Polylactide-based compositon and uses thereof

Abstract

The present invention relates to a composition comprising polymeso-lactide (PML) and poly-L-lactide (PLA) each with defined properties, and at least one chain extending agent. The invention further relates to substrates coated with a composition of the invention, and to articles comprising or made from such compositions or from such coated substrates. The invention also relates to the use of a composition comprising polymeso-lactide (PML) and poly-L-lactide (PLA) and at least one chain extending agent for various applications, in particular for melt-processing applications such as film production, and extrusion or extrusion coating applications.

Description

[0001] POLYLACTIDE-BASED COMPOSITON AND USES THEREOF

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of polylactide-based compositions. More specifically, the present invention relates generally to melt-processable compositions with improved properties that may be useful for various applications, in particular for applications such as film production, extrusion or extrusion coating applications, and to methods for using the compositions.

[0004] BACKGROUND OF THE INVENTION

[0005] Global awareness of material sustainability has increased the demand for bio-based polymers like poly(lactic acid) (PLA), which are seen as a desirable alternative to fossil-based polymers because they have less environmental impact.

[0006] PLA is a linear, aliphatic thermoplastic polyester, which can be manufactured from renewable resources. Such manufacture may involve the fermentation of starch, sugar, or other renewable organic substrates into lactic acid. PLA can be produced by direct polycondensation of lactic acid, i.e. lactate monomers. Lactic acid is a molecule with one chiral center, and so it exists in two enantiomeric forms, the so-called R-(or D-) enantiomer and the S-(or L-) enantiomer. More frequently, PLA is prepared by ring-opening polymerization (ROP) of lactide, the cyclic dimer of lactic acid, which in turn is usually manufactured by polycondensation of lactic acid into PLA oligomers, followed by de-polymerization of these oligomers by a so-called ‘backbiting’ mechanism in the presence of a suitable catalyst. After purification, the produced lactide can be converted into PLA by means of a ring-opening polymerization reaction (ROP) in the presence of a polymerization catalyst and initiator.

[0007] Besides the fact that it can be obtained from renewable resources, PLA also has the advantage that it can be biodegraded, thus allowing it to be more readily disposed of after use. These two advantageous properties have led to a significant increase in the use of PLA for various applications, ranging from food packaging to biomedical products, textiles, cards, electronic appliances and others.

[0008] Melt processing is one of the main techniques used for the production of PLA products for the medical, textile, plasticulture, and packaging industries. PLA can for instance be melt-processed by injection molding, blow molding, extrusion, extrusion coating, etc. However, PLA has a relative low melt strength, which makes melt-processing in some instances more difficult. For example, in film / sheet extrusion or extrusion coating applications, phenomena such as neck-in and draw instability may occur, resulting in a lower film or coating quality, and inefficient processing conditions such as high extrusion temperatures and / or slow machine speeds.

[0009] In view of the above, there remains a constant need in the art to provide biodegradable polymer materials with improved properties. More particularly, there remains a need in the art to provide a PLA-based material showing improved properties, and in particular showing improved meltprocessability and extrudability, in order to facilitate its processing, e.g. in extrusion applications.

[0010] There also remains a need in the art of improving extrudability of PLA-based polymers while securing processing conditions, such as improved machine speed in extrusion and / or good adhesion to a packaging materials or substrates in extrusion coating applications. There is also a need to improve quality and properties of the resulting melt-processed materials such as polymer- coated materials or substrates. These needs should be achieved with improved economy and without compromising environmental aspects of the resulting product.

[0011] Accordingly, it is an object of the present invention to provide PLA-based compositions with improved properties. It is also an object of the invention to provide PLA-based compositions that may overcome at least some of the above mentioned drawbacks during melt-processing thereof.

[0012] SUMMARY OF THE INVENTION

[0013] It has now surprisingly been found that some or all of the above needs can be attained either individually or in any combination by a PLA-based composition according to the present invention.

[0014] Thus, according to a first aspect, the present invention provides a composition comprising: a) polymeso-lactide (PML) having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 85.0 g / 10 min, and a stereochemical purity of at least 35.0 % D-lactate, b) poly-L-lactide (PLA) having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 40.0 g / 10 min, and a stereochemical purity of at least 85.0 % L-lactate; and c) at least one chain extending agent.

[0015] In accordance with the present invention, the sum of a) polymeso-lactide (PML) and b) poly-L- lactide (PLA) in a composition of the invention is more than 50.0 wt%, with wt% based on the total weight of the composition, and for instance the sum of a) PML and b) PLA in said composition is at least 55.0 wt%, preferably at least 60.0 wt%, preferably at least 70.0 wt%, based on the total weight of the composition. It has been surprisingly found that by combining two different types of lactide-based polymers, having defined properties and at least one chain extending agent, compositions were obtained having excellent mechanical properties and melt-processability, making such compositions particularly suitable for various applications. In particular compositions according to the invention have excellent melt processibility, and are particularly useful in meltprocessing applications including but not limited to extrusion coating applications, and / or for being processed into films or sheets, or layer(s) thereof.

[0016] In a second aspect, the present invention relates to a coated substrate comprising at least one layer of a composition according to the invention, that is coated on at least one surface of said substrate. The coated substrate may be selected from a metal, a textile, a composite material, and a substrate based on (ligno)cellulosic materials.

[0017] In a third aspect, the present invention relates to a process for preparing a coated substrate comprising the step of coating of a composition according to the present invention onto at least one surface of a substrate, preferably a substrate as defined in the present invention, to form a coated substrate. In certain embodiments, a coated substrate is prepared by extrusion coating, lamination coating, suspension coating, dispersion coating, emulsion coating, and preferably by means of extrusion coating.

[0018] For extrusion coating, it is particularly advantageous to be able to run at relative high coating line speed, and at the same time to produce a coating with good adhesion and low coating weight, hence a coating which is not too thick. A balance between these properties is required to obtain an optimized extrusion coating process, and a satisfying coated substrate having good properties. Running at high coating line speed is only advantageous when also properties as adhesion and (low) coating weight can be obtained. When used in extrusion coating applications, the compositions of the invention show improved adhesion on the substrate, improved melt strength and improved melt curtain stability. Using the compositions of the invention therefore allows to carry out extrusion and extrusion coating processes at higher speeds while maintaining operational stability and good adhesion properties. Using a composition according to the invention for coating a substrate by extrusion coating permits to produce a coated substrate with balanced properties; including good adhesion of the coating layer to the substrate, controlled neck-in, at a sufficiently low coating weight while being able to process at much higher extrusion line speed under stable conditions. The inventive compositions provide a better balance in properties to the coated substrates which can be obtained at higher stable coating line speed.

[0019] In a fourth aspect, the present invention relates to an an article comprising a composition according to the present invention and / or a coated substrate according to the present invention. Such articles may include but are not limited to a container, bottle, cup, packaging material, film, sheet, foamed material, bag, wrapping material.

[0020] In a fifth aspect, the present invention also relates to the use of a composition according to the invention in various applications. In certain embodiments, the present invention relates to the use of a composition according to the invention for coating a substrate, preferably a substrate as defined herein, for instance by extrusion coating, by lamination coating, suspension coating, dispersion coating, emulsion coating, preferably by extrusion coating. In certain embodiments, the present invention also relates to the use of a composition according to the invention for producing a film or sheet, or for producing at least one layer in a multilayer film.

[0021] The independent and dependent claims set out particular and preferred features of the invention. Features from the dependent claims may be combined with features of the independent or other dependent claims as appropriate.

[0022] The present invention will now be further described. 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 or statement indicated as being preferred or advantageous may be combined with any other features or statements indicated as being preferred or advantageous.

[0023] Detailed description of the invention

[0024] When describing the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0025] 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.

[0026] As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a composition" means one composition or more than one composition.

[0027] As used herein, the term “and / or” when used in a list of two or more items, means that any one of the listed items can be employed by itself or any combination of two or more of the listed items can be employed. For example, if a list is described as comprising group A, B, and / or C, the list can comprise A alone, B alone, C alone, A and B in combination, A and C in combination, B and C in combination, or A, B, and C in combination.

[0028] 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.

[0029] The recitation of numerical ranges by endpoints includes all intervening values between the lower and upper endpoints, as well as the recited endpoints. Intervening values may be integers or, where applicable, fractions, i.e., more broadly any real numbers such as any rational numbers. For instance: 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). This applies to numerical ranges irrespective of whether they are introduced by the expression “from... to...” or the expression “between... and...” or another expression. Any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, each sub-range between any stated value in a stated range and any other stated value in that stated range is also specifically disclosed. Each sub-range between any stated value in a stated range and either the lower endpoint or the upper endpoint of the stated range is also specifically disclosed. The stated value may be an isolated value or an endpoint of a range subsumed by or overlapping with the stated range. For example, for a stated range with lower endpoint L1 and upper endpoint U1 (i.e., stated range L1-U1) and a stated sub-range nested within the stated range with lower endpoint L2 and upper endpoint U2 (i.e., stated sub-range L2- U2), also specifically disclosed are the subranges L1 -L2, L1-U2, L2-U1 , and U2-U1.

[0030] All references cited in the present specification are hereby incorporated by reference in their entirety. In particular, the teachings of all references herein specifically referred to are incorporated by reference.

[0031] 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 some 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.

[0032] As used herein, the term “about” is used to provide flexibility to a numerical value or range endpoint by providing that a given value may be “a little above” or “a little below” said value or endpoint, depending on the specific context. Unless otherwise stated, use of the term “about” in accordance with a specific number or numerical range should also be understood to provide support for such numerical terms or range without the term “about.” For example, the recitation of “about 30” should be construed as not only providing support for values a little above and a little below 30, but also for the actual numerical value of 30 as well.

[0033] The terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the disclosure described herein are capable of operation in other sequences than described or illustrated herein.

[0034] Reference in this specification may be made to methods that provide “improved” performance (e.g. increased or decreased results, depending on the context). It is to be understood that unless otherwise stated, such “improvement” is a measure of a benefit obtained based on a comparison to methods in the prior art. Furthermore, it is to be understood that the degree of improved performance may vary between disclosed embodiments and that no equality or consistency in the amount, degree, or realization of improved performance is to be assumed as universally applicable.

[0035] 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 of material, or total moles, which includes the component.

[0036] Preferred statements (features) and embodiments of the processes, formulations and uses of this invention are set herein below. Each statement and embodiment of the invention so defined may be combined with any other 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.

[0037] 1 . A composition comprising: a) polymeso-lactide (PML) having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 85.0 g / 10 min, and a stereochemical purity of at least 35.0 % D-lactate, b) poly-L-lactide (PLA) having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 40.0 g / 10 min, and a stereochemical purity of at least 85.0 % L-lactate; and c) at least one chain extending agent wherein the sum of a) PML and b) PLA is more than 50.0 wt%, based on the total weight of the composition.

[0038] 2. Composition according to statement 1 , wherein the sum of a) PML and b) PLA is at least 55.0 wt%, preferably at least 60.0 wt%, preferably at least 70.0 wt%, preferably at least 80.0 wt%, preferably at least 90.0 wt%, preferably at least 95.0 wt%, based on the total weight of the composition.

[0039] 3. Composition according to any one of the preceding statements, wherein said composition comprises said chain extending agent in an total amount of at most 3.0 wt%, preferably between 0.01 and 2.5 wt%, or between 0.01 and 2.0 wt%, or between 0.01 and 1.7 wt%, or between 0.01 and 1 .0 wt%, with wt% based on the total weight of the composition.

[0040] 4. Composition according to any one of the preceding statements, wherein the weight ratio of PML:PLA is equal to or higher than 1 :1 , preferably at least 1.5:1 , or at least 2:1 , or at least 2.5:1 , or at least 3:1.

[0041] 5. Composition according to any one of the preceding statements, wherein the weight ratio of PML:PLA is at most 4.5:1 , or at most 4:1 , or at most 3.5:1.

[0042] 6. Composition according to any one of the preceding statements, wherein the weight ratio of PML:PLA is comprised between 4.5:1 and 1 :1 , or between 4:1 and 1.5:1 , or between 3.5:1 and 2:1.

[0043] 7. Composition according to any one of the preceding statements, wherein said composition comprises PML in an amount of between 15.0 and 85.0 wt%, preferably between 30.0 and 80.0 wt%, preferably between 45.0 and 80.0 wt%, preferably between 55.0 and 75.0 wt%, preferably between 55.0 and 73.0 wt%, with wt% based on the total weight of the composition.

[0044] 8. Composition according to any one of the preceding statements, wherein said composition comprises PLA in an amount of between 10.0 and 80.0 wt%, preferably 20.0 and 50.0 wt%, preferably between 22.5 and 45.0 wt%, preferably between 25.0 and 35.0 wt%, with wt% based on the total weight of the composition.

[0045] 9. Composition according to any one of the preceding statements, wherein said chain extending agent is selected from the group consisting of an epoxide-functionalized chain extending agent, a peroxide-functionalized chain extending agent, an anhydride-functionalized chain extending agent, an isocyanate-functionalized chain extending agent, an oxazoline chain extending agent and oxazine chain extending agent, a vinyl-acetate-based polymer, and any combinations thereof.

[0046] 10. Composition according to any one of the preceding statements, wherein said chain extending agent is an epoxide-functionalized chain extending agent, and preferably is an epoxycontaining copolymer based on styrene, acrylic ester and / or methacrylic ester, and preferably the chain extending agent is an epoxy functional styrene-acrylate copolymer.

[0047] 11 . Composition according to any one of the preceding statements, wherein the epoxide- functionalized chain extending agent has an average of at least 2, such as from 3 to 30 epoxy groups per molecule / per chain.

[0048] 12. Composition according to any one of the preceding statements, wherein the epoxide- functionalized chain extending agent has a number average molecular weight Mn of from 400 to 8500 g / mol.

[0049] 13. Composition according to any one of the preceding statements, further comprising one or more additives, preferably selected from the group comprising lubricants, antioxidants, heat stabilizers, ultraviolet stabilizers, fillers, plasticizers, colorants, flame retardants, and antistatic agents and any combinations thereof, and preferably wherein such additives are present in said composition in a total amount of less than 5.0 wt%, such as less than 3.0 wt%, preferably less than 1.0 wt%.

[0050] 14. Composition according to any one of the preceding statements, wherein said composition has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of at least 5.0 g / 10 min, or at least 10.0 g / 10 min, or at least 20.0 g / 10 min, or at least 40.0 g / 10 min, or at least 50.0 g / 10 min. 15. Composition according to any one of the preceding statements, wherein said PML has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.5 and 80.0 g / 10 min, such as between 3.0 and 80.0 g / 10 min, or between 10.0 and 80.0 g / 10 min, or between 30.0 and 80.0 g / 10 min, or between 50.0 and 75.0 g / 10 min, or between 50.0 and 65.0 g / 10 min.

[0051] 16. Composition according to any one of the preceding statements, wherein said PLA has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 25.0 g / 10 min, or between 2.0 and 15.0 g / 10 min, or between 2.0 and 10.0 g / 10 min.

[0052] 17. Composition according to any one of the preceding statements, wherein said PML has a stereochemical purity of between 35.0 and 60.0 % D-lactate, or between 40.0 and 55.0 % D- lactate, or between 47.0 and 52.0 % D-lactate.

[0053] 18. Composition according to any one of the preceding statements, wherein said PLA has a stereochemical purity of at least 86.5 % L-lactate, or at least 88.0 % L-lactate, or at least 90.0 % L-lactate, or at least 92.5 % L-lactate, or at least 95.0 % L-lactate, or at least 97.5 % L- lactate, or at least 99.0 % L-lactate.

[0054] 19. Composition according to any one of the preceding statements, wherein composition has a zero shear viscosity (etaO) measured at 190°C, 0.1 rad / s, lower than 3500 Pa.s, such as lower than 1500 Pa.s, or lower than 1000 Pa.s, or lower than 500 Pa.s.

[0055] 20. Composition according to any one of the preceding statements, wherein said PML has a zero shear viscosity (etaO) measured at 190°C, 0.1 rad / s, lower than 3800 Pa.S, or lowerthan 1800 Pa.s, or lower than 1500 Pa.s, or lower than 500 Pa.s.

[0056] 21 . Composition according to any one of the preceding statements, wherein said PML is amorphous.

[0057] 22. Composition according to any one of the preceding statements, wherein said composition is a coating composition for coating a substrate by extrusion coating, by lamination coating, or by suspension coating, preferably by extrusion coating.

[0058] 23. A coated substrate comprising at least one layer of a composition, according to any one of the preceding statements 1 to 22, that is coated on at least one surface of said substrate.

[0059] 24. The coated substrate according to statement 23, wherein said substrate is selected from a metal, a textile, a composite material, a substrate based on (ligno)cellulosic materials. 25. The coated substrate according to any one of the preceding statements 23-24, wherein said substrate is a substrate selected from the group comprising paper, paperboard, cartonboard, wood, fiberboard, textile material, material based on paperpulp.

[0060] 26. The coated substrate according to any one of the preceding statements 23-25, wherein said substrate has a basis weight prior to coating of at least 0.5 g / m2, such as at least 1 .0 g / m2; or at least 10.0g / m2; or at least 25.0 g / m2.

[0061] 27. The coated substrate according to any one of the preceding statements 23-26, wherein said coated substrate has a coating weight ranging from 1.0 to 50.0 g / m2; preferably a weight of from 2.0 to 45.0 g / m2; preferably a weight of from 2.5 to 40.0 g / m2; preferably a weight of from 3.0 to 35.0 g / m2.

[0062] 28. The coated substrate according to any one of the preceding statements 23-27, wherein said substrate is coated by a process selected from the group comprising extrusion coating, lamination coating, suspension coating, emulsion coating, dispersion coating, and preferably by extrusion coating.

[0063] 29. Process for preparing a coated substrate comprising the step of coating of a composition according to any one of statements 1 to 22 onto at least one surface of a substrate to form a coated substrate.

[0064] 30. Process according to statement 29, when said coating is performed by extrusion coating, lamination coating, suspension coating, emulsion coating, dispersion coating, preferably by extrusion coating.

[0065] 31 . Process according to any one of statements 29 to 30, comprising the steps of: a) melting said composition, preferably a composition according to any one of statements 1 to 22, in an extruder to form a molten composition; b) extruding the molten composition through a die to form a film of molten composition; c) coating said film of molten composition onto at least one surface of a substrate thereby obtaining a substrate having a layer of said molten composition coated on at least one surface thereof, d) pressing the layer of said molten composition onto the substrate, and e) cooling the layer of the molten composition pressed onto the substrate thereby obtaining a coated substrate. 32. Process according to any one of statements 29 to 31 , wherein said substrate is as defined in any one of statements 24 to 27.

[0066] 33. Process according to any one of the preceding statements 29-32, comprising the step of separately feeding said polymeso-lactide (PML), said poly-L-lactide (PLA), and said chain extending agent, preferably each as defined in any one of statements 1 to 22, to said extruder, to form a composition as defined in any one of statements 1 to 22.

[0067] 34. Process according to any one of the preceding statements 29-33, wherein said composition is dried prior to use thereof, preferably dried to a temperature of at least 20°C, such as at least 30 °C, preferably for at least 4 hours.

[0068] 35. Process according to any one of the preceding statements 29-34, wherein said composition is molten in said extruder to a temperature of at least 150°C, preferably at least 165 °C, and preferably to at most 190°C or at most 170 °C.

[0069] 36. Process according to any one of the preceding statements 29-35, wherein the substrate is subjected to a corona treatment or a flame treatment prior to coating thereof, preferably wherein said flame treatment comprises subjecting the substrate to a temperature of between 75 and 90°C, in the presence of an oxidizing gas, such as propane.

[0070] 37. Process according to any one of the preceding statements 29-36, wherein said coating composition is coated onto at least one surface of said substrate at a coating line speed of at least 80 m / min, preferably at least 100 m / min, preferably at least 110 m / min, more preferably at least 120 m / min.

[0071] 38. Process according to one of the preceding statements 29-37, wherein the air gap between the die and the surface of the substrate to be coated is at most 150 mm, preferably at most 130 mm.

[0072] 39. Process according to any one of the preceding statements 29-38, wherein the layer of said molten coating composition is pressed onto the substrate by supplying the substrate comprising said layer between a nip roll and a chill roll.

[0073] 40. Process according to any one of the preceding statements 29-39, wherein the layer of the molten coating composition pressed onto the substrate is cooled by contacting the layer of the molten coating composition with a chill roll having a temperature of about 15 to 35°C.

[0074] 41 . An article comprising or consisting of a composition according to any one of statements 1-22, and / or a coated substrate according to any one of statements 23-28,

[0075] 42. The article according to statement 41 , wherein said article is a container, bottle, cup, packaging material, film, sheet, foamed material, bag, wrapping material.

[0076] 43. Use of a composition according to any one of statements 1-22 for coating a substrate, for instance by extrusion coating, lamination coating, suspension coating, emulsion coating, dispersion coating, and preferably by extrusion coating.

[0077] 44. Use of a composition according to statement 43, wherein said substrate is as defined in any one of statements 24 to 27.

[0078] 45. Use of a composition according to any one of statements 1 to 22 for producing a film or sheet.

[0079] 46. Use of a composition according to any one of statements 1 to 22 for producing at least one layer in a multilayer film.

[0080] 47. The use according to any one of statements 45 to 46, wherein said film, or sheet, or said layer is produced by a process selected from cast film extrusion, blown film extrusion, injection stretch blow moulding, extrusion blow moulding and extrusion lamination, or combinations thereof.

[0081] Hereunder, particularities of the composition according to the invention and its uses will be discussed in more detail.

[0082] Polylactide resins are made industrially by converting lactic acid to lactide, which is then polymerized. Two molecules of lactic acid can condense, with the elimination of two molecules of water, to form a 3, 6-dimethyl-1 ,4-dioxane-2, 5-dione, which is commonly referred to as "lactide". Polylactide is thus a polymer of a lactide (monomer).

[0083] Lactide molecules can take one of three forms: 3S,6S-3,6-dimethyl-1 ,4-dioxane-2, 5-dione (S,S- lactide or L-lactide), 3R,6R-3,6-dimethyl-1 ,4-dioxane-2, 5-dione (R,R-lactide or D-lactide), and 3R,6S-dimethyl-1 ,4-dioxane-2, 5-dione (R,S-lactide or meso-lactide). L-lactide and D-lactide are a pair of enantiomers, while meso-lactide is a stereoisomer. The term “lactide” 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), or a mixture of two or more of the above. A 50 / 50 mixture of L-lactide and D-lactide with a melting point of about 126°C is often referred to in the literature as D, L-lactide or racemic lactide (and is also denoted as “rac-Lactide” or “racemic lactide” or “rac-lactide” herein). In general, polylactides can be obtained by polymerizing of L-lactide, D-lactide, meso-lactide, racemic lactide or mixtures thereof.

[0084] The present invention is directed to a composition that comprise two specific types of polylactide resins, i.e. a poly-L-lactide as well as polymeso-lactide, each having defined properties, as recited herein

[0085] More specifically, the present invention relates in a first aspect to a composition which comprises: a) polymeso-lactide (PML) having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 85.0 g / 10 min, and a stereochemical purity of at least 35.0 % D-lactate, b) poly-L-lactide (PLA) having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 40.0 g / 10 min, and a stereochemical purity of at least 85.0 % L-lactate; and c) at least one chain extending agent.

[0086] The composition according to the invention is a composition wherein the sum of a) PML and b) PLA is more than 50.0 wt%, based on the total weight of the composition.

[0087] In certain preferred embodiments, the sum of a) PML and b) PLA in said composition is at least 55.0 wt%, or at least 60.0 wt%, or at least 70.0 wt%, or at least 80.0 wt%, or at least 90.0 wt%, or at least 95.0 wt%, based on the total weight of the composition.

[0088] It has been surprisingly found that by combining two different types of lactide-based polymers, and a chain extending agent, compositions were obtained having excellent mechanical properties and processability, making such compositions particularly suitable for various uses, including for coating application such as extrusion coating.

[0089] The first component in the composition is polymeso-lactide. The term "polymeso-lactide" or “polymesolactide” or “PML” as used herein means a polymer containing mainly repeating units derived from meso-lactide (meso-3,6-dimethyl-1 ,4-dioxane-2, 5-dione). Thus, the term PML as used herein refers to a polymer containing repeating units that are mainly from meso-lactide. Meso-lactide is the cyclic diester of a D-lactic acid and a L-lactic acid. Essentially, the polymerization of meso-lactide yields a polymer wherein the D-lactic acid units and the L-lactic acid units are distributed quite regular in the polymer chain. There could be a reaction by two L- lactic acids units or two D-lactic acids units (head to head reaction) resulting in the sequence -(L- D-D-L-)nor -(D-L-L-D-)n or there can be a reaction of the L-lactic acid unit with a D-lactic acid unit (head to tail reaction) resulting in the sequence -(D-L-D-L)n. In certain embodiments, a PML polymer as defined herein is a polymer of meso-lactide (monomer) as defined herein only, i.e. such polymer does not comprise any other monomer which is not meso-lactide.

[0090] A polymeso-lactide (PML) as applied in the present composition, has a stereochemical purity of at least 35.0 % D-lactate. In certain embodiments of the invention, the PML may have a stereochemical purity of between 35.0 and 60.0 % D-lactate, or between 40.0 and 55.0 % D- lactate, or between 47.0 and 52.0 % D-lactate. In other words, a polymeso-lactide (PML) as applied in the present composition, has at least 70 % of meso-lactide. Examples of polymesolactide polymers for use in the present composition include for instance PML having a D-lactate content of 47.0, 47.5, 48.0, 48.5, 49.0, 49.5, 50.0, 50.5, 51.0, 51.5, 52.0 %. The “%” as used herein when referring to % D-lactate or % L lactate is meant to refer to the ratio between L-lactate and D-lactate present in the polymer. The % D-lactate refers to the total amount of D-lactate divided by the total amount of the sum of the L-lactate and D-lactate in the polymer. The % L- lactate refers to the total amount of D-lactate divided by the total amount of the sum of the L- lactate and D-lactate in the polymer. In an example, the ratio of D-lactate and L-lactate in the polymeso-lactide polymers as applied in the present invention is about 1 :1.

[0091] The L-lactate and D-lactate content, and hence stereochemical purity, of a poly-mesolactide as applied herein, may be determined using methods known in the art, such as chiral gas chromatography of methyl lactates after methylation of the original sample (as explained in the example section).

[0092] A polymeso-lactide (PML) as applied in the present composition has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 85.0 g / 10 min. In certain embodiments, the melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of the polymeso-lactide is between 2.5 and 80.0 g / 10 min, such as between 3.0 and 80.0 g / 10 min, or between 10.0 and 80.0 g / 10 min, or between 30.0 and 80.0 g / 10 min, or between 50.0 and 75.0 g / 10 min, or between 50.0 and 65.0 g / 10 min.

[0093] In preferred embodiments, the polymeso-lactide has low viscosity. For instance, in certain preferred embodiments of the invention, the PML applied in the present composition has a zero shear viscosity (etaO) measured at 190°C, 0.1 rad / s, lower than 3800 Pa.S, such as lower than 1800 Pa.s, or lower than 1500 Pa.s, or lower than 500 Pa.s. Zero shear viscosity may be determined as explained in the example section. In certain embodiments, the PML as applied in the present composition has a free acid content of less than 5.0 meq / kg. The free acid content (free acidity) refers to the amount of free carboxylic acid groups in the polymer and is expressed in milli-equivalents per kg (meq / kg). Free acid content can be determined as explained in the example section.

[0094] In certain other embodiments, the PML resin applied in the present invention has a free acid content of 5.0 meq / kg or higher. Such PML resins may be formed using methods known in the art by using an initiator compound containing one or more carboxyl groups, or containing one or more carboxyl groups and one or more hydroxyl groups. Lactic acid, or dimers or oligomers of lactic acid are for instance suitable initiators.

[0095] In preferred embodiments, the polymeso-lactide as applied herein is amorphous. By "amorphous", it is meant that the polymeso-lactide contains no more than 5 J / g of crystallites after being heated at 110°C in air for one hour. The sample is previously heated to at least 220°C to melt any crystallites and then quenched by rapidly cooling to room temperature (23 ± 3°C). The quenched sample is then heated at 110°C for one hour and again quenched by cooling to room temperature. Crystallinity then is conveniently measured using differential scanning calorimetry (DSC) methods according to methods known in the art. A convenient test protocol for making DSC measurements is to heat a 5-10 milligram sample from 25°C to 225°C at 20°C / minute under air, on a Mettler Toledo DSC 3+ calorimeter running STARe V.16 software, or equivalent apparatus.

[0096] A composition according to the present invention may comprise a polymeso-lactide as defined herein in an amount of at least 15.0 wt%, preferably at least 30.0 wt%, preferably at least 45.0 wt%, preferably at least 50.0 wt%, preferably at least 55.0 wt%, with wt% based on the total weight of the composition. In certain embodiments, the amount of the polymeso-lactide in a composition of the invention is preferably at most 85.0 wt%, more preferred at most 80.0 wt%, more preferred at most 75.0 wt%, even more preferred at most 73.0 wt%, with wt% based on the total weight of the composition. In certain embodiments, a composition of the invention comprises PML in an amount of between 15.0 and 85.0 wt%, preferably between 30.0 and 80.0 wt%, preferably between 45.0 and 80.0 wt%, preferably between 50.0 and 75.0 wt%, preferably between 55.0 and 73.0 wt%, with wt% based on the total weight of the composition.

[0097] A polymeso-lactide, as applied in the present composition, may be produced by polymerizing meso-lactide according to methods that are known in the art using catalysts and reaction conditions customary for lactide polymerization. For instance, polymerization of meso-lactide into polymeso-lactide is carried out by means of a ring-opening polymerization in the presence of a catalyst, preferably a metal catalyst, and optionally one or more initiators, such as e.g. a primary aliphatic alcohol. The same catalysts that as used in the polymerization of L-lactide or D-lactide, such as for instance a metal-containing catalyst, powdered zinc, Lewis acids (e.g., zinc chloride and antimony trifluoride), or organometallic compounds, may be used to polymerize mesolactide. Polymerization can be conducted batch-wise, semi-continuously or continuously. Suitable polymerization temperatures preferably are from about 125°C to about 225°C, or from about 160 to about 200°C. Residence times and polymerization temperatures are selected to produce a PML polymer with desired properties.

[0098] The second component in the present composition is poly-L-lactide. The terms “PLA”, and “poly- L-lactide” are used herein interchangeably and refer to a polymer containing mainly repeating units derived from L-lactide. More in particular, the terms “PLA”, and “poly-L-lactide” as used herein refer to a polylactide that has a stereochemical purity of at least 85.0 % L-lactate. In other words, the terms “PLA”, and “poly-L-lactide” as used herein refer to a polylactide that has less than 15.0 % D-lactate. The % L-lactate or % D-lactate as applied herein intends to refer to the ratio between L-lactate and D-lactate in the polymer as explained above.

[0099] A person skilled in the art will understand that the term “D-lactate” as used herein when referring to poly-L-lactide refers to D-lactic acid units that may originate from, i.e. be present through, D- lactide and / or meso-lactide, or be generated through racemization during polymerization.

[0100] The L-lactate and D-lactate content, and hence stereochemical purity, may be determined using methods known in the art, such as chiral gas chromatography of methyl lactates after methylation of the original sample (as explained in the example section).

[0101] In preferred embodiments of the present invention, the poly-L-lactide as applied in the composition of the invention is a homopolymer, i.e. such polymer does not comprise any other monomer which is not a lactide.

[0102] In certain embodiments of the invention, it is preferred that the poly-L-lactide as applied in the compositions of the present invention has a stereochemical purity of at least 86.5 % L-lactate, or at least 88.0 % L-lactate, or at least 90.0 % L-lactate, or at least 92.5 % L-lactate, or at least 95.0 % L-lactate, or at least 97.5 % L-lactate, or at least 98.0 % L-lactate, or at least 98.5 % L-lactate, or at least 99.0 % L-lactate, or at least 99.5 % L-lactate. In certain embodiments, the PLA as applied in the compositions of the present invention has a stereochemical purity of at most 99.9% L-lactate, or of at most 99.7 % L-lactate. In certain embodiments, the poly-L-lactide used in the present process has a content of D-lactate content lower than 12.0 %, or lower than 10.0 %, or lower than 8.0 %, or lower than 5.0 %, or lower than 2.0 %. Examples of poly-L-lactide polymers for use in a process according to the invention include for instance PLA having an L-lactate content of 1 .5 or 2.0 or 2.5 or 3.0 or 3.5 or 4.0 or 4.5 or 5.0 or 5.5 or 6.0%.

[0103] In certain embodiments, the poly-L-lactide as applied in the present invention is not amorphous.

[0104] In certain embodiments, it is preferred that the poly-L-lactide is a semi-crystalline grade in which the ratio of L-lactate to D-lactate units is 90:10 to 100:0 or 10:90 to 0:100, preferably 92:8 to 100:0 or 8:92 to 0:100.

[0105] In certain other embodiments, the PLA as applied in the present composition has a free acid content of less than 5.0 meq / kg. The free acid content (free acidity) refers to the amount of free carboxylic acid groups in the polymer and is expressed in milli-equivalents per kg (meq / kg). Free acid content can be determined as explained in the example section.

[0106] In certain other embodiments, the PLA resin applied in the present invention has a free acid content of 5.0 meq / kg or higher. Such PLA resins may be formed using methods known in the art by using an initiator compound containing one or more carboxyl groups, or containing one or more carboxyl groups and one or more hydroxyl groups. Lactic acid, or dimers or oligomers of lactic acid are for instance suitable initiators.

[0107] A PLA as applied in the present composition has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 40.0 g / 10 min. In certain preferred embodiments, PLA as applied in the present composition has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 25.0 g / 10 min, or between 2.0 and 15.0 g / 10 min, or between 2.0 and 10.0 g / 10 min.

[0108] A composition according to the present invention preferably comprises a poly-L-lactide as defined herein in an amount of at least 10.0 wt%, preferably at least 20.0 wt%, preferably at least 22.5 wt%, preferably at least 25.0 wt%, with wt% based on the total weight of the composition. In certain embodiments, the amount of the poly-L-lactide in composition of the invention is preferably at most 80.0 wt%, more preferred at most 50.0 wt%, even more preferred at most 45.0 wt%, with wt% based on the total weight of the composition. In certain embodiments, a composition of the invention comprises PLA in an amount of between 10.0 and 80.0 wt%, preferably between 20.0 and 50.0 wt%, preferably between 22.5 and 45.0 wt%, preferably between 25.0 and 35.0 wt%, with wt% based on the total weight of the composition. The process for preparing PLA is well-known by the person skilled in the art. The poly-L-lactide as applied in the present composition, may be produced by polymerizing lactide according to methods that are known in the art using customary catalysts and reaction conditions. For instance, polymerization of L-lactide into poly-L-lactide is carried out by means of a ring-opening polymerization in the presence of a catalyst, preferably a metal catalyst, and optionally one of more initiators, such as e.g. a primary aliphatic alcohol. Polymerization can be conducted batch- wise, semi-continuously or continuously. Suitable polymerization temperatures preferably are from about 125°C to about 225°C, or from about 160 to about 200°C. Residence times and polymerization temperatures are selected to produce a PLA polymer with desired properties.

[0109] The third component in a composition of the invention is a chain extending agent, herein also denoted as “chain extender”.

[0110] The term “chain extending agent” as used herein refers to a chemical compound that has at least one reactive functionality that react with functional groups on the linear polymer chains to expand the molecular chain and increase the molecular weight. The reactive functionalities of these chain extending agents can for instance be an epoxide, hydroxide, isocyanate, oxazoline, oxazine, tris phosphite, peroxide.

[0111] Preferably, a composition of the invention comprises such chain extending agent in an total amount of at most 3.0 wt%, preferably between 0.01 and 2.5 wt%, or between 0.01 and 2.0 wt%, or between 0.01 and 1 .7 wt%, or between 0.01 and 1 .0 wt%, with wt% based on the total weight of the composition.

[0112] Chain extending agents as used herein may be selected from the group consisting of an epoxide- functionalized chain extending agent, a peroxide-functionalized chain extending agent, an anhydride-functionalized chain extending agent, an isocyanate-functionalized chain extending agent, an oxazoline chain extending agent and oxazine chain extending agent, a vinyl-acetate- based polymer, including vinyl-acetate-based homopolymers, copolymers, and terpolymers, and any combinations thereof.

[0113] In some embodiments the chain extending agent is an epoxide-functionalized chain extending agent, also denoted herein as an epoxy functional compound. As used herein a “epoxy functional compound” is a compound which structure comprises at least one epoxy functionality.

[0114] Suitable epoxy functional compounds include epoxidized fats or oils and epoxy-containing copolymers based on styrene, acrylic ester and / or methacrylic ester. In certain preferred embodiments, the chain extending agent is an epoxide-functionalized chain extending agent has an average of at least 2, such as from 3 to 30 epoxy groups per molecule / per chain, or from 3 to 15 epoxy groups per molecule / per chain.

[0115] In certain preferred embedment, the chain extending agent is an epoxide-functionalized chain extending agent preferably as defined herein, and preferably an epoxy-containing copolymer based on styrene, acrylic ester and / or methacrylic ester, more preferably of the styrene- glycidylether-methylmethacrylate type, which is present in said composition in an amount of at most 3.0 wt%, preferably between 0.01 and 2.5 wt%, or between 0.01 and 2.0 wt%, or between 0.01 and 1.7 wt%, or between 0.01 and 1.0 wt%, with wt% based on the total weight of the composition.

[0116] Preferred epoxide-functionalized chain extending agent include epoxy-containing copolymers based on styrene, acrylic ester and / or methacrylic ester, preferably of the styrene-glycidylether- methylmethacrylate type. The units which bear epoxy groups are preferably glycidyl (meth)acrylates. Copolymers having a glycidyl methacrylate content of greater than 20, more preferably greater than 30 and even more preferably greater than 50 wt% of the copolymer will be found particularly advantageous. The epoxy equivalent weight (EEW) in these polymers is preferably in the range from 150 to 3000 and more preferably in the range from 200 to 500 g / equivalent. The weight-average molecular weight Mw of the polymers is preferably in the range from 2000 to 25 000 g / mol and particularly in the range from 3000 to 8000 g / mol. The number average molecular weight Mn of the polymers is preferably in the range from 400 to 6000 g / mol and particularly in the range from 1000 to 4000 g / mol.

[0117] In certain preferred embedment, the chain extending agent is an epoxide-functionalized chain extending agent preferably as defined herein, and preferably an epoxy-containing copolymers based on styrene, acrylic ester and / or methacrylic ester, more preferably of the styrene-glycidylether-methylmethacrylate type. having a Mw of in the range from 2000 to 25 000 g / mol and preferably in the range from 3000 to 8000 g / mol, having a number average molecular weight Mn in the range from 400 to 6000 g / mol and particularly in the range from 1000 to 4000 g / mol, and

[0118] - which is present in said composition in an amount of between 0.01 and 2.0 wt%, or between 0.01 and 1 .7 wt%, with wt% based on the total weight of the composition. Epoxy-containing copolymers of the abovementioned type are commercially available, for example from BASF under the Joncryl® ADR brand. Joncryl® ADR 4400, Joncryl® ADR 4368 and Joncryl® ADR 4300 are suitable examples for use in the present invention. Joncryl ADR 4400, has the following characteristics: molecularweight 7100 g / mol, glass transition temperature Tg = 65°C, an epoxy group equivalent 485 g / mol. Joncryl® ADR 4300, has the following characteristics: molecular weight of 5500 g / mol, a Tg of 56°C, and an epoxy equivalent weight of 445 g / mol. Joncryl® ADR 4368, has the following characteristics: molecularweight of 6800 g / mol, a Tg of 54°C, and an epoxy equivalent weight of 285 g / mol.

[0119] In the present invention, the chain extending agent, such as those listed above, may be used neat (i.e. added directly) or as a masterbatch to the composition of the invention.

[0120] In certain embodiments a composition of the invention preferably has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of at least 5.0 g / 10 min, or at least 10.0 g / 10 min, or at least 20.0 g / 10 min, or at least 40.0 g / 10 min, or at least 50.0 g / 10 min.

[0121] In certain embodiments a composition of the invention has a zero shear viscosity (etaO) measured at 190°C, 0.1 rad / s, lower than 3500 Pa.s, or lower than 1500 Pa.s, or lower than 1000 Pa.s, or lower than 500 Pa.s.

[0122] Compositions according to the present invention may further comprise limited amounts of one or more additives. Suitable additives may for instance be selected from the group comprising lubricants, antioxidants, heat stabilizers, ultraviolet stabilizers, fillers, plasticizers, colorants, flame retardants, antistatic agents, and any combinations thereof. Preferably such additives, if present, are present in said composition in a total amount of less than 5.0 wt%, such as less than 3.0wt%, preferably less than 1 .0 wt%.

[0123] In the composition of the present invention, the sum of the amount of PLA and PML in a composition of the invention is more than 50.0 wt%, with wt% based on the total weight of the composition. In certain embodiments, it is preferred that total amount of PML and PLA, based on the total weight of the composition, is at least 55.0 wt%, such as at least 60.0 wt%, preferably at least 70.0 wt%, preferably at least 80.0 wt%, preferably at least 90.0 wt%, preferably at least 95.0 wt%, based on the total weight of the composition.

[0124] In certain embodiments, a composition of the invention is provided wherein the weight ratio of PML:PLA is equal to or higher than 1 :1 , preferably at least 1.5:1 , or at least 2:1 , or at least 2.5:1 , or at least 3:1. In certain embodiments, a composition of the invention is provided wherein the weight ratio of PML:PLA is at most 4.5:1 , or at most 4:1 , or at most 3.5:1. In certain embodiments, a composition of the invention is provided wherein the weight ratio of PMLPLA is comprised between 4.5:1 and 1 :1 , or between 4:1 and 1.5:1 , or between 3.5:1 and 2:1.

[0125] Compositions of the invention can be made by blending the PML, the poly-L-lactide and the chain extending agent(s) in appropriate amounts.

[0126] In certain embodiments, the composition of the invention is prepared by separately blending, i.e. separately mixing, the PML, the PLA and the chain extender component each as defined herein. In certain embodiments the PML and the PLA, as defined herein, may first be mixed with one another, after which the chain extender component as defined herein is added to the mixture of PML and PLA. The present composition thus in certain embodiments provides physical mixtures of PML, PLA and chain extender, each as defined herein. Such composition of the invention may then be further processed, e.g., by melt blending, to pellets or the like.

[0127] In some preferred embodiments, a composition of the invention may comprise between 50.0 and 75.0 wt% of polymeso-lactide, with wt% based on the total weight of the composition, having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 85.0 g / 10 min, and preferably between 50.0 and 75.0 g / 10 min, and a stereochemical purity of at least 35.0 % D-lactate, and between 22.5 and 45.0 wt%, of poly-L-lactide, with wt% based on the total weight of the composition, having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 40.0 g / 10 min, and preferably between 2.0 and 10.0 g / 10 min, and a stereochemical purity of at least 85.0 % L-lactate; and between 0.01 and 2.50 wt%, or between 0.01 and 2.0 wt% of chain extending agent, with wt% based on the total weight of the composition,

[0128] - wherein the sum of the amount of PLA and PML in the composition is more than 50.0 wt%, with wt% based on the total weight of the composition and preferably is at least 55.0 wt%, or at least 60.0 wt%, or at least 75.0 wt% based on the total weight of the composition; optionally wherein the weight ratio of PML: PLA in said composition is equal to or higher than 1 :1 , preferably at least 1.5:1 , or at least 2:1 , or at least 2.5:1 , or at least 3:1.

[0129] In some preferred embodiments, a composition of the invention may comprise between 55.0 and 73.0 wt%, of polymeso-lactide with wt% based on the total weight of the composition, having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 50.0 and 75.0 g / 10 min, and a stereochemical purity of at least 40.0 % D-lactate, and between 25.0 and 35.0 wt%, of poly-L-lactide, with wt% based on the total weight of the composition, having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 10.0 g / 10 min, and a stereochemical purity of at least 90.0 % L-lactate; and between 0.01 and 2.0 wt%, of chain extending agent, with wt% based on the total weight of the composition,

[0130] - wherein the sum of the amount of PLA and PML in the composition is more than 70.0 wt%, with wt% based on the total weight of the composition and preferably is at least 80.0 wt%, or at least 90.0 wt% with wt% based on the total weight of the composition, optionally wherein the weight ratio of PML: PLA in said composition is equal to or higher than 1 :1 , preferably at least 1.5:1 , or at least 2:1 , or at least 2.5:1 , or at least 3:1.

[0131] In some preferred embodiments, the composition as defined herein comprises: at most 3.0 wt% based on the total weight of the composition of an epoxide-functionalized chain agent, from 45.0 to 80.0 wt%, based on the total weight of the composition of a polymeso-lactide, having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 85.0 g / 10 min, or between or between 50.0 and 75.0 g / 10 min, and having a stereochemical purity of 40.0 and 55.0 % D-lactate, from 22.5 and 45.0 wt%, of a poly-L-lactide, having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 15.0 g / 10 min, or between 2.0 and 10.0 g / 10 min; and having a stereochemical purity of at least 95.0 % L-lactate,

[0132] - wherein the sum of said polymeso-lactide and said poly-L-lactide is at least 70.0 wt %, preferably at least 80.0. wt%, based on the total weight of the composition; optionally wherein the weight ratio of PML: PLA is equal to or higher than 1 :1 , preferably at least 1.5:1 , or at least 2:1 , and optionally wherein the weight ratio of PML: PLA is at most 4.5:1 , or at most 4: 1.

[0133] In some preferred embodiments, the composition as defined herein comprise between 0.01 and 2.0 wt%, based on the total weight of the composition of an epoxy functional styrene-acrylate copolymer; from 55.0 to 73.0 wt%, based on the total weight of the composition of a polymeso-lactide, having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 50.0 and 75.0 g / 10 min, and having a stereochemical purity of 40.0 and 55.0 % D-lactate, from 25.0 to 35.0 wt%, of a poly-L-lactide, having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 15.0 g / 10 min, or between 2.0 and 10.0 g / 10 min; and having a stereochemical purity of at least 95.0 % L-lactate,

[0134] - wherein the sum of said polymeso-lactide and said poly-L-lactide is at least 80.0 wt%, preferably at least 90.0 wt%, based on the total weight of the composition. optionally wherein the weight ratio of PML:PLA is comprised between 4.5:1 and 1 :1 , or between 4:1 and 1.5:1 , or between 3.5:1 and 2:1.

[0135] A composition according to the present invention is melt processable. As used herein, the term “melt processable” refers to the capacity of the composition as defined herein to be processed by melting. Such processes may include but are not limited to extrusion, blow moulding, compression moulding and injection moulding. The present invention thus provides a composition having excellent processability making it particularly suitable for various applications.

[0136] In certain embodiments, the present invention relates to the use of a composition according to the invention for coating a substrate. In some embodiments, the invention provides the use of a composition according to the invention for coating a substrate as defined herein, by a process selected from the group comprising but not limited to extrusion coating, lamination coating, suspension coating, emulsion coating, and dispersion coating. In some preferred embodiments, a composition of the invention is used for coating a substrate as defined herein by means of extrusion coating.

[0137] As used herein the term “extrusion coating” refers to a technique that permits the extrusion of a thin coating layer onto a substrate. As used herein the term “lamination coating” refers to a technique that involves combining two or more substrates together by 'bonding' them together with a coating. As used herein the term “suspension coating” refers to a technique that involves applying a suspension by, for instance a slot die to a substrate, and then drying the coating. “Dispersion coating” refers to a technique that involves applying a polymer dispersion on a substrate. “Emulsion coating” refers to a technique that involves applying a emulsion on a substrate. Methods used for applying solutions and dispersion on a substrate may include for instance bar, knifes, rolls. For instance, “bar coating” refers to a technique wherein a solution of the coating is spread across a substrate by a cylindrical bar with wire spiralling around it. The gaps between the wire and the substrate control how much solution is allowed through. This determines the film thickness. “Knife coating” refers to a technique wherein an excess of coating material is applied to the substrate and removed by a metering blade to achieve the desired coating thickness. “Roll coating” refers to a technique wherein rollers are used to apply a coating to a substrate.

[0138] In certain embodiments, compositions of the invention are particularly suitable coating composition for coating a substrate. According to the present invention, the composition of the invention can be coated onto any substrate to which it will adhere.

[0139] Therefore, in certain embodiments, in some embodiments the present invention also encompasses a substrate coated with a composition according to the invention. In certain embodiments, the present invention also relates to a coated substrate comprising at least one layer of a composition according to the invention that is coated on at least one surface of said substrate.

[0140] In certain embodiments, the substrate is a selected from a metal, a textile, a composite material, a substrate based on (ligno)cellulosic materials. In certain embodiments, said substrate is a cellulosic substrate or a lignocellulosic substrate, and preferably a substrate selected from the group comprising paper, paperboard, cartonboard, wood, fiberboard, textile material, material based on paperpulp.

[0141] For instance, the substrate may be selected from the group comprising, a cellulosic material such as paperboard, paper, cardboard, fibreboard, wood, a wood veneer, or other boardstock; a textile, which may be, for example, made up of woven, knitted, entangled and / or melt-bonded fibres; a polymeric film or sheet, which may be thermoplastic or thermoset material; a metal sheet; a composite material; natural and synthetic paper, polymer films, and aluminum foil, or any other material that is capable of being processed through the melt extrusion coating apparatus.

[0142] Various weights of substrate can be utilized. In certain embodiments, the coated substrate according to the invention has a basis weight, herein also referred to as grammage, prior to coating of at least 0.5 g / m2, such as at least 1 .0 g / m2; or at least 10.0 g / m2; or at least 25.0 g / m2.

[0143] In certain embodiments, a coated substrate according to the invention has a coating weight ranging from 1 .0 to 50.0 g / m2; preferably a weight of from 2.0 to 45.0 g / m2; preferably a weight of from 2.5 to 40.0 g / m2; preferably a weight of from 3.0 to 35.0 g / m2.

[0144] In another aspect, the present invention relates to a process for preparing a coated substrate comprising the step of coating of a composition according to the invention onto at least one surface of a substrate to form a coated substrate, preferably a substrate as defined herein. Coating may be performed by means of different methods, such as but not limited to extrusion coating, lamination coating, suspension coating, emulsion coating, dispersion coating, as explained above.

[0145] In certain embodiments, compositions of the invention are particularly useful for making coated substrates by means of an extrusion coating process, due in part to their high melt strength and good processability. In general, extrusion coating is meant include various types of substrate coating processes using an extruder to force a coating composition through a die and includes, for example, curtain coating (i.e. , the formation of a film of molten composition).

[0146] In some embodiment, the present invention provides a process, comprising the steps of: a) melting said composition, preferably a composition as defined herein, in an extruder to form a molten composition; b) extruding the molten composition through a die to form a film of molten composition; c) coating said film of molten composition onto at least one surface of a substrate thereby obtaining a substrate having a layer of said molten composition coated on at least one surface thereof, d) pressing the layer of said molten composition onto the substrate, and e) cooling the layer of the molten composition pressed onto the substrate thereby obtaining a coated substrate.

[0147] Equipment suitable for performing extrusion coating is known in the art. In general, equipment employed for extrusion coatings is similar to that used for the extrusion of flat film. A thin molten film from the extruder is drawn down into the nip between a chill roll and a pressure roll positioned below a die. The pressure between these two rolls forces the film onto the substrate. The substrate moves at a speed faster than the extruded film, and hence draws the film to a desired thickness. The molten film is cooled with a chill roll.

[0148] In certain embodiments of the above process, a molten composition is formed in an extruder. The PML, PLA and chain extender component as defined herein may be separately feed to an extruder, to form a composition as defined herein. For instance the components mya be fed into a twin-screw extruder where they are melted, mixed, and brought to the reaction temperature at least partially through mechanically generated heat formed by operating the extruder screws. Further temperature control can be provided by controlling the extruder jacket temperature. The process may be performed, for example, by introducing the poly-L-lactide and the polymeso- lactide into an upstream section of an extruder barrel, melting the resin(s) and bringing them to reaction temperature. The chain extending agent is then introduced in a downstream section of the extruder barrel where it is mixed with the PLA and PML resin(s) that are already at reaction temperature. A small temperature drop may be seen at the point of mixing, but this is generally small because the relative proportion of the chain extender is small. If the temperature of the mixture drops below the reaction temperature at this point, the reaction temperature is recovered rapidly. Alternatively, the different components of a composition of the invention may be added to a hopper from which they are fed to an extruder.

[0149] In some embodiments, it is preferred that the composition or polymer components thereof, is / are dried prior to use thereof, preferably dried to a temperature of at least 20°C, such as at least 30 °C, preferably for at least 4 hours. The drying step has the advantage of reducing degradation of the polymers used in the composition, and hence reducing or avoiding molecular weight degradation. For instance, this can be done using a conventional in-line drying apparatus. The PLA and PML may be conveyed from such in-line dryer to the hopper without exposure to the ambient atmosphere.

[0150] In some embodiments of the present process the composition is molten in said extruder to a temperature of at least 150°C, preferably at least 165 °C, and preferably to at most 190°C or at most 170 °C. While high temperatures are required for the coating processes, the temperature cannot be too high when processing a composition comprising PLA and PML polymers as defined herein. The composition must maintain a degree of cohesion so that the composition sticks together as a good molten composition film during application of the composition onto the substrate surface.

[0151] The molten composition of the invention may then be extruded through a suitable die, e.g. a slit die. The temperature of a composition of the invention at the (slit) die may be, for example 170° C to 270° C, with a preferred temperature range being 210 °C to 260° C. and a more preferred temperature range being 225 °C to 245 °C. Higher temperatures can lead to thermal degradation of the polymer resin(s). Lower temperatures lead to poor adhesion and other processing difficulties.

[0152] In the present process, a substrate may be continuously pulled through a coating zone located below the (slit) die, such that film curtain falls onto the substrate and forms a coating. Typically the substrate is fed from roll, over nip roll and chill roll, whereby nip roll and / or chill roll may be driven and thus may provide the necessary force to pull substrate through coating zone. In some embodiments of the process, the substrate is subjected to a flame treatment prior to coating thereof. Preferably such flame treatment comprises subjecting the substrate to a temperature of between 75 and 90°C, in the presence of an oxidizing gas, such as propane. In some embodiments of the process, the substrate is subjected to a corona treatment prior to coating thereof.

[0153] The vertical distance between die opening and the point of contact with the substrate is known as the “air gap”. The air gap preferably is as small as possible consistent with geometrical constraints imposed by the design of the equipment (in particular the chill roll diameter), so cooling is minimized in the melt curtain and the viscosity of the composition does not increase excessively before coming into contact with the substrate. In some embodiments, it is preferred in the present process that the air gap between the die and the surface of the substrate to be coated is at most 150 mm, preferably at most 130 mm.

[0154] Because typically a coating zone is located below the die, the film of molten composition (film curtain) must fall downward through the atmosphere from die opening into coating zone, where it contacts the substrate and forms a coating thereon. Pressure is then applied to the coated substrate to marry the layers together and promote good adhesion, and the coating is cooled, preferably to 50° C or below. These steps can be performed sequentially (application of pressure followed by cooling) or simultaneously. For instance, In certain embodiments the layer of said molten coating composition is pressed onto the substrate by passing the substrate comprising said layer between a nip roll and a chill roll. In certain embodiments of the present process the layer of the molten coating composition pressed onto the substrate is cooled by contacting the layer of the molten coating composition with a chill roll having a temperature of about 15 to 35°C.

[0155] At industrial scale, line speed has a large effect on draw ratio, with higher line speeds correlating to higher draw ratios (other things being constant). “Line speed” or “’’coating line speed” as used herein, refer to the linear rate of movement of a substrate through the coating installation. The line speed may be, for example, at least 50 meters per minute, but the advantages of the invention are best realized at higher line speeds, and therefore higher draw ratios. A preferred line speed is at least 80 meters per minute, at least 100 meters per minute, at least 120 meters per minute or at least 140 meters per minute. The line speed may be, for example, up to 400 meters per minute, up to 350 meters per minute, up to 300 meters per minute, up to 250 meters per minute, up to 200 meters per minute, up to 180 meters per minute or up to 160 meters per minute. In some embodiments of the present process the composition the coating composition is coated onto at least one surface of said substrate at a coating line speed of at least 80 m / min, preferably at least 100 m / min, preferably at least 110 m / min, more preferably at least 120 m / min. Another feature relevant during extrusion coating process is the “neck-in” phenomenon. This applies when the width of a molten film composition (film curtain) decreases, so the width of the applied coating is less than the length of the (slit) opening of (slit) die. The present process allows neck-in to be controlled and in some instances even reduced.

[0156] A non-limiting example of an extrusion coating installation which is suitable to carry out a process of the invention may and apply a composition of the invention onto a substrate for instance be as follows. The installation is generally a part of a larger apparatus that may include, for example, apparatus for holding, tensioning and feeding a substrate; various pretreatment and / or posttreatment apparatus such as gas treatment apparatus, substrate pre-heating apparatus, one or more additional coating stations at which, for example, a second coating layer is applied to a surface of the substrate and / or a coating layer may be applied to the opposite surface of the substrate; means for supplying and marrying a second substrate layer atop the composition coating to produce a laminate; apparatus for feeding a polymer composition to a (slit) die; apparatus for trimming or otherwise cutting the coated substrate; apparatus for moving the substrate through the process; apparatus for rolling or otherwise packaging the coated substrate; various metering devices and process control devices; apparatus for supplying a chilled liquid to a chill roll, and the like.

[0157] Thus, the present process, using a composition according to the invention for coating a substrate shows several advantages.

[0158] It allows a coated substrate to have a continuous and smooth coating surface. That is, a coating surface without significant breaks or holes therein.

[0159] The compositions of the invention exhibit more stable processing and provide extrusion coating operational efficacy, resulting in coated substrates with balanced properties. Particularly, using the inventive compositions results in an extrusion coating process showing good processability, and extrusion coated substrates are obtained showing good adhesion, at an affordable coating weight, and with limited neck-in.

[0160] The process of the invention can be carried out at relatively high line speeds, while maintaining operational stability and at the same time producing a coating with good adhesion and low coating weight, hence a coating which is not too thick.

[0161] In certain embodiments, compositions of the invention may also be particularly suitable for producing a film or sheet. Compositions of the invention may also be particularly suitable for producing a layer from a multi-layer structure or material. Therefore, in certain other embodiments, the present invention therefore also relates to the use of a composition according to the invention for producing a film or sheet, and / or for producing at least one layer in a multilayer film.

[0162] Differences between films and sheets are related to their technical characteristics. For instance, films typically have a thickness of less than 0.25 mm, while sheets typically exceed 0.25 mm in thickness, with some reaching several centimeters.

[0163] Films comprising a composition of the invention may consist of one layer (also called monolayer film) or may comprise two, three or more layers (also called multilayer films). Such multilayer film may comprise one or more layers of the same biodegradable polymer composition or more than one layer of different biodegradable polymer compositions as described above. The multilayer films may also comprise additional layers prepared from polymers or polymer composition different from the composition of the invention. Examples of such two- and three layer films are films having the following layer sequences, wherein A denotes a composition of the invention and B denotes another polymer composition different from the composition according to the invention: for instance: A / B, A / B / A, B / A / B.

[0164] Additionally, films or sheets may be stretched either mono- or biaxially.

[0165] Films, sheets, and multilayer structures may be produced by processes known by person skilled in the art, e.g. by cast film extrusion, blown film extrusion, injection stretch blow moulding, extrusion blow moulding, extrusion lamination, or combinations thereof.

[0166] The present invention also relates in another aspect to an article comprising or consisting of a composition according to the present invention, and / or a coated substrate according to the present invention. Preferred articles that can be produced using a composition according to the present invention, and / or a coated substrate according to the present invention comprise for instance, but are not limited to a container, bottle, cup, packaging material, film, sheet, foamed material, bag, wrapping material.

[0167] In certain embodiments, the coated substrate or the article according to the invention is compostable and / or biodegradable.

[0168] The term “compostable” as used herein refers to a material capable of biodegradation at specified conditions (i.e. a certain temperature, timeframe, etc.). At the end of the composting process, for example in an industrial composting plant, only natural products remain (water, carbon, biomass).

[0169] The term “biodegradable” as used herein, refers to a material breaking down into substances such as water, carbon and biomass with the help of microorganisms. The process of biodegradation is therefore a natural chemical process and depends on the environmental conditions as well as on the material or application itself. Consequently, the process and its outcome can vary considerably To be labelled a biodegradable material, there is no time limit set on when the product breaks down.

[0170] In some embodiments, the article according to the present invention, or the substrate coated with a composition of the present invention is a recyclable material. The term “recyclable material” refers to a material that can be recovered or diverted from the waste stream through available processes and infrastructure and can be collected, processed and returned to use in form of raw materials or goods.

[0171] The invention will now be illustrated by the following, non-limiting illustrations of particular embodiments of the invention.

[0172] EXAMPLES

[0173] 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.

[0174] Materials

[0175] The following polymer and other materials were used in the examples.

[0176] “PLA1” is a poly-L-lactide having a stereochemical purity of 96 % of L-lactate (L-isomer), MFI (190°C, 2.16kg) of 3 g / 10 min, and is available from TotalEnergies Corbion, Gorinchem, The Netherlands, under the name Luminy LX175.

[0177] “PLA2” is a poly-L-lactide having a stereochemical purity of 98 % of L-lactate (L-isomer), MFI (190°C, 2.16kg) of 10 g / 10 min, and is available from TotalEnergies Corbion, Gorinchem, The Netherlands, under the name Luminy LX530.

[0178] “PML1” is a polymeso-lactide having a stereochemical purity of 49.2 % of D-lactate (D-isomer), MFI (190°C, 2.16kg) of 71 g / 10 min, and a Tg of 49 °C.

[0179] “PML2” is a polymeso-lactide having a stereochemical purity of 49.2 % of D-lactate (D-isomer), MFI (190°C, 2.16kg) of 13 g / 10 min, and a Tg of 48 °C.

[0180] “PML3” is a polymeso-lactide having a stereochemical purity of 49.1 % of D-lactate (D-isomer), MFI (190°C, 2.16kg) of 3 g / 10 min, and a Tg of 49 °C. The PML1 , PML2, and PML3 resins were produced by melt-polymerizing a meso-lactide monomer having a free acid content of less than 5 meq / kg and a D-content of about 49 % at a temperature of 170 to 220°C using a polymerization catalyst as conventionally applied for lactide polymerization, and a suitable initiator, e.g. a primary aliphatic alcohol. The molecular weight, and therefore the MFI of the resulting polymeso-lactide resins, was controlled by varying the content of initiator during the polymerization reaction according to practices known in the art.

[0181] The material denoted “MB1” corresponds to a masterbatch consisting of 25 wt % Joncryl ADR 4400 in PLA1 . Joncryl ADR 4400, available from BASF, is an epoxy-functionalized styrene-acrylate copolymer, having a molecular weight of 7100 g / mol, a Tg of 65°C, and an epoxy equivalent weight of 485 g / mol.

[0182] Methodology

[0183] Melt flow rate

[0184] The melt flow index (MFI) of a PLA, a PML, or a composition, is measured in accordance with Condition D as described in ISO1133 (2005), at a temperature of 190 °C and a test weight of 2.16 kg.

[0185] Relative molecular weight

[0186] Relative molecular weight parameters Mn, and Mwcan be determined using Gel Permeation Chromatography (GPC) with an ELSD detector. In particular, an Agilent HPLC Infinity II system can be used with chloroform (HPLC grade, stabilized with 1% ethanol) and 5% methanol (HPLC grade) as solvent at a flow rate of 1.0 mL / min. The size exclusion columns used can be a PLgel 5pm Guard column (50x7.5mm) and two PLgel 5pm MIXED-C columns (300x7.5mm) connected in series at 35°C column oven temperature. 1-15 mg of a sample is weighed in a 20 ml crimp cap vial and 15 mL chloroform is added thereto. The suspension obtained is shaken for 2h at 50°C, filtered over a 0.45 pm filter, transferred to a 2 ml vial and injected to the GPC system for analysis. A calibration curve of narrow dispersity polystyrene standards is prepared versus which the molecular weights are reported.

[0187] Stereochemical purity (L / D content)

[0188] The stereochemical purity of a poly-L-lactide (PLA) or a polymeso-lactide (PML) as provided herein can be assessed after destructive methylation. To that end 0.1 g of a sample of PLA or PML is brought into a crimp cap vial, subsequently 2.0 g of dichloromethane (pure, Acros Organics) and 5.0 g of methanol (J.T. Baker) are added and the sample is allowed to dissolve for 2 hours at 70°C. After cooling down to room temperature, 3.0 g of Amberlyst 15 (ion exchange resin, dry, Acros Organics) is added and the reaction is allowed to proceed for 22 hours at 80°C. After cooling down to room temperature, the sample is subjected to chiral gas chromatography separation on a Thermo Focus GC equipped with a CP-Chirasil-dex CB separation column. This achieves separation of the R- (or D) and S- (or L-)methyl lactates, the ratio of which finally determines the stereochemical purity of the sample.

[0189] Free acid content (acidity level)

[0190] The free acid content (free acidity) of a PI_A or PML resin may be expressed as amount of free carboxylic acid groups in milli-equivalents per kg (meq / kg), and may be measured by potentiometric titration of a sample of the polymer, using sodium methylate or potassium methylate in water-free methanol. A suitable titration device may be a Mettler Toledo T5 titrator.

[0191] Zero Shear Viscosity and Melt Strength

[0192] The zero shear viscosity of a PI_A or PML or a composition as applied in the present invention may be determined as follows.

[0193] A zero-shear viscosity value (q0), in Pascal-seconds at 190° C, is obtained via a creep test that is conducted on an Anton Paar Physica MOR 301 Rheometer. This rotational Rheometer is fitted with an electric heating plate and hood which can heat to 400°C and are cooled by pressurized air. Furthermore a parallel plate set-up is used in which the top plate has a diameter of 25 mm.

[0194] Frequency Sweeps are used to measure a complex viscosity.

[0195] The parallel plate set-up is allowed to heat to 190°C after which a dried sample is applied. The top plate and hood are allowed to lower until a gap of 5 mm between the parallel plates is reached. Subsequently the sample is allowed to melt for 5 minutes at the set temperature (190°C). After 5 minutes the gap distance is lowered 0.5 mm and excess sample is removed. Subsequently the following 1-step measurement is started:

[0196] Increasing angular frequency:

[0197] • Temperature: 190°C

[0198] • Angular frequency: going from 0.1 to 500 rad.s-1(logarithmic)

[0199] • Amplitude: 10 %

[0200] • Time setting: from 50 to 4 sec / data point

[0201] • 20 data points As a measure of the melt strength of polymers and composition as applied in the present invention, the tan 6 can be determined. From the storage (G’) and loss (G") dynamic moduli, obtained by applying the above angular frequency sweep analyses, the loss tangent (tan 5) may be obtained, where 5 is the phase (loss) angle, which is a measure of melt elasticity, is defined for each angular frequency as follows: tan 5 = G " / G ‘

[0202] Tan delta (tan 5) refers to a measure of how close a material is to a perfectly-elastic solid (where d = 0°, tan delta = 0) or of how close a material is to a perfectly-Newtonian liquid (where d = 90°, tan delta ~ infinity). The lower the tan 5 value, the higher the melt elasticity and melt strength. Tan delta is determined at 1 rad / sec and 190 °C.

[0203] Adhesion test

[0204] The adhesion strength of a coating composition on a coated substrate was evaluated on a scale of 0 to 5, with 5 being the best, using the below scores:

[0205] The following protocol was applied.

[0206] Samples of a coated substrate were cut out, and subjected to tear, and visually inspected by a tester. Per coated substrate, five samples were taken at different positions of the coated substrate. The samples were circular with a diameter of about 110 mm. A cross with a cutter was made in the middle of the circular sample at the side of the coating. A tester then subjected the sample to tear in order to separate the coating from the substrate by pulling from the middle of the cross. The amount of fibers that remain adhered to the coating after separation of the coating from the substrate were evaluated. The percentage of the fibers indicated in the above scoring table thus represents the number of fibers (of the substrate) remaining in the coating layer after separation of the coating layer from the substrate. All samples are cut and evaluated by the same tester in a same way. Five samples were evaluated for each coating composition obtained under the same process conditions. The resulting score is an average of these 5 measurements. This evaluation permits to evaluate the strength of the adhesion of the coating composition to the substrate. The higher the number of fibers, the better the adhesion strength.

[0207] Grammaqe (basis weight)

[0208] Grammage is the area density of a product, i.e. the mass per unit of area. It is expressed in g / m2, regardless of its thickness. The grammage of a substrate can be determined in accordance with ISO 536.

[0209] Thickness of a substrate

[0210] The thickness of a substrate, generally expressed in pm, can be determined in accordance with ISO 534.

[0211] Coating weight

[0212] The coating weight of a coated substrate refers to the amount of coating composition applied on a substrate. The amount of coating composition is expressed as weight per given area, in particular in g / m2.

[0213] In the present examples, the coating weight reported for coated substrates is the average of measurements performed on 5 samples of coated substrates. Per coated substrate, five samples were taken at different positions of the coated substrate while avoiding the edges of the coated substrate, where the coating may be less well distributed. Samples of a coated substrate were cut out in a same way as done in the adhesion test: the samples were circular with a diameter of about 110 mm. The samples were weighted on a precision scale. The weight of the substrate without coating composition was also determined and used as the reference value. Each weighing was performed by the same tester, using the same scale. To determine the coating weight, the reference value was subtracted from the total weight of the sample of the coated substrate sample. The coating weight corresponds to an average of the 5 sample measurements.

[0214] Neck-in

[0215] “Neck-in” (synonymous herein for “necking”) can be determined by considering the width of the substrate and the coating width obtained when coating the substrate. Neck-in was measured manually. Measurements were always done by the same person. For each coated substrate tested, a sample of about 10 meters was taken, and neck-in was measured at five different points along these 10 meters. An average of these five measurement points was determined, and neck- in was then calculated as the difference between the substrate width (In the below examples, substrate width used for the tests was 550 mm for all samples) and the average of the five coating width measuring points.

[0216] The following examples illustrate several embodiments of compositions according to the invention, and their usefulness in coating substrates via extrusion coating.

[0217] EXAMPLE 1 : PLA-BASED COMPOSITIONS

[0218] Certain properties of the PLA and PML resins as applied in the present example are summarized in the below Table 1 :

[0219] Table 1

[0220] Different examples of compositions according to the invention were prepared using the above resins, and are listed in Table 2. The coating compositions reported in Table 2 were prepared by blending the listed components, i.e. PLA, PML, and chain extending agent, at the indicated amounts, wherein the amounts are expressed in wt% based on the total weight of the resulting coating compositions. The compositions IE1 to IE5 were dried after preparation at 45°C for at least 6 hours. A comparative coating composition CE1 was also prepared and is reported in Table 2. This comparative composition contains PLA in combination with a chain extending agent. The comparative composition (CE1) was dried after preparation at 80 °C for 4 hours.

[0221] Table 2: Compositions according to the invention and comparative composition

[0222] EXAMPLE 2: EXTRUSION COATING

[0223] The present example illustrates extrusion coating experiments carried out on a paper-based substrate using various coating compositions according to the invention as compared to a comparative composition.

[0224] The extrusion coating system used in this example, comprises: a hopper for feeding a composition to an extruder; an extruder with screw diameter of 60 mm, L / D ratio of about 30; a die having a width of 700 mm; a pressure roll and a glossy chill roll; a surface treatment unit allowing to apply a flame treatment on the substrate before being coated, comprising a Hill Gmbh, type EF 75-1 burner, (Burner CE62-500), with a heat output of max. 50 kW, and propane gas supply.

[0225] In the extrusion coating experiments, cooling under the hopper was fixed at about 30°C.

[0226] The width of the coated substrates in the present experiments was 550 mm. The die width was adjusted to about 680 mm in order to have a coating in the 550 mm width of the substrate. The chill roll was operated at 20°C. The air gap (die height) was adjusted to 130 mm during the experiments. Pressing pressure used in the pressure roll during the experiments was set at about 5 to 6 bar.

[0227] In the present experiments, the substrate to be coated consisted of cartonboard having a thickness of 260 pm, and a grammage of 195 g / m2, available from Stora Enso (BE) under the tradename Performa Nature™. The same substrate was used for coating with the inventive coating compositions and the comparative coating composition.

[0228] In all experiments, using the inventive and comparative composition, the substrate was subjected prior to coating to a flame treatment in the presence of propane gas, at a power of about 50 kW for a suitable period of time in order to oxidize and heat up the surface of the substrate to a temperature of about 70-90 °C.

[0229] Extruder and die temperatures applied during the coating experiments are listed in Tables 3 and 4. Different extrusion line speeds, expressed in m / min and ranging from 60 to 240 m / min, were applied and coating performance was evaluated, in terms of adhesion of the inventive and comparative coating composition to the substrate, neck-in values and coating weight.

[0230] Table 3: Extruder temperatures used per coating composition (°C):

[0231] Table 4: Die temperatures used per coating composition (°C):

[0232] Further conditions as applied during the extrusion coating experiments are reported in Table 5, which shows the melt temperature during the extrusion as measured by the extruder system (sensor located inside the extruder) for each coating composition and extruder screw speed applied in the experiments.

[0233] Table 5

[0234] Coated substrates were obtained when coating with compositions IE1 to IE5, and CE1 to CE3 compositions, and the coated substrates were analyzed in terms of neck-in, coating weight and adhesion of the layer of the tested coating composition to the substrate, using the methodology as explained in the method section above.

[0235] It is noted that no coated substrates could be obtained with the coating composition consisting of polymeso-lactide (PML3) due to blockage of the extruder when using this composition. The addition to the PML3 resin of a chain extending agent (added as MB1) did not lead to a composition that could be extruded because of extruder blocking issues.

[0236] Neck-in

[0237] Results of neck-in when using different compositions at different coating line speeds are reported in Table 6.

[0238] The value that is underlined in Table 6, marks the maximum speed of the coating line at which extrusion coating could be performed in a stable manner, allowing to uniformly extrude the coating composition on the substrate. In contrast, extrusion coating is defined as unstable, when no uniform application of the coating composition can be done, for instance, when the coating is oscillating, which may lead to extreme neck-in and / or the presence of holes.

[0239] Table 6: Neck-in (in mm) nd = not determined

[0240] Coating weight

[0241] Table 7 reports coating weights determined for the substrates coated with various inventive and comparative coating composition, and when coated at different coating line speeds. The value that is underlined in Table 7, marks the maximum speed of the extrusion coating line at which extrusion coating could be performed in a stable manner, as discussed above, allowing to uniformly extrude the coating on the substrate.

[0242] Table 7: Coating weight (in g / m2) nd = not determined Adhesion

[0243] Table 8 reports adhesion of inventive and comparative coating composition to a substrate when coated at different extrusion coating line speeds. The value that is underlined in Table 8 marks the maximum coating line speed at which the extrusion coating could be performed, in a stable manner, as discussed above, allowing to uniformly extrude the coating on the substrate.

[0244] Table 8: Adhesion performance nd = not determined

[0245] Table 9 provides an overview of the results of adhesion and neck-in of coated substrates at a coating weight of about 25 g / m2or close to that weight, as obtained for the coated substrates obtained in example 2 when using inventive and comparative coating compositions. Also indicated in Table 9 is the coating line speed line at which such results were obtained. For instance, for CE1 , the results show that at a coating line speed of 60 m / min, a coating weight of 29.9 mm is found with an adhesion score of 2.

[0246] Table 9 Properties of coated substrates of similar coating weight Table 10 represents coating weight, adhesion, and neck-in properties as determined for coated substrates obtained in example 2 at their respective the maximum coating line speed providing a stable extrusion coating operation.

[0247] Table 10 Properties of coated substrates at maximum stable coating line speed

[0248] Tables 9 and 10 illustrate that substrates coated with a composition according to the invention can be obtained at higher stable line speeds, while such coated substrates still show good properties such as limited neck-in, good adhesion and coating weights that are similar and in some cases even better than those obtained for substrates coated with the comparative composition but at lower coating line speed. Table 10 shows that the coating weight obtained with compositions IE3 and IE5 at the indicated stable coating line conditions is relatively low (13, 11 , 16 g / m2), suggesting that it is possible to further increase the coating weight, and hence adhesion properties, under the reported stable operational conditions.

[0249] Results of the experiments shown in Tables 6 to 10 show that when using inventive compositions according to the invention, extrusion coating operational efficacy and stability can be improved, resulting in coated substrates with balanced properties. Particularly, using the inventive compositions results in an extrusion coating process showing good processability, and extrusion coated substrates are obtained showing good adhesion, at an affordable coating weight, and with limited neck-in. When comparing the results obtained for the inventive compositions with the comparative composition CE1 , it can be observed that the inventive compositions (IE1 to IE5) allow performing extrusion coating under stable and uniform conditions at a much higher speed of the coating line, and at the same time maintaining good results on neck-in and adhesion to the coated substrates. For CE1 adhesion was very poor when running at higher speeds (see Table 8).

Claims

CLAIMS1. Composition comprising: a) polymeso-lactide (PML) having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 85.0 g / 10 min, and a stereochemical purity of at least 35.0 % D-lactate, b) poly-L-lactide (PLA) having a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 40.0 g / 10 min, and a stereochemical purity of at least 85.0 % L-lactate; and c) at least one chain extending agent, wherein the sum of a) PML and b) PLA in said composition is more than 50.0 wt%, based on the total weight of the composition.

2. Composition according to claim 1 , wherein the sum of a) PML and b) PLA in said composition is at least 55.0 wt%, preferably at least 60.0 wt%, preferably at least 70.0 wt%, based on the total weight of the composition3. Composition according to claim 1 or 2, wherein the weight ratio of PML:PLA is equal to or higher than 1 :1 , preferably at least 1.5:1 , or at least 2:1 , or at least 2.5:1 , or at least 3:1.

4. Composition according to any one of claims 1 to 3, wherein said composition comprises PML in an amount of between 15.0 and 85.0 wt%, preferably between 30.0 and 80.0 wt%, preferably between 45.0 and 80.0 wt%, preferably between 55.0 and 75.0 wt%, with wt% based on the total weight of the composition.

5. Composition according to any one of claims 1 to 4, wherein said composition comprises PLA in an amount of between 10.0 and 80.0 wt%, preferably 20.0 and 50.0 wt%, preferably between 22.5 and 45.0 wt%, preferably between 25.0 and 35.0 wt%, with wt% based on the total weight of the composition.

6. Composition according to any one of claims 1 to 5, wherein said composition comprises said chain extending agent in a total amount of at most 3.0 wt%, with wt% based on the total weight of the composition.

7. Composition according to any one of claims 1 to 6, wherein said chain extending agent is selected from the group consisting of an epoxide-functionalized chain extending agent, a peroxide-functionalized chain extending agent, an anhydride-functionalized chain extending agent, an isocyanate-functionalized chain extending agent, an oxazoline chain extendingagent and oxazine chain extending agent, a vinyl-acetate-based polymer, and any combinations thereof, preferably an epoxide-functionalized chain extending agent; and more preferably the chain extending agent is an epoxy functional styrene-acrylate copolymer.

8. Composition according to any one of claims 1 to 7, wherein said PML has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.5 and 80.0 g / 10 min, such as between 3.0 and 80.0 g / 10 min, or between 10.0 and 80.0 g / 10 min, or between 30.0 and 80.0 g / 10 min, or between 50.0 and 75.0 g / 10 min, or between 50.0 and 65.0 g / 10 min.

9. Composition according to any one of claims 1 to 8, wherein said PLA has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of between 2.0 and 25.0 g / 10 min, or between 2.0 and 15.0 g / 10 min, or between 2.0 and 10.0 g / 10 min.

10. Composition according to any one of claims 1 to 9, wherein said PML has a zero shear viscosity (etaO) measured at 190°C, 0.1 rad / s, lower than 3800 Pa.S, such as lower than 1800 Pa.s, or lower than 1500 Pa.s, or lower than 500 Pa.s.

11. Composition according to any one of claims 1 to 10, wherein said composition has a zero shear viscosity (etaO) measured at 190°C, 0.1 rad / s, lower than 3500 Pa.s.

12. Composition according to any one of claims 1 to 11 , wherein said composition has a melt flow index (MFI), as determined at a temperature of 190 °C and a test weight of 2.16 kg, of at least 5.0 g / 10 min, or at least 10.0 g / 10 min.

13. Composition, according to any one of claims 1 to 12, wherein said composition is prepared by by separately blending said PML, said PLA, and said chain extender agent.

14. A coated substrate comprising at least one layer of a composition according to any one of the claims 1 to 13, that is coated on at least one surface of said substrate.

15. The coated substrate according to claim 14, wherein said substrate is selected from a metal, a textile, a composite material, a substrate based on (ligno)cellulosic materials, and preferably is a substrate selected from the group comprising paper, paperboard, cartonboard, wood, fiberboard, textile material, and material based on paperpulp.

16. Process for preparing a coated substrate comprising the step of coating of a composition according to any one of claims 1 to 13 onto at least one surface of a substrate, preferably as defined in claim 15, to form a coated substrate, preferably by means of extrusion coating.

17. An article comprisinga composition according to any one of claims 1 to 13, and / or a coated substrate according to any one of claims 14 to 15, preferably wherein said article is a container, bottle, cup, packaging material, film, sheet, foamed material, bag, wrapping material.

18. Use of a composition according to any one of claims 1 to 13- for coating a substrate, preferably by extrusion coating, or,- for producing a film or sheet, or- for producing at least one layer in a multilayer film.

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