FR3136465A1 - Process for preparing a thermoplastic cellulosic material - Google Patents

Abstract

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

Description

Process for preparing a thermoplastic cellulosic material Field of the invention

The invention relates to a process for thermoplasticizing a cellulosic material. It also relates to the thermoplastic cellulosic material which can be obtained according to this process, its implementation in a hot forming process, as well as the hot formed cellulosic material which can be obtained according to this process.

Technical background

The plastic materials currently used largely rely on the use of petrochemical resources which cause significant greenhouse gas emissions. Furthermore, some plastics are difficult to biodegrade, causing significant environmental problems.

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 different thermoplastic matrices (PE, PP, PVC), which are shaped using classic extrusion techniques in particular.

However, these composite materials whose thermoplastic properties result mainly from the presence of a thermoplastic matrix, remain mainly made up of polymers of petroleum origin, and therefore only allow a very limited reduction in CO ₂ emissions into the environment linked to to their manufacture. In addition, these composite materials remain difficult to biodegrade.

There is therefore a real need to have thermoplastic materials mainly made up of renewable resources, replacing materials of fossil origin, in order to reduce the impact of plastic materials on the environment.

A process has now been developed making it possible to confer thermoplastic properties on a cellulosic material, such as in particular wood. More particularly, the inventors discovered that by esterifying the hydroxyl functions of a cellulosic material with fatty acids comprising saturated or unsaturated hydrocarbon chains, in particular according to a specific esterification rate, it was possible to modify the native properties of the cellulosic material, in particular to reduce its crystallinity and to give it thermoplastic properties.

Thus, by way of example, the inventors were able to observe that the crystallinity index (CrI) of a 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, while that of the same native wood, not esterified, was around 42%.

Advantageously, the thermoplasticization process can be carried out under mild conditions, in particular without solvent and advantageously at room temperature, which thus limits the environmental impact and the economic cost linked to the implementation of 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.

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 compounds from petrochemicals.

According to another advantage, the thermoplastic cellulosic materials capable of being obtained according to this process are characterized, after hot forming, in particular by pressing, by a first softening temperature (T ₁ ), that is to say the temperature of lowest softening, 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 process hot forming and thus the risk of degradation of the cellulosic material, while also promoting their recycling.

Advantageously, the hot-formed materials obtained from thermoplastic cellulosic materials are 100% biosourced and do not contain plasticizers or thermoplastic polymers from petrochemicals.

According to another advantage, the hot-formed material has an isotropy of appearance making it possible to no longer observe the initial particles of cellulosic material. It generally has softness, flexibility and characteristics of a translucent and thermoplastic material.

By “isotropic appearance”, we mean a material presenting overall homogeneity as a whole.

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

By “flexibility” we mean a flexible material that can be easily bent or bent easily.

By “translucent” we mean a material which, when light passes through it, diffuses part of the light rays, generally due to irregularities in its surface. Conversely, opaque materials (unmodified sawdust) which block all light rays.

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

1. Bringing a fatty acid (FA) into contact with trifluoroacetic anhydride (TFAA); And
2. The esterification of a cellulosic material by reaction with the mixed anhydride obtained in step i), whereby a thermoplastic cellulosic material is obtained,

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

According to embodiments, the method according to the invention comprises one or more of the following additional characteristics:

• 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:

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

• 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 a solid state;
• the cellulosic material is wood, in particular in the form of powder or in the solid state;
• fatty acid (FA) is a saturated or unsaturated fatty acid, such as propionic acid, butyric acid, crotonic acid, isovaleric acid, caprylic acid, capric acid, acid lauric acid, myristic acid, palmitic acid, stearic acid and oleic acid;
• the molar ratio of the AG/TFAA reagents is between 0.8 and 1.2 and is preferably equal to 1;
• step i) is carried out for a duration of less than 1 hour, in particular a duration of 30 minutes;
• the mass proportion of the TFAA used in step i) relative to the cellulosic material used 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 cellulosic material with a hydroalcoholic mixture; And
  • drying the washed thermoplastic cellulosic material until an anhydrous thermoplastic cellulosic material is obtained.

According to a second aspect, the invention relates to a thermoplastic cellulosic material capable of being obtained by the process according to the invention.

In embodiments, the thermoplastic cellulosic material is a material in which:

- 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; and or

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

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.

In embodiments, 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.

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

In embodiments, the hot-formed cellulosic material is characterized by:

• a first softening temperature of between 40°C and 200°C, in particular between 120°C and 200°C; and or
• a density between 1 and 1.5 g/cm ³ .

Brief description of the figures

shows the evolution of the mass gain (GM) of the esterification reaction of wood powder with different fatty acids as a function of the reaction time

shows the evolution of the mass gain at the end of step ii) as a function of the quantity of TFAA used in step i)

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

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 microscopy scanning electronics.

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.

: Curves showing softening temperatures

wood esterified with different fatty acids

: X-ray diffraction analysis of unmodified wood powder esterified with different fatty acids

: Recyclability of hot-formed esterified wood

detailed description

The invention is now described in more detail and in a non-limiting manner in the description which follows.

Unless otherwise stated, percentages are expressed by weight. In particular, the weight of the cellulosic material refers to the weight of dry material, that is to say containing less than 1% water.

Process for thermoplasticizing a cellulosic material

Thus, according to a first aspect, the invention relates to a process for thermoplasticizing a cellulosic material, said process comprising:

1. Bringing a fatty acid (FA) into contact with trifluoroacetic anhydride (TFAA); And
2. The esterification of a cellulosic material by reaction with the mixed anhydride obtained in step i), whereby a thermoplastic cellulosic material is obtained,

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

By “thermoplasticization” we mean a process for converting a cellulosic material into a thermoplastic material.

By “ambient temperature”, we mean a temperature generally between 15 and 25°C, in particular between 20 and 24°C.

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

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

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

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

According to embodiments, the cellulosic material is hemp or linen.

According to a preferred embodiment, the cellulosic material is wood, in particular in the form of powder or in the solid state. It can be made from a species of spruce, poplar, oak, beech, fir, Douglas fir or pine wood. It can also include a mixture of wood species, particularly in the form of powders.

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

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

According to embodiments, step i) is carried out for a duration of less than 1 hour, in particular a duration of 30 minutes.

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

According to embodiments, step ii) of esterification is carried out for a duration of less than 4 hours.

The thermoplastic cellulosic material obtained in step ii) can then be 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.

The TFAA and TFA which have not reacted in step i) or released during the esterification reaction of the hydroxyl functions of the cellulosic material in step ii) can be advantageously recovered and reused in the thermoplasticization process according to 'invention. It can be recovered in particular by distillation.

Thermoplastic cellulosic material

According to a second aspect, the invention relates to a thermoplastic cellulosic material capable of being obtained by the process as defined above.

According to further embodiments, the esterification rate of the thermoplastic cellulosic material 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.

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

By “crystallinity rate”, or “crystallinity 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, A.E., Conrad, C.M., 1959. An empirical method for estimating the degree of crystallinity of native cellulose using X-ray diffractometer. Text. Res. J. 29, 786–794.

The crystallinity rate of the thermoplastic cellulosic material may in particular be between 3 and 25%.

Use of a thermoplastic cellulosic material in a hot forming process

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.

By “hot forming” process we mean a process consisting of taking a material, heating it to soften it, and taking advantage of this ductility to shape it with a mold. The material hardens again when it cools, keeping this shape.

The hot forming process may in particular be a hot pressing process, in particular comprising a pressing step.

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

For 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.

Hot formed thermoplastic cellulosic material

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

The cellulosic material may in particular have a density of between 1 and 1.5 g/cm ³ .

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

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

The hydroxyl groups of spruce wood have been functionalized with different fatty acids. The reaction diagram is as follows:

Scheme 1: Esterification of spruce wood powder with fatty acids

using TFAA

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

The materials obtained were characterized by measuring the mass gain (GM), determining the characteristics of the chemical structure by FTIR and NMR analysis, the thermal properties by thermogravimetric analysis (ATG) and differential scanning calorimetric analysis (DSC), the adhesive properties/molding ability of esterified powder by hot pressing, surface properties of esterified pressed wood by contact angle measurement, morphological properties by scanning electron microscopy (SEM) and thermoplastic properties by analysis thermomechanics (TMA) and X-ray diffraction (XRD).

To calculate the mass gain (GM), we can refer to the following publication: Philippe Gerardin et al. Wood Science and Technology (2020) 54:479–502.

Spruce sawdust (Picea abies) was used after Soxhlet extraction for 4 h with a toluene/ethanol mixture in the proportions (2:1), 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 that the quantities of wood expressed below, before treatment, refer to the dry material.

Different lengths of fatty chains were used ranging from C4 to C18 for saturated fatty acids. Regarding unsaturated fatty acids, crotonic acid (C4) and oleic acid (C18) were used.

Specifically, a fatty acid was mixed with TFAA in a molar ratio (1:1) without solvent at room temperature to form a mixed anhydride. The oven-dried wood powder was then added to the mixed anhydride in Wood/TFAA proportions of (1:4) (m/m) relative to the quantity of TFAA used in step i), for different reaction times (15 min-24h) in a closed system. Esterified woods were successively washed with ethanol and water followed by soxhlet extraction in ethanol/water (2:1) for 24 h, changing the solvent mixture as much as possible to remove the TFA formed during the esterification reaction or the residual TFAA.

The sample obtained was then dried at 103°C for 24 h, and the mass gain (GM) was calculated.

More particularly, after treatment of the spruce sawdust, the mass gain (GM) was determined gravimetrically according to the equation: GM = [(m1-m0) / m0] X 100 with m0 = mass of the sawdust anhydrous spruce sawdust before treatment, m1 = mass of anhydrous spruce sawdust after treatment.

After treatment, the experimental mass gain or GM is determined gravimetrically according to the equation: GM = [(m ₁ -m ₀ ) / m ₀ ] X 100 with m ₀ = mass of the anhydrous sawdust before treatment, m ₁ = mass of anhydrous sawdust after treatment. The increase in mass gain (GM) reflects the grafting of fatty acids by esterification of the hydroxyl functions of the wood and makes it possible to determine the rate of esterification of wood by the fatty acid, by dividing the mass gain by the molar mass. M of the corresponding grafted acyl function for a given fatty acid.

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

There describes the grafting of different fatty acids onto wood using variable reaction times (15 min - 24 hours). After 15 minutes of reaction, the ester content already reaches 7.6 – 9.9 mmol ester/g wood; after 1 hour of reaction, it is greater than 10 mmol of ester/g of wood and begins to stabilize up to 24 hours of reaction.

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

The esterification of wood powder with different quantities of fatty acid and trifluoroacetic anhydride (TFAA) relative to the mass of wood used was studied ( ), the quantity of TFAA relative to AG remaining constant and equal to 1 molar equivalent.

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

Example 2: characterization of the chemical and structural properties of esterified wood

Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analysis were carried out to understand the chemical and structural changes of wood before and after esterification.

Fourier transform infrared spectroscopy (FTIR) shows that the OH vibration absorption band (3500 - 3300 cm ^-1 ) in unmodified wood disappeared in esterified wood with a significant increase in group intensity. CH, CH ₂ (2918 and 2848 cm ^-1 ) and C=O ester (1743 cm-1) observed in the esterified wood. The longest fatty chain having esterified the wood with a high mass gain (GM) shows a higher intensity of these CH groups, while the C = O ester showed the same intensity in all the esterified woods.

.The solid NMR spectrum obtained with unmodified wood shows a characteristic carbohydrate profile as evidenced by: C1 (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 (C1 of hemicellulose), at 73.4 ppm (C- 2/C-3/C-5 cellulose) decrease and move to 64.2 ppm (amorphous cellulose C-6). A new peak also appears in the esterified wood at 14.6 – 30 ppm corresponding to the methyl and methylene groups and at 172.7 ppm corresponding to the C=O ester.

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

Example 3: Characterization of the thermal properties of esterified woods

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

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

Spruce sawdust, esterified with different fatty acids according to the process of the invention, were 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 non-esterified sawdust, with an opaque appearance (Figure 3D).

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

Furthermore, Figure 3C shows that the sheets obtained are flexible when they are folded on themselves, and therefore have thermoplastic properties.

The fibrous structure of unmodified hot-pressed spruce sawdust was observed by scanning electron microscopy ( ). After esterification, this fibrous structure disappears following the apparent fusion of the wood fibers. Esterified wood appears more compact and less fibrillar, indicating thermal fusion of the wood.

Example 5: Characterization of the surface properties of esterified woods

The contact angle measurement of pressed sheet spruce wood before and after esterification was observed to understand the surface properties of the esterified woods.

There shows that before esterification of the wood, the water droplets form a low contact angle just after the start of the measurement. After esterification of wood with different fatty acid chain lengths, the contact angle varied from 69.3 to 96.8° at the beginning of the measurement and from 65.1 to 92.7° after 60 seconds of measurement. These results show that the esterification of wood with different fatty acids makes the surface of the material hydrophobic.

Example 6: Thermomechanical analysis of esterified woods

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

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

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

Table 1: Softening temperatures of esterified wood

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

The diffraction patterns were performed directly on the modified and unmodified wood powder. The assembly used includes a SEIFERT XRD-3000 type generator, working at 40KV, 30mA and according to a Bragg - Brentano (θ/θ) geometry. CuKα1 radiation is selected from a copper source using a graphite monochromator, at the wavelength h = 0.1540598 nm. The diffraction patterns are recorded for angles θ between 1 and 30°.

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

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

These results show that esterification induces decrystallization of cellulose (see ).

This reduction in the crystallinity of the cellulose in the esterified wood gives the final material thermoplasticity.

Example 8: Recycling of hot-formed esterified wood

After grinding, the hot-formed material can be hot-formed again by pressing as shown in .

These results show that hot-formed esterified wood, heated to a temperature higher than its softening temperature T1, softens and thus exhibits reversibility of its hardening, characteristic of thermoplastic materials.

Claims (21)

Process for thermoplasticizing a cellulosic material, said process comprising:

1. Bringing a fatty acid (FA) into contact with trifluoroacetic anhydride (TFAA); And
2. The esterification of a cellulosic material by reaction with the mixed anhydride obtained in step i), whereby a thermoplastic cellulosic material is obtained,

steps i) and ii) being carried out in the absence of solvent, in particular at room temperature. A method according to claim 1, wherein the cellulosic material further comprises lignin and/or hemicelluloses. Method according to claim 1 or 2, in which the cellulosic material comprises at least 20%, in particular 30%, in particular 40% by weight of cellulose. Process according to any one of the preceding claims, in which the cellulosic material comprises:

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

Method according to any one of the preceding claims, in which the cellulosic material is chosen from wood, plants, or mixtures thereof. Process according to any one of the preceding claims, in which the cellulosic material used in step i) is in the form of powders, raw or woven fibers or in the bulk state. Method according to any one of the preceding claims, in which the cellulosic material is wood, in particular in the form of powder or in the solid state. Process according to any one of the preceding claims, in which the fatty acid (AG) 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. Process according to any one of the preceding claims, in which the molar ratio of the AG/TFAA reagents is between 0.8 and 1.2 and is preferably equal to 1. Method according to any one of the preceding claims, in which step i) is carried out for a duration of less than 1 hour, in particular a duration of 30 minutes. Process according to any one of the preceding claims, in which the mass proportion of the TFAA used in step i) relative to the cellulosic material used in step ii) varies from 4/1 to 2/1. Process according to any one of the preceding claims, in which step ii) of esterification is carried out for a period of less than 4 hours. Process according to any one of the preceding claims, in which 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.

Thermoplastic cellulosic material obtained by the process according to any one of claims 1 to 13. Thermoplastic cellulosic material according to claim 14 in which 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. Thermoplastic cellulosic material according to claims 14 or 15, characterized in that its crystallinity rate is at least 30% lower than that of the native cellulosic material and/or is between 3 and 25%. Use of a thermoplastic cellulosic material according to any one of claims 14 to 16, in a hot forming process. Use according to claim 17, in which 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. A hot-formed cellulosic material comprising a thermoplastic cellulosic material according to any one of claims 14 to 16. 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. Hot-formed thermoplastic material according to claim 19, wherein the cellulosic material has a density of between 1 and 1.5 g/cm ³ .