| 摘要 |
1398853 Polyester films; laminates IMPERIAL CHEMICAL INDUSTRIES Ltd 17 Nov 1972 [17 Nov 1971] 53299/71 Headings B5B and B5N A polymeric film of composite structure comprises at least one region of linear polyester co-extruded with at least one other separate region comprising re-work quality linear polyester, the region of the latter being restricted to a part of the film where its properties do not impair the suitability of the film for its intended end use. Polyethylene terephthalate is the preferred polyester. Rework quality polyester may be confined to edge margins of the film which are then trimmed, yielding a film suitable for coating with a photographic emulsion, or a core layer thereof may be located between surface skins of fresh polyester, which may be coated with a metallic layer or a magnetic coating, or a two-layer laminate may be made, one layer of fresh polyester and the other of rework quality polyester. Examples illustrate the production of polyethylene terephthalate films by melt-extrusion followed by quenching, longitudinal stretching between slow and fast rollers at 80‹ C. to a draw ratio of 3À0: 1, followed by transverse stretching by tentering at 100‹ C. to the same draw ratio, followed by heat-setting at 200‹ C. while shrinkage of the film is restrained.
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