Formable polyester films

Abstract

A formable biaxially-oriented film includes a first layer. The first layer includes from about 10 to about 90 wt. % crystalline polyester and from about 10 to about 90 wt. % of a formability enhancer to assist in increasing the polymeric chain flexibility. The formability enhancer has a melting point less than about 230° C. The film has a MD and a TD Young's Modulus of at least 10% lower than a crystalline polyester film in the absence of the formability enhancer. The film may further include a second layer, which includes an amorphous copolyester. The second layer may be adjacent to or attached to the first layer.

We claim: 
     
         1 . A formable biaxially-oriented film, the film comprising:
 a first layer comprising from about 10 to about 90 wt. % crystalline polyester and from about 10 to about 90 wt. % of a formability enhancer to assist in increasing the polymeric chain flexibility, the formability enhancer having a melting point less than about 230° C.,   wherein the film has a MD and a TD Young's Modulus of at least 10% lower than a crystalline polyester film in the absence of the formability enhancer.   
     
     
         2 . The formable film of  claim 1 , wherein the formability enhancer is a homopolymer or copolymer comprising repeating units of trimethylene terephthalate. 
     
     
         3 . The formable film of  claim 1 , wherein the formability enhancer is a homopolymer or copolymer comprising repeating units of butylene terephthalate. 
     
     
         4 . The formable film of  claim 1 , wherein the formability enhancer is a copolyester elastomer. 
     
     
         5 . The formable film of  claim 1 , wherein the formability enhancer is a polyester comprising repeating units of at least one aliphatic dicarboxylic acid or a polyester having more than four methylene groups from aliphatic diols within repeating units. 
     
     
         6 . The formable film of  claim 1 , wherein the film has a MD and TD Young's Modulus of at least 20% lower than a crystalline polyester film in the absence of the formability enhancer. 
     
     
         7 . The formable film of  claim 6 , wherein the film has a MD and a TD Young's Modulus of at least 30% lower than a crystalline polyester film in the absence of the formability enhancer. 
     
     
         8 . The formable film of  claim 7 , wherein the film has a MD and a TD Young's Modulus of at least 40% lower than a crystalline polyester film in the absence of the formability enhancer. 
     
     
         9 . The formable film of  claim 8 , wherein the film has a MD and a TD Young's Modulus of at least 50% lower than a crystalline polyester film in the absence of the formability enhancer. 
     
     
         10 . The formable film of  claim 1 , wherein the crystalline polyester includes homopolyesters or copolyesters of polyethylene terephthalate, polyethylene naphthalate, polyethylene terephthalate-co-isophthalate copolymer, polyethylene terephthalate-co-naphthalate copolymer, polycyclohexylene terephthalate, polyethylene-co-cyclohexylene terephthalate, polyether-ester block copolymer, ethylene glycol or terephthalic acid-based polyester homopolymers and copolymers, or combinations thereof. 
     
     
         11 . The formable film of  claim 1 , wherein the crystalline polyester includes homopolyesters or copolyesters of polyethylene terephthalate. 
     
     
         12 . The formable film of  claim 1 , wherein the thickness of the film is from about 2 μm to about 350 μm. 
     
     
         13 . The formable film of  claim 12 , wherein the thickness of the film is from about 3 μm to about 50 μm. 
     
     
         14 . The formable film of  claim 13 , wherein the thickness of the film is from about 10 μm to about 25 μm. 
     
     
         15 . A formable biaxially-oriented film, the film comprising:
 a first layer comprising from about 10 to about 90 wt. % crystalline polyester and from about 10 to about 90 wt. % of a formability enhancer to assist in increasing the polymeric chain flexibility, the formability enhancer having a melting point less than about 230° C.; and   a second layer comprising an amorphous copolyester, the second layer being adjacent to the first layer,   wherein the film has a MD and a TD Young's Modulus of at least 10% lower than a crystalline polyester film in the absence of the formability enhancer.   
     
     
         16 . The formable film of  claim 15 , wherein the amorphous copolyester includes isophthalate modified copolyesters, sebacic acid modified copolyesters, diethyleneglycol modified copolyesters, triethyleneglycol modified copolyesters, cyclohexanedimethanol modified copolyesters, or combinations thereof. 
     
     
         17 . The formable film of  claim 15 , further including a third layer, the third layer comprising an amorphous copolyester, the first layer being attached to and located between the second and third layers. 
     
     
         18 . The formable film of  claim 15 , further including a third layer, the third layer being a metallic barrier layer, the first layer being attached to and located between the second and third layers. 
     
     
         19 . The formable film of  claim 18 , wherein the metallic barrier layer includes titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, gold, palladium or combinations thereof. 
     
     
         20 . The formable film of  claim 19 , wherein the metallic barrier layer includes aluminum. 
     
     
         21 . The formable film of  claim 15 , wherein the formability enhancer is a homopolymer or copolymer comprising repeating units of trimethylene terephthalate. 
     
     
         22 . The formable film of  claim 15 , wherein the formability enhancer is a homopolymer or copolymer comprising repeating units of butylene terephthalate. 
     
     
         23 . The formable film of  claim 15 , wherein the film has a MD and a TD Young's Modulus of at least 20% lower than a crystalline polyester film in the absence of the formability enhancer. 
     
     
         24 . The formable film of  claim 23 , wherein the film has a MD and a TD Young's Modulus of at least 40% lower than a crystalline polyester film in the absence of the formability enhancer. 
     
     
         25 . A formable biaxially-oriented film, the film comprising:
 at least one layer comprising from about 10 to about 90 wt. % crystalline polyester and from about 10 to about 90 wt. % of a formability enhancer to assist in increasing the polymeric chain flexibility, the formability enhancer having a melting point less than about 230° C.,   wherein the film has a composite MD and TD Young's Modulus of less than about 500 kg/mm 2 .   
     
     
         26 . The formable film of  claim 25 , wherein the film has a composite MD and TD Young's Modulus of less than about 475 kg/mm 2 . 
     
     
         27 . The formable film of  claim 26 , wherein the film has a composite MD and TD Young's Modulus of less than about 450 kg/mm 2 .