| 摘要 |
1,129,136. Films. IMPERIAL CHEMCIAL INDUSTRIES Ltd. 5 July, 1966 [30 July, 1965; 24 Jan., 1966], Nos. 32703/65 and 3101/66. Heading B5B. In a process for quenching a molten thermoplastic film which has been freshly extruded on to a moving casting surface and wherein an electrostatic charge is deposited on the upper surface of the cast film from an electrode situated near the film surface, and maintained at a large electrostatic potential difference from the casting surface such that the film is caused to adhere thereto, means are applied to maintain the electrode substantially free from deposits arising from condensation of vapours of volatile matter in the thermoplastic material, or from the decomposition products of such volatile matter. When the electrode is a wire, such means may take the form of (a) a scraper plate having an orifice just sufficient to allow passage of the clean wire, (b), a bath containing a solvent for the deposit, or (c) a method of reducing the contaminant concentration in the vicinity of the electrode. In the case of (a) or (b) the scraper or bath may be passed periodically along the wire, or a continuous electrode wire may be used, which is continuously moved through the scraper or bath. In case (c) an air blower or vacuum device may be used to remove the volatiles from the electrode vicinity. Another method of performing the invention consists in unwinding a clean wire from a reel at one side of the die orifice and winding the slightly contaminated wire on a reel on the other side, at such a speed that the wire accummulates substantially no deposit. Suitable thermoplastics are polyolefine polymers and copolymers polyethyleneterephthalate, polyamides, PVC, polyoxymethylene or poly -3,3-bischloromethyl oxacyclobutane. Volatile materials are U-V and heat stabilizers, and antistatic agents, Polypropylene, containing 2-hydroxy-4-methoxy benzophenone is exemplified. |
