Multi-layer film with improved modulus properties

1. Multi-layer plastic film, comprising

a core layer A comprising at least one copolyester that exhibits residues from

(a) a dicarboxylic acid component comprising

i) 70 mole % to 100 mole % terephthalic acid residues,

ii) 0 mole % to 30 mole % aromatic dicarboxylic acid residues with up to 20 carbon atoms, and

iii) 0 mole % to 10 mole % aliphatic dicarboxylic acid residues with up to 16 carbon atoms, and

(b) a diol component comprising

i) 5 mole % to 50 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues, and

ii) 50 mole % to 95 mole % 1,4-cyclohexanedimethanol residues,

wherein the sum of the mole % of residues i)-iii) of the dicarboxylic acid component amounts to 100 mole % and the sum of the mole % of residues i) and ii) of the diol component amounts to 100 mole %

and wherein the inherent viscosity of the copolyester amounts to 0.50 dL/g to 1.20 dL/g and the copolyester exhibits a glass transition temperature T g from 80° C. to 150° C.,

and wherein said core layer is located between two outer layers B comprising at least one thermoplastic polyurethane, the thermoplastic polyurethane exhibiting a hardness from 45 Shore D to 85 Shore D and being obtainable from

a) one or more linear polyether diols with mean molecular weights from 500 g/mol to 10,000 g/mol, optionally 500 g/mol to 6000 g/mol, and, on average, in each instance at least 1.8 and at most 3.0, optionally 1.8 to 2.2, Tserevitinov-active hydrogen atoms

b) one or more organic diisocyanates,

c) one or more diol chain-extenders with molecular weights from 60 g/mol to 500 g/mol and with, on average, 1.8 to 3.0 Tserevitinov-active hydrogen atoms

in the presence of

d) optionally, one or more catalysts

with addition of

e) optionally, one or more auxiliary substances and additives,

wherein the molar ratio of the NCO groups in b) to the groups in a) and c) that are reactive towards isocyanate amounts to 0.85:1 to 1.2:1, optionally 0.9:1 to 1.1:1, and

said core layer A being located between two outer layers B comprising at least one thermoplastic polyurethane exhibiting a hardness from 45 Shore D to 85 Shoe D.

2. Multi-layer plastic film according to claim 1 , wherein said core layer A comprises at least one polyester or copolyester having an inherent viscosity from 0.50 dL/g to 1.20 dL/g and a glass transition temperature T g from 80° C. to 200° C.

3. Multi-layer plastic film according to claim 1 , wherein the thermoplastic polyurethane exhibits a hardness from 50 Shore D to 80 Shore D.

4. Multi-layer plastic film according to claim 1 , wherein the polyether diol a) used for producing the thermoplastic polyurethane is selected from one or more polyether diols of the group based on 1,4-butanediol units and/or 1,3-propylene glycol units.

5. Multi-layer plastic film according to claim 1 , wherein the organic diisocyanate b) used for producing the thermoplastic polyurethane is selected from one or more isocyanates of the group containing 4,4′-diphenylmethane diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate or 1,6-hexamethylene diisocyanate.

6. Multi-layer plastic film according to claim 1 , wherein the diol chain-extender c) used for producing of the thermoplastic polyurethane is selected from one or more chain-extenders of the group containing 1,4-butanediol, 1,3-propanediol, 1,2-propanediol, 1,2-ethylene glycol, 1,6-hexanediol, 1,4-di(β-hydroxyethyl)hydroquinone or 1,4-di(β-hydroxyethyl)bisphenol A.

7. Multi-layer plastic film according to claim 1 , wherein the thermoplastic polyurethane was produced in a prepolymer process.

8. Multi-layer plastic film according to claim 1 , wherein the diol component of the copolyester comprises 10 mole % to 35 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues and 65 mole % to 90 mole % 1,4-cyclohexanedimethanol residues, 5 mole % to 35 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues and 65 mole % to 85 mole % 1,4-cyclohexanedimethanol residues, or optionally 15 mole % to 30 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues and 70 mole % to 85 mole % 1,4-cyclohexanedimethanol of residues, the sum of the mole % of these two components of the diol component amounting to 100 mole %.

9. Multi-layer plastic film according to claim 1 , wherein the residues from the dicarboxylic acid component of the polyester include 95 mole % to 100 mole % terephthalic acid residues.

10. Multi-layer plastic film according to claim 1 , wherein the film has been co-extruded.

11. Multi-layer plastic film according to claim 1 , comprising a total thickness from 300 μm to 2000 μm, optionally from 400 μm to 1500 μm, or optionally from 500 μm to 1200 μm.

12. Multi-layer plastic film according to claim 1 , wherein the core layer A has a layer thickness from 250 μm to 1600 μm, optionally from 350 μm to 1400 μm, or optionally from 400 μm to 1000 μm.

13. Multi-layer plastic film according to claim 1 , wherein the outer layers B each have a layer thickness from 25 μm to 500 μm, optionally from 30 μm to 300 μm, or optionally from 50 μm to 200 μm.

14. Multi-layer plastic film according to claim 2 , wherein the poly- or copolyester exhibits an inherent viscosity from 0.50 dL/g to 0.80 dL/g.

15. Multi-layer plastic film according to claim 1 , wherein the poly- or copolyester exhibits a glass transition temperature T g from 85° C. to 130° C., optionally from 90° C. to 120° C.

16. Multi-layer plastic film according to claim 1 , wherein the outer layers B each have a layer thickness from 30 μm to 300 μm.

17. Multi-layer plastic film according to claim 1 , wherein the outer layers B each have a layer thickness from 50 μm to 200 μm.

18. Multi-layer plastic film according to claim 1 , wherein the core layer A has a layer thickness from 350 μm to 1400 μm.

19. Multi-layer plastic film according to claim 1 , wherein the core layer A has a layer thickness from 400 μm to 1000 μm.