Process for preparing a thermoplastic cellulosic material

Abstract

The invention relates to a thermoplasticizing process for a cellulosic material, said process comprising: contacting a fatty acid (FA) with trifluoroacetic anhydride (TFAA); and esterifying a cellulosic material by reaction with the mixed anhydride obtained in step i), thereby obtaining a thermoplastic cellulosic material, steps i) and ii) being carried out in the absence of solvent, in particular at room temperature. Figure for the abstract: none

Description

Title of the invention: Process for preparing a thermoplastic cellulose material Scope of the invention

[0001] The invention relates to a thermoplasticizing process for a cellulosic material. It also relates to the thermoplastic cellulosic material obtainable by this process, its implementation in a hot forming process, and the hot-formed cellulosic material obtainable by this process. Technical background

[0002] The plastics currently in use largely rely on petrochemical resources, which generate significant greenhouse gas emissions. Furthermore, some plastics are difficult to biodegrade, causing significant environmental problems.

[0003] In order to limit this environmental impact, wood-based composite materials with thermoplastic properties have recently been developed. These composite materials consist of mixtures of wood powders with various thermoplastic matrices (PE, PP, PVC), which are shaped using conventional extrusion techniques, among others.

[0004] However, these composite materials, whose thermoplastic properties result primarily from the presence of a thermoplastic matrix, remain mainly composed of petroleum-based polymers, and therefore allow only a very limited reduction in CO2 emissions into the environment related to their manufacture. Furthermore, these composite materials remain difficult to biodegrade.

[0005] There is therefore a real need for thermoplastic materials mainly made up of renewable resources, as a replacement for materials of fossil origin, in order to reduce the impact of plastics on the environment. Summary of the invention

[0006] A process has now been developed for imparting thermoplastic properties to a cellulosic material, such as wood. More specifically, the inventors have discovered that by esterifying the hydroxyl groups of a cellulosic material with fatty acids having saturated or unsaturated hydrocarbon chains, particularly according to a specific esterification ratio, it is possible to modify the native properties of the cellulosic material, in particular to decrease its crystallinity and to impart thermoplastic properties to it.

[0007] Thus, by way of example, the inventors were able to observe that the crystallinity index (Cri) of wood esterified according to the process of the invention could be between 3% and 25% depending in particular on the nature of the fatty acid used in the esterification reaction, whereas that of the same native wood, not esterified, was around 42%.

[0008] Advantageously, the thermoplasticization process can be carried out under mild conditions, in particular without solvents and advantageously at ambient temperature, thereby limiting the environmental impact and the economic cost associated with implementing the process. According to another advantage, the trifluoroaceric anhydride used in this process or the trifluoroacetic acid generated during the process can be recovered and recycled, in particular reused in the process.

[0009] These new materials are particularly advantageous economically and ecologically since they can be obtained from abundant and renewable raw materials, namely fatty acids and cellulosic materials, thus limiting the use of petrochemical compounds.

[0010] According to another advantage, the thermoplastic cellulosic materials that can be obtained by this process are characterized, after hot forming, in particular by pressing, by a first softening temperature (Ti), that is to say the lowest softening temperature, relatively low compared to that of the same non-esterified cellulosic material, in particular between 40 and 200°C, more particularly between 120 and 190°C, which makes it possible to limit the temperature to be used during the hot forming process and thus the risk of degradation of the cellulosic material, while also promoting its recycling.

[0011] Advantageously, the hot-formed materials obtained from thermoplastic cellulosic materials are 100% bio-based and do not contain plasticizers or thermoplastic polymers derived from petrochemicals.

[0012] According to another advantage, the hot-formed material exhibits isotropy of appearance, making the initial cellulosic material particles invisible. It generally displays the suppleness, flexibility, and characteristics of a translucent, thermoplastic material.

[0013] By "isotropic appearance", we mean a material exhibiting overall homogeneity throughout

[0014] By “flexibility” we mean a material having sufficient elasticity to allow it to deform reversibly.

[0015] By “flexibility” is meant a flexible material that can be easily bent or folded.

[0016] By "translucent" is meant a material which, when light passes through it, diffuses some of the light rays, generally due to irregularities in its surface. Conversely, opaque materials (unmodified sawdust) which stop all the light rays.

[0017] According to a first aspect, the invention relates to a thermoplasticizing process for a cellulosic material, said process comprising:

[0018] i. Contacting a fatty acid (FA) with trifluoroacetic anhydride (TFAA); and ii. Esterification of a cellulosic material by reaction with the mixed anhydride obtained in step i), thereby obtaining a thermoplastic cellulosic material,

[0019] steps i) and ii) being carried out in the absence of solvent, in particular at room temperature.

[0020] According to embodiments, the process according to the invention comprises one or more of the following additional features:

[0021] - the cellulosic material further comprises lignin and / or hemicelluloses; - the cellulosic material comprises at least 20%, in particular 30%, in particular 40% by weight of cellulose; - The cellulosic material comprises:

[0022] - 40 - 60% by weight of cellulose, - 20-40% hemicelluloses, and - 10-25% lignin;

[0023] - the cellulosic material is chosen from wood, plants, or mixtures thereof; - the cellulosic material used in step i) is in the form of powders, raw or woven fibers or in solid form; - the cellulosic material is wood, particularly in powder form or in solid form; - fatty acid (FA) is a saturated or unsaturated fatty acid, such as propionic acid, butyric acid, crotonic acid, isovaleric acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and oleic acid; - the molar ratio of the AG / TFAA reactants is between 0.8 and 1.2 and is preferably equal to 1; - step i) is carried out for a period of less than 1 hour, in particular a period of 30 minutes; - the mass proportion of TFAA implemented in step i) compared to the cellulosic material implemented in step ii) varies from 4 / 1 to 2 / 1; - step ii) of esterification is carried out for a period of less than 4 hours; - the thermoplastic cellulosic material obtained in step ii) is subjected to a purification process comprising the following steps: - washing the thermoplastic cellulose material with a hydroalcoholic mixture; and - drying of the washed thermoplastic cellulosic material until an anhydrous thermoplastic cellulosic material is obtained.

[0024] According to a second aspect, the invention relates to a thermoplastic cellulosic material that can be obtained by the process according to the invention.

[0025] In some embodiments, the thermoplastic cellulosic material is a material in which:

[0026] - the esterification rate is between 5 and 15 mmol of ester / g of cell material lulosic, in particular between 6 and 12 mmol of ester / g of cellulosic material; and / or

[0027] - the degree of crystallinity is at least 30% lower than that of the cellulosic material native and / or is between 3 and 25%.

[0028] According to a third aspect, the invention relates to the use of a thermoplastic cellulosic material according to the invention, in a hot forming process.

[0029] In embodiments, the forming process includes a pressing step, in particular carried out at a temperature between 120 and 200°C, and / or at a pressure between 10 MPa and 15 MPa.

[0030] According to a fourth aspect, the invention relates to a hot-formed cellulosic material comprising a thermoplastic cellulosic material according to the invention.

[0031] In some embodiments, the hot-formed cellulosic material is characterized by:

[0032] - a first softening temperature between 40°C and 200°C, in particular between 120°C and 200°C; and / or - a density between 1 and 1.5 g / cm3. Brief description of the figures

[0033] [Fig-1] shows the evolution of the mass gain (MG) of the esterification reaction of wood powder with different fatty acids as a function of reaction time

[0034] [Fig.2] shows the evolution of the mass gain at the end of step ii) as a function of the amount of TFAA implemented in step i)

[0035] [Fig.3] shows the appearance of woods esterified with different hot-pressed fatty acids (A), of woods esterified with different pressing temperatures (B), the flexibility of wood grafted with myristic acid (C), as well as the appearance of unmodified wood (D) hot-pressed, light passes through when there is nothing in front (E), part of the light passes through in front of a film of esterified wood, translucent material (F), light does not pass through in front of native wood, opaque material (G).

[0036] [Fig.4] presents an image of unmodified wood pressed at 200°C (A) and an image of wood grafted with myristic acid pressed at 140°C with a mass gain of 214.7% (B), these images being obtained by scanning electron microscopy.

[0037] [Fig.5] represents the contact angle of the hot-formed cellulosic material obtained from unmodified wood powder on the one hand and esterified with different fatty acids on the other hand.

[0038] [Fig.6]: Curves showing softening temperatures

[0039] of wood esterified by different fatty acids

[0040] [Fig.7]: X-ray diffraction analysis of unmodified and esterified wood powder with different fatty acids

[0041] [Fig.8]: Recyclability of hot-formed esterified wood Detailed description

[0042] The invention is now described in more detail and in a non-limiting manner in the following description.

[0043] Unless otherwise indicated, percentages are expressed by weight. In particular, the weight of the cellulosic material refers to the weight of the dry material, i.e., containing less than 1% water.

[0044] Thermoplasticization process for a cellulosic material

[0045] Thus, according to a first aspect, the invention relates to a thermoplasticization process for a cellulosic material, said process comprising:

[0046] i. Contacting a fatty acid (FA) with trifluoroacetic anhydride (TFAA); and ii. Esterification of a cellulosic material by reaction with the mixed anhydride obtained in step i), thereby obtaining a thermoplastic cellulosic material,

[0047] steps i) and ii) being carried out in the absence of solvent, in particular at room temperature.

[0048] By "thermoplasticization" we mean a process for converting a cellulosic material into a thermoplastic material.

[0049] By "ambient temperature" is meant a temperature generally between 15 and 25°C, in particular between 20 and 24°C.

[0050] According to some embodiments, the cellulosic material further comprises lignin and / or hemicelluloses. The cellulosic material may comprise at least 20%, in particular 30%, and in particular 40% by weight of cellulose. In particular, the cellulosic material may comprise:

[0051] - 40 - 60% by weight of cellulose, - 20-40% by weight of hemicelluloses, and - 10-25% by weight of lignin.

[0052] The cellulosic material can be chosen from wood, plants, or mixtures thereof.

[0053] The cellulosic material used in step i) can be in the form of powders, raw or woven fibers or in solid form.

[0054] According to some embodiments, the cellulosic material is hemp or flax.

[0055] According to a preferred embodiment, the cellulosic material is wood, in particular It is typically available in powder form or in solid form. It can be derived from a specific type of wood such as spruce, poplar, oak, beech, fir, Douglas fir, or pine. It can also be a mixture of wood species, particularly in powder form.

[0056] The fatty acid (FA) implemented in step i) can be a saturated or unsaturated fatty acid, such as propionic acid, butyric acid, crotonic acid, isovaleric acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, or a mixture thereof.

[0057] The molar ratio of the AG / TFAA reactants can be between 0.8 and 1.2 and is preferably equal to 1.

[0058] According to some embodiments, step i) is carried out for a period of less than 1 hour, in particular a period of 30 minutes.

[0059] The mass proportion of TFAA implemented in step i) relative to the cellulosic material implemented in step ii) can vary from 4 / 1 to 2 / 1.

[0060] According to embodiments, the esterification step ii) is carried out for a period of less than 4 hours.

[0061] The thermoplastic cellulosic material obtained in step ii) can then be subjected to a purification process comprising the following steps:

[0062] - Washing the thermoplastic cellulosic material with a hydroalcoholic mixture; and - drying of the washed thermoplastic cellulosic material until an anhydrous thermoplastic cellulosic material is obtained.

[0063] The TFAA and TFA that did not react in step i) or were released during the esterification reaction of the hydroxyl groups of the cellulosic material in step ii) can advantageously be recovered and reused in the thermoplasticizing process according to the invention. It can be recovered, in particular, by distillation. Thermoplastic cellulosic material

[0064] According to a second aspect, the invention relates to a thermoplastic cellulosic material that can be obtained by the process as defined above.

[0065] According to further embodiments, the esterification rate of the thermoplastic cellulosic material is between 5 and 15 mmol of ester / g of cellulosic material. lulosic, in particular between 6 and 12 mmol of ester / g of cellulosic material.

[0066] According to further embodiments, the thermoplastic cellulosic material is characterized in that its degree of crystallinity is at least 30% lower, in particular 40% to 90% lower, than that of the native cellulosic material.

[0067] By "crystallity rate", or "crystallity index", also denoted Cri, is meant the relative degree of crystallinity of the cellulosic material measured by X-ray diffraction according to the method described by Segal et al. in the publication: Segal, L., Creely, L., Martin, AE, Conrad, CM, 1959. An empirical method for estimating the degree of crystallinity of native cellulose using X-ray diffractometer. Text. Res. J. 29, 786-794.

[0068] The degree of crystallinity of the thermoplastic cellulosic material can be in particular between 3 and 25%.

[0069] Use of a thermoplastic cellulosic material in a hot forming process

[0070] According to a third aspect, the invention relates to the use of a thermoplastic cellulosic material according to the invention, in a hot forming process.

[0071] The term "hot forming" refers to a process in which a material is heated to soften it, and this ductility is then used to shape it with a mold. The material hardens again upon cooling, retaining this shape.

[0072] The hot forming process may include, in particular, a hot pressing process, including a pressing step.

[0073] The hot pressing conditions can vary depending on the dimensions of the hot-formed cellulosic material that one wishes to obtain, in particular its thickness.

[0074] By way of example, hot pressing can be carried out at a temperature between 120 and 200°C, and / or at a pressure between 10 MPa and 15 MPa.

[0075] Hot-formed thermoplastic cellulosic material

[0076] According to a fourth aspect, the invention relates to a hot-formed cellulosic material comprising a thermoplastic cellulosic material as defined above.

[0077] The cellulosic material may in particular have a density of between 1 and 1.5 g / cm3.

[0078] According to embodiments, the first softening temperature of the hot-formed thermoplastic cellulosic material is between 40°C and 200°C, in particular between 120°C and 200°C. Examples

[0079] Example 1: Esterification of spruce wood powder according to the process of the invention

[0080] The hydroxyl groups of spruce wood have been functionalized with different fatty acids. The reaction scheme is as follows: O .... I GG M o cpj WM 53. SSOMG OG R” V "«G G WA WiS—OK G TOS ««GM X; R > OG <• mG"< CL cr3 = 5 A

[0081] Scheme 1: Esterification of spruce wood powder by fatty acids

[0082] using TF AA

[0083] The esterification of wood powder by fatty acids is carried out using trifluoroacetic anhydride (TFAA) as an activating agent or propellant or facilitator (Scheme 1).

[0084] The materials obtained were characterized by measuring the mass gain (MG), determining the characteristics of the chemical structure by FTIR and NMR analysis, the thermal properties by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the adhesive properties / molding capacity of the esterified powder by hot pressing, the surface properties of the pressed esterified wood by measuring the contact angle, the morphological properties by scanning electron microscopy (SEM) and the thermoplastic properties by thermomechanical analysis (TMA) and X-ray diffraction (XRD).

[0085] For the calculation of mass gain (GM), reference may be made to the following publication: Philippe Gerardin et al. Wood Science and Technology (2020) 54:479-502.

[0086] Spruce (Picea abies) sawdust was used after Soxhlet extraction for 4 h with a toluene / ethanol mixture in the proportions of (2:1), and then again for 4 h with ethanol. The sawdust was then dried at 103°C for 24 h. The sawdust used in the esterification process is therefore anhydrous, so the quantities of wood expressed below, before treatment, refer to the dry material.

[0087] Different fatty acid chain lengths were used, ranging from C4 to Cl8 for saturated fatty acids. For unsaturated fatty acids, crotonic acid (C4) and oleic acid (Cl8) were used.

[0088] More specifically, a fatty acid was mixed with TFAA in a molar ratio (1:1) without solvent at room temperature to form a mixed anhydride. Kiln-dried wood powder was then added to the mixed anhydride in Wood / TFAA proportions of (1:4) (w / w) relative to the amount of TFAA used in step i), for different reaction times (15 min–24 h) in a closed system. The wood esterified products were successively washed with ethanol and water followed by soxhlet extraction in an ethanol / water mixture (2:1) for 24 h, changing the solvent mixture as much as possible to remove TFA formed during the esterification reaction or residual TF AA.

[0089] The sample obtained is then dried at 103°C for 24 h, and the mass gain (MG) was calculated.

[0090] More particularly, after treatment of the spruce sawdust, the mass gain (GM) was determined gravimetrically according to the equation: GM = [(ml-m0) / mO] X 100 with mO = mass of the anhydrous spruce sawdust before treatment, ml = mass of the anhydrous spruce sawdust after treatment.

[0091] After treatment, the experimental mass gain (GM) is determined gravimetrically according to the equation: GM = [(mrmo) / m0] x 100, where m0 = mass of the anhydrous sawdust before treatment, and mi = mass of the anhydrous sawdust after treatment. The increase in mass gain (GM) reflects the grafting of fatty acids by esterification of the hydroxyl groups in the wood and allows the esterification rate of the wood by the fatty acid to be determined by dividing the mass gain by the molar mass M of the corresponding grafted acyl group for a given fatty acid.

[0092] The esterification rate reflects the ester content and also represents the number of ester functions grafted in milliequivalents (meq.) per gram of wood according to the following formula: (Mass gain) / (M(grafted group)) X 1000.

[0093] Figure 1 describes the grafting of different fatty acids onto wood using varying reaction times (15 min - 24 hours). After 15 minutes of reaction, the ester content already reaches 7.6 - 9.9 mmol of ester / g of wood; after 1 hour of reaction, it is greater than 10 mmol of ester / g of wood and begins to stabilize, remaining stable until 24 hours of reaction.

[0094] Therefore, these results show that the esterification reaction of wood by fatty acids according to the process of the invention is very rapid since the esterification rate reaches a maximum after only 15 minutes of reaction.

[0095] The esterification of wood powder with different amounts of fatty acid and trifluoroacetic anhydride (TFAA) relative to the mass of wood used was studied ([Fig.2]), the amount of TFAA relative to AG remaining constant and equal to 1 molar equivalent.

[0096] The results show that the mass gain (MG) of the esterified wood increases when the mass ratio of TFAA to wood varies from 1:1 to 4:1. The mass gain stabilizes for TFAA / wood ratios greater than 4:1. These results show that the accessibility of the hydroxyl groups of wood by different fatty acids is approximately 10 to 11 mmol of ester / g of wood maximum.

[0097] Example 2: Characterization of the chemical and structural properties of esterified woods

[0098] Fonder transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) analysis were performed to understand the chemical and structural changes in wood before and after esterification.

[0099] Fourier transform infrared (FTIR) spectroscopy shows that the absorption band of the OH vibration (3500–3300 cm⁻¹) in the unmodified wood disappeared in the esterified wood, with a significant increase in the intensity of the CH and CH₂ groups (2918 and 2848 cm⁻¹) and the C=O ester (1743 cm⁻¹) observed in the esterified wood. The longest fatty chain that esterified the wood with a high mass gain (GM) showed a higher intensity of these CH groups, while the C=O ester showed the same intensity in all the esterified woods.

[0100] The NMR spectrum of the solid obtained with unmodified wood shows a characteristic carbohydrate profile, as evidenced by: Cl (102.0 ppm), C4 (88.0 ppm), C2, C3, C5 (73.4 ppm), and C6 (65.0 ppm). After esterification with myristic acid, the peak at 88.0 ppm (C4 of crystalline cellulose) disappears, and the intensities of the peaks at 102.0 ppm (Cl of hemicellulose) and 73.4 ppm (C-2 / C-3 / C-5 of cellulose) decrease and shift to 64.2 ppm (C-6 amorphous cellulose). A new peak also appears in the esterified wood at 14.6–30 ppm, corresponding to methyl and methylene groups, and at 172.7 ppm, corresponding to the C=O ester.

[0101] The change in chemical structure observed in FTIR and NMR shows that fatty acids grafted onto wood play an important role in obtaining a thermoplastic wood powder from the decrystallization of cellulose created by grafting fatty acids onto wood.

[0102] Example 3: Characterization of the thermal properties of esterified woods

[0103] The thermal properties of esterified wood were observed by performing thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results obtained by TGA show that the degradation temperature of the wood increases when the wood is esterified. The degradation temperature (midpoint) of unesterified wood is 351°C, and that of esterified wood is between 362 and 379°C. The results obtained by DSC confirm the degradation temperature obtained by TGA; more specifically, they describe that the degradation of esterified wood occurs through endothermic and exothermic phenomena.

[0104] Example 4: Characterization of the plastic appearance of esterified wood (Press and microscopy)

[0105] Spruce sawdust, esterified with different fatty acids according to the process of the invention, was hot-pressed at 200°C for 10 minutes under a pressure of 10 MPa. Translucent sheets were obtained, regardless of the fatty acids used (Figure 3A), unlike the sheet obtained under the same conditions by pressing unesterified sawdust, which has an opaque appearance (Figure 3D).

[0106] Furthermore, Figure 3B shows that when the pressing of spruce sawdust, esterified by myristic acid, is carried out at a temperature below 200°C, in particular between 120°C and 200°C, sheets with a plastic appearance that are still translucent, but of a lighter shade, are obtained.

[0107] Furthermore, Figure 3C shows that the sheets obtained are flexible when folded over themselves, and therefore exhibit thermoplastic properties.

[0108] The fibrous structure of hot-pressed, unmodified spruce sawdust was observed by scanning electron microscopy ([Fig. 4]). After esterification, this fibrous structure disappears due to the apparent melting of the wood fibers. The esterified wood appears more compact and less fibrillar, indicating the thermal melting of the wood.

[0109] Example 5: Characterization of the surface properties of esterified woods

[0110] The measurement of the contact angle of the pressed sheet spruce wood before and after es Esterification was observed to understand the surface properties of esterified woods.

[0111] Figure 5 shows that before esterification of the wood, the water droplets form a small contact angle immediately after the start of the measurement. After esterification of the wood with different fatty acid chain lengths, the contact angle varies from 69.3° to 96.8° at the start of the measurement and from 65.1° to 92.7° after 60 seconds of measurement. These results show that esterification of the wood with different fatty acids renders the surface of the material hydrophobic.

[0112] Example 6: Thermomechanical analysis of esterified wood

[0113] The thermal softening properties of esterified wood were observed using a thermomechanical analyzer (TMA).

[0114] A sample of pressed esterified wood was compressed under a constant load of 0.1 N in a chamber heated from 30 to 280°C at a heating rate of 10°C / min. As the temperature increased, the load shifted and recorded the deformation. The maximum deformation value is then considered to be the softening temperature.

[0115] Figure 6 and Table 1 show the thermal softening phenomena of esterified wood with different fatty acid chains compared to unmodified spruce sawdust. Unmodified spruce sawdust exhibits only one softening temperature at 221.47°C. When the spruce sawdust was esterified with fatty acids, the first deformation occurred early. This phenomenon has been termed TL1. There is a tendency for the longer the grafted fatty acid, the lower the resulting T1. The second softening temperature (T2) was observed in all esterified woods, while the third softening temperature (T3) was observed from fatty acids with 5 to 18 carbon atoms. Softening Temperature Treatment (°C) T1 T2 T3 Unmodified Sawdust 221.47 C3 Sawdust 196.8 266.42 C4 Sawdust 125 199.03 C5 Sawdust 113.18 141.49 283.88 C8 Sawdust 58.52 178.72 280.98 C10 Sawdust 72.54 187.46 257.94 C12 Sawdust 61.9 181.42 250.21 C14 Sawdust 62.57 173.88 250.12 C16 Sawdust 56.47 171.61 245.43 C18 Sawdust 55.88 164.87 266.81

[0116] Table 1: Softening temperatures of esterified wood

[0117] Example 7: Analysis of esterified wood by X-ray diffraction

[0118] Diffraction patterns were obtained directly on modified and unmodified wood powder. The setup used included a SEIFERT XRD-3000 generator operating at 40 kV, 30 mA, and in a Bragg-Brentano (0 / 0) geometry. CuKal radiation was selected from a copper source using a graphite monochromator at a wavelength h = 0.1540598 nm. Diffraction patterns were recorded for θ angles between 1 and 30°.

[0119] Before the esterification of fatty acids of different chain lengths, native spruce sawdust exhibited an X-ray diffraction pattern which had two diffraction planes for 2 0 = 22.5° and 15.8° before treatment.

[0120] After esterification of spruce sawdust with fatty acids of different chain lengths, the first crystalline radius at 22.5° due to plane 002 was shifted towards the amorphous (19.6°-21.8°) and enlarged.

[0121] These results show that esterification induces decrystallization of cellulose (see [Fig.7]).

[0122] This decrease in the crystallinity of the cellulose in the esterified wood gives the final material thermoplasticity.

[0123] Example 8: Recycling of hot-formed esterified wood

[0124] After grinding, the hot-formed material can be hot-formed again by pressing as shown in [Fig.8].

[0125] These results show that hot-formed esterified wood, heated to a temperature above its softening temperature Tl, it softens and thus exhibits a reversibility of its hardening, characteristic of thermoplastic materials.

Claims

Demands

1. A process for thermoplasticizing a cellulosic material, said process comprising: i. Contacting a fatty acid (FA) with trifluoroacetic anhydride (TFAA); and ii. Esterifying a cellulosic material by reaction with the mixed anhydride obtained in step i), thereby obtaining a thermoplastic cellulosic material, steps i) and ii) being carried out in the absence of solvent, in particular at room temperature.

2. A method according to claim 1, wherein the cellulosic material further comprises lignin and / or hemicelluloses.

3. A method according to claim 1 or 2, wherein the cellulosic material comprises at least 20%, in particular 30%, in particular 40% by weight of cellulose.

4. A process according to any one of the preceding claims, wherein the cellulosic material comprises: - 40-60% by weight of cellulose, - 20-40% of hemicelluloses, and - 10-25% of lignin.

5. A method according to any one of the preceding claims, wherein the cellulosic material is selected from wood, plants, or mixtures thereof.

6. A process according to any one of the preceding claims, wherein the cellulosic material used in step i) is in the form of powders, raw or woven fibers or in solid form.

7. A method according to any one of the preceding claims, wherein the cellulosic material is wood, in particular in powder form or in solid form.

8. A process according to any one of the preceding claims, wherein the fatty acid (FA) is a saturated or unsaturated fatty acid, such as propionic acid, butyric acid, crotonic acid, isovaleric acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and oleic acid.

9. A process according to any one of the preceding claims, wherein the molar ratio of the AG / TFAA reactants is between 0.8 and 1.2 and is preferably equal to 1.

10. A method according to any one of the preceding claims, wherein step i) is carried out for a period of less than 1 hour, in particular a period of 30 minutes.

11. A process according to any one of the preceding claims, wherein the mass proportion of TFAA implemented in step i) relative to the cellulosic material implemented in step ii) varies from 4 / 1 to 2 / 1.

12. A process according to any one of the preceding claims, wherein the esterification step ii) is carried out for a period of less than 4 hours.

13. A process according to any one of the preceding claims, wherein the thermoplastic cellulosic material obtained in step ii) is subjected to a purification process comprising the following steps: - Washing the thermoplastic cellulosic material with a hydroalcoholic mixture; and - drying the washed thermoplastic cellulosic material until an anhydrous thermoplastic cellulosic material is obtained.

14. Thermoplastic cellulosic material obtained by the process according to any one of claims 1 to 13.

15. Thermoplastic cellulosic material according to claim 14 wherein the esterification rate is between 5 and 15 mmol of ester / g of cellulosic material, in particular between 6 and 12 mmol of ester / g of cellulosic material.

16. Thermoplastic cellulosic material according to claims 14 or 15, characterized in that its degree of crystallinity is at least 30% lower than that of the native cellulosic material and / or is between 3 and 25%.

17. Use of a thermoplastic cellulosic material according to any one of claims 14 to 16, in a hot forming process.

18. Use according to claim 17, wherein the forming process comprises a pressing step, in particular carried out at a temperature between 120 and 200°C, and / or at a pressure between 10 MPa and 15 MPa.

19. Hot-formed cellulosic material comprising a thermoplastic cellulosic material according to any one of claims 14 to 16.

20. Hot-formed thermoplastic material according to claim 19, characterized in that its first softening temperature is between 40°C and 200°C, in particular between 120°C and 200°C.

21. Hot-formed thermoplastic material according to claim 19, wherein the cellulosic material has a density between 1 and 1.5 g / cm3.

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