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A breathable, heat-sealable composite film comprising first and second layers of polymeric material wherein (i) the polymeric material of the first layer comprises copolyester comprising monomeric units derived from one or more diol(s); one or more dicarboxylic acid(s); and one or more poly(alkylene

A breathable, heat-sealable composite film comprising first and second layers of polymeric material wherein (i) the polymeric material of the first layer comprises copolyester comprising monomeric units derived from one or more diol(s); one or more dicarboxylic acid(s); and one or more poly(alkylene oxide)glycol(s); and (ii) the second layer is a heat-sealable polymeric layer, and a process for the production thereof.

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1. A breathable, heat-sealable composite film comprising first and second layers of polymeric material wherein: (i) the polymeric material of the first layer comprises a copolyester comprising monomeric units derived from one or more diol(s); one or more dicarboxylic acid(s), wherein at least one of

1. A breathable, heat-sealable composite film comprising first and second layers of polymeric material wherein: (i) the polymeric material of the first layer comprises a copolyester comprising monomeric units derived from one or more diol(s); one or more dicarboxylic acid(s), wherein at least one of said one or more dicarboxylic acids is an aromatic acid; and one or more poly(alkylene oxide)glycol(s);(ii) the second layer is a heat-sealable polymeric layer;(iii) the composite film has an elongation to break of less than 250%;(iv) the poly(alkylene oxide)glycol of the first layer constitutes in the range of 10 to 40 mol % of all diol and glycol monomeric units of the first layer;wherein the polymeric material of the first layer comprises greater than 50% of the copolyester by weight, relative to the total amount of polymeric material in the first layer, and wherein the heat-sealable polymeric layer is formed by coating the heat-sealable polymer onto the first layer, conducted after the first layer is stretched and subsequently heat-set; and wherein:(a) the copolyester of the first layer has a glass transition temperature (Tg) of at least 0° C. and no more than 60° C.; or(b) the polymeric material of the heat-sealable second layer is derived from a first aromatic dicarboxylic acid, a low molecular weight aliphatic diol, a poly(alkylene oxide)glycol, and a further dicarboxylic acid which imparts heat-sealability. 2. The film according to claim 1 wherein the copolyester of the first layer has a glass transition temperature (Tg) of at least 0° C. and no more than 60° C. 3. The film according to claim 1 wherein the copolyester of the first layer has a glass transition temperature (Tg) of at least 0° C. and no more than 60° C. and the polymeric material of the heat-sealable second layer is derived from a first aromatic dicarboxylic acid, a low molecular weight aliphatic diol, a poly(alkylene oxide)glycol, and a further dicarboxylic acid which imparts heat-sealability. 4. A breathable, heat-sealable composite film comprising first and second layers of polymeric material wherein: (i) the polymeric material of the first layer comprises a copolyester comprising monomeric units derived from one or more diol(s); one or more dicarboxylic acid(s), wherein at least one of said one or more dicarboxylic acids is an aromatic acid; and one or more poly(alkylene oxide)glycol(s);(ii) the second layer is a heat-sealable polymeric layer;(iii) the composite film has an elongation to break of less than 250%;(iv) the poly(alkylene oxide)glycol of the first layer constitutes in the range of 10 to 40 mol % of all diol and glycol monomeric units of the first layer; and(v) the copolyester of the first layer has a glass transition temperature (Tg) of at least 0° C. and no more than 60° C.;wherein the polymeric material of the first layer comprises greater than 50% of the copolyester by weight, relative to the total amount of polymeric material in the first layer, and wherein the composite film exhibits a haze of less than 10%; and wherein either:(a) the heat-sealable second layer is derived from a first dicarboxylic acid, a first low molecular weight diol, and either a second dicarboxylic acid or a second low molecular weight diol; or(b) the polymeric material of the heat-sealable second layer is derived from a first aromatic dicarboxylic acid, a low molecular weight aliphatic diol, a poly(alkylene oxide)glycol, and a further dicarboxylic acid which imparts heat-sealability; or(c) the heat-sealable second layer comprises a copolyester derived from an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid; or(d) the heat-sealable second layer comprises ethylene vinyl acetate (EVA). 5. The film according to claim 1 or claim 4 wherein the film is permeable to gaseous water. 6. The film according to claim 1 or claim 4 wherein the poly(alkylene oxide)glycol is selected from the group consisting of polyethylene glycol (PEG), polypropylene glycol (PPG) and poly(tetramethylene oxide)glycol (PTMO). 7. The film according to claim 1 or claim 4 wherein the poly(alkylene oxide)glycol is polyethylene glycol. 8. The film according to claim 1 or claim 4 wherein the average molecular weight of the poly(alkylene oxide)glycol is from about 400 to about 10000. 9. The film according to claim 1 or claim 4 wherein the average molecular weight of the poly(alkylene oxide)glycol is from about 400 to about 4500. 10. The film according to claim 1 or claim 4 wherein the copolyester of the first layer comprises terephthalic acid. 11. The film according to claim 1 or claim 4 wherein the copolyester of the first layer comprises an aliphatic diol. 12. The film according to claim 1 or claim 4 wherein the copolyester of the first layer comprises ethylene glycol. 13. The film according to claim 1 or claim 4 wherein said one or more dicarboxylic acid(s) comprises a first aromatic dicarboxylic acid and a second dicarboxylic acid. 14. The film according to claim 13 wherein said first aromatic dicarboxylic acid is terephthalic acid. 15. The film according to claim 14 wherein said second dicarboxylic acid is an aliphatic dicarboxylic acid. 16. The film according to claim 15 wherein said second dicarboxylic acid is adipic acid or azelaic acid. 17. The film according to claim 14 wherein said second dicarboxylic acid is a sulphonated aromatic dicarboxylic acid. 18. The film according to claim 17 wherein said second dicarboxylic acid is sodium sulpho-isophthalic acid. 19. The film according to claim 13 wherein the first dicarboxylic acid constitutes from 50 to 100 mol % of all dicarboxylic acid monomeric units, and the second dicarboxylic acid constitutes from 0 to 50 mol % of all dicarboxylic acid monomeric units. 20. The film according to claim 1 or claim 4 wherein the thickness of the first layer is in the range of from about 0.5 to about 300 μm. 21. The film according to claim 1 or claim 4 wherein the heat-sealable second layer is derived from a first dicarboxylic acid, a first low molecular weight diol, and either a second dicarboxylic acid or a second low molecular weight diol. 22. The film according to claim 21 wherein the heat-sealable second layer is a copolyester derived from ethylene glycol, terephthalic acid and isophthalic acid. 23. The film according to claim 21 wherein the heat-sealable second layer is a copolyester derived from terephthalic acid, ethylene glycol and 1,4-cyclohexanedimethanol. 24. The film according to claim 1 or claim 4 wherein the polymeric material of the heat-sealable second layer is derived from a first aromatic dicarboxylic acid, a low molecular weight aliphatic diol, a poly(alkylene oxide)glycol, and a further dicarboxylic acid which imparts heat-sealability. 25. The film according to claim 24 wherein said first aromatic dicarboxylic acid is terephthalic acid, and/or said low molecular weight aliphatic diol is ethylene glycol, and/or said further dicarboxylic acid which imparts heat-sealability is isophthalic acid. 26. The film according to claim 24 wherein said first dicarboxylic acid constitutes from 50 to 90 mol % of all dicarboxylic acid monomeric units. 27. The film according to claim 24 wherein said low molecular weight diol constitutes from 60 to 90 mol % of all diol and glycol monomeric units. 28. The film according to claims 24 wherein the poly(alkylene oxide)glycol is poly(ethylene oxide)glycol. 29. The film according to claim 1 or claim 4 wherein the heat-sealable second layer comprises a copolyester derived from an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid. 30. The film according to claim 29 wherein the aromatic dicarboxylic acid from which the copolyester of the heat-sealable second layer is derived is terephthalic acid. 31. The film according to claim 29 wherein the aliphatic dicarboxylic acid from which the copolyester of the heat-sealable second layer is derived is selected from sebacic acid, adipic acid and azelaic acid. 32. The film according to claim 29 wherein the concentration of the aliphatic dicarboxylic acid in the copolyester of the heat-sealable second layer is in the range of 20 to 55 mol %, based on the dicarboxylic acid components of the copolyester of the heat-sealable second layer. 33. The film according to claim 29 wherein the concentration of the aliphatic dicarboxylic acid in the copolyester of the heat-sealable second layer is in the range of 30 to 50 mol %, based on the dicarboxylic acid components of the copolyester of the heat-sealable second layer. 34. The film according to claim 29 wherein the concentration of the aliphatic dicarboxylic acid in the copolyester of the heat-sealable second layer is in the range of 35 to 45 mol %, based on the dicarboxylic acid components of the copolyester of the heat-sealable second layer. 35. The film according to claim 29 wherein the copolyester of the heat-sealable second layer is: (i) a copolyester of azelaic acid, terephthalic acid and an aliphatic glycol; or(ii) a copolyester of adipic acid, terephthalic acid and an aliphatic glycol; or(iii) a copolyester of sebacic acid, terephthalic acid and an aliphatic glycol. 36. The film according to claim 29 wherein the copolyester of the heat-sealable second layer is: (i) a copolyester of azelaic acid, terephthalic acid and ethylene glycol; or(ii) a copolyester of adipic acid, terephthalic acid and ethylene glycol; or(iii) a copolyester of sebacic acid, terephthalic acid and butylene glycol. 37. The film according to claim 29 wherein the copolyester of the heat-sealable second layer is a copolyester of sebacic acid, terephthalic acid and butylene glycol. 38. The film according to claim 37 wherein the relative molar ratios of sebacic acid:terephthalic acid:butylene glycol are 45-55:55-45:100. 39. The film according to claim 37 wherein the relative molar ratios of sebacic acid:terephthalic acid:butylene glycol are 50:50:100. 40. The film according to claim 29 wherein the copolyester of the heat-sealable second layer is a copolyester of azelaic acid, terephthalic acid and ethylene glycol. 41. The film according to claim 40 wherein the relative molar ratios of azelaic acid:terephthalic acid:ethylene glycol are 40-50:60-50:100. 42. The film according to claim 40 wherein the relative molar ratios of azelaic acid:terephthalic acid:ethylene glycol are 45:55:100. 43. The film according to claim 1 or claim 4 wherein the heat-sealable second layer comprises ethylene vinyl acetate (EVA). 44. The film according to claim 1 or claim 4 wherein the thickness of the second layer is in the range of from about 0.05 to about 20 μm. 45. The film according to claim 1 or claim 4 wherein the composite film exhibits a water vapour transmission rate (WVTR) of at least 60 g/m2/day. 46. A method of packaging cut plants, comprising heat-sealing the plants within a container comprising the composite film according to claim 1 or claim 4. 47. The method according to claim 46 wherein the container further comprises a receptacle for the cut plants, wherein the film forms a lid for the receptacle, and wherein the step of heat-sealing comprises heat-sealing the film to the receptacle. 48. A sealed container comprising a receptacle containing cut plant(s), and a lid formed from the composite film according to claim 1 or claim 4. 49. A breathable, heat-sealable composite film comprising first and second layers of polymeric material wherein: (i) the polymeric material of the first layer comprises a copolyester comprising monomeric units derived from one or more diol(s); one or more dicarboxylic acid(s), wherein at least one of said one or more dicarboxylic acids is an aromatic acid; and one or more poly(alkylene oxide)glycol(s);(ii) the second layer is a heat-sealable polymeric layer;(iii) the composite film has an elongation to break of less than 250%; and(iv) the poly(alkylene oxide)glycol of the first layer constitutes in the range of 10 to 40 mol % of all diol and glycol monomeric units of the first layer;wherein the polymeric material of the first layer comprises greater than 50% of the copolyester by weight, relative to the total amount of polymeric material in the first layer, and wherein the composite film exhibits a haze of less than 10%; andwherein the polymeric material of the heat-sealable second layer is derived from a first aromatic dicarboxylic acid, a low molecular weight aliphatic diol, a poly(alkylene oxide)glycol, and a further dicarboxylic acid which imparts heat-sealability. 50. The film according to claim 49 wherein said first aromatic dicarboxylic acid is terephthalic acid, and/or said low molecular weight aliphatic diol is ethylene glycol, and/or said further dicarboxylic acid which imparts heat-sealability is isophthalic acid, and/or said poly(alkylene oxide)glycol is poly(ethylene oxide)glycol. 51. The film according to claim 49 or 50 wherein said first dicarboxylic acid constitutes from 50 to 90 mol % of all dicarboxylic acid monomeric units and/or said low molecular weight diol constitutes from 60 to 90 mol % of all diol and glycol monomeric units.