Patent GB-1071689-A (GB)
Title: Process for producing coloured welded seams
IPC: B29C65/00
Filed: 1964-08-04
Abstract: 1,071,689. Seaming non-metallic sheet material. DEUTSCHE GOLD-UND SILBER SCHEIDEANSTALT VORMALS ROESSLER. Aug. 4, 1964 [July 26, 1963; May 5, 1964], No. 31104/64. Heading B5K. Mono- or poly-chromatic effects of the same or different colours in relation to the material to be welded are produced during the welding of synthetic thermoplastic materials to themselves or to other weldable materials using heated-bar, high-frequency or ultrasonic welding apparatus, by depositing on the welding bars, electrodes or heads, prior to welding, a dyestuff or a dyestuff in a carrier, the dyestuff being transferred to the material to be welded during or by the welding process. The welding bars, electrodes or heads may be formed with surface patterns, e.g. imitation quilting or lozenge patterns, to produce an embossed seam. Different dyestuffs may be deposited on the same or different zones of a welding element or different welding elements of the same apparatus. The welding elements may be preheated before application of the dyestuff thereto, preferably at temperatures up to 150‹ C. The process can be used for joining sheets, foils, artificial leathers, coated materials or laminates. Specified thermoplastic materials are polyethylene, vinyl chloride and vinylidene chloride polymers with or without plasticizers, polyamides and copolymers of vinyl chloride and vinyl acetate. The dyestuffs used must be stable at temperatures up to 200‹ C. which may occur during welding. Specified dyestuffs are inorganic pigments, e.g. oxides, metallic pigments such as aluminium powder or aluminium bronze, carbon blacks or surface-treated pigments, or organic colorants, e.g. chromophthal dyestuffs, perylene pigments and certain azo-dyes. The dyestuffs may be employed in powder or dust form applied to the welding elements by wipers or stamping pads. Preferably, the dyestuffs are mixed with solvents, oil or plasticizers and applied in paste form by wipers, ink rolls, stamping pads or stamping plates. The binder used in the colorant paste is preferably a synthetic thermoplastic material, e.g. a polymer or copolymer which mixes homogeneously with or is identical to the material to be welded and, if required, with the addition of plasticizers, solvents or extenders. For welding polyvinyl chloride the binder may be polyvinyl chloride, vinyl chloride-vinyl acetate copolymers or polymethyl methacrylate. If the dyestuffs are solid under normal conditions transfer to the welding element can be effected from the melt, e.g. if polyethylene is to be welded the dyestuff is transferred to the welding element from a melt containing polyethylene or an ethyleneisobutylene copolymer. The dyestuff may be deposited on the welding element electrostatically by applying a D.C. voltage of 1000-2000 volts to the element and immersing the latter in the dyestuff in powder form. The element may have a portion which contacts a switch to supply a D.C. voltage thereto on the lowering of the element towards a bath containing the dyestuff mixture. Excess powder may be removed by wipers, brushes or rubber or synthetic plastic strippers.