| 摘要 |
Biaxially oriented polypropylene film with at least one base layer contg. polypropylene has (a) isotactic block length between two structural defects of more than 40 (statistical average), (b) n-heptane-insol. component of the polypropylene with an isotacticity (by <13>C-NMR spectrometry) of at least 95%, (c) mol. wt. ratio Mw/Mn of less than 4 and (d) polypropylene contg. less than 1% n-heptane-soluble component. Also claimed is a process for the prodn. of this film. Pref. the base layer (A) has elastic moduli of more than 2400 and more than 3800 N/mm<2> in the machine direction and transverse direction respectively. (A) contains polypropylene in which the heptane-insol. component has an isotacticity of at least 96%, pref. at least 97%, and a Mw/Mn ratio of less than 3.0, pref. less than 2.7. The film may have outer layer(s) (B) of olefinic polymer on one or pref. both sides and interlayer(s) (C) of olefinic polymer between base and outer layers. Layer (A) contains an antistatic agent, (B) contain(s) lubricants and/or antiblocking agents, and (A), (B) and/or (C) contain neutralising agents and/or stabilisers; interlayer(s) (C) may contain neutralising agents, stabilisers, antistatics and/or antiblocking agents. Layers (B) may or may not be sealable. The total film thickness is 4-100 microns, with the base layer (A) making up 40-60% of this. Alternatively, the film may consist of a single layer. |
