Multi-layer metallized paper-based packaging material

Abstract

The present invention relates to a cellulose substrate comprising or consisting of a cellulose graft copolymer comprising a polypeptide branch. The invention also relates to a packaging material, in particular a multilayer metallized paper-based packaging material, comprising at least one paper layer comprising or consisting of a cellulose graft copolymer comprising polypeptide branches.

Description

Technical Field

[0001] The present invention relates to a multi-layer paper-based packaging material, which includes a paper layer and an ultra-thin metal or quasi-metal layer for water vapor barrier, and the ultra-thin metal or quasi-metal layer is sandwiched between ultra-thin coatings, and these ultra-thin coatings provide oxygen barrier and sealing properties for the structure. More precisely, the present invention relates to a multi-layer paper-based packaging material, wherein the paper layer contains a cellulose graft copolymer containing polypeptide side chains. Background Art

[0002] Plastic packaging is frequently used in the economy and people's daily lives. It has multiple advantages, such as its flexibility and its light weight. For example, such weight reduction helps to save fuel and reduce CO2 during transportation. Its barrier properties contribute to reducing food waste due to their positive effect on extending the shelf life. The barrier properties also help to ensure food safety.

[0003] However, with the improvement of environmental awareness and in order to ensure the reduction of plastic waste, multi-layer packaging materials have been developed, which include a paper or cardboard layer and one or more layers of plastic or metal films that provide robustness and barrier properties, especially against oxygen and moisture.

[0004] In recent years, environmental awareness has even further increased, especially in terms of waste materials, such as used packaging that is not recycled or properly treated. The industry attaches great importance to this challenge and they spend more and more effort in developing new packaging materials that can be recycled quickly and easily.

[0005] Currently, when manufacturing the structure of multi-layer packaging materials, the plastic layer is applied by known techniques, especially extrusion (extrusion-lamination), or similarly by an adhesive lamination process, and a plastic film with such a high thickness obtained is necessarily provided on the paper.

[0006] Even for relatively low-thickness extruded or laminated polymers in the multi-layer structure as described above, the cohesive strength of the polymer film is very high, and the adhesion level between the polymer and the paper or cardboard (i.e., cellulose) substrate is also very high. This will prevent such polymers from detaching from the substrate during recycling and prevent the recycling and repulping of the cellulose fiber portion during the paper stream recycling process.

[0007] Therefore, in a subsequent recycling process, a multi-layer structure comprising a mixture of paper and a plastic (polymer) film is extruded (by classical techniques such as extrusion lamination or extrusion coating) or adhesively laminated, and has limited recyclability in a standard paper stream recycling process because the plastic layer is too thick to be dispersed and at the same time the same layer has levels of cohesive strength and adhesion with adjacent layers of the structure that are too high to be separated from other material layers, especially from paper fibers. The extruded plastic film remains intact in a pulp bath, thus making it difficult to recycle the pulp from the repulping process.

[0008] Furthermore, the recycling process of the above-known laminates is expensive and energy-consuming and is characterized by a relatively low yield of recycled paper fibers (less than 80% of the total amount of packaging material in the whole structure), and thus is not sufficiently environmentally friendly from the perspective of disposal and recycling. In a paper recycling stream, there is also room for improving the recyclability of the remaining parts of the packaging material, i.e., plastic polymers and metal parts, such as aluminum parts.

[0009] In addition, for packaging intended for food products, good barrier properties are essential for maintaining the safety and quality of the packaged food. Generally, such barrier properties include gas barriers, such as gas barriers to oxygen and water vapor (moisture), and if possible, also liquid tightness.

[0010] One way to provide good moisture barrier in a paper-based packaging material is to introduce a metal or metalloid layer in a so-called "metallized" layer. In this specification, the term "metallized" (e.g., in the expression "metallized barrier paper layer") refers to the deposition of metal or metalloid atoms at the surface of paper or cardboard. Embodiments even including the deposition of alloys of metals and metalloids can be considered. Metalloids are close to metals in some of their characteristics. Aluminum oxide and silicon oxide are examples of metalloids.

[0011] The problem with introducing a metal layer in a paper-based packaging material is the sensitivity of the metal layer to mechanical stress and the poor adhesion of the metal to the paper surface, the poor smoothness and high porosity of the paper material. Mechanical stress can, for example, easily lead to a loss of the desired barrier properties that the metallized packaging material should provide. This can be due to the processing of the multi-layer material during the manufacture of the packaging using, for example, a form-fill-seal packaging machine, whereby during the formation and sealing of the packaging by conventional packaging forming methods, the material is stretched, bent, rolled, compressed, and / or heated. Such packaging manufacturing methods impose high mechanical and / or chemical stress on the material and, in particular, on the ultra-thin metallized layer of metal or metalloid, and thus cause damage to such layer, generating cracks and tears that are mostly irreversible.

[0012] In view of the above, there is a need for a multi-layer metallized paper-based packaging material that simultaneously exhibits: sufficient barrier properties, particularly against oxygen and moisture; high elasticity to mechanical stress such that the same barrier level is maintained even when subjected to conversion processes such as those used in the manufacture of packaging; a significantly reduced plastic polymer content compared to the cellulose material content; and also preferably has the ability to be recycled in a paper stream and / or to be biodegradable under different environmental conditions, particularly (but not limited to) in a marine environment. Summary of the Invention

[0013] The inventors have unexpectedly found that by grafting cellulose with polypeptides (e.g., via succinic acid or citric acid), the elasticity of a paper layer comprising a cellulose graft copolymer is improved, and thus the mechanical properties of the entire packaging multi-layer material comprising the cellulose paper layer are improved.

[0014] Accordingly, the inventors have overcome the technical limitations of known multi-layer barrier structures and have achieved a packaging multi-layer structure that has excellent properties for blocking oxygen and moisture transmission, as well as resistance to liquid contact on the inner or outer surface, while achieving a relatively high total cellulose fiber content.

[0015] In addition, the inventors have successfully formed a multi-layer structure that is completely free of polymer layers formed by extrusion lamination and / or adhesive lamination, providing a multi-layer structure with a very high cellulose fiber to non-cellulose material ratio, and in which due to the solubility of the pre-coating in water, the polymer layer easily disintegrates during repulping, and the relatively high adhesion of the polymer to the metallized layer after metallization (or quasi-metallization) inhibits fragmentation of the metal layer during repulping, resulting in cleaner fibers during the repulping process. Thus, the resulting structure exhibits excellent repulping ability and a high-quality high fiber yield, allowing it to be accepted by standard recycling paper mills in most countries. The content of non-cellulose polymers and vacuum-deposited metal materials is very low, such that the entire material of the present invention easily disintegrates, dissolves, and separates during the recycling process designed for cellulose materials such as paper or cardboard, which is different from the known existing multi-layer barrier structures in the art.

[0016] In one aspect, the present invention provides a cellulose substrate comprising or consisting of a cellulose graft copolymer containing polypeptide side chains. The cellulose graft copolymer can be any cellulose graft copolymer described herein. The cellulose substrate can be a paper substrate, a cardboard substrate, or a hardboard substrate.

[0017] In one aspect, the present invention provides a packaging material comprising at least one paper layer, said at least one paper layer comprising or consisting of a cellulose graft copolymer containing polypeptide side chains. The cellulose graft copolymer can be any cellulose graft copolymer as described herein. The packaging material can be a multi-layer metallized paper-based packaging material.

[0018] In one embodiment, the present invention provides a multi-layer metallized paper-based packaging material (1) which, from its outer side to its inner side, comprises: (i) a paper layer (2) having a grammage in the range of 30 g / m 2 to 120 g / m 2 wherein said paper layer comprises or consists of a cellulose graft copolymer containing polypeptide side chains, (ii) at least one organic barrier layer (3) of a polymer selected from the list consisting of: polyvinyl alcohol (PVOH), ethylene-vinyl alcohol (EVOH), butanediol-vinyl alcohol copolymer (BVOH) or combinations thereof, said polymer being present in an amount of 0.5 g / m 2 to 20 g / m 2 , preferably in an amount of 1 g / m 2 to 10 g / m 2 , more preferably in an amount of 2 g / m 2 to 8 g / m 2 , (iii) at least one inorganic barrier layer (4) selected from the list consisting of: metals, metalloids or combinations thereof, said inorganic layer having a thickness of 1 nm to 100 nm, and (iv) at least one organic heat-sealing layer (5) comprising a polymer capable of heat-sealing, said heat-sealing layer (5) being present in an amount of 2 g / m 2 to 20 g / m 2 , preferably in an amount of 4 g / m 2 to 9 g / m 2 .

[0019] The inorganic layer can comprise a metal or metalloid selected from the list consisting of: aluminum, aluminum oxide (AlOx) or silicon oxide (SiOx), said metal and / or metalloid being deposited by vacuum deposition or transfer metallization. The heat-sealing layer can comprise an acrylic or methacrylic acid polymer grafted with at least one ionomer, preferably a sodium ionomer. Suitably, the molecular weight of the acrylic or methacrylic acid polymer grafted with an ionomer is between 85 g / mol and 90 g / mol. Each organic layer in the organic layers can be deposited onto an adjacent layer by aqueous dispersion or by aqueous solution deposition.

[0020] In some embodiments, the outer surface of the paper layer (2) is covered with an ink layer (6). Suitably, the ink layer is selected from the list consisting of: water-based ink, solvent-free ink, or a combination thereof. In some embodiments, the outer surface of the paper layer or the ink layer is covered with an overprint varnish (OPV) outermost layer (7). Suitably, the overprint varnish outermost layer (7) is a styrene acrylic varnish.

[0021] The packaging material may have a water vapor transmission rate (WVTR) of less than 0.5 g / m 2 / day (measured at 23 °C and 85% relative humidity) and / or an oxygen transmission rate (OTR) of less than 0.1 cm 3 / m 2 / day / bar (measured at 23 °C and 50% RH). The packaging material may have a breaking strain under in-plane tensile load of up to 5% in the longitudinal direction of the paper and up to 15% in the transverse direction of the paper.

[0022] In one aspect, the present invention provides a three-dimensional closed packaging article made of a packaging material according to the present invention, the three-dimensional closed packaging article being obtained by forming, filling with an edible product for human or animal consumption, and then sealing the packaging material.

[0023] In one aspect, the present invention provides the use of a cellulose graft copolymer containing polypeptide side chains (as described herein), a cellulose substrate according to the present invention, or a packaging material according to the present invention for packaging an edible product for human or animal consumption.

[0024] In one aspect, the present invention provides a packaged edible product, the packaged edible product comprising a cellulose graft copolymer containing polypeptide side chains (as described herein), a cellulose substrate according to the present invention, or a packaging material according to the present invention, filled with an edible product for human or animal consumption.

[0025] In one aspect, the present invention provides a cellulose graft copolymer containing polypeptide side chains.

[0026] Any suitable polypeptide can be grafted onto the cellulose backbone. In some embodiments, the polypeptide is collagen or a hydrolyzed form thereof. The polypeptide side chain can be coupled to the cellulose by any suitable method. The polypeptide side chain can be coupled to the cellulose via a linking group. In some embodiments, the polypeptide side chain is coupled to the cellulose via a polycarboxylic acid or its anhydride. In some embodiments, the polypeptide side chain is coupled to the cellulose via a tricarboxylic acid or its anhydride. In some embodiments, the polypeptide side chain is coupled to the cellulose via a tricarboxylic acid or its anhydride selected from one or more of citric acid, isocitric acid, aconitic acid, or glyceric acid. In some embodiments, the polypeptide side chain is coupled to the cellulose via citric acid or its anhydride. In some embodiments, the polypeptide side chain is coupled to the cellulose via citric acid. In some embodiments, the polypeptide side chain is coupled to the cellulose via a dicarboxylic acid or its anhydride. In some embodiments, the polypeptide side chain is coupled to the cellulose via a dicarboxylic acid or its anhydride selected from one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, or sebacic acid. In some embodiments, the polypeptide side chain is coupled to the cellulose via succinic acid or its anhydride. In some embodiments, the polypeptide side chain is coupled to the cellulose via succinic anhydride.

[0027] In one aspect, the present invention provides a method for grafting a polypeptide onto cellulose, the method comprising: (a) functionalizing the cellulose with a linking molecule to provide functionalized cellulose; and (b) grafting the polypeptide onto the functionalized cellulose to provide a cellulose graft copolymer comprising a polypeptide side chain.

[0028] Any suitable polypeptide can be used. In some embodiments, the polypeptide is collagen or a hydrolyzed form thereof. The cellulose can be functionalized with any suitable linking molecule. In some embodiments, the linking molecule is a polycarboxylic acid or its anhydride. In some embodiments, the linking molecule is a tricarboxylic acid or its anhydride. In some embodiments, the linking molecule is a tricarboxylic acid or its anhydride selected from one or more of citric acid, isocitric acid, aconitic acid, or glyceric acid. In some embodiments, the linking molecule is citric acid or its anhydride. In some embodiments, the linking molecule is citric acid. In some embodiments, the linking molecule is a dicarboxylic acid or its anhydride. In some embodiments, the linking molecule is a dicarboxylic acid or its anhydride selected from one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, or sebacic acid. In some embodiments, the linking molecule is succinic acid or its anhydride. In some embodiments, the linking molecule is succinic anhydride. Any suitable reaction conditions can be used to functionalize the cellulose. Suitably, the polycarboxylic acid or its anhydride is incubated with a nucleophilic catalyst, optionally wherein the nucleophilic catalyst is 4-dimethylaminopyridine (DMAP).

[0029] Any suitable reaction conditions can be used to graft polypeptides onto cellulose. Appropriately, the polypeptides are grafted onto functionalized cellulose by a carbodiimide crosslinking reaction. In some embodiments, the carbodiimide crosslinking agent is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDAC), optionally wherein N-hydroxysuccinimide (NHS) is included in the carbodiimide crosslinking reaction.

[0030] In one aspect, the present invention provides a cellulose graft copolymer that is obtained or can be obtained by the method according to the present invention.

[0031] In one aspect, the present invention provides a functionalized cellulose, wherein the functionalized cellulose is functionalized with a polycarboxylic acid or its acid anhydride.

[0032] In some embodiments, the functionalized cellulose is functionalized with a tricarboxylic acid or its acid anhydride. In some embodiments, the functionalized cellulose is functionalized with a tricarboxylic acid or its acid anhydride selected from one or more of citric acid, isocitric acid, aconitic acid, or glyceric acid. In some embodiments, the functionalized cellulose is functionalized with citric acid or its acid anhydride. In some embodiments, the functionalized cellulose is functionalized with citric acid. In some embodiments, the functionalized cellulose is functionalized with a dicarboxylic acid or its acid anhydride. In some embodiments, the functionalized cellulose is functionalized with a dicarboxylic acid or its acid anhydride selected from one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, or sebacic acid. In some embodiments, the functionalized cellulose is functionalized with succinic acid or its acid anhydride. In some embodiments, the functionalized cellulose is functionalized with succinic anhydride. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Additional features and advantages of the present invention are described in the following description of presently preferred embodiments, which is given with reference to the accompanying drawings, and these features and advantages will be apparent from the description, wherein:

[0034] Figure 1 An exemplary reaction scheme showing the grafting of collagen onto cellulose by a two-step coupling using succinic anhydride is shown.

[0035] Figure 2 It is shown that the handsheets formed from the recovered grafted cellulose fibers have improved hydrophobicity. (A) Exemplary photographs of water droplets on small handsheets with and without grafted collagen are shown. (B) Contact angles of handsheets with and without grafted collagen over time. (C) Rate of change of contact angles of handsheets with and without grafted collagen for different volumes of water.

[0036] Figure 3The presence of collagen in the recovered grafted cellulose fibers was confirmed. (A) SEM images and EDX measurements of dry cellulose fibers. (B-C) SEM images and EDX measurements of wetted cellulose fibers: (B) EDX measurements performed on the background; (C) EDX measurements on the fibers.

[0037] Figure 4 An exemplary reaction scheme showing the grafting of collagen onto cellulose by a two-step coupling using citric acid is shown.

[0038] Figure 5 The first embodiment of the multilayer structure according to the present invention is shown;

[0039] Figure 6 The second embodiment of the multilayer structure according to the present invention is shown. Detailed Description

[0040] The preferred features and embodiments of the present invention will now be described by way of non-limiting examples. Those skilled in the art will understand that they can combine all the features of the present invention disclosed herein without departing from the scope of the present invention as disclosed.

[0041] It must be noted that, as used herein and in the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. As used herein, the terms "comprising" and "consisting of" are synonymous with "including", "containing", and are inclusive of end values or open-ended, and do not exclude additional unrecited members, elements, or steps. The terms "comprising / including" and "consisting of" also include the term "consisting of". Numerical ranges include the numbers defining the range.

[0042] All publications mentioned in the specification are incorporated herein by reference. The publications discussed herein are provided only for their disclosure prior to the filing date of this patent application. Nothing herein should be construed as an admission that such publications constitute prior art to the claims appended hereto.

[0043] Cellulose graft copolymer

[0044] In one aspect, the present invention provides a graft copolymer comprising a cellulose backbone and a polypeptide side chain.

[0045] As used herein, "graft copolymer" may refer to a branched copolymer having one or more polymer branches attached to the backbone of a main polymer chain, where the components of the branches are structurally different from the components of the main chain (see, e.g., Feng, C. et al., 2011, Chemical Society Reviews, 40(3), pp. 1282-1295). The "backbone" of a graft copolymer may also be referred to as the "main chain", and the "branches" of a graft copolymer may also be referred to as "side chains" or "pendants".

[0046] Cellulose backbone

[0047] The graft copolymers of the present invention may be referred to as cellulose graft copolymers. As used herein, "cellulose graft copolymer" may refer to a graft copolymer in which the main polymer chain is cellulose (see, e.g., Kang, H. et al., 2015, Polymer, 70, pp. A1-A16).

[0048] Cellulose is a polysaccharide composed of a straight chain of hundreds to thousands of β(1→4)-linked D-glucose units and may have the following molecular formula:

[0049]

[0050] Any suitable source of cellulose may be used in the present invention (see, e.g., Lavanya, D.K.P.K. et al., 2011, International Journal of Drug Formulation and Research, 2(6), pp. 19-38). The main industrial source of cellulose is vascular plants. For example, most of the cellulose used in paper products is derived from wood pulp. The molecular weight of cellulose may depend on its source and the extraction conditions used for purification.

[0051] The cellulose graft copolymers of the present invention may be in the form of cellulose fibers, which are typically extracted from plants, seeds, or trees; such fibers contain not only cellulose molecules but also hemicellulose and lignin.

[0052] Polypeptide side chain

[0053] In the graft copolymers of the present invention, the graft polymer branches are polypeptides.

[0054] As used herein, "polypeptide" can refer to multiple amino acid residues linked by peptide bonds. Suitably, the polypeptide has a length of at least about 10 amino acids, at least about 15 amino acids, or at least about 20 amino acids. Any suitable polypeptide can be grafted onto the backbone. Suitably, the polypeptide is a water-soluble polypeptide. Suitably, the polypeptide is a fibrous polypeptide or a globular polypeptide. Suitable fibrous polypeptides can include collagen. Suitable globular polypeptides can include any type of albumin or globulin. Suitable polypeptides include collagen, ovalbumin, serum albumin, lactoglobulin, or their hydrolyzed forms. In some embodiments, the polypeptide is selected from one or more of the following: collagen, ovalbumin, serum albumin, lactoglobulin, or their hydrolyzed forms. In a preferred embodiment, the polypeptide is collagen or its hydrolyzed form.

[0055] Collagen consists of a right-handed bundle of three parallel left-handed polyproline type II (PPII) helices. The tight packing of the PPII helices within the triple helix requires that every third residue must be Gly, resulting in a repeating XaaYaaGly sequence, where Xaa and Yaa can be any amino acid. This repetition occurs in all types of collagen. The amino acids at the Xaa and Yaa positions of collagen are typically (2S)-proline (Pro, 28%) and (2S,4R)-4-hydroxyproline (Hyp, 38%), respectively. ProHypGly is the most common triplet in collagen (10.5%) (see, for example, Shoulders, M.D. and Raines, R.T., 2009. Annual review of biochemistry, 78, p. 929).

[0056] Any suitable source of collagen can be used in the present invention (see, for example, Silvipriya, K.S. et al., 2015. Journal of Applied Pharmaceutical Science, 5(3), pp. 123-127). Animal sources include cows, pigs, and fish. Collagen is mainly present in connective tissues such as cartilage, bone, tendon, ligament, and skin.

[0057] Any suitable form of hydrolyzed collagen can be used in the present invention (see, for example, Mariod, A.A. and Fadul, H., 2013. Acta Scientiarum Polonorum Technologia Alimentaria, 12(2), pp. 135-147). Suitable forms of hydrolyzed collagen include gelatin, which is obtained by thermal denaturation of collagen. In some embodiments, the polypeptide side chain is gelatin.

[0058] Linking group

[0059] The polypeptide side chain can be grafted onto the main chain by any suitable coupling chemistry. Suitably, the polypeptide side chain is coupled to the main chain through a linking group. Suitably, the graft copolymer has the following formula:

[0060]

[0061] The linking group can be any suitable linking group, such as any of the linking groups described herein. Suitably, the linking group can be an aliphatic group (e.g., having 1 to 8 carbon atoms), which is optionally substituted with one or more functional groups (e.g., one or more alcohol groups, carboxyl groups, and / or amide groups), optionally coupled to one or more polypeptides, and / or optionally crosslinked to one or more other main chains.

[0062] Suitably, the linking group is bonded to the main chain through an ester bond (e.g., at the 6-hydroxy group of cellulose) and bonded to the polypeptide through a peptide bond (e.g., at the N-terminus of the polypeptide). The linking group can be derived from a molecule (or its anhydride) comprising two or more carboxylic acid groups. In this context, "derived from" can mean that, prior to the grafting reaction, the linking group is a molecule comprising two or more carboxylic acid groups (or its anhydride), and after the grafting reaction, one carboxylic acid group forms an ester bond (e.g., at the 6-hydroxy group of cellulose) and one carboxylic acid group forms a peptide bond (e.g., at the N-terminus of the polypeptide). Suitably, the graft copolymer has the following formula:

[0063]

[0064] The linking group can be an aliphatic group (e.g., having 1 to 8 carbon atoms), which is optionally substituted with one or more functional groups (e.g., one or more alcohol groups), optionally coupled to one or more polypeptides, and / or optionally crosslinked to one or more other main chains.

[0065] The molecule (or its anhydride) comprising two or more carboxylic acid groups includes a polycarboxylic acid or its anhydride. As used herein, "polycarboxylic acid" can refer to an organic compound containing two or more carboxyl groups (-COOH), and includes dicarboxylic acids and tricarboxylic acids. As used herein, "anhydride" can refer to an organic compound having two acyl groups bonded to the same oxygen atom, and "carboxylic acid anhydride" can refer to an anhydride whose parent acid is a carboxylic acid.

[0066] In some embodiments, the linking group is derived from a dicarboxylic acid or its anhydride. In some embodiments, the linking group is derived from a dicarboxylic anhydride. Suitable dicarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, acetylenedicarboxylic acid, glutaconic acid, muconic acid, pentynedioic acid, citraconic acid, mesaconic acid, and itaconic acid. Suitable dicarboxylic anhydrides include malonic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, pimelic anhydride, suberic anhydride, azelaic anhydride, sebacic anhydride, maleic anhydride, glutaconic anhydride, muconic anhydride, citraconic anhydride, mesaconic anhydride, and itaconic anhydride. Suitably, the graft copolymer has the following formula:

[0067]

[0068] R can be an aliphatic group (e.g., having 1 to 8 carbon atoms), optionally substituted by one or more functional groups (e.g., one or more alcohol groups). In some embodiments, R is an aliphatic group having 1 to 8 carbon atoms. In some embodiments, R is an aliphatic group having 2 to 4 carbon atoms. In some embodiments, R is an aliphatic group having 2 to 3 carbon atoms.

[0069] In some embodiments, the linking group is derived from succinic acid or its anhydride. In some embodiments, the linking group is derived from succinic anhydride. Suitably, the graft copolymer has the following formula:

[0070]

[0071] In some embodiments, the linking group is derived from a tricarboxylic acid or its anhydride. In some embodiments, the linking group is derived from a tricarboxylic acid. Suitable tricarboxylic acids include citric acid, isocitric acid, cis-aconitic acid, trans-aconitic acid, and glyceric acid. Suitable tricarboxylic anhydrides include citric anhydride, citric 1,5-anhydride, isocitric anhydride, cis-aconitic anhydride, trans-aconitic anhydride, and glyceric anhydride.

[0072] Compared with dicarboxylic acids or their anhydrides, tricarboxylic acids or their anhydrides may have the advantage of allowing additional branching, e.g., by (i) coupling to two polypeptides and / or (ii) crosslinking the main chain to other main chains. Suitably, the graft copolymer has the following formula:

[0073]

[0074] R can be an aliphatic group (e.g., having 1 to 8 carbon atoms), optionally substituted by one or more functional groups (e.g., one or more alcohol groups). In some embodiments, R is an aliphatic group having 1 to 8 carbon atoms, optionally substituted by one or more alcohol groups. In some embodiments, R is an aliphatic group having 3 to 5 carbon atoms, optionally substituted by one or more alcohol groups. In some embodiments, R is an aliphatic group having 3 to 4 carbon atoms, optionally substituted by one or more alcohol groups. In some embodiments, R is an aliphatic group substituted by one alcohol group.

[0075] In some embodiments, the linking group is derived from citric acid or its anhydride. In some embodiments, the linking group is derived from citric acid. Suitably, the graft copolymer has the following formula:

[0076]

[0077] Method for grafting polypeptide onto cellulose

[0078] In one aspect, the present invention provides a method for grafting a polypeptide onto a cellulose backbone.

[0079] The "grafting onto" or "grafting to" method may involve using a backbone having functional groups randomly distributed along the chain. The formation of the graft copolymer results from a coupling reaction between the functionalized backbone and the end groups of the reactive side chains. These coupling reactions can be made possible by chemically modifying the backbone to functionalize it.

[0080] The method of the present invention may include the following steps: (a) functionalizing the cellulose; and (b) grafting the polypeptide onto the functionalized cellulose. Any suitable reaction conditions can be used for steps (a) and (b). Suitable reaction conditions are described below.

[0081] Step (a): Functionalize the backbone

[0082] Any suitable method can be used to functionalize the backbone. For example, step (a) may include the step of functionalizing the backbone with a linking molecule to obtain a functionalized backbone. In one aspect, the present invention provides a functionalized backbone obtainable or obtained by step (a). In some embodiments, the functionalized backbone includes a carboxylic acid functional group.

[0083] The linking molecule can be any suitable linking molecule, such as any of the linking molecules described herein. The linking molecule may include two or more carboxylic acid groups (or their anhydrides). Suitably, the functionalized backbone has the following formula:

[0084]

[0085] The linking group may be an aliphatic group (e.g., having 1 to 8 carbon atoms), which is optionally substituted with one or more functional groups (e.g., one or more alcohol groups) and is optionally crosslinked with one or more other backbones.

[0086] In some embodiments, the linking molecule is a dicarboxylic acid or its anhydride. In some embodiments, the linking molecule is a dicarboxylic anhydride. Suitable dicarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, acetylenedicarboxylic acid, glutaconic acid, muconic acid, pentynedioic acid, citraconic acid, mesaconic acid, and itaconic acid. Suitable dicarboxylic anhydrides include malonic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, pimelic anhydride, suberic anhydride, azelaic anhydride, sebacic anhydride, maleic anhydride, glutaconic anhydride, muconic anhydride, citraconic anhydride, mesaconic anhydride, and itaconic anhydride. Appropriately, the functionalized backbone has the following formula:

[0087]

[0088] R may be an aliphatic group (e.g., having 1 to 8 carbon atoms), which is optionally substituted with one or more functional groups (e.g., one or more alcohol groups). In some embodiments, R is an aliphatic group having 1 to 8 carbon atoms. In some embodiments, R is an aliphatic group having 2 to 4 carbon atoms. In some embodiments, R is an aliphatic group having 2 to 3 carbon atoms.

[0089] In some embodiments, the linking molecule is succinic acid or its anhydride. In some embodiments, the linking molecule is succinic anhydride. Appropriately, the functionalized backbone has the following formula:

[0090]

[0091] In some embodiments, the linking molecule is a tricarboxylic acid or its anhydride. In some embodiments, the linking molecule is a tricarboxylic acid. Suitable tricarboxylic acids include citric acid, isocitric acid, cis-aconitic acid, trans-aconitic acid, and glyceric acid. Suitable tricarboxylic anhydrides include citric anhydride, citric 1,5-anhydride, isocitric anhydride, cis-aconitic anhydride, trans-aconitic anhydride, and glyceric anhydride. Appropriately, the functionalized backbone has the following formula:

[0092]

[0093] R can be an aliphatic group (e.g., having 1 to 8 carbon atoms), optionally substituted with one or more functional groups (e.g., one or more alcohol groups). In some embodiments, R is an aliphatic group having 1 to 8 carbon atoms, optionally substituted with one or more alcohol groups. In some embodiments, R is an aliphatic group having 3 to 5 carbon atoms, optionally substituted with one or more alcohol groups. In some embodiments, R is an aliphatic group having 3 to 4 carbon atoms, optionally substituted with one or more alcohol groups. In some embodiments, R is an aliphatic group substituted with one alcohol group.

[0094] In some embodiments, the linking molecule is citric acid or its anhydride. In some embodiments, the linking molecule is citric acid. Suitably, the functionalized backbone has the following formula:

[0095]

[0096] Suitably, the linking molecule can be present in the reaction mixture in an amount of at least 0.5 equivalents, at least 1.0 equivalent, or at least 1.5 equivalents. Suitably, the linking molecule is present in the reaction mixture in an amount of 10.0 equivalents or less, 5.0 equivalents or less, or 4.0 equivalents or less. Suitably, the linking molecule can be present in the reaction mixture in an amount of 0.5 equivalents to 10.0 equivalents, 1.0 equivalents to 5.0 equivalents, or 1.5 equivalents to 4.0 equivalents.

[0097] The linking molecule can be coupled to the backbone under any suitable reaction conditions. For example, when the reaction is an esterification reaction, it can be carried out in the presence of a catalyst and heat. Suitably, the reaction mixture contains a nucleophilic catalyst, such as 4-dimethylaminopyridine (DMAP). Suitably, the nucleophilic catalyst (e.g., DMAP) can be added in an amount of 0.1 equivalent. Suitably, the reaction can be carried out at 95 °C for 24 hours. For example, when the reaction is with a primary alcohol and a dicarboxylic acid, N-hydroxysuccinimide (NHS) or its water-soluble analogue sulfo-NHS can be included to activate the carboxylic acid group.

[0098] Any suitable method known in the art can be used to monitor the progress of the reaction and / or determine that the functionalized backbone has been obtained. Suitably, infrared (IR) spectroscopy such as Fourier transform infrared (FT-IR) spectroscopy can be used to determine that the functionalized backbone has been obtained. For example, functionalization with a carboxylic acid can be determined by monitoring the appearance of the carboxylic acid signal at 1650 cm -1 −1. Alternatively, solid-state NMR can be used to determine that the functionalized backbone has been obtained.

[0099] Step (b): Graft the polypeptide onto the functionalized backbone

[0100] Any suitable method can be used to graft the polypeptide onto the functionalized backbone. In one aspect, the present invention provides a graft copolymer obtainable by or capable of being obtained by step (b).

[0101] For example, if the functionalized backbone includes a carboxylic acid functional group, then the polypeptide can be grafted to the functionalized backbone through a carboxyl-reactive cross-linking reaction, such as through a carbodiimide cross-linking reaction. Any suitable carbodiimide cross-linking agent can be used, such as 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC) or N,N′-dicyclohexylcarbodiimide (DCC). EDAC reacts with the carboxylic acid group to form a reactive O-acylisourea intermediate, which is readily displaced by nucleophilic attack from a primary amine group in the reaction mixture. The primary amine forms an amide bond with the original carboxyl group, and the EDAC by-product is released as a soluble urea derivative. Appropriately, EDAC can be added to the reaction mixture in an amount of 0.5 equivalents.

[0102] Any suitable reaction conditions can be used. For example, N-hydroxysuccinimide (NHS) or its water-soluble analogue sulfo-NHS can be included in the carbodiimide coupling reaction to increase efficiency or to generate amine-reactive intermediates. EDAC couples NHS to the carboxyl group, forming an NHS ester, which is much more stable than the O-acylisourea intermediate while allowing efficient conjugation with primary amines. Appropriately, NHS can be added to the reaction mixture in an amount of 1.5 equivalents. A base can be added to the reaction mixture, for example to deprotonate the carboxylic acid. For example, triethylamine (TEA) can be added to the reaction mixture in an amount of 0.1 equivalents. Appropriately, the reaction can be carried out at 95 °C for 24 hours.

[0103] Any suitable method known in the art can be used to monitor the progress of the reaction and / or to determine that the graft copolymer has been obtained. Appropriately, infrared (IR) spectroscopy such as Fourier transform infrared (FT-IR) spectroscopy can be used to determine that the graft copolymer has been obtained. For example, the grafting via an amide bond to the polypeptide can be determined by monitoring the appearance of amide fragments at 1650, 1550, and 1420 cm -1 in the IR spectrum. Alternatively, solid-state NMR can be used to determine that the graft copolymer has been obtained. Alternatively, the Kjeldahl method can be used to determine that the graft copolymer contains polypeptide side chains (see, for example, Bradstreet, R.B., 1954, Analytical Chemistry, 26(1), pages 185-187).

[0104] Cellulose substrate

[0105] In one aspect, the present invention provides a cellulose substrate comprising, consisting of, or obtainable by or through the graft copolymer of the present invention or a graft copolymer obtainable by the method of the present invention.

[0106] As used herein, "cellulose substrate" may include any base material containing cellulose, such as paper, cardboard, hardboard, and wood film. The substrate can be used in conversion processes such as printing or coating, and generally refers to the base material on which, for example, an image will be printed. The cellulose substrate can be used to manufacture articles or substances such as packaging materials. In some embodiments, the cellulose substrate is a paper substrate, a cardboard substrate, or a hardboard substrate.

[0107] Suitably, the cellulose substrate comprises an amount of the graft copolymer of the present invention or a graft copolymer obtainable by or through the method of the present invention of at least 10 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, or at least 90 wt%.

[0108] Packaging material

[0109] In one aspect, the present invention provides a packaging material comprising the graft copolymer of the present invention, a graft copolymer obtainable by or through the method of the present invention, or the cellulose substrate of the present invention.

[0110] The packaging material may include at least one paper layer comprising, consisting of, or obtainable by or through the graft copolymer of the present invention, a graft copolymer obtainable by the method of the present invention, or the cellulose substrate of the present invention.

[0111] As used herein, "packaging material" may refer to any article or substance intended or capable of coming into contact with an edible product for human or animal consumption, including containers such as cartons, boxes, and cases, or wrapping and covering materials such as paper and wax paper.

[0112] The present invention also relates to a three-dimensional closed packaging article made of the packaging material described herein (such as the multi-layer metallized paper-based packaging material described herein), which is obtained by forming, then filling an edible product for human or animal consumption, and then sealing the packaging material.

[0113] The present invention also relates to the use of the packaging material described herein (such as the multi-layer metallized paper-based packaging material described herein) for packaging an edible product for human or animal consumption.

[0114] The present invention also relates to a packaged edible product, which comprises a packaging material as described herein (e.g., the multilayer metallized paper-based packaging material as described herein), filled with an edible product for human or animal consumption. Preferably, the edible product is a powder, gel or kibble, and is selected from the list of: soluble coffee, nutritional compositions for infants, adults or the elderly, soups, confectionery or candies, chocolate-like products, dry animal food, dairy products.

[0115] Multilayer metallized paper-based packaging material

[0116] In a preferred embodiment, the packaging material is a multilayer metallized paper-based packaging material. The "multilayer metallized paper-based packaging material" may include a paper layer, a pre-metallization coating, a metallization layer and a post-metallization coating.

[0117] The paper layer may comprise, consist of, or be composed of the graft copolymer of the present invention, a graft copolymer obtainable or capable of being obtained by the method of the present invention, or the cellulose substrate of the present invention. Suitably, the grammage of the paper layer is in the range of 30 g / m 2 to 120 g / m 2 . Suitably, the paper layer contains at least 10 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt% or at least 90 wt% of the graft copolymer of the present invention or a graft copolymer obtainable or capable of being obtained by the method of the present invention.

[0118] The pre-metallization coating may comprise or consist of at least one organic barrier layer of a polymer selected from the list of: polyvinyl alcohol (PVOH), ethylene-vinyl alcohol (EVOH), butanediol-vinyl alcohol copolymer (BVOH) or combinations thereof. The at least one organic barrier layer may be present in an amount of 0.5 g / m 2 to 20 g / m 2 , preferably in an amount of 1 g / m 2 to 10 g / m 2 , more preferably in an amount of 2 g / m 2 to 8 g / m 2 .

[0119] The metallization layer may comprise or consist of at least one inorganic barrier layer selected from the list of: metals, metalloids or combinations thereof. The thickness of the metallization layer may be from 1 nm to 100 nm. In a preferred embodiment, the at least one inorganic barrier layer comprises a metal or metalloid selected from the list of: aluminum, aluminum oxide (AlOx) or silicon oxide (SiOx). The metal and / or metalloid may be deposited by vacuum deposition or transfer metallization. In a particularly preferred embodiment, the at least one inorganic barrier layer is a vacuum-deposited aluminum layer.

[0120] After metallization, the coating may comprise or consist of at least one organic heat-sealing layer, which contains a polymer capable of heat-sealing. The at least one organic heat-sealing layer may be present in an amount of 2 g / m 2 to 20 g / m 2 and preferably in an amount of 4 g / m 2 to 9 g / m 2 .

[0121] Each organic layer in the organic layer is preferably deposited onto an adjacent layer by means of an aqueous dispersion or by means of an aqueous solution deposition.

[0122] In a preferred embodiment, the multi-layer metallized paper-based packaging material comprises, from its outer side to its inner side:[[]]

[0123] - a paper layer having a grammage in the range of 30 g / m 2 to 120 g / m 2 , wherein the paper layer comprises or consists of a graft copolymer according to the invention;

[0124] - at least one organic barrier layer of a polymer selected from the list consisting of:[[]]

[0125] polyvinyl alcohol (PVOH), ethylene-vinyl alcohol (EVOH), butanediol-vinyl alcohol copolymer (BVOH) or combinations thereof, the amount of the polymer being 0.5 g / m 2 to 20 g / m 2 ,

[0126] preferably in an amount of 1 g / m 2 to 10 g / m 2 , more preferably in an amount of 2 g / m 2 to 8 g / m 2 ;

[0127] - at least one inorganic barrier layer selected from the list consisting of: metals, metalloids or combinations thereof, the thickness of the inorganic layer being in the range of 1 nm to 100 nm; and

[0128] - at least one organic heat-sealing layer containing a polymer capable of heat-sealing, the heat-sealing layer being applied in an amount in the range of 2 g / m 2 to 20 g / m 2 and preferably in an amount in the range of 4 g / m 2 to 9 g / m 2 .

[0129] In all embodiments of the invention described herein, the multilayer structure may include other additional and optional layers which are not fully described in detail herein. Such layers may include, for example, a printed layer on the outer surface of the paper layer, and optionally a protective layer deposited outside the printed layer, and thus constitute the outermost layer of the entire structure. The printed layer and the optional protective layer are not described in more detail because they are techniques known to those skilled in the art.

[0130] In some embodiments, the outer surface of the paper layer is covered with an ink layer. The thickness of the ink layer may be 0.5 g / m 2 to 5 g / m 2 . In a preferred embodiment, the ink layer is selected from the list consisting of: water-based ink, solvent-free ink, or a combination thereof.

[0131] More preferably, the outer surface of the paper layer or the ink layer is covered with an overprint varnish (OPV) outermost layer. The grammage of the OPV layer may be 0.5 g / m 2 to 10 g / m 2 . The optional OPV layer (if present) may also contribute to improving the resistance of the barrier paper to wet expansion strain, particularly providing improved moisture barrier (water vapor transmission rate or "WVTR") under high humidity conditions. In an advantageous embodiment, the overprint varnish outermost layer is a styrene acrylic varnish.

[0132] The multilayer metallized paper-based packaging material according to the invention advantageously achieves barrier properties against oxygen and moisture as follows: a water vapor transmission rate (WVTR) of less than 0.5 g / m 2 / day (measured at 23 °C, 85% relative humidity) and / or an oxygen transmission rate (OTR) of less than 0.1 cm 3 / m 2 / day / bar (measured at 23 °C, 50% RH). These values are measured according to the flexible test standard ASTM F392 or an equivalent standard, after subjecting the sample to an in-plane tensile prestrain of up to 2% and also after subjecting the sample to 3 cycles of a Gelboflex test device.

[0133] The multilayer metallized paper-based packaging material according to the invention preferably has a fracture strain under in-plane tensile load of up to 5% in the longitudinal direction of the paper and up to 15% in the transverse direction of the paper. The fracture strain of the entire paper structure is 2.5% in the longitudinal direction and 9% in the transverse direction, which results in higher mechanical elasticity.

[0134] According to the paper recycling regulations in most regions or countries, the multilayer structure according to the invention is preferably designed to be eligible for recycling in a standard recycled paper stream process. The recyclability in the paper stream is achieved by the multilayer structure according to the invention, wherein:

[0135] - The fiber content is predominant relative to all the components contained therein (the definition of recyclability in the paper stream depends on national legislation, but on average, materials are required to contain at least 80% fiber to be acceptable for paper recycling processes dedicated to paper materials), and

[0136] - The inorganic layer is ultrathin (i.e., a few nanometers, typically from 1 nm to 100 nm) and its thickness consists of a few atoms,

[0137] - The organic polymer layer is deposited entirely by deposition coating with an aqueous dispersion or an aqueous solution, which means that the layer thus obtained is thin enough relative to the paper material thickness to achieve a very high paper material content of the overall structure, which makes the entire structure compatible with the paper recycling processes illustrated herein,

[0138] - The organic barrier layer preferably contains a water-soluble polymer (i.e., PVOH, EVOH, and / or

[0139] BVOH), which makes it easier to separate the fibers from the rest of the materials in the structure, especially from the cellulose content.

[0140] Figure 5 A first embodiment of the present invention is depicted. In this embodiment, the multilayer structure 1 includes, in sequence from its outer side (i.e., the material side facing the outside of the package made therefrom) towards its inner side (i.e., the inner side in contact with the packaged product in the package made therefrom):

[0141] - A highly smooth paper layer 2, optionally having a grammage of 62 g / m 2 , which highly smooth paper layer contains the graft copolymer of the present invention, a graft copolymer obtainable by or capable of being obtained by the method of the present invention, or the cellulose substrate of the present invention, or consists thereof.

[0142] - A first organic polyvinyl alcohol-based (PVOH) pre-metallized coating 3, which mainly provides gas

[0143] (especially oxygen) barrier properties and is optionally applied as an aqueous solution at a weight of 3 g / m 2 .

[0144] - A vacuum-deposited inorganic aluminum layer 4, optionally having a thickness of 40 nm, which mainly provides water vapor barrier performance, and

[0145] - A second organic coating 5 based on a methacrylic acid ionomer coating, which serves as a heat-sealing layer and is optionally applied in the form of an aqueous dispersion at a weight of 5 g / m 2 .

[0146] In this first embodiment, the deposition techniques for the first and second organic layers, as mentioned above, can improve their recyclability in the paper flow process. The structure 1 of this first embodiment can achieve high moisture and gas barrier properties, with an oxygen transmission rate (OTR) value of less than 0.5 cm 3 / m 2 / day measured at 23 °C and 50% relative humidity (RH), and a water vapor transmission rate (WVTR) value of less than 0.5 g / m 2 / day measured at 23 °C and 85% RH.

[0147] The breaking strain of the overall structure 1 can be measured to be 2.5% longitudinally and 9% transversely. These values provide excellent elastic properties, which allow the protection of the aluminum layer during the processing of the structure in conventional packaging forming processes. When packaging is made from this material, no rupture of the aluminum layer occurs during bending, stretching, and / or sealing of the material, which results in maintaining the same level of OTR and WVTR barrier characteristics before and after forming the packaging from the multi-layer structural material.

[0148] In Figure 6 is depicted a structure similar to the structure described above with respect to Figure 5 However, in this second exemplary embodiment of the present invention, the outer surface of the paper layer 2 is covered with the following two layers, from the outer side to the inside of the packaging material in sequence:

[0149] - The outermost overprint varnish layer 7 based on acrylic, which is optionally applied in the form of an aqueous dispersion at a weight of 1 g / m 2

[0150] - The water-based ink layer 6, which is optionally applied in the form of an aqueous dispersion at a weight of 1 g / m 2 ; this water-based ink layer 6 is located between the outermost overprint varnish layer 7 and the paper layer 2.

[0151] The remaining layers in structure 1 remain similar to the structure described with reference to Figure 5 namely:

[0152] - The highly smooth paper layer 2, optionally with a grammage of 62 g / m 2 , which contains the graft copolymer of the present invention, the graft copolymer obtainable by or capable of being obtained by the method of the present invention, or the cellulose substrate of the present invention, or is composed of them.

[0153] - The first organic polyvinyl alcohol-based (PVOH) pre-metallized coating 3, which mainly provides gas (especially oxygen) barrier characteristics and is optionally applied as an aqueous solution at a weight of 3 g / m 2

[0154] - An inorganic aluminum layer 4 deposited by vacuum, optionally having a thickness of 40 nm, which mainly provides water vapor barrier properties, and

[0155] - A second organic coating 5 of a methacrylic acid ionomer-based coating, which is optionally applied in the form of an aqueous dispersion at a weight of 5 g / m 2 of the substrate.

[0156] The structure corresponding to the above embodiments can meet the requirements for the recyclability of materials or packages made therefrom under standard recycling mill conditions.

[0157] Method for manufacturing a multilayer metallized paper-based packaging material

[0158] Generally, in this specification, "extrusion coating" refers to a method of providing a polymer layer by using an extruder that forces a molten thermoplastic resin (such as polyethylene) through a horizontal slot die onto a moving web of a substrate (such as paper). The resulting product is a permanently coated web structure.

[0159] So-called "extrusion lamination" refers to a method similar to extrusion coating, in which a polymer resin is extruded between two substrates (such as a layer of paper and another layer of polymer film) and acts as an adhesive.

[0160] So-called "adhesive lamination" refers to a method in which a paper material is coated with an adhesive and laminated to a second paper or cardboard material. During the lamination process, two thick material layers are joined by extrusion lamination or adhesive lamination, where the thickness of each layer is much greater than the thickness obtained by dispersion coating.

[0161] So-called "dispersion coating" refers to a coating technique in which an aqueous dispersion of fine polymer particles or a polymer solution is applied to the surface of paper or cardboard in such a way that a solid, pore-free film is formed after drying. Dispersion coating can be carried out by gravure printing, letterpress printing, rod, blade, slot die, curtain coater, roll coating, or any other known paper coating method. Dispersion coating can produce a much thinner layer than extrusion lamination and / or adhesive lamination because the polymer is mixed in an aqueous solution. This brings advantages in terms of polymer usage, its barrier properties, and the recyclability of the resulting paper structure. The goal of dispersion coating is to obtain a barrier layer against water, water vapor, oils, fats, gases, etc. through environmentally friendly coating. Another goal is to prepare the surface of paper materials for vacuum deposition processes.

[0162] Example

[0163] The present invention will now be further described by way of examples, which are intended to assist those skilled in the art in practicing the present invention and are not intended to limit the scope of the present invention in any way.

[0164] Example 1: Grafting collagen onto cellulose via a succinic acid linking group

[0165] The grafting of collagen is carried out through a two-step reaction (see the reaction scheme in Figure 1 ).

[0166] The first step involves the grafting through succinic anhydride to functionalize cellulose with a carboxylic acid spacer. 4-Dimethylaminopyridine (DMAP) is used to partially deprotonate the cellulose hydroxyl groups, which then attack the carbonyl group of the anhydride, opening it and releasing the carboxylic acid. The first step of the reaction can be monitored by measuring the IR spectrum and tracking the increase in the carboxylic acid signal at 1650 cm -1 . To complete, the reaction is left overnight. The resulting pulp is filtered and thoroughly washed with water until a neutral pH is obtained.

[0167] Then the carboxylic acids are activated using the carbodiimide crosslinking agent 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDAC) and N-hydroxysuccinimide (NHS) to allow grafting at the N-terminus of collagen. The grafting of collagen is monitored by observing the appearance of amide fragments at 1650, 1550, and 1420 cm -1 in the IR spectrum. The reaction is left overnight, after which the pulp is filtered and thoroughly washed with softened water.

[0168] Handsheets are formed from the recovered grafted cellulose fibers. As observed in Figure 2 A, the application of water droplets on small handsheets with and without grafted collagen shows that in the presence of grafted collagen, the contact angle of the water droplets is much larger. This indicates that the hydrophobicity of the handsheet is increased compared to the handsheet without grafted collagen, and the collagen buffers the water absorption of cellulose, resulting in a more hydrophobic surface. Monitoring the contact angle over time shows that in the presence of collagen, the adsorption of water droplets (observed by the decrease in the contact angle over time) is slower compared to the reference cellulose (see Figure 2 B). This is confirmed when applying different volumes of water (see Figure 2 C). Systematically, in the presence of grafted collagen, the contact slope over time is smaller, indicating less water adsorption and thus increased hydrophobicity of the fibers due to water being adsorbed by collagen rather than cellulose.

[0169] EDX measurements further demonstrate the grafting of collagen onto cellulose (see Figure 3 A). This shows a higher nitrogen content compared to the cellulose reference, confirming the presence of collagen. Adding a drop of water to the sample causes the sample to swell (see Figure 3 B - C). As can be seen in the SEM images, after wetting, a swelling effect is observed on the surface of the sample, and when performing EDX on the transparent fibers and on the background, a higher nitrogen content is observed, indicating collagen swelling, resulting in an increased nitrogen content.

[0170] Example 2: Grafting collagen onto cellulose via a citric acid linking group

[0171] Grafting of collagen to cellulose was also achieved with citric acid (see the reaction scheme in Figure 4 ). By treating cellulose with 3 equivalents of citric acid (in the presence of DMAP), an increase in the carboxylic acid signal at 1650 cm -1 was monitored by FT-IR, indicating bond formation. Further reaction with EDAC and NHS to activate the carboxylic acid, followed by the addition of collagen, resulted in an increase in the amide signal in the FTIR, confirming the grafting of collagen to the newly formed carboxyl functional groups.

[0172] The citric acid-grafted cellulose has a tendency for the film to become more transparent compared to unmodified cellulose. This may be due to an increase in crosslinking between cellulose fibers imparted by citric acid, resulting in smaller porosity and less light diffraction, and thus a more translucent appearance.

[0173] Embodiment

[0174] The various preferred features and embodiments of the present invention will now be described with reference to the following numbered paragraphs (paragraphs).

[0175] 1. A cellulose graft copolymer comprising polypeptide side chains.

[0176] 2. The cellulose graft copolymer according to paragraph 1, wherein the polypeptide is collagen or a hydrolyzed form thereof.

[0177] 3. The cellulose graft copolymer according to paragraph 1 or 2, wherein the polypeptide side chains are coupled to the cellulose via a linking group, optionally wherein the cellulose graft copolymer has the following formula:

[0178]

[0179] 4. The cellulose graft copolymer according to any one of paragraphs 1 to 3, wherein the polypeptide side chains are coupled to the cellulose via a polycarboxylic acid or its anhydride, optionally wherein the

[0180] cellulose graft copolymer has the following formula:

[0181]

[0182] 5. The cellulose graft copolymer according to any one of paragraphs 1 to 4, wherein the polypeptide side chains are coupled to the cellulose via a tricarboxylic acid or its anhydride, optionally wherein the polypeptide side chains are coupled to the cellulose via a tricarboxylic acid or its anhydride selected from one or more of citric acid, isocitric acid, aconitic acid, or glyceric acid.

[0183] 6. The cellulose graft copolymer according to paragraph 5, wherein the polypeptide side chain is coupled to the cellulose through citric acid or its anhydride, preferably wherein the polypeptide side chain is coupled to the cellulose through citric acid.

[0184] 7. The cellulose graft copolymer according to any one of paragraphs 1 to 4, wherein the polypeptide side chain is coupled to the cellulose through a dicarboxylic acid or its anhydride, optionally wherein the polypeptide side chain is coupled to the cellulose through a dicarboxylic acid or its anhydride selected from one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid or sebacic acid.

[0185] 8. The cellulose graft copolymer according to paragraph 7, wherein the polypeptide side chain is coupled to the cellulose through succinic acid or its anhydride, preferably wherein the polypeptide side chain is coupled to the cellulose through succinic anhydride.

[0186] 9. A method for grafting a polypeptide onto cellulose, the method comprising:

[0187] (a) functionalizing the cellulose with a linking molecule to provide functionalized cellulose; and

[0188] (b) grafting the polypeptide onto the functionalized cellulose to provide a cellulose graft copolymer comprising a polypeptide side chain.

[0189] 10. The method according to paragraph 9, wherein the polypeptide is collagen or a hydrolyzed form thereof.

[0190] 11. The method according to paragraph 9 or 10, wherein the linking molecule is a polycarboxylic acid or its anhydride, optionally wherein the functionalized cellulose has the following formula:

[0191]

[0192] 12. The method according to any one of paragraphs 9 to 11, wherein the linking molecule is a tricarboxylic acid or its anhydride, optionally wherein the linking molecule is a tricarboxylic acid or its anhydride selected from one or more of citric acid, isocitric acid, aconitic acid or glyceric acid.

[0193] 13. The method according to paragraph 12, wherein the linking molecule is citric acid or its anhydride, preferably wherein the linking molecule is citric acid.

[0194] 14. The method according to any one of paragraphs 9 to 11, wherein the linking molecule is a dicarboxylic acid or its anhydride, optionally wherein the linking molecule is a dicarboxylic acid or its anhydride selected from one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid or sebacic acid.

[0195] 15. The method according to paragraph 14, wherein the linking molecule is succinic acid or its anhydride, preferably wherein the linking molecule is succinic anhydride.

[0196] 16. The method according to any one of paragraphs 11 to 15, wherein the polycarboxylic acid or its anhydride is incubated with a nucleophilic catalyst, optionally wherein the nucleophilic catalyst is 4-dimethylaminopyridine (DMAP).

[0197] 17. The method according to any one of paragraphs 11 to 16, wherein the polypeptide chain is grafted onto the functionalized cellulose by a carbodiimide cross-linking reaction.

[0198] 18. The method according to paragraph 17, wherein the carbodiimide cross-linking agent is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDAC), optionally wherein N-hydroxysuccinimide (NHS) is included in the carbodiimide cross-linking reaction.

[0199] 19. A cellulose graft copolymer obtainable or obtained by a method according to any one of paragraphs 9 to 18.

[0200] 20. Functionalized cellulose, wherein the functionalized cellulose is functionalized with a polycarboxylic acid or its anhydride.

[0201] 21. The functionalized cellulose according to paragraph 20, wherein the functionalized cellulose is functionalized with a tricarboxylic acid or its anhydride, optionally wherein the functionalized cellulose is functionalized with a tricarboxylic acid or its anhydride selected from one or more of citric acid, isocitric acid, aconitic acid or glyceric acid, preferably wherein the functionalized cellulose is functionalized with citric acid or its anhydride, more preferably wherein the functionalized cellulose is functionalized with citric acid.

[0202] 22. The functionalized cellulose according to paragraph 20, wherein the functionalized cellulose is functionalized with a dicarboxylic acid or its anhydride, optionally wherein the functionalized cellulose is functionalized with a dicarboxylic acid or its anhydride selected from one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid or sebacic acid, preferably wherein the functionalized cellulose is functionalized with succinic acid or its anhydride, more preferably wherein the functionalized cellulose is functionalized with succinic anhydride.

[0203] 23. A cellulose substrate comprising or consisting of a cellulose graft copolymer according to any one of paragraphs 1 to 8 or paragraph 19.

[0204] 24. The cellulose substrate according to paragraph 23, wherein the cellulose substrate is a paper substrate, a cardboard substrate or a hardboard substrate.

[0205] 25. A packaging material, said packaging material comprising a cellulose graft copolymer according to any one of paragraphs 1 to 8 or paragraph 19 or a cellulose substrate according to paragraph 23 or 24.

[0206] 26. The packaging material according to paragraph 25, wherein the packaging material is a multi-layer metallized paper-based packaging material, preferably wherein the multi-layer metallized paper-based packaging material (1) from its outer side to its inner side comprises:

[0207] (i) A paper layer (2), the grammage of the paper layer being in the range of 30 g / m 2 to 120 g / m 2 ,

[0208] (ii) At least one organic barrier layer (3) of a polymer selected from the list consisting of: polyvinyl alcohol (PVOH), ethylene-vinyl alcohol (EVOH), butanediol-vinyl alcohol copolymer (BVOH) or combinations thereof, the amount of the polymer being 0.5 g / m 2 to 20 g / m 2 , preferably in an amount of 1 g / m 2 to 10 g / m 2 , more preferably in an amount of 2 g / m 2 to 8 g / m 2 ,

[0209] (iii) At least one inorganic barrier layer (4) selected from the list consisting of: metals, metalloids or combinations thereof, the thickness of the inorganic layer being from 1 nm to 100 nm, and

[0210] (iv) At least one organic heat-sealing layer (5) comprising a polymer capable of heat-sealing, the heat-sealing layer (5) being applied in an amount of 2 g / m 2 to 20 g / m 2 , preferably in an amount of 4 g / m 2 to 9 g / m 2 ,

[0211] wherein the paper layer comprises or consists of a cellulose graft copolymer according to any one of paragraphs 1 to 8 or paragraph 19 or a cellulose substrate according to paragraph 23 or 24.

[0212] 27. The multi-layer metallized paper-based packaging material (1) according to paragraph 26, wherein the inorganic layer comprises a metal or metalloid selected from the list consisting of: aluminum, aluminum oxide (AlOx) or silicon oxide (SiOx), and the metal and / or metalloid is deposited by vacuum deposition or transfer metallization.

[0213] 28. The multi-layer metallized paper-based packaging material (1) according to paragraph 26 or 27, wherein the heat-sealing layer comprises an acrylic or methacrylic acid polymer grafted with at least one ionomer, preferably a sodium ionomer.

[0214] 29. The multi-layer metallized paper-based packaging material (1) according to any one of paragraphs 26 to 28, wherein the molecular weight of the acrylic or methacrylic acid polymer grafted with the ionomer is between 85 g / mol and 90 g / mol.

[0215] 30. The multi-layer metallized paper-based packaging material (1) according to any one of paragraphs 26 to 29, wherein each organic layer in the organic layer is deposited onto an adjacent layer by means of an aqueous dispersion or by means of an aqueous solution deposition.

[0216] 31. The multi-layer metallized paper-based packaging material (1) according to any one of paragraphs 26 to 30, wherein the outer surface of the paper layer (2) is covered with an ink layer (6).

[0217] 32. The multi-layer metallized paper-based packaging material (1) according to paragraph 31, wherein the ink layer is selected from the list of the following: water-based ink, solvent-free ink or a combination thereof.

[0218] 33. The multi-layer metallized paper-based packaging material (1) according to paragraph 31 or 32, wherein the outer surface of the paper layer or the ink layer is covered with an overprint varnish (OPV) outermost layer (7).

[0219] 34. The multi-layer metallized paper-based packaging material (1) according to paragraph 33, wherein the overprint varnish outermost layer (7) is a styrene-acrylic varnish.

[0220] 35. The multi-layer metallized paper-based packaging material (1) according to any one of paragraphs 26 to 34, wherein the packaging material has a water vapor transmission rate (WVTR) of less than 0.5 g / m 2 / day (measured at 23 °C, 85% relative humidity) and / or an oxygen transmission rate (OTR) of less than 0.1 cm 3 / m 2 / day / bar (measured at 23 °C, 50% RH).

[0221] 36. The multi-layer metallized paper-based packaging material according to any one of paragraphs 26 to 35, wherein the packaging material has a breaking strain under in-plane tensile load of at most 5% in the longitudinal direction of the paper material and at most 15% in the transverse direction of the paper material.

[0222] 37. Three-dimensional closed packaging article, said three-dimensional closed packaging article being made of a packaging material according to any one of paragraphs 25 to 36, said three-dimensional closed packaging article being obtained by forming, filling with an edible product for human or animal consumption, and then sealing said packaging material.

[0223] 38. Use of a cellulose graft copolymer according to any one of paragraphs 1 to 8 or paragraph 19, a cellulose substrate according to paragraph 23 or 24, or a packaging material according to any one of paragraphs 25 to 36, for packaging an edible product for human or animal consumption.

[0224] 39. Packaged edible product, said packaged edible product comprising a cellulose graft copolymer according to any one of paragraphs 1 to 7 or paragraph 19, a cellulose substrate according to paragraph 23 or 24, or a packaging material according to any one of paragraphs 25 to 36, filled with an edible product for human or animal consumption.

Claims

1. A cellulose substrate, said cellulose substrate comprising or consisting of a cellulose graft copolymer containing polypeptide side chains.

2. The cellulose substrate according to claim 1, wherein the polypeptide is collagen or a hydrolyzed form thereof.

3. The cellulose substrate according to claim 1 or 2, wherein the polypeptide side chains are coupled to the cellulose via a linking group, optionally wherein the cellulose graft copolymer has the following formula:

4. The cellulose substrate according to any of the preceding claims, wherein the polypeptide side chains are coupled to the cellulose via a polycarboxylic acid or its anhydride, optionally wherein the cellulose graft copolymer has the following formula:

5. The cellulose substrate according to any of the preceding claims, wherein the polypeptide side chains are coupled to the cellulose by: (a) a tricarboxylic acid or its anhydride; optionally wherein the tricarboxylic acid or its anhydride is selected from one or more of citric acid, isocitric acid, aconitic acid, or glyceric acid or its anhydride; preferably wherein the tricarboxylic acid or its anhydride is citric acid or its anhydride; more preferably wherein the tricarboxylic acid or anhydride is citric acid; or (b) a dicarboxylic acid or its anhydride; optionally wherein the dicarboxylic acid or its anhydride is selected from one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, or sebacic acid or its anhydride; preferably wherein the dicarboxylic acid or its anhydride is succinic acid or its anhydride; more preferably wherein the dicarboxylic acid or its anhydride is succinic anhydride.

6. A packaging material, said packaging material comprising the cellulose substrate according to any one of claims 1 to 5.

7. The packaging material according to claim 6, wherein the packaging material is a multilayer metallized paper-based packaging material (1), and the multilayer metallized paper-based packaging material comprises, from its outer side to its inner side: (i) A paper layer (2) with a grammage in the range of 30 g / m 2 to 120 g / m 2 wherein the paper layer comprises or consists of a cellulose substrate according to any one of claims 1 to 5, (ii) at least one organic barrier layer (3) of a polymer selected from the list consisting of polyvinyl alcohol (PVOH), ethylene-vinyl alcohol (EVOH), butanediol-vinyl alcohol copolymer (BVOH), or combinations thereof, the amount of the polymer being from 0.5 g / m 2 to 20 g / m 2 , (iii) at least one inorganic barrier layer (4), said at least one inorganic barrier layer being selected from the list consisting of: metals, metalloids, or combinations thereof, and the thickness of the inorganic layer is from 1 nm to 100 nm, and (iv) At least one organic heat-sealing layer (5), said at least one organic heat-sealing layer comprising a polymer capable of heat-sealing, said heat-sealing layer (5) being applied in an amount consisting of an amount from 2 g / m 2 to 20 g / m 2 of the amount applied.

8. The multilayer metallized paper-based packaging material (1) according to claim 7, wherein the inorganic barrier layer comprises a metal or metalloid selected from the list consisting of: aluminum, aluminum oxide (AlOx), or silicon oxide (SiOx), and the metal and / or metalloid is deposited by vacuum deposition or transfer metallization.

9. The multilayer metallized paper-based packaging material (1) according to claim 7 or 8, wherein the organic heat-sealing layer comprises an acrylic or methacrylic acid polymer grafted with at least one ionomer, preferably a sodium ionomer, optionally wherein the molecular weight of the acrylic or methacrylic acid polymer grafted with the ionomer is between 85 g / mol and 90 g / mol.

10. The multilayer metallized paper-based packaging material (1) according to any one of claims 7 to 9, wherein each organic layer in the organic layer is deposited onto an adjacent layer by means of an aqueous dispersion or by aqueous solution deposition.

11. The multi-layer metallized paper-based packaging material (1) according to any one of claims 7 to 10, wherein an ink layer (6) covers the outer surface of the paper layer (2), preferably wherein the ink layer is selected from the list consisting of: water-based ink, solventless ink, or a combination thereof, optionally wherein the outer surface of the paper layer or the ink layer is covered by an overprint varnish (OPV) outermost layer (7), preferably wherein the overprint varnish outermost layer (7) is a styrene acrylic varnish.

12. The multi-layer metallized paper-based packaging material (1) according to any one of claims 7 to 11, wherein the packaging material has: (a) a water vapor transmission rate (WVTR) of less than 0.5 g / m2 / day (measured at 23 °C, 85% relative humidity) and / or an oxygen transmission rate (OTR) of less than 0.1 cm3 / m2 / day / bar (measured at 23 °C, 50% RH); and / or (b) a breaking strain under in-plane tensile load of at most 5% in the longitudinal direction of the paper material and at most 15% in the transverse direction of the paper material.

13. A three-dimensional closed packaging article, the three-dimensional closed packaging article being made of the packaging material according to any one of claims 6 to 12, the three-dimensional closed packaging article being obtained by forming, filling with an edible product for human or animal consumption, and then sealing the packaging material.

14. Use of the cellulose substrate according to any one of claims 1 to 5 or the packaging material according to any one of claims 6 to 12 for packaging an edible product for human or animal consumption.

15. A packaged edible product, the packaged edible product comprising the cellulose substrate according to any one of claims 1 to 5 or the packaging material according to any one of claims 6 to 12 and being filled with an edible product for human or animal consumption.

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