| abstract |
(57) [Summary] [Objective] To provide a polypropylene composite film having excellent heat sealing properties such as low temperature heat sealing property and heat sealing strength, hot tack property and blocking resistance. [Structure] (A) an unstretched crystalline polypropylene layer, (B) A polypropylene composite film comprising a propylene / 1-butene random copolymer layer, wherein the copolymer (B) contains (1) 1-butene structural unit in an amount of 5 to 50 mol%. (2) The intrinsic viscosity is 0.1 to 5 dl / g, and (3) The molecular weight distribution (Mw / Mn) is 3 or less, and (4) B value is 1.0 to 1.5, preferably 1.0 to 1.3. More preferably (5) the melting point is 60 to 140 ° C., and the content of the 1-butene structural unit satisfies the melting point or the crystallinity and a specific relational expression. The copolymer (B) can be produced using a specific metallocene catalyst. |