Method for obtaining a lignocellulosic composite material and composite material obtained by this method

Abstract

The present invention relates to a method for obtaining a lignocellulosic composite material, a lignocellulosic composite material capable of being obtained by this method, and the use of this lignocellulosic composite material.

Description

[0001] METHOD FOR OBTAINING A LIGNO-CELLULOSIC COMPOSITE MATERIAL AND COMPOSITE MATERIAL OBTAINED BY THIS METHOD

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method for obtaining a lignocellulosic composite material, a lignocellulosic composite material capable of being obtained by this method and the use of this lignocellulosic composite material.

[0004] TECHNICAL BACKGROUND

[0005] The flexible materials currently used are produced using highly polluting chemical and physical processes. The flexible plastics industry relies primarily on petroleum resources such as Polyvinyl Chloride (PVC) or polyesters, and the textile and leather industry relies on transformation processes that can be lengthy and polluting, such as tanning in baths of solutions of chromium-based compounds. The main quality of these materials is their biaxial flexibility, meaning they can be deformed in two axes simultaneously.

[0006] Wood is a more environmentally friendly alternative to these materials. However, wood is a naturally anisotropic material, meaning its mechanical properties depend on the direction in which the material is considered. In particular, wood is not naturally flexible due to its structure. Thus, a thin sheet of wood (veneer) has better bending properties in the tangential direction (parallel to the fibers, at 90°) than in the longitudinal or axial direction (direction of the fibers, at 0°). These properties remain limited, however, as the deformation radii accepted by the wood sheet are relative to its thickness. This is mainly due to the fact that there is no possible transfer of stress within the lignocellulosic structure.

[0007] Non-permanent softening of wood is known to those skilled in the art. For example, softening methods using water vapor or ammonia can give the wood angles that are not possible under ambient humidity and / or temperature conditions. The compounds introduced act as a plasticizer of the wood components. However, the flexibility provided is not permanent, as the wood regains its initial rigidity once the vapors are extracted from the wood.

[0008] It is also customary to obtain the finest possible cut of wood in order to reduce the accepted radius of curvature before breaking, these two parameters being interdependent.

[0009] Surface cutting of the wood by various methods has also been carried out to increase flexibility. However, the resulting wood has marks due to the cutting carried out, which changes the natural appearance of the wood.

[0010] Another method is calendering the wood, i.e. passing it between two rollers to crush it. This method, however, requires specific humidity and temperature conditions to be respected so that it can soften the wood, thus weakening it. Another option involves the use of calenders with a particular geometry (notched for example) which has an impact on the final appearance of the wood and weakens it. Impregnating compounds within the wood is also known to ensure a certain flexibility but this only has an impact on the flexibility under tangential stress (perpendicular to the fibers).

[0011] Thus, to date, there is no method for obtaining a flexible lignocellulosic material, i.e. one with permanent biaxial flexibility at room temperature while retaining a natural appearance and feel.

[0012] Surprisingly and unexpectedly, the inventors found that the process according to the invention made it possible to obtain a lignocellulosic composite material having improved biaxial flexibility compared to the starting material and permanent at room temperature while retaining a natural appearance and feel.

[0013] SUMMARY OF THE INVENTION

[0014] A first subject of the invention relates to a method 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 with at least one filling compound of the lignocellulosic material resulting from step (1), a step (3) of processing the lignocellulosic material resulting from step (2), said method comprising a step of in-situ regeneration of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

[0015] The invention also relates to a lignocellulosic composite material capable of being obtained by the process as defined above.

[0016] The invention also relates to the use of the material as defined above, for the manufacture of parts, containers, coatings or surfaces.

[0017] DETAILED DESCRIPTION

[0018] A first subject of the invention relates to a method 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 with at least one filling compound of the lignocellulosic material resulting from step (1), a step (3) of processing the lignocellulosic material resulting from step (2), said method comprising a step of in-situ regeneration of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

[0019] By "comprising the following steps" is meant here "comprising at least the following steps". Thus, the present inventors have surprisingly and unexpectedly found that the specific combination of these three steps makes it possible to confer specific properties on the composite material while allowing it to retain a natural appearance and feel.

[0020] By "partial hydration of cellulose and / or hemicelluloses" is preferably meant the hydration of at least part of the cellulose and / or hemicelluloses present in the lignocellulosic material.

[0021] By "partial dissolution of cellulose and / or hemicelluloses" is preferably meant the dissolution of at least part of the cellulose and / or hemicelluloses present in the lignocellulosic material.

[0022] Preferably, by "partial dissolution of the cellulose and / or hemicelluloses" is meant a partial solubilization of the cellulose and / or hemicelluloses, i.e. a solubilization of at least part of the cellulose and / or hemicelluloses present in the lignocellulosic material.

[0023] Preferably, in the method as defined above:

[0024] - step (1) is a step of chemical treatment of a lignocellulosic material, making it possible to hydrate and / or partially dissolve the cellulose and / or hemicelluloses present in the lignocellulosic material,

[0025] - step (2) is a step of impregnation with at least one filling compound of the lignocellulosic material resulting from step (1), and

[0026] - step (3) is a step of implementation by mechanical and / or thermal and / or thermo-hygro-mechanical treatment, preferably by mechanical treatment, of the lignocellulosic material resulting from step (2), said method comprising a step of in-situ regeneration of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

[0027] Preferably, in the method as defined above

[0028] - step (1) is a step of chemical treatment of a lignocellulosic material using at least one solvent chosen from non-derivatizing aqueous solvents, non-aqueous non-derivatizing solvents, derivatizing solvents, and mixtures thereof, making it possible to hydrate and / or partially dissolve the cellulose and / or hemicelluloses present in the lignocellulosic material,

[0029] - step (2) is a step of impregnation with at least one filling compound of the lignocellulosic material resulting from step (1) so as to plasticize the cellulose and / or the hemicelluloses present in the lignocellulosic material, and

[0030] - step (3) is a step of implementation by mechanical and / or thermal and / or thermo-hygro-mechanical treatment, preferably by mechanical treatment, of the lignocellulosic material resulting from step (2) aimed at destructuring the internal structure of the lignocellulosic material, said method comprising a step of in-situ regeneration of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2).

[0031] Thus, preferably, during step (1), the lignocellulosic material is treated using a treatment agent making it possible to destructure the network of hydrogen bonds present within the cellulose and / or hemicelluloses and to partially dissolve it (them) within its (their) structure without extracting it (them) from the lignocellulosic material and acting consequently on the other parietal elements such as lignin. Advantageously, this step will make it possible to dissolve and / or partially hydrate the cellulose and / or hemicelluloses selectively in order to expose the microfibrils and / or nanofibrils of cellulose and / or hemicelluloses and therefore to make the latter (these) 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 more affinity with the filler elements used in step (2).

[0032] By "in-situ regeneration" we preferably mean the in-situ precipitation of the cellulose and / or hemicelluloses present in the lignocellulosic material.

[0033] In-situ regeneration of cellulose and / or hemicelluloses can take place following chemical treatment (1) and / or during the impregnation step (2).

[0034] For example, in-situ regeneration of cellulose and / or hemicelluloses can be carried out by neutralization of the lignocellulosic material following chemical treatment (1), for example when using basic solutions.

[0035] In-situ regeneration of cellulose and / or hemicelluloses can also be carried out using the solvents and / or fillers used in step (2).

[0036] The step of chemically treating a lignocellulosic material using at least one solvent chosen from non-derivatizing aqueous solvents, non-aqueous non-derivatizing solvents, derivatizing solvents, and mixtures thereof is preferably a soaking step.

[0037] By "non-derivatizing solvent" we preferably mean any solvent allowing hydration or dissolution of a substrate without chemically modifying the structure of the dissolved element.

[0038] The non-derivatizing aqueous solvent may be selected from, but not limited to, aqueous solutions of transition metal complexes such as cuprammonium 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.

[0039] The non-aqueous non-derivatizing solvent may be selected 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.

[0040] 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, tetrafluoroborate, sulfonates, sulfates, thiocyanates, dicyanamide, carboxylates or their derivatives, and mixtures thereof.

[0041] Examples of pyridinium salts include, but are not limited to, pyridinium ethyl chloride.

[0042] 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, dicyanamide, carboxylates or their derivatives, and mixtures thereof.

[0043] The non-aqueous, non-derivatizing solvent can be used in combination with salts such as lithium chloride.

[0044] Preferably, dimethylacetamide is used in combination with salts such as lithium chloride.

[0045] By "derivatizing solvent" is preferably meant 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.

[0046] The derivatizing solvent may be selected 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.

[0047] Examples of acetic anhydride derivatives include, but are not limited to, trichloroacetic anhydride.

[0048] Examples of nitric acid derivatives include, but are not limited to, nitric anhydride.

[0049] 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.

[0050] Preferably, the mixture is an aqueous mixture of sodium hydroxide and urea or an aqueous mixture of sodium hydroxide and thiourea.

[0051] When the solvent used during step (1) of chemical treatment is an aqueous solvent, the concentration of the species in solutions is preferably between 1% and 25%, preferably between 5% and 20% by weight of dry matter relative to the weight of the solution.

[0052] Advantageously, this concentration range allows the cellulose and / or hemicelluloses to be sufficiently hydrated or dissolved without damaging the structure of the lignocellulosic material.

[0053] Preferably, during step (1) of chemical treatment the weight ratio of lignocellulosic material relative to the weight of the 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%.

[0054] Preferably, the solvent used during step (1) of chemical treatment is a non-derivatizing aqueous solvent, a non-aqueous non-derivatizing solvent, and mixtures thereof, and even more preferably a non-derivatizing aqueous solvent.

[0055] 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.

[0056] 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.

[0057] Treatment step (1) 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.

[0058] Preferably, the solvent used in the optional washing step is water.

[0059] The treatment step (1) and / or the optional washing step may be followed by a drying step of the lignocellulosic material. Drying may remove the solvent used for the chemical treatment step.

[0060] Advantageously, step (1) of chemical treatment of the lignocellulosic material aimed at hydrating and / or partially dissolving the cellulose and / or hemicelluloses makes it possible to obtain a more intimate contact between the cellulose and / or hemicelluloses and the filling element used during step (2). Advantageously, step (2) of impregnation makes it possible to make the filling element penetrate into the cell wall of the lignocellulosic material. This results in a plasticization of the cellulose and / or hemicelluloses at the molecular level. Advantageously, thanks to this plasticization, at the end of step (2) of impregnation, 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 may be left empty or may be filled by the filler(s).

[0061] One or more fillers may be used during this impregnation step (2). This impregnation step may also be repeated at least once with fillers of the same or different nature from the first filler. Successive impregnation steps may complete the first impregnation by, for example, filling the lumens and providing other properties to the lignocellulosic material.

[0062] By "repeated at least once" we mean preferably repeated from 1 to 10 times, more preferably from 1 to 5 times, and even more preferably from 1 to 3 times.

[0063] The impregnation step (2) can be carried out with the filler element alone or via an impregnation vector such as a solvent allowing better diffusion of the filler element within the lignocellulosic material. The solvent used during the impregnation step can be identical to that used during the chemical treatment step (1) or identical to that used during the optional washing step.

[0064] Preferably, the filling compound is chosen for the affinities it develops with the elements of the lignocellulosic material so as to provide, for example, a plasticizing and / or reinforcing effect to the latter.

[0065] Advantageously, the filler compound is a compound capable of penetrating into the cell walls of the lignocellulosic material and having an affinity with the constituent polymers of the lignocellulosic material. Preferably, the filler compound has as many interactions as possible with the cellulose and / or hemicelluloses so as to plasticize it (them) and potentially with the other constituent elements of the lignocellulosic material such as lignin which it can also plasticize. Thus, any compound capable of associating, of creating interactions with the constituent elements of the cell wall of the lignocellulosic material, in particular cellulose and / or hemicelluloses, is preferred.

[0066] The filler compound may be selected from polymers, prepolymers, monomers, compounds derived from the hydrolysis of oxyranic compounds such as ethylene glycol, compounds derived from aziridine such as ethanolamine, compounds derived from the polymerization of oxyranic compounds such as polyethylene glycol, compounds derived from the polymerization of compounds derived from aziridine 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.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.

[0067] Examples of prepolymers include, but are not limited to, polyester diols, polycarbonate diols, polyalkadiene diols, epoxy resins, urethane prepolymers, and mixtures thereof.

[0068] Examples of monomers include, but are not limited to, oxyranic compounds, aziridinic compounds, methacrylic compounds, acrylic compounds, epoxies, urethanes, and mixtures thereof.

[0069] 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 derivatives thereof, and / or at least one organic or inorganic anion such as halides, tetrachloroaluminate, nitrates, hexafluorophosphate, tetrafluoroborate, sulfonates, sulfates, thiocyanates, dicyanamide, carboxylates or derivatives thereof, and mixtures thereof.

[0070] Examples of pyridinium salts include, but are not limited to, pyridinium ethyl chloride.

[0071] 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, dicyanamide, carboxylates or their derivatives, and mixtures thereof.

[0072] Examples of deep eutectic solvents include, but are not limited to, mixtures of a quaternary ammonium compound with a hydrogen bond donor compound.

[0073] Examples of quaternary ammoniums include, but are not limited to, choline chloride, chlorcholine chloride, betaines, ammonium chloride, and mixtures thereof.

[0074] Examples of hydrogen bond donor 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 thereof.

[0075] 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.

[0076] The ratio of filler compound to lignocellulosic material can vary depending on the desired properties.

[0077] Preferably, the filler 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 lignocellulosic material.

[0078] Impregnation step (2) may be followed by an optional drying step. Drying may be carried out following impregnation in the case of using an impregnation vector and / or to allow polymerization of the filler compound such as monomers. Drying may also prepare the lignocellulosic material for subsequent steps such as optional lamination.

[0079] Advantageously, at the end of the treatment steps (1) and (2) of impregnation, the lignocellulosic material exhibits an improvement in flexibility under tangential stress.

[0080] Advantageously, the mechanical treatment step (3) makes it possible to deconstruct the structure of the lignocellulosic material and in particular to shear the internal structure of the lignocellulosic material in order to soften it in the axial direction (grain direction). The impregnated filler element and the optional laminated material can make it possible to preserve the integrity of the lignocellulosic material. During this step, the hydrogen bond network present within the lignocellulosic material can be reorganized with the filler element.

[0081] Advantageously, step (3) of mechanical treatment impacts the biaxial flexibility of the material by microcracking of the structure at the mesoscopic scale, and by bringing the filling element and the structure closer together by creating bonds at the molecular scale.

[0082] The mechanical processing step may be selected from, but not limited to, padding, bending, calendering, laminating, embossing, blistering, emerizing, moiré, fulling, sanforizing, striking, staking, creasing, and combinations thereof, preferably calendering.

[0083] The heat treatment step may include exposing the material to a temperature between -50°C and 250°C.

[0084] Preferably, within the meaning of the present invention, the expressions "thermo-hygro-mechanical treatment" and "thermo-hydro-mechanical treatment" will be used interchangeably. By "thermo-hygro-mechanical treatment" or "thermo-hydro-mechanical treatment" is preferably meant a mechanical treatment of the material under controlled temperature and humidity conditions.

[0085] The mechanical and / or thermal and / or thermo-hygro-mechanical treatment step (3), preferably the mechanical treatment step (3), can be carried out before, during or after the optional additive addition step, before, during or after the optional drying step, before, during or after the optional laminating step and before, during or after the optional finishing step.

[0086] 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 is passed between 1 and 500 times, preferably between 20 and 450 times and more preferably between 50 and 400 times in the belt press. Preferably, the pressure applied by the cylinders of the belt press is between 0 and 20 bars, more preferably between 1 and 15 bars, and even more preferably between 2 and 10 bars.

[0087] Advantageously, during the process of the present invention, the internal mesoscopic structure of the lignocellulosic material is cracked so as to reduce the natural anisotropy of the lignocellulosic material without this having any consequence on the external appearance thereof. The mechanical treatment allows a more pronounced approximation of the filling element with the cellulose and / or the hemicelluloses of the lignocellulosic material which has (have) been made more accessible thanks to the chemical treatment. Advantageously, these two combined treatments result in an increase in the plasticizing effect of the filling element on the lignocellulosic material. This dual action of cracking and pressure thus makes it possible to obtain new flexural properties of the lignocellulosic material.

[0088] Preferably, the mechanical and / or thermal and / or thermo-hygro-mechanical treatment step, more preferably the mechanical treatment step, is distinct from the tests aimed at controlling the mechanical properties of the lignocellulosic composite material capable of being obtained by the process as defined previously.

[0089] An optional drying step may be carried out before, during and / or after one of the steps as defined previously, preferably before, during and / or after step (1) of partial hydration and / or partial dissolution, before, during and / or after step (2) of impregnation and / or before, during and / or after step (3) of implementation.

[0090] A portion of the cell wall components other than cellulose and / or hemicelluloses may be extracted during step (1).

[0091] Preferably, the method as defined above further comprises a step of partial delignification of the lignocellulosic material in order to obtain a partially delignified lignocellulosic material.

[0092] The amount of lignin extracted may 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. The optional partial delignification step may in particular make it possible to reduce the density of the lignocellulosic material and to extend the range of usable lignocellulosic materials. The reduction in the lignin content may also allow the lignocellulosic material to have more affinity with subsequent fillers.

[0093] The method as defined above may further comprise at least one step selected from the group consisting of a step of bleaching the lignocellulosic material, a step of partial or total extraction of the extractables and chromophores from the lignocellulosic material, a step of activation of the hydroxyl groups of the lignocellulosic material, a step of substitution of the hydroxyl groups of the lignocellulosic material, a step of oxidation of the lignocellulosic material, a step of reduction of the lignocellulosic material, a step of transformation of the lignocellulosic material such as slitting to reduce its thickness, and combinations thereof.

[0094] These steps may for example be carried out before, during or after the treatment step (1), and / or before, during or after the optional washing step (2) after the treatment step (1).

[0095] The method as defined above may further comprise an optional step of adding additives to the lignocellulosic material. This step of adding additives may be carried out by impregnation or by coating. This step may be carried out before, during and / or after one of the steps as defined above, preferably before, during and / or after step (1) of partial hydration and / or partial dissolution, before, during and / or after step (2) of impregnation and / or before, during and / or after step (3) of implementation.

[0096] Examples of additives include, but are not limited to, flame retardants, coloring agents, crosslinking agents, hydrophobic or waterproofing agents, surfactants, and mixtures thereof.

[0097] Examples of fire-fighting agents include, but are not limited to, halogenated compounds and their derivatives, phosphorus compounds and their derivatives, metal oxides and their derivatives, metal hydroxides and their derivatives, boron-based compounds and their derivatives, and mixtures thereof.

[0098] Examples of halogenated compounds and their derivatives include, but are not limited to, chlorinated or brominated paraffins, polybrominated diphenyl ethers, hexabromocyclododecane, tetrabromobisphenol A, polybrominated biphenyls, decabromodiphenyl ether, and mixtures thereof.

[0099] Examples of phosphorus compounds and their derivatives include, but are not limited to, organic phosphates, inorganic phosphates, inorganic phosphates, and mixtures thereof.

[0100] Examples of metal oxides and their derivatives include, but are not limited to, antimony oxides. Examples of metal hydroxides and their derivatives include, but are not limited to, aluminum hydroxide, magnesium hydroxide, and mixtures thereof.

[0101] Examples of boron-based compounds and their derivatives include, but are not limited to, boric acid, zinc borate, and mixtures thereof.

[0102] Examples of coloring agents include, but are not limited to, organic pigments, inorganic pigments, organic dyes, and mixtures thereof.

[0103] Examples of organic pigments include, but are not limited to, perylene, quinacridones, phthalocyanines, indigo, sepia, carmine, and mixtures thereof.

[0104] Examples of inorganic pigments include, but are not limited to, metal oxides, cinnabar, Guimet blue, ochre, cobalt blue, titanium white, zinc white, cadmium yellow, and mixtures thereof.

[0105] Examples of organic dyes include, but are not limited to, azo dyes, anthraquinone dyes, triarylmethane dyes, chlorine dyes, polymethine dyes, and mixtures thereof.

[0106] Examples of crosslinking agents include, but are not limited to, crosslinking agents having a functionality of at least 2 such as polyepoxides, polyacids, alkoxysilanes, and mixtures thereof.

[0107] Examples of polyepoxides include, but are not limited to, diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, diepoxyoctane, diepoxybutane, and mixtures thereof.

[0108] Examples of polyacids include, but are not limited to, malonic acid, tartaric acid, citric acid, succinic acid, fumaric acid, oxalic acid, isophthalic acid, phosphoric acid, and mixtures thereof.

[0109] Examples of alkoxysilanes include, but are not limited to, methyltrimethoxysilane, tetraethoxysilane, tetramethoxysilane, phenyltrimethoxysilane, and mixtures thereof.

[0110] Examples of hydrophobic or waterproofing agents include, but are not limited to, fats, oils, waxes, silica particles such as silica nanoparticles, and mixtures thereof.

[0111] Examples of surfactants include, but are not limited to, penetrating agents, solubilizing agents, wetting agents, dispersing agents, emulsifying agents, and mixtures thereof.

[0112] The method as defined above may further comprise a step of laminating a material, preferably a flexible material, onto the lignocellulosic material or a step of laminating said lignocellulosic composite material onto itself in order to obtain a reinforced material. The laminated material may be chosen from, but not limited to, a textile, an untanned or tanned skin such as leather, rubber, latex, a foam, another composite material different from the composite material obtained, and a mixture thereof.

[0113] This laminating step may 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).

[0114] In this optional lamination step, the material can be laminated to a flexible element to maintain the flexibility acquired during the impregnation step (2) while providing an improvement in the mechanical strength of the material such as tear resistance. However, the lignocellulosic material can be used without an additional lamination step, as its strength may be sufficient for many applications.

[0115] This optional lamination can be permanent or temporary depending on whether the reinforcing material must be present or not in the final material or whether recycling of the material is envisaged.

[0116] This optional lamination can be carried out before or after the optional step of transforming the material such as slitting to reduce its thickness.

[0117] Preferably, the glue used in the laminating step does not alter the flexibility of the material and can be used despite the changes made by the chemical treatment step (1) and the impregnation step (2) with the filling compound.

[0118] Examples of adhesives that may 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-sealing films, and mixtures thereof.

[0119] The method as defined above may comprise at least one finishing step comprising the coating of one or more faces of the material with a protective agent and / or a step of physical or chemical treatment of one or more faces of the material.

[0120] 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 combinations thereof.

[0121] Advantageously, the finishing step makes it possible to protect the material by an element allowing it to provide surface properties such as coloring, texture, mechanical strength (scratch resistance), UV resistance, hydrophobicity (humidity resistance) and / or fire resistance, preferably coloring, mechanical strength (scratch resistance), UV resistance and / or hydrophobicity (humidity resistance). This finishing step can also make it possible to limit the exudation of the filling element over time. This step is optional in the sense that protection can also be provided by the filling element 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 depositing a varnish, by coating or by chemical modification of the surface of the lignocellulosic material.For example, to improve UV resistance, UV absorbers may be added during the optional finishing step and / or antioxidants may be present in the filler element.

[0122] Advantageously, the finish provided allows the flexibility provided to the material to be retained.

[0123] Advantageously, following the processing operations and before or after the application of the finish, the wood is made sufficiently flexible to undergo processing operations not normally feasible on wood. The material thus obtained can, for example, be split down to very thin thicknesses.

[0124] Advantageously, the initial architecture of the lignocellulosic material is preserved at the end of step (1) of partial hydration and / or partial dissolution, and / or at the end of step (2) of impregnation, preferably the initial architecture of the lignocellulosic material is preserved at the mesoscopic scale at the end of step (1) of partial hydration and / or partial dissolution, and / or at the end of step (2) of impregnation.

[0125] Preferably, said lignocellulosic material is wood.

[0126] The wood may be green wood, wet wood or dry wood as defined in WO2017098149 (A1) or in WO2018224598 (A1). For example, the wood may be wood used after possible storage for a more or less long period (a few days to a few years). This wood may have been transformed after felling, i.e., have been cut, sawn, planed, freed from its bark, sapwood or heartwood, or be engineered wood. It may also be aged wood, i.e., wood that has already been used, for example, construction timber. This wood may come from various species and essences such as those defined in WO2017098149 (A1) or in WO2018224598 (A1). This wood may have undergone physical or chemical treatment.

[0127] The lignocellulosic material can, for example, be in the form of a sheet, board, plate or solid wood veneer.

[0128] The method of the present invention can be carried out on all cutting orientations of the lignocellulosic material, preferably in the longitudinal, tangential and / or radial direction of the lignocellulosic material.

[0129] Advantageously, the method of the present invention is a method for obtaining a lignocellulosic composite material having biaxial flexibility, preferably at room temperature, and even more preferably permanent at room temperature.

[0130] Advantageously, the method of the present invention is a method for obtaining a lignocellulosic composite material having biaxial flexibility, preferably at room temperature, and even more preferably permanent at room temperature, improved compared to the starting lignocellulosic material.

[0131] The present invention also relates to a lignocellulosic composite material capable of being obtained by the process as defined above.

[0132] Preferably, said material as defined above has biaxial flexibility.

[0133] Preferably, said material as defined above has biaxial flexibility at room temperature.

[0134] Preferably, said material as defined above has permanent biaxial flexibility at room temperature.

[0135] Surprisingly and unexpectedly, the present inventors have found that the process as defined above makes it possible to obtain a lignocellulosic material having permanent biaxial flexibility at room temperature. In particular, all of steps (1) to (3) make it possible to eliminate the natural resistance of the lignocellulosic material to folding without loss of mechanical properties and to obtain a lignocellulosic material having a natural appearance and feel. Advantageously, the process according to the present invention is easy to implement.

[0136] By "biaxial flexibility" we preferably mean the maximum deformation that can be brought to the material before its plastic deformation.

[0137] Preferably, the material as defined above has a biaxial radius of curvature of 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.

[0138] Thus, advantageously, the material as defined previously has a radius of curvature much smaller than that of the initial material, particularly in the longitudinal direction.

[0139] Preferably, the material as defined above has a thickness of 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.

[0140] Preferably, the material as defined above has resistance to repeated bending.

[0141] Preferably, the material as defined above has a tensile strength identical to or greater than that of the initial lignocellulosic material.

[0142] Preferably, the material as defined above has a friction resistance identical to or greater than that of the initial lignocellulosic material.

[0143] 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.

[0144] 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 lignocellulosic material.

[0145] Preferably, the material as defined above has a capacity to be sewn, a capacity to be slit, and a capacity to be trimmed, unlike the natural lignocellulosic material.

[0146] The present invention also relates to a lignocellulosic composite material as defined previously as such.

[0147] The present invention also relates to the use of the material as defined above, for the manufacture of parts, containers, coatings or surfaces.

[0148] 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.

[0149] DESCRIPTION OF FIGURES

[0150] Figure 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 in Example 1.

[0151] Figure 2: Diagram showing the tangential radius of curvature of the material obtained after each step of the process of example 1 compared to the initial material used.

[0152] Figure 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.

[0153] EXAMPLES

[0154] Example 1:

[0155] Step 1: Chemical Treatment

[0156] In a glass reactor, a mass of 45 g of sodium hydroxide is dissolved in 450 g of distilled water at 5°C while stirring. After dissolving the sodium hydroxide, a mass of 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.

[0157] The temperature of the solution is brought back to 10°C. A sycamore maple veneer sheet 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.

[0158] The sycamore maple leaf is then removed from this medium and placed in a distilled water bath at 35°C for 30 minutes. This operation is repeated 3 times to obtain a neutral pH.

[0159] Step 2: Impregnation

[0160] The chemically treated wood sheet is then immersed in a 50% solution of polyethylene glycol 400 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.

[0161] Step 3: Mechanical treatment

[0162] The impregnated wood sheet is then fed into a belt press consisting of 10 rollers of 25 cm diameter with a pressure of 5 bars. The wood sheet thus obtained has biaxial flexibility and can be deformed repeatedly without the sheet being broken.

[0163] The radius of curvature was measured by rods of decreasing diameters on rectangular specimens of 100 mm by 50 mm.

[0164] The breaking stress was measured by a tensile machine (Testometric X350) according to the ISO 527 method.

[0165] The characteristics of the obtained material are presented in Table 1 and Figures 1 to 3.

[0166] Table 1]

Claims

CLAIMS Method 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 with at least one filling compound of the lignocellulosic material resulting from step (1), and - a step (3) of using the lignocellulosic material from step (2), said method comprising a step of in-situ regeneration of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2). Method for manufacturing a lignocellulosic composite material according to claim 1, characterized in that: - step (1) is a step of chemical treatment of a lignocellulosic material making it possible to hydrate and / or partially dissolve the cellulose and / or hemicelluloses present in the lignocellulosic material, - step (2) is a step of impregnation with at least one filling compound of the lignocellulosic material resulting from step (1), and - step (3) is a step of implementation by mechanical and / or thermal and / or thermo-hygro-mechanical treatment, preferably by mechanical treatment, of the lignocellulosic material resulting from step (2), said method comprising a step of in-situ regeneration of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2). Method for manufacturing a lignocellulosic composite material according to claim 1 or 2, characterized in that: - step (1) is a step of chemical treatment of a lignocellulosic material using at least one solvent chosen from non-derivatizing aqueous solvents, non-aqueous non-derivatizing solvents, derivatizing solvents, and mixtures thereof, making it possible to hydrate and / or partially dissolve the cellulose and / or hemicelluloses present in the lignocellulosic material, - step (2) is a step of impregnation with at least one filling compound of the lignocellulosic material resulting from step (1) so as to plasticize the cellulose and / or the hemicelluloses present in the lignocellulosic material, and - step (3) is a step of implementation by mechanical and / or thermal and / or thermo-hygro-mechanical treatment, preferably by mechanical treatment, of the lignocellulosic material resulting from step (2) aimed at destructuring the internal structure of the lignocellulosic material, said method comprising a step of in-situ regeneration of the cellulose and / or hemicelluloses at the end of step (1) and / or during the impregnation step (2). Method according to any one of claims 1 to 3, characterized in that the filling compound is chosen from polymers, prepolymers, monomers, compounds resulting from the hydrolysis of oxyranic compounds such as ethylene glycol, compounds derived from aziridine such as ethanolamine, compounds resulting from the polymerization of oxyranic compounds such as polyethylene glycol, compounds derived from aziridine 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.Process according to claim 3 or 4, characterized in that the non-derivatizing aqueous solvent is chosen from aqueous solutions of transition metal complexes such as cuprammonium hydroxide, cupriethylenediamine hydroxide and their mixtures, 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 their mixtures, aqueous solutions of salts such as zinc chloride, lithium chloride, sodium chloride and their mixtures, aqueous solutions of urea and its derivatives such as thiourea, and their mixtures.A method according to any one of claims 3 to 5, characterized in that the non-aqueous non-derivatizing solvent is chosen from ionic liquids, poly(ionic liquids), organic solvents such as methylmorpholine oxide, dimethylacetamide, ammonia, dimethylsulfoxide, deep eutectic solvents, and mixtures thereof. A method according to any one of claims 2 to 6, characterized in that the mechanical treatment step is chosen from padding, bending, calendering, laminating, embossing, blistering, emerizing, moiré, fulling, sanforizing, striking, staking, crumpling, and combinations thereof, preferably calendering.Method according to any one of claims 1 to 7, characterized in that it further comprises at least one step chosen from the group consisting of a step of bleaching the lignocellulosic material, a step of partial or total extraction of the extractables and chromophores from the lignocellulosic material, a step of activation of the hydroxyl groups of the lignocellulosic material, a step of substitution of the hydroxyl groups of the lignocellulosic material, a step of oxidation of the lignocellulosic material, a step of reduction of the lignocellulosic material, a step of transformation of the lignocellulosic material, and combinations thereof. Method according to any one of claims 1 to 8, characterized in that it further comprises a step of laminating a material onto the lignocellulosic material or a step of laminating said lignocellulosic composite material onto itself in order to obtain a reinforced material.Lignocellulosic composite material obtainable by the process as defined according to any one of claims 1 to 9. Material according to claim 10, characterized in that it has biaxial flexibility at room temperature.

12. Use of the material as defined according to claim 10 or 11, for the manufacture of parts, containers, coatings or surfaces.

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