Breathable composite polymeric films

A film according to claim 49 wherein the polyester of substrate layer (A) is a copolyester comprising monomeric units derived from a diol, a first dicarboxylic acid and a second dicarboxylic acid.

A film according to claim 49 wherein the polyester of substrate layer (A) is a 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).

A film according to any preceding claim wherein primer coating layer (B) is derived from a composition comprising a sulfopolyester and a cross-linking agent.

A film according to claim 49, or according to any one of claims 2 to 3 and 5 when dependent from claim 49, wherein substrate layer (A) is a monolayer film or a multilayer film.

A film according to any preceding claim wherein the polyester(s) of substrate layer (A) comprises an aromatic dicarboxylic acid, preferably terephthalic acid, isophthalic acid, phthalic acid and/or 2,5-, 2,6- or 2,7-naphthalene dicarboxylic acid, and preferably terephthalic acid.

A film according to any preceding claim wherein the polyester(s) of substrate layer (A) comprises an aliphatic diol, preferably aliphatic diols containing 2-8 carbon atoms, preferably ethylene glycol and 1,4-butanediol, more preferably ethylene glycol.

A film according to any preceding claim wherein the inherent viscosity of the substrate layer (A) is at least 0.6 dL/g, preferably at least 0.7 dL/g, preferably at least 0.75 dL/g, preferably at least 0.77 dL/g.

A film according to any preceding claim wherein the thickness of substrate layer (A) is from about 0.1 to 200 µm, preferably from about 0.5 to about 100 µm, preferably from about 12 to about 50 µm, and preferably from about 15 to about 30 µm.

A film according to any preceding claim wherein the crosslinking agent of primer coating layer (B) is or comprises a water-soluble crosslinking agent.

A film according to any preceding claim wherein the crosslinking agent of primer coating layer (B) is selected from a melamine, isocyanate, oxazoline, aziridine, carbodiimide, epoxy resin, silane and zirconium based crosslinking agent.

A film according to any preceding claim wherein the composition from which the primer coating layer (B) is derived comprises in the range of from about 0.1% to about 3% by weight, preferably from about 0.2% to about 2%, preferably from about 0.5% to about 1.5% by weight of the crosslinking agent based on the total weight of the composition prior to drying.

A film according to any preceding claim wherein the composition from which the primer coating layer (B) is derived comprises in the range of from about 0.5% to about 20% by weight, preferably from about 1% to about 15%, preferably from about 2% to about 10%, preferably from about 4% to about 8% by weight of the sulfopolyester based on the total weight of the composition prior to drying.

A film according to any preceding claim wherein the composition from which the primer coating layer (B) is derived comprises a coating vehicle, preferably wherein the composition comprises the coating vehicle in an amount such that the composition has a solids content of 1 to 15%, preferably 3% to 12%, preferably 4 to 10%, preferably 5 to 8%, preferably 6% to 7% by weight relative to the total weight of the composition.

A film according to any preceding claim wherein the thickness of primer coating layer (B) is from about 5 to about 50 nm, preferably from about 10 to about 30 nm, preferably from about 15 to 25 nm.

A film according to any preceding claim wherein the composition from which the heat-sealable coating layer (C) is derived comprises in the range of from about 1% to about 20% by weight, preferably from about 5% to about 18% by weight, preferably from about 10% to about 15% by weight, and preferably from about 12% to about 14% by weight of the first copolyester based on the total weight of the composition prior to drying.

A film according to any preceding claim wherein the heat-sealable coating layer (C) comprises a second copolyester derived from an aliphatic glycol, a first aromatic dicarboxylic acid and a second aliphatic dicarboxylic acid, preferably wherein the aliphatic diol contains 2-8 carbon atom and is preferably ethylene glycol, preferably wherein the first aromatic dicarboxylic acid is terephthalic acid, and preferably wherein the second aliphatic dicarboxylic acid is isophthalic acid.

A film according to any preceding claim wherein the composition from which the heat-sealable coating layer (C) is derived comprises a coating vehicle, preferably wherein the composition comprises the coating vehicle in an amount such that the composition has a solids content of 5 to 30%, preferably 8% to 25%, preferably 10 to 20%, and preferably 15% to 19% by weight relative to the total weight of the composition.

A film according to any preceding claim wherein the thickness of heat-sealable coating layer (C) is 2 to 3.5 µm, preferably 2.4 to 3 µm, preferably 2.6 to 2.8 µm.

A film according to any preceding claim wherein the film is oriented, preferably biaxially oriented.

A film according to any preceding claim wherein the film exhibits a haze of less than 10%, preferably less than 6%, preferably less than 5% and preferably less than 2%, wherein the haze is measured according to the standard ASTM D 1003.

A film according to any preceding claim wherein the film exhibits a water vapour transmission rate of at least 80 g/m2/day, preferably at least 90 g/m2/day, preferably at least 100 g/m2/day, preferably at least 115 g/m2/day, preferably at least 130 g/m2/day, preferably at least 140 g/m2/day, and more preferably at least 150 g/m2/day, wherein the water vapour transmission rate is tested according to the method provided in the description.