Improvements relating to the flame treatment of polyvinyl fluoride film and shaped fibre-reinforced polyester structures bonded with such treated film

摘要

999,055. Treating polyvinyl fluoride film; mould linings. E. I. DU PONT DE NEMOURS & CO. July 17, 1963 [July 18, 1962]. No. 28352/63. Drawings to Specification. Headings B5A and B5B. A surface of a polyvinyl fluoride film is continuously brought into intimate contact with a moving, relatively highly thermally conductive solid surface maintained at a temperature of 40‹ to 135‹ C., whereby the film passing thereover is heated to the temperature of the moving surface and the film while in contact with this surface is passed through the secondary envelope of a steady flame of a burner disposed parallel to the film and transversely to its direction of travel. The flame is free from yellow luminosity and is supplied with a gaseous mixture consisting of a paraffinic or olefinic hydrocarbon fuel, preferably propane, oxygen and nitrogen, the " fuel equivalence ratio " of the gaseous mixture being 10À5 to 1À20 and its oxygen ratio 0À15 to 0À25. The distance from the free surface of the film to the discharge opening or openings of the burner is greater than the length of the unimpeded primary envelope of the flame, and the film is exposed to the flame for 0À01 to 0À5 second. The film is maintained in contact with the moving surface for a time after it has left the flame. The " fuel equivalence ratio " is defined as the ratio of the amount of hydrocarbon fuel present in the gaseous mixture supplied to the burner to the amount of hydrocarbon fuel necessary for complete stoichiometric combustion. The " oxygen ratio" is the ratio of the amount of oxygen present in the gaseous mixture supplied to the burner to the total amount of non-fuel components in the mixture, said components including chiefly oxygen and nitrogen. The " primary envelope" of the flame is defined as the luminous, pale blue inner portion of the flame nearer the discharge opening of the burner and the " secondary envelope" of the flame is defined as the fainter, less luminous sheath surrounding the primary envelope. Fibre-reinforced polyester structures clad with polyvinyl films treated by the process of the invention may be produced by moulding and curing a mixture comprising at least one linear polymeric ester containing recurring ethylenic unsaturation, at least one addition-polymerizable ethylenically unsaturated monomer, and reinforcing fibres, using as a mould release sheet a polyvinyl fluoride film of which at least the surface in contact with the mixture has been treated by the process of the invention. Specification 845,634 is referred to.