[0001] The invention relates to the field of carbon fibers, especially of carbon fibers made from bio-based precursors for the manufacture of pieces in thermoplastic or thermosetting materials which can be used especially in the field of aeronautics, automotive, wind energy, naval, building construction, sport. The invention relates to a method for manufacturing a highly carbonaceous fiber or a set of highly carbonaceous fibers and the fiber or set of fibers may be obtained by such a manufacturing method.

Prior Art!

[0002] The carbon fiber market is expanding. In recent years, the carbon fiber industry has been growing to meet the demands from different applications. The market is currently estimated at approximately 60 kt / year and should grow up to 150-200 kt / year by 2020-2025. This high growth forecast is primarily related to the introduction of carbon fiber in composites used in the aerospace, energy, construction, automotive and leisure.

[0003] The carbon fibers generally have excellent tensile properties, high thermal and chemical stabilities, good thermal and electrical conductivities, and excellent resistance to deformation. They can be used as reinforcements for composite materials which typically comprise a polymer resin (matrix). The thus reinforced composite materials have excellent physical properties while maintaining an advantageous lightness. The relief is a key measure of the reduction of C0 emissions 2 for transport. The automotive and aviation industry is in demand of compounds at equivalent performance, greater lightness.

[0004] In this context, the automotive and aerospace sectors, and more broadly the industry, also, need efficient materials but at controlled costs. Indeed, the performance of composite materials is due in part to the use of carbon reinforcing fibers which have today, the drawback of a high price, depending on the raw material used and manufacturing processes.

[0005] Today the carbon fibers are predominantly made from acrylic precursor. Polyacrylonitrile (PAN) precursor is the most used today for the manufacture of carbon fibers. Briefly, the production of carbon fibers from PAN comprises the steps of polymerization of the precursor PAN-based, fiber spinning, thermal stabilization, carbonization and graphitization. Carbonization takes place under a nitrogen atmosphere at a temperature of 1000 to 1500 ° C. The carbon fibers obtained at the end of these steps are made in 90% carbon, about 8% nitrogen, 1% oxygen and less than 1% hydrogen. An additional step, designated by graphitization is sometimes performed. This usually requires a temperature of 2500 to 3000 ° C. In that case, the last stage is used to obtain a 99% carbon compound material, which makes it considerably more malleable, but also less resistant. These two steps of carbonization and graphitization require mounted very high temperatures and are thus energy intensive. Blocking factors for wider use of composite materials based on carbon fibers having a precursor of PAN fibers, are their cost which is linked in part to the cost of oil and the management of the production line, including the rise temperature, which is quite complex. These two steps of carbonization and graphitization require mounted very high temperatures and are thus energy intensive. Blocking factors for wider use of composite materials based on carbon fibers having a precursor of PAN fibers, are their cost which is linked in part to the cost of oil and the management of the production line, including the rise temperature, which is quite complex. These two steps of carbonization and graphitization require mounted very high temperatures and are thus energy intensive. Blocking factors for wider use of composite materials based on carbon fibers having a precursor of PAN fibers, are their cost which is linked in part to the cost of oil and the management of the production line, including the rise temperature, which is quite complex.

[0006] A pitch-based precursors have also been developed, but as acrylic precursors they consume fossil fuels and cause energy consumption related to the high temperatures required during the steps of carbonization and graphitization.

[0007] With the aim of reducing the price of the carbon fiber, one of the proposed solutions has been to replace the basic elements of petroleum (eg PAN or Pitch) with biobased materials, such as cellulose or lignin contained in the wood. The cost for manufacturing carbon fiber using as a precursor of the cellulose is much lower than that of the fibers with PAN. In this context, several cellulosic precursors were evaluated. The cellulose-based precursors have the advantage of producing well-structured charred structures but they generally fail to achieve satisfactory carbon yields.

[0008] Nevertheless, there is in the art of more environmentally friendly fiber manufacturing processes. For example, WO2014064373 application published May 1, 2014 filed by the applicant describes a manufacturing process, from a bioresourced precursor, continuous carbon fiber doped with carbon nanotubes (CNTs). The presence of the CNTs in the bioresourced precursor allows to increase the carbon yield of the precursor during carbonization, as well as to increase the mechanical properties of carbon fibers. The bioresourced precursor can be converted to cellulose in the form of fibers by dissolution and coagulation / spinning, so as to form the hydrocellulose (e.g., viscose, lyocell, rayon). Such a method allows the production of a continuous and regular filament from bioresourced precursor. Nevertheless, this method still relies on a carbonization stage with a temperature rise up to 600 ° C and a step of graphitization at a temperature of 2000 ° C to 3000 ° C and preferably 2200 ° C, resulting in consumption energy related to high temperatures required.

[0009] One may also refer to the document KR 20120082287 which discloses a process for manufacturing carbon fiber from a precursor material comprising lyocell (cellulose fibers from wood or bamboo) and a nanocomposite material - graphenes.

[0010] One may also refer to the document CN1587457 discloses a method for preparing a cellulose precursor material for the production of carbon fiber having improved properties and a lower cost of manufacture. The cellulosic preparation involves the insertion of nano soot particles in the cellulose solution.

[001 1] Reference may be made in the same way the document US 201 1/285049 which discloses a method for producing a carbon fiber from a precursor material comprising a continuous fiber lignin including dispersed carbon nanotubes representing 10% by weight or less and preferably from 0.5 to 1, 5%. Lignin and carbon nanotubes are mixed and heated to be melt, extrusion and spinning. This method does not provide sizing step of the precursor material.

[0012] However, the methods as described above, are all based on the use of a cellulose-based precursor or lignin which is added fillers prior to implement the steps of carbonization and graphitization. These processes are not satisfactory since the carbon yields the one seeks to increase and / or alleviate the composite parts made with these carbon fibers. The further steps of carbonization and graphitization are carried out at normal temperatures which are too high in view of a decrease in manufacturing costs of the fibers or sets of fibers and composite material parts made with these fibers.

[0013] Thus, there remains a need for precursors and methods for manufacturing carbon fibers capable of responding to problems with existing methods for: i) a reduced density to produce materials based on fiber carbon lighter, ii) high yield atoms, iii) a reduced manufacturing cost, and iv) a simple conversion of carbon fiber.

Technical rProblème!

[0014] The invention therefore aims to overcome the disadvantages of the prior art. In particular, the invention aims to provide a process for producing carbon fibers, said method being simple to implement, with a reduced number of steps, and to control costs thanks to the reduction of expenditure energy-related stages of carbonization and graphitization.

[0015] The invention further aims to provide a highly carbonaceous fiber or set of highly carbonaceous fibers, mechanically very stable with a carbon yield higher than conventionally carbon fibers obtained from bio-based materials. In addition, the highly carbonaceous fibers of the invention are lighter and have a lower density than the conventional carbon fibers. Advantageously, the method may be implemented on sets of organized fibers and non-carbonized such as lyocell, viscose, rayon, to form quickly and at lower cost, combinations of woven carbon fibers to namely carbon fiber fabrics.

Γ Brief Description of inventionl

[0016] Thus, the invention relates to a method of manufacturing a fiber or a set of highly carbonaceous fibers, mainly characterized in that it comprises the combination of a structured precursor comprising a fiber or a set of fibers of hydrocellulose, and an unstructured precursor, further comprising lignin or a lignin derivative, which is in the form of a solution having a viscosity lower than 15 000 mPa.s and most preferably less than 10 000 mPa.s at the temperature at which occurs the combining step, to obtain a fiber or a set of hydrocellulose covered with said lignin fibers, said method further comprising the steps of:

- a thermal and dimensional stabilization step of the fiber or set of fibers hydrocellulose covered with said lignin so as to obtain a fiber or a set of hydrocellulose covered with a deposit of lignin fibers, and

- a step of carbonizing the fiber or set of hydrocellulose fibers covered with a lignin deposit so as to obtain a fiber or a set of highly carbonaceous fibers.

[0017] This new production process, from bio-based precursors, a highly carbonaceous carbon fiber or a set of highly carbonaceous carbon fibers has many advantages such as the reduction in energy demand to produce materials with equivalent properties, obtaining a carbon yield higher than that observed with the methods of the prior art and forming fibers having a low density.

[0018] According to other optional features of the method:

- the precursor comprises a structured multi-filament twisted, an untwisted multi-filament, a set of non-woven fibers, or a set of woven fibers. Indeed, the process according to the invention has the advantage of reducing manufacturing costs of the carbon fiber assemblies (for example woven). For example, in the context of the method according to the invention, it is possible to manufacture a fiber fabric of hydrocellulose (for example: viscose, lyocell, rayon) and directly to sustain the manufacturing process according to the invention to form a set of highly carbonaceous fibers.

unstructured precursor comprises between 1 and 50%, preferably between 5% and 1 5% by weight lignin or a lignin derivative. Lignin is a widely available resource, underutilized and low cost allowing the process to meet the economic demands of industries. Also, at such concentrations, the hydrocellulose fibers are completely covered with a deposit of lignin without that the latter does not entail deformation of fibers or an amalgam.

unstructured precursor is an aqueous solution or an organic solution or a mixture of both. These alternatives allow to adapt the precursor unstructured depending on lignin or lignin derivative used and of any carbon nanotubes added. Preferably, the unstructured precursor is a hydroalcoholic solution of lignin or lignin derivative.

structured precursor comprises at least one fiber hydrocellulose whose diameter is between 0.5 and 300 μηι μηι, preferably between 1 and 50 μηι μηι. The invention has the advantage of being suitable for a wide range of fiber diameter of hydrocellulose.

precursor structured and / or unstructured precursor comprises carbon nanotubes, said carbon nanotubes being present at a concentration between 0.0001% and 10% by weight, and preferably between 0.01% and 1% by mass. The addition of carbon nanotubes (CNTs) to one of the two, or both precursors improves the carbon fiber yield obtained. Indeed, when such a substance is added to lignin or lignin derivative, lignin or lignin derivative act as a binder and cause an increase in the amount of CNT is indeed inserted in the resultant carbon fiber.

The combining step comprises impregnation. The impregnation has the advantage of being a method that can be easily implemented industrially.

the steps of combining and thermal and dimensional stabilization are repeated one or more times. This is particularly advantageous for thus it is possible to increase the carbon efficiency, increase the diameter of the fibers obtained and / or reduce their density.

- the manufacturing method further comprises, before the carbonization step, the steps of:

o a sizing step of contacting the fiber or set of hydrocellulose coated with a lignin deposit fibers with an aqueous solution comprising at least one flame retardant, said flame retardant being selected from: potassium , sodium, phosphate, acetate, chloride, urea, and

o a step of sizing post drying.

This has the advantage of strengthening the physicochemical properties of the obtained carbon fibers. Indeed, although the lignin or lignin derivative has flame retardant properties, the addition of a sizing step with a solution comprising at least one flame retardant compound improves the characteristics of the carbon fiber obtained.

- Advantageously, the sizing steps and post sizing drying are repeated one or more times. This is advantageous because it is possible to increase the amount of fire retardant associated with the fiber or so to combine different treatments with different substances.

- the manufacturing method according to the invention further comprises, after the carbonization step, a step of graphitization. Graphitization increases the malleability of the carbon fiber or the entire carbon fiber obtained by the process according to the invention.

- the manufacturing method according to the invention further comprises, after the carbonization step, a sizing step of contacting the fiber or set of highly carbonaceous fibers with a solution comprising at least one organic component which comprise at least one silane derivative or silane and / or at least one derivative siloxane or siloxane. This step helps to improve the physicochemical properties of the fiber (e.g., a protection against abrasion and improving the integrity of the fibers) and has the advantage, in the context of the invention can be performed on a set fiber, that is to say for example on a carbon fiber fabric.

[0019] The invention further relates to a fiber or a fiber assembly of hydrocellulose covered with a deposit of lignin or lignin derivative as an intermediate product obtained after the step of thermal and dimensional stabilization of the manufacturing method the invention, for which the ratio of the mass of fiber mass lignin or lignin derivative is between 1/2 and 100/1.

[0020] Optionally, the deposition of lignin or the lignin derivative fiber or set of hydrocellulose covered with a deposit of fibers lignin or lignin derivative according to the invention may comprise between 0.50% and 50% by weight of flame retardant, preferably between 2% and 30% by mass relative to the deposition lignin).

[0021] The invention further relates to a highly carbonaceous fiber or fabric of carbon fibers highly likely to are obtained by the process according to the invention. Advantageously, the fiber or set of fibers present, after the carbonization step, a density between 0,20 and 1, 95 g / cm 3 , preferably between 1 45 and 1 60 g / cm 3 . These products meet the expectations of manufacturers in search of lighter carbon fiber however with sufficient mechanical properties especially to meet the needs of aeronautical or automotive industries.

[0022] The invention further relates to the use of fibers or sets of highly carbonaceous fibers obtained according to the manufacturing method for the manufacture of pieces in thermoplastic or thermoset composites.

[0023] The invention further relates to thermoplastic or thermoset composites obtained with fibers or sets of fibers manufactured according to the manufacturing method of the invention. These thermoplastic or thermosetting composite materials have the advantage of having, for the same volume, a lower weight of at least 5% by weight of conventional thermoplastic or thermoset composites.

[0024] Other advantages and features of the invention appear on reading the following description given by way of illustrative and nonlimiting example, with reference to the appended figures which represent:

Figure 1 shows a diagram of an embodiment of the carbon fiber manufacturing method according to the invention. The steps framed by dotted lines are optional.

Figure 2 shows an image obtained by scanning electron microscopy of a section of carbon fibers according to the invention.

[Description of the Invention!

[0025] The term "fiber or set of highly carbonaceous fiber" according to the invention, a more than 80% compound material, by weight, of carbon, preferably more than 90%, more preferably more than 95%, even more preferably more than 98% (materials considered materials of very high purity).

[0026] The term "fiber hydrocellulose" according to the invention, cellulose fibers or cellulose derivatives, preferably continuous and regular diameter, obtained after dissolution of cellulose from lignocellulosic material. As detailed in the following text, this combination can be accomplished by several alternative methods. The hydrocellulose may, for example, be obtained after a treatment with sodium hydroxide followed by dissolution with carbon disulfide. In this case the hydrocellulose is specifically called viscose. Alternatively, the fiber hydrocellulose can be obtained from lignocellulosic material dissolved in a solution comprising N-methylmorpholine N-oxide to form lyocell.

[0027] The term "lignin" a plant according to the invention aromatic polymer whose composition varies with the plant species and generally formed from three phenylpropanoid monomers: p-coumaryl alcohol, coniferyl and sinapyl.

[0028] The term "lignin derivative" according to the invention a molecule having a molecular structure of lignin and having substituents have been added during the process for extracting lignin or subsequently so as to modify its physicochemical properties. There are many method for extracting lignin from lignocellulosic biomass and these can lead to changes in the lignin. For example, the Kraft process uses a strong base with sodium sulfide to separate lignin from cellulose fibers. This process may form thio-lignins. The sulfite process, resulting lignosulfonates formation. The methods

Organosolv pretreatment using an organic solvent or mixtures of organic solvents with water to solubilize the lignin prior to the enzymatic hydrolysis of the cellulosic fraction. Preferably by lignin derivative must include a lignin having substituents being selected from: thiol, sulphonate, Alkyl, or polyesther. Lignins or lignin derivatives used in the context of the present invention generally have a molecular weight greater than 1000 g / mol, for example greater than 10,000 g / mol.

[0029] In the following description, the same references are used to designate the same elements.

[0030] According to a first aspect, the invention relates to a process 1 of a fiber or of a set of highly carbonaceous fibers 2, comprising the combination 100 of a structured precursor 10 comprising a fiber or a set of fibers of hydrocellulose, and an unstructured precursor 15 comprising lignin or a lignin derivative, which is in the form of a solution having a viscosity less than 15,000 mPa.s at the temperature at which takes place the 'combining step 100.

[0031] This combination of step 100 provides a fiber or a fiber assembly of hydrocellulose covered with said lignin or lignin derivative 20.

[0032] This process is illustrated in Figure 1. It can be carried out continuously or batchwise. As part of a continuous production, in industrial processes the sequence of steps without interruption and that from a fiber or even an assembly of fibers.

structured precursor (10)

[0033] The structured precursor 10 comprises a fiber or set of fibers hydrocellulose. This fiber or set of fibers hydrocellulose can take very different forms. One advantage of the invention is that the method may be implemented on hydrocellulose of fibers having been previously formatted, for example in the form of a twisted multi-filament, untwisted multi-filament , a set of non-woven fibers, or a set of woven fibers.

[0034] In the manufacture of carbon fiber fabrics, it is usually necessary to produce coils of carbon fibers, for example from PAN then organize these fibers according to the desired weaving. Here, the invention enables direct use of hydrocelluloses fibers having previously been held in the form of multi-filament or fiber assembly. The method according to the invention then makes it possible, thanks to the lignin deposition step or lignin derivative on said hydrocelluloses fibers, and after a step of carbonization and possibly graphitization, to create multi-filaments or together fibers, such as a fabric of carbon fibers having a reduced density and advantageous mechanical properties including,

[0035] Thus, preferably, the structured precursor 10 comprises a twisted multi-filament untwisted multi-filament, a set of non-woven fibers, or a set of woven fibers. Even more preferred, the structured precursor 10 is a twisted multi-filament untwisted multi-filament, a set of non-woven fibers, or a set of woven fibers.

[0036] The multi-filament twisted can be used according to the invention for instance have a number of turns per meter between 5 and 2000 turns per meter, preferably between 10 and 1000 turns per meter,

[0037] The structured precursor 10 according to the invention may comprise at least one fiber of hydrocellulose whose diameter is between 0.5 and 300 μηι μηι, preferably between 1 and 50 μηι μηι. In addition, preferably the structured precursor 10 according to the invention comprises at least one continuous fiber hydrocellulose having a regular diameter along its length, and in particular the absence of fibril. This improves the cohesion between the filing of lignin and fiber. By regular diameter, it is understood that the diameter varies by less than 20%, preferably less than 10% along the length of the fiber.

[0038] This fiber hydrocellulose can be obtained by various known production processes. It may for example be obtained according to the manufacturing method described in the application WO2014064373. The hydrocellulose used fibers may also be fibers of lyocell or viscose, the cellulose is derived for example of wood or bamboo.

[0039] Most of the fiber manufacturing processes of hydrocellulose is based on achieving a cellulosic preparation from dissolved cellulose, for example carbon disulfide, 4-oxide, 4-methylmorpholine (N-Methylmorpholine- N-oxide NMMO) or in an acid solution (eg ortho-phosphoric acid or

acetic acid), which is then used to form the continuous fibers of hydrocellulose following immersion in a coagulation bath containing for example sulfuric acid. The fiber hydrocellulose used in the method of the present invention as a precursor, has not been pre-carbonization.

unstructured precursor (15)

[0040] The informal precursor 15 comprises lignin or a lignin derivative. Lignin is 10 to 25% of the Earth's biomass lignocellulosic nature and it is now only undervalued by industry. Each year, hundreds of tons of lignin or lignin derivatives are produced without any possible recovery. Lignin is present mainly in vascular plants (or higher plants) and some algae. This is a plant aromatic polymer whose composition varies with the plant species and generally formed from three phenylpropanoid monomers: p-coumaryl alcohol, coniferyl and sinapyl as shown by the following formulas:

alcohol p-coumaryl alcohol sinapyl alcohol coniferyl

[0041] Preferably, the unstructured precursor 15 comprises between 1 and 50% by weight lignin or a lignin derivative. Advantageously, the unstructured understand precursor 15 between 5% and 15% by weight lignin or a lignin derivative. At this concentration, the deposition of lignin or lignin derivative is homogeneous while allowing an increase in the carbon efficiency of the carbon fiber obtained after the carbonization step 300.

[0042] In addition, the unstructured precursor 15 is in the form of a solution having a viscosity lower than 15 000 mPa · s-1 and preferably less than 10 000 mPa.s- to the temperature at which unfolds the combining step 100. with

such a viscosity, the deposition of lignin or lignin derivative is more homogeneous and allows to obtain a continuous carbon fiber having a regular diameter while allowing an increase in the carbon efficiency of the carbon fiber obtained after the carbonization step 300. regular diameter, it is understood that preferably, the carbon fiber has a diameter not varying more than 20%, preferably by more than 10% along its length.

[0043] The viscosity of the solution is measured at the temperature at which occurs the combining step 100, for example through a free flowing viscometer, capillary or viscosity or the Brookfield method.

[0044] In particular, the unstructured precursor 15 used in the one manufacturing process is an aqueous solution or an organic solution or a mixture of both. The use of unstructured precursor 15 in the form of a solution makes it possible to control the deposit and its thickness. In addition, the solution composition may be selected according to the characteristics of the lignin or lignin derivative used. Preferably the unstructured precursor 15 used in the manufacturing method 1 is a solution comprising water and an organic solvent such as an alcohol.

[0045] Advantageously, the precursor 10 structured and / or unstructured precursor 15 can comprise carbon nanotubes, said carbon nanotubes being present at a concentration between 0.0001% and 10% by mass. Preferably, these carbon nanotubes are present at a concentration of between 0.01% and 1% by weight.

[0046] Carbon nanotubes (CNTs) can be of the single wall, double wall or multiwall. Double-wall nanotubes may especially be prepared as described by FLAHAUT et al in Chem. Corn. (2003), 1442. The multiwall nanotubes may in turn be prepared as described in WO 03/02456. Nanotubes typically have an average diameter ranging from 0.1 to 100 nm, preferably from 0.4 to 50 nm, and more preferably 1 to 30 nm, or 10 to 15 nm, and preferably a length of 0.1 10 μηι. Their length / diameter ratio is preferably greater than 10 and most often greater than 100. Their specific surface area is for example between 100 and 300 m 2 / g, preferably between 200 and 300 m 2/ G, and their apparent density may in particular be between 0.05 and 0.5 g / cm3 and more preferably between 0.1 and 0.2 g / cm3. The multi-walled nanotubes may for example comprise 5 to 15 sheets (or walls) and more preferably from 7 to 10 sheets. [0047] An example of crude carbon nanotubes is especially commercially available from Arkema under the trade name Graphistrength® C100. Alternatively, these nanotubes can be purified and / or treated (e.g., oxidized) and / or ground and / or functionalized, before their implementation in the process of the invention. The purification of raw or milled nanotubes may be carried out by washing with a sulfuric acid solution, so as to rid them of any residual mineral and metallic impurities. Oxidation of nanotubes is advantageously carried out by bringing the latter into contact with a sodium hypochlorite solution. The functionalization of the nanotubes can be achieved by grafting of reactive moieties such as vinyl monomers on the surface of nanotubes.

Combining (100)

[0048] The combining step 100 according to the invention corresponds to the contacting of the precursor 10 with the structured unstructured precursor 15. This combination can be accomplished by several alternative methods, generally at a temperature ranging from -10 ° C at 80 ° C, preferably 20 ° C to 60 ° C. For example, it is possible to realize a dipping, spraying or impregnation (e.g., padding). Preferably, the combining step 100 is impregnation.

thermal and dimensional stabilization (200)

[0049] The production method 1 of the invention further comprises a thermal and dimensional stabilization step 200 of the fiber or set of fibers hydrocellulose covered with said lignin 20 so as to obtain a fiber or a group fibers of hydrocellulose covered with a deposit of lignin 30.

[0050] The thermal and dimensional stabilization step 200 may comprise a drying for solvent evaporation and / or ventilation. Drying may be achieved via an increase in temperature, for example between 50 ° C and 200 ° C. Indeed, when the structured precursor is treated with an unstructured precursor comprising a diluent or organic solvent, it is desirable to then remove the diluent or solvent, for example to subject this article to a heat treatment to remove the diluent or the solvent in vapor form.

[0051] Following this step, a solid film of lignin or lignin derivative is formed on the surface of the fiber. This film may have varying thicknesses depending on

parameters used in the context of the process such as the viscosity of the solution or the concentration of lignin or lignin derivative.

[0052] Preferably, the combination of steps 100 and thermal stabilization and dimensional 200 may be repeated one or more times. The repetition of these steps allows to increase the amount of lignin or lignin derivative deposited on the fiber or set of fibers hydrocellulose.

Carbonisation (300)

[0053] The production method 1 of the invention further comprises a step of carbonizing the fiber 300 or the set of hydrocellulose fibers covered with a deposit of lignin 30 so as to obtain a fiber or a group highly carbonaceous fibers 2.

[0054] This carbonization step 300 may be performed at a temperature between 250 ° C and 1000 ° C, preferably above 300 ° C and preferably below 600 ° C. The charring 300 step can last, for example 2 to 60 minutes. This carbonization step may comprise a progressive rise in temperature. The carbonization takes place in the absence of oxygen and preferably under a nitrogen atmosphere. The presence of oxygen during the carbonization should be preferably limited to 5 ppm.

[0055] In general and as shown in the examples, the inventors have shown that the method according to the invention allows, with equivalent mechanical properties to use a lower temperature than methods of the prior art. So there is a reduction in the amount of energy needed to achieve these carbon fiber, an energy saving.

This carbonization step may be carried out continuously and can be coupled to a stretching step of the carbon fiber so as to improve the mechanical properties of the carbon fiber obtained.

Ensimaqe pre-carbonization (210)

[0056] The manufacturing method according to the invention may further comprise, before the carbonization step 300, the steps of:

- a sizing step 210 comprising contacting the fiber or the fiber assembly of hydrocellulose covered with a deposit of lignin 30

with an aqueous solution comprising at least one flame retardant, said flame retardant being selected from: potassium, sodium, phosphate, acetate, chloride, and urea, and

a step of post 220 sizing drying.

[0057] The steps of sizing and sizing 210 220 post drying may be repeated one or more times.

Graphitisation (400)

[0058] The manufacturing method according to the invention may further comprise, after the step of carbonization 300, a graphitization step 400. This 400 graphitization step can be carried out at a temperature between 1000 ° C and 2800 ° C , preferably greater than or equal to 1100 ° C and preferably less than 2000 ° C. The graphitization step 400 may for example be from 2 to 60 minutes, preferably 2 to 20 minutes. This graphitization step 400 may comprise a progressive rise in temperature.

Sizing post carbonisation (500)

[0059] The manufacturing method according to the invention may further comprise, after the step of carbonization 300, a sizing step 500 comprising contacting the fiber or set of highly carbonaceous fibers 2 with a solution of an organic component which can comprise at least one silane derivative or silane and / or at least one derivative siloxane or siloxane. This sizing 500 can also be performed after the graphitizing step 400. It improves the integrity of the fiber and helps protect it from abrasion.

[0060] The solution comprising at least one silane derivative or silane and / or at least one derivative Siloxane or Siloxane is preferably an aqueous solution, an organic solution or an aqueous emulsion.

[0061] According to another aspect, the invention relates to a fiber or a set of hydrocellulose covered with a deposit of lignin fibers 30 as an intermediate product obtained after the thermal and dimensional stabilization step 200 of the manufacturing method the invention.

[0062] This intermediate product shows a ratio of the fiber weight on the weight of lignin or lignin derivative included between 1/2 and 100/1, preferably between 2/1 and 95/1.

[0063] In addition, the deposition of lignin of this intermediate product comprises between 0.50% and 50% by weight of flame retardant, preferably between 2% and 30% by weight.

[0064] According to another aspect, the invention relates to a fiber or set of highly carbonaceous fibers 2 obtainable by the method according to the invention. Preferably and advantageously, the fiber or set of highly carbonaceous fibers 2 present after the carbonization step 300, a density between 0,20 and 1, 95 g / cm 3 , preferably between 1 and 45 1, 80 g / cm 3. Preferably, the invention relates to a fiber or a set of highly carbonaceous fibers 2 obtained from the combination of a structured precursor 10 and an unstructured precursor 15, said structured precursor 10 comprises a fiber or an assembly of hydrocellulose fibers, said unstructured precursor 15 comprises lignin or a lignin derivative and said fiber or set of fibers present, after the carbonization step 300, a density between 0,20 and 1, 95 g / cm 3 , preferably between 1 45 and 1 60 g / cm 3 .

[0065] More preferably, the fibers or fiber assembly may highly carbonaceous 2 are obtained by the process according to the invention, after the carbonization step 300, a density of 1, 45 and 1, 60 g / cm 3

[0066] According to another aspect, the invention relates to the use of fibers or highly carbonaceous fiber assemblies which can be obtained via the manufacturing process according to the invention for the manufacture of pieces in thermoplastic composites or thermosetting.

[0067] According to another aspect, the invention relates to thermoplastic or thermoset composite materials obtained from fibers produced through the manufacturing method according to the invention. Advantageously, these thermoplastic or thermosetting composite materials have, for the same volume, a lower weight of at least 5% by weight of conventional thermoplastic or thermoset composites.

[0068] The following example illustrate the invention but have no limiting character.

Description of starting materials:

[0069] The structured precursor used is based on hydrocellulose of fibers (rayon) sold by the company Cordenka.

[0070] For the formation of unstructured precursor, the lignin was solubilized in a mixture ethanol / water 60/40 at 60 ° C. After 2 h of stirring, the solution was cooled to room temperature. The precipitated fraction was filtered. The final solution contained 10% lignin mass.

Preparation of carbon fiber

[0071] Step 1: impregnation

[0072] The fibers of hydrocellulose, structured precursor, were impregnated with the unstructured precursor by passing continuously into the lignin solution at a speed of 15 m / min.

[0073] Step 2: drying

[0074] The fibers impregnated with lignin were dried continuously through ovens at 140 ° C for about two minutes of residence time.

[0075] Step 3: sizing

[0076] The fibers having a lignin deposit were sized in a flame retardant formulation in aqueous base comprising 160 g / dm 3 NH 3 Cl and 20 g / dm 3 Urea.

[0077] Step 4: Post sizing drying

[0078] The fibers coated with a lignin deposit after the size has been a drying step in the same conditions as step 2.

[0079] Step 5: carbonization

[0080] The carbonization was carried out in continuous, under a nitrogen atmosphere at an average temperature of 350 ° C for an average duration of 16 minutes.

[0081 ] Etape 6 : graphitisation

[0082] The graphitization was carried out at an average temperature of 1100 ° C under a nitrogen atmosphere to an average duration of 16 minutes.

Characteristics of the obtained carbon fibers

regular deposit

[0083] The deposition of lignin on the fiber hydrocellulose was 6-7% by weight. Quantification of mass lignin deposition can be obtained by weighing the fiber before hydrocellulose step 1 then following step 2 of drying.

[0084] Figure 2 shows an image obtained by scanning electron microscopy of a section of the carbon fibers obtained by the process according to the invention. This image shows that carbon fibers are distinct without creating agglomerate and that the interface between the carbon fiber from the fiber hydrocellulose and lignin after graphitization is not visible.

[0085] These carbon fibers have a diameter between 6 and 7 μηι which is larger than that of fibers used as hydrocelluloses structured precursor for the manufacture of such carbon fiber.

Increased carbon performance

[0086] The carbon efficiency (CR) was calculated after carbonization:

RC = (m carbonaceous material / precursor m) x 100

carbonization results are:

Fibers hydrocellulose, without deposition of lignin, carbonized (reference) 22% hydrocellulose fibers, with deposit 7% lignin, carbonized (Invention) 30%

[0087] Thus, the combination of hydrocellulose fibers with lignin to form, prior to carbonization, of hydrocellulose covered with a deposit of lignin fibers to switch from 22% to 30% carbon yield an increase of over 36%.

[0088] Furthermore, the addition of carbon nanotubes in the informal precursor containing lignin possible to further increase the carbon yield and achieve carbonic yields of 35%, an overall increase of almost 60% of carbon performance.

Optimization of the process parameters

The temperature conditions were adjusted to obtain the same mechanical properties of the fibers, from the hydrocellulose no deposit lignin fibers (reference) and from the hydrocellulose fibers having undergone the process of the invention:

Tensile strength: 500-600 MPa,

Elongation: 4-5%, and

Shrinkage / elongation fibers, set to 0% (no shrinkage, no stretching).

[0089] These fibers have an elongation at break higher than conventional carbon fibers.

[0090] The average temperature of the results of these tests are presented in the table below:

[0091] These results show that the process according to the invention reduces the temperature required for conventional three stages in the manufacture of carbon fibers. This temperature reduction ranges between 20 and 55% depending on the steps. It corresponds more generally to a reduction in the energy needed to transform carbon fibers in fiber. Such energy savings can be translated on an industrial scale by a decrease in manufacturing costs of the carbon fibers.

[0092] These examples show that treatment of precursor lignin by hydrocellulose possible to increase the carbon yield and decrease the temperature of high-temperature furnaces for the production of fibers of the same quality.

[0093] Thus, the present invention includes the use of a natural resource, cellulose, at the base of a structured precursor combined with another natural resource, lignin, as unstructured precursor to obtain a carbon fiber or a set of lighter carbon fiber, more effective performance char and giving carbonized material at lower cost precursors such as PAN fibers.

[0094] The carbon fiber obtained by the process of the invention may advantageously be used in place of fiberglass or carbon fiber vector for the manufacture of parts in thermoplastic or thermosetting materials which may be used particularly in the aerospace, automotive, wind energy, naval, building construction, sport. These fibers of the invention have several advantages, in particular a reduction in the weight of the structures because the fibers according to the invention have a lower density than the glass fiber and conventional carbon fibers.

claims

Production method (1) of a fiber or of a set of highly carbonaceous fibers (2), characterized in that it comprises combining (100) a structured precursor (10) comprising a fiber or a set of fibers of hydrocellulose, and an unstructured precursor (15), further comprising lignin or a lignin derivative, which is in the form of a solution having a viscosity lower than 15 000 mPa.s, and most preferably less than 10 000 mPa · s ~ at, the temperature at which occurs the combining step (100), so as to obtain a fiber or a set of hydrocellulose covered with said lignin fibers or lignin derivative (20) , said method further comprising the steps of:

- a thermal and dimensional stabilization step (200) of the fiber or set of fibers hydrocellulose covered with said lignin (20) so as to obtain a fiber or a set of hydrocellulose covered with a deposit fibers lignin or lignin derivative (30), and

- a carbonization step (300) of the fiber or set of hydrocellulose covered with a deposit of lignin fibers (30) so as to obtain a fiber or a set of highly carbonaceous fibers (2).

A manufacturing method according to claim 1, characterized in that the structured precursor (10) comprises a twisted multi-filament, multi-filament untwisted, a set of non-woven fibers, or a set of woven fibers.

Production method according to one of claims 1 or 2, characterized in that the unstructured precursor (15) comprises between 1 and 50%, preferably between 5% and 15% by weight lignin or a lignin derivative .

A manufacturing method according to any one of claims 1 to 3, characterized in that the unstructured precursor (15) is an aqueous solution or an organic solution or a mixture of both.

A manufacturing method according to any one of the preceding claims, characterized in that the structured precursor (10) comprises at least one fiber hydrocellulose whose diameter is between 0.5 and 300 μηι μηι, preferably between 1 and μηι 50 μηι.

6. The manufacturing method according to any one of the preceding claims, characterized in that the structured precursor (10) and / or unstructured precursor (15) comprises carbon nanotubes, said carbon nanotubes being present at a concentration of between 0.0001% and 10% by weight, and preferably between 0.01% and 1% by weight.

7. The manufacturing method according to any one of the preceding claims, characterized in that the combining step (100) is impregnated.

8. Manufacturing process according to any one of the preceding claims, characterized in that the combination of steps (100) and thermal and dimensional stabilization (200) are repeated one or more times.

9. Manufacturing process according to any one of the preceding claims, characterized in that it further comprises, before the carbonization step (300), the steps of:

- a sizing step (210) of contacting the fiber or set of hydrocellulose covered with a deposit of lignin fibers (30) with an aqueous solution comprising at least one flame retardant, said flame retardant compound capable be selected from: potassium, sodium, phosphate, acetate, chloride, and urea, and

- sizing a post drying step (220).

10. The manufacturing method according to claim 9, characterized in that the sizing steps (210) and post drying sizing (220) are repeated one or more times.

January 1. A manufacturing method according to any one of the preceding claims, characterized in that it further comprises, after the step of carbonization (300), a step of graphitization (400).

12. The manufacturing method according to any one of the preceding claims, characterized in that it further comprises, after the carbonization step (300), a sizing step (500) of contacting the fiber or all highly carbonaceous fibers (2) with a solution comprising at least one organic component which can comprise at least one silane derivative or silane and / or at least one derivative siloxane or siloxane.

13. A fiber or set of hydrocellulose covered with a deposit of lignin fibers (30) as an intermediate product obtained after the thermal and dimensional stabilization step (200) of the manufacturing method according to any one of the preceding claims, characterized in that the ratio of the mass of fiber mass lignin or lignin derivative is between 1/2 and 100/1.

14. A fiber or set of hydrocellulose covered with a deposit of lignin fibers (30) according to claim 13, characterized in that said depositing comprises between 0.50% and 50% by weight of flame retardant, preferably between 2 % and 30 wt%.

15. A fiber or set of highly carbonaceous fibers (2) obtained by the process according to one of claims 1 to 12.

16. A fiber or set of highly carbonaceous fibers (2) obtained from the combination of a structured precursor (10) and an unstructured precursor (15), characterized in that the structured precursor (10) comprises a fiber or an assembly of fibers of hydrocellulose, in that the unstructured precursor (15) further comprises lignin or a lignin derivative and in that said fiber or set of fibers present, after the carbonization step (300), a density of between 0.20 and 1, 95 g / cm 3 , preferably between 1 45 and 1 60 g / cm 3 .

17. Use of highly carbonaceous fibers or fiber assemblies according to claim 15 or 16 for the manufacture of pieces in thermoplastic or thermoset composites.

18. thermoplastic or thermosetting composite material obtained according to claim 17, characterized in that they have an identical lower volume weight of at least 5% by weight of conventional thermoplastic or thermoset composites.