GB816696A - A process for coating rigid sheet materials with thermoplastic synthetic resins - Google Patents

Abstract

Rigid sheet materials coated with a thermoplastic synthetic resin are produced by scattering the synthetic resin in the form of granules or a pre-gelled powder on to the sheet material, placing the sheet material between the heatable platens of a press and applying heat and pressure. The granules are defined as being obtained by kneading the synthetic resin with a plasticiser and, if desired, other additives, e.g. stabilizers, fillers and pigments, at an elevated temperature, e.g. about 120 DEG to 170 DEG C., until a homogeneous mixture is obtained and then disintegrating the mixture into regular or irregular particles. Pregelled powders are defined as being obtained by mixing the resin in powder form with plasticiser and, if desired, other additives at a lower temperature, e.g. about 100 DEG to 120 DEG C., as described in Specifications 653,965 and 654,477, [both in Group IV (a)]. The sheet material may be wood fibre insulating sheet or plywood and may be pre-compressed before the resin particles are scattered thereon. The synthetic resin may be a vinyl chloride polymer which may be mixed with dioctyl phthalate, white lead, calcium stearate and pigment in the formation of the granules or pregelled powder. The temperature during the pressing step may be between 150 and 180 DEG C., and the pressure applied is greater than the vapour pressure of any volatile constituents released from the sheet material under the influence of heat, e.g. 15 to 35 kg./cm.2 when wood fibre insulating sheets are used.