Patent GB-1033959-A (GB)
Title: Self-sealing article and process
IPC: B29C48/09
Filed: 1963-10-02
Abstract: 1,033,959. Heat-deformable films; laminates and laminating. RAYCHEM CORPORATION. Oct. 2, 1963 [Oct. 4, 1962], No. 38857/63. Headings B5B and B5N. In a process for the manufacture of an article having elastic memory, a first portion that is relatively fusible is intimately bonded to a second portion that is also relatively fusible to form a single integral structure, the second portion is then rendered relatively infusible, while maintaining the first portion relatively fusible, and the property of elastic memory is imparted to the article. The " relatively infusible portion " is defined as a portion that does not become substantially fluid at a temperature sufficient to render the " relatively fusible portion " substantially fluid. The relatively fusible first portion and the second portion may be bonded together by fusion, e.g. by compound extrusion or by chemical means. The second portion may be rendered relatively infusible by cross-linking e.g. by irradiation or by chemical means, and in one embodiment, may be cross-linked to a point where it is substantially infusible, i.e. cross-linked to a point where it decomposes before melting. The two portions may be thermoplastic polymers, e.g. modified neoprene and silicone rubbers, polyethylene, polypropylene, nylon, fluorinated ethylene and propylene polymers, polyvinyl chloride, polytetrafluorethylene, polyvinylidene fluoride and acrylic polymers. The first and second portions may differ chemically or may be the same compound differing in molecular weight characteristics. The relative difference in fusibility, resulting from cross-linking, may be controlled by addition of cross-linking agents to the portion to be made relatively infusible, or by addition of thermal anti-oxidants or crosslinking inhibitors to the portion to remain relatively fusible. In a modification of the process, the second portion is already relatively infusible when it is bonded to the first portion. The property of elastic memory is imparted to the relatively infusible portion or to both portions, and the article, e.g. a tube or flat film or tape, may be made heat-shrinkable or heat-expandible. In one embodiment (Fig 1 and 2) (not shown), the article 1 comprises a tube formed by compound extrusion of relatively infusible portion 5 and relatively fusible portion 6. The compound tube is extruded from 4 and passed, in chamber 7, over rollers 9 wherein it is subjected to an electron beam from electron generator 8. After irradiation, the tube is passed to an expanding apparatus wherein a pressure differential, e.g. positive pressure or vacuum is exerted on the tube as it travels between rollers 10, 11. After leaving heating medium 13, the tube is quenched by cooling die 14. The articles may be used for laminating, sealing of containers, encapsulating or covering tubes, and may be provided with a reinforcing material such as a braid or knit fabric. On application of heat, the relatively fusible portion is urged by the heat-deformable relatively infusible portion towards the article to be covered and forms a seal therewith. The fusible portion may contain, or be coated with, agents which bond with the article to be covered. In an example, a composite tubular film comprising relatively infusible outer, and relatively fusible inner portions of polyethylene is extruded, irradiated, and expanded according to the process disclosed in Specification 990,235.