GB953663A - Improvements in or relating to laminates - Google Patents

Abstract

953,663. Laminates. IMPERIAL CHEMICAL INDUSTRIES Ltd. Feb. 26, 1962 [March 13, 1961], No. 9041/61. Heading B5N. A laminate consists of a film of isotactic polypropylene, or a mixture of isotactic polypropylene with a small proportion of polythene, bonded to a film of polyethylene terephthalate. The laminate may be made by extruding a melt of polythene, preferably having a density below 0.93, on to one side of one of the films and pressing the other film against the coated surface. Alternatively other adhesives and/or primer or anchor coats as listed below may be used. The polypropylene film may be pretreated by corona discharge or with ozone, ionizing radiation, flame, or chromic acid in sulphuric acid, to produce superficial oxidation. Either or both films may be unoriented, oriented, or oriented and heat set. The polyethylene terephthalate film may be pre-metallized, preferably on the bonded surface, and care is preferably taken to avoid crystallization of the film. Alternative adhesives usable are solutions of atactic polypropylene in toluene, petroleum ether or other hydrocarbon, solutions of chlorsulphonated polythene, cyclized rubber, vinylidene chloride copolymers, polyvinyl acetate nitrocellulose, rubber, nylon-8, polyethylene terephthalate/sebacate, or butadiene acrylonitrile resins. Primer or anchor coats such as a syrup of melamine-formaldehyde or thermosetting resins such as butylated urea-formaldehyde resin may be used on the polypropylene film, or an alkyl titanate, e.g. tetrabutyl titanate on the polyethylene terephthalate film. Other primer or anchor coats usable are N-alkoxy methyl polyamides, and phenol-, urea-, or melamine-formaldehyde resins. A biaxially oriented polyethylene terephthalate film treated with a primer or anchoring coat may be laminated with a polypropylene film by extruding the latter molten on to the treated film and cooling immediately, as by passing through the nip of cold steel, and silicone rubber faced, rollers, with the polypropylene film in contact with the steel roller. Solutions of static polypropylene used as adhesive may contain carbon black. The products may be used for packaging, the polyethylene terephthalate film being less gas-permeable and, when oriented and heat-set, less shrinkable on heating, than the polypropylene film, but the latter being more readily heat-sealable. Sealed packages may be sterilized at temperatures up to 150‹ C. The inventions claimed in the following Specifications are disclaimed: 868,159. 891,417, 909,947 and 913,289, Specification 715,914 also is referred to.