Composite film

Abstract

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 paraxylylenediamine (of which the content is not more than 30% (mol) on the basis of the total amount of metaxylylenediamine 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.

What is claimed is: 
     
       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.   
     
     
       2. The composite film according to claim 1, wherein the .[.gas.]. .Iadd.oxygen .Iaddend.transmission rate is not more than 30 ml./m. 2  24 hr. atm. 
     
     
       3. The composite film according to claim 1, wherein the thickness of the biaxially drawn film is 5 to 50μ. 
     
     
       4. The composite film according to claim 1, wherein the thickness of the composite film is 6 to 200μ. 
     
     
       5. The composite film according to claim 1, wherein the melting point of the thermoplastic resin is 50 to 170° C. 
     
     
       6. The composite film according to claim 1, wherein the thermoplastic resin is a polyolefin resin. 
     
     
       7. The composite film according to claim 1, which is heat sealable at a temperature of 70 to 160° C. 
     
     
       8. The composite film according to claim 1, wherein the thickness of the thermoplastic resin is about 5 to 100μ. 
     
     
       9. The composite film according to claim 1, wherein the polyamide has a relative viscosity of about 2.0 to 4.0. 
     
     
       10. The composite film according to claim 1, wherein the polyamide is a homopolymer selected from the group consisting of polymetaxylylene adipamide polymetaxylylene sebacamide and polymetaxylylene suberamide. 
     
     
       11. The composite film of claim 1, wherein the polyamide is selected from the group consisting of copolymers of metaxylylene/paraxylylene adipamide, metaxylylene/paraxylylene pimelamide, metaxylylene/paraxylylene sebacamide and metaxylylene/paraxylylene azelamide.