Methods

Abstract

The present invention relates to a method of manufacturing a pellet or film, wherein the pellet or film comprises cutin, and uses thereof in order to replace single-use plastics.

Description

[0001] Methods Field of Invention The present invention relates to a biodegradable product, and methods of producing the same. In particular, the present invention relates to a process for manufacturing a novel pellet or a novel film comprising cutin for a packaging product such as a tray, coffee cup or film. Background of the Invention Single-use plastics (SUPs) are being increasingly used and produced globally, forming an integral part of our daily lives, yet they are responsible for about 150 million tonnes of plastic waste each year worldwide. SUPs are intended to be used once before being thrown away and becoming non-biodegradable waste. Even though a considerable proportion of plastics are recyclable, only an approximate 9% of all plastic is recycled (NRDC, 2020). SUPs are primarily produced from fossil-fuel based chemicals, most commonly for use as packaging, bottles, wrappers, straws, and bags. Of the 91% of unrecycled plastics, over half ends up in landfill waste causing significant damages to the environment, especially to marine ecosystems (National Geographic, 2018). There exists a major problem associated with the difficulty in recycling specific plastics such as thin plastic film and bags used as packaging for consumer products. Considering the continuous increase of plastic waste production, recycling of plastic alone is not a sufficient solution. It is therefore imperative to decrease the usage of fossil fuel-based plastic packaging by developing sustainable bio-based alternatives. Cutin is one of two waxy polymers that are the main components of the plant cuticle, which covers all aerial surfaces of plants. Cutin is a water insoluble substance with waterproof quality. This protective, insoluble barrier prevents plants from water loss and biological attack. Despite its ubiquity in plants, to date, there has been limited uptake of cutin as a feedstock for the production of novel materials, in part due to the difficulty in its extraction and processing. In particular, cutin has not been successfully used before as a plastic replacement, such as to create a film with the suitable mechanical and barrier properties to be used in a biodegradable product, such as a packaging product. The present invention seeks to solve this problem. Summary of the Invention The present invention concerns the production of biodegradable plastics from the renewable source of cutin in order to address the major problems associated with plastic waste pollution. Specifically, the present invention relates to a biodegradable plastic-like material in the form of a pellet or film, and the preparation thereof from cutin, for example, for the manufacture of a solid product, such as a packaging product. The inventors have surprisingly found a method for manufacturing a pellet or film comprising cutin which can be subsequently used to make packaging materials. Despite an entirely plant-derived composition, the pellet or film of the invention match the essential characteristics of bioplastics, such as water-barrier (insolubility), biodegradation, and long-term stability. However, the invention is not a bioplastic because the formulation is derived from a non-chemically modified natural polymer, therefore it falls outside of the EU Single Use Plastic Directive. Due to cutin’s high availability from agricultural waste (such as tomato peel), cutin poses a particularly attractive source for biodegradable plastic production. The intrinsic qualities of cutin provide a renewable source for producing biodegradable plastics that possess the ability to biodegrade much quicker than conventional plastics, while retaining characteristics of traditional plastics. Thus, the use of cutin creates an excellent alternative to SUPs and non-biodegradable or non-recyclable plastics. Furthermore, the barrier properties (particularly water-barrier, e.g., insolubility and hydrophobicity) of cutin differentiates it from other biopolymers and is one of the features that makes it suitable for uses such as packaging. The pellet or film of the present invention may be up to 100% home-compostable. The method of the present invention is environmentally-friendly and cost-effective as cutin can generally be obtained from waste agricultural products. Furthermore, the method is quick, resulting in high throughput. Further, the method of the present invention is more environmentally friendly compared to other processes such as solvent or aqueous-based casting methods, due to lower energy consumption. Importantly, the films of the invention are heat sealable, and so they can be used with the same machinery currently used in the plastic industry. Accordingly, a first aspect of the present invention provides a method of manufacturing a film-coated substrate, comprising the steps of: (i) feeding a composition comprising cutin into an extruder; and (ii) extruding the mixture comprising cutin through a die to obtain a film, wherein the extruding is extrusion coating of the film onto a substrate to obtain the film-coated substrate or the film is laminated onto a substrate to obtain the film-coated substrate. A second aspect provides a film-coated substrate obtainable by the first aspect. A third aspect provides a method of manufacturing a pellet, or film, comprising the steps of: (i) feeding a composition comprising cutin into an extruder; (ii) extruding the mixture comprising cutin through a die to obtain (a) a filament or (b) the film; and (iii) pelletising the filament to obtain the pellet. A fourth aspect of the invention is a pellet or film obtainable by the method of the third aspect of the invention. A fifth aspect of the invention is a pellet or film comprising cutin. A sixth aspect of the invention is a cardboard packaging material comprising a film coating, wherein the film coating comprises cutin and wherein the film coating has been applied onto at least one surface of the cardboard packaging material by extrusion coating or film casting. A seventh aspect of the invention is the use of a film-coated substrate obtained in the first or second aspect, or the pellet or film obtained in the third to fifth aspects, for manufacturing a packaging product. Description of the Figures Fig 1. Cutin pellets created by compounding and filament extrusion. Fig 2. Cutin extrusion coating (1) on board (2) Fig 3. Coffee / drinks cup with cutin interior coating created by extrusion coating Fig 4. Container, bowls, plates produced by extrusion coating on board which is then converted into product shapes Fig 5. Take away container with cutin interior coating created by extrusion coating Fig 6. Cutin film produced by extrusion Fig 7. Cutin container / cup produced by injection moulding using cutin pellets Fig 8. Cutin containers, bowls, plates produced by injection moulding using cutin pellets. Fig 9. Cutin cutlery produced by injection moulding using cutin pellets. Fig 10. Film-coated substrate (3) coated with a cutin first layer (2) and a second layer (1). Fig 11. Film-coated substrate (3) coated with a cutin first layer (2) and a heat-sealable second partial layer (1). Fig 12. Cup produced using the film-coated substrate (3) of Fig 11 which comprises a cutin layer (2) and a heat-sealed partial layer (1). Detailed description of the Invention Unless indicated otherwise, all technical and scientific terms used herein will have their common meaning as understood by one of ordinary skills in the art to which this invention pertains. The term “comprising”, or variants thereof will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. References to “comprising” also encompass providing basis for “consisting”. The term “consisting” or variants thereof is to be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, and the exclusion of any other element, integer or step or group of elements, integers or steps. The term “wt%” is a commonly used abbreviation in the art and refers to the “weight %” with respect to the total weight of the material referred to. Where a numerical range is used, for example, “between 1 wt% and 10 wt%”, the specified end point in the range is included in the claimed amount. Cutin consists of omega hydroxy acids and their derivatives, which are interlinked via ester bonds, forming a polyester polymer of indeterminate size. There are two major monomer families of cutin, the C16 and C18 families. The C16 family consists mainly of 16-hydroxy palmitic acid and 9,16- or 10,16-dihydroxypalmitic acid. The C18 family consists mainly of 18-hydroxy oleic acid, 9,10-epoxy-18-hydroxy stearic acid, and 9,10,18-trihydroxystearate. As used herein, “cutin” refers to the raw material derived from plant cuticle. Cutin may be derived from agricultural waste, such as fruit skin. Specifically, cutin may be extracted from waste tomato peel and is obtained in the extraction of a polyester polymer composed of a complex mixture of interesterified, long-chain ǔ- hydroxy acid with typically the 16- or 18- carbon skeleton. In contrast to many biopolymers, cutin in tomato skin is not well-defined such that its structure varies between different weather conditions and levels of ripeness of a tomato. Suitably, according to the first aspect of the invention, there is provided a method of manufacturing a film-coated substrate, comprising the steps of: (i) feeding a composition comprising cutin into an extruder; and (ii) extruding the mixture comprising cutin through a die to obtain a film, wherein the extruding is extrusion coating of the film onto a substrate to obtain the film-coated substrate or the film is laminated onto a substrate to obtain the film-coated substrate. In some embodiments, the method comprises extrusion coating of the film onto a substrate to obtain the film-coated substrate. In alternative embodiments, the film is laminated onto a substrate to obtain the film- coated substrate (i.e. the method comprises a step of laminating the film onto a substrate to obtain the film-coated substrate). “Lamination” is well known in the field and refers to the process of heat pressing the film onto the substrate. As used herein, “film” includes “coating”, such as coating on a board (e.g. a coating on paperboard or cardboard, which is otherwise referred to as a “film-coated substrate”). In some embodiments, the film is a coating (which is otherwise referred to as “film- coating”). The film of the invention is a bio-friendly alternative to synthetic plastic films and as such does not comprise any plastic (such as non-natural polymers) and is not unnaturally chemically modified. Cutin is also highly abundant in nature. Similarly, the pellet or film and therefore the subsequent products made from them do not comprise any plastic (such as non-natural polymers) and are not chemically modified. Suitably, the cutin may be derived from a terrestrial plant and / or agricultural waste, such as fruit skin preferably from the group consisting of tomato, apple, nectarine, cherry, bananas, watermelon, oranges, grapes, aubergines and carrots, and mixtures of two or more thereof. In preferred embodiments, the cutin is derived from tomato or grapes, most preferably tomato. The skilled person will understand that the following embodiments may be embodiments of both the first, second and third aspects of the invention as appropriate. Without wishing to be bound by theory, it is believed that an effective water barrier may be provided by cutin that is cross-linked solely by “internal” cross linking (i.e. by fully cross linking the functional groups present in the natural cutin polymer). The cutin as found in nature is believed to be fully cross-linked in this manner. The degree of internal cross-linking may be related to the amount of water present in the cutin, such that the smaller the amount of water present in the cutin, the greater the degree of cross-linking. Drying the cutin to remove water is believed to drive the esterification reaction between the functional groups present on the cutin polymer chain (i.e., the cross-linking reaction). Therefore, in some embodiments, cross-linking is achieved by decreasing the amount of water present in the cutin (e.g. in the extracted cutin). In particular embodiments, the method comprises a step of drying the composition comprising cutin and / or the film (such as the film obtained as a film-coating in the first aspect). It is further believed that the degree of cross-linking (and thus the amount of water present in the cutin material) may relate to the thermoplasticity of the cutin. Without wishing to be bound by theory, fully cross-linked cutin (i.e. dry) may behave as a thermoset material, while cutin that is not fully cross-linked (i.e. cutin with a higher water content) may behave as a thermoplastic material. The water content of the cutin may therefore be important for the ease of processing (extrusion) of the cutin material. Furthermore, the water content of the filament, or film is also important because it may affect their tackiness (and the tackiness of the final products, e.g solid products, coatings). Therefore it may be important that the water content of the filament or film is controlled to prevent the material from being too sticky for product use. The water content can be controlled in the filament particularly so that the filament can be pelletised fully for further processing via injection moulding or similar. In some embodiments, in step (i) of the method, the composition comprising cutin comprises between 1 wt% to 50 wt% water, preferably between 1 wt% to 40 wt%, more preferably 1 wt% to 20 wt%, even more preferably between 1 wt% to 10 wt%, yet more preferably 2 wt% to 8 wt%, such as 3 wt% to 7 wt%. Suitably the water content of the film-coating and / or film and / or filament is less than 20 wt%, preferably less than 10 wt%, even more preferably less than 5 wt%, such as less than 4 wt%, 3 wt%, 2 wt%, e.g., less than 1 wt%. Suitably the water content of the film-coating and / or film and / or filament is substantially dry, such as 0 wt% water content. Suitably, the method may further comprise a step (iii) of drying the film-coating and / or film and / or filament until the film-coating and / or film and / or filament comprises less than 10 wt% water, even more preferably less than 5 wt%, such as less than 4 wt%, 3 wt%, 2 wt%, e.g., less than 1 wt% water. Suitably the drying occurs until the water content of the film-coating and / or film and / or filament is substantially dry, such as 0 wt% water content. In some embodiments, the film-coating and / or film and / or filament may be air dried (e.g. with fans or a drying oven). In some embodiments, the film-coating and / or film and / or filament may be dried by lyophilisation. In particular embodiments the drying step comprises heating the film-coating and / or film and / or filament, such as at above 100°C, 120°C or 150°C for at least 5 minutes, such as at least 10 minutes. Suitably, the cutin in the composition is in raw form, i.e., the cutin is not unnaturally chemically modified in the composition or before addition to the composition. No unnatural chemical modification of cutin occurs in the composition between cutin and any other biopolymers that may be present in the composition. I.e., only natural chemical modifications that typically occur in nature may occur in the composition (e.g., such as the cross-linking of the cutin polymer chains described above). The film, pellet or filament of the present invention is manufactured by “extrusion”, which is a well-known manufacturing process for producing parts by forcing a molten polymer into the barrel of an extruder. The process involves feeding a material into a heated single or twin-screw extruder and extruding the resulting molten polymer through an appropriately shaped die to form a film or filament, the filament being then pelletised to form the pellet. Extrusion enables resultant products to be more homogeneous and uniform compared to other manufacturing techniques. An “extruder” is a heated system of barrels and cylinders for the process of extrusion as defined above. Materials are fed into a single-screw or twin-screw barrel through feeders that may be positioned at different points along the barrel. The extruder may involve multiple kneading zones at varying temperatures to accommodate certain materials. A kneading zone comprises kneading screw elements whose main function is mixing and are used for the distribution and dispersion of the materials. At the end of the barrel is a die with the size and shape of the intended final extruded product. The invented method is not restricted to any particular extruder and may be performed using any extruder machine. In some embodiments, the extruder is a single screw extruder. In alternative embodiments, the extruder is a twin screw extruder. A twin screw extruder provides more shear to the formulation, so it is more effective at mixing. The term “pelletisation” is a well-known industry standard and refers to the process of cutting extruded filaments to the shape of a pellet. In the present invention, the filament can be formed by extrusion, by combining materials through heat and shear in the extruder and pushing them through a filament shaped die. The filament is then “pelletised” to form pellets, suitably by cutting or chopping the filament into the desired length pellets. The pelletisation step is necessary in order to obtain pellets of the homogenous material formed by the extrusion step. Pellets are small and thus easily stored and they can be easily utilised in future manufacturing steps to create products. Continuous manufacturing increases the efficiency of the process. The extrusion of the filament may be followed by the downstream pelletisation as part of the same production line. Therefore, in some embodiments, the extrusion and pelletisation steps are a continuous, linear process. In some embodiments, the method of the third aspect of the invention comprises manufacturing a film comprising the steps of: (i) feeding a composition comprising cutin into an extruder; and (ii) extruding the mixture comprising cutin through a die to obtain a film. In such embodiments, the method does not comprise a step of making a pellet. The method of such embodiments is particularly efficient in a continuous manufacturing process, such as part of an in-line process. In particular such embodiments, the extrusion of the mixture (i.e. step (ii)) may comprise extrusion coating onto a substrate (e.g., a board such as paperboard or cardboard) to obtain the film in the form of a coating on the substrate. The skilled person will understand that the “film in the form of a coating on the substrate” may be referred to a “film-coating”, and vice-versa. In alternative embodiments, the method may further comprise a step of laminating the film obtained in step (ii) onto a substrate to obtain the film in the form of a coating on the substrate. Alternatively, the process allows for a modular, flexible approach, in which the extrusion and the pelletisation steps may be separated, so that they are carried out using apparatus that is not necessarily part of the same production line, and / or extrusion and pelletisation are carried out in different locations or at a different time. Therefore, in some embodiments, the extrusion and pelletisation are separate processes. In some embodiments of the third aspect of the invention, the method of manufacturing a pellet comprising the steps of: (i) feeding a composition comprising cutin into an extruder; (ii) extruding the mixture comprising cutin through a die to obtain a filament; and (iii) pelletising the filament to obtain the pellet. In some embodiments, the water content of the pellet is greater than 5 wt%, such as greater than 7 wt%, 10 wt%, 12 wt%, 15 wt%, 20 wt%, 25 wt% or 30 wt%, preferably greater than 7 wt%, more preferably greater than 10 wt%. In some embodiments, the water content of the pellet is less than 20 wt%, preferably less than 10 wt %. In some embodiments, the water content of the pellet is of 2 to 10 wt%, preferably of 3 to 8 wt%, such as of 4 to 6 wt% water. The presence of additional macromolecules, such as polysaccharides, in the film or pellet may be used to alter the properties of the pellet or film, for example to improve the functional properties of the pellet or film, as the formed polymer blend can endow the resultant material with properties intermediate to its constituent components (cutin and polysaccharide). For example, the presence of polysaccharides may improve processing (such as the extrusion steps) or may improve conversion (e.g. conversion of extrusion coated paperboard into a box or other packaging item which may require folding). In the case of the film, the presence of polysaccharides may improve the flexibility of the film. The presence of further biopolymers (i.e. other biopolymers in addition to cutin) may improve the consistency and durability of the material, creating a biopolymer blend. Suitably, the method of the first or third aspects of the invention further comprises the step of feeding a second biopolymer into the extruder. Suitably, the method of the first or third aspects of the invention further comprises the step of feeding a second and a third biopolymer into the extruder. In some embodiments, the second, and where appropriate the third, biopolymer is selected from the group consisting of agar, alginate, carrageenan, cellulose, chitosan, starch, pectin, laminarin, fucoidan, ulvan, pullulan, natural gums, soya protein, pea protein, zein, a vegetable-derived protein, corn gluten meal, corn starch, preferably pectin or agar. In some embodiments, the second, and where appropriate the third, biopolymer may be at least 5 wt% with respect to the total weight of the filament or film, such as at least 7 wt% or 10 wt% with respect to the total weight of the filament or film. For the avoidance of doubt, if drying of the filament is necessary, the biopolymer weight percentage is with respect to the weight of the filament after drying. It is advantageous that films and coatings are heat sealable, as they can be used with the same machinery currently used in the plastic industry. In some embodiments, the film is heat sealable. Seaweed-derived extracts (e.g. agar, carrageenan) may be used to make the film heat sealable. Therefore, in some embodiments, the film of the invention comprises a seaweed-derived extract. A “plasticiser” is an additive that promotes plasticity and flexibility to reduce rigidity of the product and improves workability and processability of the mixture. Plasticisers are generally high boiling point liquids with low molecular weights. The low molecular weight of the plasticiser enables it to occupy intermolecular spaces between polymer chains, reducing secondary forces among them, which reduces the energy required for motion within the molecule and also reduces the hydrogen bonding between the chains. As a result, this increases the free volume of the polymer material and improves the flowability of the polymer, making it easier to use in an extrusion or injection moulding process. The degree of plasticity in a polymer is largely dependent on the chemical structural groups. The type and concentration of plasticiser used can greatly affect the resulting processing characteristics, thermal and mechanical properties of the material and the end product. Plasticisers are essential additives for extruded products as they improve flexibility and handling as well as improving density through the reduction of pores and cracks in the polymer matrix. Suitably, the method of the first and third aspect may comprise feeding a plasticiser into the extruder. In some embodiments, the plasticiser is selected from the group consisting of triacetine, polysorbate, a polyol, monoglycerides (such as glycerol monostearate) and fatty acids (such as oleic acid and stearic acid), citric acid, soy lecithin, glycerol, sodium stearate, agar, carrageenan, pectin, 1,3-butylene glycol, acacia, acetic and fatty acid esters of glycerol, acetone, acetylated distarch adipate, acetylated monoglycerides, starch, agar, alginic acid, alkaline-treated starch, ascorbyl palmitate, ascorbyl stearate, vegetable oil, candelilla wax, carnauba wax, carob bean gum, potassium acetate and mixtures of two or more thereof, preferably triacetine, polysorbate, or a polyol. Suitably, a polyol may be glycerol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and polyethylene glycol, propylene glycol, sorbitol, mannitol, erythritol, maltitol, isomalt, lactitol or xylitol. Most natural plasticisers are hygroscopic and hydrophilic so can affect the resulting barrier properties of the final product by attracting additional water. An amphiphilic plasticizer with both a lipophilic and hydrophilic part can be used to improve the barrier properties and to act as an active interface agent between ingredients. Suitably, in some embodiments, the plasticiser is a monoglyceride (such as glycerol monostearate) or a fatty acid (such as oleic acid or stearic acid). Suitably, the filament, the pellet, film-coating and / or the film comprises less than 40 wt% of plasticiser, such as less than 30 wt%, 25 wt%, 20 wt%, 15 wt%, or 10 wt%. In an embodiment, the filament, the pellet, film-coating and / or the film comprises more than 1 wt% of any plasticiser, such as more than 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or 8 wt%. Preferably the filament, the pellet, film-coating and / or the film comprises more than 3 wt% plasticiser, more preferably more than 5 wt% plasticiser. In some embodiments, the filament, the pellet, film-coating, the film and / or the composition comprising cutin comprises between 1 wt% to 50 wt% plasticiser, preferably between 1 wt% to 40 wt%, more preferably 1 wt% to 20 wt%, even more preferably between 1 wt% to 10 wt%, yet more preferably 2 wt% to 8 wt%, such as 3 wt% to 7 wt%. In some embodiments, the plasticiser content of the film-coating and / or film and / or filament and / or the composition comprising cutin is less than 20 wt%, preferably less than 10 wt%, even more preferably less than 5 wt%, such as less than 4 wt%, 3 wt%, 2 wt%, e.g., less than 1 wt%. Suitably the plasticiser content of the film-coating and / or film and / or filament and / or the composition comprising cutin is substantially 0 wt%. For the avoidance of doubt, any of the aforementioned lower range end-points may be combined with any of the aforementioned upper range end-points. In some embodiments, the weight ratio between cutin and the plasticiser in the filament, the pellet, film-coating and / or the film is at least 2:1, such as at least 3:1 or 4:1. In some embodiments, the weight ratio between cutin and the plasticiser in the filament, the pellet, film-coating and / or the film is less than 6:1 such as less than 5:1. In some embodiments, the film, film-coating and / or filament comprise 5 to 60 wt% plasticiser with respect to the amount of cutin present in the same film, film-coating and / or filament, preferably 10 to 50 wt%, more preferably 10 to 30 wt%. Additives may be incorporated to improve the properties of the material (e.g., pellet or film), such as barrier properties, tensile or flexural strength, processability, cost, sustainability, biodegradability profile. Suitably, the method of the first and third aspects of the invention further comprises the step of feeding one or more additives into the extruder. In some embodiments, the pellet or film or film-coating comprises at least 1 wt% additive, such as at least 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt% or 7 wt%. In some embodiments, the pellet or film comprises less than 40 wt% additive, such as less than 30 wt%, 20 wt%, 15 wt%, 10 wt%. For the avoidance of doubt, any of the aforementioned lower range end-points may be combined with any of the aforementioned upper range end-points. In preferred embodiments, the pellet or film comprises less than 10 wt% additive, such as less than 2 wt%. Additives may be used to reduce the cost of the material or improve performance. Suitable such additives are insoluble fibers. Insoluble fibers include cellulose, hemicellulose, and lignin based fibers. Insoluble fibers further include insoluble fibers of citrus, wheat, oat, vegetable or fruit e.g. pomegranate, pea, tomato, pineapple leaf, potato, onion, grape pomace, apple pomace, olive pomace, almond, cherry stalks, olive stone, bamboo, cellulose, bagasse, seagrass, and seaweed, preferably seaweed (such as dried and milled, added as insoluble powder). The fibers may be milled down to a fine powder or particle size of less than 500 micron. Additives include proteins (such as potato protein, soy protein isolate, sunflower protein isolate, zein, pisumin, albumin, prolamin, globulin, glutenin, amandin, gluten), pectins (such as low methoxy pectin and high methoxy pectins) and natural gums (such as xanthan gum or konjac). These materials may be added as a natural source e.g. derived from waste material dried and milled into a powder or by a refined extract. Filler additives can be incorporated for improved barrier properties and strength. Filler additives include nanocellulose or microcrystalline cellulose, clays including diatomaceous earth, bentonites, kaolin and calcium carbonate. Additives include polysaccharides such as agar, carrageenan, chitosan, starch etc. Polysaccharides may be added as extracts. Additives include hydrophobic materials such as oils or insoluble materials such as lignin, olive stone or fruit pit powders. Hydrophobic materials improve the barrier properties of the material (e.g. film or pellet used to form a moulded product). Emulsifiers such as glycerol monostearate may be incorporated in the material (e.g. film, pellet), particularly in cases where there is a higher hydrophobic or non-water soluble component in the material. Additives such as polyphenols can also be used to improve the barrier properties of polysaccharide based materials as polyphenolic compounds such as green tea extract can form hydrogen bonds with the hydroxyl groups within the polysaccharide to saturate the chains, preventing any further interactions with water, thus improving the water resistance. Lignin or other aromatic compounds can also be added to increase hydrophobicity and improve strength of the material. Tensile strength refers to the amount of load or stress that a material can handle until it stretches and breaks. The film of the invention has good tensile strength properties, to allow for use in consumer products, such as packaging materials which need to be able to withstand a pulling (tensile) force. For example, the film of the invention successfully withstands the tensile force applied by a user when wrapping a product in the film. As a further example, packaging products coated with a film of the invention (such as via extrusion coating) have suitable creasing properties, such that the coating successfully withstands cracking during the conversion process (such as into a box). Additives may also include waxes, rosins, colourants, anti-blocking agents (i.e. anti- sticking agent), or processing aids. Suitably, the additive may be a wax or a rosin which may reduce or increase the pellet or film’s disintegration in water. In some embodiments, the additive is a wax, such as carnauba, bees, sunflower, rice, bran and olive wax. In some embodiments, the additive is a rosin, such as pine or tall-oil rosin. The material (e.g. film, pellet) may be coloured in a range of colours using additives such as natural and artificial colourants and dyes. In some embodiments, the additive is a natural colourant such as chlorophyll (green), carotenoids (yellow, red, orange), flavonoids such as anthocyanins and anthoxantins (red, blue, purple). Cutin commonly contains natural colourants which originate in the plant from which the cutin was obtained and are retained during the extraction of cutin from the bulk lignocellulosic biomass. These colourants are typically terpenes in the carotenoid family such as lycopene, ǃ-carotene or lutein. As such, in some embodiments the method comprises the step of subjecting the extracted cutin to an oxidative bleaching process, such as with hydrogen peroxide, prior to drying, to remove unwanted colour. Any other bleaching process such as alkaline or acidic treatment, oxygen or ozone treatment, enzymatic or variations of sequential bleaching treatments may be used. Anti-blocking agents prevent the layers of film from sticking together when in roll form. In some embodiments, the additive is an anti-blocking agent. In particular embodiments, the anti-blocking agent is calcium carbonate, calcium stearate, magnesium stearate, microfibrillated cellulose, or bamboo fibre. These materials can also be used as a processing aid. Processing aids improve processing and lower the torque during extrusion. In some embodiments, the additive is a processing aid. In particular embodiments, the processing aid is a natural surfactant such as soy lecithin or sunflower lecithin, or citric acid. In some embodiments, the one or more additives comprises a hygroscopic salt. The addition of hygroscopic salts has been found to help keep the film or solid product 'hydrated' in the sense that they absorb moisture and so prevent the product from drying out and becoming too brittle resulting in cracking. In some embodiments, the hygroscopic salt comprises calcium chloride, magnesium chloride, magnesium sulfate, potassium acetate, potassium chloride, potassium sulphate, potassium nitrate, choline chloride, or sodium acetate, preferably calcium chloride, magnesium chloride, magnesium sulfate, potassium acetate or sodium acetate, more preferably potassium acetate. In some embodiments, the pellet and / or filament and / or film comprise 1 to 10 wt% of hygroscopic salt, preferably 1 to 7 wt%, more preferably 2 to 5 wt% hygroscopic salt. Suitably, the composition comprising cutin that is fed into the extruder is dry. Suitably the composition comprising cutin comprises less than 5wt%, preferably less than 4wt%, more preferably less than 3wt%, even more preferably less than 2wt%, yet more preferably less than 1wt%, liquid, such as a solvent and / or water. Suitably the cutin comprises substantially no, such as does not contain any liquid, such as a solvent and / or water. The cutin may be suitable for transportation, storage and use in conventional machinery. Suitably, the method of the first or third aspects further comprises the pre-step of drying the composition comprising cutin before feeding it into the extruder, preferably to achieve the aforementioned amounts of liquid content in the cutin composition. Cutin that is milled to small particles helps improve the mixing and thus the homogeneity of the resulting extruded material. Milling down improves processability and surface area to volume ratio for heating and the subsequent melting / shear processes (e.g. to help the material flow). In addition, if there are any insoluble components in the cutin, they must be small enough so as to not disrupt the mechanical integrity of the final product. Suitably, the method of the first and third aspects further comprises the pre-step of milling down the composition comprising cutin, preferably to an average particle size of smaller than 5 mm, such as smaller than 4 mm, 3 mm, 2 mm, 1 mm or 0.5 mm. Suitably the method comprises both pre-steps of drying and milling down the composition comprising cutin. This process will require drying to remove all water content, mixing and further drying stages. In some embodiments, an automated universal processing system may be used to simultaneously stir and dry the cutin. After drying, the cutin is dry and so can then be milled, such as by feeding the cutin into a universal cutting mill to finally obtain cutin as a dry powder with particle size smaller than 5 mm, such as smaller than 2 mm, preferably smaller than 1 mm or smaller than 0.5 mm. In some embodiments, the filament, the pellet, film-coating and / or the film comprises at least 50 wt% cutin, preferably at least 60 wt% cutin. In some embodiments, the filament, the pellet, film-coating and / or the film comprises between 50 to 90 wt% cutin, preferably 55 to 80 wt% cutin, more preferably 60 to 70 wt%, even more preferably 60 to 65 wt% cutin. The filament and pellets of the present invention may be of many shapes and sizes. However, in order to be suitable for pelletisation, the filament is preferably 1 to 6 mm in diameter, more preferably 2 to 4 mm. As the pellets are formed from the filament, preferably the pellets are also 1 to 6 mm in diameter, more preferably 2 to 4 mm. This size of pellets is particularly suitable for downstream processing, particularly by injection moulding. Pellets inside this range result in better uniformity, fewer blockages and / or better ability to melt properly. The skilled person will recognise that the method of the invention can be used industrially to produce multiple pellets quickly. These may be made in “batches”, such as the machine will run for a pre-determined time, or until a certain number of pellets have been formed. The size and geometry of the pellets are driving factors for how and when a pellet will melt. It is important that the pellets are uniform in size and geometry as any variation can cause different degrees of friction which causes non- uniformity within the polymer melt. In some embodiments, substantially all (more than 90% by weight, often more than 95% by weight, for example more than 98% or 99% by weight) of the pellets produced by the method in a batch are of a size from about 1 to 6 mm, preferably 2 to 4 mm. The films of the invention are effective at encapsulating, protecting and / or preserving consumer or industry products. The films are robust, resistant to splitting and leaking, while being suitably thin. Therefore, in some embodiments, the film has a thickness of 5 to 200 ^m, preferably 20 to 200 ^m, more preferably 30 to 150 ^m, even more preferably 35 to 100 ^m. In some embodiments, the film (e.g., film coating) has a thickness of 5 to 100 ^m, preferably 20 to 100 ^m, more preferably 30 to 80 ^m, even more preferably 35 to 70 ^m, yet more preferably 40 to 60 ^m. Petroleum based materials or chemical modifications to polymers are often included to improve or introduce desired properties such as enhanced barrier performance, thermal stability, biological resistance, mechanical strength, flexibility or rigidity. However, since a majority of petroleum based and / or chemically modified polymers are not naturally occurring, they are non-biodegradable in a home composting environment, and there are concerns around subsequently generated microplastics which are released and could have a detrimental impact on ecosystems. Therefore, in order to obtain home-compostable, truly biodegradable materials and retain reduced environmental damages, the method may comprise feeding into the extruder substantially no, such as none, petroleum derived materials, non-naturally occurring materials and / or chemically modified polymers. In some embodiments, the compositions fed into the extruder comprise less than 5 wt%, preferably less than 3 wt%, more preferably less than 1 wt% of petroleum based, non-naturally occurring, synthetic and / or chemically modified polymers. As such, the pellet and / or film may comprise less than 5 wt%, preferably less than 3 wt%, more preferably less than 1 wt% of petroleum based, synthetic and / or chemically modified polymers. In some embodiments the petroleum based, synthetic, non-naturally occurring and / or chemically modified polymers are selected from the group consisting of PLA, PP, HDPE, LDPE, PVOH, PHB or PVA. PHA and PHB may be considered as naturally occurring biodegradable plastics as they are able to be synthesised by various bacteria. In some embodiments, the method further comprises feeding into the extruder a composition comprising PHA and / or PHB. As such, the pellet and / or film may comprise PHA and / or PHB. In some embodiments, the compositions fed into the extruder comprise less than 10 wt%, preferably less than 5 wt%, preferably less than 3 wt%, more preferably less than 1 wt% of PHA. In some embodiments, the compositions fed into the extruder do not comprise more than 5 wt%, such not more than 3 wt% or 1 wt% of PHB. As such, the pellet and / or film may comprise less than 10 wt%, preferably less than 5 wt%, preferably less than 3 wt%, more preferably less than 1 wt% of PHA and / or PHB. The presence of certain compounds e.g. additives in the composition comprising cutin may affect the cross-linking behaviour of cutin and consequently the water barrier that may result from using that cutin material. In some embodiments, the composition comprising cutin (i.e. in step (i)) comprises less than 10 wt% C4-12 carboxylic acids, such as less than 5 wt%, preferably less than 3 wt%. In some embodiments, the compositions fed into the extruder comprise less than 30 wt% of cellulose, such as less than 20 wt% cellulose, for example less than 10 wt% cellulose. The low water permeability (moisture sensitivity) of the film is advantageous because curling of the film is reduced, enabling it to be used on existing industrial packing machinery in industry. Calendering may be used as a method post extrusion to reduce the thickness of the flat film as it comes out of the extruder. Calendering is a process for creating high- volume, high quality plastic film and sheet. In calendaring, the hot film that comes out of the extruder is further processed using calendaring rolls. The temperature and speed of the rolls influences the properties of the film. This process can enable embossing or improvement to the film by surface treatment. In some embodiments, the method further comprises the step of calendaring the film. In some embodiments of the first and third aspects of the invention, the method further comprises applying a second layer to the film and / or film-coating to obtain the film and / or film-coating comprising a multilayer structure. As used herein, “multilayer” refers to the material being formed of at least two (such as at least three or four) overlaying layers of (the same or different types of) material. In some embodiments, the film and / or film-coating comprising a multilayer structure is a laminated film. In some embodiments, the second layer is a layer of a different material (i.e. different than the composition comprising cutin), such that the resulting film has additional properties, e.g. ability to heat seal or additional barrier or performance properties. Thus, preferably, the second layer is heat-sealable. Preferably the second layer comprises a seaweed extract as defined earlier in the specification. Preferably the seaweed extract is agar or carrageenan. In particular embodiments, the applying of the second layer is by extrusion, such as extrusion coating. In more particular embodiments, the first and second layer are applied onto the substrate by co-extrusion (i.e. the first and second layer are extruded simultaneously) or lamination (i.e. the second layer is applied to the substrate by heat pressing). The skilled person will understand that the “first layer” is the layer comprising cutin. The film may be produced by extruding the composition comprising cutin through an appropriate die, or by extruding the pellet into a film. As such, in some embodiments, the method further comprises the step of extruding the pellet into a film. Extrusion coating refers to the process in which an extruder forces a melted thermoplastic resin through a die onto a moving substrate. The resulting product is a permanently coated structure. Extrusion lamination is a similar process to extrusion coating, where the resin is extruded between two substrates and acts as a bonding agent. Inside an extrusion coating and laminating line, the substrates and melt are nipped at a bonding station. This consists of a large roll, a pressure roll, and a counter-pressure roll cooled by water. The combination of the pressure between the rolls and the temperature permits delivery of the correct adhesion level. The final product is rewound as a permanently bonded multi-ply laminated structure. Suitably the film (e.g. the film of the third aspect or the film obtained by extrusion of the pellet) may be used as a coating, which can be applied to a substrate. Suitably the method further comprises the step of applying the film coating onto a substrate, preferably the substrate is paperboard, carboard, card or paper. Preferably the paperboard, carboard, card or paper substrate is then converted into a packaging product. Suitably, the film may be applied to a substrate by extrusion coating or lamination. The skilled person will understand that lamination refers to application of the film to a substrate using heat pressing. Alternatively, the method may further comprise the step of subjecting the pellet to extrusion coating or film casting (optionally the film casting may be followed by lamination) to apply a film coating onto a substrate, preferably the substrate is paperboard, carboard, card or paper. Preferably the paperboard, carboard, card or paper substrate is then converted into a packaging product. The substrate may be a cutin based substrate, or a substrate made from other natural resources, such as a seaweed based substrate, or another type of substrate. Suitably the packaging product is a cup, tray, box (e.g., a take-away container), or a container. In preferred embodiments, the aforementioned film coating of the invention is for use on a coffee cup. Suitably, the method further comprises the step of applying the film coating on cardboard or paperboard. The method may also comprise the steps of cutting the cardboard or paperboard into cup sidewall blanks, wrapping the blanks into a cup shape, adding a cup bottom, then sealing the seams to form a coffee cup. The pellets of the invention may be converted into solid products that may be used for a variety of purposes, such as packaging. Injection moulding is a standard industrial method commonly used in the plastics processing industry for the mass production of products or parts with complicated shapes e.g. bowls, cutlery, coat hangers, golf tees, disposable razor handles etc. Injection moulding is used to obtain moulded products by injecting plastic materials molten by heat into a mould, followed by a cooling step to form a solid product. There are six major steps in injection moulding: clamping, injection, dwelling, cooling, mould opening and ejection of products from the mould. In each stage of the injection moulding process, the operator can change the temperature or pressure tailor the process so that the material flows appropriately to ensure complete filling of the mould. An injection moulding machine comprises two main parts, an injection unit and a clamping unit. The injection unit melts the plastic by heat and then injects the molten plastic into the mould. A screw is then rotated to melt plastic introduced from the hopper and to accumulate molten plastic in front of the screw (a process called metering). After the required amount of molten plastic is accumulated, the injection process is started. As the molten plastic begins flowing into the mould, the machine controls the moving speed of the screw (called the injection speed). It also controls the dwell pressure after molten plastic fills out cavities. The position of change from speed control to pressure control is set at the point where either the screw position or injection pressure reaches a certain fixed value. Each injection moulding process is tailored to suit the material and the mould, to obtain the desired product shapes. There are two types of blow moulding (via injection and extrusion). Injection blow moulding is used for manufacturing large volumes of hollow parts such as bottles, jars and containers. There are three stages in the process, injection, blowing and ejection. Extrusion blow moulding is a similar process except that the mould for the products is filled with the required amount of molten plastic directly from an extruder. Air is subsequently used to inflate the plastic to the required shape in the same mould. Common materials used are all petrochemical based, non natural materials, including polyethylene (high density, low density and linear low density), polypropylene, polyethylene-terephythalate (PET) and PVC. In some embodiments, the method further comprises the step of moulding the pellet into a solid product, such as by injection moulding, or blow moulding. In some embodiments, the solid product is a packaging product, such as a tray, a film bowl, cup, cutlery, bottle, lid, container, cosmetics tub, electronic housings, or secondary packaging. Preferably the packaging product is used for packaging food or drink. The packaging can be formed through extrusion coating or through film cast extrusion to form a flexible film. Preferably the packaging product comprises coated board that has a Cobb1800 score of less than 20 grams per metre square. Cobb1800 is a water resistance test known to the skilled person in the art. In preferred embodiments, the packaging product comprises coated board that has a COBB water 30 minutes of minimum 8 grams per square metre and maximum 30 grams per square metre, and / or a water vapour transmission rate of maximum 40 g / m2 / day measured at 23 °C and 86 RH. Water vapor transmission rate may be used to assess whether a material is a high barrier material. As used herein, a “high barrier material” is defined as achieving lower than 1 g / m²ڄday for water vapour transmission rate at 37.8 °C and 90% RH. In some embodiments, the packaging product is a high barrier material. In alternative embodiments, the packaging product may offer a medium to low barrier property. The solid product may be thin and flexible, or thicker and rigid, so it is suitable as packaging to protect a variety of products. Suitably, the solid product has a thickness of at least 0.5 mm, such as at least 1 mm, 2 mm, or 3 mm. Suitably, the solid product has a thickness of less than 10 mm, such as less than 9 mm, 8 mm, 7 mm, 6 mm or 5 mm. For the avoidance of doubt, any of the aforementioned lower range end-points may be combined with any of the aforementioned upper range end-points. For the avoidance of doubt, the method of the first aspect of the invention may have any of the features of the third aspect of the invention; and the method of the third aspect of the invention may have any of the features of the first aspect of the invention. According to a second aspect of the invention, there is provided a film-coated substrate obtainable by the first aspect. For the avoidance of doubt, the film-coated substrate of the second aspect may have any of the features of the first aspect of the invention. The skilled person will understand that the film-coated substrate comprises a film obtainable by the first aspect of the invention, which film may be referred to as a “film- coating”. In some embodiments, film-coating of the film-coated substrate is a multilayer, i.e. the film-coating comprises multilayer structure of at least two (such as at least three or four) overlaying layers of (the same or different types of) material. In some embodiments, the film-coating comprising a multilayer structure is a laminated film. In some embodiments, the second layer is a layer of a different material (i.e. different than the composition comprising cutin), such that the resulting film has additional properties, e.g. ability to heat seal or additional barrier properties or functional performance improvements. In more particular embodiments, the second layer only partially overlaps with the first layer (i.e. the second layer is a “partial second layer”). The skilled person will understand that the “first layer” refers to the layer comprising cutin. For example, the partial second layer may be in the form of a strip at one end of the first layer, as shown in Figure 11. The substrate may then be folded so as to join said partial second layer to another section of the substrate to form a seal, such as shown in Figure 12. The seal may be formed by a VFFS (vertical form fill seal) or a HFFS (horizontal form fill seal) process. In particular embodiments, the first layer (i.e. comprising cutin) is directly adjacent to the substrate, and the second layer is on top of the first layer (i.e. the first layer is in between the substrate and the second layer). Preferably, the second layer is heat sealable. In alternative embodiments, the second layer is directly adjacent to the substrate, and the first layer (i.e. comprising cutin) is on top of the second layer (i.e. the second layer is in between the substrate and the first layer). Preferably, the second layer is heat sealable. The second layer may have any of the features defined below for the fifth aspect of the invention. According to a fourth aspect of the invention, there is a pellet, film or solid product obtainable by the method of the third aspect of the invention. For the avoidance of doubt, the pellet, film or solid product of the fourth aspect of the invention may have any of the features of the first or third aspects of the invention. According to a fifth aspect of the invention, there is provided a pellet or a film comprising cutin. For the avoidance of doubt, the pellet or film of the fifth aspect of the invention may have any of the features of the first to fourth aspects of the invention. The film is a bio-friendly alternative to synthetic plastic films and as such is considered as a biodegradable plastic material or a biodegradable plastic film. Similarly, the pellet is considered a biodegradable plastic material and therefore so are the subsequent products made from it. Suitably, the pellet or a film comprising cutin is dry. Suitably the pellet or the film comprising cutin comprises less than 5wt%, preferably less than 4wt%, more preferably less than 3wt%, even more preferably less than 2wt%, yet more preferably less than 1wt%, liquid, such as a solvent and / or water. Suitably the pellet or a film comprising cutin comprises substantially no, such as does not contain any, liquid, such as a solvent and / or water. Suitably, the pellet or film may comprise a monolayer structure. As used herein, “monolayer” refers to the whole material (i.e., the pellet or film) being formed of a single homogenous material, rather than comprising two or more overlaying layers of (the same or different types of) material. Suitably, the pellet or film may comprise a multilayer structure (e.g. the pellet or film comprises at least a first layer and a second layer). As used herein, “multilayer” refers to the material being formed of at least two (such as at least three or four) overlaying layers of (the same or different types of) material. In some embodiments, the film is a multilayer, such as a laminated film. The multilayer film may comprise a layer of a different material (i.e. different than the composition comprising cutin), such that the resulting film has additional properties, e.g. ability to heat seal. Preferably, the different material is extrudable. In particular embodiments, the multilayer film comprises a layer (e.g. a second layer) comprising a seaweed-derived extract, such as agar or carrageenan. The seaweed- derived extracts may be used to impart heat sealing properties to the film. In more particular embodiments, such a film may be used for manufacturing a packaging product, such as a tray, box, or cup. In particular embodiments, the multilayer film comprises a layer (e.g. a second layer) comprising a protein, such as a prolamin protein, such as zein. Prolamins are a group of plant storage proteins having a high proline amino acid content. They are found in plants, mainly in the seeds of cereal grains, such as wheat (gliadin), barley (hordein), rye (secalin), corn (zein), sorghum (kafirin), and oats (avenin). They are characterised by a high glutamine and proline content, and have poor solubility in water. In particular embodiments, the multilayer film comprises a layer (e.g. a second layer) comprising a biopolymer as defined above, such as wherein the biopolymer is selected from the group consisting of agar, alginate, carrageenan, cellulose, chitosan, starch, pectin, laminarin, fucoidan, ulvan, pullulan, natural gums, soya protein, pea protein, zein, a vegetable-derived protein, corn gluten meal, corn starch, preferably pectin or agar. The skilled person will understand that the “first layer” is the layer comprising cutin. The first and / or second layer (and thus the multilayer structure) may have any of the features defined above for the fourth aspect of the invention. According to a sixth aspect of the invention, there is provided a cardboard packaging material comprising a film coating, wherein the film coating comprises cutin and wherein the film coating has been applied onto at least one surface of the cardboard packaging material by extrusion coating or film casting, optionally followed by lamination. Suitably part of or the whole surface is covered. Suitably, a film of the first or third aspects of the invention may be extruded directly onto a cardboard material through an extrusion coating process, leading to cardboard coated with a layer of the film comprising cutin acting as a grease and water barrier. Without wishing to be bound by theory, extruding a composition comprising cutin improves the processability when compared to virgin cutin, enabling the composition to be converted into a pellet or film with suitable barrier and processability properties to be useful as a film or coating on products, such as packaging products. Pelletisation of the filament is necessary to convert the material into a pellet for subsequent processes of injection moulding or blow moulding. A two-step process (pelletisation of a filament, then further extrusion to film formation) provides a homogeneous material with optimum flexible film quality. For the avoidance of doubt, the film coating of the sixth aspect of the invention may have any of the features of the first to fifth aspects of the invention. In the seventh aspect, there is a use of a pellet or film obtained in the first or third aspects or the pellet or film of the second or fourth aspects for manufacturing a packaging product. As appropriate, the packaging product may have any of the properties as described for the first to sixth aspects. Certain embodiments of the invention are provided in the following numbered paragraphs. 1. A method of manufacturing a pellet or film, comprising the steps of: (i) feeding a composition comprising cutin into an extruder; (ii) extruding the mixture comprising cutin through a die to obtain (a) a filament or (b) the film; and (iii) pelletising the filament to obtain the pellet. 2. The method of paragraph 1, wherein the method comprises feeding a biopolymer (agar, alginate, carrageenan, cellulose, chitosan, starch, pectin, pullulan, soya protein, zein, a vegetable proteins) into the extruder. 3. The method of any one of the preceding paragraphs, wherein the method comprises feeding a plasticiser (such as glycerol, sorbitol, xylitol, triacetin, polysorbate, mannitol or a polyol, monoglycerides (such as glycerol monostearate) or fatty acids (such as oleic acid and stearic acid)) into the extruder. 4. The method of any one of the preceding paragraphs, wherein the method comprises feeding a wax (such as carnauba, bees, sunflower, rice, bran and olive wax) or a rosin (such as pine or tall-oil rosin) into the extruder. 5. The method of any one of the preceding paragraphs wherein the method comprises feeding an additive into the extruder. 6. The method of any one of the preceding paragraphs, wherein the method further comprises a pre-step of drying the composition comprising cutin. 7. The method of any one of the preceding paragraphs, wherein the method further comprises a pre-step of milling down the composition comprising cutin, preferably to a particle size less of than 5 mm, such as less than 2 mm. 8. The method of any one of the preceding paragraphs, wherein the filament, the pellet and / or the film comprises at least 60 wt% cutin, preferably at least 70 wt% cutin, more preferably at least 80 wt% cutin. 9. The method of any one of paragraphs 3 to 8, wherein the pellet, filament and / or film comprise 5 to 60 wt% plasticiser, filament and / or coating, preferably 10 to 50 wt%, more preferably 10 to 30 wt%; or the filament, the pellet, and / or the film comprises between 1 wt% to 50 wt% plasticiser, preferably between 1 wt% to 40 wt%, more preferably 1 wt% to 20 wt%, even more preferably between 1 wt% to 10 wt%, yet more preferably 2 wt% to 8 wt%, such as 3 wt% to 7 wt%. 10. The method of any one of the preceding paragraphs, wherein the filament, the pellet and / or the film comprises less than 30 wt% plasticiser, preferably less than 25 wt% plasticiser, more preferably less than 20 wt% plasticiser, such as less than 10 wt% plasticiser, such as less than 5 wt%, such as less than 4 wt%, 3 wt%, 2 wt%, e.g., less than 1 wt%. 11. The method of any one of the preceding paragraphs, wherein the filament, the pellet and / or the film comprises more than 1 wt% plasticiser, preferably more than 3 wt% plasticiser, more preferably more than 5 wt% plasticiser, such as more than 8 wt% plasticiser. 12. The method of any one of the preceding paragraphs wherein the cutin is derived from a terrestrial plant or agricultural waste, such as fruit skin preferably from the group consisting of tomato, apple, nectarine, cherry, bananas, watermelon, oranges, grapes, aubergines and carrots, and mixtures of two or more thereof; preferably, tomato. 13. The method of any one of the preceding paragraphs, wherein the filament or pellet is 1 to 6 mm in diameter, preferably 2 to 4 mm. 14. The method of any one of paragraphs 1 to 12, wherein the film has a thickness of 5 to 200 ^m, preferably 20 to 200 ^m, more preferably 30 to 150 ^m, even more preferably 35 to 100 ^m. 15. The method of any one of paragraphs 1 to 14, wherein the method further comprises the step of subjecting the pellet to extrusion coating or film casting. 16. The method of paragraph 15, wherein the extrusion coating or film casting coats a paperboard, cardboard, card or paper, optionally wherein the paperboard or the cardboard is converted into a packaging material. 17. The method of any one of paragraphs 1 to 13, wherein the method further comprises the step of moulding the pellet into a solid product, such as by injection moulding, or blow moulding. 18. The method of paragraph 17 wherein the solid product is a packaging product, such as a tray, a film, bowl, cup, cutlery, bottle, lid, container, cosmetics tub, electronic housings, or secondary packaging. 19. The method of any one of paragraphs 17 or 18, wherein the solid product has a thickness of between 0.5 mm and 10 mm. 20. The method of any one of any preceding paragraphs, wherein the method further comprises the step of extruding the pellet into a film. 21. A pellet or film or solid product obtainable by the method of any one of the preceding paragraphs. 22. The method of any one of paragraphs 1 to 20, wherein the pellet or film comprises a monolayer structure. 23. A pellet or film comprising cutin. 24. A pellet or film according to paragraph 23, wherein the pellet or film further comprises one or more of a biopolymer, plasticiser, wax, rosin or additive. 25. A pellet or film according to any one of paragraphs 23 or 24, having any one of the features described in paragraphs 8 to 14. 26. A pellet or film according to any one of paragraphs 23 to 25 wherein the pellet or film is dry. 27. A cardboard packaging material comprising a film coating, wherein the film coating comprises cutin and wherein the film coating has been applied onto at least one surface of the cardboard packaging material by extrusion coating or film casting. 28. The film of any one of paragraphs 23 to 26 or cardboard material of paragraph 27, wherein the film or cardboard material can be tuned to be a low to high barrier material. 29. Use of a pellet or film of any preceding paragraph for manufacturing a packaging product. 30. The method of any one of paragraphs 1 to 22, wherein the extruding is extrusion coating of the film onto a substrate to obtain a film-coated substrate or the film is laminated onto a substrate to obtain the film-coated substrate. 31. The method of any one of paragraphs 1 to 22 and 30, wherein in step (i), the composition comprising cutin comprises between 1 wt% to 50 wt% water, preferably between 1 wt% to 40 wt%, more preferably 1 wt% to 20 wt%, even more preferably between 1 wt% to 10 wt%, yet more preferably 2 wt% to 8 wt%, such as 3 wt% to 7 wt%. 32. The method, film, or pellet of any one of paragraphs 1 to 31, wherein the water content of the film-coating and / or film and / or filament is less than 20 wt%, preferably less than 10 wt%, even more preferably less than 5 wt%, such as less than 4 wt%, 3 wt%, 2 wt%, e.g., less than 1 wt%. 33. The method, film, or pellet of any one of paragraphs 1 to 32, wherein the water content of the film-coating and / or film and / or filament is substantially dry, such as 0 wt% water content. 34. The method of any one of paragraphs 1 to 22 and 30 to 33 further comprising a step (iii) of drying the film-coating and / or film and / or filament until the film-coating and / or film and / or filament comprises less than 10 wt% water, even more preferably less than 5 wt%, such as less than 4 wt%, 3 wt%, 2 wt%, e.g., less than 1 wt% water, such as the drying occurs until the water content of the film-coating and / or film and / or filament is substantially dry, such as 0 wt% water content. Examples Example 1 – Extrusion coating of cutin onto a board Cutin which has been extracted from tomatoes in accordance with methods outlined in EP4116352. Cutin was dried under ambient conditions until it contained about 5 wt% water, and was then cut up into pellets. The pellets were fed through an extruder using the following conditions: screw speed = 100 rpm, and at temperatures between 50 to 150 °C. The extruded film was applied directly onto board (simulating extrusion coating). The resulting film-coating had a high contact angle (indicating high water barrier) without any post-processing. In order to further increase the effectiveness of the water barrier, the extrusion coated board was exposed to an additional drying step (10 minutes at elevated temperature (180°C)). An impermeable barrier was then obtained. It is believed that this drying step may fully drive the crosslinking to completion. Example 2 – Preparing pellets and cutin To explore the possible modifications to the properties of the cutin compositions and the subsequently made products, the following examples were developed. Cutin may be derived from a terrestrial plant or agricultural waste (e.g. high cutin bearing plants), such as fruit skin (e.g. tomato, apple, nectarine, cherry, bananas, watermelon, oranges, grapes, aubergines and carrots, and mixtures of two or more thereof). As received from the cutin extraction process (extracted from tomatoes), cutin is dried in several stages, through stages of complete mixing / cutting and drying at high temperatures for several days. The dried cutin is then ground into a smaller particle size (< 1mm) suitable for powder-feeding into an extruder. In the next step, the dried, ground cutin is processed into a film or filament and then pellets using a twin-screw extruder (although other methods of pelletisation such as a pellet mill could also be used). Example 3 – Preparing cutin pellets, extruding to form a film, followed by calendaring (extrusion coating) In this example, a mixture of cutin, plasticisers, blended polymers and additives as described above is processed in a twin-screw extruder into the form of pellets, the pellets are then dried and fed into a single-screw film casting extruder fitted with a slit die. The molten polymer web, extruded from the die is then stretched and pressed using a calendar to afford a thin homogeneous polymer film. Example 4 – Extrusion coating onto a board In another example, the molten polymer web, extruded from the die of Example 3 is pressed using a calendar onto paper / board while still hot, resulting in an extrusion coated board which retains the barrier properties of cutin. Example 5 – Formation of a film, followed by calendaring In this example, a mixture of cutin, plasticisers, blended polymers and additives as described above is processed in a twin-screw extruder directly into a film, as such the molten polymer blend exits the die of the twin screw extruder and is then stretched and pressed using a calendar to afford a thin homogeneous polymer film. Example 6 – Extrusion coating onto a board In another example, the molten polymer web, extruded from the die of Example 5 is pressed using a calendar onto paper / board while still hot, resulting in an extrusion coated board which retains the barrier properties of cutin. The properties of the pellets and / or films of the present invention may be modified such as by the addition of additives (including seaweed-derived extracts) or plasticisers. A few of such modified formulations are exemplified below. Exemplary formulations of Examples 3 to 6:

[0002] Conclusion Pellets and films comprising cutin were obtained by extrusion and pelletising (pellets only). The pellets of the example formulations have also been further extruded into a film, which has further been used as coating on a cardboard packaging product. The films, coatings and solid products have suitable properties (strength, durability, water permeability) for being used as packaging materials.

Claims

Claims 1. A method of manufacturing a film-coated substrate, comprising the steps of: (i) feeding a composition comprising cutin into an extruder; and (ii) extruding the mixture comprising cutin through a die to obtain a film, wherein the extruding is extrusion coating of the film onto a substrate to obtain the film-coated substrate or the film is laminated onto a substrate to obtain the film-coated substrate.

2. The method of claim 1, wherein the water content of the film-coating is less than 10 wt%, preferably less than 5 wt%, such as less than 2 wt% or less than 1 wt%.

3. The method of any one of the claims 1 or 2, wherein the composition comprising cutin comprises between 1 wt% and 20 wt% water, more preferably between 1 wt% and 10 wt%, yet more preferably between 2 wt% and 8 wt%, such as between 3 wt% and 7 wt%.

4. The method of any one of claims 1 or 2, wherein the composition comprising cutin comprises less than 5 wt% water.

5. The method of any one of the preceding claims, wherein the method further comprises a pre-step of drying the composition comprising cutin, preferably the drying is until the water content of the composition comprising cutin is as described in claim 3 or 4.

6. The method of any one of the preceding claims, wherein the method further comprises the post-step (iii) of drying the film-coating, such as until the film-coating comprises less than 3 wt% water, preferably less than 1 wt% water.

7. The method of any one of the preceding claims, wherein the film-coating comprises at least 60 wt% cutin, preferably at least 70 wt% cutin, more preferably at least 80 wt% cutin.

8. The method of any one of the preceding claims, wherein the substrate is paperboard, carboard, card or paper.

9. The method of any one of the preceding claims, wherein the method comprises feeding a biopolymer (agar, alginate, carrageenan, cellulose, chitosan, starch, pectin, pullulan, soya protein, zein, a vegetable proteins) into the extruder.

10. The method of any one of the preceding claims, wherein the method comprises feeding a plasticiser (such as glycerol, sorbitol, xylitol, triacetin, polysorbate, mannitol or a polyol, monoglycerides (such as glycerol monostearate) or fatty acids (such as oleic acid and stearic acid)) into the extruder.

11. The method of any one of the preceding claims, wherein the method comprises feeding a wax (such as carnauba, bees, sunflower, rice, bran and olive wax) or a rosin (such as pine or tall-oil rosin) into the extruder.

12. The method of any one of the preceding claims wherein the method comprises feeding an additive into the extruder.

13. The method of any one of the preceding claims, wherein the method further comprises a pre-step of milling down the composition comprising cutin, preferably to a particle size less of than 5 mm, such as less than 2 mm.

14. The method of any one of claims 10 to 13, wherein the film-coating comprises 5 to 60 wt% plasticiser with respect to the amount of cutin present in the same film and / or film-coating, preferably 10 to 50 wt%, more preferably 10 to 30 wt%.

15. The method of any one of the preceding claims, wherein the film-coating comprises less than 30 wt% plasticiser, preferably less than 25 wt% plasticiser, more preferably less than 20 wt% plasticiser, such as less than 10 wt% plasticiser.

16. The method of any one of the preceding claims, wherein the film-coating comprises more than 1 wt% plasticiser, preferably more than 3 wt% plasticiser, more preferably more than 5 wt% plasticiser, such as more than 8 wt% plasticiser.

17. The method of any one of the preceding claims wherein the cutin is derived from a terrestrial plant or agricultural waste, such as fruit skin preferably from the group consisting of tomato, apple, nectarine, cherry, bananas, watermelon, oranges, grapes, aubergines and carrots, and mixtures of two or more thereof; preferably, tomato.

18. The method of any one of claims 1 to 17, wherein the film-coating has a thickness of 5 to 200 ^m, preferably 30 to 150 ^m, more preferably 35 to 100 ^m.

19. The method of any one of claims 1 to 18, wherein the film-coating comprises a monolayer structure.

20. The method of claim 19, wherein the method further comprises applying a second layer onto the film-coating, preferably wherein the second layer is heat- sealable.

21. The method of any one of the preceding claims, wherein the method further comprises the step of converting the film-coated substrate into a packaging product.

22. The method of claim 21, wherein the packaging product is a cup, tray, box (such as a take-away container), or a container.

23. A film-coated substrate obtainable by the method of any one of claims 1 to 22.

24. A film-coated substrate wherein the film-coating comprises cutin, wherein the film-coating is substantially dry.

25. A film-coated substrate according to claim 24, wherein the film-coating further comprises one or more of a biopolymer, plasticiser, wax, rosin or additive.

26. A film-coated substrate according to any one of claims 24 or 25, having any one of the features described in claims 14 to 18.

27. A cardboard packaging material comprising a film coating, wherein the film coating comprises cutin and wherein the film coating has been applied onto at least one surface of the cardboard packaging material by extrusion coating.

28. The film-coated substrate of any one of claims 24 to 26 or cardboard material of claim 27, wherein the film-coated substrate or cardboard material can be tuned to be a low to high barrier material.

29. Use of a film-coated substrate of any preceding claim for manufacturing a packaging product.

Images