GB314937A - Improvements in or relating to the preparation of thermoplastic sheets - Google Patents

Abstract

314,937. Wade, H., (Bakelite Corporation). Aug. 28, 1928. [A Specification was laid open to inspection under Sect. 91 of the Acts, July 6, 1929]. Fabrics composed of fibrous material agglutinated by adhesives.-Thermoplastic sheet material is made by preparing a pulp composed of fibre and a reactive plastic resin in subdivided state suspended .in water or other liquid, continuously forming a sheet therefrom by laying the pulp, draining off excess liquid, and then drying out the residual liquid under conditions which preclude the reaction of the resin to an infusible state and lessening of the plasticity of the resin. Drying may be effected by subjecting the moist sheet to a current of dehydrated air or other gas, the latter being first passed over chemical agents such as concentrated sulphuric acid or calcium chloride. or over cooled pipes in a refrigerating apparatus, and then heated by passage through steam coils. The gas is preferably blown against both surfaces of the paper in the middle thereof. The temperature of the current is regulated according to the progress, of the drying and the nature of the resin, and the actual temperature of the sheet is kept below the fusion point of the resin. An alternative method of drying the sheet, after removing the excess liquid by suction, by shaking, by felt rollers or other means, consists in passing it through a chamber in which it is subjected to reduced pressure and heated by means of heated rollers. Both methods of drying may be used in succession. The process is applicable to sheets containing synthetic resins of all types, but is particularly intended for use with resins of the phenol aldehyde and cresol aldehyde types.