Multilayer oriented film
A multilayer oriented film comprising at least one layer (a) comprising one or more polyesters and/or copolyesters characterized by a % of crystallinity higher than 15, an adjacent layer (b) comprising one or more polyolefin-based adhesive resins, and a layer (c) comprising one or more co-polyesters characterized by a % of crystallinity lower than 15, is positioned between said two layers (a) and (b) in such a way that one of the two principal surfaces of layer (c) is directly adhered to layer (a) and the other is directly adhered to layer (b). The presence of a co-polyester layer (c) of relatively low % crystallinity positioned between (co)polyester layer (a) and adhesive layer (b) remarkably increases the bond between the two layers (a) and (b) and prevents delamination problems in the oriented structure.
1. A multilayer oriented film comprising:
at least one layer (a) comprising one or more homo-polyesters and/or copolyesters characterized by a % of crystallinity higher than 15,
layer (b) comprising one or more polyolefin-based adhesive resins selected from one or more of ethylene-unsaturated acid copolymers, ethylene-unsaturated ester copolymers, modified polyethylene homopolymer, modified ethylene-α-olefin copolymers, modified ethylene-vinyl acetate copolymers, modified ethylene-alkyl(meth)acrylate copolymers, modified ethylene-(meth)acrylic acid copolymers, modified ethylene-propylene copolymer, modified ethylene-propylene-α-olefin co-polymers, and
a layer (c) comprising one or more co-polyesters characterized by a % of crystallinity lower than 15, is positioned between the two layers (a) and (b) in such a way that one of the two principal surfaces of layer (c) is directly adhered to layer (a) and the other is directly adhered to layer (b),
an outer layer (d) which comprises one or more heat-sealable polyolefins selected from one or more of ethylene homo-polymers, heterogeneous or homogeneous ethylene-α-olefin copolymers, ethylene-vinyl acetate co-polymers, ethylene-(C 1 -C 4 ) alkyl acrylate or methacrylate co-polymers, ethylene-acrylic acid co-polymers, and ethylene-methacrylic acid co-polymers,
a core gas-barrier layer (e) between layers (b) and (d) comprising ethylene/vinyl alcohol copolymer,
wherein layers (a), (b), (c), (d), and (e) are fully coextruded together.
2. The multi-layer film of claim 1 which is biaxially oriented.
3. The multi-layer film of claim wherein layer (a) is an outer layer of the film.
4. The oriented film of claim 1 wherein the % of crystallinity of the (co)polyesters employed for layer (a) is higher than 20.
5. The oriented film of claim 1 wherein the % of crystallinity of the co-polyesters employed for layer (c) is lower than 12.
6. The multi-layer film of claim 1 wherein the homo-polyester and/or co-polyester resins of layer (a) have a Tm higher than 220° C.
7. The multi-layer film of claim 1 wherein the homo-polyester and/or co-polyester resins of layer (a) have a Vicat softening temperature which is higher than 110° C.
8. The multi-layer film of claim 1 wherein the co-polyester resins of layer (c) have either no detectable Tm or a Tm lower than 200° C.
9. The multi-layer film of claim 1 wherein the co-polyester resins of layer (c) have a Vicat softening point lower than 110° C.
10. The multi-layer film of claim 1 which is heat-shrinkable.
11. The multi-layer film of claim 1 which is heat-set.
12. The multi-layer film of claim 1 wherein the one or more co-polyesters of layer (c) comprises glycolised co-polyester PETG.
13. A packaged food comprising a package comprising the film of claim 1 enclosing a food.
14. A process of making a film comprising:
coextruding together layers (a), (b), (c), (d), and (e) to form a fully coextruded film, wherein
layer (a) comprises one or more homo-polyesters and/or copolyesters characterized by a % of crystallinity higher than 15,
layer (b) comprises one or more polyolefin-based adhesive resins selected from one or more of ethylene-unsaturated acid copolymers, ethylene-unsaturated ester copolymers, modified polyethylene homopolymer, modified ethylene-α-olefin copolymers, modified ethylene-vinyl acetate copolymers, modified ethylene-alkyl (meth)acrylate copolymers, modified ethylene-(meth)acrylic acid copolymers, modified ethylene-propylene copolymer, modified ethylene-propylene-α-olefin co-polymers,
layer (c) comprises one or more co-polyesters characterized by a % of crystallinity lower than 15, wherein layer (c) is positioned between layers (a) and (b) in such a way that one of the two principal surfaces of layer (c) is directly adhered to layer (a) and the other is directly adhered to layer (b),
layer (d) is an outer layer which comprises one or more heat-sealable polyolefins selected from one or more of ethylene homo-polymers, heterogeneous or homogeneous ethylene-α-olefin copolymers, ethylene-vinyl acetate co-polymers, ethylene-(C 1 -C 4 ) alkyl acrylate or methacrylate co-polymers, ethylene-acrylic acid co-polymers, and ethylene-methacrylic acid co-polymers, and
layer (e) is a core gas-barrier layer between layers (b) and (d) comprising ethylene/vinyl alcohol copolymer.
15. The process of claim 14 further comprising biaxially orienting the fully coextruded film.
16. The process of claim 14 further comprising heat-setting the biaxially oriented film.
17. The process of claim 14 wherein the % of crystallinity of the (co)polyesters employed for layer (a) is higher than 20 and the % of crystallinity of the co-polyesters employed for layer (c) is lower than 12.
18. The process of claim 14 wherein the homo-polyester and/or co-polyester resins of layer (a) have a Tm higher than 220° C. and the co-polyester resins of layer (c) have either no detectable Tm or a Tm lower than 200° C.
19. The process of claim 14 wherein the homo-polyester and/or co-polyester resins of layer (a) have a Vicat softening temperature which is higher than 110° C. and the co-polyester resins of layer (c) have a Vicat softening point lower than 110° C.
20. The process of claim 14 wherein the one or more co-polyesters of layer (c) comprises glycolised co-polyester PETG.