Packaging material

Abstract

A multi-layer packaging material comprising - a polymeric substrate comprising or consisting of a polymeric component selected from the group consisting of a polyhydroxyalkanoate polymer or copolymer, polybutylene succinate or its copolymers, polylactic acid, polybutylene adipate terephthalate and mixtures thereof, and - a barrier coating layer on one or both sides of the substrate comprising: from 51 to 99 % wt, preferably 90 - 99 % wt, more preferably 95 - 98 % wt. of a polymeric component selected from the group consisting of a polyhydroxyalkanoate polymer or copolymer, proteins from milk or legumes, polylactic acid, polybutylene succinate or its copolymers, starch, chitosan, carrageenan, pectin, alginates, lipids, polyacrylic polymers, polyurethane, cellulose or chemically modified cellulose and mixtures thereof, and from 49 to 1 % wt, preferably 1-10 % wt, more preferably 2-5 % wt. of a filler selected from the group consisting of a layered double hydroxide, nanocellulose, silicates, clay and mixtures thereof, the percentages by weight being referred to 100 parts by weight of the polymeric component and the filler.

Description

[0001] Packaging Material

[0002] The present invention relates to a multi-layer packaging material, particularly for use in packaging confectionary products, comprising a polymeric substrate and at least a barrier layer.

[0003] Barrier coatings are required and widely used in food packaging to preserve the food organoleptic properties. Barrier properties for packaging materials, particularly for a confectionary product, include a low permeability to 02 and water vapor, as well as low permeability to volatile aroma compounds and low light permeability. Particularly, for packaging materials for use in the packaging of confectionary products it is desirable to achieve an oxygen transmission rate (OTR) lower than 100 or preferably lower than 0.1 cc / m224h, measured at 23 °C at 0% RH and a water vapor transmission rate (WVTR) lower than 10 or preferably lower than 0.1 g / m2 24 h at 38 °C at 90% RH.

[0004] There is a need for packaging materials that are eco-sustainable, allowing the packagings to be compostable and easily recyclable in multiple environments. An object of the invention is to provide multilayer packaging with multiple materials that will still maintain the biodegradation and compostability properties while ensuring high level of protection that, as of today, biobased and biodegradable materials are lacking. This goal is reached by adding all natural additives / materials to make sure that in the biodegradation process no harming substances are going to be left behind in the soil or compost.

[0005] Moreover, there is a need for packaging materials that combine the required barrier properties and the eco-sustainability properties, with mechanical properties that allow their use in modem high-speed packaging machines such as for instance flow-pack and flow-wrap machines and twist-wrap machines. Particularly desirable as mechanical properties are tensile strength and resistance to pierce.

[0006] The purpose of the invention is to provide a multi-layer packaging material that combines the above-mentioned requirements. Summary of the invention

[0007] In view of the above-mentioned purpose, the subject-matter of the invention is a multi-layer packaging material as defined in the appended claims.

[0008] The dependent claims relate to preferred embodiments of the invention.

[0009] Further characteristics and advantages of the packaging material of the invention will become clear from the detailed description that follows, made with reference to the attached drawings, provided by way of non-limiting example.

[0010] Brief description of the drawings

[0011] In the attached drawings:

[0012] - Fig. 1 is a schematic sectional representation showing the layers layout of a plurality of embodiments (a) through (f) of the packaging material wherein a surface layer of the multi-layer structure has heat sealing properties;

[0013] - Fig. 2 is a schematic sectional representation showing the layers layout of embodiments of the invention (a) though (c) wherein the multi-layer structure includes a surface layer having cold sealing properties,

[0014] - Fig. 3 to 8 show preferred examples of composite coextruded substrates and

[0015] - Fig. 9 and 10 show further exemplified embodiments.

[0016] In the annexed drawings, the reference numerals indicate the following structural features:

[0017] I polymeric substrate (single layer film or sheet or coextruded composite film or sheet);

[0018] 3 core layer of a coextruded composite film or sheet;

[0019] 5 skin layer(s) of a coextruded composite film or sheet;

[0020] 7 barrier layer;

[0021] 9 optional layer obtained by applying a heat sealable laquer;

[0022] I I optional continuous or discontinuous cold sealable layer:

[0023] 13 optional continuous or discontinuous printed layer;

[0024] 15 optional layer obtained from a release varnish.

[0025] Detailed description of the invention The invention relates to packaging materials having a multi-layer structure and comprising a substrate 1, which is a film or sheet of a (bio) degradable polymer or of a blend of (bio)degradable polymers.

[0026] The (bio) degradable polymers are selected from the group consisting of a polyhydroxyalkanoate or a polyhydroxyalkanoate copolymer, polybutylene succinate or its copolymers, polylactic acid, polybutylene adipate terephthalate and mixtures thereof.

[0027] The reference to a sheet includes thermoformed or thermoformable sheets.

[0028] Polyhydroxyalkanoates (PHAs) for use as the substrate 1 preferably include medium chain length PHAs with 6-14 carbon atoms in their monomer units, that are soft and elastomeric with low melting points, typically from 50 to 170°, preferably from 100 to 160°; however, the term PHAs also includes short chain length and long chain length PHAs and / or mixtures thereof.

[0029] Examples of poly (hydroxyalkanoate) polyesters that can be used within the scope of the invention include, but are not limited to, poly (3 -hydroxybutyrate) (3HB), poly (4- hydroxybutyrate) (4HB), poly (3- hydroxyvalerate)(3HV); particularly preferred are copolymers of hydroxybutyrate and hydroxyvalerate or hydroxyhexanoate which have a melting temperature of 120 to 1600C including, poly (3-hydroxybutyrate-co-3- hydroxyvalerate)(PHBV), poly (hydroxybutyrate-co-hydroxyhexanoate) (PHBH), poly (3 - hydroxy-co-4-hydroxybutyrate)and their copolymers. PHBH and PHBV are preferred.

[0030] Also included are PHAs blends including a PHA, preferably poly(3-hydroxybutyrate-co-4- hydrobutyrate) and biodegradable polymers selected from cellulose, starch or starch acetate, poly (lactic acid), polycaprolactone.

[0031] Polybutylene succinate (PBS) copolymers include: poly(l,4-butylene succinate-co-adipate), poly(l,4-butylene succinate-co-l,4-butylene azelate), poly(l,4-butylene succinate-co-l,4-butylene terephthalate), poly(l,4-butylene succinate-co-l,4-butylene sebacate-co-l,4-butylene terephthalate), poly(l,4-butylene adipate-co-l,4-butylene succinate-co-1,4- butylene terephthalate), poly(l,4-butylene azelate-co-l,4-butylene succinate-co-l,4-butylene terephthalate). Also included are polyhydroxyalkanoate-polybutylene succinate copolymers.

[0032] The reference to a film or sheet of a (bio)degradable polymer does not exclude the presence within the film or sheet of additives that are conventionally included in commercial films or sheets, such as plasticizers, antioxidants and fillers.

[0033] Particularly, but optionally, the substrate 1 may comprise particulate fillers that improve the barrier properties, such as layered double hydroxides (LDH), particularly hydrotalcite or hudrotalcite-like minerals, clay, nanocellulose and mixtures thereof. Such fillers, if included in the substrate, are dispersed in the polymer matrix, typically in the amount of from 0.5 to 10 % wt. referred to the polymer matrix.

[0034] In one embodiment, the polymeric component of the substrate consists of a polyhydroxyalkanoate polymer or copolymer, of polybutylene succinate or of a blend of a poly hydroxy alkanoate and polybutylene succinate. Said blend preferably contains:

[0035] - from 50 to 70 % wt. of a polyhydroxyalkanoate and from 30 to 50 % wt. of polybutylene succinate with reference to 100 parts by weight of the polymeric component, and wherein, preferably, said substrate further comprises up to 10% wt. of a filler, referred to 100 parts by weight of the polymeric component, selected from the group consisting of a layered double hydroxide (LDH), particularly hydrotalcite or hydrotalcite-like minerals, clay, nanocellulose, starch and mixtures thereof.

[0036] In one embodiment the substrate 1 is a coextruded composite film or sheet comprising a core layer 3 and a skin layer 5 thinner than the core layer on one or, preferably on both sides of the core layer; in this embodiment the core layer is preferably a polymeric film or sheet of a polyhydroxyalkanoate polymer or copolymer, preferably PHBH or PHBV or of polybutylene succinate and mixtures thereof.

[0037] The core layer of the coextruded film or sheet or the substrate as a single layer film, can be a blend of a PHA with up to 40 % wt. referred to the PHA, of poly (lactic acid), to enhance the twist hold characteristics of the substrate. Blends of PHBH and PBS may be used to enhance the stretchability of PHBH films.

[0038] In the embodiment of a coextruded composite film, preferably the core layer 3 comprises a filler dispersed in the polymer matrix, selected from layered double hydroxides, particularly hydrotalcite or hydrotalcite-like minerals, preferably in the amount of from 0.5 to 10 % wt referred to the polymer matrix, and cellulose nanocrystals, preferably in the amount of from 0.5 to 3 % wt. , referred to the polymer matrix; the skin layers are a co-extruded coating comprising or consisting essentially of a polymeric component selected from a polyhydroxyalkanoate polymer or copolymer, polybutylene succinate ant its copolymers and mixtures thereof. The skin layer(s) prevents or limits any potential migration of additives from the core layer. The polymer for the skin layer(s)may be the same or different from the polymer of the core layer.

[0039] Said coextruded composite films or sheets are intermediate products, adapted to further processed to be coated with a barrier layer or other layers, as herein described, that fall within the scope of the invention.

[0040] Figures 3 to 8 show non limiting examples of coextruded composite substrates for use according to the invention.

[0041] Depending on the choice of the melting temperature of the adopted polymer, the substrate may be heat sealable.

[0042] The packaging material of the invention also comprises a barrier layer 7 on one or both sides of the substrate.

[0043] The term barrier layer, as used herein, indicates a structural layer that provides a barrier to water vapor, oxygen, aroma or carbon dioxide; it may further provide grease or moisture resistance and / or water absorption resistance. It was found that said barrier layer, as herein described, with reference to the substrates adopted for the invention, also enhances the material mechanical properties (e.g. tensile, tear, impact or burst strength). In some embodiments, the disclosed barrier layer also provides a packaging material with the ability to maintain deformation upon twisting, cold forming properties and thermoforming, while keeping the original material properties of the substrate.

[0044] In some embodiments, the barrier layer is heat sealable owing to the adoption of a low sealing temperature polymer / blend (PHA, PBS, milk proteins, legumes proteins, carrageenan).

[0045] A barrier layer with heat sealing properties (such as shown in fig. 1 (b) and (d)) is adopted or required, if the barrier layer is an external layer and no cold sealing or heat- sealing layer (shown e.g. in fig 1(c), fig. 2(a), (b) and (c) is applied.

[0046] The barrier layer 7 may be extrusion coated or laminated or applied as a dispersion or solution in water or in an organic solvent and dried onto the substrate layer.

[0047] Said barrier layer applied on one or both sides of the substrate, preferably comprises: from 51 to 99 % wt., preferably 90-99 % wt., more preferably 95 - 98 % wt. of a polymeric component selected from the group consisting of a polyhydroxyalkanoate polymer or copolymer, proteins from milk or from vegetables such as legumes, polylactic acid, polybutylene succinate or its copolymers, starch, chitosan, carrageenan, pectin, alginates, lipids, polyacrylic polymers, polyurethane, cellulose or chemically modified cellulose and mixtures thereof, and from 49 to 1 % wt., preferably 1-10 % wt., more preferably 2-5 % wt. of a filler selected from the group consisting of a layered double hydroxide, particularly hydrotalcite or hydrotalcite-like minerals, nanocellulose, silicates, clay and mixtures thereof, the percentage by weight being referred to 100 parts by weight of the polymeric component and the filler and sum up to 100%.

[0048] In another embodiment, the barrier coating layer may be obtained by applying and drying a lacquer comprising one or a blend of the mentioned polymers and the previously disclosed filler or fillers in water or in an organic solvent vehicle. A suitable water dispersion typically includes a solid content (polymer(s) and filler(s) from 5 to 70 % wt., preferably 20-60 % wt.; suitable organic solvents include ethanol or ethyl acetate with a solid content (polymer(s) and filler(s)) of 5-70 % wt, preferably 20-60 % wt.

[0049] In one embodiment, said barrier layer, obtained from a lacquer, may be on both sides of the substrate (fig. 1 (d)).

[0050] In another embodiment, the multi-layer structure may comprise a barrier coating layer which is extrusion coated or laminated onto the substrate and a barrier layer which is heat sealable obtained from a lacquer on the other side of the substrate (fig.1 (d)).

[0051] In another embodiment, the multi-layer structure may comprise said barrier coating layer, obtained from a lacquer, as described above, above a barrier layer which is extrusion coated or laminated onto the substrate layer or, if said barrier layer is extrusion coated or laminated onto both sides of the substrate, said barrier coating layer, obtained from a lacquer, may be placed on both extrusion coated or laminated layers.

[0052] If the barrier layer is not heat sealable, a heat sealable layer 9 obtained from a heat sealable lacquer may be applied as an external layer (fig 1 (c)); the polymers for the heat sealable lacquer are the same low melting polymers disclosed for the barrier layer, but this layer 9 does not include a filler.

[0053] The polyhydroxyalkanoates (PHAs)for use in the barrier layer(s), may be the same as previously disclosed for the substrate.

[0054] Polybutylene succinate (PBS) copolymers for use in the barrier layer(s), may be the same as previously disclosed for the substrate.

[0055] Vegetable proteins include proteins from legumes, such as pea and lentil, or proteins from fungi.

[0056] Also included as suitable polymeric components for the barrier layer are polylactic acid, thermoplastic blends of starch and aliphatic polyesters, chitosan, carrageenan and pectin. The fillers for use in the barrier layers of the invention are selected from layered double hydroxides (LDH), nanocellulose, natural or synthetic phyllosilicates and mixtures thereof. Preferred LDH include hydrotalcite and hydrotalcite-like minerals.

[0057] Preferred nanocellulose materials include cellulose nanofibers (CNF), nanocrystalline cellulose (CNC) or bacterial nanocellulose (BNC); the term nanocellulose also includes nanocellulose modified in the CH2OH groups, for example by esterification or amidation or etherification.

[0058] Preferred phyllosilicates include montmorillonite bentonite, hectorite, smectite and mica.

[0059] The adopted fillers typically have a particle size with the following features:

[0060] One dimension: 1-40 micron

[0061] Other dimension: 1 nm - 2 micron, aspect ratio: 1.20 - 20,000.

[0062] The barrier layers are normally applied in a weight range of from 0.5 to 10 g / m2, preferably 1-5 g / m2, more preferably 1-3 g / m2.

[0063] In a preferred embodiment of the invention, the laminated or extrusion coated barrier layer is heat-sealable, in which case the polymeric component is preferably a polyhydroxyalkanoate (as previously described), polybutylene succinate, polybutylene adipate terephthalate and polylactic acid, in combination with a filler which is preferably selected from a layered double hydroxide and nanocellulose.

[0064] In a further embodiment which allows to obtain a heat-sealable barrier layer which is a surface layer of the multi-layer-material, the polymeric component is selected from the group consisting of proteinaceous materials, preferably selected from milk, fungal and pea proteins, as well as gelatin.

[0065] The multilayer packaging material may further include one or more primer layers (not shown in the drawings) that are applied to one or both sides of the substrate layer, in between the surface of the substrate layer and said barrier coating layers; primer layers may be used to improve the spreading or adhesion of the subsequent coating.

[0066] Primers for the purpose of the present invention may be selected from the group consisting of acrylic acid copolymers, polyesters, polyhydroxyalkanoates, native and chemically modified starches, xylan and chemically modified xylan, polyvinylidene dichloride, polyvinyl alcohol, ethyl-vinyl alcohol, vinyl acetate, ethyl-vinyl acetates, cellulose nitrate, silanes, polyurethanes, or combinations thereof.

[0067] In case the multilayer packaging material of the invention does not include a surface layer which is heat-sealable, a cold sealable layer 11 (fig 2 (a), (b) and (c) may be applied as a surface coating, optionally in limited areas of the packaging material.

[0068] Cold sealable layers 11 are normally formulated from a latex or non-allergenic latex suspension; water-based acrylic or synthetic latex systems could alternatively be used. Cold sealable layers may include additives or pigments (e.g. 0.1-5% by weight relative to the resin).

[0069] Typically, the multi-layer structure includes a surface printed layer 13 that is applied using conventional printing inks as well as natural inks and conventional printing techniques, such as offset printing or rotogravure.

[0070] The printed layer may be further coated with a protective varnish; protective varnishes are applied to protect inks or coatings from damage during the lifetime of the packaging. Damage could occur from moisture or solvent attack or by mechanical stress or abrasion. A protective varnish is applied by the same technology used to apply the printing ink.

[0071] Typically, protective varnishes comprise a resin, additives / stabilizers / modifiers and solvent. Suitable solvents may be water, ethanol, ethyl acetate. Resins can be selected from nitro- or other modified cellulose, acrylic polymers and polyurethane.

[0072] Particularly in those embodiments, wherein the multi-layer structure includes a cold sealable surface layer 11, a release coating layer 15 may be applied to cover the printed layer, on the side of the multi-layer structure opposite to the cold sealable layer, to provide release properties.

[0073] Release varnishes are applied to facilitate the unwinding of the printing reels and to prevent cold seal from adhering to other parts of the packaging structure. The release varnishes to be considered have the same constituents as a protective varnish but include an additional slip or release agent. Slip or release agents can be selected from silicone-containing compounds, fatty acids or fatty acid esters, vegetable or other plant-based oils, carnauba or other biobased waxes and paraffin waxes.

[0074] A preferred embodiment of the invention includes multi-layer packaging materials wherein the barrier layer is heat-sealable and comprises:

[0075] - from 50 to 70 % wt. of a PHA having a melting temperature of from 60 to 170 °C,

[0076] - from 20 to 40 % wt. of PBS, and

[0077] - from 0.5 to 3 % wt. of nanocellulose (preferably CNC) and up to 9.5 % wt. of additives and / or filler, selected from those which are previously mentioned, other that nanocellulose, wherein the sum of the wt. percentages is 100%; or:

[0078] 90% wt. PHA, preferably PHBH;

[0079] 0.5 -3% wt. dispersed CNC

[0080] 7 - 9.5 % wt. additives / fillers other than CNC, wherein the % amounts sum up to 100 %.

[0081] Or:

[0082] 90% wt PHA, preferably PHBH;

[0083] 0.5 -3% wt. dispersed LDH, preferably hydrotalcite

[0084] 7 - 9.5 % wt. additives / fillers other than LDH, wherein the % amounts sum up to 100 %.

[0085] In a further preferred embodiment, wherein the barrier layer is heat-sealable and is laminated or extrusion coated, said barrier layer comprises:

[0086] - from 50 to 60 % wt. of a PHA, with a melting temperature of from 60 to 170 °C, - from 20 to 30 % wt. of PBS,

[0087] - from 0.5 to 10 % wt. of a dispersed layered double hydroxide, and

[0088] - from 5 to 9.5 % wt. of additives / fillers (other than LDH), the sum of said percentages being 100% wt.

[0089] Examples 1-6 relate to embodiments of composite coextruded substrates that can be used to provide the packaging materials of the invention as flexible films or as thermoformable sheets.

[0090] In examples 1-6, the core layer and the skin layers for use to provide flexible films, preferably have (altogether) a thickness of from 12 to 45 micron, preferably about 20 micron, and for use to provide thermoformable sheets have generally a thickness of from 500 to 1500 micron.

[0091] Example 1 (figure 3)

[0092] Core layer 3: PHA, preferably PHBH, including 0.5- 10% wt. clay, preferably hydrotalcite dispersed in the polymer matrix.

[0093] Skin layers 5: both PBS

[0094] Example 2 (figure 4)

[0095] Core layer 3: PBS, including 0.5- 10% wt. clay, preferably hydrotalcite dispersed in the polymer matrix.

[0096] Skin layers 5: both PHA, preferably PHBH

[0097] Example 3 (figure 5)

[0098] Core layer 3: PHA, preferably PHBH, including 0.5 - 3% wt. nanocellulose (preferably CNC) dispersed in the polymer matrix.

[0099] Skin layers 5: both PBS Example 4 (figure 6)

[0100] Core layer 3: PHA, preferably PHBH, including 0.5 - 3% wt. nanocellulose (preferably CNC) dispersed in the polymer matrix.

[0101] Skin layers 5: both PHA, preferably PHBH.

[0102] Example 5 (figure 7)

[0103] Core layer 3: PBS, including 0.5 - 3 % wt. nanocellulose (preferably CNC) dispersed in the polymer matrix.

[0104] Skin layers 5: both PHA, preferably PHBV.

[0105] Example 6 (figure 8)

[0106] Core layer 3: PBS, including 0.5 - 3 % wt. nanocellulose (preferably CNC) dispersed in the polymer matrix.

[0107] Skin layers 5: both PBS.

[0108] The composite coextruded substrates shown in Examples 1 - 6 may be used according to the layouts of figures 1 and 2.

[0109] Examples 9-11 relate to preferred embodiments of flexible films, particularly for flow pack and pouches packaging applications:

[0110] Example 9

[0111] A multi-layer flexible film having a structure comprising or consisting of the following layers:

[0112] - external printed layer: preferably with a weight of 1 gsm;

[0113] - coextruded composite layer according to Example 5 (fig. 7) or according to Example 3 (fig. 5), thickness: 20 micron;

[0114] - (extrusion coated or laminated) barrier layer, (weight: about 10 gsm) comprising: - from 50 to 60 % wt. of a heat sealable PHA, with a melting temperature of from 60 to 170 °C,

[0115] - from 20 to 30 % wt. of PBS,

[0116] - from 0.5 to 10 % wt. of a dispersed layered double hydroxide, and from 5 to 9.5 % wt. of conventional additives, the sum of said percentages being 100 % wt.

[0117] Oxygen barrier from about 300 to about 0.5 cc / m2 24h, measured at 23 °C at 40-50 RH.

[0118] A clay based or metal oxide additional layer may be added to further improve the moisture barrier to values below 20 g / m2 24 h at 38 °C at 90% RH.

[0119] Example 10

[0120] A multi-layer flexible film having a structure comprising or consisting of the following layers:

[0121] - external printed layer: preferably with a weight of about 1 gsm;

[0122] - coextruded composite layer according to Example 5 (fig. 7) or according to Example 3 (fig. 5), thickness :20 to 40 micron, preferably 20 micron;

[0123] - (extrusion coated or laminated) barrier layer with a weight of about 10 gsm, comprising:

[0124] - from 50 to 60 % wt. of a heat sealable PHA, with a melting temperature of from 60 to 170 °C,

[0125] - from 20 to 30 % wt. of PBS,

[0126] - from 0.5 to 10 % wt. of a dispersed layered double hydroxide, and from 5 to 9.5 % wt. of conventional additives, the sum of said percentages being 100 % wt.; wherein the barrier layer is coated with a PBS film (thickness 15 micron) useful to avoid or to reduce delamination of the barrier layer.

[0127] Example 11

[0128] A multi-layer flexible film having the structure shown in fig. 9.

[0129] A barrier layer consisting of a PHA (thickness: 3-8 micron, weight: about 10 gsm) and including nanocellulose (preferably CNC 0.5 - 3% wt.) or hydrotalcite (0.5- 10% wt. is sandwiched between two PHA films (12 micron and 20 micron). The PHA on the side opposite the printed layer is selected so as to have heat sealable properties.

[0130] Examples 12 and 13 relate to preferred embodiments of thermoformable sheets:

[0131] Example 12

[0132] An extrusion coated or laminated barrier layer of proteinaceous material (Proteins from Milk) including nanocellulose (preferably CNC 0.5 - 3% wt.) or hydrotalcite (0.5- 10% wt.) with a thickness of 10 micron is sandwiched between two PHA sheets or coextruded composite layers with a thickness of 250- 500 micron.

[0133] Example 13

[0134] An extrusion coated or laminated barrier layer of proteinaceous material (Proteins from Milk) including nanocellulose (preferably CNC, 0.5 - 3% wt.) or hydrotalcite (0.5- 10% wt.) with a thickness of 10 micron is sandwiched between a PBS film (15 micron) and a composite coextruded sheet with a thickness of from 500 to 1500 micron having a structure according to anyone of examples 1 to 6. (cf fig.10)

[0135] It is understood that the multi-layer structure of the packaging material may include additional layers, such as:

[0136] A wax coating layer (e.g. a 5 - 15 gsm wax layer obtained from a wax -based dispersion in water) providing a moisture barrier;

[0137] A hydrotalcite layer (e.g. 4 - 5 gsm layer of, preferably, substantially pure hydrotalcite, obtained from a water dispersion of 30 - 60% wt hydrotalcite, providing barrier properties and an enhancement of mechanical properties,

[0138] A nanocellulose (preferably CNC) layer (e.g. 1-5 gsm layer of, preferably, substantially pure CNC obtained from a water dispersion at 20-40 % wt. solid content, providing 02 barrier properties and an enhancement of the mechanical properties.

Claims

CLAIMS1. A multi-layer packaging material comprising- a polymeric substrate comprising or consisting of a polymeric component selected from the group consisting of a polyhydroxyalkanoate polymer or copolymer, polybutylene succinate or its copolymers, polylactic acid, polybutylene adipate terephthalate and mixtures thereof, and- a barrier coating layer on one or both sides of the substrate comprising: from 51 to 99 % wt., preferably 90 - 99 % wt., more preferably 95 - 98 % wt. of a polymeric component selected from the group consisting of a polyhydroxyalkanoate polymer or copolymer, proteins from milk or legumes, polylactic acid, polybutylene succinate or its copolymers, starch, chitosan, carrageenan, pectin, alginates, lipids, polyacrylic polymers, polyurethane, cellulose or chemically modified cellulose and mixtures thereof, and from 49 to 1 % wt., preferably 1-10 % wt., more preferably 2-5 % wt. of a filler selected from the group consisting of a layered double hydroxide, nanocellulose, silicates, clay and mixtures thereof, the percentages by weight being referred to 100 parts by weight of the polymeric component and the filler.

2. The multi-layer packaging material of claim 1 wherein said polyhydroxyalkanoates (PHAs)for the substrate or for the barrier layer include medium chain length PHAs with 6- 14 carbon atoms in their monomer units, with melting points, typically from 50 to 170°, preferably from 100 to 160°.

3. The multi-layer packaging material of claim 1 or 2, wherein said polyhydroxyalkanoate of the substrate or of the barrier coating is selected from the group consisting of poly (3-hydroxybutyrate) (3HB), poly (4-hydroxybutyrate) (4HB), poly (3- hydroxyvalerate)(3HV), poly (3-hydroxybutyrate-co-3-hydroxyvalerate), poly (hydroxybutyrate-co-hydroxy hexanoate), poly (3 -hydroxy-co-4-hydroxybutyrate), their copolymers and mixtures thereof.

4. The packaging material according to claims 1, 2 or 3, wherein in said substrate, the polymeric component consists of a polyhydroxyalkanoate polymer or copolymer, ofpolybutylene succinate or of a blend of a polyhydroxyalkanoate and polybutylene succinate, wherein said blend contains:- from 50 to 70 % wt. of a polyhydroxyalkanoate and from 30 to 50 % wt. of polybutylene succinate with reference to 100 parts by weight of the polymeric component, and wherein said substrate further comprises up to 10 % wt. of a filler, referred to 100 parts by weight of the polymeric component, selected from the group consisting of a layered double hydroxide (LDH), clay, nanocellulose, starch and mixtures thereof.

5. The packaging material according to claim 4, wherein said substrate further comprises from 0.5 to 3 % wt. of cellulose nanocrystals (CNC), referred to 100 % wt. of the polymeric component.

6. The packaging material according to claim 4, wherein said substrate comprises from 0.5 to 10% wt of a dispersed layered double hydroxide (LDH) and from 7 to 9.5 % wt. of said fillers other than LDH, both referred to 100 parts by weight of the polymeric component.

7. The packaging material of any of claims 1 to 6, wherein the substrate is a composite coextruded film or sheet comprising a core layer and a skin layer thinner than the core layer on one or both sides of the core layer, wherein said core layer is a polymeric film of a polyhydroxyalkanoate or polybutylene succinate and mixtures thereof comprising a filler dispersed in the polymer matrix, selected from a layered double hydroxide, preferably in the amount of from 0.5 to 10 % wt. referred to the polymer matrix, and cellulose nanocrystals, preferably in the amount of from 0.5 to 3 % wt. , referred to the polymer matrix and said skin layer is a co-extruded coating consisting of a polymeric component selected from a polyhydroxyalkanoate, polybutylene succinate and mixtures thereof.

8. The packaging material according to any of claims 1 to 7, wherein said barrier coating is a heat- sealable layer of the packaging material and the polymeric component of said barrier coating consists of a polymer selected from the group consisting of a polyhydroxyalkanoate, polybutylene succinate, milk proteins, vegetable proteins, carrageenan or mixtures thereof having a heat-sealing temperature from 60 to 170°C.

9. The packaging material according to any of claims 1 to 8 wherein said barrier layer is a heat-sealable surface layer of the packaging material and the polymeric component of said barrier layer is a polyhydroxyalkanoate or a blend of polyhydroxyalkanoates having a heat-sealing temperature between 60 and 170C.

10. The packaging material of claim 1, wherein said barrier layer is obtained by applying and drying a lacquer comprising said polymeric component and filler in water or in a solvent vehicle.

11. The packaging material according to any of claims 1 to 7, further comprising a heat- sealable surface layer obtained from a lacquer comprising a heat sealable polymeric component and not including filler.

12. The packaging material according to any of claims 1 to 11, further comprising a surface protective coating on the side opposite the barrier layer with respect to the core, obtained from a varnish comprising a liquid vehicle selected from water, ethanol, ethyl acetate and polymer selected from nitrocellulose or chemically modified cellulose, polyacrylic polymers and polyurethane.

13. The packaging material according to any of the preceding claims further comprising a surface release coating comprising a slip or a release agent selected from the group consisting of silicone containing compounds, fatty acid or fatty acid esters, vegetable oils, carnauba wax and paraffin wax.

14. The packaging material according to any of the preceding claims further comprising a primer layer applied to one or both sides of the substrate in between the surface of the substrate layer and said barrier coating layer.

15. The packaging material according to any of the preceding claims, further comprising an ink printed layer.

16. The packaging material according to claim 1 comprising, as a surface layer, a coldsealable layer formulated from a latex suspension, optionally including additives or pigments.

17. A composite coextruded film or sheet comprising a core layer and a skin layer thinner than the core layer on one or both sides of the core layer, wherein said core layer is a polymeric film of a polyhydroxyalkanoate or polybutylene succinate and mixtures thereof comprising a filler dispersed in the polymer matrix, selected from a layered double hydroxide, preferably in the amount of from 0.5 to 10 % wt. referred to the polymer matrix, and cellulose nanocrystals, preferably in the amount of from 0.5 to 3 % wt. , referred to the polymer matrix and said skin layer is a co-extruded coating consisting of a polymeric component selected from a polyhydroxyalkanoate, polybutylene succinate and mixtures thereof.

18. The composite coextruded sheet of claim 17 which is thermoformable and has a thickness of from 500 to 1500 micron.

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