| 摘要 |
1303220 Extruded film W R GRACE & CO 19 April 1971 [23 March 1970] 23783/71 Heading B5A [Also in Divison B2] A multiply plastics film comprising a tubular thermoplastic polymer substrate carrying an outer layer of a composition consisting of, by weight, 0-72% of isotactic polypropylene, 0-50% of polybut-1-ene and 0-50% of atactic polypropylene (the total of the percentages being 100) is produced by depositing a layer of meltextruded outer layer composition over the tubular substrate. The latter, which may be of polyethylene or ethylene/vinyl acetate copolymet, is produced by means of an extruder 9 and die head 11 and is passed in collapsed form through an irradiation vault 14 to cross-link the copolymer. The tubing is then passed through a vacuum chamber 21 and through the opening 26 of a circular cross head die 22 where a molten intermediate coating composition of ethylene/ vinyl acetate copolymer 23 is extruded around and sucked on to the substrate. After water spray cooling at 30, the two-ply film is coated with the outer layer composition by melt extrusion as for the intermediate layer and the product is passed to a water tank at c. 100‹ C. and stretch-oriented by a trapped bubble technique. The multiply tubular film is used in packaging. |
