, 29, webs of pervious material which have been impregnated with an aqueous dispersion of a thermoplastic or thermosetting <PICT:0569115/IV/1> plastic material while being led from supply rolls 19 around pervious suction drums e dipping into troughs 10 containing the impregnant. The webs may be pre-wetted by passing under rollers 21 dipping in tanks 20. The webs are removed from the drums at a portion of the circumference which is not subjected to suction by doctor knives 23 and supported by rolls 26 are fed to the rolls 27-29 heated by steam; and additional heat may be provided, e.g. by a radio - frequency field before and between the pairs of rolls. Where a thermosetting material is used, the compound sheet material may be part-cured while passing between rolls 27-29 and subsequently moulded and, e.g. to form channels or pipes completely cured as a web or sections cut therefrom by a guillotine 30. The pervious webs may be woven fabric or felt of animal, vegetable or mineral fibres, such as wool, cotton ramie, asbestos, or glass, singly or in combination, wood veneer, or webs produced by compressions, felting, or extrusion from powdered or disintegrated waste fibrous material, e.g. cotton, wool, linen, or jute waste, sawdust, which may be treated with calcium hydrosulphide. The layers may be perforated or roughened. Sheets or webs of plain corrugated, embossed or perforated metal or wire gauze may be incorporated without treatment on the suction drums, as inside or outside layers. Suitable dispersions are made by dissolving sulphonated ocenol or sodium stearate in a cresol-formaldehyde condensation product, and mixing the solution with a 3 per cent aqueous glue solution, or by polymerizing an emulsion of methyl methacrylate and benzoyl peroxide in an aqueous solution of sulphonated ocenol. Urea-formaldehyde resin or a polyvinyl compound such as polystyrene may be used. The thermosetting or thermoplastic material may be dissolved in an alcohol and emulsified in an aqueous solution containing casein, triethanolamine, ammonia and lauryl sulphonate. A layer of varnish may be sprayed on an outer or inner web on its way to the pressure rolls. The outer plies may be of glass fibres and the core of cheap filler material. Specification 551,179, [Group VIII], is referred to.