Improved oriented PLA based film, method for its production and use thereof

Abstract

The present application relates to a recyclable and / or biodegradable barrier film, methods for its preparation and uses thereof. The improved barrier film comprises PLA as the matrix polymer and PLGA as the barrier polymer, and has outstanding mechanical, optical and barrier properties, and can be easily made and processed. Particularly, the barrier film is an oriented PLA based barrier film obtained or obtainable by stretching a PLA / PLGA blend i, in the form of a sheet, n the longitudinal and / or the transverse direction, wherein the PLA / PLGA blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA.

Description

[0001] IMPROVED ORIENTED PLA BASED FILM, METHOD FOR ITS PRODUCTION AND USE THEREOF

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to biodegradable polylactide (PLA) based materials and films exhibiting high gas barrier properties, particularly useful in packaging applications, and methods for the preparation of such materials and films.

[0004] BACKGROUND OF THE INVENTION

[0005] Packaging materials are generally used to protect and preserve products such as food products. Especially in the case of products with limited shelf-life, in addition to the mechanical properties to physically protect the product, packaging materials are often required to possess adequate barrier properties e.g. from oxygen, water vapour or moisture, dust, etc. Keeping the contents clean, fresh, and safe for the intended shelf life is a primary function. Without an oxygen and / or moisture barrier, the food product or other product contained within the packaging may lose freshness, taste, colour, or may otherwise expire or become inedible or non-useable more quickly than products contained within packaging having such a barrier.

[0006] Currently multilayer structures such as films find many applications in the high-volume packaging industry including food and medical packaging. The combination of several layers of different materials improves the mechanical and physical properties of the structure or film including puncture, tear and heat resistance, and also significantly increases shelflife by controlling the transmission rate of oxygen, carbon dioxide and moisture as well as the concentration of oxygen, carbon dioxide, nitrogen and argon inside the package which is key in preserving the freshness of packaged products for longer period of time. However, multilayer films are essentially impossible to be recycled and / or to be reused.

[0007] The demand for biodegradable polymers and materials with excellent material properties is rapidly growing. Biodegradable polymers can be used in various applications, including as packaging materials. Polylactide, also referred to herein as poly(lactide) or PLA, is a well- known biobased and biodegradable polyester with high strength, transparency and good processability. Currently, large-scale commercialization of poly(lactide) (PLA) has given a viable degradable alternative to the petrochemical-based polymers. PLA can be synthesized by ring-opening polymerization (ROP) of lactide, the cyclic dimer of lactic acid (LA) and through different enzymatic, cationic, anionic, or coordination-insertion polymerization mechanisms. However, PLA articles show high gas transmission rates, which makes it unsuitable for certain packaging applications, such as food and medical packaging.

[0008] There is thus a need in the art for improved PLA based films, particularly for their application in packaging. In particular, there is a need in the art for PLA based films, particularly single layer PLA based films, with improved properties, particularly PLA based films that combine excellent mechanical, optical and gas barrier properties.

[0009] SUMMARY OF THE INVENTION

[0010] The present invention addresses one or more of the above identified needs. The inventors have surprisingly developed a new, renewable barrier film, particularly a mono-layer barrier film, comprising PLA as the matrix polymer and PLGA as the barrier polymer, with well-defined mechanical and barrier properties, good appearance, that can be easily made and easily processed. Particularly, the barrier film of the present application is an oriented PLA based barrier film obtained or obtainable by stretching a PLA / PLGA blend or PLA / PLGA sheet. The oriented PLA / PLGA film according to the present invention is a fully recyclable, industrially compostable polymer / polymer film that combines highly efficient barrier properties with great mechanical and optical properties. Advantageously, the stretching performance of the PLA / PLGA blend during oriented film processing, particularly biaxial stretching performance, was excellent, as evidenced by the absence of any tearing / failing of the film during stretching.

[0011] A first aspect of the present application provides an oriented film comprising a blend of polylactide (PLA) and poly(lactide-co-glycolide) (PLGA), wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA. In particular embodiments, the oriented film is a monoaxially oriented film or a biaxially oriented film, preferably wherein the oriented film is a biaxially oriented film. The oriented film may also be a heat set film.

[0012] In particular embodiments, the PLGA in the blend / oriented film is a crystallizable PLGA, particularly having a glycolide content of at least 75 wt%. Alternatively, the PLGA is a non- crystallizable PLGA, having a glycolide content between 40 and 70 wt%, such as between 40 and 60 wt% or between 40 and 50 wt%. In particular, the PLGA has an MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, measured at 230 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), and / or the PLGA has a melting temperature between 170 and 215 °C, as determined by differential scanning calorimetry (DSC).

[0013] In particular embodiments, the PLA has an MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, measured at 210 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), and / or the PLA has a melting temperature between 150 and 185 °C, as determined by DSC.

[0014] The oriented film particularly has a PLA crystallinity of at least 15%, particularly between 20% and 50% or between 20% and 40%.

[0015] Preferably, the oriented film exhibits one or more of the following: a water vapor transmission rate of less than 160 g / m2.day, as determined at 38 °C and 90% relative humidity in accordance with ASTM D1653, and standardized to 25 pm film thickness., particularly wherein the PLGA in the oriented film is a crystallizable PLGA copolymer and the water vapor transmission rate is less than 100 g / m2.day, as determined at 38 °C and 90% relative humidity in accordance with ASTM D1653, and standardized to 25 pm film thickness;

[0016] - An oxygen transmission rate of less than 250 cc / m2.d.0.1 MPa, as determined at 23 °C and 0% relative humidity according to GB1038-2000, and standardized to 25 pm film thickness, particularly wherein the PLGA in the film is a crystallizable PLGA copolymer and the oxygen transmission rate is less than 75 cc / m2.d.0.1 MPa, as determined at 23 °C and 0% relative humidity according to GB1038-2000, and standardized to 25 pm film thickness; and / or

[0017] - A transmittance at 550 nm of at least 75%, particularly at least 80%, such as ranging from 80% to 95%, as determined by UV-VIS spectrometry.

[0018] A second, related aspect of the present application provides a method for the preparation of an oriented film comprising a blend of PLA and PLGA, comprising the steps of:

[0019] (a) blending or compounding PLA and PLGA to form a polymeric blend comprising PLA and PLGA, wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA;

[0020] (b) forming the polymeric blend comprising PLA and PLGA, either directly or indirectly, into a sheet, particularly in a sheet with thickness between 100 and 750 pm,

[0021] (c) orienting the sheet by stretching the sheet in the longitudinal direction of orientation and / or the transverse direction of orientation, thereby obtaining the oriented film comprising a blend of PLA and PLGA; (d) optionally, annealing the oriented film obtained in step (c), particularly by heating the oriented film at a temperature of at least 100°C, particularly between 100°C and 150°C, for a time period of at least 1s, particularly between 2s and 10s, more particularly between 4s and 6s.

[0022] Preferably, steps (a) and step (b) are performed in a single step.

[0023] In certain embodiments, step (b) is performed by extruding a melt of the polymeric blend of PLA and PLGA, particularly through a flat film extrusion die and at a temperature of 200- 250 °C, and cooling, thereby forming the sheet.

[0024] In certain embodiments, step (c) comprises:

[0025] - stretching the sheet in the longitudinal or in the transverse direction of orientation in a ratio of 1.5 to 6 such as 2 to 5, thereby obtaining a monoaxially oriented film, or

[0026] - stretching the sheet in the longitudinal direction of orientation in a ratio of 1.5 to 6, such as 2 to 5, and in the transverse direction of orientation in a ratio of 1 .5 to 6, such as 2 to 5, thereby obtaining a biaxially oriented film, particularly wherein the stretching of the sheet in the longitudinal direction and in the transverse direction of orientation is performed simultaneously or sequentially, in any order.

[0027] In particular embodiments, step (c) is performed by stretching the sheet at a temperature of at least 50 °C, particularly between 50 °C and 120 °C, more particularly between 60 °C and 90 °C; and / or by stretching the sheet in at least one of the longitudinal or transverse directions of orientation at a stretching speed of at least 0.15 mm / s or at least 1.0 mm / s, particularly at least 5.0 mm / s or at least 10.0 mm / s, such as between 5.0 mm / s and 500 mm / s or between 10.0 mm / s and 250 mm / s.

[0028] A further related aspect relates to the use of an oriented film according to the present invention as a packaging film, a wrapping film, a lidding film, a lamination film or as a film for pouches.

[0029] Another further related aspect relates to the use of a compounded polymer blend comprising PLA and PLGA, such as an extruded polymer blend, for the preparation of an oriented film comprising a blend of PLA and PLGA, particularly an oriented film according to the present application, in a method according to the present application, wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA, particularly wherein the PLGA is a crystallizable PLGA, particularly having a glycolide content ranging between 75 wt% and 95 wt%. DETAILED DESCRIPTION OF THE INVENTION

[0030] When describing the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0031] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0032] In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0033] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while certain embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art.

[0034] The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements, or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of" as used herein comprise the terms "consisting of", "consists" and "consists of".

[0035] As used in the specification and the appended claims, the singular forms "a", "an," and "the" include plural referents unless the context clearly dictates otherwise. By way of example, "a step" means one step or more than one step.

[0036] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art. All publications referenced herein are incorporated by reference thereto. The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1 , 2, 3, 4 when referring to, for example, a number of elements, and can also include 1 .5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of endpoints also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

[0037] The term "about" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / -10% or less, preferably + / -5% or less, more preferably + / -1% or less, of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier "about" refers is itself also specifically, and preferably, disclosed.

[0038] The terms “wt%,” “vol%”, or “mol%” refers to a weight percentage of a component, a volume percentage of a component, or molar percentage of a component, respectively, based on the total weight, the total volume, or total moles of the material, which includes the component.

[0039] When describing the present invention, the terms used are to be construed in accordance with the definitions specified herein, unless a context dictates otherwise.

[0040] In the following passages, different aspects and preferred statements (features) and embodiments and uses of this invention are defined in more detail. Each aspect, statement and embodiment of the invention so defined may be combined with any other aspect, statement and / or embodiment unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features or statements indicated as being preferred or advantageous. Hereto, the present invention is in particular captured by any one or any combination of one or more of the below numbered statements and embodiments, with any other aspect and / or embodiment.

[0041] Statement 1. An oriented film comprising a blend of polylactide (PLA) and poly(lactide-co- glycolide) (PLGA), wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA.

[0042] Statement 2. Statement according to statement 1 , wherein the oriented film is a monoaxially oriented film or a biaxially oriented film, preferably wherein the oriented film is a biaxially oriented film. Statement 3. Statement according to statement 1 or 2, wherein the PLGA is a crystallizable PLGA, particularly having a glycolide content of at least 75 wt%, such as ranging between 75 wt% and 95 wt%, or wherein the PLGA is a non-crystallizable PLGA, particularly having a glycolide content between 40 and 70 wt%, such as between 40 and 60 wt% or between 40 and 50 wt%.

[0043] Statement 4. Statement according to any one of statements 1 to 3, wherein the PLGA has an MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, measured at 230 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), and / or wherein the PLGA has a melting temperature between 170 and 215 °C, as determined by differential scanning calorimetry (DSC).

[0044] Statement 5. Statement according to any one of statements 1 to 4, wherein the PLA has a MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, measured at 210 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), and / or wherein the PLA has a melting temperature between 150 and 185 °C, as determined by DSC.

[0045] Statement 6. Statement according to any one of statements 1 to 5, wherein the oriented film has a PLA crystallinity of at least 15%, particularly between 20% and 50% or between 20% and 40%.

[0046] Statement 7. Statement according to any one of statements 1 to 6, wherein the oriented film is a single layer film.

[0047] Statement 8. Statement according to any one of statements 1 to 7, wherein the oriented film is a heat set film.

[0048] Statement 9 Statement according to any one of statements 1 to 8, wherein the oriented film has a thickness between 5 and 200 pm.

[0049] Statement 10. Statement according to any one of statements 1 to 9, wherein the oriented film exhibits one or more of the following: a water vapor transmission rate of less than 160 g / m2.day, as determined at 38 °C and 90% relative humidity in accordance with ASTM D1653, and standardized to 25 pm film thickness, particularly wherein the PLGA in the oriented film is a crystallizable PLGA copolymer and the water vapor transmission rate is less than 100 g / m2.day, as determined at 38 °C and 90% relative humidity in accordance with ASTM D1653, and standardized to 25 pm film thickness;

[0050] - An oxygen transmission rate of less than 250 cc / m2.d.0.1MPa, as determined at 23 °C and 0% relative humidity according to GB1038-2000, and standardized to 25 pm film thickness, particularly wherein the PLGA in the film is a crystallizable PLGA copolymer and the oxygen transmission rate is less than 75 cc / m2.d.0.1 MPa, as determined at 23 °C and 0% relative humidity according to GB1038-2000, and standardized to 25 pm film thickness;

[0051] - A transmittance at 550 nm of at least 75%, particularly at least 80%, such as ranging from 80% to 95%, as determined by LIV-VIS spectrometry.

[0052] Statement 11. Method for the preparation of an oriented film comprising a blend of PLA and PLGA, particularly for the preparation of an oriented film according to any one of statements 1 to 10, comprising the steps of:

[0053] (a) blending or compounding PLA and PLGA to form a polymeric blend comprising PLA and PLGA, wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA;

[0054] (b) forming the polymeric blend comprising PLA and PLGA, either directly or indirectly, into a sheet, particularly in a sheet with thickness between 100 and 750 pm,

[0055] (c) orienting the sheet by stretching the sheet in the longitudinal direction and / or the transverse direction, thereby obtaining the oriented film comprising a blend of PLA and PLGA.

[0056] Statement 12. Statement according to statement 11 , wherein the PLGA is a crystallizable PLGA, particularly having a glycolide content ranging between 75 wt% and 95 wt%; and / or wherein the PLGA has an MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10min, measured at 230 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011); and / or wherein the PLGA has a melting temperature between 170 and 215 °C, as determined by DSC; and / or wherein the PLA has an MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, measured at 210 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011); and / or wherein the PLA has a melting temperature between 150 and 185 °C, as determined by DSC.

[0057] Statement 13. Statement according to statement 11 or 12, wherein the polymeric blend is prepared by extrusion, particularly by extruding a melt comprising PLA and PLGA at a temperature of 200-250 °C through a die and quench cooling the extrudate.

[0058] Statement 14. Statement according to statement 11 or 12, wherein step (a) and step (b) are performed in a single step.

[0059] Statement 15. Statement according to any one of statements 11 to 14, wherein step (b) is performed by extruding a melt of the polymeric blend of PLA and PLGA, particularly through a flat film extrusion die and at a temperature of 200-250 °C, and cooling, thereby forming the sheet.

[0060] Statement 16. Statement according to any one of statements 11 to 15, wherein step (c) comprises stretching the sheet in the longitudinal or in the transverse direction of orientation in a ratio of 1 .5 to 6, such as 2 to 5, thereby obtaining a monoaxially oriented film.

[0061] Statement 17. Statement according to any one of statements 11 to 15, wherein step (c) comprises stretching the sheet in the longitudinal direction of orientation in a ratio of 1 .5 to 6, such as 2 to 5, and in the transverse direction of orientation in a ratio of 1 .5 to 6, such as 2 to 5, thereby obtaining a biaxially oriented film.

[0062] Statement 18. Statement according to statement 17, wherein the stretching of the sheet in the longitudinal direction and in the transverse direction of orientation is performed simultaneously; or wherein the stretching of the sheet in the longitudinal direction and in the transverse direction of orientation is performed sequentially in any order.

[0063] Statement 19. Statement according to any one of statements 11 to 18, wherein step (c) is performed by stretching the sheet at a temperature of at least 50 °C, particularly between 50 °C and 120 °C, more particularly between 60 °C and 90 °C.

[0064] Statement 20. Statement according to any one of statements 11 to 19, wherein step (c) is performed by stretching the sheet in at least one of the machine or transverse directions of orientation at a stretching speed of at least 0.15 mm / s or at least 1 .0 mm / s, particularly at least 5.0 mm / s or at least 10.0 mm / s, such as between 5.0 mm / s and 500 mm / s or between 10.0 mm / s and 250 mm / s.

[0065] Statement 21 . Statement according to any one of statements 11 to 20, further comprising the step of annealing the oriented film obtained in step (c), particularly by heating the oriented film at a temperature of at least 100 °C, particularly between 100 °C and 150 °C, for a time period of at least 1s, particularly between 2s and 10s, more particularly between 4s and 6s.

[0066] Statement 22. An oriented film comprising a blend of PLA and PLGA, particularly a biaxially oriented film, according to any one of statements 1 to 10, wherein the film is obtained or obtainable by a method according to any one of statements 11 to 21.

[0067] Statement 23. Use of an oriented film according to any one of statements 1 to 10 as a packaging film, a wrapping film, a lidding film, a lamination film or as a film for pouches.

[0068] Statement 24. A compounded polymer blend comprising PLA and PLGA, such as an extruded polymer blend, wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA. Statement 25. Statement according to statement 24, wherein the PLGA is a crystallizable PLGA, particularly having a glycolide content ranging between 75 wt% and 95 wt%; and / or wherein the PLGA has an MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, measured at 230 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), and / or wherein the PLGA has a melting temperature between 170 and 215 °C, as determined by differential scanning calorimetry (DSC).

[0069] Statement 26. Statement according to statement 24 or 25, wherein the PLA has an MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, measured at 210 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), and / or wherein the PLA has a melting temperature between 150 and 185 °C, as determined by DSC.

[0070] Statement 27. Use of the polymer blend according to any one of statements 24 to 26 for the preparation of an oriented film comprising a blend of PLA and PLGA, particularly for the preparation of an oriented film according to any one of statements 1 to 11 , in a method according to any one of statements 11 to 21.

[0071] The present invention is based on the surprising finding that an oriented layer or film comprising a blend of PLA and PLGA can be obtained, which shows good processing behavior, and which combines excellent gas barrier properties and mechanical properties. These properties make the oriented film or layer of the present application particularly advantageous in packaging applications. Hereunder, particularities and properties of the different aspects and statements according to the present invention and the polymers applied therein will be discussed in more detail.

[0072] The present invention generally relates to an oriented film or layer comprising a blend of polylactide (PLA) and poly(lactide-co-glycolide) (PLGA), methods for the preparation of such oriented film and uses thereof, as well as a compounded polymer blend of PLA and PLGA, particularly for its use in the preparation of an oriented film as envisaged herein.

[0073] In a first aspect, the oriented film or layer according to the present invention comprises a blend of polylactide (PLA) and poly(lactide-co-glycolide) (PLGA), wherein the blend comprises 55- 90 wt% PLA and 10-45 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA.

[0074] An oriented film as considered herein refers to a film, sheet, layer or similar structure, that has been stretched in at least one direction, particularly wherein the polymer chains are aligned in the stretch direction. The orientation of the film may be assessed by e.g. polarized light microscopy or by birefringence measurements as known to the skilled person.

[0075] In certain embodiments, the oriented film according to the invention is a monoaxially oriented film or a biaxially oriented film. In particularly preferred embodiments, the oriented film according to the invention is a biaxially oriented film. A monoaxially oriented film is only stretched in the longitudinal or machine direction of orientation, or in the transverse direction of orientation. A biaxially oriented film is stretched in both the longitudinal as well as in the transverse direction of orientation during its manufacturing process. It is understood that the longitudinal direction, also known as the machine direction, is perpendicular to the transverse direction.

[0076] The oriented film as considered herein is made up of a blend comprising PLA as the matrix material and PLGA as the barrier material, in casu comprising 55-90 wt% PLA and 10-45 wt% PLGA, based on the weight of the blend. In certain embodiments, the blend comprises 60- 85 wt% PLA and 15-40 wt% PLGA, based on the total weight of the blend. Optionally, the blend may comprise one or more additives, including but not limited to colorants, slip / anti- block agents, impact modifiers, anti-static agents, chain extenders, compatibilizers, and the like, particularly wherein these additives are present in a concentration of less than 5 wt%, such as less than 4 wt%, less than 3 wt%, less than 2 wt% or even less than 1 wt.%, based on the total weight of the blend.

[0077] In the present application, the terms “PLA”, “polylactide”, “poly(lactide)” and “polylactic acid” are used as synonyms. Polylactide or PLA as used herein refers to a polymer of lactide (monomers). Lactide can exist in three different geometric structures, which have a diastereomeric relationship. The term “lactide” (or “lactide monomer”) as used herein may therefore be L-lactide (derived from two L-lactic acid molecules), D-lactide (derived from two D-lactic acid molecules), meso-lactide (derived from a L-lactic acid molecule and a D-lactic acid molecule), D,L lactide (derived from a 50 / 50 mixture of L-lactide and D-lactide with a melting point of about 126°C). A PLA polymer as defined herein may thus be a polymer of lactide (monomer) selected from the group comprising L-lactide, D-lactide, meso-lactide, D,L lactide and any mixture of two or more thereof. The process for preparing PLA is well-known by the person skilled in the art.

[0078] In certain embodiments, the PLA as envisaged herein is a PLA homopolymer, which comprises at least 98 wt%, at least 99 wt%, or even at least 99.5 wt% of lactide. A PLA homopolymer essentially does not comprise any other monomer which is not a lactide. Such PLA homopolymer may thus consist of lactide, e.g. lactide which is selected from the group comprising L-lactide, D-lactide, meso-lactide, racemic lactide and any mixture of two or more thereof. The PLA as considered herein may be a PLLA or “poly(L-lactic acid)” or a PDLA or “poly(D-lactic acid)”, having an optical purity (called isomeric purity) of the L- or D-isomer, respectively, which is equal to or higher than 94.0 wt% of the PLA, preferably higher than 96 wt%. A PLLA used in the invention thus comprises or essentially consists of lactide monomers, and includes a content of D-isomer lower than 6.0 wt%, preferably lower than 4.0 wt% By analogy, a PDLA used in the invention thus comprises or essentially consists of lactide monomers includes a content of L-isomer lower than 6.0 wt%, preferably lower than 4.0 wt%.

[0079] In certain embodiments, the PLA as considered herein has a melt flow index or MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, more particularly between 1 and 20 g / 10 min or between 1 and 10 g / 10 min, measured at 210 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), for instance as described in the examples section.

[0080] In certain embodiments, the PLA as considered herein has a melting temperature between 150 and 185 °C, as determined by Differential Scanning Calorimetry (DSC).

[0081] In the present application, the term “PLGA” or “poly(lactide-co-glycolide)” or “PLGA copolymer” or “poly(lactide-coglycolide) copolymer” are used as synonyms and refer to a polymer comprising, particularly essentially consisting of, lactide and glycolide. PLGA is a linear copolymer that can be prepared at different ratios between its constituent monomers, lactic acid and glycolic acid according to methods that are well known to the skilled person. For instance, PLGA can be synthesized by ring opening polymerization (ROP) of lactide and glycolide. Depending on the ratio of lactide to glycolide used for the polymerization, different forms of PLGA can be obtained. PLGA is a biocompatible and biodegradable polymer.

[0082] In certain embodiments, the PLGA is a crystallizable PLGA. Advantageously, the presence of crystallized PLGA in the oriented film, particularly biaxially oriented film as considered herein, provides high barrier properties to the film. Crystallized / crystallisable PLGA copolymers can be identified via e.g. DSC measurements by the presence of a melting endotherm and a melting temperature. In particular, a crystallizable PLGA copolymer is a PLGA copolymer that exhibits a DSC melting endotherm after being subject to an isothermal holding treatment for 8 hrs at 100 °C. A crystallizable PLGA copolymer has a glycolide content of at least 75.0 wt%, based on the total weight of the PLGA copolymer. More in particular, a crystallizable PLGA copolymer has a glycolide content between 75.0 wt% and 100 wt%, with 100 wt% excluded, preferably between 75.0 wt% and 99.0 wt% or between 80.0 and 99.0 wt%, more preferably between 85.0 and 98.0 wt% or between 75.0 and 95.0 wt%, between 80.0 and 95 wt% or between 85.0 and 95.0 wt%, based on the total weight of the PLGA copolymer. The determination of the glycolide content in PLGA polymers is known to the skilled person. The glycolide content may be determined by hydrolyzing the PLGA polymer by methanolic potassium hydroxide and transesterification of the hydrolysis products to their corresponding methyl ester. The methyl esters are subsequently separated and quantified by gas chromatography using a polar column, using internal standards for calibration.

[0083] In certain other embodiments, the PLGA is a non-crystallizable PLGA. A non-crystallizable PLGA as used herein has a glycolide content between 40 and 75 wt%, particularly between 40 and 70 wt%, more particularly between 40 and 60 wt% or between 45 and 55 wt%, based on the total weight of the PLGA copolymer.

[0084] In certain embodiments, the PLGA as considered herein has a melt flow index (MFI) ranging between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, more particularly between 1 and 20 g / 10 min or between 1 and 10 g / 10 min, measured at 230 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), for instance as detailed in the examples section.

[0085] In certain embodiments, the PLGA as considered herein has a melting temperature between 170 and 215 °C, as determined by differential scanning calorimetry (DSC).

[0086] In certain embodiments, the oriented film, particularly the biaxially oriented film as considered herein has a PLA crystallinity of at least 15%, particularly between 15% and 50% or between 20% and 50%, more particularly between 20% and 45% or between 20% and 40%. Advantageously, when using a crystallizable PLGA polymer in the blend, crystallization of both PLA and PLGA provides high mechanical and barrier properties upon stretch ing / orienti ng the film or layer.

[0087] The PLA crystallinity of the films is calculated from the cold crystallization and melting enthalpies measured by DSC, in particular by recording a DSC thermogram over a temperature range from 0 to 240 °C at a heating rate of 20 °C / min under a nitrogen gas flow. The crystallinity percentage (XPLA) is calculated using the formula: wherein WPLA represents the weight content of PLA in the sample; AHm. PLA and AHC, PLA represent enthalpies of melting and cold crystallization of PLA, respectively; and AHm. PLA.O represents the melting enthalpy of 100% crystalline PLA, which is 93 J / g.

[0088] In certain embodiments, the oriented film, particularly biaxially oriented film as considered herein, is a heat set or annealed film. Typically, the annealed film has an increased crystallinity compared to the non-annealed film, thus contributing to the improved barrier and mechanical properties of the oriented film. Advantageously, compared to a non-annealed film, an annealed oriented film, particularly an annealed biaxially oriented film as considered herein has an improved dimensional stability and, hence, a reduced shrinkage, particularly in both the longitudinal and the transverse directions of orientation. Furthermore, an annealed oriented film, particularly an annealed biaxially oriented film as considered herein has improved barrier properties, particularly an improved WVTR, and exhibits a higher elongation at break.

[0089] The oriented film, particularly biaxially oriented film as defined in the present application combines outstanding mechanical and optical properties with excellent barrier properties, including but not limited with respect to water vapour and oxygen.

[0090] In certain embodiments, the oriented film, particularly biaxially oriented film as defined herein, exhibits a water vapor transmission rate of less than 160 g / m2.day, as determined at 38 °C and 90% relative humidity in accordance with ASTM D1653, and standardized to 25 pm film thickness. In particular embodiments, the oriented film, particularly biaxially oriented film as defined herein, comprises a crystallizable PLGA copolymer and exhibits a water vapor transmission rate of less than 100 g / m2.day, as determined at 38 °C and 90% relative humidity in accordance with ASTM D1653, and standardized to 25 pm film thickness.

[0091] In certain embodiments, the oriented film, particularly biaxially oriented film as defined herein, exhibits an oxygen transmission rate of less than 250 cc / m2.d.0.1MPa, as determined at 23 °C and 0% relative humidity according to GB1038-2000, and standardized to 25 pm film thickness. In particular embodiments, the oriented film, particularly biaxially oriented film as defined herein, comprises a crystallizable PLGA copolymer and exhibits an oxygen transmission rate of less than 75 cc / m2.d.0.1MPa, as determined at 23 °C and 0% relative humidity according to GB1038-2000, and standardized to 25 pm film thickness.

[0092] In certain embodiments, the oriented film, particularly biaxially oriented film as defined herein, exhibits an excellent transparency. The film transparency may be determined using an UV- VIS spectrometer by assessing the transparency of the film over a wavelength range, such as between 400-800 nm, or at a single wavelength. More in particular, the oriented film, particularly biaxially oriented film as defined herein, exhibits a transmittance at 550 nm of at least 75%, particularly of at least 80%, such as ranging from 80% to 95%, as determined by LIV-VIS spectrometry.

[0093] In certain embodiments, the oriented film, particularly biaxially oriented film as defined herein, exhibits excellent mechanical properties. For instance, the oriented film, particularly biaxially oriented film as defined herein exhibits a tensile strength of at least 85 MPa, particularly a tensile strength of at least 90 MPa, such as ranging from 90 MPa to 150 MPa, and / or exhibits an elongation at break of at least 90%, particularly at least 95%, such as ranging from 95% to 160%; with tensile strength and elongation at bread determined as known to the skilled person, for instance as described in the examples section. In particular embodiments, the oriented film, particularly biaxially oriented film as defined herein, is a non-annealed film and exhibits a tensile strength of at least 100 MPa.

[0094] The oriented film, particularly biaxially oriented film as defined herein, may further have excellent dimensional stability. For instance, the oriented film, particularly biaxially oriented film as defined herein, particularly when annealed, exhibits a shrinkage in the machine or longitudinal direction and / or in the transverse direction of orientation of less than 10%, particularly less than 5%, or less than 3% at 80°C.

[0095] The oriented film or layer, particularly biaxially oriented film or layer according to the invention may be of any suitable thickness, depending on its (end)application. In certain embodiments, an oriented film or layer according to the present invention has a thickness comprised between 5 and 200 pm. Thickness of an oriented film or layer according to the invention may be determined by any technique known to the person skilled in the art. For instance, measurements of thickness can be performed inline by e.g. X-Ray transmission gauges or offline by a micrometer. In certain embodiments the oriented film or layer is a single layer film.

[0096] Due to its advantageous combination of optical, mechanical and barrier properties, the oriented film, particularly the biaxially oriented film as considered herein is particularly suitable as a packaging material, particularly for products with limited shelf-life. A further related aspect of the present invention thus provides the use of an oriented film, particularly a biaxially oriented film as defined elsewhere herein, as a packaging film, a wrapping film, a lidding film, a lamination film or as a film for pouches.

[0097] A related aspect of the present invention provides a method for the preparation of an oriented film comprising a blend of PLA and PLGA, in particular a method for the preparation of an oriented film as considered herein, comprising a blend of PLA and PLGA, with PLA and PLGA as defined elsewhere herein, wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA. Said method comprises the steps of:

[0098] (a) blending or compounding PLA and PLGA to form a polymeric blend comprising PLA and PLGA, wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly comprises 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA;

[0099] (b) forming the polymeric blend comprising PLA and PLGA, either directly or indirectly, into a sheet; and (c) orienting the sheet by stretching the sheet in the longitudinal direction and / or the transverse direction of orientation, thereby obtaining the oriented film comprising a blend of PLA and PLGA.

[0100] Advantageously, the PLA and PLGA blend as considered herein exhibits an excellent processing behaviour, in particular an excellent and smooth stretching or bi-stretching performance, with essentially no tearing of the film during (biaxial) stretching.

[0101] In said method, the PLA and PLGA that are present in the blend are essentially as defined elsewhere herein. Optionally, the blend may comprise one or more additives, including but not limited to colorants, slip / anti-block agents, impact modifiers, anti-static agents, chain extenders, compatibilizers, and the like, as discussed elsewhere herein. In particular embodiments, the PLGA copolymer is a crystallizable PLGA copolymer as discussed elsewhere herein, having a glycolide content of at least 75.0 wt%, based on the total weight of the PLGA copolymer. In particular embodiments, the PLA is selected from the group comprising, and preferably consisting of, poly(L-lactic acid) (PLLA), poly(D-lactic acid) (PDLA), and any mixture thereof, with PLLA and PDLA as discussed elsewhere herein, particularly having an optical purity (called isomeric purity) of the L- or D-isomer, respectively, which is equal to or higher than 94.0 wt% of the PLA, preferably higher than 96 wt%.

[0102] Step (a) is not particularly limited to a specific method for preparing a polymeric blend, and includes any method for blending or compounding PLA and PLGA known to the skilled person. In particular embodiments, the polymeric blend is prepared by extrusion, particularly by extruding a melt comprising PLA and PLGA at a temperature of 200-250°C through a die and cooling, such as quench cooling the extrudate. Preferably, the extrusion temperature does not substantially exceed this temperature range to avoid the risk of polymer decomposition.

[0103] Similarly, step (b) is not particularly limited to a specific method for preparing a polymer sheet. In particular embodiments, step (b) is performed by extruding a melt of the polymeric blend of PLA and PLGA, particularly through a flat film extrusion die and at a temperature of 200- 250 °C, and cooling, thereby forming the sheet. The formed sheet may have a thickness between 100 and 750 pm.

[0104] In particular embodiments, step (a) and step (b) may be performed in a single step.

[0105] In step (c), the sheet may be stretched and oriented in only one direction, thereby obtaining a monoaxially oriented film, or in two perpendicular directions, thereby obtaining a biaxially oriented film.

[0106] In particular embodiments, step (c) comprises stretching the sheet in either the longitudinal or machine direction of orientation, or either in the transverse direction of orientation, thereby obtaining a monoaxially oriented film. The stretching ratio, defined as the length after stretching to the initial length in the stretched direction, may range between 1.5 and 6, such as between 2 and 5 or between 2 and 4. Stated differently, the film is stretched by 1 .5 to 6 times, such as between 2 and 5 or between 2 and 4 times, its original dimension in the stretched direction.

[0107] In particular embodiments, step (c) comprises stretching the sheet in both the longitudinal or machine direction of orientation as well as in the transverse direction of orientation, thereby obtaining a biaxially oriented film. In each direction, the stretching ratio may range between 1.5 and 6, such as between 2 and 5 or between 2 and 4. Stated differently, the film is stretched by 1.5 to 6 times, such as between 2 and 5 times or between 2 and 4 times, its original dimensions in both the longitudinal and transverse direction. In particular embodiments, the stretching of the sheet in the longitudinal direction and in the transverse direction of orientation is performed simultaneously. Alternatively, the stretching of the sheet in the longitudinal direction and in the transverse direction of orientation may be performed sequentially, in any order, i.e. first in one or other of the transverse or longitudinal directions and then, subsequently, in the other direction. The film may be stretched by the same amounts or by different amounts in each of the transverse and longitudinal directions.

[0108] In particular embodiments, step (c) is performed by stretching the sheet at a temperature of at least 50 °C, particularly between 50 °C and 120 °C, more particularly between 60 °C and 90 °C or between 70 °C and 90 °C. In certain embodiments, step (c) is performed by stretching the sheet in at least one of the machine or transverse directions of orientation at a stretching speed or draw speed of at least 0.15 mm / s or at least 1 .0 mm / s, particularly at least 5.0 mm / s or at least 10.0 mm / s, such as between 5.0 mm / s and 500 mm / s or between 10.0 mm / s and 250 mm / s.

[0109] The above indicated stretching conditions and stretching ratios result in films with good optical, barrier and mechanical properties.

[0110] In certain embodiments, the method as considered herein further comprises the step (d) of annealing the oriented film obtained in step (c). In certain embodiments, step (d) comprises heating the oriented film obtained in step (c) at a temperature of at least 100°C, particularly between 100°C and 150°C, for a time period of at least 1s or at least 2s, such as between 1s and 30s, particularly between 2s and 20s or between 2s and 10s, more particularly between 3s and 8s or between 4s and 6s. Advantageously, by implementing an annealing treatment (d), the crystallinity, particularly the PLA crystallinity of oriented film increases, thus contributing to the improved barrier and mechanical properties of the oriented film as considered herein. Advantageously, the annealing treatment as considered herein improves the dimensional stability of the oriented film, resulting in a reduced shrinkage, particularly in both the longitudinal and the transverse directions of orientation.

[0111] The present application further relates to an oriented film or layer, particularly a biaxially oriented film or layer, comprising a blend of PLA and PLGA, as considered herein is, wherein said film or layer is obtained or obtainable by a method according to the present application.

[0112] A further related aspect provides a compounded polymer blend comprising PLA and PLGA which is particularly suitable for the preparation of an oriented film as defined elsewhere herein. The compounded polymer blend comprising PLA and PLGA is preferably an extruded polymer blend, and the polymer blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA.

[0113] In the compounded or extruded polymer blend, the PLA and PLGA that are present in the blend are essentially as defined elsewhere herein. Optionally, the blend may comprise one or more additives, including but not limited to colorants, slip / anti-block agents, impact modifiers, anti-static agents, chain extenders, compatibilizers, and the like, as discussed elsewhere herein.

[0114] In particular embodiments, the PLGA copolymer is a crystallizable PLGA copolymer as discussed elsewhere herein, having a glycolide content of at least 75.0 wt%, based on the total weight of the PLGA copolymer. More in particular, a crystallizable PLGA copolymer has a glycolide content between 75.0 wt% and 100 wt%, with 100 wt% excluded, preferably between 75.0 wt% and 99.0 wt% or between 80.0 and 99.0 wt%, more preferably between 85.0 and 98.0 wt% or between 75.0 and 95.0 wt%, between 80.0 and 95 wt% or between 85.0 and 95.0 wt%, based on the total weight of the PLGA copolymer. In certain other embodiments, the PLGA is a non-crystallizable PLGA, particularly having a glycolide content between 40 and 75 wt%, particularly between 40 and 70 wt%, more particularly between 40 and 60 wt% or between 45 and 55 wt%, based on the total weight of the PLGA copolymer.

[0115] In certain embodiments, the PLGA as considered herein has a melt flow index (MFI) ranging between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, more particularly between 1 and 20 g / 10 min or between 1 and 10 g / 10 min, measured at 230 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), for instance as detailed in the examples section. In certain embodiments, the PLGA as considered herein has a melting temperature between 170 and 215 °C, as determined by differential scanning calorimetry (DSC). In particular embodiments, the PLA is selected from the group comprising, and preferably consisting of, poly(L-lactic acid) (PLLA), poly(D-lactic acid) (PDLA), and any mixture thereof, with PLLA and PDLA as discussed elsewhere herein, particularly having an optical purity (called isomeric purity) of the L- or D-isomer, respectively, which is equal to or higher than 94.0 wt% of the PLA, preferably higher than 96 wt%. In certain embodiments, the PLA as considered herein has a melt flow index or MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, more particularly between 1 and 20 g / 10 min or between 1 and 10 g / 10 min, measured at 210 °C and 2.16 kg, particularly determined according to ISO 1133- 1 (2011), for instance as described in the examples section. In certain embodiments, the PLA as considered herein has a melting temperature between 150 and 185 °C, as determined by Differential Scanning Calorimetry (DSC).

[0116] A further related aspect of the present invention provides the use of said compounded or extruded polymer for the preparation of an oriented film comprising a blend of PLA and PLGA as defined elsewhere herein, particularly in a method as defined elsewhere herein.

[0117] The following examples serve to merely illustrate the invention and should not be construed as limiting its scope in any way. While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes and modifications without departing from the scope of the invention.

[0118] EXAMPLES

[0119] Materials and methodology

[0120] The PLA base resin was Luminy LX575, which is commercially available from TotalEnergies Corbion, with a stereochemical purity of 98% and an MFI of 7g / 10min (210°C, 2.16kg).

[0121] The PLGA1 copolymer used in the examples contained 45 wt% glycolide, 55 wt% L- lactide, based on the total weight of the polymer, and its melt flow index (MFI) at 210°C is 9 g / 10 min (load: 2.16 kg).

[0122] The PLGA2 copolymer used in the examples contained 91 wt% glycolide, 9% wt% L- lactide, and its melt flow index (MFI) at 210°C is 16 g / 10min (load, 2.16kg). PLGA2 is a crystallizable PLGA copolymer and a PLGA crystal melting endotherm can be observed in DSC measurements. All resins were dried using a desiccant air dryer at 80°C for 12h before further processing.

[0123] The PLGA1 and PLGA2 copolymers were produced by melt ring opening polymerization of a mixture of lactide and glycolide in the presence of a conventional catalyst. The molecular weight is controlled via the addition of a specific amount of a conventional initiator. After achieving the desired molecular weight, the conventional catalyst is deactivated by adding a deactivation additive and the excess of monomer is removed under vacuum.

[0124] The glycolide content in the PLGA polymer is calculated as follows. First, 0.5g of the PLGA polymer is hydrolyzed by methanolic potassium hydroxide and the resulting monomers are (trans)esterified to their corresponding methyl esters. The methyl esters are separated using a Thermo Scientific TRACE 1300 Gas Chromatograph and a polar column. Quantification is performed using an internal standard method and resulting chromatograms are analyzed with Chromeleon 7.4 software.

[0125] The melt flow index [(MFI (210°C; 2.16 kg)] is determined according to ISO 1133-1 (2011) as follows. Prior to the measurement, the samples are pre-dried in a Motan MDE40 desiccant hot air dryer for a minimum of 4 hours at 90°C. The MFI is measured on a calibrated Karg Meltflow Basic equipment, which is equilibrated at the set temperature for at least 15 minutes. 4-5g sample is loaded in the cylinder and molten for 5 minutes at 210°C, with the piston loaded and the nozzle closed. After 5 minutes a weight of 2.16kg is placed on the piston and the nozzle opened. The Karg equipment will cut off first extrudate (=waste) and the following extrudate is collected until a next cut off. The last extrudate is also waste. The collected extrudate is weighed and the MFR is calculated using the Karg Software.

[0126] PLA crystallinity of the films is measured using a DSC-8000 apparatus (PerkinElmer, USA) over a temperature range from 0 to 240 °C at a heating rate of 20 °C / min under a nitrogen gas flow. The enthalpies of cold crystallization and melting of PLA in the DSC thermograms are recorded and the crystallinity percentage is calculated using following formula: 100 where I / I / P represents the weight content of PLA; AHm. PLA and AHC, PLA represent enthalpies of melting and cold crystallization of PLA, respectively; and AHm. PLA.O represents the melting enthalpy of 100% crystalline PLA, which is 93 J / g. PLGA crystallinity could also be observed in the DSC thermograms whenever PLGA2 copolymer was used; causing a melting peak around 200°C. The PLGA crystallinity was in line with the expected PLGA crystallinity based on the PLGA concentration in the blend.

[0127] Sample preparation

[0128] Blends, containing about 70 wt% of PLA as matrix material and about 30 wt% of PLGA1 or PLGA2 as barrier material, were prepared by extrusion on a twin-screw, co-rotating extruder with an L / D ratio of 46 (Nanjing Jieya Extrusion Equipment Co., Ltd). Final melt temperature was 210°C for the PLA-PLGA1 blend, and 240 °C for the PLA-PLGA2 bend. The melt was extruded through a strand die, strands were quench cooled in water and pellets were pelletized. A composition containing about 100 wt% PLA, subject to the same extrusion process, was used as a comparative example. All samples also contained a minor amount (0.3 wt%) of Joncryl ADR4468, a polymeric epoxide-functional chain extender, from BASF.

[0129] The composition of the different samples is shown in Table 1.

[0130] Table 1. Composition of the blends used in the preparation of the films. Composition is expressed in wt% based on the total weight of the composition.

[0131] Next, polymer sheets (-350 pm in thickness) were prepared by extruding a melt of the respective blends with a single-screw extruder equipped with a slotted die and quenching with a chill roll. The melt temperature was 240 °C and the temperature of the cooling rolls was set at about 50 °C. Next, the polymer sheets were cut into 9.0x9.0 cm2plaques for simultaneous biaxial stretching.

[0132] Stretching of the plaques was performed on a lab-scale biaxial stretcher (Hefei Puliang Technology Co., Ltd). In all experiments, the plaques were preheated at Theat for a time theat and simultaneously stretched at 3x3 ratio at a constant stretching speed Vstretch, thereby obtaining about 39 pm biaxially oriented films BO-PLA / PLGA1 (samples S5-S8) and BO- PLA / PLGA2 (samples S9-S12). After stretching, part of the biaxially oriented PLA / PLGA films were annealed by holding the films for 30 seconds at 120°C (samples S6, S8, S10 and S12). A comparative example containing about 100 wt% PLA was treated in the same way, thereby obtaining BO-PLA film (samples S1-S4, with S2 and S4 being subject to the annealing treatment).

[0133] The process parameters for obtaining the different film samples are summarized in Table 2.

[0134] Table 2. Processing conditions for making BO PLA based films.

[0135] Measurements Water vapor transmission rate (WVTR) was measured using a Water Vapor

[0136] Transmission Rate Tester (W3 / 060, Labthink, China) at 38 °C and 90% relative humidity in accordance with ASTM D1653. It is expressed in g / m2.day and standardized to 25 pm thickness.

[0137] Oxygen transmission rate (OTR) measurements were performed using a Gas Permeability Tester (C130H, Labthink instruments, China) at 23 °C with 0% relative humidity according to GB1038-2000. It is expressed in cc / m2.day.0,1MPa and standardized to 25 pm thickness.

[0138] The tensile properties of the biaxially oriented films were measured using an Instron 5976 universal tensile tester at room temperature. The rectangular spline used for testing was sampled using a fixed-width sampler with surgical-grade blades. The sample width is 10 mm, and the gauge length is 20 mm. At least five specimens for each sample were tested at a cross-head speed of 10 mm / min.

[0139] The transmittance of the stretched films was tested and analyzed using a LIV-VIS spectrometer (UV-3600 plus) with an integrating sphere (UV-3600 plus). The test wavelength range was 400-800 nm with a test interval of 1 nm.

[0140] The results are summarized in Tables 3 and 4.

[0141] Table 3. Properties of the different BO-PLA based films. Table 4. Mechanical properties of the different BO-PLA based films.

[0142] Based on these results, it can be concluded that:

[0143] The PLA / PLGA blends exhibited a great and very smooth bi-stretching performance, with no tearing of the film during biaxial stretching. - The presence of the PLGA component did not affect the crystallinity of PLA in the BO-

[0144] PLA based films. Samples obtained with the higher stretching speed exhibited a higher PLA crystallinity.

[0145] The oxygen and water vapor transmission data demonstrated that the barrier properties of the PLA film are substantially improved by the addition of the PLGA copolymer in combination with biaxial stretching. The gas barrier properties were higher for the BO-PLA-PLGA film comprising the crystallizable PLGA2 compared to the non-crystallizable PLGA1.

[0146] The transmittance of PLA films is important for their application as packaging material. All films exhibited an excellent transparency. The transmittance of the BO-PLA / PLGA films remained high, generally between 80 and 90% at 550 nm, which is only slightly less than the transmittance of the comparative BO-PLA film (91-93% at 550 nm).

[0147] The BO-PLA / PGLA films had excellent ductile properties, as demonstrated by the elongation at break data exceeding 100%. In particular, inclusion of the non- crystallizable PLGA copolymer even increased the elongation at break compared to the BO-PLA film.

[0148] - Annealing slightly reduced the tensile strength of the BO PLA based films. The tensile strength of the annealed samples was at least 95 MPa and at least 100 MPA for the BO-PLA / PLGA film comprising the crystallizable PLGA and non-crystallizable PLGA, respectively. The tensile strength of the non-annealed BO-PLA / PLGA films exceeded 118 MPa. Annealing also decreased the WVTR of the BO-PLA / PLGA films.

Claims

CLAIMS1. An oriented film comprising a blend of polylactide (PLA) and poly(lactide-co-glycolide) (PLGA), wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60- 85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA.

2. The oriented film according to claim 1 , wherein the oriented film is a monoaxially oriented film or a biaxially oriented film, preferably wherein the oriented film is a biaxially oriented film; and / or wherein the oriented film has a thickness between 5 and 200 pm.

3. The oriented film according to claim 1 or 2, wherein the PLGA is a crystallizable PLGA, particularly having a glycolide content of at least 75 wt%; or wherein the PLGA is a non- crystallizable PLGA, having a glycolide content between 40 and 70 wt%, such as between 40 and 60 wt% or between 40 and 50 wt%.

4. The oriented film according to any one of claims 1 to 3, wherein the PLGA has an MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, measured at 230 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), and / or wherein the PLGA has a melting temperature between 170 and 215 °C, as determined by differential scanning calorimetry (DSC); and / or wherein the PLA has an MFI between 1 and 100 g / 10 min, particularly between 1 and 50 g / 10 min, measured at 210 °C and 2.16 kg, particularly determined according to ISO 1133-1 (2011), and / or wherein the PLA has a melting temperature between 150 and 185 °C, as determined by DSC.

5. The oriented film according to any one of claims 1 to 4, wherein the oriented film has a PLA crystallinity of at least 15%, particularly between 20% and 50% or between 20% and 40%.

6. The oriented film according to any one of claims 1 to 5, wherein the oriented film is a heat set film.

7. The oriented film according to any one of claims 1 to 6, wherein the oriented film exhibits one or more of the following: a water vapor transmission rate of less than 160 g / m2.day, as determined at 38 °C and 90% relative humidity in accordance with ASTM D1653, and standardized to 25 pm film thickness., particularly wherein the PLGA in the oriented film is a crystallizable PLGA copolymer and the water vapor transmission rate is less than 100 g / m2.day, as determined at 38 °C and 90% relative humidity in accordance with ASTM D1653, and standardized to 25 pm film thickness;- An oxygen transmission rate of less than 250 cc / m2.d.0.1MPa, as determined at 23 °C and 0% relative humidity according to GB1038-2000, and standardized to 25 pm filmthickness, particularly wherein the PLGA in the film is a crystallizable PLGA copolymer and the oxygen transmission rate is less than 75 cc / m2.d.0.1 MPa, as determined at 23 °C and 0% relative humidity according to GB1038-2000, and standardized to 25 pm film thickness; and / or- A transmittance at 550 nm of at least 75%, particularly at least 80%, such as ranging from 80% to 95%, as determined by LIV-VIS spectrometry.

8. Method for the preparation of an oriented film comprising a blend of PLA and PLGA, particularly for the preparation of an oriented film according to any one of claims 1 to 7, comprising the steps of:(a) blending or compounding PLA and PLGA to form a polymeric blend comprising PLA and PLGA, wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA;(b) forming the polymeric blend comprising PLA and PLGA, either directly or indirectly, into a sheet, particularly in a sheet with thickness between 100 and 750 pm,(c) orienting the sheet by stretching the sheet in the longitudinal direction of orientation and / or the transverse direction of orientation, thereby obtaining the oriented film comprising a blend of PLA and PLGA;(d) optionally, annealing the oriented film obtained in step (c), particularly by heating the oriented film at a temperature of at least 100°C, particularly between 100°C and 150°C, for a time period of at least 1s, particularly between 2s and 10s, more particularly between 4s and 6s.

9. The method according to claim 8, wherein step (a) and step (b) are performed in a single step.

10. The method according to claim 8 or 9, wherein step (b) is performed by extruding a melt of the polymeric blend of PLA and PLGA, particularly through a flat film extrusion die and at a temperature of 200-250 °C, and cooling, thereby forming the sheet.

11. The method according to any one of claims 8 to 10, wherein step (c) comprises:- stretching the sheet in the longitudinal or in the transverse direction of orientation in a ratio of 1 .5 to 6, such as 2 to 5, thereby obtaining a monoaxially oriented film, or- stretching the sheet in the longitudinal direction of orientation in a ratio of 1.5 to 6, such as 2 to 5, and in the transverse direction of orientation in a ratio of 1.5 to 6, such as 2 to 5, thereby obtaining a biaxially oriented film, particularly wherein the stretching of the sheet in thelongitudinal direction and in the transverse direction of orientation is performed simultaneously or sequentially in any order.

12. The method according to any one of claims 8 to 11 , wherein step (c) is performed by stretching the sheet at a temperature of at least 50 °C, particularly between 50 °C and 120 °C, more particularly between 60 °C and 90 °C; and / or wherein step (c) is performed by stretching the sheet in at least one of the longitudinal or transverse directions of orientation at a stretching speed of at least 0.15 mm / s or at least 1.0 mm / s, particularly at least 5.0 mm / s or at least 10.0 mm / s, such as between 5.0 mm / s and 500 mm / s or between 10.0 mm / s and 250 mm / s.

13. Use of an oriented film according to any one of claims 1 to 7, particularly a biaxial ly oriented film, as a packaging film, a wrapping film, a lidding film, a lamination film or as a film for pouches.

14. Use of a compounded polymer blend comprising PLA and PLGA, such as an extruded polymer blend, for the preparation of an oriented film comprising a blend of PLA and PLGA, particularly an oriented film according to any one claims 1 to 7, in a method according to any one of claims 8 to 12, wherein the blend comprises 55-90 wt% PLA and 10-45 wt% PLGA, particularly 60-85 wt% PLA and 15-40 wt% PLGA, based on the weight of the blend, and wherein the glycolide content of the PLGA is at least 40 wt% based on the weight of the PLGA, particularly wherein the PLGA is a crystallizable PLGA, particularly having a glycolide content ranging between 75 wt% and 95 wt%.

15. An oriented film comprising a blend of PLA and PLGA, particularly a biaxially oriented film, according to any one of claims 1 to 7, wherein the film is obtained or obtainable by a method according to any one of claims 8 to 12.

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