Method for manufacturing conductive graphene-based ink and product thereof

Abstract

The present invention relates to a method for preparing a graphene-based conductive ink for additive manufacturing, which is based on the exfoliation of graphite. The present invention also relates to a graphene-based conductive ink for additive manufacturing, a method for preparing a substrate coated with the conductive ink, and the resulting coated substrate.

Description

Technical Field

[0001] The present invention relates to a method for preparing a graphene-based conductive ink for additive manufacturing, which is based on the exfoliation of graphite. The present invention also relates to a graphene-based conductive ink for additive manufacturing, a method for preparing a substrate coated with the conductive ink, and the resulting coated substrate.

Background Art

[0002] Graphene is a material composed of pure carbon in which carbon atoms are arranged in a flat single layer having a thickness of one atom, whereby the carbon atoms are in an sp 2 hybridized state. This atomic arrangement gives an array of interconnected π-orbitals that is suitable for conducting electrons in a very efficient manner. Graphene is also a light material with good mechanical properties from the viewpoint of mechanical resistance. Graphene is therefore very interesting as a component of materials having applications in conductive materials, lightweight materials and / or mechanically resistant materials. In particular, graphene is considered a promising material for the formulation of conductive inks for use in advanced manufacturing methods. This could enable the reduction of the use of metals in conductive structures, such as printed circuits and microelectronics. Replacing the conductive metal parts in such products with graphene-based materials is attractive for economic, practical and environmental reasons. Next, graphite has a crystalline structure that can be regarded as a multilayer of graphene, whereby these layers interact with each other through electronic interactions via π-orbitals formed by carbon atoms in each layer. Although graphite is abundant and readily available, the benefits from the same mechanical and electronic properties as graphene cannot be obtained. 2

[0003] Methods for preparing graphene are known in the art. For example, graphite can be exfoliated by applying an adhesive tape to graphite and pulling it apart to remove single layers of graphene. Chemical vapor deposition is also known in the art for the production of graphene. While these methods impart high-quality graphene in terms of the thickness of the produced graphene layer, these methods are not sufficiently scalable on an industrial scale. Other methods, such as chemical exfoliation of graphite, have been developed. This method presents the advantage of being scalable at the expense of a reduced quality of the obtained graphene compared to the processes mentioned above. In particular, the exfoliation process is thought to impart high-quality graphene when obtaining the benefit of high conductivity by enabling the production of a material with reduced thickness. Alternative methods are composed of the reduction of graphene oxide. However, this method does not achieve sufficient electrical conductivity under chemical reduction of graphene oxide.

[0004] Methods of chemical graphite exfoliation have been reported in the art. Typically, these methods are carried out in a liquid phase consisting of an organic solvent or water combined with an intercalating agent, also referred to as an exfoliating agent, which is suitable for intercalation into the layers of graphene in graphite and non-covalent interactions with the layers, such as hydrogen bonding, anion-π interactions, cation-π interactions or hydrophobic interactions. These interactions act together to extract the layers of graphene from the graphite material. Such methods typically allow the formation of graphene nanoflakes or nanoplatelets while reducing the conversion of graphite to graphene.

[0005] For example, U.S. Patent Application Publication No. 2015 / 0072162 discloses a method of exfoliating graphite using ethyl cellulose as an exfoliating agent at a weight ratio of 1 to 2 grams of ethyl cellulose to 5 grams of graphite, and using ethyl cellulose at a concentration of 1% to 2% w / v. The disclosed method enables the production of an ink comprising graphene having a low to medium viscosity after repeating a solvent exchange process involving an aqueous solvent several times. An ink for inkjet printing applications is prepared by dissolving the graphene powder from the exfoliation process in an organic solvent. After 10 passes of inkjet printing and annealing at high temperature, a film with a thickness of about 140 nm and a conductivity of about 2.5×10 4 S / m was obtained. According to the authors, this performance level is achieved by the decomposition of ethyl cellulose to aromatic species during the annealing process.

[0006] Carrasco and colleagues reported in Carbon 70, 2014, 157 - 163 a process for graphite exfoliation using cellulose nanocrystals as an exfoliating agent. The developed process uses a weight ratio of cellulose nanocrystals to graphite of 1:1 to 1:20, and an optimal exfoliation yield is obtained at a weight ratio in the range of 1:1 to 1:4. The disclosed method enables the preparation of an aqueous dispersion of graphene flakes at a concentration higher than 1 mg / mL. However, the authors do not mention the use of cellulose nanocrystals in the preparation of inks for advanced shaping techniques.

[0007] Ferreira and colleagues also disclosed in Nanoscale, 2017, 9, 10219-10226 a graphite exfoliation process using cellulose as an exfoliating agent. An aqueous alkaline solution of cellulose was used as a medium for graphite exfoliation using a weight ratio of cellulose to graphite of 2:5 to 5:2. In this case, cellulose was used as an adhesive for the cellulose substrate. Thus, the authors reported the preparation of paper-based electrodes coated with graphene obtained by exfoliation from graphite.

[0008] It is further known in the art that nanocellulose can stabilize a solution or dispersion of a carbonaceous material. In this regard, PCT / EP2021 / 054774 discloses a cellulose composite composition comprising in particular cellulose nanofibers obtained by enzymatic digestion of filter paper and reduced graphene oxide, thereby providing a hybrid material suitable for biocompatible devices. The authors disclose in particular a paper composite material having a conductivity of up to 25 S / m. The above material is prepared by reduction of graphene oxide embedded in a nanocellulose-based paper.

[0009] Liu and colleagues reported in Composites Part B 225(2021) 109250 a process for the exfoliation of oxidized graphite, comprising: (i) preparing low oxidation expanded graphite (LOEG) from graphite; (ii) mixing the LOEG with a slurry of microfibrillated cellulose in an alkaline medium; and (iii) milling the mixture of step (ii) to provide a low oxidation graphene-nanocellulose hybrid material in suspension. In this material, the mass ratio of graphite to microfibrillated cellulose is 2:1. Films were prepared from the suspension obtained by evaporation of the supernatant. The most performant films were reported to have an in-plane conductivity of up to 5800 S / m. However, the disclosed method has the problem of insufficient scalability as a ball milling process is required.

[0010] Xu and colleagues disclosed in Nanoscale 2019, 11, 11719-11729 a method for exfoliating graphite using cellulose nanofibers, comprising blending graphite with cellulose nanofibers at a weight ratio of 1 gram of cellulose nanofibers per 32.8 grams of graphite in a concentration of 1.5 g per liter of water. In particular, the mixture does not comprise any further binder. However, the material prepared from this mixture is described as an insufficient electrical conductor and the disclosed method is described as not being suitable for the preparation of electrically conductive inks. The obtained graphene flakes are mostly formed from multiple graphene layers (about 50% three-layer and 47% multi-layer). These materials are disclosed as being suitable for forming nanopapers useful as moisture-responsive actuators.

[0011] It is derived that there is still a need to provide an improved graphene-based conductive ink suitable for high-precision shaping, as well as its preparation method and use in the preparation of a conductive coating substrate, from what has been disclosed in the art.

Summary of the Invention

[0012] After intensive studies, the inventors have developed a method for preparing a substrate coated with a graphene-based electrical conductor, which comprises a step of reducing the thickness of the coating on the substrate, wherein the coating is the result of a coating step with an ink comprising graphite exfoliated by an exfoliating agent and a binder, thereby leading to the formation of a thin film of the above ink. The inventors have found that the combination of the exfoliating agent and the binder described herein in the graphite-based ink according to the present invention enables a two-step graphite exfoliation process. The first step of graphite exfoliation is promoted by an exfoliating agent in solution and leads to the formation of graphene nanoflakes. As is known in the art, the above graphene nanoflakes are low-conductive materials. The above step of reducing the thickness of the coating comprising the ink is said to promote a second exfoliation step of the graphene nanoflakes formed in solution, which results in an improvement in the conductivity of the film. This second exfoliation step occurs once the ink of the present invention has been transferred onto the surface of the substrate, particularly when the thickness of the resulting coating is reduced in a compression step. The binder comprised in the ink composition is necessary to maintain a coating composition well-adhered to the substrate during this second exfoliation step. In addition, the solvent, the exfoliating agent and the binder are said to interact with each other and with the graphene nanoflakes at the supramolecular level to impart a tacky ink composition having a viscosity sufficient for use in advanced shaping techniques. The method of the present invention requires the use of an ink comprising exfoliated graphite and a binder, whereby the graphite is exfoliated by the intervention of an exfoliating agent selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin and mixtures thereof.The amount of the release agent, and more particularly, the ratio of the release agent to graphite, is an essential feature of the present invention. This is because, on the one hand, an excessive amount of the release agent reduces the conductivity of the final material, and on the other hand, too little amount of the release agent leads to inefficient exfoliation of graphite, resulting in insufficient conductivity. The release agent used in the present invention advantageously further enables the stabilization of graphene nanoflakes and nanoplatelets in the solution formed through the exfoliation of graphite. In addition, the release agent further improves the adhesion of the ink to the substrate. The binder is also an essential aspect of the present invention to ensure the adhesion of the ink to the substrate during the second exfoliation step related to the shear between the graphene platelets formed through the first exfoliation induced by the release agent when the ink is deposited on the substrate. Further reduction of the thickness of the coating formed by the deposited ink as described above provides a highly conductive coating substrate.

[0013] Therefore, in a first aspect, the present invention is a method for manufacturing an ink for forming a conductive coating, comprising: (i) In the step of providing a mixture comprising graphite, a release agent and a first polar solvent: - The release agent is selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin and mixtures thereof; - The weight ratio of the release agent to graphite is configured to be from 1:100 to 1:20 in the above step; (ii) The step of homogenizing the mixture provided in step (i); (iii) In the step of adding a binder different from the release agent to the mixture obtained from step (ii), the binder has a degree of polymerization higher than 5 and (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl and (C 1 -C6 ) Alkyl-CO 2 Selected from the group consisting of polyaniline and water-soluble polysaccharide, which may be substituted at any available position by one or more radicals independently selected from the group consisting of H; the binder is in an amount such that the weight ratio of the binder to the releasing agent is from 4:1 to 1:2. The above step; (iv) Adding a second polar protic solvent having a boiling point equal to or higher than that of the first polar solvent applied in step (i) to the mixture obtained in step (iii); and (v) Substantially removing all of the first polar solvent applied in step (i) while leaving substantially all of the second polar protic solvent added in step (iv). Relates to the above method comprising the same.

[0014] The second aspect of the present invention is, therefore: - Solvent, - A carbonaceous material consisting of one or more of graphene, exfoliated graphite, and a mixture thereof with graphite; - A releasing agent selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin, and mixtures thereof; and - Having a degree of polymerization higher than 5 and (C 1 -C 6 ) Alkyl, (C 1 -C 6 ) Alkylcarbonyl and (C 1 -C 6 ) Alkyl-CO 2 Selected from the group consisting of polyaniline and water-soluble polysaccharide, which may be substituted at any available position by one or more radicals independently selected from the group consisting of H, a binder; An ink composition for forming a conductive coating comprising, wherein the binder and the release agent are different, the release agent is in an amount such that the weight ratio of the release agent to the carbonaceous material is from 1:100 to 1:20, and the binder is in an amount such that the weight ratio of the binder to the release agent is from 4:1 to 1:2. The present invention relates to the above ink composition.

[0015] A third aspect of the present invention relates to an ink composition obtained by the method of the first aspect of the present invention.

[0016] As defined above, the inks of the second and third aspects of the present invention are useful in the preparation of conductive coatings. As a result, a fourth aspect of the present invention is a method for preparing a conductive coating substrate, comprising: (i) providing a substrate for containing a conductive ink for coating; (ii) applying the ink composition defined in the second or third aspect of the present invention; (iii) depositing the ink applied in step (ii) on the substrate applied in step (i); (iv) drying the ink deposited in step (iii) to form a film of the dried ink as described above; (v) reducing the thickness of the film obtained from step (iv) until a film thickness of less than 50% of the film thickness obtained from step (iv) is reached, and optionally repeating steps (iii) to (v) relates to the above method comprising.

[0017] A fifth aspect of the present invention relates to a coating substrate composition obtained by the method of the fourth aspect of the present invention.

[0018] The sixth aspect of the present invention also relates to a coated substrate, wherein the coating comprises a carbonaceous material selected from one or more of graphene, exfoliated graphite, and a mixture thereof with graphite; a release agent selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin, and mixtures thereof; and a binder selected from the group consisting of polyaniline and water-soluble polysaccharide, which may be substituted at any available position by one or more radicals independently selected from the group consisting of (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl, and (C 1 -C 6 ) alkyl-CO 2 H, the binder and the release agent are different, the release agent is in an amount such that the weight ratio of the release agent to the carbonaceous material is from 1:100 to 1:20, and the binder is in an amount such that the weight ratio of the binder to the release agent is from 4:1 to 1:2. BRIEF DESCRIPTION OF THE DRAWINGS

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Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0028] All terms used in this specification in this application shall be understood in their ordinary meaning known in the art, unless otherwise described. Other more detailed definitions for certain terms used in this application are as described below, and are intended to be uniformly applied throughout this specification and the claims, unless a separately and clearly described definition gives a broader definition.

[0029] For the purposes of the present invention, any given range includes both endpoints of the lower and upper limits of that range. A given range, for example, of temperature, time, molar ratio, volume ratio, etc., shall be considered approximate (i.e., having a 5% variation margin around the indicated point), unless otherwise specified.

[0030] The term "polysaccharide" refers to a molecule derived from monosaccharide constituent blocks and comprising a plurality of repeating units connected via glycosidic bonds. The number of monosaccharide repeating units comprised in a polysaccharide compound is also referred to herein as the "degree of polymerization". Examples of polysaccharides include, inter alia, arabinoxylan, carrageenan, cellulose, hemicellulose, chitin, chitosan, alginic acid, alkali salts of alginic acid, pectin, and agarose. In the context of the present invention, it is contemplated that the polysaccharide compound may be functionalized by one or more functional groups such as (C 1 -C 6 )alkyl, (C 1 -C 6 )alkylcarbonyl and (C 1 -C 6 )alkyl-CO 2 OH.

[0031] The term cellulose refers to a homopolymer of β-glucose.

[0032] The three main types of nanocellulose are cellulose nanofibers, cellulose nanocrystals, and bacterial cellulose. Bacterial cellulose can be, for example, the result of the enzymatic digestion of paper using a prototype endoglucanase enzyme, as described in Barruetabena et al. Comm. Chem. 2:76, 2019 (p. 10-11) and Alonso-Lerma et al. Commun. Mater, which are incorporated herein by reference. Bacterial cellulose may consist of a mixture of cellulose nanofibers and cellulose nanocrystals. In the context of the present invention, unless otherwise stated, nanocellulose is a general term comprising cellulose nanofibers, cellulose nanocrystals or a mixture of both.

[0033] However, the terms nanofibrillated cellulose, nanofibrillar cellulose, nanofiber, nanofibril, cellulose nanofibril, and cellulose nanofiber are considered to be used interchangeably in the literature, including as synonyms for microfibrillated cellulose, microfiber, and microfibril (MFC). Cellulose nanofibers are thin fibers that are longer than cellulose nanocrystals and have a length of up to several micrometers. In the context of the present invention, the term "cellulose nanofiber" refers to a fiber of cellulose having a thickness or diameter in the nanometer range of 1 to 1000 nm. Typically, cellulose nanofibers have a length of 1 μm to 10 μm and a diameter (also identified as width) of 5 nm to 60 nm. Cellulose nanofibers have at least a different length-to-width aspect ratio (length / diameter) with respect to cellulose nanocrystals.

[0034] Cellulose nanocrystals (also called cellulose nanocrystals or nanowhiskers) are needle-like crystalline particles having a length of several hundred nanometers depending on the source and isolation process. Cellulose nanocrystals have higher mechanical stability compared to cellulose nanofibers due to their crystalline structure. Cellulose nanocrystals have a high surface area and tensile strength that can be compared to other materials, such as Kevlar or carbon nanotubes. In the context of the present invention, the term "cellulose nanocrystals" refers to cellulose particles having a thickness or diameter in the nanometer range of 1 to 1000 nm and, for non-spherical particles, a length. More specifically, cellulose nanocrystals have an average diameter (also identified as width) between 2 and 60 nm and a length between 10 nm and 2 μm, depending on the cellulose source and isolation process. The diameter and length of cellulose nanocrystals and / or cellulose nanofibers can be calculated, for example, by atomic force microscopy (AFM) using any suitable technique known to those skilled in the art.

[0035] The term "chitin" as used herein refers to a β(1-4) polymer of N-acetyl-D-glucosamine. Chitin is arranged in antiparallel (α), parallel (β) or mixed (γ, two parallel strands alternating with a single antiparallel strand) strands, and is a linear, highly crystalline homopolymer of β-1,4-N-acetylglucosamine (GlcNAc) composed of β-1,4-linked N-acetylglucosamine residues, with the (α) configuration being the most abundant. The repeating unit of chitin is represented by the following formula:

Chemical formula

[0036] In the context of the present invention, the term "chitin nanofiber" refers to a fiber of chitin having a thickness or diameter in the nanometer range of 1 to 1000 nm. Typically, chitin nanofibers have a length of 1 μm to 10 μm and a diameter (also identified as width) of 5 nm to 60 nm. Chitin nanofibers differ at least in terms of the length-to-width aspect ratio (length / diameter) with respect to chitin nanocrystals. In the context of the present invention, the term "chitin nanocrystal" refers to a particle of chitin having a thickness or diameter in the nanometer range of 1 to 1000 nm and, for non-spherical particles, a length. More specifically, chitin nanocrystals have an average diameter (also identified as width) between 2 and 60 nm and a length of 10 nm to 2 μm, depending on the chitin source and the isolation process. The diameter and length of chitin nanocrystals and / or chitin nanofibers can be calculated, for example, by atomic force microscopy (AFM) using any suitable technique known to those skilled in the art. Nanocrystals and nanofibers of chitin may be obtained by enzymatic digestion of chitin, as reviewed by Lin et al “Preparation, properties and applications of polysaccharide Nanocrystals in advanced functional nanomaterials: a review” Nanoscale 4, 3274·3294 (2012).

[0037] In the context of the present invention, the term "lignosulfonate" refers to a sulfonated lignin compound obtained from the production of wood pulp using sulfite pulping. Lignosulfonate is a water-soluble anionic polyelectrolyte polymer having a repeating unit comprising a fragment of the following formula in its molecular formula.

Chemical formula

[0038] In the context of the present invention, the term "hemicellulose" refers to a polysaccharide formed from at least two sugar repeating units linked by β1-4 bonds such as xylose, arabinose, galactose, glucose, glucuronic acid and mannose. Typically, hemicellulose nanofibers have a length of 1 μm to 10 μm and a diameter (also identified as width) of 5 nm to 60 nm. Hemicellulose nanofibers differ at least in length-to-width aspect ratio (length / diameter) with respect to hemicellulose nanocrystals. In the context of the present invention, the term "hemicellulose nanocrystal" refers to a particle of hemicellulose having a thickness or diameter in the nanometer range of 1 to 1000 nm and, for non-spherical particles, a length. More specifically, hemicellulose nanocrystals have an average diameter (also identified as width) between 2 and 60 nm and a length between 10 nm and 2 μm, depending on the hemicellulose source and the isolation process. Hemicellulose nanocrystals and / or hemicellulose nanofibers can be calculated, for example, by atomic force microscopy (AFM) using any suitable technique known to those skilled in the art.

[0039] Arabinoxylan is an example of a hemicellulose compound, which is a polysaccharide comprising a copolymer of arabinose and xylose.

[0040] The term "chitosan", as used herein, relates to a derivative of chitin obtained by deacetylation of chitin in the solid state under alkaline conditions (e.g., concentrated NaOH) or by enzymatic hydrolysis in the presence of chitin deacetylase. This is a randomly distributed β-(1-4)-linked D-glucosamine (deacetylated units) and N-acetyl-D-glucosamine (acetylated units) chain polysaccharide characterized by its average molecular weight and its degree of acetylation (the proportion of acetylated glucosamine units along the polymer backbone). Chitosan is represented by the following general formula:

Chemical formula

[0041] As used herein, the term "lignin" refers to the phenylpropane polymer of monolignol monomers (p-coumaric alcohol, coniferyl alcohol, and sinapyl alcohol) found as an essential part of the secondary cell walls of plants and certain types of algae. Lignin can also refer to natural products, or any lignin derivatives derived from the modification of naturally obtained lignin materials, such as esters, amides, ethers, carboxylic acids and their salts. The term "lignin" can also refer to the alkali salts of the above compounds.

[0042] The term "tannin" is known in the art and refers to large polyphenolic compounds containing hydroxyl and other suitable groups (e.g., carboxyl) sufficient to form strong complexes with various polymers. Tannin may also refer to any tannin derivatives derived from natural products or modification of naturally obtained tannin materials, such as esters, amides, ethers, carboxylic acids and their salts. Exemplary genera of shrubs and / or trees from which suitable tannins can be derived include, but are not limited to, Acacia, Quercus, Senegalia, Momordica, Comptonia, Rubus, Quercus, Synopsis, Tsuga, Nurdia, Juglans, Carya, and Pinus, any combination thereof or any mixture thereof. Suitable tannins include, for example, but not limited to, tannic acid according to CAS number 1401-55-4, and its salts, such as alkali salts.

[0043] Carrageenan is a plant polysaccharide composed of glucose residues linked through β-1,3-linkages and has the following general formula:

Chemical formula

[0044] Alginate is a linear copolymer having homopolymeric blocks of (1→4)-linked β-D-mannuronic acid (M) and α-L-guluronic acid (G) residues covalently linked together in different sequences or blocks. The monomers may be found in homopolymeric blocks of consecutive G-residues (G-blocks), consecutive M-residues (M-blocks) or alternating M and G-residues (MG-blocks). Therefore, alginate has the following general formula:

Chemical formula

[0045] As is known in the art, the term "pectin" refers to a heteropolysaccharide compound known in the art, which is composed mainly of a backbone consisting of optionally esterified D-galacturonic acid in an α1-4 chain configuration and optionally has other sugar compounds as side chains. The acid groups along the chain of D-galacturonic acid repeating units are mostly esterified by methoxy groups in natural products. There may be acetyl groups present on the free hydroxy groups.

[0046] As is known in the art, starch is a polysaccharide comprising glucose monomers joined by α-1,4 linkages. The simplest form of starch is the linear polymer amylose; amylopectin is in a branched form. Typically, starch nanofibers have a length of 1 μm to 10 μm and a diameter (also identified as width) of 5 nm to 60 nm. Starch nanofibers differ at least in the length-to-width aspect ratio (length / diameter) with respect to starch nanocrystals. In the context of the present invention, the term "starch nanocrystal" refers to particles of starch having a thickness or diameter in the nanometer range of 1 to 1000 nm and, for non-spherical particles, a length. More specifically, starch nanocrystals have an average diameter (also identified as width) between 2 and 60 nm and a length of 10 nm to 2 μm, depending on the starch source and the isolation process. Starch nanocrystals and / or starch nanofibers can be calculated, for example, by atomic force microscopy (AFM) using any suitable technique known to those skilled in the art. The starch nanocrystals and nanofibers may be obtained by enzymatic digestion of starch, as reviewed by Lin et al “Preparation, properties and applications of polysaccharide Nanocrystals in advanced functional nanomaterials: a review” Nanoscale 4, 3274·3294 (2012).

[0047] As is known in the art, the term "agarose" refers to a polysaccharide consisting of repeating units of the disaccharide agarobiose, which is a disaccharide composed of D-galactose and 3,6-anhydro-L-galactopyranose of the following formula: [Chemical formula]

[0048] In the context of the present invention, a mixture of components is said to be "homogenized" when the components forming the mixture are substantially equally distributed within the mixture.

[0049] As defined above, a first aspect of the present invention is a method for manufacturing an ink for forming a conductive coating, comprising: (i) In the step of applying a mixture comprising graphite, a delaminating agent and a first polar solvent: - The delaminating agent is selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin and mixtures thereof; - The weight ratio of the delaminating agent to graphite is configured to be from 1:100 to 1:20 in the above step; (ii) The step of homogenizing the mixture applied in step (i); (iii) In the step of adding a binder different from the delaminating agent to the mixture obtained from step (ii), the above binder has a degree of polymerization higher than 5, and (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl and (C 1 -C 6 ) alkyl-CO 2Selected from the group consisting of polyaniline and water-soluble polysaccharide, which may be substituted at any available position by one or more radicals independently selected from the group consisting of H; the binder is in an amount such that the weight ratio of the binder to the release agent is from 4:1 to 1:2 in the above process; (iv) adding to the mixture obtained from step (iii) a second polar proton solvent having a boiling point equal to or higher than that of the first polar solvent imparted in step (i); and (v) substantially removing all of the first polar solvent imparted in step (i) while leaving substantially all of the second polar proton solvent added in step (iv). Relates to the above method comprising the same.

[0050] In a preferred embodiment of the first aspect of the present invention, the first polar solvent of the mixture in step (i) is selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, acetone, methyl ethyl ketone, 3-pentanone, 2-pentanone and mixtures thereof.

[0051] In another preferred embodiment of the first aspect of the present invention, the first polar solvent of the mixture in step (i) is selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, butanol, tert-butanol and mixtures thereof.

[0052] In another more preferred embodiment of the first aspect of the present invention, the first polar solvent is preferably a mixture of water and isopropanol in a volume ratio of 1:1.

[0053] In another preferred embodiment of the first aspect of the present invention, the graphite in the mixture of step (i) is selected from the group consisting of synthetic graphite powder, natural graphite flakes, natural graphite powder and mixtures thereof; preferably synthetic graphite powder.

[0054] In another preferred embodiment of the first aspect of the present invention, the graphite of the mixture in step (i) has a particle size of less than 30 μm.

[0055] In another preferred embodiment of the first aspect of the present invention, the delaminating agent of the mixture in step (i) is selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, and mixtures thereof.

[0056] In another preferred embodiment of the first aspect of the present invention, the delaminating agent of the mixture in step (i) is selected from the group consisting of cellulose nanocrystals, cellulose nanofibers, and mixtures thereof.

[0057] In another preferred embodiment of the first aspect of the present invention, the delaminating agent of the mixture in step (i) is a cellulose nanofiber or cellulose nanocrystal having a length between 100 and 1500 nm and a diameter between 10 and 20 nm.

[0058] In another preferred embodiment of the first aspect of the present invention, the delaminating agent of the mixture in step (i) is obtained by enzymatic digestion of filter paper; preferably, by enzymatic digestion of filter paper mediated by one of endoglucanase, cellobiohydrolase, and β-glucosidase optionally linked to a carbohydrate-binding module; more preferably, by enzymatic digestion of filter paper mediated by an endoglucanase related to the last common ancestor of the phylum Firmicutes optionally linked to a carbohydrate-binding module. Such an enzymatic digestion method is known in the art and is disclosed in Alonso-Lerma, B., Barandiaran, L., Ugarte, L. et al. High performance crystalline nanocellulose using an ancestral endoglucanase. Commun Mater 1, 57 (2020), page 8 (the method section incorporated herein by reference).

[0059] In another preferred embodiment of the first aspect of the present invention, the delayer of the mixture in step (i) is cellulose nanocrystal obtained by acid treatment of cellulose.

[0060] In another preferred embodiment of the first aspect of the present invention, the weight ratio of the delayer to graphite is configured to be 1:90 to 1:30. In certain specific embodiments, the weight ratio of the delayer to graphite is configured to be 1:40 to 1:30, preferably 1:32 to 1:30.

[0061] In another preferred embodiment of the first aspect of the present invention, the delayer has a concentration of 100 mg per liter of solvent to 10 g per liter of solvent in the mixture of step (i); preferably 1 g per liter of solvent to 5 g per liter of solvent. In certain embodiments, the delayer has a concentration of 2 g per liter of solvent to 2.5 g per liter of solvent.

[0062] In another preferred embodiment of the first aspect of the present invention, step (ii) is carried out by mild tank or ultrasonication at the tip or by shear mixing the mixture of step (i).

[0063] In another preferred embodiment of the first aspect of the present invention, step (ii) is carried out by ultrasonication in a mild tank.

[0064] In another preferred embodiment of the first aspect of the present invention, the binder in step (iii) is selected from the group consisting of polyaniline, arabinoxylan, carrageenan, cellulose, chitin, chitosan, alginic acid, alkali salts of alginic acid, pectin, agarose, and mixtures thereof, and the hydroxyl and amino groups available in each of arabinoxylan, carrageenan, cellulose, chitin, chitosan, pectin, and agarose are (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl and (C 1 -C6 ) alkyl-CO 2 Optionally substituted by a radical selected from the group consisting of H.

[0065] In another preferred embodiment of the first aspect of the present invention, the binder in step (iii) is selected from the group consisting of polyaniline, cellulose, chitin, chitosan, alginic acid, alkali salts of alginic acid, agarose and mixtures thereof, and the available hydroxyl and amino groups in each of cellulose, chitin, chitosan and agarose are (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl and (C 1 -C 6 ) alkyl-CO 2 Optionally substituted by a radical selected from the group consisting of H.

[0066] In another preferred embodiment of the first aspect of the present invention, the binder in step (iii) is selected from the group consisting of polyaniline and cellulose in which the available hydroxyl in cellulose is optionally substituted by a radical selected from the group consisting of (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl and (C 1 -C 6 ) alkyl-CO 2 Optionally substituted by a radical selected from the group consisting of H.

[0067] In another preferred embodiment of the first aspect of the present invention, the binder in step (iii) is selected from the group consisting of carboxymethyl cellulose, polyaniline and mixtures thereof; preferably carboxymethyl cellulose. Carboxymethyl cellulose is cellulose in which at least one of the hydroxyl groups of the repeating unit of cellulose is substituted by a -CH 2 CO 2 H group.

[0068] In another preferred embodiment of the first aspect of the present invention, the binder in step (iii) is in an amount such that the weight ratio of the binder to the release agent is 2:1 to 1:2; preferably 3:2 to 2:3.

[0069] In another preferred embodiment of the first aspect of the present invention, the second polar solvent in step (iv) is selected from the group consisting of water, 1,2-propanediol, glycerol, diethylene glycol, 1,2-ethanediol, terpineol, and mixtures thereof.

[0070] In another preferred embodiment of the first aspect of the present invention, the second polar solvent in step (iv) is 1,2-propanediol or water.

[0071] In another preferred embodiment of the first aspect of the present invention, the second polar solvent in step (iv) is 1,2-propanediol.

[0072] In another preferred embodiment of the first aspect of the present invention, the second polar solvent in step (iv) is 1,2-propanediol in an amount such that the volume ratio of 1,2-propanediol to the first polar solvent applied in step (i) is 1:5 to 1:10; preferably 1:8. This advantageously enables the production of inks having a high viscosity.

[0073] In another preferred embodiment of the first aspect of the present invention, the second polar solvent in step (iv) is in an amount such that the volume ratio of the second polar proton solvent to the first polar solvent applied in step (i) is 1:5 to 1:10.

[0074] In another preferred embodiment of the first aspect of the present invention, the second polar solvent in step (iv) and the first polar solvent in step (i) are the same solvent. In such an embodiment, step (v) is a concentration step, and the volume of the solvent remaining after the concentration step is 0.1 to 0.2; preferably 0.125 times the volume of the solvent before step (v).

[0075] In another preferred embodiment of the first aspect of the present invention, step (v) is carried out by heating and / or by applying a vacuum.

[0076] In another preferred embodiment of the first aspect of the present invention, step (v) is carried out by heating at a temperature of 100 °C.

[0077] As defined above, the second aspect of the present invention is: - a solvent, - a carbonaceous material consisting of one or more of graphene, exfoliated graphite and a mixture thereof with graphite; - a release agent selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin and mixtures thereof; and - a binder selected from the group consisting of polyaniline and water-soluble polysaccharides having a degree of polymerization higher than 5 and substituted at any available position by one or more radicals independently selected from the group consisting of (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl and (C 1 -C 6 ) alkyl-CO 2 H, An ink composition for forming a conductive coating comprising: The binder and the release agent are different, the release agent is in an amount such that the weight ratio of the release agent to the carbonaceous material is from 1:100 to 1:20, and the binder is in an amount such that the weight ratio of the binder to the release agent is from 4:1 to 1:2. The present invention relates to the above ink composition.

[0078] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises 85% to 98% by weight of a carbonaceous material, and the percentage by weight is expressed in relation to the total weight of the carbonaceous material, the release agent, and the binder.

[0079] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises 90% to 98% by weight of a carbonaceous material, and the percentage by weight is expressed in relation to the total weight of the carbonaceous material, the release agent, and the binder.

[0080] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises 92% to 98% by weight of a carbonaceous material, and the percentage by weight is expressed in relation to the total weight of the carbonaceous material, the release agent, and the binder.

[0081] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises a solvent that is a polar protic solvent; preferably, the solvent is the solvent S, or an azeotropic mixture of the solvent S and a solvent selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, acetone, methyl ethyl ketone, 3-pentanone, 2-pentanone, and mixtures thereof, and S is selected from the group consisting of water, 1,2-propanediol, glycerol, diethylene glycol, 1,2-ethanediol, terpineol, and mixtures thereof.

[0082] In a more preferred embodiment of the second aspect of the present invention, the ink composition comprises a solvent that is a polar protic solvent; preferably, the solvent is the solvent S, or an azeotropic mixture of the solvent S and a solvent selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, and mixtures thereof, and S is selected from the group consisting of water, 1,2-propanediol, glycerol, diethylene glycol, 1,2-ethanediol, terpineol, and mixtures thereof.

[0083] In a more preferred embodiment of the second aspect of the present invention, the ink composition comprises a solvent which is a polar protic solvent; preferably, the solvent is an azeotropic mixture of solvent S or the solvent S and a solvent which is preferably a mixture of water and isopropanol in a volume ratio of 1:1; S is selected from the group consisting of water, 1,2-propanediol, glycerol, diethylene glycol, 1,2-ethanediol, terpineol, and mixtures thereof.

[0084] In a more preferred embodiment of the second aspect of the present invention, the ink composition comprises a solvent which is a polar protic solvent; preferably, the solvent is an azeotropic mixture of solvent S or the solvent S and a solvent which is preferably a mixture of water and isopropanol in a volume ratio of 1:1; S is 1,2-propanediol.

[0085] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises a solvent which is 1,2-propanediol or an azeotropic mixture thereof with water and / or isopropanol.

[0086] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises a carbonaceous material composed of a mixture of exfoliated graphite and graphite; the graphite is preferably synthetic graphite powder. The carbonaceous material of the ink composition of the second aspect of the present invention is the result of the effect of the exfoliating agent defined in the first aspect of the present invention on the suspension of graphite. When exfoliation is complete, the carbonaceous material of the second aspect of the present invention may consist of graphene flakes, exfoliated graphite, and mixtures thereof. When exfoliation is partial, i.e., when not all of the graphite is exfoliated, the carbonaceous material of the second aspect of the present invention may consist of a mixture of graphite and graphene flakes and / or exfoliated graphite.

[0087] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises a release agent defined in any of the preferred embodiments of the first aspect of the present invention.

[0088] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises a binder defined in any of the preferred embodiments of the first aspect of the present invention.

[0089] In a preferred embodiment of the second aspect of the present invention, the ink composition is configured such that the weight ratio of the release agent to graphite is 1:90 to 1:30. In certain specific embodiments, the weight ratio of the release agent to graphite is configured to be 1:40 to 1:30, preferably 1:32 to 1:30.

[0090] In a preferred embodiment of the second aspect of the present invention, the ink composition is such that the binder is in an amount such that the weight ratio of the binder to the release agent is 2:1 to 1:2; preferably 3:2 to 2:3.

[0091] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises 1% to 4% by weight of the release agent, and the percentage by weight is expressed in relation to the total weight of the carbonaceous material, the release agent, and the binder.

[0092] In a preferred embodiment of the second aspect of the present invention, the ink composition comprises 1% to 6% by weight of the binder, and the percentage by weight is expressed in relation to the total weight of the carbonaceous material, the release agent, and the binder.

[0093] In a preferred embodiment of the second aspect of the present invention, the ink composition has a graphite concentration between 40 and 1000 g per liter of solvent; preferably 60 or 600 g per liter of solvent. In a more preferred embodiment, it is 600 g per liter of solvent.

[0094] Therefore, in a preferred embodiment of the second aspect of the present invention, the ink composition has a kinematic viscosity between 300 and 3000 Pa·s; preferably between 1000 and 1500 Pa·s. This is free in order to enable the use of the ink composition in advanced shaping techniques such as screen printing, syringe extrusion and 3D printing.

[0095] In a more preferred embodiment of the second aspect of the present invention, the ink composition comprises 1,2-propanediol as a solvent, and 93% by weight of graphite, 1.7% by weight of cellulose nanocrystals, 1.6% by weight of polyaniline, 3.7% by weight of carboxymethyl cellulose, preferably consisting of these, and the concentration of graphite is 600 g per liter of solvent. The ink is further referred to as Ink A herein.

[0096] In a more preferred embodiment of the second aspect of the present invention, the ink composition comprises 1,2-propanediol as a solvent, and 94% by weight of graphite, 3% by weight of cellulose nanocrystals obtainable by acid treatment of filter paper, 3% by weight of carboxymethyl cellulose, preferably consisting of these, and the concentration of graphite is 600 g per liter of solvent. The ink is further referred to as Ink C herein.

[0097] In a more preferred embodiment of the second aspect of the present invention, the ink composition comprises 1,2-propanediol or water as a solvent, and 94% by weight of graphite, 3% by weight of cellulose nanocrystals or nanofibers obtainable by enzymatic hydrolysis of filter paper, 3% by weight of carboxymethyl cellulose, preferably consisting of these, and the concentration of graphite is 600 g per liter of solvent. The method for enzymatic hydrolysis of filter paper is known in the art and is defined above in the first aspect of the present invention. The ink is further referred to as Ink E herein when the solvent is 1,2-propanediol. The ink is further referred to as Ink H herein when the solvent is water.

[0098] In a more preferred embodiment of the second aspect of the present invention, the ink composition comprises 1,2-propanediol as a solvent, 96.3% by weight of graphite, 1.8% by weight of cellulose nanocrystals or nanofibers obtainable by enzymatic hydrolysis of filter paper, and 1.9% by weight of carboxymethyl cellulose, preferably consisting of these, and the concentration of graphite is 600 g per liter of solvent. The ink is further referred to herein as Ink J.

[0099] In a more preferred embodiment of the second aspect of the present invention, the ink composition comprises 1,2-propanediol as a solvent, 97.2% by weight of graphite, 1.2% by weight of cellulose nanocrystals or nanofibers obtainable by enzymatic hydrolysis of filter paper, and 1.6% by weight of carboxymethyl cellulose, preferably consisting of these, and the concentration of graphite is 600 g per liter of solvent. The ink is further referred to herein as Ink K.

[0100] As further shown in the following examples, Inks A, C, E, H, J and K are particularly useful in the preparation of conductive coatings.

[0101] As defined above, the third aspect of the present invention relates to a composition obtainable by the first aspect of the method of the present invention.

[0102] The fourth aspect of the present invention is a method for preparing a conductive coating substrate, comprising: (i) providing a substrate for containing a conductive ink for coating; (ii) applying an ink composition defined in any one of the second or third aspects of the present invention; (iii) depositing the ink applied in step (ii) on the substrate applied in step (i); (iv) drying the ink deposited in step (iii) to form a film of the dried ink as described above. (v) Reduce the thickness of the film obtained from step (iv) until it reaches a film thickness of less than 50% of the thickness of the film obtained from step (iv), and optionally repeat steps (iii) to (v). Relates to the above method comprising the same.

[0103] In a preferred embodiment of the fourth aspect of the present invention, the substrate is made from cardboard, paper, cellulose acetate or a plastic material such as polypropylene, polyvinyl chloride, polyacrylonitrile, polyurethane or polyethylene terephthalate.

[0104] In a preferred embodiment of the fourth aspect of the present invention, the thickness of the film produced in step (v) is at least 5 μm; preferably between 10 and 80 μm. As will be described in more detail in the examples below, the thicker the film, the more conductive the coating.

[0105] In a preferred embodiment of the fourth aspect of the present invention, the deposition step (iii) may be carried out by screen printing, ink extrusion, 3D printing or the application of a doctor blade. More preferably, the deposition step is carried out by screen printing technology, such as silk screen printing. As is known in the art, different patterns can be advantageously printed using this technology.

[0106] In a further preferred embodiment of the fourth aspect of the present invention, the deposition step (iii) may be carried out by screen printing using a silk fabric having 43 to 120 threads per cm.

[0107] In a preferred embodiment of the fourth aspect of the present invention, the drying step (iv) is preferably carried out by heating at a temperature above the boiling point of the solvent of the ink applied in step (i). Therefore, when the solvent is 1,2-propanediol, the drying step (iv) may be carried out at a temperature of 150 °C.

[0108] In a preferred embodiment of the fourth aspect of the present invention, the film produced by the drying step (iv) has a thickness exceeding 40 μm.

[0109] In a preferred embodiment of the fourth aspect of the present invention, in step (v), the thickness of the film obtained from step (iv) is reduced until it reaches a film thickness less than 40% of the thickness of the film obtained from step (iv); preferably, the thickness of the film obtained from step (iv) is reduced until it reaches a film thickness less than 30% of the thickness of the film obtained from step (iv). As mentioned above, this step is said to induce a second exfoliation of graphite within the deposited coating by promoting shear between the platelets of exfoliated graphite contained in the ink, leading to an increase in the conductivity of the said coating.

[0110] In a preferred embodiment of the fourth aspect of the present invention, the thickness of the film produced in step (v) is at least 5 μm; preferably between 10 and 80 μm.

[0111] In a preferred embodiment of the fourth aspect of the present invention, step (v) is carried out by subjecting the film of step (iv) to compression rolling. The said compression rolling is preferably carried out at a speed between 1 and 5 cm / second.

[0112] In a preferred embodiment of the fourth aspect of the present invention, the said method comprises a further step (vi) of heating the coated substrate obtained from step (v); preferably at a temperature comprised between 200 °C and 300 °C. The said heating step is preferably carried out for a period of 5 to 10 minutes.

[0113] The fifth aspect of the present invention relates to a coated substrate obtainable by the fourth aspect of the method of the present invention as defined above in any of the preferred embodiments of the fourth aspect.

[0114] In a preferred embodiment of the fifth aspect of the present invention, the coating has a surface resistance of less than 40 Ω / sq; preferably less than 10 Ω / sq; more preferably less than 5 Ω / sq.

[0115] In a preferred embodiment of the fifth aspect of the present invention, the coating has a conductivity of at least 8000 S / m, preferably at least 15000 S / m.

[0116] In a sixth aspect, the present invention relates to a coated substrate, wherein the coating comprises a carbonaceous material selected from one or more of graphene, exfoliated graphite, and mixtures thereof with graphite; a releasing agent selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin, and mixtures thereof; and a binder selected from the group consisting of polyaniline and water-soluble polysaccharides having a degree of polymerization higher than 5 and optionally substituted at any available position by one or more radicals independently selected from the group consisting of (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl, and (C 1 -C 6 ) alkyl-CO 2 H, the binder and the releasing agent being different, the releasing agent being in an amount such that the weight ratio of the releasing agent to the carbonaceous material is from 1:100 to 1:20, and the binder being in an amount such that the weight ratio of the binder to the releasing agent is from 4:1 to 1:2.

[0117] In a preferred embodiment of the sixth aspect, the present invention relates to a coated substrate, wherein the substrate is made of paper or a plastic material. In certain embodiments, the plastic material is polyethylene terephthalate. The substrate is preferably a sheet.

[0118] In a preferred embodiment of the sixth aspect of the present invention, the coating substrate is such that the carbonaceous material is as defined in any of the embodiments of the second aspect of the present invention and / or is present in an amount as defined in any of the embodiments of the second aspect of the present invention.

[0119] In a preferred embodiment of the sixth aspect of the present invention, the coating substrate is such that the release agent is as defined in any of the embodiments of the second aspect of the present invention and / or is present in an amount as defined in any of the embodiments of the second aspect of the present invention.

[0120] In a preferred embodiment of the sixth aspect of the present invention, the coating substrate is such that the binder is as defined in any of the embodiments of the second aspect of the present invention and / or is present in an amount as defined in any of the embodiments of the second aspect of the present invention.

[0121] In a preferred embodiment of the sixth aspect of the present invention, the coating substrate has a coating with a thickness of at least 5 μm; preferably between 10 and 80 μm.

[0122] In a preferred embodiment of the sixth aspect of the present invention, the coating substrate has a surface resistance of less than 40 Ω / sq; preferably less than 10 Ω / sq; more preferably less than 5 Ω / sq.

[0123] In another preferred embodiment of the sixth aspect of the present invention, the coating has a conductivity of at least 8000 S / m, preferably at least 15000 S / m.

[0124] Throughout this specification and the claims, the term "comprising" and variations of the term are not intended to exclude other technical features, additives, components or steps. Further, the term "comprising" encompasses the cases of "consisting of" and "consisting essentially of". Further objects, advantages and features of the present invention will become apparent to those skilled in the art upon practice of this specification, or can be acquired by practice of the present invention. The following examples are given by way of illustration and are not intended to be limiting of the present invention.

Example

[0125] General considerations UV-Vis spectroscopy was performed on a NanoDrop device (Thermo Scientific) in spectrophotometer mode, analyzed in the range of 700 - 200 nm, and the absorbance at 660 nm was measured. Cellulose nanocrystals or nanofibers obtained by enzymatic hydrolysis were prepared by hydrolysis of filter paper using a prototype endoglucanase enzyme using the processes disclosed in Barruetabena et al. Comm. Chem. 2:76, 2019 (p. 10 - 11) and Alonso-Lerma et al. Commun. Mater. 1:57, 2020, which are incorporated herein by reference. Cellulose nanocrystals or nanofibers obtained by acid hydrolysis were prepared by hydrolysis of filter paper using sulfuric acid as disclosed in Composites Science and Technology 92(2014) 27·33, section 2.2 of page 28, which is incorporated herein by reference. Graphite consisted of synthetic graphite powder (CAS: 7782 - 42 - 5, particle size < 30 microns) having a major diffraction peak at 26.6° (at 2θ) and a relative density of 2.2 g / cm 3 3. Silk screen printing device and mesh (Brildor, #43 - #120). The mesh was coated with an azo - sensitized emulsion ink, left to dry for about 30 minutes, and then irradiated with a desired patterned photolite thereon. After irradiating for 15 minutes under a UV lamp (about 1 m below), the mesh was rinsed vigorously with water so that the uncured ink was removed leaving the desired pattern that was not coated. Different graphene inks were applied and spread using a rubber squeegee (75 Shore) to optimize the rheology of the ink and the pattern was retained after application. A commercially available semiconductor characterization instrument (Jandel, Model RM3 - AR) was used in 4 - probe mode either in contact with or indenting into the bulk height of the sample. The surface resistance value (Ω / □) was collected by applying different intensities of current in the range between 10 nA and 50 mA. Measurements were made on the samples with different inks, different printing passes, and different post - treatment conditions (temperature and rolling) as described herein. The viscosity of a representative ink (Ink E) was kinematically measured by measuring the time required for it to flow through a plastic 10 - mL vial having a hole at the bottom and equipped with an mL scale. From these, the flow rate was computer - calculated. This time was compared with the time required for glycerol to flow through the same vial, and the viscosity was estimated as follows:

Number

[0126] Method for the evaluation of release agents by precipitation The efficiency of graphite exfoliation induced by exfoliating agents, such as lignosulfonate and cellulose nanocrystals, was quantitatively determined in a precipitation experiment. In the first step, a suspension of natural graphite flakes with an average width of 500 μm and a concentration of 100 mg per 1 mL of water was prepared. Different amounts of exfoliating agent were added to the divided samples of the above suspension to prepare several graphite suspensions with different exfoliating agent concentrations in the range of 0.1 - 10 mg / mL. The resulting mixtures were sonicated in a water bath for 2 hours and then centrifuged at 100 rcf for 5 minutes. The supernatant was collected and its absorbance at 660 nm was measured. The concentration of exfoliated graphite or graphene in the supernatant was calculated from Lambert-Beer's law on the premise that graphene has a molar extinction coefficient ε of 680 mL·g -1 ·m -1 .

[0127] Figure 2 shows the results of the above measurements using lignosulfonate (top), cellulose nanocrystals (bottom, black squares), or carboxymethyl cellulose (bottom, ● - comparative example) as the exfoliating agent. The results in Figure 2 indicate that both lignosulfonate and cellulose nanocrystals are suitable exfoliating agents as they enable the achievement of concentrations of exfoliated graphite and / or graphene in the range between 0.4 - 0.5 g / l. Next, carboxymethyl cellulose is not a suitable exfoliating agent because the amount of exfoliated graphite and / or graphene in the supernatant decreases dramatically with the increase in the amount of exfoliating agent, especially in the range of 5 - 10 mg / mL.

[0128] General method for ink preparation Method A: One method according to the first aspect of the present invention consists of the following steps: (i) A step of preparing a mixture of a release agent (cellulose nanocrystal CNC or enzyme nanocellulose ENC) shown in Table 1 and synthetic graphite in a 1 / 1 (v / v) mixture of water and isopropanol so that the concentration of graphite becomes a mixture of 75 g / l and the weight ratio of the release agent to graphite is as shown in Table 1; (ii) A step of homogenizing the mixture applied in step (i) by sonication in a water bath for 1 hour; (iii) As shown in Table 1, a step of adding a binder which is carboxymethyl cellulose (CMC) or a mixture of this and polyaniline to the mixture obtained from step (ii) in an amount such that the weight ratio of the binder to graphite is as shown in Table 1; (iv) A step of adding 1,2-propanediol to the mixture obtained from step (iii) in an amount such that the volume ratio of 1,2-propanediol to the mixture of water and isopropanol is 1:8; and (v) In the mixture obtained from step (iv), a step of evaporating water and isopropanol at around 100 °C using gentle magnetic stirring, thereby producing a viscous gray fluid which is the ink according to the present invention.

[0129] General method for the preparation of a coating substrate Method B: One method according to the fourth aspect of the present invention consists of the following steps: (i) A step of providing a substrate for containing a conductive ink for coating, which is one sheet of paper or one sheet of polyethylene terephthalate (PET); (ii) A step of applying the ink composition prepared according to Method A; (iii) In the step of depositing the ink applied in step (ii) on the substrate applied in step (i) by silk screen printing using a #43 mesh; the step in which the mesh has been previously subjected to treatment with a photosensitive ink (Zoicocoat WR, KOPIMASK) and irradiated by photolithography with different printing patterns; (iv) A step of drying the ink deposited in step (iii) by heating at 150 °C to form the film of the dried ink as described above; (v) A step of reducing the thickness of the film obtained from step (iv) by compression rolling using a stainless steel flat roll mill; (vi) Optionally, a step of repeating steps (iii) to (v) - The sequence of steps (iii) to (v) is also referred to as a "printing pass" in this specification; The number of printing passes for each prepared coating substrate is as shown in Table 1, step; (vii) A step of heating the coating substrate obtained in step (vi) at a temperature of 220 to 250 °C for 10 to 15 minutes.

[0130] Method for measuring the thickness of the coating The thickness of the prepared coating was measured by subtracting the thickness of the substrate measured before coating from the thickness of the coated substrate measured using a Mitutoyo (registered trademark) micrometer (HDP356).

[0131] Method for measuring the resistance of the coating substrate For measuring surface resistance (and conductivity), the established four-point method was used on the substrate coated with a circular pattern with a diameter of 30 mm (selected in the printing process of Method B) as shown in Figure 3 (right). The surface resistance measurement was performed in the region near the center of these circles to minimize the influence or strain at the edges when measuring.

[0132] The surface resistance was measured using a commercially available semiconductor characterization instrument with four-point probes, which is specific for the measurement of surface resistance. The measurement was carried out using a wide current range of 1 nA to 70 mA. A value of 10 mA was selected as the reference value for the comparison of resistances between different materials. As a result, all the values in Table 1 are assigned to a current value of 10 mA. The surface resistance values were measured by pressing into the tip (this result closely corresponds to the mass conductivity value of the material) and by making a slight contact between the tip and the surface of the coating. The surface resistance value (R s,c ) obtained by surface contact measurement is substantially lower than the value (R s,i ) obtained by pressing, as can be seen from the values reported in Table 1.

[0133] Using the surface resistance value R s and the thickness t, the conductivity value of the coating was estimated using the relationship: σ (S / m) = 1 / (R s ·t).

[0134] Table 1 below summarizes different ink compositions prepared by Method A, having a graphite concentration of 600 g per liter of solvent, and different paper substrates coated with the above inks by Method B, together with these physical properties.

Table 1

[0135] As will be apparent to those skilled in the art, Ink I does not contain any release agent and is given as a comparative example. The data related to the blank and the aluminum coating are also given as reference examples.

[0136] Discussion of Results The results in Table 1 above show that when Ink I (comparative example without a release agent) is compared with Ink H or Ink J, for example, the combination of ENC and a binder, such as CMC, surprisingly enables the formation of a conductive coating having a lower resistance than a conductive coating prepared according to Method B from an ink comprising only the binder as CMC. The coating obtained from Ink I is slightly conductive as a result of graphite exfoliation caused only by CMC (as shown in FIG. 2, CMC can act as a release agent). Also, the results in FIG. 8 show that a comparative ink formulation comprising graphite and cellulose nanocrystals and / or nanofibers as release agents and instead of a binder is not suitable for the formation of a conductive coating because the formed deposited film does not adhere to the surface substrate. These data indicate that the combination of a release agent and a binder is essential in an ink formulation for forming a conductive coating according to the method of the present invention.

[0137] The results in FIG. 5 show that the step of reducing the thickness of the conductive coating in the method of the present invention (e.g., by compression) enables the production of a coating with reduced resistance. This is evidence that this step causes a second exfoliation process of the ink once deposited on the substrate.

[0138] The results in Table 1 also show that the number of print passes used in the method for preparing the conductive coating enables the production of a film with increased thickness. The data in Table 1 and FIG. 7 show that the resistance of the conductive coating decreases as the film thickness increases. This effect can also be induced from FIG. 7.

[0139] From the comparison of Ink E and Ink H, it can be induced that 1,2-propanediol is more preferred as a solvent than water because it enables the formation of a conductive coating using a similar number of print passes with a lower resistance and thus advantageously using a smaller amount of ink material.

[0140] The results in FIG. 6 show that when using cellulose nanofibers or cellulose nanocrystals obtained by enzymatic digestion of filter paper with a cellulase related to the last common ancestor of the phylum Firmicutes optionally linked to a carbohydrate-binding module as a release agent, in particular when using cellulose nanofibers or cellulose nanocrystals obtained by enzymatic digestion of filter paper mediated by an endoglucanase related to the last common ancestor of the phylum Firmicutes optionally linked to a carbohydrate-binding module, which are prepared from Ink C or Ink E, the resistance of the resulting conductive coating is lower than when cellulose nanofibers and / or nanocrystals prepared by acid treatment of filter paper are used as the release agent. Without being bound by theory, this is thought to be due to the fact that cellulose nanocrystals and / or nanofibers prepared by enzymatic digestion are more hydrophobic than cellulose nanocrystals and / or nanofibers prepared by acid treatment of filter paper because they have a reduced number of charged groups, such as sulfate groups. Item The present invention may also be defined by the following items: 1. A method for producing an ink for forming a conductive coating, comprising: (i) In the step of applying a mixture comprising graphite, a release agent, and a first polar solvent: - The release agent is selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin, and mixtures thereof; - The weight ratio of the release agent to graphite is configured to be 1:100 to 1:20 in the step; (ii) A step of homogenizing the mixture applied in step (i); (iii) In the step of adding a binder different from the release agent to the mixture obtained from step (ii), the binder has a degree of polymerization higher than 5 and (C 1 -C6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl and (C 1 -C 6 ) alkyl-CO 2 selected from the group consisting of polyaniline and water-soluble polysaccharide, optionally substituted at any available position by one or more radicals independently selected from the group consisting of H; the binder is in an amount such that the weight ratio of the binder to the release agent is from 4:1 to 1:2, said step; (iv) adding to the mixture obtained in step (iii) a second polar protonic solvent having a boiling point equal to or higher than that of the first polar solvent applied in step (i), preferably in an amount such that the volume ratio of the second polar protonic solvent to the first polar solvent applied in step (i) is from 1:5 to 1:10; and (v) substantially removing substantially all of the first polar solvent applied in step (i) while leaving substantially all of the second polar protonic solvent added in step (iv). The method comprising the above steps. 2. The method according to item 1, wherein the first solvent of the mixture in step (i) is selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, acetone, methyl ethyl ketone, 3-pentanone, 2-pentanone, and mixtures thereof. 3. The method according to any one of items 1 or 2, wherein the first solvent of the mixture in step (i) is selected from the group consisting of water, methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, and mixtures thereof. 4. The method according to any one of items 1 to 3, wherein the first solvent is preferably a mixture of water and isopropanol at a volume ratio of 1:1. 5. The method according to any one of items 1 to 4, wherein the graphite in the mixture in step (i) is selected from the group consisting of synthetic graphite powder, natural graphite flakes, and natural graphite powder; preferably synthetic graphite powder. 6. The method according to any one of items 1 to 5, wherein the release agent for the mixture in step (i) is selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, and mixtures thereof. 7. The method according to any one of items 1 to 6, wherein the release agent for the mixture in step (i) is cellulose nanocrystals and / or cellulose nanofibers. 8. The method according to any one of items 1 to 7, wherein the release agent for the mixture in step (i) is cellulose nanofibers or cellulose nanocrystals having a length between 100 and 1500 nm and a diameter between 10 and 20 nm. 9. The cellulose nanofibers or cellulose nanocrystals are obtained by enzymatic digestion of filter paper; preferably, by enzymatic digestion of filter paper mediated by one of endoglucanase, cellobiohydrolase, and β-glucosidase optionally linked to a carbohydrate-binding module; more preferably, by enzymatic digestion of filter paper mediated by an endoglucanase related to the last common ancestor of the phylum Firmicutes optionally linked to a carbohydrate-binding module. The method according to item 7 or 8. 10. The method according to any one of items 1 to 7, wherein the release agent for the mixture in step (i) is cellulose nanocrystals obtained by acid treatment of cellulose. 11. The method according to any one of items 1 to 10, wherein the weight ratio of the release agent to graphite is 1:90 to 1:30. 12. The method according to any one of items 1 to 11, wherein the release agent has a concentration of 100 mg per liter of solvent to 10 g per liter of solvent in the mixture in step (i); preferably 1 g per liter of solvent to 5 g per liter of solvent. 13. The method according to any one of items 1 to 12, wherein step (ii) is carried out by mild tank or tip sonication or by shearing and mixing the mixture of step (i) or a combination of both. 14. The binder in step (iii) is selected from the group consisting of polyaniline, arabinoxylan, carrageenan, cellulose, chitin, chitosan, alginic acid, alkali salts of alginic acid, pectin, agarose, and mixtures thereof, and the hydroxyl and amino groups available in each of arabinoxylan, carrageenan, cellulose, chitin, chitosan, pectin, and agarose are optionally substituted by radicals selected from the group consisting of (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl, and (C 1 -C 6 ) alkyl-CO 2 H; preferably, the binder is selected from the group consisting of polyaniline, cellulose, chitin, chitosan, alginic acid, alkali salts of alginic acid, agarose, and mixtures thereof, and the hydroxyl and amino groups available in each of cellulose, chitin, chitosan, and agarose are optionally substituted by radicals selected from the group consisting of (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl, and (C 1 -C 6 ) alkyl-CO 2 H. The method according to any one of items 1 to 13. 15. The method according to any one of items 1 to 14, wherein the binder in step (iii) is selected from the group consisting of polyaniline and cellulose, and the hydroxyl available in cellulose is optionally substituted by radicals selected from the group consisting of (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl, and (C 1 -C 6 ) alkyl-CO 2 H. 16. The method according to any one of items 1 to 15, wherein the binder in step (iii) is selected from the group consisting of carboxymethyl cellulose, polyaniline, and mixtures thereof; preferably carboxymethyl cellulose. 17. The method according to any one of items 1 to 16, wherein the binder in step (iii) is in an amount such that the weight ratio of the binder to the release agent is from 2:1 to 1:2; preferably from 3:2 to 2:3. 18. The method according to any one of items 1 to 17, wherein the second solvent in step (iv) is selected from the group consisting of water, 1,2-propanediol, glycerol, diethylene glycol, 1,2-ethanediol, terpineol, and mixtures thereof. 19. The method according to any one of items 1 to 18, wherein the second solvent in step (iv) is 1,2-propanediol. 20. The method according to any one of items 1 to 19, wherein the second solvent in step (iv) is in an amount such that the volume ratio of 1,2-propanediol to the first polar solvent applied in step (i) is from 1:5 to 1:10; preferably 1:8. 21. The method according to any one of items 1 to 19, wherein step (v) is carried out by heating and / or applying a vacuum. 22 - a solvent, - a carbonaceous material consisting of one or more of graphene, exfoliated graphite, and mixtures thereof with graphite; - a release agent selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin, and mixtures thereof; and - having a degree of polymerization higher than 5, and (C 1 - C 6 ) alkyl, (C 1 - C 6 ) alkylcarbonyl, and (C 1 - C 6 ) alkyl - CO 2A binder selected from the group consisting of polyaniline optionally substituted at any available position by one or more radicals independently selected from the group consisting of H and water-soluble polysaccharides, An ink composition for forming a conductive coating comprising, wherein the binder and the release agent are different, the release agent is in an amount such that the weight ratio of the release agent to the carbonaceous material is from 1:100 to 1:20, and the binder is in an amount such that the weight ratio of the binder to the release agent is from 4:1 to 1:2. The ink composition. 23. The composition according to item 22, comprising 85% to 98% by weight of a carbonaceous material, wherein the percentage by weight is expressed in relation to the sum of the weights of the carbonaceous material, the release agent and the binder. 24. The composition according to item 22, comprising 90% to 98% by weight of a carbonaceous material, wherein the percentage by weight is expressed in relation to the sum of the weights of the carbonaceous material, the release agent and the binder. 25. The composition according to item 22, comprising 92% to 98% by weight of a carbonaceous material, wherein the percentage by weight is expressed in relation to the sum of the weights of the carbonaceous material, the release agent and the binder. 26. The composition according to any one of items 22 to 25, wherein the solvent is a polar protic solvent. 27. The composition according to any one of items 22 to 26, wherein the solvent is solvent S or an azeotropic mixture of solvent S and water as defined in any one of items 2 to 4, and S is selected from the group consisting of water, 1,2-propanediol, glycerol, diethylene glycol, 1,2-ethanediol, terpineol and mixtures thereof. 28. The composition according to any one of items 22 to 27, wherein the solvent is a polar protic solvent which is 1,2-propanediol or an azeotropic mixture thereof with water and / or isopropanol. 29. The composition according to any one of items 22 to 28, wherein the carbonaceous material consists of a mixture of exfoliated graphite and graphite; preferably the graphite is synthetic graphite powder. 30. The composition according to any one of items 22 to 29, wherein the release agent is as defined in any one of items 6 to 10. 31. The composition according to any one of items 22 to 30, wherein the binder is as defined in item 14 or 15. 32. The composition according to any one of items 22 to 31, wherein the weight ratio of the release agent to the graphite is 1:90 to 1:30. 33. The composition according to any one of items 22 to 32, wherein the binder is in an amount such that the weight ratio of the binder to the release agent is 2:1 to 1:2; preferably 3:2 to 2:3. 34. The composition according to any one of items 22 to 33, having a kinematic viscosity between 300 and 3000 Pa·s; preferably between 1000 and 1500 Pa·s. 35. The composition according to any one of items 22 to 34, comprising 1% to 4% by weight of the release agent, the percentage by weight being expressed in relation to the total weight of the carbonaceous material, the release agent and the binder. 36. The composition according to any one of items 22 to 35, comprising 1% to 6% by weight of the binder, the percentage by weight being expressed in relation to the total weight of the carbonaceous material, the release agent and the binder. 37. The composition according to any one of items 22 to 36, wherein the concentration of the graphite is between 40 and 1000 g per liter of solvent; preferably 60 or 600 g per liter of solvent. 38. The composition according to any one of items 22 to 37, comprising 1,2-propanediol as the solvent, and 93% by weight of graphite, 1.6% by weight of cellulose nanocrystals, 1.6% by weight of polyaniline, 3.8% by weight of carboxymethyl cellulose, and the concentration of the graphite is 60 g per liter of solvent. 39. The composition according to any one of items 22 to 37, comprising 1,2-propanediol as the solvent, and 94% by weight of graphite, 3% by weight of the cellulose nanocrystals as defined in item 10, 3% by weight of carboxymethyl cellulose, and the concentration of the graphite is 600 g per liter of solvent. 40. A composition according to any one of items 22 to 37, comprising 1,2-propanediol as a solvent, 94% by weight of graphite, 3% by weight of the cellulose nanofiber defined in item 8 or 9, and 3% by weight of carboxymethyl cellulose, wherein the concentration of the graphite is 600 g per liter of the solvent. 41. A composition according to any one of items 22 to 37, comprising water as a solvent, 94% by weight of graphite, 3% by weight of the cellulose nanofiber defined in item 8 or 9, and 3% by weight of carboxymethyl cellulose, wherein the concentration of the graphite is 600 g per liter of the solvent. 42. A composition according to any one of items 22 to 37, comprising 1,2-propanediol as a solvent, 96.3% by weight of graphite, 1.8% by weight of the cellulose nanofiber defined in item 8 or 9, and 1.9% by weight of carboxymethyl cellulose, wherein the concentration of the graphite is 600 g per liter of the solvent. 43. A composition according to any one of items 22 to 37, comprising 1,2-propanediol as a solvent, 97.2% by weight of graphite, 1.2% by weight of the cellulose nanofiber defined in item 8 or 9, and 1.6% by weight of carboxymethyl cellulose, wherein the concentration of the graphite is 600 g per liter of the solvent. 44. A composition obtainable by the method according to any one of items 1 to 21. 45. A method for preparing a conductive coating substrate, comprising: (viii) a step of providing a substrate for containing a conductive ink for coating; (ix) a step of providing an ink composition defined in any one of items 22 to 42 or 43; (x) a step of depositing the ink applied in step (ii) on the substrate provided in step (i), preferably by inkjet printing, screen printing or syringe extrusion 3D printing; (xi) In step (iii), drying the deposited ink to form a film of the dried ink; preferably, drying the deposited ink by heating; (xii) Reducing the thickness of the film obtained from step (iv) until a film thickness less than 50% of the film thickness obtained from step (iv) is reached, and optionally repeating steps (iii) to (v); preferably by compression rolling. The method comprising the above. 46. The method according to item 45, wherein the substrate is made of paper or a plastic material. 47. The method according to item 45 or 46, wherein the thickness of the film produced in step (v) is at least 5 μm; preferably between 10 and 80 μm. 48. A coated substrate obtainable by the method according to any one of items 45 to 47. 49. The coated substrate according to item 48, wherein the coating has a surface resistance of less than 40 Ω / sq; preferably less than 10 Ω / sq; more preferably less than 5 Ω / sq. 50. The coated substrate according to item 48 or 49, wherein the coating has a conductivity of at least 8000 S / m, preferably at least 15000 S / m. 51. A coated substrate, wherein the coating is a carbonaceous material consisting of one or more of graphene, exfoliated graphite and a mixture thereof with graphite; an exfoliating agent selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin and mixtures thereof; and having a degree of polymerization higher than 5, and (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkylcarbonyl and (C 1 -C 6 ) alkyl-CO 2A binder selected from the group consisting of polyaniline optionally substituted at any available position by one or more radicals independently selected from the group consisting of H and water-soluble polysaccharides comprising, wherein the binder and the release agent are different, the release agent is in an amount such that the weight ratio of the release agent to the carbonaceous material is from 1:100 to 1:20, and the binder is in an amount such that the weight ratio of the binder to the release agent is from 4:1 to 1:2, said coated substrate. 52. The coated substrate according to item 51, wherein the substrate is made of paper or a plastic material. 53. The coated substrate according to item 51 or 52, wherein the carbonaceous material is present in an amount defined in any one of items 23 to 25. 54. The coated substrate according to any one of items 51 to 53, wherein the release agent is as defined in any one of items 6 to 10. 55. The coated substrate according to any one of items 51 to 54, wherein the binder is as defined in item 14 or 15. 56. The coated substrate according to any one of items 51 to 55, wherein the binder is in an amount defined in item 33 or 36. 57. The coated substrate according to any one of items 51 to 56, wherein the release agent is in an amount defined in item 35. 58. The coated substrate according to any one of items 51 to 57, wherein the carbonaceous material, the binder and the release agent are present in an amount defined in any one of items 38 to 43. 59. The coated substrate according to any one of items 51 to 58, wherein the coating has a thickness of at least 5 μm; preferably between 10 and 80 μm. 60. The coated substrate according to any one of items 51 to 59, wherein the coating has a surface resistance of less than 40 Ω / sq; preferably less than 10 Ω / sq; more preferably less than 5 Ω / sq. The coated substrate according to any one of items 51 to 60, wherein the coating has a conductivity of at least 8000 S / m, preferably at least 15000 S / m.

Claims

1. A method for manufacturing an ink for forming a conductive coating, comprising: (i) a step of applying a mixture comprising graphite, a delamination agent, and a first polar solvent, wherein: - the delamination agent is selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin, and mixtures thereof; - the weight ratio of the delamination agent to graphite is configured to be from 1:100 to 1:20, said step; (ii) a step of homogenizing the mixture applied in step (i); (iii) A step of adding a binder different from the release agent to the mixture obtained from step (ii), wherein the binder has a polymerization degree higher than 5 and is selected from the group consisting of polyaniline and water-soluble polysaccharide which may be substituted at any available position by one or more radicals independently selected from the group consisting of (C １ -C ６ ), alkyl, (C １ -C ６ ), alkylcarbonyl and (C １ -C ６ ), alkyl-CO ２ H; and the binder is in an amount such that the weight ratio of the binder to the release agent is from 4:1 to 1:2; said step; (iv) a step of adding a second polar proton solvent having a boiling point equal to or higher than that of the first polar solvent applied in step (i) to the mixture obtained from step (iii); and (v) a step of removing substantially all of the first polar solvent applied in step (i) while leaving substantially all of the second polar proton solvent added in step (iv). The method comprising the above steps.

2. The method according to claim 1, wherein the first polar solvent of the mixture in step (i) is a mixture of water and isopropanol in a volume ratio of 1:

1.

3. The method according to claim 1 or 2, wherein the delamination agent is selected from the group consisting of lignosulfonate, cellulose nanocrystals, and cellulose nanofibers, and the cellulose nanofibers or cellulose nanocrystals are obtained by enzymatic digestion of filter paper mediated by endoglucanase.

4. The method according to any one of claims 1 to 3, wherein the weight ratio of the delamination agent to graphite is configured to be from 1:90 to 1:

30.

5. The method according to any one of claims 1 to 4, wherein step (ii) is carried out by mild tank or tip sonication or by shear mixing the mixture of step (i).

6. The method according to any one of claims 1 to 5, wherein the binder in step (iii) is selected from the group consisting of carboxymethyl cellulose, polyaniline, and mixtures thereof.

7. The method according to any one of claims 1 to 6, wherein the second solvent in step (iv) is 1,2-propanediol.

8. - a solvent, - A carbonaceous material consisting of one or more of graphene, exfoliated graphite, and a mixture thereof with graphite; - A releasing agent selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, optionally sulfonated tannins, and mixtures thereof; and - having a degree of polymerization higher than 5 and being substituted at any available position by one or more radicals independently selected from the group consisting of (C １ -C ６ ), alkyl, (C １ -C ６ ), alkylcarbonyl and (C １ -C ６ ), alkyl-CO ２ H, a binder selected from the group consisting of polyaniline and water-soluble polysaccharide which may be substituted An ink composition for forming a conductive coating comprising: wherein the binder and the releasing agent are different, the releasing agent is in an amount such that the weight ratio of the releasing agent to the carbonaceous material is from 1:100 to 1:20, and the binder is in an amount such that the weight ratio of the binder to the releasing agent is from 4:1 to 1:2, said ink composition.

9. The composition according to claim 8, comprising 85% to 98% by weight of said carbonaceous material, the percentage by weight being expressed in relation to the sum of the weights of said carbonaceous material, said releasing agent, and said binder.

10. The composition according to claim 8 or 9, wherein the solvent is 1,2-propanediol or an azeotropic mixture thereof with water and / or isopropanol.

11. The composition according to any one of claims 8 to 10, having a kinematic viscosity of 1000 to 1500 Pa·s.

12. The composition according to any one of claims 8 to 11, comprising 90% to 98% by weight of said carbonaceous material, 1% to 4% by weight of said releasing agent, and 1% to 6% by weight of said binder, the percentage by weight being expressed in relation to the sum of the weights of said carbonaceous material, said releasing agent, and said binder.

13. A composition obtainable by the method according to any one of claims 1 to 7.

14. A method for preparing a conductive coating substrate, comprising: (vi) providing a substrate for containing a conductive ink for coating; (vii) applying the ink composition according to any one of claims 8 to 12 or 13; (viii) depositing the ink applied in step (ii) on the substrate applied in step (i); (ix) drying the deposited ink in step (iii) to form a film of the dried ink. Reducing the thickness of the film obtained from step (x)(iv) until reaching a film thickness of less than 50% of the thickness of the film obtained from step (iv), and optionally repeating steps (iii) to (v). The method comprising the above steps.

15. A coated substrate obtainable by the method according to claim 14.

16. A coating substrate, wherein the coating comprises a carbonaceous material consisting of one or more of graphene, exfoliated graphite, and a mixture thereof with graphite; a releasing agent selected from the group consisting of lignosulfonate, cellulose nanocrystals, cellulose nanofibers, chitin nanocrystals, chitin nanofibers, hemicellulose nanocrystals, hemicellulose nanofibers, starch nanocrystals, starch nanofibers, lignin, tannin, and mixtures thereof; and a binder selected from the group consisting of polyaniline and water-soluble polysaccharides, which may be substituted at any available position by one or more radicals independently selected from the group consisting of (C １ -C ６ ), alkyl, (C １ -C ６ ), alkylcarbonyl, and (C １ -C ６ ), alkyl-CO ２ H, the binder and the releasing agent being different, the releasing agent being in an amount such that the weight ratio of the releasing agent to the carbonaceous material is from 1:100 to 1:20, and the binder being in an amount such that the weight ratio of the binder to the releasing agent is from 4:1 to 1:2, said coating substrate.

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