Composite film

Claim 1

A composite film comprising (A) a biaxially drawn film of a polyamide containing in the molecule not less than 70% (mol) of the repeating unit consisting of metaxylylenediamine or its mixture with paraxylyenediamine, wherein the paraxylylenediamine content is not more than 30% (mol) on the basis of the total amount of methaxylylenediamine and paraxylylenediamine, and an α,ω-aliphatic dicarboxylic acid having 6 to 10 carbon atoms and (B) a layer of a thermoplastic resin having a melting point or a softening point at least 50° C. below the melting point or the softening point of the polyamide provided on at least one surface of the biaxially drawn film; the biaxially drawn film having the following physical constants: (1) .[.Gas.]. .Iadd.Oxygen .Iaddend.permeability constant (at 30° C.): not more than 9×10 - 13 ml. cm./cm. 2 sec. cm. Hg; (2) Plane orientation index: not less than 0.025; (3) Degree of balance: not more than 0.045; (4) Breaking strength: not less than 10 kg./mm. 2 in machine and transverse directions; (5) Breaking elongation: 30 to 150% in machine and transverse directions; (6) Yield strength: not less than 5 kg./mm. 2 in machine and transverse directions; and (7) Yield elongation: 2 to 6% in machine and transverse directions; and the composite film having the following physical constant: (8) .[.Gas.]. .Iadd.Oxygen .Iaddend.transmission rate (at 30° C.): not more than 50 ml./m. 2 24 hr. atm.