Patent GB-618230-A (GB)
Title: Process of transfer coating and transfer for use therein
IPC: B44C1/17
Filed: 1945-05-23
Abstract: 618,230. Transfer coatings. SYLVANIA INDUSTRIAL CORPORATION. May 23, 1945, No. 12852. Convention date, May 25, 1944. Drawings to Specification. [Class 140] [Also in Group XVI] Heat and pressure transfers (see Group XVI) are made by coating a flexible backing sheet with a thermoplastic material of softening point below 100‹C. and applying thereover a continuous thermoplastic transfer film having a thermal tacking point higher than the softening point of the intermediate coating. The flexible backing sheet may be fibrous or non-fibrous, specified are paper, fabrics and felts formed of natural or synthetic fibres and films of cellulose acetate, gelatine, casein, diacetylated chitin, zein, alkali-soluble water-insoluble cellulose ethers, hvdrophobic cellulose derivatives, thermoplastic resins and films formed from mixtures of the above materials with synthetic rubber and flexible metal foils. Suitable thermoplastic materials for the intermediate coating include fats, waxes, fatty acids, metallic soaps, natural resins, hydrogenated oils and chlorinated hydrocarbons. They may be used alone, in admixture or together with unvulcanized natural or synthetic rubbers. The coating may be applied to the backing sheet by means of rollers, brushes, calendering machines, spreaders or spray guns. For the transfer film there may be used cellulose acetate and butyrate, nitrocellulose and organic solvent soluble alkyl, carboxy-alkyl and hydroxy-alkyl cellulose ethers and cellulose mixed ether-esters. polymers of vinyl acetate and chloride and vinylidene chloride and after-chlorinated vinyl polymers, polyvinyl formals, acetals and butyrals, polystyrene, coumarone and indene resins, polyethylene resins, resins derived from esters of acrylic and methacrylic acids, and as polymers of these compounds with one another or with aldehydes, resins from dicarboxylic acids and diamines, polybutadiene, oleine polysulsulphides, polyisobutylene and polychloroprene and mixtures thereof. The solvent used for forming the transfer film should not dissolve the intermediate coating. The transfer film may also comprise plasticizers, moisture- and fire-proofing agents, pigments, dyestuffs and effect materials. The transfer film is transferred to the surface to be coated by means of heated platens, calender rolls or drums, preferably at temperatures between 100‹ and 160‹ C. and pressures of 100-300 lbs. square inch. For open mesh fabrics lower pressures, e.g. 5 lbs. square inch, may be used. The backing sheet is stripped off before the intermediate coating has cooled below its softening point and if desired the transfer film polished, printed, decorated, embossed or coated. If desired the intermediate coating may be miscible with the transfer film at the transferring temperature whereby some remains on the transfer when the backing is stripped off and permits the transfer being given a high gloss by polishing and imparts waterproofness to it. The process may be used for coating or decorating paper, e.g. photographs and other documents, or textile fabrics and felts. In examples : (1) Kraft paper was coated with stearic acid in carbon tetrachloride and after drying the intermediate film coated with a copolymer of vinyl chloride or vinyl acetate and methyl methacrylate, tricresyl phosphate and methyl-Cellosolve (R.T.M) acetyl ricinoleate dissolved in ethylene dichloride. The coated sheet was pressed on to printed paper at 154‹C. under 450 lbs. square inch pressure to effect the transfer and the backing sheet stripped off as soon as it was removed from the press. The coated printed paper was given a smooth glossy surface by pressing against a heated polished metal roller. If desired the intermediate coating may comprise aluminium stearate dissolved in naphtha or other petroleum solvent. In (2) Cellophane (R.T.M.) sheet was given an intermediate coating of either (a) molten paraffin wax and unvulcanized rubber; or (b) chlorinated diphenyl dissolved in carbon tetrachloride; or (c) a wax-like polymer of ethylene glycol. After rapid cooling the coated sheet was coated with polyvinyl butyral and dibutyl sebacate in acetone and butyl alcohol. The transfer film was applied to a textile fabric at 130‹C. and 300 lbs. square inch pressure and the cellophane film stripped from the composite material whilst the intermediate coating was still fluid. The coated fabric was polished by passage through hot rolls coated with a film of regenerated cellulose. In (3) paper was coated with ozokerite wax and then with a transfer film of cellulose acetate-butyrate plasticized with dibutyl phthalate. Transferring was carried out at 135‹C. under 300 lbs. square inch pressure, the composite article cooled to 60‹C. and the backing sheet stripped off.