METHOD FOR OBTAINING A LIGNO-CELLULOSIC COMPOSITE MATERIAL AND THE COMPOSITE MATERIAL OBTAINED BY THIS METHOD

Abstract

The present invention relates to a method for obtaining a ligno-cellulosic composite material, a ligno-cellulosic composite material that can be obtained by this method, and the use of this ligno-cellulosic composite material.

Description

Title of the invention: METHOD FOR OBTAINING A LIGNO-CELLULOSIC COMPOSITE MATERIAL AND THE COMPOSITE MATERIAL OBTAINED BY THIS METHOD FIELD OF INVENTION

[0001] The present invention relates to a method for obtaining a lignocellulosic composite material, a lignocellulosic composite material obtainable by this method, and the use of this lignocellulosic composite material. TECHNICAL BACKGROUND

[0002] The flexible materials currently in use are produced through highly polluting chemical and physical processes. The flexible plastics industry relies primarily on petroleum-based resources such as polyvinyl chloride (PVC) or polyesters, while the textile and leather industries rely on potentially lengthy and polluting transformation processes such as tanning in baths of chromium-based compound solutions. The main advantage of these materials is their biaxial flexibility, meaning they can be deformed along two axes simultaneously.

[0003] Wood is a more environmentally friendly alternative to these materials. However, wood is a naturally anisotropic material, meaning that its mechanical properties depend on the direction in which the material is viewed. In particular, wood is not naturally flexible due to its structure. Thus, a thin sheet of wood (veneer) exhibits better bending properties in the tangential direction (parallel to the grain, at 90°) than in the longitudinal or axial direction (along the grain, at 0°). These properties remain limited, however, as the deformation radii accepted by the wood sheet are relative to its thickness. This is primarily due to the fact that there is no possible stress transfer within the lignocellulosic structure.

[0004] The non-permanent softening of wood is known to those skilled in the art. For example, softening methods using steam or ammonia make it possible to give wood angles that are not possible under ambient humidity and / or temperature conditions. The introduced compounds act as a plasticizer for the wood components. However, the resulting flexibility is not permanent; the wood regains its initial rigidity once the vapors are extracted.

[0005] It is also common practice to obtain the thinnest possible wood cut in order to reduce the acceptable radius of curvature before breakage, these two parameters being interdependent.

[0006] Surface cuts in the wood were also made using various methods to increase flexibility. However, the resulting wood shows marks from the cutting process, which alters its natural appearance.

[0007] Another method is calendering the wood, that is, passing it between two rollers to flatten it. This method, however, requires specific humidity and temperature conditions to soften the wood, thus weakening it. Another option involves using calenders with a particular geometry (notched, for example), which impacts the final appearance of the wood and weakens it.

[0008] Impregnation of compounds within the wood is also known to ensure a certain flexibility but this only has an impact on flexibility under tangential stress (perpendicular to the fibers).

[0009] Thus, to date, there is no method for obtaining a flexible ligno-cellulosic material, i.e., one exhibiting permanent bi-axial flexibility at room temperature while retaining a natural appearance and feel.

[0010] Surprisingly and unexpectedly, the inventors found that the process according to the invention made it possible to obtain a ligno-cellulosic composite material exhibiting improved bi-axial flexibility compared to the starting material and permanent at room temperature while retaining a natural appearance and feel. Summary of the invention

[0011] A first object of the invention relates to a process for obtaining a lignocellulosic composite material comprising the following steps: - a step (1) of partial hydration and / or partial dissolution of the cellulose and / or hemicelluloses present in the lignocellulosic material, - a step (2) of impregnation by at least one filler compound of the ligno-cellulosic material from step (1), - a step (3) of implementation of the ligno-cellulosic material from step (2), said process comprising an in-situ regeneration step of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

[0012] The invention also relates to a ligno-cellulosic composite material that can be obtained by the process as defined above.

[0013] The invention also relates to the use of the material as defined above for the manufacture of parts, containers, coatings or surfaces. DETAILED DESCRIPTION

[0014] A first object of the invention relates to a process for obtaining a lignocellulosic composite material comprising the following steps: - a step (1) of partial hydration and / or partial dissolution of the cellulose and / or hemicelluloses present in the lignocellulosic material, - a step (2) of impregnation by at least one filler compound of the ligno-cellulosic material from step (1), - a step (3) of implementation of the ligno-cellulosic material from step (2), said process comprising an in-situ regeneration step of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

[0015] By "including the following steps" we mean here "including at least the following steps".

[0016] Thus, the present inventors have found, surprisingly and unexpectedly, that the specific combination of these three steps makes it possible to confer specific properties to the composite material while allowing it to retain a natural look and feel.

[0017] By "partial hydration of cellulose and / or hemicelluloses" we preferably mean the hydration of at least a part of the cellulose and / or hemicelluloses present in the lignocellulosic material.

[0018] By "partial dissolution of cellulose and / or hemicelluloses" we preferably mean the dissolution of at least a part of the cellulose and / or hemicelluloses present in the lignocellulosic material.

[0019] Preferably, "partial dissolution of cellulose and / or hemicelluloses" means a partial solubilization of cellulose and / or hemicelluloses, that is to say, a solubilization of at least a part of the cellulose and / or hemicelluloses present in the lignocellulosic material.

[0020] Preferably, in the process as defined above: - step (1) is a chemical treatment step of a lignocellulosic material, allowing the hydration and / or partial dissolution of the cellulose and / or hemicelluloses present in the lignocellulosic material, - step (2) is an impregnation step using at least one filler compound of the lignocellulosic material from step (1), and - step (3) is an implementation step involving mechanical treatment of the lignocellulosic material obtained from step (2), said process comprising an in-situ regeneration step of cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

[0021] Preferably, in the process as defined above: - step (1) is a chemical treatment step of a lignocellulosic material using at least one solvent selected from non-derivatizing aqueous solvents, non-derivatizing non-aqueous solvents, derivatizing solvents, and mixtures thereof, enabling the hydration and / or partial dissolution of the cellulose and / or hemicelluloses present in the lignocellulosic material, - step (2) is an impregnation step with at least one filler compound of the lignocellulosic material from step (1) so as to plasticize the cellulose and / or hemicelluloses present in the lignocellulosic material, and - step (3) is an implementation step by mechanical treatment of the ligno-cellulosic material from step (2) aimed at destructuring the internal structure of the ligno-cellulosic material, said process including an in-situ regeneration step of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

[0022] Thus, preferably, in step (1), the lignocellulosic material is treated with a treatment agent that disrupts the hydrogen bond network present within the cellulose and / or hemicelluloses and partially dissolves them within its structure without extracting them from the lignocellulosic material and consequently affecting other cell wall components such as lignin. Advantageously, this step allows for the selective partial dissolution and / or hydration of the cellulose and / or hemicelluloses in order to expose the cellulose and / or hemicellulose microfibrils and / or nanofibrils, thereby making them more accessible. Once exposed, these fibrils remain stable as long as their structure is hydrated by the solvent.Hydration and / or partial dissolution of cellulose and / or hemicelluloses also allows the lignocellulosic material to have a greater affinity for the fillers used in step (2).

[0023] By "in-situ regeneration" we preferably mean the in-situ precipitation of cellulose and / or hemicelluloses present in the lignocellulosic material.

[0024] In-situ regeneration of cellulose and / or hemicelluloses can take place following chemical treatment (1) and / or during the impregnation step (2).

[0025] For example, in-situ regeneration of cellulose and / or hemicelluloses can be carried out by neutralizing the ligno-cellulosic material following chemical treatment (1), for example when using basic solutions.

[0026] In-situ regeneration of cellulose and / or hemicelluloses can also be carried out using the solvents and / or fillers used in step (2).

[0027] The step of chemically treating a ligno-cellulosic material using at least one solvent chosen from non-derivatizing aqueous solvents, non-derivatizing non-aqueous solvents, derivatizing solvents, and mixtures thereof is preferably a soaking step.

[0028] By "non-derivatizing solvent" we preferably mean any solvent which allows hydration or dissolution of a substrate without chemically altering the structure of the dissolved element.

[0029] The non-derivatizing aqueous solvent may be chosen from, but not limited to, the aqueous solutions of transition metal complexes such as cu-prammonium hydroxide, cupriethylenediamine hydroxide and mixtures thereof, aqueous solutions of ammonium hydroxides such as tetraethylammonium hydroxide, aqueous solutions of alkali hydroxides such as sodium hydroxide, aqueous solutions of mineral acids such as sulfuric acid, phosphoric acid and mixtures thereof, aqueous solutions of salts such as zinc chloride, lithium chloride, sodium chloride and mixtures thereof, aqueous solutions of urea and its derivatives such as thiourea, and mixtures thereof.

[0030] The non-aqueous non-derivatizing solvent may be chosen from, but not limited to, ionic liquids, poly(ionic liquids), organic solvents such as methylmorpholine oxide, dimethylacetamide, ammonia, dimethyl sulfoxide, deep eutectic solvents, and mixtures thereof.

[0031] Examples of ionic liquids include, but are not limited to, salts consisting of at least one organic cation such as pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, piperidinium, pyrrolidinium, quinolinium, isoquinolinium or their derivatives, and / or at least one organic or inorganic anion such as halides, tetrachloroaluminate, nitrates, hexafluorophosphate, tetrafluoro-roborate, sulfonates, sulfates, thiocyanates, dicyanamide, carboxylates or their derivatives, and mixtures thereof.

[0032] Examples of pyridinium salts include, but are not limited to, pyridinium ethyl chloride.

[0033] Examples of poly(ionic liquids) include, but are not limited to, polymers consisting of a chain of organic cations such as pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, piperidinium, pyrrolidinium, quinolinium, isoquinolinium or their derivatives, forming salts with organic or inorganic anions such as halides, tetrachloroaluminate, nitrates, hexafluorophosphate, tetrafluoroborate, sulfonates, sulfates, thiocyanates, dicyanamidide, carboxylates or their derivatives, and mixtures thereof.

[0034] The non-aqueous non-derivatizing solvent can be used in combination with salts such as lithium chloride.

[0035] Preferably, dimethylacetamide is used in combination with salts such as lithium chloride.

[0036] By "derivatizing solvent" we preferably mean solvents in which the hydration or dissolution of a substrate takes place in combination with covalent derivatization and induces the formation of a derivative of the substrate, for example an ester, an acetal or an ether.

[0037] The derivatizing solvent may be chosen from, but not limited to, acetic acid and its derivatives such as trifluoroacetic acid, dichloroacetic acid, and mixtures thereof, formic acid, nitrogen peroxide, dimethylformamide, paraformaldehyde, chlorotrimethylsilane, acetic anhydride and its derivatives, nitric acid and its derivatives, and mixtures thereof.

[0038] Examples of acetic anhydride derivatives include, but are not limited to, trichloroacetic anhydride.

[0039] Examples of nitric acid derivatives include, but are not limited to, nitric anhydride.

[0040] Examples of mixtures include, but are not limited to, a mixture of sodium hydroxide and urea, a mixture of sodium hydroxide and thiourea, a mixture of zinc chloride and lithium chloride, a mixture of dimethylacetamide and lithium chloride, a mixture of ammonia, sodium chloride and dimethyl sulfoxide, a mixture of nitrogen peroxide and dimethylformamide, a mixture of sulfuric acid and formic acid, a mixture of paraformaldehyde and dimethyl sulfoxide, a mixture of chlorotrimethylsilane and dimethyl sulfoxide, and mixtures thereof, preferably a mixture of sodium hydroxide and urea, a mixture of sodium hydroxide and thiourea, and mixtures thereof.

[0041] Preferably, the mixture is an aqueous mixture of sodium hydroxide and urea or an aqueous mixture of sodium hydroxide and thiourea.

[0042] When the solvent used in step (1) of chemical treatment is an aqueous solvent, the concentration of the species in solution is preferably between 1% and 25%, preferably between 5% and 20% by weight of dry matter relative to the weight of the solution.

[0043] Advantageously, this concentration range makes it possible to sufficiently hydrate or dissolve the cellulose and / or hemicelluloses without damaging the structure of the ligno-cellulosic material.

[0044] Preferably, during the chemical treatment step (1), the weight ratio of ligno-cellulosic material to the weight of solvent is between 0.5% and 99%, preferably between 1% and 50%, and even more preferably between 2% and 25%, or preferably between 0.5% and 50%, and even more preferably between 0.5% and 25%.

[0045] Preferably, the solvent used in step (1) of chemical treatment is a non-derivatizing aqueous solvent, a non-derivatizing non-aqueous solvent, and mixtures thereof, and even more preferably a non-derivatizing aqueous solvent.

[0046] Surprisingly and unexpectedly, the present inventors found that non-derivatizing aqueous solvents, non-derivatizing non-aqueous solvents, and mixtures thereof improved the interaction between the lignocellulosic material and the filler element.

[0047] The chemical treatment step can be carried out for a period of between 1 minute and 24 hours, preferably between 5 minutes and 15 hours, and more preferably between 15 minutes and 6 hours.

[0048] Step (1) of the treatment may be followed by an optional washing step with a solvent to remove excess reagent and / or reaction residues. It may be preferable to keep the lignocellulosic material as obtained at the end of the treatment, without an additional washing step.

[0049] Preferably, the solvent used during the optional washing step is water.

[0050] The treatment step (1) and / or the optional washing step may be followed of a drying step of the lignocellulosic material. Drying can eliminate the solvent used for the chemical treatment step.

[0051] Advantageously, step (1) of chemical treatment of the ligno-cellulosic material aimed at partially hydrating and / or dissolving the cellulose and / or hemicelluloses allows for more intimate contact between the cellulose and / or hemicelluloses and the filler element used in step (2).

[0052] Advantageously, the impregnation step (2) allows the filler to penetrate the cell wall of the lignocellulosic material. This results in plasticization of the cellulose and / or hemicelluloses at the molecular level. Advantageously, thanks to this plasticization, at the end of the impregnation step (2), the lignocellulosic material is made flexible in the tangential direction (parallel to the fibers). During the impregnation step (2), the lumens of the lignocellulosic material can be left empty or can be filled by the filler(s).

[0053] One or more fillers may be used in this impregnation step (2). This impregnation step may also be repeated at least once with fillers of the same or different nature as the first filler. Successive impregnation steps may complete the first impregnation by, for example, filling the lumens and imparting other properties to the lignocellulosic material.

[0054] By "repeated at least once" we preferably mean repeated from 1 to 10 times, more preferably from 1 to 5 times, and even more preferably from 1 to 3 times.

[0055] The impregnation step (2) can be carried out with the filler element alone or via an impregnation vector such as a solvent that allows for better diffusion of the filler element within the lignocellulosic material. The solvent used in the impregnation step can be the same as that used in the chemical treatment step (1) or the same as that used in the optional washing step.

[0056] Preferably, the filler compound is chosen for the affinities that it develops with the elements of the ligno-cellulosic material in such a way as to bring, for example, a plasticizing and / or reinforcing effect to the latter.

[0057] Advantageously, the filler compound is a compound capable of penetrating the cell walls of the lignocellulosic material and exhibiting an affinity for the polymers constituting the lignocellulosic material. Preferably, the filler compound exhibits as many interactions as possible with cellulose and / or hemicelluloses so as to plasticize them, and potentially with other constituents of the lignocellulosic material such as lignin, which it can also plasticize. Thus, any compound capable of associating with and creating interactions with the constituents of the cell wall of the lignocellulosic material, particularly cellulose and / or hemicelluloses, is preferred.

[0058] The filling compound can be selected from polymers, pre-polymers, monomers, compounds from the hydrolysis of oxyranic compounds such as ethylene glycol, aziridine derivatives such as ethanolamine, compounds from the polymerization of oxyranic compounds such as polyethylene glycol, compounds from the polymerization of aziridine derivatives such as polyethyleneimine, polyols such as glycerol, carbohydrates such as sorbitol, ionic liquids and poly(ionic liquids), deep eutectic solvents, natural polymers such as cellulose, starch and / or chitosan and their derivatives, synthetic polymers and their monomers such as polyvinyl alcohol or polyurethanes, polycarboxylic acids such as citric acid, and mixtures thereof.

[0059] Examples of polymers include, but are not limited to, oligomers, polyethers such as polyethylene glycol, aliphatic polyols such as polyvinyl alcohol, polyamines such as polyethyleneimine, polyurethanes, polyesters, and mixtures thereof.

[0060] Examples of prepolymers include, but are not limited to, polyester diols, polycarbonate diols, polyalkadiene diols, epoxy resins, methane prepolymers, and mixtures thereof.

[0061] Examples of monomers include, but are not limited to, oxyranic compounds, aziridinic compounds, methacrylic compounds, acrylic compounds, epoxies, methanes, and mixtures thereof.

[0062] Examples of ionic liquids include, but are not limited to, salts consisting of at least one organic cation such as pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, piperidinium, pyrrolidinium, quinolinium, isoquinolinium or their derivatives, and / or at least one organic or inorganic anion such as halides, tetrachloroaluminate, nitrates, hexafluorophosphate, tetrafluoro- Roborate, sulfonates, sulfates, thiocyanates, dicyanamide, carboxylates or their derivatives, and mixtures thereof.

[0063] Examples of pyridinium salts include, but are not limited to, pyridinium ethyl chloride.

[0064] Examples of poly(ionic liquids) include, but are not limited to, polymers consisting of a chain of organic cations such as pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, piperidinium, pyrrolidinium, qui-nolinium, isoquinolinium or their derivatives, forming salts with organic or inorganic anions such as halides, tetrachloroaluminate, nitrates, hexafluorophosphate, tetrafluoroborate, sulfonates, sulfates, thiocyanates, dicyanamidide, carboxylates or their derivatives, and mixtures thereof.

[0065] Examples of deep eutectic solvents include, but are not limited to, mixtures of a quaternary ammonium compound with a hydrogen bond-donating compound.

[0066] Examples of quaternary ammonium compounds include, but are not limited to, choline chloride, chlorcholine chloride, betaines, ammonium chloride, and mixtures thereof.

[0067] Examples of hydrogen bond-donating compounds include, but are not limited to, amides such as urea, thiourea, methylurea, dimethylurea, acetamide, and mixtures thereof; carboxylic acids such as malonic acid, malic acid, maleic acid, citric acid, aconitic acid, and mixtures thereof; alcohols such as glycerol, ethylene glycol, polyethylene glycol, and mixtures thereof; carbohydrates such as glucose, fructose, sucrose, cyclodextrins, and mixtures thereof; and mixtures of these.

[0068] Examples of natural polymer derivatives include, but are not limited to, methylcellulose, ethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, cellulose acetate, cellulose nitrate, hydroxypropyl starch, hydroxyethyl starch, cationic starch, carboxymethyl starch, phosphated starch, acetylated starch, starch octenyl succinate, and mixtures thereof

[0069] The ratio between the filler compound and the ligno-cellulosic material can vary according to the desired properties.

[0070] Preferably, the filling compound is present in a concentration of between 1% and 99%, more preferably between 15% and 75%, and even more preferably between 20% and 60% by weight relative to the total weight of the ligno-cellulosic material.

[0071] The impregnation step (2) may be followed by an optional drying step. Drying may be carried out following impregnation in the case of using a impregnation vector and / or to enable polymerization of the filler compound such as monomers. Drying can also prepare the lignocellulosic material for subsequent steps such as optional lamination.

[0072] Advantageously, at the end of the treatment (1) and impregnation (2) steps, the ligno-cellulosic material exhibits improved flexibility under tangential stress.

[0073] Advantageously, the mechanical treatment step (3) allows the structure of the lignocellulosic material to be broken down, and in particular, the internal structure of the lignocellulosic material to be sheared in order to soften it in the axial direction (grain direction). The impregnated filler and the optional bonded material can help maintain the integrity of the lignocellulosic material. During this step, the hydrogen bond network present within the lignocellulosic material can be rearranged with the filler.

[0074] Advantageously, the mechanical treatment step (3) impacts the biaxial flexibility of the material by microcracking the structure at the mesoscopic scale, and by bringing the filling element and the structure closer together by creating bonds at the molecular scale.

[0075] The mechanical processing step can be chosen from, but not limited to, scarfing, bending, calendering, lamination, embossing, blistering, emerying, moiréing, fulling, sanforizing, hammering, staking, crumpling, and combinations thereof, preferably calendering.

[0076] The mechanical treatment step (3) can be carried out before, during or after the optional laminating step and before, during or after the optional finishing step.

[0077] The calendering is preferably carried out using a belt press. Preferably, the diameter of the press rollers is between 50 cm and 10 mm. Preferably, the wood makes between 1 and 500 passes, more preferably between 20 and 450 passes, and more preferably between 50 and 400 passes in the belt press. Preferably, the pressure applied by the belt press cylinders is between 0 and 20 bar, more preferably between 1 and 15 bar, and even more preferably between 2 and 10 bar.

[0078] Advantageously, during the process of the present invention, the internal mesoscopic structure of the lignocellulosic material is fractured so as to reduce the natural anisotropy of the lignocellulosic material without affecting its external appearance. The mechanical treatment allows for a closer proximity of the filler element to the cellulose and / or hemicelluloses of the lignocellulosic material, which has been made more accessible through the chemical treatment. Advantageously, these two combined treatments have the following effect: This results in an increased plasticizing effect of the filler on the lignocellulosic material. This dual action of cracking and pressure thus allows for the development of new flexural properties in the lignocellulosic material.

[0079] Preferably, the mechanical treatment step is separate from the tests aimed at controlling the mechanical properties of the ligno-cellulosic composite material that can be obtained by the process as defined above.

[0080] Part of the cell wall components other than cellulose and / or hemicelluloses can be extracted during step (1).

[0081] Preferably, the process as defined above further includes a step of partial delignification of the ligno-cellulosic material in order to obtain a partially delignified ligno-cellulosic material.

[0082] The amount of lignin extracted can be between 0.5% and 99%, preferably between 1% and 50%, and even more preferably between 5% and 45% relative to the total weight of lignin present in the lignocellulosic material.

[0083] The optional partial delignification step can, in particular, reduce the density of the lignocellulosic material and extend the range of usable lignocellulosic materials. Reducing the lignin content can also allow the lignocellulosic material to have a greater affinity for subsequent fillers.

[0084] The process as defined above may further include at least one step selected from the group consisting of a bleaching step of the ligno-cellulosic material, a partial or total extraction step of extractables and chromophores from the ligno-cellulosic material, an activation step of the hydroxyl groups of the ligno-cellulosic material, a substitution step of the hydroxyl groups of the ligno-cellulosic material, an oxidation step of the ligno-cellulosic material, a reduction step of the ligno-cellulosic material, a transformation step of the ligno-cellulosic material such as slitting to reduce its thickness, and combinations thereof.

[0085] These steps can for example be carried out before, during or after the treatment step (1), and / or before, during or after the optional washing step (2) following the treatment step (1).

[0086] The process as defined above may further include a step of bonding a material, preferably a flexible material, onto the ligno-cellulosic material or a step of bonding said ligno-cellulosic composite material onto itself in order to obtain a reinforced material.

[0087] The bonded material may be chosen from, but not limited to, a textile, an untanned or tanned hide such as leather, rubber, latex, a foam, another composite material different from the composite material obtained, and a mixture of these last.

[0088] This laminating step can be carried out following the impregnation step (2) (in the case where the process does not include an optional drying step following the impregnation step (2)) or following the optional drying step (in the case where the process includes an optional drying step following the impregnation step (2)).

[0089] During this optional lamination step, the material can be laminated onto a flexible element, thus retaining the flexibility acquired during the impregnation step (2) while improving the material's mechanical strength, such as tear resistance. However, the ligno-cellulose material can be used without this additional lamination step, as its strength may be sufficient for many applications.

[0090] This optional lamination can be permanent or temporary depending on whether the reinforcing material is to be present in the final material or whether recycling of the material is envisaged.

[0091] This optional lamination can be carried out before or after the optional material transformation step such as slitting to reduce its thickness.

[0092] Preferably, the glue used during the laminating step does not alter the flexibility of the material and can be used despite the modifications made by the step (1) of chemical treatment and the step (2) of impregnation with the filling compound.

[0093] Examples of adhesives that can be used during this laminating step include, but are not limited to, vinyl adhesives, acrylic adhesives, cyanoacrylate adhesives, neoprene adhesives, epoxy adhesives, silicone-based adhesives, polyurethane-based adhesives, natural polymer-based adhesives, heat-sealable films, and mixtures thereof.

[0094] The process as defined above may include at least one finishing step comprising coating one or more faces of the material with a protective agent and / or a physical or chemical treatment step of one or more faces of the material.

[0095] Examples of physical or chemical treatment steps include, but are not limited to, plasma treatment, corona treatment, reaction of the material surface with silanes, and their combinations.

[0096] Advantageously, the finishing step protects the material with an element that provides it with surface properties such as color, mechanical strength (scratch resistance), UV resistance, and hydrophobicity (moisture resistance). This finishing step can also limit the exudation of the filler element over time. This step is optional. in the sense that protection can also be provided by the filler used during the impregnation step (2). Thus, this finishing step can be carried out during the impregnation step by filling the lumens with a polymer, by applying a varnish, by coating, or by chemically modifying the surface of the lignocellulosic material. For example, to improve UV resistance, UV-absorbing agents can be added during the optional finishing step and / or antioxidants can be present in the filler.

[0097] Advantageously, the finish applied allows the material to retain its flexibility.

[0098] Advantageously, following the processing operations and before or after the application of the finish, the wood is rendered sufficiently flexible to undergo processing operations that are not normally possible on wood. The material thus obtained can, for example, be split to very thin thicknesses.

[0099] Preferably, said ligno-cellulosic material is wood.

[0100] The wood may be green wood, wet wood, or dry wood as defined in WO2017098149 (Al) or WO2018224598 (Al). For example, the wood may be wood used after possible storage for a more or less extended period (from a few days to a few years). This wood may have been processed after felling, i.e., it may have been cut, sawn, planed, stripped of its bark, sapwood, or heartwood, or it may be engineered wood. It may also be aged wood, i.e., wood that has already been used, such as construction timber. This wood may come from various species and wood types such as those defined in WO2017098149 (Al) or WO2018224598 (Al). This wood may have undergone physical or chemical treatment.

[0101] The ligno-cellulosic material can, for example, be in the form of a sheet, a board, a plate or a veneer of solid wood.

[0102] Advantageously, the process of the present invention is a process for obtaining a ligno-cellulosic composite material exhibiting bi-axial flexibility, preferably at room temperature, and even more preferably permanent at room temperature.

[0103] Advantageously, the process of the present invention is a process for obtaining a ligno-cellulosic composite material exhibiting bi-axial flexibility, preferably at room temperature, and even more preferably permanent at room temperature, improved compared to the starting ligno-cellulosic material.

[0104] The present invention also relates to a ligno-cellulosic composite material that can be obtained by the process as defined above.

[0105] Preferably, said material as defined above exhibits bi- flexibility axial.

[0106] Preferably, said material as defined above exhibits biaxial flexibility at room temperature.

[0107] Preferably, said material as defined above exhibits permanent biaxial flexibility at room temperature.

[0108] Surprisingly and unexpectedly, the present inventors found that the process as defined above makes it possible to obtain a lignocellulosic material exhibiting permanent biaxial flexibility at room temperature. In particular, the set of steps (1) to (3) makes it possible to eliminate the natural resistance of the lignocellulosic material to bending without loss of mechanical properties and to obtain a lignocellulosic material with a natural appearance and feel. Advantageously, the process according to the present invention is easy to implement.

[0109] By “biaxial flexibility” we preferably mean the maximum deformation that can be made to the material before its plastic deformation.

[0110] Preferably, the material as defined above has a bi-axial radius of curvature between 0.1 mm and 100 mm, preferably between 0.5 mm and 50 mm, and even more preferably between 1 mm and 10 mm.

[0111] Thus, advantageously, the material as defined above has a radius of curvature much smaller than that of the initial material, particularly in the longitudinal direction.

[0112] Preferably, the material as defined above has a thickness between 0.1 mm and 10 mm, preferably between 0.25 mm and 5 mm, and even more preferably between 0.5 mm and 2 mm.

[0113] Preferably, the material as defined above exhibits resistance to repeated bending.

[0114] Preferably, the material as defined above has a tensile strength equal to or greater than that of the initial lignocellulosic material.

[0115] Preferably, the material as defined above has a resistance to friction identical to or greater than that of the initial ligno-cellulosic material.

[0116] Preferably, the material as defined above, for example that obtained at the end of optional steps such as lamination and / or obtained at the end of successive impregnation steps, has improved tear resistance compared to the initial lignocellulosic material.

[0117] Preferably, the material as defined above, for example that obtained at the end of the finishing step, has improved surface properties compared to the initial ligno-cellulosic material.

[0118] Preferably, the material as defined above has the ability to be sewn, the ability to be split, and the ability to be trimmed, unlike the natural lignocellulosic material.

[0119] The present invention also relates to a ligno-cellulosic composite material as defined above as such.

[0120] The present invention also relates to the use of the material as defined above, for the manufacture of parts, containers, coatings or surfaces.

[0121] The material as defined above can in particular be used in industries using flexible elements for clothing, in particular the textile, leather, packaging or automotive sectors. DESCRIPTION OF THE FIGURES

[0122] [Fig.1]: Photographs of the material obtained. This figure shows the biaxial flexibility (hyperbolic paraboloid surfaces - longitudinal flexibility) of the material obtained at the end of the mechanical treatment step of the process of example 1.

[0123] [Fig.2]: Diagram showing the tangential radius of curvature of the material obtained after each step of the process in example 1 compared to the initial material used.

[0124] [Fig.3]: Diagram showing the tensile mechanical properties of the material obtained at the end of the impregnation step of example 1 compared to the initial material used. EXAMPLES Example 1:

[0125] Step 1: Chemical treatment

[0126] In a glass reactor, 45 g of sodium hydroxide is dissolved in 450 g of distilled water at 5°C with stirring. After the sodium hydroxide has dissolved, 5 g of urea is dissolved in the solution. The resulting solution has a mass composition of 9% sodium hydroxide, 1% urea, and 90% water.

[0127] The temperature of the solution is brought down to 10°C.

[0128] A sheet of sycamore maple veneer measuring 150x150x0.6 mm is introduced into the reactor containing the solution. The treatment is carried out for a period of 6 hours at a temperature of 10°C.

[0129] The sycamore maple leaf is then extracted from this medium and placed in a bath of distilled water at 35°C for 30 minutes. This operation is repeated 3 times to obtain a neutral pH.

[0130] Step 2: Impregnation

[0131] The chemically treated wood sheet is then immersed in a 50% polyethylene glycol 400 solution for 72 hours at 25°C. The sheet is then removed from this bath and dried at 103°C for 24 hours and then at 25°C for 1 week.

[0132] Step 3: Mechanical treatment

[0133] The impregnated wood sheet is then fed into a belt press consisting of 10 rollers, each 25 cm in diameter, with a pressure of 5 bars. The resulting wood sheet exhibits biaxial flexibility and can be repeatedly deformed without breaking.

[0134] The radius of curvature was measured by rods of decreasing diameters on rectangular test pieces of 100 mm by 50 mm.

[0135] The breaking strength was measured by a tensile testing machine (Testometric X350) according to the ISO 527 method.

[0136] The characteristics of the material obtained are presented in Table 1 and in Figures 1 to 3.

[0137] [Tables 1] Property Orientation at 0° Orientation at 90° Original wood Modified wood Original wood Modified wood Radius of bend without fiber breakage 40 mm 5 mm 5 mm Bendable in 2 without fiber breakage Tensile strength 47 MPa 52 MPa 6 MPa 3 MPa

Claims

Demands

1. A process for obtaining a ligno-cellulosic composite material comprising the following steps: - a step (1) of partial hydration and / or partial dissolution of the cellulose and / or hemicelluloses present in the ligno-cellulosic material, - a step (2) of impregnation with at least one filler compound of the ligno-cellulosic material obtained from step (1), and - a step (3) of processing the ligno-cellulosic material obtained from step (2), said process comprising an in-situ regeneration step of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

2. A method for manufacturing a ligno-cellulosic composite material according to claim 1, characterized in that: - step (1) is a chemical treatment step of a ligno-cellulosic material enabling the hydration and / or partial dissolution of the cellulose and / or hemicelluloses present in the ligno-cellulosic material, - step (2) is an impregnation step with at least one filler compound of the ligno-cellulosic material obtained from step (1), and - step (3) is a processing step by mechanical treatment of the ligno-cellulosic material obtained from step (2), said method comprising an in-situ regeneration step of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

3. A method for manufacturing a lignocellulosic composite material according to claim 1 or 2, characterized in that: - step (1) is a chemical treatment step of a lignocellulosic material using at least one solvent selected from non-derivatizing aqueous solvents, non-derivatizing non-aqueous solvents, and mixtures thereof, enabling the hydration and / or partial dissolution of the cellulose and / or hemicelluloses present in the lignocellulosic material, - step (2) is an impregnation step with at least one filler compound of the lignocellulosic material obtained in step (1) so as to plasticize the cellulose and / or hemicelluloses present in the ligno-cellulosic material, and - step (3) is an implementation step by mechanical treatment of the ligno-cellulosic material from step (2) aimed at destructuring the internal structure of the ligno-cellulosic material, said process including an in-situ regeneration step of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

4. A process according to any one of claims 1 to 3, characterized in that the filler compound is selected from polymers, prepolymers, monomers, compounds from the hydrolysis of oxyranic compounds such as ethylene glycol, aziridine derivatives such as ethanolamine, compounds from the polymerization of oxyranic compounds such as polyethylene glycol, aziridine derivatives such as polyethyleneimine, polyols such as glycerol, carbohydrates such as sorbitol, ionic liquids and poly(ionic liquids), deep eutectic solvents, natural polymers such as cellulose, starch and / or chitosan, synthetic polymers and their monomers such as polyvinyl alcohol or polyurethanes, polycarboxylic acids such as citric acid, and mixtures thereof.

5. A process according to claim 3 or 4, characterized in that the non-derivatizing aqueous solvent is selected from aqueous solutions of transition metal complexes such as cu-prammonium hydroxide, cupriethylenediamine hydroxide and mixtures thereof, aqueous solutions of ammonium hydroxides such as tetraethylammonium hydroxide, aqueous solutions of alkali hydroxides such as sodium hydroxide, aqueous solutions of mineral acids such as sulfuric acid, phosphoric acid and mixtures thereof, aqueous solutions of salts such as zinc chloride, lithium chloride, sodium chloride and mixtures thereof, aqueous solutions of urea and its derivatives such as thiourea, and mixtures thereof.

6. A method according to any one of claims 3 to 5, characterized in that the non-aqueous non-derivatizing solvent is selected from ionic liquids, poly(ionic liquids), organic solvents such as methylmorpholine oxide, dimethylacetamide, ammonia, dimethyl sulfoxide, deep eutectic solvents, and mixtures thereof.

7. A method according to any one of claims 2 to 6, characterized in that the mechanical treatment step is selected from scarving, bending, calendering, laminating, embossing, blistering, grinding, moiréing, fulling, sanforizing, hammering, paving, flaking, crumpling, and combinations thereof.

8. A method according to any one of claims 2 to 6, characterized in that the mechanical treatment step is selected from calendering.

9. A process according to any one of claims 1 to 8, characterized in that it further comprises at least one step selected from the group consisting of a bleaching step of the ligno-cellulosic material, a partial or total extraction step of extractables and chromophores from the ligno-cellulosic material, an activation step of the hydroxyl groups of the ligno-cellulosic material, a substitution step of the hydroxyl groups of the ligno-cellulosic material, an oxidation step of the ligno-cellulosic material, a reduction step of the ligno-cellulosic material, a transformation step of the ligno-cellulosic material, and combinations thereof.

10. A method according to any one of claims 1 to 9, characterized in that it further comprises a step of laminating a material onto the ligno-cellulosic material or a step of laminating said ligno-cellulosic composite material onto itself in order to obtain a reinforced material.

11. Ligno-cellulosic composite material obtainable by the process as defined according to any one of claims 1 to 10.

12. Material according to claim 11, characterized in that it exhibits bi-axial flexibility at room temperature.

13. Use of the material as defined according to claim 11 or 12, for the manufacture of parts, containers, coatings or surfaces.

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