GB647105A - Improvements relating to the colouration of sheet materials - Google Patents

Abstract

Sheets of a thermoplastic cellulose derivative are coloured by locally applying a dye soluble in the sheet-material unaccompanied by any substance insoluble in the material, simultaneously or subsequently heating the surface to be coloured to a temperature above the flow-point of the sheet material, and while it is at such temperature applying pressure by means of a polished metal plate. The dye may be applied by (1) first printing the design on to a textile fabric (e.g. cellulose acetate or cotton) in the normal way, washing and drying, and laying the fabric on to the thermoplastic sheet; paper is less suitable than textile fabrics, but other cellulose esters and linear polymers such as nylon may be used; (2) printing the design (e.g. by a screen) on to a polished metal plate, drying and applying this to the sheet; the dye is applied to the plate in the form of a lacquer (e.g. of the cellulose acetate type) all the components of which are soluble in the sheet-material; or (3) silk-screen printing directly on to the sheet and drying. The process is applicable to rigid transparent or translucent sheets and to thin flexible films and foils. The material may be cellulose acetate or other ester derived from one or more fatty acids of two to four carbon atoms, or may be ethyl or benzyl cellulose. Suitable dyes are those of the azo, nitro - diarylamine and amino - anthraquinone series which have affinity for the sheet-material. Further Further effects which may be obtained are: (1) increased brightness of colour by roughening the uncoloured surface of the sheet, e.g. by pressing it against a hot plate engraved with a fine pattern; this plate may be the lower surface of the assembly used to provide heat and pressure for transfer of the colour; (2) dull areas by transferring on to the sheet alongside the areas coloured by the dye a pigment of high refractive index, e.g. titanium dioxide; this may be printed directly on to the sheet in the form of a lacquer, or printed first on to a fabric in the same manner as the dye; (3) an embossed effect derived from the fabric when this is used as transfer means for the dye. Examples show the process applied to cellulose acetate. According to the Provisional Specification, the process is applicable to sheets of other thermoplastic polymers, e.g. polymerized monoolefinic compounds such as polyvinyl-chloride-acetate, polyethyl acrylate and polymethyl methacrylate, and linear condensation polymers such as nylon.