| abstract |
PURPOSE:To obtain a biaxially stretched polypropylene film which is good in transparency, rigidity, impact resistance and thermo-contracting resistance, by a method in which a polymer having a specific ethylene content and a specific isotactic value is melted and extruded into a sheet, and the sheet is preheated, vertically stretched and then biaxially stretched sidewards. CONSTITUTION:A polypropylene having an ethylene content (Ec) of 0.1-2.0mol% and an isotactic value (Iso) to meet the relationship Iso>=-5Ec+96.3 in the case of 0.1<=Ec<=0.3 (mol%) and also Iso>=-0.67Ec+95.0 in the case of 0.3<E<=2.0 (mol%) is melted and extruded through a T-die into a sheet form, and the sheet is solidified by cooling, preheated, vertically stretched, and then biaxially stretched sidewards to obtain the aimed biaxially stretched polypropylene film. |