Packaging film

Abstract

To provide a film characterized by good biodegradation properties, good mechanical properties (in particular a high elastic modulus) and adequate barrier properties.SOLUTION: There is provided a film comprising at least one biodegradable layer (i) having an elastic modulus of 450 MPa or more, consisting of a mixture of polyhydroxyalkanoate constituting the continuous phase and aliphatic polyester and / or aliphatic-aromatic polyester constituting the discontinuous phase, and at least one coating layer (ii) preferably capable of having barrier effects against gases and liquids. The surface of the layer (i) will have a root mean square roughness Sq of 10 nm or more and 45 nm or less, measured by atomic force microscopy (AFM). The film is particularly suitable for use in food packaging.SELECTED DRAWING: None

Description

Technical Field

[0001] Description The present invention relates to a film particularly suitable for use in the manufacture of various types of packaging, especially primary food packaging such as bags, films, lids, etc.

Background Art

[0002] In the manufacture of packages, films having properties that ensure sufficient processability and resistance to mechanical stress are required. Good mechanical properties must also be associated with the ability to protect the contents from external factors and to adequately preserve the food and extend its shelf life, especially in food packaging. These functions are mainly achieved by using films having a barrier effect against gases such as liquids and oxygen. The choice of the material that forms the base of the film directly affects the permeability of the package, but in order to achieve an appropriate barrier property (e.g., against water vapor and oxygen), the packaging film can be subjected to special treatments such as the application of a coating layer.

[0003] However, the effectiveness of the barrier effect depends on the sufficient adhesion between the coating layer and the constituent material of the film, and is thus affected by the surface properties of the film. Similarly, packaging films also respond to other surface treatments such as printing and decoration with high or low efficiency based on their surface properties. In the packaging field, mechanical properties and barrier properties are also associated with the need to use biodegradable materials that can be decomposed without accumulating waste in the environment after their primary use.

[0004] Typical biodegradable materials used in the production of food packaging films are mainly based on polylactic acid, and their rigidity and transparency cannot be achieved by other biodegradable materials. For example, WO 2011 / 123682 A1 discloses a biaxially oriented packaging film made of PLA. In order to achieve a softer touch and a quieter sound, this PLA film contains a second polyester, which forms a layered inner layer within the PLA-based layer as a result of biaxial orientation. However, polylactic acid has a limitation that its adhesion to surface coating treatment is not appropriate, and as a result, the barrier effect of the final packaging is impaired. For example, when it is necessary to use a sticky resin such as an acrylic resin and a polyurethane resin, the overall biodegradability of the packaging may be impaired. That is, manufacturers of biodegradable packaging films are faced with the problem of having to choose between using a film that has good mechanical properties and biodegradability but not optimal barrier properties, or conversely, tolerating low performance in terms of mechanical properties and biodegradability to enhance the barrier properties of the packaging. Summary of the Invention Problems to be Solved by the Invention

[0005] Therefore, there is a need to develop a film that can balance these different requirements and is thus characterized by good biodegradability, good mechanical properties (especially high elastic modulus) and reasonable barrier properties. Means for Solving the Problems

[0006] The present invention is capable of overcoming the above problems. In fact, surprisingly, biodegradable films in which aliphatic polyesters and / or aliphatic / aromatic polyesters are dispersed in a continuous phase composed of one or more polyhydroxyalkanoates in the presence of a specific amount of a crosslinking agent and / or chain extender have been found to have adhesion properties particularly suitable for surface treatments such as coating treatments having a barrier effect against gases and liquids. Films having this composition and an elastic modulus of 450 MPa or more can be effectively bonded to one or more coating layers and may be suitable for use as packaging materials having a barrier effect (e.g., for food).

[0007] Accordingly, an object of the present invention is to provide at least one biodegradable layer (i) having an elastic modulus of 450 MPa or more, comprising a mixture containing a polyhydroxyalkanoate constituting a continuous phase and an aliphatic polyester and / or an aliphatic-aromatic polyester constituting a discontinuous phase, and further containing 0.01 to 5% by weight of a crosslinking agent and / or chain extender having two or more functional groups, and at least one coating layer (ii) (which can preferably have a gas and liquid barrier effect). The surface of the layer (i) has a root mean square roughness Sq of 10 nm or more and 45 nm or less as measured by an atomic force microscope (AFM).

[0008] The present invention also relates to the use of a biodegradable film having an elastic modulus of 450 MPa or more, comprising a mixture containing polyhydroxyalkanoate as a continuous phase and at least one aliphatic polyester and / or aliphatic-aromatic polyester as a discontinuous phase, for the production of a packaging material having a barrier effect. According to one aspect, the layer (i) of the film according to the present invention contains a mixture of 10 to 49% by weight, preferably 20 to 45% by weight, more preferably 30 to 45% by weight of an aliphatic polyester and / or aliphatic / aromatic polyester and 90 to 51% by weight, preferably 80 to 55% by weight, more preferably 70 to 55% by weight of polyhydroxyalkanoate, based on the total weight of the mixture. Preferably, the mixture comprises the aliphatic polyester and / or aliphatic / aromatic polyester, the polyhydroxyalkanoate, and a crosslinking agent and / or chain extender as optional components.

Mode for Carrying Out the Invention

[0009] Hereinafter, the packaging film according to the present invention will be described in more detail while referring to the individual layers (i) and (ii) constituting the film.

[0010] Layer (i) Regarding the layer (i) of the film according to the present invention, it consists of a mixture having a continuous phase containing polyhydroxyalkanoate. This polyhydroxyalkanoate is preferably selected from the group consisting of polylactic acid, polyhydroxybutyrate, polyhydroxybutyrate-valerate, polyhydroxybutyrate-propanoate, polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodecanoate, polyhydroxybutyrate-hexadecanoate, polyhydroxybutyrate-octadecanoate, poly 3-hydroxybutyrate-4-hydroxybutyrate, or a mixture thereof. Preferably, the polyhydroxyalkanoate constituting the continuous phase contains at least 70% by weight of one or more polylactic acids.

[0011] In a preferred embodiment, the polylactic acid is selected from the group consisting of poly-L-lactic acid, poly-D-lactic acid, poly-D-lactic acid stereocomplex, a copolymer containing 50 mol% or more of the polylactic acid, and a mixture thereof. Particularly preferred is a polylactic acid containing at least 95% by weight of repeating units derived from L-lactic acid or D-lactic acid or a combination thereof, having a molecular weight Mw of 50,000 or more and a shear viscosity of 50 to 700 Pa·s, preferably 80 to 500 Pa·s (measured according to ASTM standard D3835 at T = 190°C, shear rate = 1000 s-1, D = 1 mm, L / D = 10). In a particularly preferred embodiment according to the present invention, the lactic acid polyester contains at least 95% by weight of L-lactic acid-derived units and ≤5% of D-lactic acid-derived repeating units, and has a melting point in the range of 135 to 175°C, a glass transition temperature (Tg) in the range of 55 to 65°C, and an MFR in the range of 1 to 50 g / 10 min (measured according to ISO 1133-1 at 190°C and 2.16 kg). Examples of commercially available products of lactic acid polyesters having such properties are Ingeo TM Biopolymer products 4043D, 3251D, and 6202D. The film layer (i) according to the present invention also contains at least one aliphatic polyester and / or aliphatic / aromatic polyester (preferably aliphatic / aromatic polyester) as a discontinuous phase including.

[0012] In the case of an aliphatic / aromatic polyester, this preferably includes the following: (a) A dicarboxylic acid component containing the following with respect to the total dicarboxylic acid component: a1) Units derived from at least one aromatic dicarboxylic acid in an amount of 30 to 70 mol%, preferably 40 to 60 mol%; a2) Units derived from at least one saturated aliphatic dicarboxylic acid in an amount of 70 to 30 mol%, preferably 60 to 40 mol%; a3) Units derived from at least one unsaturated aliphatic dicarboxylic acid in an amount of 0 to 5 mol% (b) A diol component containing the following with respect to the total diol component: b1) Units derived from at least one saturated aliphatic diol in an amount of 95 to 100 mol%, preferably 97 to 100 mol%; b2) Units derived from at least one unsaturated aliphatic diol in an amount of 0 to 5 mol%, preferably 0 to 3 mol%.

[0013] The aromatic dicarboxylic acid of component a1 is preferably a phthalic acid-type aromatic dicarboxylic acid, preferably terephthalic acid or isophthalic acid, more preferably terephthalic acid, and a heterocyclic dicarboxylic acid aromatic compound, preferably 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 2,3-furandicarboxylic acid, 3,4-furandicarboxylic acid, more preferably 2,5-furandicarboxylic acid, their esters, salts, and mixtures thereof. In a preferred embodiment, the aromatic dicarboxylic acid includes the following: - 1 to 99 mol%, preferably 5 to 95 mol%, more preferably 10 to 80 mol% of terephthalic acid, its ester or salt; - 99 to 1 mol%, preferably 95 to 5 mol%, more preferably 90 to 20% of 2,5-furandicarboxylic acid, its ester or salt.

[0014] The saturated aliphatic dicarboxylic acid of component a2 is preferably a C2-C 24 , preferably a C4-C 13 , more preferably a C4-C 11 saturated dicarboxylic acid, their C1-C 24 , preferably a C1-C4 alkyl ester, their salts and mixtures. Preferably, the saturated aliphatic dicarboxylic acid is selected from succinic acid, 2-ethylsuccinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid and their C1-C 24 alkyl esters. In a preferred embodiment according to the present invention, the saturated aliphatic dicarboxylic acid includes succinic acid, adipic acid, azelaic acid, sebacic acid and mixtures thereof.

[0015] The unsaturated aliphatic dicarboxylic acid of component a3 is preferably itaconic acid, fumaric acid, 4-methylenepimelic acid, 3,4-bis(methylene)nonanedioic acid, 5-methylenenonanedioic acid, their C1-C 24, preferably selected from C1-C4 alkyl esters, their salts and mixtures. In a preferred embodiment according to the present invention, the unsaturated aliphatic dicarboxylic acid is at least 50 mol%, preferably 60 mol% or more, more preferably 65 mol% or more itaconic acid, its C1-C 24 , preferably comprising a mixture containing C1-C4 esters. More preferably, the unsaturated aliphatic dicarboxylic acid consists of itaconic acid.

[0016] Regarding the saturated aliphatic diols of component b1, these are preferably 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, 2-methyl-1,3-propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, cyclohexanemethanediol, dialkylene glycol and polyalkylene glycols with a molecular weight of 100 to 4000 such as polyethylene glycol and polypropylene glycol, and mixtures thereof. Preferably, the diol component contains at least 50 mol% of one or more diols selected from 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol. More preferably, the diol component contains 1,4-butanediol or consists of 1,4-butanediol.

[0017] Regarding the unsaturated aliphatic diols of component b2, these are preferably selected from cis-2-butene-1,4-diol, trans-2-butene-1,4-diol, 2-butyne-1,4-diol, cis-2-pentene-1,5-diol, trans-2-pentene-1,5-diol, 2-pentyne-1,5-diol, cis-2-hexene-1,6-diol, trans-2-hexene-1,6-diol, 2-hexyne-1,6-diol, cis-3-hexene-1,6-diol, trans-3-hexene-1,6-diol, 3-hexyne-1,6-diol.

[0018] In the case of the aliphatic polyester, this preferably contains the following: (c) A dicarboxylic acid component containing the following with respect to the total dicarboxylic acid component: (c1) Units derived from at least one aliphatic dicarboxylic acid in an amount of 95 to 100 mol%; (c2) Units derived from at least one unsaturated aliphatic dicarboxylic acid in an amount of 0 to 5 mol%; (d) A diol component containing the following with respect to the total diol component: (d1) Units derived from at least one saturated aliphatic diol in an amount of 95 to 100 mol%; (d2) Units derived from at least one unsaturated aliphatic diol in an amount of 0 to 5 mol%.

[0019] The saturated aliphatic dicarboxylic acid of component c1 is preferably a saturated C2-C 24 , preferably C4-C 13 , more preferably C4-C 11 dicarboxylic acid, their C1-C 24 , preferably C1-C4 alkyl esters, their salts and mixtures. Preferably, the saturated aliphatic dicarboxylic acid is succinic acid, 2-ethylsuccinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, hexadecanedioic acid, octadecanedioic acid and their C1-C 24 alkyl esters.

[0020] The unsaturated aliphatic dicarboxylic acid of component c2 is preferably itaconic acid, fumaric acid, 4-methyl-pimelic acid, 3,4-bis(methylene)nonanedioic acid, 5-methylene-nonanedioic acid, their C1-C 24 , preferably selected from C1-C4 alkyl esters, their salts and mixtures. In a preferred embodiment according to the present invention, the unsaturated aliphatic dicarboxylic acid contains at least 50 mol%, preferably 60 mol% or more, preferably 65 mol% or more of itaconic acid, its C1-C 24 , preferably a mixture containing a C1-C4 ester. More preferably, the unsaturated aliphatic dicarboxylic acid consists of itaconic acid.

[0021] Regarding the saturated aliphatic diol of component d1, these are preferably 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, 2-methyl-1,3-propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, cyclohexanemethanediol, dialkylene glycol and polyalkylene glycol with a molecular weight of 100 to 4000 such as polyethylene glycol and polypropylene glycol, and mixtures thereof. The diol component preferably contains at least 50 mol% of one or more diols selected from 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol. More preferably, the diol component contains 1,4-butanediol or consists of 1,4-butanediol.

[0022] Regarding the unsaturated aliphatic diols of component d2, these are preferably selected from cis-2-butene-1,4-diol, trans-2-butene-1,4-diol, 2-butyne-1,4-diol, cis-2-pentene-1,5-diol, trans-2-pentene-1,5-diol, 2-pentyne-1,5-diol, cis-2-hexene-1,6-diol, trans-2-hexene-1,6-diol, 2-hexyne-1,6-diol, cis-3-hexene-1,6-diol, trans-3-hexene-1,6-diol.

[0023] In a particularly preferred embodiment, the aliphatic polyester and / or aliphatic / aromatic polyester of layer (i) according to the present invention is selected from the group consisting of poly(1,4-butylene succinate), poly(1,4-butylene succinate-co-adipate), poly(1,4-butylene succinate-co-1,4-butylene azelate), poly(1,4-butylene adipate-co-1,4-butylene terephthalate), poly(1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene terephthalate), poly(1,4-butylene brasilate-co-1,4-butylene terephthalate), poly(1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene azelate-co-1,4-butylene terephthalate), poly(1,4-butylene succinate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene terephthalate).

[0024] The aliphatic polyester and / or aliphatic / aromatic polyester of layer (i) according to the present invention may also advantageously contain repeating units derived from at least one hydroxy acid in an amount of 0 to 49 mol%, preferably 0 to 30 mol%, based on the total number of moles of the dicarboxylic acid component. Examples of suitable hydroxy acids are glycolic acid, hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid, 7-hydroxyheptanoic acid, 8-hydroxyheptanoic acid, 9-hydroxynonanoic acid, lactic acid or lactide. The hydroxy acid may be inserted as such or as a prepolymer / oligomer into the chain, or may be reacted in advance with a diacid or diol.

[0025] Long molecules having two functional groups containing non-terminal functional groups may also be added in an amount not exceeding 10 mol% based on the total number of moles of the dicarboxylic acid component. Examples are dimer acid, ricinoleic acid and acids having an epoxy functional group, and polyoxyethylene with a molecular weight of 200 to 10,000. Diamines, amino acids or amino alcohols may also be present in a proportion of up to 30 mol% based on the total number of moles of the dicarboxylic acid component.

[0026] In the process for producing the aliphatic polyester and / or aliphatic / aromatic polyester of layer (i) according to the present invention, advantageously, in order to obtain a branched product, one or more molecules having a plurality of functional groups may be added in an amount of 0.1 to 3 mol% based on the total number of moles of the dicarboxylic acid component. Examples of these molecules are glycerol, pentaerythritol, trimethylolpropane, citric acid, dipentaerythritol, monoanhydrosorbitol, monoanhydromannitol, acid triglyceride, polyglycerol, etc. The number average molecular weight Mn of the aliphatic and / or aliphatic-aromatic polyester layer (i) is preferably ≧20,000, more preferably ≧40,000. Instead, with respect to the polydispersity index (Mw / Mn) of the molecular weight, this is preferably 1.5 to 10, more preferably 1.6 to 5, and even more preferably 1.8 to 2.7.

[0027] The number-average molecular weight Mn and weight-average molecular weight Mw can be measured using gel permeation chromatography (GPC). The measurement can be carried out on a chromatography system maintained at 40 °C, using a set of two columns in series (mixed porosity with particle sizes of 5 μm and 3 μm), a refractive index detector, chloroform as the eluent (flow rate 0.5 ml / min), and polystyrene as the reference standard. The melt flow rate (MFR) of the aliphatic polyester and / or aliphatic-aromatic polyester of layer (i) is preferably 500 to 1 g / 10 min, more preferably 100 to 3 g / 10 min, and even more preferably 15 to 3 g / 10 min (measured at 190 °C / 2.16 kg according to the standard ISO 1133-1 "Plastics - determination of the melt mass-flow rate (MFR) and melt volume flow rate (MVR) of thermoplastics - Part 1: Standard method"). The content of terminal acid groups in the aliphatic and / or aliphatic-aromatic polyester layer (i) is preferably 100 meq / kg, more preferably 60 meq / kg or less, and even more preferably 40 meq / kg.

[0028] The content of terminal acid groups can be measured as follows. 1.5 to 3 g of polyester is placed in a 100 ml flask together with 60 ml of chloroform. After the polyester is completely dissolved, 25 ml of 2-propanol and 1 ml of deionized water are added immediately before analysis. The solution thus obtained is titrated with a standardized NaOH solution in ethanol. The titration endpoint is determined using a suitable indicator (e.g., a glass electrode for acid-base titration in a non-aqueous solvent). The content of terminal acid groups is calculated from the consumption of the NaOH solution in ethanol according to the following formula:

Number

[0029] Preferably, the aliphatic and / or aliphatic / aromatic polyester of layer (i) has an intrinsic viscosity (measured with an Ubbelohde viscometer for a solution in CHCl3 at a concentration of 0.2 g / dl at 25 °C) greater than 0.3 dl / g, preferably between 0.3 and 2 dl / g, more preferably between 0.4 and 1.1 dl / g. The aliphatic and / or aliphatic / aromatic polyester of layer (i) is biodegradable. For the purposes of the present invention, biodegradable polymer means a biodegradable polymer according to EN 13432. The aliphatic and / or aliphatic / aromatic polyester of layer (i) can be synthesized by any of the processes known in the art. In particular, the aliphatic and / or aliphatic / aromatic polyester of layer (i) can advantageously be obtained by a condensation polymerization reaction.

[0030] The synthesis process can advantageously be carried out in the presence of a suitable catalyst. Examples of suitable catalysts include organotin compounds such as stannous acid derivatives, titanium compounds such as orthobutyl titanate, aluminium compounds such as Al-triisopropyl, compounds of antimony, zinc and zirconium, and mixtures thereof. Examples of synthesis processes that can be advantageously used for the production of the polyester are described in international application WO 2016 / 050963.

[0031] The film layer (i) according to the present invention contains at least a crosslinking agent and / or a chain extender in an amount of 0.01 to 5% by weight, preferably 0.01 to 4% by weight, more preferably 0.05 to 4% by weight, even more preferably 0.1 to 3% by weight of the total mixture. The crosslinking agent and / or chain extender according to the present invention is selected from compounds having two or more functional groups including isocyanate, peroxide, carbodiimide, isocyanurate, oxazoline, epoxy, anhydride or divinyl ether groups and mixtures thereof. According to a preferred embodiment of the present invention, the biodegradable film layer (i) according to the present invention contains 0.01 to 0.45% by weight, based on the total mixture, of a crosslinking agent and / or chain extender having two or more functional groups. According to this embodiment, the crosslinking agent and / or chain extender having two or more functional groups preferably has a peroxide group or an epoxy group.

[0032] The crosslinking agent and / or chain extender, preferably the crosslinking agent and / or chain extender having a peroxide group or an epoxy group, improves the rheology of the mixture constituting layer (i) and affects its surface properties. These compounds having two or more functional groups, preferably compounds having a peroxide group or an epoxy group, are preferably contained in the film layer (i) in an amount of 0.4% by weight or less, more preferably 0.35% by weight or less, still more preferably 0.3% by weight or less.

[0033] Regarding compounds having two or more functional groups having a peroxide group, these are preferably benzoyl peroxide, lauroyl peroxide, isononanoyl peroxide, di-(t-butylperoxyisopropyl)benzene, t-butyl peroxide, dicumyl peroxide, α,α-(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hex-3-yne, di(4-t-butylcyclohexyl) peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, 3,6,9-trimethyl-3,6,9-trimethyl-1,4,7-triperoxonan, di(2-ethylhexyl) peroxydicarbonate and mixtures thereof. According to one aspect, the compound having these two or more functional groups has a peroxide group and is preferably contained in the film layer (i) in an amount of 0.01 to 0.1% by weight, more preferably 0.01 to 0.05% by weight, of the total mixture constituting the layer (i). Due to the radical mechanism of action of these compounds having a peroxide group, a gel can be formed in the polymer matrix.

[0034] Compounds having an epoxy group are preferred to minimize gel formation. Examples of compounds having two or more functional groups having an epoxy group that can be advantageously used in the mixtures according to the invention are all polyepoxides derived from epoxidized oils and / or styrene-glycidyl ether-methyl methacrylate and / or glycidyl ether methyl methacrylate, preferably in the range of molecular weights from 1000 to 10000, with an epoxide number per molecule in the range of 1 to 30, preferably 5 to 25. The epoxides are selected from the group comprising: diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycidyl ether glycerol, polyglycidyl ether diglycerol, 1,2-epoxybutane, polyglycidyl ether polyglycerol, isoprene dioxide and cycloaliphatic epoxides, 1,4-cyclohexanedimethanol diglycidyl ether, 2-methylphenyl ether glycidyl 2-methylphenyl ether, propoxylated glycerol, 1,4-butanediol diglycidyl ether, polyglycidyl sorbitol, glycerol diglycidyl ether, tetraglycidyl meta-xylenediamine ether and bisphenol A-glycidyl ether and mixtures thereof. According to one preferred embodiment, the compound having these two or more functional groups has an epoxy group and is contained in the film layer (i) in an amount of 0.05 to 0.3% by weight, more preferably 0.1 to 0.3% by weight, of the total mixture constituting the layer (i).

[0035] According to one aspect of the present invention, the crosslinking agent and / or chain extender includes a compound having two or more functional groups having a carbodiimide group, which further improves the stability against hydrolysis. Compounds having two or more functional groups having a carbodiimide group (which are preferably used in the mixtures according to the present invention) are poly(cyclooctylene carbodiimide), poly(1,4-dimethylenecyclohexylene carbodiimide), poly(cyclohexylene carbodiimide), poly(ethylene carbodiimide), poly(butylene carbodiimide), poly(isobutylene carbodiimide), poly(nonylene carbodiimide), poly(dodecylene carbodiimide), poly(neopentylene carbodiimide), poly(1,4-dimethylenephenylene carbodiimide), poly(2,2',6,6'-tetraisopropyldiphenylene carbodiimide)(Stabaxol ( Registered Trademark ) D), poly(2,4,6-triisopropyl-1,3-phenylene carbodiimide)(Stabaxol ( Registered Trademark ) P-100), poly(2,6-diisopropyl-1,3-phenylene carbodiimide)(Stabaxol ( Registered Trademark ) P), poly(tolyl carbodiimide), poly(4,4'-diphenylmethane carbodiimide), poly(3,3'-dimethyl-4,4'-biphenylene carbodiimide), poly(p-phenylene carbodiimide), poly(m-phenylene carbodiimide), poly(3,3'-dimethyl-4,4'-diphenylmethane carbodiimide), poly(naphthylene carbodiimide), poly(isophorone carbodiimide), poly(cumene carbodiimide), p-phenylene bis(ethyl carbodiimide), 1,6-hexamethylene bis(ethyl carbodiimide), 1,8-octamethylene bis(ethyl carbodiimide), 1,10-decamethylene bis(ethyl carbodiimide), 1,12-dodecamethylene bis(ethyl carbodiimide) and mixtures thereof.

[0036] According to one aspect, the crosslinking agent and / or chain extender includes at least one compound having two or more functional groups containing isocyanate groups. More preferably, the crosslinking agent and / or chain extender includes one or more compounds having two or more functional groups containing isocyanate groups, and at least 25% by weight thereof. Particularly preferred is a mixture of a compound having two or more functional groups having isocyanate groups and a compound having two or more functional groups containing epoxy groups. More preferably, it is a mixture containing at least 75% by weight of a compound having two or more functional groups having isocyanate groups.

[0037] The compound having two or more functional groups containing isocyanate groups is preferably selected from p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4-diphenylmethane diisocyanate, 1,3-phenylene-4-chloro diisocyanate, 1,5-naphthalene diisocyanate, 4,4-diphenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 3-methyl-4,4'-diphenylmethane diisocyanate, diphenyl ester diisocyanate, 2,4-cyclohexane diisocyanate, 2,3-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexyl diisocyanate, 1-methyl-2,6-cyclohexyl diisocyanate, bis-(cyclohexyl isocyanate) methane, 2,4,6-toluene triisocyanate, 2,4,4-diphenyl ether triisocyanate, polymethylene-polyphenyl-polyiisocyanate, methylene diphenyl diisocyanate, triphenylmethane triisocyanate, 3,3'-ditoluene-4,4-diisocyanate, 4,4'-methylene-bis-(2-methylphenyl isocyanate), hexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,2-cyclohexylene diisocyanate, and mixtures thereof. In one preferred embodiment, the compound containing isocyanate groups is 4,4-diphenylmethane-diisocyanate.

[0038] In one preferred embodiment of the present invention, the crosslinking agents and / or chain extenders present in the mixture constituting layer (i) have a peroxy group and / or an epoxy group, preferably an epoxy group of the styrene-glycidyl ether-methyl methacrylate type, and / or an isocyanate group, preferably 4,4-diphenylmethane-diisocyanate, and / or a carbodiimide group, and include compounds having such groups. In one particularly preferred embodiment of the present invention, the crosslinking agent and / or chain extender includes a compound containing an epoxy group of the styrene-glycidyl ether-methyl methacrylate type. In combination with a compound having two or more functional groups having an isocyanate group, a peroxide group, a carbodiimide group, an isocyanurate group, an oxazoline group, an epoxy group, an anhydride group or a divinyl ether group, a catalyst may also be used to enhance the reactivity of the reactive groups. In the case of polyepoxides, salts of fatty acids are preferably used, and more preferably calcium stearate and zinc stearate are used.

[0039] The mixture constituting the film layer (i) according to the present invention may also optionally contain one or more additives selected from the group consisting of plasticizers, UV stabilizers, lubricants, nucleating agents, surfactants, antistatic agents, pigments, lignin, organic acids, antioxidants, fungicides, waxes, process aids and polymer components (preferably polymer components selected from the group including vinyl polymers and diacid diol polyesters other than the above aliphatic polyesters and / or aliphatic / aromatic polyesters). Each additive is present in an amount of preferably less than 10% by weight, more preferably less than 5% by weight, and even more preferably less than 1% by weight of the total weight of the mixture.

[0040] One of the advantages according to the present invention is represented by the fact that the mixture constituting layer (i) has remarkable processability compared to conventional materials, and thus easy film formation is possible without the aid of additives such as slip agents and / or release agents and processing aids. Slip agents and / or release agents are, for example, biodegradable fatty acid amides such as oleamide, erucamide, ethylene-bis-stearylamide, fatty acid esters such as glycerol oleate or glycerol stearate, fatty acid soaps such as stearate, and inorganic agents such as silica or talc. Among the slip agents and / or release agents, silica is preferred. According to an advantageous embodiment, the mixture of layer (i) has a slip agent and / or release agent content of 0.5 wt% or less, preferably 0.3 wt% or less, more preferably 0.1 wt% or less, based on the weight of the mixture. More preferably, there is no slip agent and / or release agent. This makes it possible to limit the migration phenomenon of additives that can change adhesiveness to the surface.

[0041] According to one preferred embodiment, the mixture of layer (i) according to the invention has an MFR value (measured at 190 °C / 2.16 kg according to ISO 1133-1) of 20 to 1 g / 10 min, more preferably 17 to 1.5 g / 10 min, even more preferably 14 to 2 g / 10 min. The film layer (i) according to the invention can advantageously be obtained by a film forming process, preferably a bubble film forming, or a cast extrusion process. The bubble film forming process is preferably characterized by a blow-up ratio (BUR or transverse stretch) value of 2 to 5 and a draw-down ratio (DDR or longitudinal stretch) value in the machine direction (MD) of 5 to 60. For the purposes of the present invention, DDR is defined as the measured elongation in the pulling direction of the molten material extruded from the extruder, and BUR is defined as the ratio of the bubble diameter to the die diameter. Advantageously, during bubble blowing, the process parameters are set such that the DDR / BUR value has a ratio of 1.5 to 18, preferably 2.5 to 10.

[0042] The film layer (i) is preferably a bubble blown film. After its manufacture, the film layer (i) is preferably not subjected to a further stretching process, either in series or discontinuously, with the film forming process. The stretching process can in fact affect the uniformity of the film and thus that of the coating layer, and can therefore reduce the barrier effect. According to one aspect of the invention, the film layer (i) is a film mainly oriented in one direction, i.e. a film whose molecular chains are mainly oriented in one direction (typically the machine direction).

[0043] The film layer (i) according to the invention can also be subjected to one or more treatments in order to enhance the final performance of the packaging material. The layer (i) can be subjected to an activation treatment (for example, a treatment that increases the surface tension, such as a plasma treatment, a corona treatment or a priming treatment) to enhance the adhesion of the coating layer (ii) and prevent delamination. However, one of the main advantages according to the invention lies precisely in the surface properties of the layer (i), which makes it possible to achieve effective adhesion even with mild treatments or even without an activation treatment.

[0044] In fact, surprisingly, the surface of layer (i) according to the present invention generally has a greater roughness than commonly used PLA films. In the art, roughness is considered to have a negative impact on the adhesion of the coating layer and thus on the barrier effect of the film. Nevertheless, the films of the present invention having a specific range of roughness exhibit a high degree of adhesion even without the need for an adhesive layer. In particular, the root mean square roughness (Sq) measured by an atomic force microscope (AFM) over an area of 10 μm × 10 μm is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, still more preferably 40 nm or more, and preferably 45 nm or less, 35 nm or less, more preferably 30 nm or less. A preferred range is 10 to 45 nm, and most preferred is 15 to 30 nm. This measurement value can be obtained, for example, by operating in tapping mode at a resolution of 256 points × 256 lines using a monolithic silicon microlever (cantilever) with a length of 225 microns, a natural frequency of 190 kHz, a force constant of 48 N / m, and a tip radius of 10 nm or less.

[0045] This root mean square roughness value Sq is calculated as the root mean square of the actual profile deviation from the mean line according to the following formula:

Equation

[0046] Thus, unlike the average roughness, the Sq value is also affected by the amplitude of the peaks and troughs detected by the measuring instrument on the measured surface, which makes it possible to distinguish between surfaces that undulate greatly or little. The characteristic undulations of layer (i) according to the present invention are considered to have the effect of facilitating the adhesion of the coating layer (ii). When performing AFM analysis under the above conditions, this surface also typically shows a Sy difference between the maximum profile height (maximum peak) and the maximum profile valley depth (maximum trough) compared to the average line that is 90 nm or more, preferably 95 nm or more, more preferably 100 nm or more, even more preferably 150 nm or more, and still more preferably 200 nm or more. Advantageously, the Sy value is 300 nm or less, preferably 280 nm or less. The thickness of layer (i) is advantageously 120 μm or less, more advantageously 80 μm or less, preferably 50 μm or less, and more preferably 30 μm or less. The thickness of this layer can be measured by any suitable technique such as a micrometer or an electron microscope.

[0047] The film according to the present invention can be applied to the manufacture of packaging materials also due to the optimal mechanical properties of layer (i). In particular, the film obtained using the mixture constituting layer (i) of the present invention advantageously has an elongation at break (ε b ) value of 400% or less, preferably 350% or less, as measured according to ASTM D882 (23 °C, relative humidity 50%, Vo 50 mm / min). Such a film obtained using the mixture constituting layer (i) according to the present invention advantageously has an elongation at break (ε b ) value of 150% or more as measured according to ASTM D882 (23 °C, relative humidity 50%, Vo 50 mm / min).

[0048] Also, the film obtained using the mixture constituting layer (i) according to the present invention advantageously has a modulus of elasticity (E) value of 450 MPa or more, preferably 500 MPa or more, more preferably 1000 MPa or more as measured according to ASTM D882 (23 °C, relative humidity 50%, Vo 50 mm / min). According to one particularly advantageous embodiment, layer (i) according to the present invention has a modulus of elasticity (E) value of more than 1500 MPa, preferably 1700 MPa or more. Advantageously, the mixture constituting the film layer (i) according to the present invention is biodegradable. For the purposes of the present invention, "biodegradable" means biodegradability according to EN13432. The layer (i) of the rigid film according to the present invention may be transparent or opaque . With regard to optical properties, according to one preferred embodiment, the film according to the present invention has a transmittance value of 80% or more, more preferably 90% or more, a haze value of 65% or less, more preferably 55% or less, and a clarity of 20% or more, more preferably 40% or more (measured according to ASTM standard D1003).

[0049] Layer (ii) The barrier film according to the present invention includes at least one coating layer (ii) adjacent to the layer (i), and preferably can have a barrier effect against gases and liquids containing water vapor. This coating layer (ii) may contain an inorganic material (for example, metal alkoxide, silicon oxide) or an organic material (for example, having the properties of proteins and / or polysaccharides or lipid-based polymers and biopolymers), optionally in combination to form a mixture or overlapping layers.

[0050] According to one embodiment of the present invention, this coating layer (ii) consists of one or more inorganic materials. Among the inorganic substances, metals such as silver, copper, gold, aluminum, aluminum oxide, titanium oxide and / or aluminum titanium oxide, silicon dioxide, zinc oxide and their oxides and alkoxides can be used.

[0051] According to another embodiment of the present invention, this coating layer (ii) consists of one or more organic materials. Among organic materials, natural substances such as different forms of cellulose (e.g., nanocrystalline form - NCC - or nanofibrillated form - NFC -) and their derivatives, chitosan, chitin, pectin, gluten, casein, zein, different forms of starch and its derivatives, gelatin, whey protein, carrageenan, guar gum, xanthan gum, alginate, and synthetic polymers such as polyvinyl alcohol, polyvinyl acetate, ethylene vinyl acetate, acrylate, polyamide, polyvinyl chloride, organosilane or polyethylene glycol can be used. Among synthetic polymers, polyvinyl alcohol, ethylene vinyl alcohol and polyvinyl alcohol - based polymers with different degrees of hydrolysis are preferred. Particularly preferred synthetic polymers are selected from polyvinyl alcohol, ethylene - vinyl alcohol and their copolymers; more preferably, polyvinyl alcohol, and advantageously polyvinyl alcohol with a degree of hydrolysis of 70 - 100%.

[0052] The coating layer (ii) can further contain fillers such as zeolite, graphene, graphene oxide or zirconium phosphate for the purpose of improving the performance of the final barrier. According to another embodiment of the present invention, this coating layer (ii) consists of a combination of one or more organic materials and one or more inorganic materials. According to this embodiment, the coating layer (ii) preferably includes a first layer of an organic material (which may be natural and / or synthetic) in contact with the layer (i) and a second layer of a metal material covering the first layer. This configuration of the layer (ii) has the advantage of enhancing the barrier effect. Preferably, the coating layer (ii) of the barrier film according to the present invention contains one or more materials selected from metals and their oxides and alkoxides, cellulose and its derivatives, starch and its derivatives, chitosan, synthetic polymers (e.g., polyvinyl alcohol, ethylene vinyl alcohol, polyvinyl acetate, ethylene vinyl acetate, acrylate, organosilane, polyethylene glycol), and combinations thereof.

[0053] The term starch encompasses all types of starch, in particular the following: wheat flour, native starch, hydrolyzed starch, destructurized starch, gelatinized starch, plasticized starch, thermoplastic starch, biopolymers containing composite starch, or mixtures thereof. Starches that can be easily destructurized and can have a high initial molecular weight (for example, potato starch and corn starch) are particularly advantageous. Starch and cellulose may be present as such or in a chemically modified form, for example as esters of starch or cellulose (preferably with a degree of substitution of 0.2 to 2.5), hydroxypropylated starch, starch modified with fatty chains, or in the form of cellophane. Destructurized starch, as used herein, refers to the teachings contained in patent EP 0 118 240 and EP 0 327 505, and means starch processed in such a way that it does not substantially exhibit the so-called "Maltese cross" under polarized light microscopy and the so-called "ghost" under phase contrast light microscopy. Destructurization of the starch is preferably carried out by an extrusion process at a temperature between 110 °C and 250 °C, preferably between 130 °C and 220 °C, and preferably at a pressure between 0.1 MPa and 7 MPa, preferably between 0.3 MPa and 6 MPa, and preferably with a specific energy of at least 0.1 kWh / kg being provided during extrusion.

[0054] The disruption of starch is preferably carried out in the presence of one or more plasticizers selected from water and polyols having 2 to 22 carbon atoms, in an amount of 1 to 40% by weight based on the weight of the starch. Regarding the water, this may be the water naturally present in the starch. Among the polyols, polyols having 1 to 20 hydroxy groups and containing 2 to 6 carbon atoms, their ethers, thioethers, and organic and inorganic esters are preferred. Examples of polyols are glycerol, diglycerol, polyglycerol, pentaerythritol, polyglycerol ethoxylate, ethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, sorbitol, sorbitol monoacetate, sorbitol diacetate, sorbitol monoethoxylate, sorbitol diethoxylate, and mixtures thereof. In one preferred embodiment, the starch is disrupted in the presence of glycerol or a mixture of plasticizers containing glycerol (preferably 1 to 90% by weight of glycerol). Preferably, the disrupted starch contains 1 to 40% by weight of a plasticizer selected from the above, based on the starch weight. Compositions containing disrupted starch are particularly preferred. Preferably, the starch in the mixture is present in the form of particles having a circular, elliptical or other elliptical-like cross-section with an arithmetic mean diameter, measured considering the major axis of the particle, of less than 1 μm, more preferably less than 0.5 μm. According to one aspect of the present invention, layer (ii) contains disrupted starch in a complexed form with a polymer containing hydrophilic groups intercalated with hydrophobic sequences, such as the composition described in patent application EP 2 758 465. These compositions can be applied in the form of an aqueous dispersion; preferably, these compositions contain, based on the total weight of the composition, - 30 to 80% disrupted starch; - 20 to 70% of a polymer containing hydrophilic groups intercalated with hydrophobic sequences; - 0 to 25% plasticizer; - 0 to 20% water and comprise.

[0055] According to this aspect, the disrupted starch in complex form means disrupted starch having one or more crystal forms that can be associated with one or more of the following diffraction peaks in an X-ray spectrometer.

Table 1

[0056] Regarding polymers containing hydrophilic groups intercalated with hydrophobic sequences, these are preferably insoluble in water. This reduces the water permeability of the coating layer (ii) according to the present invention. Regarding polymers containing hydrophilic groups intercalated with hydrophobic sequences, these are advantageously a. Polyvinyl alcohol having a degree of hydrolysis of 10 to 100%; b. Vinyl alcohol / vinyl acetate block copolymer; c. Polyvinyl acetate in dry form and in an aqueous emulsion form; d. Ethylene copolymers with vinyl alcohol, vinyl acetate, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic anhydride, glycidyl methacrylate or mixtures thereof; e. 6-6, 6-9 or 12 aliphatic polyamides, aliphatic polyurethanes, aliphatic and aliphatic / aromatic polyesters, random or block polyurethane / polyamide, polyurethane / polyether, polyurethane / polyester, polyamide / polyester, polyamide / polyether, polyester / polyether, polyure a / polyester, polyure a / polyether, polylactic acid, polyglycolic acid, polycaprolactone / urethane copolymer (the molecular weight of the polycaprolactone block is 300 to 3000) selected from. Mixtures of these polymers may also be used.

[0057] Among the polymers containing hydrophilic groups intercalated with hydrophobic arrays, preferred are ethylene copolymers with vinyl alcohol and / or acrylic acid, polyvinyl alcohol with a degree of hydrolysis of 10 to 100%, polyvinyl acetate in a dry state and emulsified in water, vinyl alcohol / vinyl acetate block copolymers, and mixtures thereof. Among these, polyvinyl alcohol and ethylene copolymers with vinyl alcohol and acrylic acid are particularly preferred. In the case of ethylene copolymers with vinyl alcohol, these preferably contain 20 to 50 mol% of ethylene units. In the case of ethylene copolymers with acrylic acid, these preferably contain 70 to 99 wt% of ethylene units. This composition based on disrupted and complexed starch is preferably deposited in the form of an aqueous dispersion.

[0058] As a result of the properties of the above-mentioned disrupted and complexed starch composition, the layer (ii) exhibits high barrier properties (e.g., against saturated and aromatic hydrocarbon compounds), which makes it particularly useful for packaging in the food field. This coating layer (ii) can be applied to the film layer (i) using known techniques, such as those typically used in the coating and printing industries. For example, the coating may be carried out in a molten state; or the coating layer may be transferred to the surface to be coated in the form of a solution or dispersion in a solvent, as in the case of a coating process such as blade or film coating, and then the solvent may be evaporated to solidify the coating or lacquer. In the latter case, an organic solvent or water is typically used. Other coating methods include methods of transferring to the surface of the material to be coated by sublimation (e.g., sublimation under vacuum conditions) or electromagnetic process treatment.

[0059] The coating process in the form of a solution or solvent dispersion typically includes a step of depositing the coating layer on one side of the substrate and a step of drying the substrate. This process advantageously includes, after deposition, removing a portion of the deposited coating composition from the substrate, whereby the thickness of the coating layer (known as leveling) can be adjusted. For the step of drying the substrate, a radiation system (preferably infrared), a convection system (preferably hot air) or a contact system (preferably comprising a drying cylinder) or any combination thereof can be advantageously used. Preferably, the film according to the invention is suitable for contact with food.

[0060] The film according to the invention can take the form of a multilayer film comprising at least one additional polymer layer (iii) adjacent to the first layer (i) described above. The polymer layer (iii) includes, for example, polymers of natural origin (such as cellulose and its derivatives) or polymers of synthetic origin. Preferably, the polymer layer (iii) includes or preferably consists of one or more polymers selected from the following: - Polyhydroxyalkanoates, preferably polyesters of lactic acid, poly-ε-caprolactone, polyhydroxybutyrate, polyhydroxybutyrate-valerate, polyhydroxybutyrate-propanoate, polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodecanoate, polyhydroxybutyrate-hexadecanoate, polyhydroxybutyrate-octadecanoate, poly 3-hydroxybutyrate-4-hydroxybutyrate and mixtures thereof, polyhydroxyalkanoates selected from the group consisting of; - Aliphatic / aromatic polyesters of the diacid diol type, the same as or different from those described above as components of layer (i); - Aliphatic polyesters, preferably selected from those described above as components of layer (i), aliphatic polyesters having a melting point not exceeding 110 °C; And mixtures thereof.

[0061] The multilayer film according to the present invention can be manufactured according to any process known to those skilled in the art, for example, by means of coextrusion, lacquer coating / coating and lamination. In one preferred embodiment, the multilayer film according to the present invention may be obtained by a process of coextruding layers (i) and (iii), and then applying the coating layer (ii). Preferably, the coextrusion process is combined with a bubble film forming process. The apparatus and specific process conditions for the manufacture of the multilayer film according to the present invention (for example, the apparatus and specific process conditions for coextrusion and film forming) depend on the composition and number of layers of the multilayer film to be manufactured.

[0062] The film according to the present invention may also be adhered to a layer of another material such as paper, or the layer may be laminated. In this case, layer (i) is preferably adhered to the material by extrusion coating and then the coating layer (ii) is applied. The present invention also relates to a packaging material obtained using the film according to the present invention, for example, a packaging material in the form of a bag, a packaging, a backing / lining, a cap or a lid. Although the present invention is described using several embodiments, it should be understood that these are illustrative and do not limit the scope of protection of this patent application.

Examples

[0063] Examples Example 1 Layer (i) 14.3 kg / h of poly(butylene adipate-co-butylene terephthalate) (MFR 4.2 g / 10 min (190 °C; 2.16 kg) and acid value 42 meq / kg), 24.7 kg / h of Ingeo 3251D polylactic acid ("PLA") (MFR 40 g / 10 min (190 °C; 2.16 kg), and 1.0 kg / h of a masterbatch containing 10 wt% Joncryl ADR4368CS (styrene-glycidyl ether-methyl methacrylate copolymer) and 90% Ingeo 4043D polylactic acid ("PLA") were fed to an OMC type twin-screw extruder operating under the following conditions: Screw diameter (D) = 58 mm; L / D = 36; Rotational speed = 140 rpm; Thermal profile = 60 - 150 - 180 - 210 x 4 - 180 x 2 °C; Throughput = 40 kg / h; Vacuum degassing was carried out in 8 out of 10 zones.

[0064] The granules thus obtained had an MFR value of 11.4 g / 10 min (at 190 °C; 2.16 kg in accordance with ISO standard 1133-1 "Plastics - determination of the melt mass-flow rate (MFR) and melt volume flow rate (MVR) of thermoplastics - Part 1: Standard method"). The granules thus obtained were fed to a Ghioldi model blown film apparatus equipped with a 40 mm diameter screw (L / D 30) operating at 64 rpm with a thermal profile of 120 - 200 x 3. The film forming head having a 0.9 mm gap and L / D 12 was set at 200 °C. Film formation was carried out at a blow ratio of 3.2 and a draw ratio of 11.7. The film thus obtained (total 24 microns) was then characterized with respect to mechanical properties, particularly tensile strength (σ b ), elongation at break (ε b ), modulus of elasticity (E), optical properties (transmittance, haze and transparency) and roughness.

[0065] The roughness measurement was performed using a monolithic silicon microlever (cantilever) with a length of 225 microns, a natural frequency of 190 kHz, a force constant of 48 N / m, and a tip radius of 10 nm or less, for an area of 10 μm × 10 μm, by an AFM operating in tapping mode with a resolution of 256 points × 256 lines.

Table 2

[0066] Layer (ii) A composite starch-based coating composition was produced by supplying 19.8 kg / h of natural corn starch (containing 12% water), 12.9 kg / h of polyvinyl alcohol with a degree of hydrolysis of 84.2% - 86.2%, 2.8 kg / h of glycerin, and 4.5 kg / h of water to an OMC model twin-screw extruder operating under the following conditions: Screw diameter (D) = 58 mm; L / D = 36; Rotational speed = 140 rpm; Thermal profile = 145 - 170 - 200x4 - 150x2 °C; Throughput = 40 kg / h; Vacuum degassing was performed in 8 zones out of 10. 20 g of the product was added to 80 g of deionized water and dispersed at 25000 rpm for 15 minutes using a rotor - stator disperser (Ika Ultra - Turrax T25). After cooling this suspension to room temperature, a coating of 12 g / m2 was applied to the surface of layer (i) using an airbrush. The obtained film appeared to show good adhesion between layer (i) and layer (ii) visually.

[0067] The barrier properties of the obtained film were determined by permeability measurements performed at 23 °C - 50% relative humidity using an Extrasolution Multiperm permeation meter according to ASTM F2622 - 08 for oxygen and according to ASTM standard F2476 - 05 for carbon dioxide, and are shown in Table 2.

Table 3

[0068] Comparative Example 2 Layer (i) Ingeo TM Biopolymer 4043D polylactic acid (MFR (190 °C, 2.16 kg) equal to 3 g / 10 min) was supplied to a Ghioldi model bubble film forming apparatus equipped with a 40 mm diameter screw (L / D 30) operating at 64 rpm with a thermal profile of 120 - 190 × 3 °C. The film head having a 0.9 mm gap and L / D 12 was set at 190 °C. Film formation was carried out at a blow ratio of 3.2 and a draw ratio of 8.1. Therefore, the film thus obtained (total 35 microns) was characterized in terms of mechanical properties, particularly tensile strength (σ b ), elongation at break (ε b ) and modulus of elasticity (E), optical properties (transmittance, haze and transparency) and roughness in the same manner as in Example 1.

Table 4

[0069] As can be understood from Table 3, the layer (i) obtained in Example 1 according to the present invention has mechanical properties and optical properties comparable to those of the layer (i) of Comparative Example 2 based only on PLA, and is suitable for packaging. In particular, the layer (i) according to the present invention has a higher order elongation at break, which means having greater toughness. At the same time, the layer (i) according to the present invention has a greater roughness with respect to both the root mean square roughness Sq with respect to the mean line and the difference Sy between the maximum peak and the maximum trough. Due to the low surface roughness of the PLA-only layer (i) in Comparative Example 2, the application of the coating layer (ii) resulted in poorer adhesion.

[0070] Comparative Example 3 Layer (i) 16 kg / h of poly(butylene sebacate-co-butylene adipate-co-butylene terephthalate) (MFR 5.7 g / 10 min (190 °C; 2.16 kg) and acid value 25 meq / kg) and 24 kg / h of Ingeo 4043D polylactic acid (“PLA”) (MFR 3 g / 10 min (190 °C; 2.16 kg)) were fed to an OMC type twin-screw extruder operated under the following conditions. Screw diameter (D) = 58 mm; L / D = 36; Rotational speed = 140 rpm; Thermal profile = 50 - 180 - 200 x 5 - 160 x 2 °C; Throughput = 40 kg / h; Vacuum degassing was carried out in 8 zones out of 10. The granules thus obtained had an MFR value of 5.9 g / 10 min (at 190 °C; 2.16 kg in accordance with ISO standard 1133-1 “Plastics - determination of the melt mass-flow rate (MFR) and melt volume flow rate (MVR) of thermoplastics - Part 1: Standard method”).

[0071] The granules thus obtained were fed to a Ghioldi model blown film apparatus equipped with a 40 mm diameter screw (L / D 30) operating at 64 rpm with a thermal profile of 120 - 145 - 180 × 2. The film forming head having a 0.9 mm gap and L / D 12 was set at 180 °C. Film formation was carried out at a blow ratio of 3.2 and a draw ratio of 12.5. Therefore, the film thus obtained (total 24 microns) was characterized in the same manner as in Example 1 with respect to mechanical properties, particularly tensile strength (σ b ), elongation at break (ε b ) and modulus of elasticity (E), optical properties (transmittance, haze and transparency) and roughness.

Table 5

[0072] The data in Table 4 have an aliphatic-aromatic polyester to PLA molar ratio similar to that of the mixture of the film layer (i) of Example 1 according to the present invention, but the film layer (i) according to Comparative Example 3 produced in the absence of the styrene-glycidyl ether-methyl methacrylate copolymer is also characterized by good mechanical properties, but shows a much higher roughness with respect to both the root mean square roughness Sq with respect to the mean line and the difference Sy between the maximum peak and the maximum trough (see Table 1). Excessive roughness values impair the uniformity of the coating layer and reduce the barrier effect.

Claims

1. A barrier film comprising at least one biodegradable layer (i) having an elastic modulus higher than 450 MPa and at least one coating layer (ii) in direct contact with a surface of the biodegradable layer (i), layer (i) is made of a mixture containing a polyhydroxyalkanoate constituting a continuous phase and an aliphatic polyester and / or an aliphatic-aromatic polyester constituting a discontinuous phase, and further containing 0.01 to 5 wt % of a crosslinker and / or a chain extender having two or more functional groups; The polyhydroxyalkanoate is selected from the group consisting of lactic acid, polyhydroxybutyrate, polyhydroxybutyrate-valerate, polyhydroxybutyrate-propanoate, polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodecanoate, polyhydroxybutyrate-hexadecanoate, polyhydroxybutyrate-octadecanoate, poly 3-hydroxybutyrate-4-hydroxybutyrate, and mixtures thereof; The aliphatic polyester and / or the aliphatic-aromatic polyester may be poly(1,4-butylene succinate), poly(1,4-butylene succinate-co-adipate), poly(1,4-butylene succinate-co-1,4-butylene azelate), poly(1,4-butylene adipate-co-1,4 butylene terephthalate), poly(1,4 butylene succinate-co-1,4 butylene terephthalate), poly(1,4 butylene azelate-co-1,4 butylene terephthalate), poly(1,4 butylene brassylate-co-1,4 butylene terephthalate), poly(1,4 butylene sebacate-co-1,4 butylene terephthalate), poly(1,4 butylene adipate-co- 1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene azelate-co-1,4-butylene terephthalate), poly(1,4-butylene succinate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene terephthalate); layer (ii) comprises one or more materials selected from metals and their oxides and alkoxides, cellulose and its derivatives, starch and its derivatives, chitosan, synthetic polymers and combinations thereof; A barrier film, wherein the surface of layer (i) is characterized by a root mean square roughness Sq of ≧10 nm and ≦45 nm as measured by atomic force microscopy (AFM).

2. 2. The barrier film of claim 1, wherein the synthetic polymer is selected from polyvinyl alcohol, ethylene vinyl alcohol, polyvinyl acetate, ethylene vinyl acetate, acrylates, organosilanes, and polyethylene glycols.

3. 3. The barrier film according to claim 1 or 2, wherein the mixture comprises 0.01 to 0.45 wt % of a bi- or multi-functional crosslinker and / or chain extender.

4. 4. The barrier film according to any one of claims 1 to 3, wherein the crosslinker and / or chain extender is selected from bi- or multi-functional compounds containing isocyanate, peroxide, carbodiimide, isocyanurate, oxazoline, epoxy, anhydride or divinyl ether groups and mixtures thereof.

5. 5. The barrier film according to claim 1, wherein layer (i) has a breaking elongation (εb) value of ≧150% and ≦400%, measured according to ASTM D882 (23° C., 50% relative humidity, Vo 50 mm / min).

6. 6. The barrier film according to claim 1, wherein the polyhydroxyalkanoate comprises at least 70% by weight of one or more polylactic acids.

7. The aliphatic / aromatic polyester comprises: (a) based on the total dicarboxylic acid components: a1) 30 to 70 mol % of units derived from at least one aromatic dicarboxylic acid; a2) 70 to 30 mol % of units derived from at least one saturated aliphatic dicarboxylic acid; a3) 0 to 5 mol % of units derived from at least one unsaturated aliphatic dicarboxylic acid A dicarboxylic acid component comprising (b) based on the total diol component: b1) 95 to 100 mol % of units derived from at least one saturated aliphatic diol; b2) 0 to 5 mol % of units derived from at least one unsaturated aliphatic diol and a diol component comprising The aliphatic polyester comprises the following components: (c) based on the total dicarboxylic acid components: (c1) 95 to 100 mol % of units derived from at least one aliphatic dicarboxylic acid; (c2) 0 to 5 mol % of units derived from at least one unsaturated aliphatic dicarboxylic acid; A dicarboxylic acid component comprising (d) based on the total diol component: (d1) 95 to 100 mol % of units derived from at least one saturated aliphatic diol; (d2) 0 to 5 mol % of units derived from at least one unsaturated aliphatic diol and a diol component comprising The barrier film according to any one of claims 1 to 6.

8. the bi- or polyfunctional crosslinker and / or chain extender has a peroxide group; and is contained in the film layer (i) in an amount of 0.01 to 0.1% by weight of the total mixture constituting the layer (i); The barrier film according to any one of claims 1 to 7.

9. the bi- or polyfunctional crosslinker and / or chain extender has an epoxy group; and The film layer (i) is contained in an amount of 0.05 to 0.3% by weight of the total mixture constituting the layer (i). Item 8. The barrier film according to any one of items 1 to 7.

10. 10. A barrier film according to any one of claims 1 to 9, wherein the coating layer (ii) is capable of having a barrier effect against gases and liquids.

11. 11. A barrier film according to any one of the preceding claims, wherein the coating layer (ii) comprises a first layer of an organic material, which may be natural and / or synthetic, in contact with layer (i) and a second layer of a metallic material covering the first layer.

12. The film according to any one of claims 1 to 11, further comprising a polymer layer (iii) (multilayer film). Barrier film.

13. 13. The barrier film of claim 12, wherein said layer (iii) comprises one or more polymers selected from polyhydroxyalkanoates, aliphatic / aromatic polyesters of the diacid-diol type which are the same or different from those contained in layer (i), aliphatic polyesters having a melting point of 110°C or less and selected from those contained in layer (i), and mixtures thereof.

14. Use of a barrier film according to any one of claims 1 to 13 for food packaging.

15. Use of a barrier film according to any one of claims 1 to 9 for the production of packaging materials having a barrier effect.

16. A packaging material comprising the barrier film according to any one of claims 1 to 13.

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