Method for preparing multifunctionalized cellulose and its use for preparing multifunctionalized nanofibrillated cellulose - Patents.com

Abstract

The present invention relates to a method for preparing multifunctionalized cellulose, comprising subjecting cellulose fibers to a first functionalization step for grafting a first organic functional group to the cellulose and a second functionalization step for grafting a second organic functional group to the cellulose in one pot simultaneously in an alkaline reaction medium. The thus obtained multifunctionalized cellulose fibers, comprising at least carboxyl functions, are particularly suitable for being subjected to a nanofibrillation process for preparing multifunctionalized nanofibrillated cellulose.

Description

[Technical field]

[0001] The present invention is in the general field of valorization of renewable resources, particularly cellulose.

[0002] More particularly, the present invention relates to a method for preparing multifunctionalized cellulose fibers.The present invention also relates to a more global method for preparing multifunctionalized nanofibrillated cellulose, as well as the multifunctionalized nanofibrillated cellulose obtained by such a method and its use in composite materials. [Background technology]

[0003] Valorization of cellulose, the most abundant renewable resource on earth, is considered one of the most effective approaches towards sustainability. Its abundance, low cost, and biodegradability make it a highly valuable candidate for the preparation of bio-based materials to replace fossil resources.

[0004] Many methods have been proposed in the prior art to modify cellulose in order to adapt its surface properties to the applications for which it is intended to be used. Most of these methods involve grafting a single functional group, e.g., a hydrophobic group, onto the cellulose surface. As many applications require cellulose to have multiple functions, some methods have also been proposed to graft two different functional groups. One of these methods involves imparting carboxymethyl and aldehyde functional groups to cellulose fibers and is described, for example, in Sichinga et al., 2022, Cellulose, 29(2): 799-815. However, all methods developed so far to prepare multifunctional cellulose are costly and time-consuming.

[0005] There remains a need for a method for preparing multifunctionalized cellulose fibers in short reaction times, at low cost and in high yields, which is all the more important since multifunctionalized cellulose fibers can be used to prepare multifunctionalized nanofibrillated cellulose, which has applications in many fields.

[0006] Nanofibrillated cellulose, also called cellulose nanofibers or cellulose nanofibrils (CNF), is composed of nano-sized cellulose fibers with widths in the nanometer range, typically 5-15 nm, and lengths in the micrometer range, and has attracted considerable scientific and commercial interest due to its attractive properties, such as high aspect ratio, high strength and stiffness, low density, transparency, high surface area, and low thermal expansion, as well as its abundance, renewable and recyclable nature. Due to these excellent properties, nanofibrillated cellulose is produced and used in a wide range of applications, including packaging, paper and cardboard, composites, adhesives, absorbents, electronics, medical products, pharmaceuticals, and cosmetics.

[0007] Despite its excellent properties, nanofibrillated cellulose is still underutilized due to some constraints related to its production. Generally, nanofibrillated cellulose is prepared by breaking down cellulose fibers into fine fragments, typically in the initial form of delignified wood pulp. However, the mechanical processing methods carried out for this purpose, generally homogenization or high-pressure microfluidization, involve high energy consumption to break down fibers to nanometer scale and tend to damage the nanofiber structure by reducing its molar mass and crystallinity.

[0008] To facilitate the nanofibrillation process and limit its energy requirements, two main types of strategies have been developed in the prior art to pretreat cellulose fibers: enzymatic and chemical strategies.

[0009] Enzymatic cellulose pretreatment involves the use of endoglucanase or cellulase solutions, whose hydrolytic effect disrupts the cellulose structure, thereby facilitating the subsequent mechanical processing steps. However, the energy required to shear the fibers is still high, necessitating multiple passes through homogenizers or high-pressure microfluidizers. Furthermore, the quality of the resulting nanofibers, especially their dispersibility, is often poor.

[0010] Chemical pretreatment of cellulose fibers aims to introduce ionic groups on the fiber surface, leading to electrostatic repulsion and thereby improving the colloidal stability of nanofibril dispersions, after which mechanical shearing becomes much easier. Two main methods have been proposed for this purpose: oxidation catalyzed by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical and carboxyalkylation, especially carboxymethylation.

[0011] Oxidation catalyzed by TEMPO was proposed as one of the most promising methods for the production of cellulose nanofibers. Indeed, TEMPO converts the primary hydroxyl groups at C6 of the cellulose chains into carboxyl groups, which creates electrostatic repulsion and facilitates the separation of cellulose nanofibers during subsequent mechanical treatment. The use of TEMPO oxidation reduces the energy costs of the process. However, it results in the generation of large amounts of toxic waste that are difficult to handle on an industrial scale and a significant decrease in the degree of polymerization (DP) of the cellulose chains occurs during the oxidation. Moreover, the presence of toxic residual reactive species in the obtained reaction products limits its use and negatively affects the properties of CNFs over time.

[0012] Controlled carboxymethylation, which has traditionally been developed for the complete solubilization of cellulose fibers, can be seen as a strategy to promote nanofibrillation. For this purpose, cellulose fibers are first impregnated with monochloroacetic acid (MCA) and then their hydroxyl groups are activated with a concentrated sodium hydroxide (NaOH) solution, leading to Williamson etherification of the hydroxyl groups of the cellulose chains. The functional groups introduced into the cellulose polymer, more specifically the degree of substitution (DS), which is the average number of carboxymethyl groups, can be controlled by experimental conditions such as the ratio of MCA to NaOH, the temperature, and the reaction time. The carboxyl groups thus introduced into the cellulose chains promote the disintegration of the fibers and the acquisition of CNFs, especially since the replacement of hydroxyl groups with carboxymethyl groups reduces the formation of irreversible hydrogen bonds in the cellulose polymer.

[0013] A barrier to the industrial use of CNFs is the difficulty of adapting their surface properties to a specific application. Carboxymethylated CNFs are generally commercially available without further modification, limiting their use for applications that require high compatibility and / or interaction with some other components, such as organic components, for example as reinforcing materials in hydrophobic polymer matrices in the composite field. In many industrial applications of nanofibrillated cellulose, such as in the composite field, packaging industry, separation techniques such as filtration and purification, hydrogels or aerogels, it is indeed necessary to introduce additional functionality, such as additional functions, additional properties, additional reactivity, etc., to the cellulose surface. For most of these applications, it is currently proposed to functionalize the nanofibrillated cellulose by chemical post-treatment after the nanofibrillation has taken place, which generally increases the production costs and the environmental impact.

[0014] The prior art, exemplified by the publication of Kaldeus et al., Cellulose, 2018, 25: 7031-7042K, proposes the preparation of bifunctionalized cellulose nanofibrils by a process that includes the one-pot preparation of bifunctionalized cellulose fibers with carboxymethyl and additional functional groups, more specifically allyl or propargyl functional groups, prior to the nanofibrillation step. For this purpose, the cellulose fibers are first subjected to a carboxymethylation step and then to an etherification reaction by contacting them with allyl bromide or propargyl bromide in an alkaline medium. However, this method requires large amounts of reactants and long reaction times, and moreover does not allow the grafting of more than 0.3-0.5 mmol of carboxymethyl groups per gram of cellulose to the cellulose surface. The document also discloses that the simultaneous addition of allyl bromide or propargyl bromide with monochloroacetic acid leads to extremely low values ​​of total charge on the fibers, which are therefore discarded. Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention aims to propose a method for the preparation of multifunctionalized cellulose fibers, as well as multifunctionalized nanofibrillated cellulose from them, in short reaction times, at low cost and preferably with high yields. [Means for solving the problem]

[0016] The inventors have now found that such an objective can be achieved by a specific method that allows grafting two or even more functional groups onto a cellulose polymer in the form of a solid fiber by a one-pot simultaneous functionalization reaction. One of these functional groups can be a carboxyl-containing group, which facilitates the subsequent nanofibrillation step, if necessary. With regard to a more global method of preparing multifunctionalized nanofibrillated cellulose, the inventors have applied this specific method in particular to simultaneously multifunctionalize cellulose fibers with carboxyl-containing groups, such as carboxymethyl groups, and one or more additional functional groups, before subjecting them to a nanofibrillation treatment. The present inventors have unexpectedly found, contrary to the teachings of the above-mentioned document by Kaldeus et al., that under certain conditions, more particularly when carrying out a certain reactant concentration, by carrying out this particular method for simultaneously achieving carboxylation, e.g., carboxymethylation, and additional functionalization of cellulose fibers, multifunctionalized cellulose fibers can be obtained, and that this simultaneous additional functionalization does not interfere with the subsequent carboxylation, e.g., carboxymethylation, so that there is no significant decrease in the total carboxyl charge, e.g., carboxymethyl charge, grafted to the cellulose fibers, compared to cellulose fibers that have only been subjected to carboxylation, e.g., carboxymethylation. This simultaneous additional functionalization of cellulose fibers does not interfere with the subsequent nanofibrillation step of the overall method for producing multifunctionalized CNFs from cellulose fibers. This nanofibrillation step is also easier than the nanofibrillation of non-carboxylated, e.g., non-carboxymethylated cellulose fibers.

[0017] Thus, according to a first aspect, the present invention provides a method for preparing multifunctionalized cellulose fibers, comprising the steps of: a first functionalization step for grafting a first organic functional group onto the cellulose polymer by reacting the cellulose with a first reactant of organic type comprising halogen atoms and / or vinyl and / or phenyl groups and said first functional group and not comprising a hydroxyl functional group, and a second functionalization step for grafting second organic functional groups different from the first functional groups onto the cellulose polymer by reacting the cellulose with a second reactant of organic type different from the first reactant, the second functional group containing halogen atoms and / or vinyl and / or phenyl groups and not containing hydroxyl functional groups. The present invention relates to a method comprising subjecting a

[0018] According to the invention, the first functionalization step and the second functionalization step are carried out simultaneously in one pot in a reaction medium, and the first reactant and the second reactant are each present in said reaction medium in an amount ranging from 0.015 to 10 mmol per gram of cellulose.

[0019] The method of the present invention provides multi-functionalized cellulose fibers in a single step carried out under conditions suitable for covalently grafting a first functional group and a second functional group onto a cellulose polymer, much more rapidly than prior art methods.

[0020] The method of the invention makes it possible to simultaneously functionalize cellulose fibers with any combination of functional groups, and even with carboxyl and primary and / or secondary amine functional groups, although in the latter case the degree of substitution of the cellulose polymer is rather low.

[0021] Thus, in certain embodiments of the present invention, the first reactant and the second reactant do not simultaneously comprise a carboxyl functional group and a primary or secondary amine functional group. By this is meant that if the first reactant comprises a carboxyl functional group, then neither the first nor the second reactant comprises a primary or secondary amine functional group, and if the second reactant comprises a carboxyl functional group, then neither the first nor the second reactant comprises a primary or secondary amine functional group. Similarly, if the first reactant comprises a primary or secondary amine functional group, then neither the first nor the second reactant comprises a carboxyl functional group, and if the second reactant comprises a primary or secondary amine functional group, then neither the first nor the second reactant comprises a carboxyl functional group.

[0022] More generally, in certain embodiments of the methods of the invention, the first reactant and the second reactant do not simultaneously contain two or more functional groups that are likely to react with each other under the operating conditions so as not to compete with the reaction of those reactants with cellulose.

[0023] The term carboxyl, as used herein, encompasses both the acid form and the carboxylate ion form.

[0024] By functional group, we mean a group having at least one functional group of any type that confers a particular characteristic / property / capability. The term "functional group," as used herein, encompasses not only the functional group itself, but also larger organic chemical moieties that contain at least one functional group.

[0025] The functional groups grafted to the cellulose polymer according to the invention may be any groups that exhibit functions that may be of interest for a given application of the multifunctionalized cellulose fibers. These functional groups are preferably selected to broaden the field of application of the cellulose fibers in applications that require specific mechanical properties and / or functionality, for example applications that require tuning the surface properties of the cellulose, such as polarity and / or charge. The functional groups may include, for example, polymerization initiator functional groups, such as benzophenone type or α-bromoisobutyryl type, for forming polymer chains, such as acrylates, styrenes, on the fiber surface, chromophores, hydrophobic groups, groups with positive or negative charges, alkene or alkyne groups for click chemistry, such as azide-alkyne cycloaddition, etc. By way of example, the functional groups may be selected from the group consisting of specific functional groups, such as carbonyl or carboxylic acid / carboxyl functional groups, alkyl, allyl, alkyloyl or alkyne chains, aromatic rings, benzophenone, etc.

[0026] In a particular embodiment of the present invention, one of the functional groups, for example the first functional group, is a carboxy-containing group, in particular a carboxyl (or carboxylic acid) group or a carboxyalkyl group, preferably a C1-C6 alkyl, for example of the methyl or ethyl-containing type. Such a feature is extremely advantageous in terms of a more global preparation of multifunctionalized nanofibrillated cellulose. And the first reactant can be a haloformic acid, such as chloroformic acid, or a haloacetic acid, such as monochloroacetic acid, or a halopropionic acid, such as chloropropionic acid, or more generally an alkyl-haloacetic acid, such as an alkyl-chloroacetic acid. Also, the first functionalization step can qualify as a carboxylation step, more particularly a carboxyalkylation step, for example a carboxymethylation step, in which a carboxymethyl group is grafted to the cellulose polymer.

[0027] Carboxyl-containing groups can also be grafted onto cellulose fibers using reactants that do not contain halogen atoms but contain vinyl groups, such as acrylic acid or its salts, e.g., sodium acrylate, and / or optionally substituted phenyl groups, such as cinnamic acid or its salts.

[0028] In a particular embodiment of the invention, at least one of the first and second functional groups is of hydrophobic type. The multifunctionalized cellulose fibers obtained by the method of the invention are then advantageously compatible with matrices based on hydrophobic polymers. Hydrophobic groups that can be used in the context of the invention are, for example, alkyl, aryl or alkyne chains, aromatic rings or polymerization initiators such as benzophenone that allow the polymerization of acrylates or styrenes on the surface of the cellulose fibers.

[0029] As an example, the second functional group can be a dye.

[0030] Examples of functional groups that can be grafted onto cellulose by the method of the present invention include: Benzophenone derivatives such as (4-methylphenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone, which can be grafted onto cellulose polymers by reacting with (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone under alkaline conditions; allyls which can be grafted onto cellulose polymers by reaction with allyl chloride or allyl bromide under alkaline conditions; alkyl acetates, the alkyl group of which preferably contains from 1 to 20, especially from 1 to 12 carbon atoms, e.g. ethyl acetate or octyl acetate, which can be grafted to the cellulose polymer under alkaline conditions by reaction with ethyl chloroacetate or ethyl bromoacetate, respectively octyl chloroacetate or octyl bromoacetate; Alkyl chains, preferably C1-C20, especially C1-C12 alkyl chains, which can be grafted onto the cellulose polymer by reaction with 1,10-dibromodecane under alkaline conditions, e.g. decane; Alkoyl chains, preferably C2-C20, especially C2-C12 alkoyl chains, which can be grafted onto cellulose polymers, for example by reaction with lauroyl chloride under alkaline conditions; For example, benzoic acid can be grafted onto cellulose polymers by reacting with 2-iodobenzoic acid under alkaline conditions. There is.

[0031] More generally, in a preferred embodiment of the invention, the first reactant and / or said second reactant has the general formula (I): YR (I) having During the ceremony, Y represents a halogen atom, a vinyl group or a phenyl group, which may be optionally substituted; and R represents a moiety that contains a functional group, with the proviso that R does not contain a hydroxyl group.

[0032] In particular, Y represents a phenyl group, said phenyl group being a halogen atom, for example a chlorine or bromine atom, linear, branched and / or cyclic hydrocarbon groups, saturated and / or unsaturated, aromatic or non-aromatic, optionally substituted and optionally containing one or more heteroatoms and / or one or more groups containing at least one heteroatom, for example -OR1, where R1 represents an alkyl group, preferably C1-C6, for example a methyl or ethyl group, NO2, SR2O or SO2R2, where R2 represents an alkyl group, preferably a C1-C6 group, for example a methyl or ethyl group; may be substituted with one or more groups selected from

[0033] In a particular embodiment of the invention, in formula (I), R represents a linear, branched and / or cyclic C2-C20 hydrocarbon group, saturated and / or unsaturated, aromatic or non-aromatic, containing functional groups, optionally substituted, optionally interrupted by one or more heteroatoms and / or one or more groups containing at least one heteroatom, and R does not contain a hydroxyl group.

[0034] In particular, R may represent a benzophenone derivative, such as (4-methylphenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone, an allyl group, an alkyl acetate group, where the alkyl group preferably comprises 1 to 20, especially 1 to 12, carbon atoms, an alkyl chain, preferably C1-C20, especially C1-C12, an alkoyl acid, preferably C2-C20, especially C2-C12, a benzoic acid group, and the like, which may be optionally substituted.

[0035] The method according to the invention may furthermore correspond to one or more of the following characteristics, implemented individually or in each of their technically functional combinations:

[0036] Both the first and second functionalization steps of the method of the present invention preferably comprise a Williamson etherification reaction involving the hydroxyl groups of the cellulose polymer. The functionalization step is carried out by contacting the cellulose with reactants in an alkaline reaction medium under conditions capable of causing an etherification reaction of the hydroxyl groups of the cellulose polymer.

[0037] The cellulose fibres used in the process of the invention are preferably fibres of wood origin: they can be obtained by disintegrating delignified wood pulp, for example by stirring the dispersion in water.

[0038] In a preferred embodiment of the present invention, the method comprises dispersing cellulose fibers in water before subjecting them to the first and second functionalization steps. It is then preferred not to include intermediate solvent exchange steps between the dispersion step and the first and second functionalization steps. The inventors have in particular noticed that such intermediate solvent exchange steps, from water to ethanol and then from ethanol to isopropanol, typically carried out in prior art methods for carboxymethylating cellulose fibers, such as the method disclosed in the above-mentioned publication by Kaldeus et al., are not necessary for the successful carboxymethylation, or more generally functionalization, of cellulose polymers in the framework of the method of the present invention. Avoiding such steps in the context of the present invention advantageously reduces the production costs of polyfunctionalized cellulose and thereby limits the amount of organic waste generated.

[0039] In a preferred embodiment of the invention, after dispersing the cellulose fibers in water, the process includes separating them from the water, preferably by filtration, before proceeding to the next step of the process.

[0040] The method of the present invention may then optionally include a step of spacing the cellulose fibers apart, which may be carried out by any technique known to those skilled in the art.

[0041] The method of the present invention can be carried out to prepare bifunctional cellulose fibers using two reactants, each containing a functional group to be grafted to the cellulose polymer. It is also possible to use more such reactants, for example three such reactants, each containing a different functional group, to prepare cellulose fibers with three or even more functional groups, still in one pot.

[0042] In a particular embodiment of the invention, the method comprises at least one further functionalization step for grafting at least one further organic functional group, i.e. a functional group different from the first and second functional groups, to the cellulose polymer by reacting the cellulose fibers with at least one further reactant comprising a halogen atom and said further functional group and not comprising a hydroxyl functional group, the further functionalization step being carried out simultaneously with the first and second functionalization steps in one pot in an alkaline reaction medium under conditions suitable for covalently attaching the further functional group to the cellulose polymer, and such further reactant being present in the reaction medium in an amount of 0.015 to 10 mmol per g of cellulose.

[0043] In certain embodiments of the invention, the first reactant, the second reactant and the further reactant do not simultaneously contain carboxyl functional groups and primary or secondary amine functional groups, or more generally functional groups that may react together under those operating conditions.

[0044] The further functional group, the further reactant and the further functionalization step may generally have one or more of the characteristics described above or below with respect to the first and second functional groups, the first and second reactants and the first and second functionalization steps of the method of the invention, respectively. The further reactant may in particular have the general formula (I):

[0045] In a particular embodiment of the invention, the first reactant and the second reactant, and where appropriate each of the further reactants, are present in the reaction medium in an amount of 0.03 to 2 mmol of reactant per gram of cellulose, more preferably 0.03 to 1 mmol of reactant per gram of cellulose, at such concentrations, in the context of the invention of polyfunctionalizing cellulose fibers, simultaneous grafting of all functional groups onto the cellulose polymer is successful.

[0046] The method of the present invention does not involve first dispersing cellulose fibers in an alkaline medium to swell them and then adding reactants for the functionalization step thereto, after which a multifunctionalized cellulose in a solubilized state is indeed obtained, which is not compatible with the objective of the present invention of forming multifunctionalized cellulose fibers.

[0047] In order to obtain polyfunctionalized cellulose fibers as required by the present invention, i.e. cellulose in solid form, such a prior dispersion of the cellulose fibers in an alkaline reaction medium should be avoided. In such an embodiment, the method of the present invention then preferably comprises, prior to the first and second functionalization steps and, where appropriate, further functionalization steps, impregnating the cellulose fibers, preferably successively, with a first impregnation solution comprising the first reactant, a second impregnation solution comprising the second reactant, and, where appropriate, one or more further impregnation solutions, each comprising a further reactant. Each of these impregnation steps is then preferably carried out for a period of between 10 minutes and 1 hour, preferably between 10 and 40 minutes, more preferably between 20 and 40 minutes, for example about 30 minutes, preferably at room temperature.

[0048] The volume of each impregnation solution is preferably 5-50 ml per gram of cellulose. In these solutions, the reactants may be contained in any suitable solvent at a concentration necessary to achieve a ratio of 0.015-10 mmol of reactant per gram of cellulose, preferably 0.03-2 mmol of reactant per gram of cellulose, more preferably 0.03-1 mmol of reactant per gram of cellulose.

[0049] Thus, in a particular embodiment of the invention, the method comprises, prior to the functionalization step, a step of impregnating the cellulose fibers with a first impregnation solution comprising a first reactant, then a step of impregnating the cellulose fibers with a second impregnation solution comprising a second reactant, and then optionally one or more further steps of impregnating the cellulose fibers with further impregnation solutions each comprising a further reactant.

[0050] Each of these impregnation steps is preferably carried out by wetting the cellulose fibers with the impregnation solution.

[0051] The first functionalization step, the second functionalization step and, where appropriate, the further functionalization step of the method of the invention are then carried out simultaneously in the same reaction medium, according to any conventional operating protocol. The etherification reaction is preferentially induced by contacting the cellulose fibers with the reactants in the presence of an alkali, such as sodium hydroxide, preferably in a proportion of 4 to 40 mmol of sodium hydroxide per gram of cellulose. In a preferred embodiment of the invention, when the cellulose fibers have been previously impregnated with the reactants, the fibers are then introduced into a reaction medium containing an alkali compound, such as sodium hydroxide, dissolved in a suitable vehicle, together with possible residues of the impregnation solution that would not have been impregnated into the fibers during the impregnation step of the method.

[0052] In a particular embodiment of the invention, the reaction medium of the functionalization step is in an alcoholic medium, preferably a weak alcoholic medium, for example containing or consisting of isopropanol or a mixture of isopropanol and methanol. Preferably, this reaction medium is free of methanol.

[0053] The first and second functionalization steps and, where appropriate, the further functionalization steps are preferentially carried out for a period of 30 to 90 minutes, more preferably 50 to 70 minutes, for example about 60 minutes. Such short reaction times are advantageously sufficient to ensure a high degree of functionalization of the cellulose polymer with all functional groups.

[0054] In a preferred embodiment of the invention, the first and second functionalization steps and, where appropriate, the further functionalization steps are carried out at a temperature of 60 to 82° C., preferably 65 to 82° C. They are preferentially carried out at a temperature of 65 to 75° C., thereby further reducing the energy requirements of the process.

[0055] As indicated above, in certain embodiments of the present invention, particularly suitable for preparing multifunctionalized nanofibrillated cellulose from multifunctionalized cellulose fibers prepared by the method of the present invention, the first functional group is a carboxyl-containing group, in particular a carboxyl group or a carboxyalkyl group, preferably containing C1-C6 alkyl, such as carboxymethyl or carboxyethyl groups. The first reactant is then preferably an alkyl-haloacetic acid, preferably a C1-C5 alkyl-haloacetic acid, such as a haloacetic acid, such as monochloroacetic acid, or a halopropionic acid, such as chloropropionic acid. The first reactant may also be halogen-free and contain a vinyl group, such as acrylic acid or a salt thereof, such as the sodium salt, or an optionally substituted phenyl group, such as cinnamic acid.

[0056] The method according to the invention then comprises: a carboxylation, e.g. carboxyalkylation, in particular carboxymethylation, step for grafting carboxyl-containing groups, in particular carboxyalkyl functional groups, such as carboxymethyl groups, onto the cellulose polymer, e.g. by reacting the cellulose fibres with an alkyl-haloacetic acid, in particular a haloacetic acid, e.g. monochloroacetic acid, and a second functionalization step for grafting the cellulose polymer with a second functional organic group, i.e. a functional group other than the carboxyl-containing group, in particular the carboxyalkyl group, of the carboxylation / carboxyalkylation step, by reacting the cellulose fiber with a second reactant comprising a halogen atom and a second functional group, not comprising a hydroxyl functional group and, optionally, also not comprising a primary amine functional group and not comprising a secondary amine functional group, and optionally a further functionalization step for grafting further functional organic groups onto the cellulose polymer, i.e. functional groups other than the carboxyl-containing groups of the carboxylation / carboxyalkylation step, in particular the carboxyalkyl groups, and other than the second functional groups, by reacting the cellulose fibres with further reactants which contain halogen atoms and further functional groups, but do not contain hydroxyl functional groups and, optionally, also do not contain primary and secondary amine functional groups. are subjected simultaneously in one pot in an alkaline reaction medium under suitable conditions to covalently graft carboxyl-containing groups, in particular carboxyalkyl groups, second functional groups and, where appropriate, further functional groups onto the cellulose polymer to form the fibers.

[0057] The simultaneous carboxylation / carboxyalkylation, in particular carboxymethylation, step and the second functionalization step of the method, and optionally a further functionalization step, advantageously result in multifunctionalized cellulose fibers, in which both carboxyl-containing groups, in particular carboxyalkyl, for example carboxymethyl groups, and second functional groups are grafted to the surface in one step. The degree of substitution of the cellulose polymer with carboxyl-containing groups, in particular carboxyalkyl, for example carboxymethyl groups, which can be measured, for example, by conductivity measurements, as described in detail herein below, is not significantly different from that obtained when applying only the carboxylation / carboxyalkylation, in particular carboxymethylation step to the cellulose fibers. The second functionalization step of the method of the invention advantageously does not affect the carboxylation / carboxyalkylation, in particular carboxymethylation, of the cellulose fibers, nor their morphology and colloidal stability.

[0058] Secondly, the method of the present invention advantageously provides a simple synthetic route to introduce several functional groups, including carboxyl functional groups, particularly negative charges derived from carboxymethyl groups, onto the surface of cellulose fibers by a one-pot simultaneous reaction.

[0059] The carboxyalkylation, especially the carboxymethylation step, preferably comprises subjecting cellulose fibers to an alkaline reaction medium under conditions that allow the etherification reaction of the hydroxyl groups of the cellulose polymer to occur. Halogen atoms and carboxyl-containing groups, such as carboxyalkyl groups, in particular monochloroacetic acid; Vinyl groups and carboxyl groups or carboxyl-containing groups, such as acrylic acid or its salts; Optionally substituted phenyl groups and carboxyl-containing groups, such as -CH=CH-COOH substituting the phenyl group The reaction is carried out by contacting the reaction mixture with a reactant containing

[0060] Preferably, a ratio of 0.1 to 10 mmol of such reactants, especially monochloroacetic acid, per gram of cellulose is applied.

[0061] When the second reactant is used in an amount of 0.015-10 mmol / g cellulose, preferably 0.03-2 mmol / g cellulose, more preferably 0.03-1 mmol / g cellulose, the grafting of the second functional group on the cellulose fibres is successful without significantly interfering with the carboxylation, particularly the carboxyalkylation, more particularly the carboxymethylation step.

[0062] The impregnation of the cellulose fibers with the impregnation solution containing the reactants for the carboxylation / carboxyalkylation step, in particular monochloroacetic acid, and the impregnation of the cellulose fibers with the second impregnation solution containing the second reactant preferably work in either order. Preferably, the cellulose fibers are first impregnated with the reactants for the carboxylation / carboxyalkylation step, in particular monochloroacetic acid, and then with the second reactant for the second functionalization step.

[0063] In a particular embodiment of the invention, the method comprises, in sequence: Dispersing cellulose fibers in water; separating the cellulose fibers from the water by filtration; wetting the cellulose fibres with a first impregnation solution containing a reactant for the carboxylation / carboxyalkylation step, for example monochloroacetic acid (MCA), in a suitable solvent, for example an alcoholic solvent, in particular isopropanol, preferably in a proportion of 0.1-10 mmol of reactant per gram of cellulose, preferably in a proportion of 5-50 ml of first impregnation solution per gram of cellulose, and impregnating the cellulose fibres with the reactant, preferably at room temperature, for preferably 20-40 minutes; wetting the cellulose fibres with a second impregnation solution containing a second reactant for the second functionalization step in a suitable solvent in a proportion of 0.015-10 mmol, more preferably 0.03-0.1 mmol of second reactant per gram of cellulose, preferably in a proportion of 5-50 ml of second impregnation solution per gram of cellulose, and impregnating the cellulose fibres with the second reactant, preferably at room temperature, for preferably 20-40 minutes; immersing the cellulose fibres, if appropriate together with the remainder of the impregnating solution that has not been impregnated, in a bath of a solution containing an alkali in a suitable medium, for example sodium hydroxide in a weak alcoholic medium, preferentially isopropanol, preferably in a proportion of 4 to 40 mmol of sodium hydroxide per gram of cellulose, and allowing the carboxylation / carboxyalkylation, in particular the carboxymethylation, and the second functionalization reaction to take place, preferably for about 1 hour, preferentially at a temperature between 60 and 75° C., preferably between 65 and 75° C., for example at about 70° C., preferably under gentle stirring. Includes.

[0064] This allows bifunctionalized cellulose fibers containing a carboxyl group-containing functional group and an additional functional group to be obtained by a one-pot simultaneous reaction.

[0065] As an example, the second functionalization step of the method of the invention can be carried out to simultaneously introduce into the cellulose polymer carboxyl-containing groups, in particular carboxymethyl groups, as well as ethyl acetate groups, allyl groups, decane groups or benzophenone derivatives such as (4-methylphenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone, alkoyl groups, benzoic acid groups, etc.

[0066] In another particular embodiment of the invention, the method comprises, in sequence: Dispersing cellulose fibers in water; separating the cellulose fibers from the water by filtration; wetting the cellulose fibres with a first impregnation solution containing a reactant for the carboxylation / carboxyalkylation step, in particular monochloroacetic acid (MCA), in a suitable solvent, for example an alcoholic solvent, in particular isopropanol, preferably in a proportion of 0.1 to 10 mmol of such reactant per gram of cellulose, preferably in a proportion of 5 to 50 ml of first impregnation solution per gram of cellulose, and impregnating the cellulose fibres with the reactant, preferably at room temperature, for preferably 20 to 40 minutes, wetting the cellulose fibres with a second impregnation solution in a suitable solvent in a proportion of 0.015-10 mmol, more preferably 0.03-0.1 mmol, in particular 0.03-0.1 mmol of the second reactant for the second functionalization step per gram of cellulose, preferably in a proportion of 5-50 ml of the second impregnation solution per gram of cellulose, and impregnating the cellulose fibres with the second reactant, preferably at room temperature, for preferably 20-40 minutes; wetting the cellulose fibres with a further impregnation solution of a further reactant for the further functionalization step in a suitable solvent in a proportion of 0.015 to 10 mmol, preferably 0.03 to 1 mmol, in particular 0.03 to 0.1 mmol of said further reactant per gram of cellulose, preferably in a proportion of 5 to 50 ml of further impregnation solution per gram of cellulose, preferably at room temperature, preferably for 20 to 40 minutes to impregnate the cellulose fibres with the further reactant, immersing the cellulose fibres, if appropriate together with the remainder of the impregnating solution that has not been impregnated, in a bath of a solution containing an alkali in a suitable medium, for example sodium hydroxide in a weak alcoholic medium, preferentially isopropanol, preferably in a proportion of 4 to 40 mmol of sodium hydroxide per gram of cellulose, and allowing the carboxylation / carboxyalkylation, in particular carboxymethylation, second functionalization and further functionalization reactions to take place, preferably for about 1 hour, preferentially at a temperature between 65 and 75° C., for example about 70° C., preferably under gentle stirring. Includes.

[0067] This allows the production of trifunctional cellulose fibers containing a carboxyl-containing functional group and two additional functional groups through a one-pot simultaneous reaction.

[0068] The same process can be applied to introduce even more functional groups into the cellulose polymer by simply adding the step of impregnating the cellulose fibers with additional reactants before immersing them in the alkaline reaction medium.

[0069] As an example, the second and further functionalization steps of the method of the invention can be carried out to simultaneously introduce carboxyl-containing groups, particularly carboxyalkyl groups, such as carboxymethyl groups, as well as ethyl acetate and allyl groups, or allyl and alkyl groups, into the cellulose polymer.

[0070] Another aspect of the invention relates to multifunctionalized cellulose fibers obtained by the process according to the invention. The functional groups carried by such multifunctionalized cellulose fibers may have any of the characteristics or a combination of characteristics described above for the process of the invention.

[0071] Examples of such polyfunctionalized cellulose fibers are functionalized with carboxyl-containing groups, such as carboxyalkyl groups, in particular those containing C1-C6 alkyl, such as carboxymethyl or carboxyethyl groups, or alkylcarboxyl groups, in particular those containing C1-C16 alkyl, such as methylcarboxyl, or phenyl-containing and carboxyl-containing groups, such as cinnamyl groups, and also include those of the following groups: Benzophenone derivatives, such as (4-methylphenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone, Allyl, Alkyl acetates, where the alkyl group preferably contains 1 to 20, in particular 1 to 12, carbon atoms, such as ethyl acetate or octyl acetate; Alkyl chains, preferably C1-C20, in particular C1-C12 alkyl chains, e.g. decane; Alkoyl chains, preferably C2-C20, in particular C2-C12 alkoyl chains, such as lauroyl chains; benzoic acid is functionalized with one or more of

[0072] Examples of such polyfunctionalized cellulose fibers according to the present invention include those containing carboxyalkyl groups, particularly C1-C6 alkyl groups, such as trifunctionalized cellulose fibers functionalized with carboxymethyl groups and at least two of ethyl acetate groups, alkyl groups, and allyl groups.

[0073] The present invention also relates to the use of the multifunctionalized cellulose fibers according to the invention for preparing composite materials which may be useful for many applications, such as, for example, in the textile sector, the packaging sector, the pulp and paper industry sector, etc.

[0074] The multifunctionalized cellulose fibers according to the invention can also be used for the preparation of microfibrillated multifunctionalized cellulose and / or multifunctionalized nanofibrillated cellulose.

[0075] Another aspect of the present invention is a process for the preparation of multifunctionalized microfibrillated cellulose, comprising subjecting cellulose fibers to the process for the preparation of multifunctionalized cellulose fibers according to the invention, preferably a carboxylation / carboxyalkylation step as described above, and then subjecting the multifunctionalized cellulose fibers thus obtained to microfibrillation.

[0076] Microfibrillated cellulose is defined herein as consisting primarily of micro-sized cellulose fibres, typically with widths of 20-50 nm and lengths in the micrometre range, in which small amounts of nano-sized cellulose particles are also found mixed in with the micro-sized fibres.

[0077] The microfibrillation step can be carried out in any manner known to the person skilled in the art, in particular by gentle shaking of the multifunctionalized cellulose fibers in an aqueous vehicle, for example at ambient temperature, for example for a period of 12 to 36 hours, in particular about 24 hours.

[0078] Another object of the invention is a multifunctionalized microfibrillated cellulose obtainable by the process for the preparation of microfibrillated cellulose according to the invention, which multifunctionalized microfibrillated cellulose is functionalized with two or more different functional groups and can have any of the characteristics or combinations of characteristics mentioned above for the process for the preparation of multifunctionalized cellulose fibers according to the invention, with the exception of the combination of t-butylcarboxamide with any of the following functional groups: Methacrylate, pent-4-ynoate, formula:

[0079] TIFF2025506191000001.tif25170

[0080] 2-methyl-3-[(prop-2-yn-1-yl)amino]propanoate, formula:

[0081] TIFF2025506191000002.tif68170

[0082] 3-(1-{2-[2-(2-methoxyethoxy)ethoxy]ethyl}-1H-1,2,3-triazol-4-yl)propanoate, and the formula:

[0083] TIFF2025506191000003.tif74170

[0084] of 3-(5-fluorescein-1H-1,2,3-triazol-4-yl)propanoate.

[0085] Examples of such polyfunctionalized microfibrillated cellulose are those containing carboxyl-containing groups, in particular carboxyalkyl groups, in particular C1-C6 alkyl groups, such as carboxymethyl or carboxyethyl groups, and the following groups: Benzophenone derivatives, such as (4-methylphenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone, Allyl, Alkyl acetates, where the alkyl group preferably contains 1 to 20, in particular 1 to 12, carbon atoms, such as ethyl acetate or octyl acetate; Alkyl chains, preferably C1-C20, in particular C1-C12 alkyl chains, e.g. decane; Alkoyl chains, preferably C2-C20, in particular C2-C12 alkoyl chains, such as lauroyl chains; benzoic acid is functionalized with one or more of

[0086] Another example of a polyfunctionalized microfibrillated cellulose according to the invention is a trifunctionalized microfibrillated cellulose functionalized with carboxyl-containing groups, in particular carboxyalkyl groups, such as carboxymethyl groups, as well as ethyl acetate groups and allyl groups.

[0087] The present invention also relates to the use of the multifunctionalized microfibrillated cellulose according to the invention for preparing a composite material which may be useful for many applications, such as, for example, in the textile sector, in the packaging sector, in the pulp and paper industry sector, etc.

[0088] The multifunctionalized microfibrillated cellulose according to the present invention can also be used to prepare multifunctionalized nanofibrillated cellulose.

[0089] Another aspect of the present invention is to provide a method for preparing cellulose fibers comprising the steps of: A process for preparing a polyfunctionalized cellulose according to the present invention, wherein one of the first and second functional groups, e.g. the first functional group, is a carboxyl-containing group, in particular a carboxyalkyl group, preferably one containing C1-C6 alkyl, e.g. a carboxymethyl group or a carboxyethyl group, or an alkylcarboxyl group, in particular one containing C1-C16 alkyl, e.g. a methylcarboxyl, or a phenyl-containing and a carboxyl-containing group, e.g. a cinnamyl group, Then, a step of nanofibrillation by mechanical treatment of the resulting multifunctionalized cellulose fibers. The present invention relates to a method for preparing a multi-functionalized nanofibrillated cellulose, the method comprising the steps of:

[0090] The presence of a large amount of negative charges on the multifunctionalized cellulose fibers originating from the carboxyl groups grafted onto their surfaces facilitates the collapse of the fibers to the nanometer scale in the subsequent nanofibrillation step, thereby reducing the energy required for nanofibrillation, and the multifunctionalized nanofibrillated cellulose is obtained without additional steps, with the same degree of nanofibrillation, and without additional energy requirements, as compared to the prior art method for preparing nanofibrillated cellulose that only carries out carboxymethylation of cellulose fibers.

[0091] In particular, the multifunctionalized cellulose fibers obtained by the concomitant first functionalization step, in particular the carboxyalkylation step, more particularly the carboxymethylation step, for grafting carboxyl-containing functional groups onto the cellulose fibers, and the second functionalization step of the method of the invention have been found by the inventors to have particularly good dispersion properties in aqueous vehicles, which can be confirmed by dynamic rheological analysis. After the microfibrillation step, which is achieved by soft stirring of the fibers in water, dispersions of such multifunctionalized cellulose fibers in water show gel-like behavior at least in the concentration range of 0.5-4.5% w / w. In the concentration range of 2-4.5% w / w, these dispersions do not even flow, indicating a high dispersion ability of cellulose microfibrils in water. Such a high dispersion ability facilitates the subsequent nanofibrillation step of the method of the invention.

[0092] The method for preparing the multifunctionalized nanofibrillated cellulose of the present invention may comprise, after a step of functionalizing the cellulose fibers, e.g. a simultaneous carboxymethylation step and a second functionalization step, and before the nanofibrillation step, a step of purifying the multifunctionalized cellulose fibers, e.g. by filtration, and then optionally washing them, e.g. with isopropanol and then with water, until a neutral pH is reached.

[0093] Also, the nanofibrillation step may optionally include a step of disintegrating the cellulose fibres to the micrometer scale, i.e. a microfibrillation step, prior to the nanofibrillation step. Such a step is particularly easy to carry out and energy-efficient due to the high degree of substitution of the fibres with carboxyl groups. In particular, it may be carried out by gently stirring the cellulose fibres in an aqueous vehicle, for example at ambient temperature, for example for 12 to 36 hours, in particular for about 24 hours.

[0094] The nanofibrillation step of the method of the invention can be carried out by any conventional technique for mechanically disrupting cellulose fibres to the nanometre scale. It can be carried out, for example, by homogenisation or high pressure microfluidisation. For example, the multifunctionalised cellulose fibres are passed through a piston pump which applies high pressure and then through a Z-shaped interaction chamber with internal diameters of 400, 200 and 100 μm, preferably at a constant flow rate, for example around 350 mL.min - 1, for example, several passes at pressures of 100, 1500 and 2000 bar, respectively.

[0095] In the context of preparing this multifunctionalized nanofibrillated cellulose, the second functional group is preferably selected to broaden the field of application of the nanofibrillated cellulose to applications requiring specific mechanical properties and / or functionality, in particular applications requiring the adjustment of the surface properties of the cellulose, such as polarity and / or charge, such as use in filtration media, reinforcement of composite materials, emulsion stabilizer for water-in-oil (w / o) or oil-in-water (o / w) systems, etc. The second functional group can include, for example, polymerization initiator functional groups, such as benzophenone type or α-bromoisobutyryl type, for forming polymer chains, such as acrylates, styrene, etc., on the fiber surface, chromophores, hydrophobic groups, groups with positive or negative charges, alkene or alkyne groups for click chemistry, such as by azide-alkyne cycloaddition, etc. By way of example, the second functional group can be selected from the group consisting of carbonyl or carboxylic acid / carboxylic acid functional groups, alkyl, allyl, alkoyl or alkyne chains, aromatic rings, specific functional groups, such as benzophenone, benzoic acid groups, etc.

[0096] In a particular embodiment of the invention, the second functional group is of hydrophobic type. The multifunctionalized nanofibrillated cellulose obtained by the method of the invention is then advantageously compatible with matrices based on hydrophobic polymers. Hydrophobic groups that can be used in the context of the invention are, for example, alkyl, aryl or alkyne chains, aromatic rings or polymerization initiators such as benzophenone that allow the polymerization of acrylates or styrenes on the surface of cellulose fibers.

[0097] Examples of second functional groups which can be grafted onto the cellulose fibres in the second functionalisation step of the process of the invention are benzophenone derivatives such as (4-methylphenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone, allyl, alkyl acetates, where the alkyl group preferably contains 1 to 20, in particular 1 to 12 carbon atoms, such as ethyl acetate or octyl acetate, alkyl chains, preferably C1-C20, in particular C1-C12 alkyl chains, such as decane, alkoyl chains, preferably C2-C20, in particular C2-C12, such as lauroyl chains, benzoic acid groups etc.

[0098] Another aspect of the invention relates to a multifunctionalized nanofibrillated cellulose, more particularly a bifunctionalized nanofibrillated cellulose, obtainable by the method according to the invention, which is functionalized by covalent grafting onto the cellulose polymer one additional functional group, preferably a carboxyl-containing group, in particular a carboxyalkyl group, preferably a C1-C6 alkyl-containing carboxyalkyl group, such as a carboxymethyl or carboxyethyl group, and preferably free of hydroxyl functions and optionally free of primary and secondary amine functions, excluding allyl, propargyl, methyltriazole-disperse red 13 and methyl 3-ethylthiolpropionate groups.

[0099] In a particular embodiment of the invention, the multifunctionalized nanofibrillated cellulose comprises 0.5-0.8 mmol of carboxyl groups, in particular carboxyalkyl groups, preferably carboxyalkyl groups containing C1-C6 alkyl, such as carboxymethyl or carboxyethyl groups, per gram of cellulose.

[0100] The additional functional group can correspond to any of the characteristics described above in relation to the second functional group.

[0101] The additional functional groups may in particular be selected from the group consisting of benzophenone derivatives, such as (4-methylphenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone, allyl, alkyl acetate, where the alkyl group preferably has 1 to 20, in particular 1 to 12 carbon atoms, such as ethyl acetate or octyl acetate, and alkyl, preferably C1-C20, in particular C1-C12 alkyl, such as decane, alkoyl chains, preferably C2-C20, in particular C2-C12 alkoyl chains, such as lauroyl chains, benzoic acid groups.

[0102] Another aspect of the invention relates to multifunctionalized nanofibrillated cellulose, in particular trifunctional or higher functionalized nanofibrillated cellulose obtainable by the process according to the invention, which is functionalized by covalently grafting to the cellulose polymer carboxyl-containing groups, in particular carboxyalkyl groups, preferably C1-C6 alkyl-containing carboxyalkyl groups, such as carboxymethyl or carboxyethyl groups, as well as at least two additional functional groups, preferably free of hydroxyl functions and, optionally, free of primary and secondary amine functions.

[0103] The additional functional groups can correspond to any of the characteristics described above in relation to the second and further functional groups.

[0104] The trifunctionalized nanofibrillated cellulose according to the invention can, for example, simultaneously have a carboxymethyl group, an ethyl acetate group or an alkyl group, and an allyl group.

[0105] As indicated above, the multifunctionalized nanofibrillated cellulose of the present invention, whether difunctionalized, trifunctionalized or further functionalized, can have any functionality required for the desired application.

[0106] Multifunctionalized nanofibrillated cellulose can, for example, have functional groups that change the nature of the interaction with other compounds, i.e. functional groups that can participate in hydrogen bonds, electrostatic interactions, etc., or functional groups that change the polarity from hydrophilic to hydrophobic, which can be advantageous for better dispersibility of the nanofibrillated cellulose in hydrophobic polymer matrices, especially in the context of the manufacture of composite materials.

[0107] Another aspect of the invention relates to the use of multifunctionalized nanofibrillated cellulose according to the invention, in particular di- or trifunctionalized nanofibrillated cellulose, for the preparation of composite materials, in particular for the reinforcement of materials based on hydrophobic polymer matrices, and in which one of the functional groups grafted to the cellulose polymer is a hydrophobic group, such as an alkyl chain, or a polymerization initiator, such as a benzophenone-containing group, and the multifunctionalized nanofibrillated cellulose is treated before use by forming polymer chains, such as acrylate chains, on its surface.

[0108] The multifunctionalized nanofibrillated cellulose according to the invention can also be used for the manufacture of new cellulose-based products intended for a number of applications, in particular in the following fields, the functionality or functionality of the nanofibrillated cellulose being appropriately selected depending on the respective specific application: In the paper industry, to improve the compatibility of nanofibrillated cellulose with synthetic polymers such as acrylates for the production of special papers - benzophenone functional groups allowing the polymerization of acrylate polymers have for example been grafted onto cellulose fibres according to the invention; In the field of packaging, in order to adjust the permeability and gas barrier properties of the material and to improve the compatibility of nanofibrillated cellulose with other components of the packaging, such as paints, hydrophobic surface coatings, etc. - benzophenone functional groups allowing the polymerization of acrylate polymers and / or alkyl chains modifying the permeability and gas transport properties of the material have for example been grafted onto cellulose fibres according to the invention; In the production of porous materials such as membranes, foams, aerogels, etc., the extremely high specific surface of nanofibrillated cellulose allows the control of the porosity of the material after drying in nanometres, giving rise to many applications where porosity and a high specific surface area are important parameters, such as filtration membranes, catalyst supports, insulation materials, etc. - charged groups such as carboxyalkyl, e.g. carboxyethyl, which allow the water adsorption properties and porosity properties of the material to be tuned, have for example been grafted onto cellulose fibres according to the invention; For the stabilization of emulsions: nanofibrillated cellulose functionalized with hydrophobic or chelating groups can be used, for example, as a stabilizer of the hydrophobic phase in paints, varnishes, cosmetics, etc., or to disperse functional agents such as opacifiers, for example titanium dioxide, or reinforcing agents, for example clays, in the paper industry - benzophenone functional groups allowing the polymerization of the polymer and / or alkyl chains modifying the amphiphilic properties of the nanofibrillated cellulose have been grafted, for example, to the cellulose fibers according to the invention; In the field of nanocomposites, the exceptional mechanical properties of nanofibrillated cellulose can be exploited and functionalized to give it compatibility with other components such as polystyrene, polyurethanes, acrylates, etc. - benzophenone functional groups allowing the polymerization of polymers and / or alkyl chains favoring the interaction with composite synthetic polymers have for example been grafted onto the cellulose fibers according to the invention; Textile sector: Nanofibrillated cellulose can be functionalized with dyes, as chemical grafting prevents color fading.

[0109] The features and advantages of the present invention will become more apparent in light of the following examples, which refer to FIGS. 1-10 and are provided for illustrative purposes only and are not intended to limit the invention in any way. [Brief description of the drawings]

[0110] [Figure 1] FIG. 1 shows photographs (top row) and optical microscope images (bottom row) of cellulose fibers in their native form ("Cell", a1 / , b1 / ), after functionalization with benzophenone-derived moieties ("Cell-BP", a2 / , b2 / ), after carboxymethylation ("CMC", a3 / , b3 / ), and after simultaneous functionalization with benzophenone-derived moieties and carboxymethylation according to the present invention ("CMC-BP", a4 / , b4 / ). [Diagram 2] FIG. 2 shows Fourier transform infrared (FT-IR) spectra of (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone ("BP"), cellulose fibers in their native form ("Cell"), cellulose fibers after functionalization with the benzophenone-derived moieties ("Cell-BP"), cellulose fibers after carboxymethylation ("CMC"), and cellulose fibers after simultaneous functionalization with the benzophenone-derived moieties and carboxymethylation in accordance with the present invention ("CMC-BP"). [Diagram 3] FIG. 3 shows, from bottom to top, solid-state 13C CP / MAS NMR spectra of (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone ("BP"), cellulose fiber in its native form ("Cell"), cellulose fiber after functionalization with this benzophenone-derived moiety ("Cell-BP"), cellulose fiber after carboxymethylation ("CMC"), and cellulose fiber after simultaneous functionalization with this benzophenone-derived moiety and carboxymethylation in accordance with the present invention and cellulose fiber after simultaneous functionalization with carboxymethylation ("CMC-BP"). [Figure 4]FIG. 4 shows a graph of the storage modulus G′ (solid symbols) and the loss modulus G″ (hollow symbols) as a function of frequency, measured by dynamic rheology, for dispersions in water of different concentrations (0.5%, 1%, 2%, 4.5% w / w) of bifunctionalized cellulose fibers obtained by simultaneous functionalization with benzophenone moieties and carboxymethylation according to the present invention. [Diagram 5] FIG. 5 shows a graph depicting the loss tangent (tan δ=G′ / G″) as a function of concentration for the dispersion of FIG. [Figure 6] FIG. 6 shows the FT-IR spectra of cellulose fibers obtained by simultaneous functionalization with benzophenone-derived moieties and carboxymethylation according to the invention, either before ("CMC-BP") or after grafting of polymer chains based on methyl methacrylate, dodecyl methacrylate or styrene monomers. [Figure 7] FIG. 7 shows FT-IR spectra at neutral pH or pH 2 of trifunctionalized cellulose fibers obtained by simultaneously functionalizing with ethyl acetate groups, functionalizing with allyl groups, and carboxymethylating according to the present invention ("CMC-EA-Allyl"), as well as FT-IR spectra at neutral pH or pH 2 of those trifunctionalized cellulose fibers after post-modification with 3-mercaptopropionic acid ("CMC-EA-PA"). [Figure 8] FIG. 8 shows photographs (top row) and optical microscope images (bottom row) of cellulose fibers in their native form ("Cell", a1 / , b1 / ), after carboxymethylation ("CMC", a2 / , b2 / ), and after simultaneous functionalization with allyl and decane groups and carboxymethylation according to the present invention ("CMC-Allyl-Dec", a3 / , b3 / ). [Figure 9]FIG. 9 shows the Fourier transform infrared (FT-IR) spectra of cellulose fibers after functionalization with (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone and sodium acrylate in accordance with the present invention ("Cell-BP-Acryl"), and the same bifunctionalized cellulose fibers after polymerization with dodecyl methacrylate ("CMC-BP-Acryl after polymerization of dodecyl methacrylate"). [Figure 10] FIG. 10 shows a photograph of a water droplet (indicated by an arrow) deposited on a film formed by vacuum filtration of cellulose fibers after functionalization with (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone and sodium acrylate, and subsequent polymerization with dodecyl methacrylate, in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0111] material Delignified bleached softwood kraft pulp was used as the starting cellulosic feedstock. Monochloroacetic acid (MCA), (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone, ethyl chloroacetate, allyl bromide, 3-mercaptopropionic acid, 4,4-azobis(4-cyanovaleric acid), methanol, sodium hydroxide, methyl methacrylate, dodecyl methacrylate, styrene and tetrahydrofuran were purchased from Sigma Aldrich and used without further purification. Isopropanol and diethyl ether were supplied by VWR International.

[0112] General protocol for characterization Optical microscope : Cellulose sample (0.1 g L in milliQ water) -1 ) were attached to a glass slide, dried at 40 °C, and observed under a BX51 polarizing microscope (Olympus France SAS) with a 4x objective. Images were taken with a U-CMAD3 camera equipped with a U-TV0.5XC-3 adapter (Olympus).

[0113] Rheology Rheological measurements were performed using a stress-controlled rheometer AR-2000 (TA Instruments). A plate geometry (40 mm) was selected. All measurements were performed at 20 °C. To prevent evaporation during the measurements, the samples were covered with paraffin oil. The elastic modulus (G') and viscous modulus (G'') were measured within the range that represents the linear response region. Measurements were performed in duplicate and the average values ​​were plotted.

[0114] Infrared Analysis (FT-IR, Fourier transform infrared spectroscopy): Infrared spectra were obtained in absorbance mode from potassium bromide (KBr) pellets containing freeze-dried cellulose samples placed directly into a Nicolet® iS50 FTIR spectrometer (Thermo Scientific). All spectra were taken from 400–4000 cm -1 After 200 consecutive scans, -1 The data were collected at a resolution of .

[0115] Conductivity measurement The surface charge of cellulose was measured by conductometric titration with 0.01M NaOH solution using a CDM230 conductivity meter equipped with a TIM900 titration tube and a CDC749 conductivity cell. The degree of substitution (DS) was then calculated using the following formula:

[0116] TIFF2025506191000004.tif15170

[0117] In the formula, n COOH is the number of equivalents of -COOH groups calculated from the conductometric titration, and m fibers is the mass of the cellulose pulp (on a dry basis), 162 corresponds to the molecular weight of anhydroglucose units of the cellulose, and 58 is the net increase in weight of anhydroglucose units of the cellulose for each sodium carboxymethyl group that replaces a hydrogen atom of a hydroxyl group.

[0118] solid state 13 C CP / MAS NMR(Cross-Polarization Magic-Angle-Spinning Nuclear Magnetic Resonance)Cellulose samples (100 mg) were rehydrated with 50 μL of H2O, and excess water was absorbed using an absorbent. Approximately 80–100 mg of each sample was packed into a 4 mm NMR rotor. Cross-polarization / magic angle (CP / MAS) NMR experiments were performed using a dual-resonance H / X CP / MAS 4 mm probe. 13 The measurements were taken on a Bruker Avance III 400 spectrometer operating at a C frequency of 100.62 MHz. The measurements were performed at room temperature and the MAS spin rate was 9 kHz. The parameters of the CP pulse sequence were: proton 90° pulse 3.5 μs, CP contact time 1.75 ms at 67.5 kHz, cycle time 9 s. CP / MAS 13 The acquisition frequency of the C spectrum was typically 5.120 scans. 13 C NMR spectra were referenced to the glycine carbonyl peak at 176.03 ppm. All spectra were processed with Gaussian multiplication parameters of LB=-5 Hz and GB=0.1. NMR spectra were deconvoluted as described in Villares et al., Sci. Rep., 2017, 7, 40262.

[0119] Example A - Bifunctionalization of cellulose fibers by introducing benzophenone-derived moieties and carboxymethyl groups Cellulose fibers were difunctionalized with carboxymethyl groups and benzophenone-derived moieties bearing benzophenone functionality according to the following reaction scheme.

[0120] TIFF2025506191000005.tif146170

[0121] Here, n is an integer from 200 to 5000.

[0122] A.1 / preparation Cellulosic fibers (delignified bleached softwood kraft pulp) (100 mg) were first dispersed in water using a blender. The fibers were filtered using a vacuum filtration system and washed with ethanol. The fibers were then impregnated with monochloroacetic acid (10 mg) dissolved in 0.5 mL of isopropanol for 30 minutes at room temperature. Next, (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone (10 mg) dissolved in diethyl ether (2 mL) was added to the fibers. The solution was impregnated into the fibers for 30 minutes at room temperature. After impregnation, the fibers were added to a solution of sodium hydroxide (16 mg) in isopropanol (1 mL) heated to 60 °C in a two-neck round-bottom flask. 2.5 mL of isopropanol was added to bring the total isopropanol reaction volume to 5 mL. The reaction was carried out at reflux for 60 minutes at 70 °C. The fibers were purified by filtration and subjected to washing steps with isopropanol (3 times) and then water (3 times) until neutral pH.

[0123] Fibrillation was carried out by magnetic stirring in water overnight to obtain cellulose microfibrils.

[0124] For comparison, fibers were impregnated separately with monochloroacetic acid or (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone to introduce only one functional group (carboxymethyl or benzophenone derivative) and treated as above.

[0125] A.2 / Characterization The appearance and microscopic images of native cellulose fibers ("Cell", a1 / , b1 / ), cellulose fibers functionalized with benzophenone derivatives ("Cell-BP", a2 / , b2 / ), carboxymethylated cellulose fibers ("CMC", a3 / , b3 / ) and carboxymethylated cellulose fibers functionalized with benzophenone derivatives ("CMC-BP", a4 / , b4 / ) are shown in Figure 1. It can be seen that the introduction of only the benzophenone derivative moiety ("Cell-BP") did not result in significant modification of the fiber morphology compared to the native fiber ("Cell"). In contrast, the visual appearance and microscopic images of both carboxymethylated samples ("CMC" and "CMC-BP") show a gel-like appearance and fiber collapse. The introduction of negative charges on the cellulose surface by carboxymethyl groups promoted the separation between fibers and subsequent fibrillation.

[0126] FT-IR spectra were obtained for native cellulose fibers ("Cell"), cellulose fibers functionalized with benzophenone derivatives ("Cell-BP"), carboxymethylated cellulose fibers ("CMC"), carboxymethylated cellulose fibers functionalized with benzophenone derivatives ("CMC-BP"), and (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone ("BP"). These spectra are shown in Figure 2. Except for the "BP" spectrum, they all show the characteristic profile of cellulose fibers. -1 A closer look at the region shows that functionalization results in the appearance of new peaks. Carboxymethylation is at 1736 cm, which corresponds to a C=O stretch from the carboxyl group. -1 This is indicated by the appearance of a new band at 1640 cm. This band was clearly detected in both the CMC and CMC-BP samples. -1 A strong band due to ketone C=O was observed at 1600 cm, which is a characteristic band belonging to benzophenone. -1These benzophenone bands were detected in both samples (Cell-BP and CMC-BP) functionalized with benzophenone derivatives. -1 is 1635cm -1 However, the band at 1600 cm is not very clear because it overlaps with the band of the symmetric deformation vibration of the absorbed water molecule. Nevertheless, the band at 1600 cm is observed in the Cell-BP and CMC-BP samples. -1 The presence of the bands in the spectra of CMC-BP clearly indicates the successful grafting of the benzophenone derivative moiety. Thus, the introduction of two functional groups in the CMC-BP sample is indicated by the presence of bands corresponding to the carboxymethyl and benzophenone groups in the CMC-BP spectrum. Furthermore, the intensity of the carboxyl group was comparable in both CMC and CMC-BP samples, indicating that the degree of substitution in the carboxymethylation reaction was not affected by the simultaneous reaction with the benzophenone derivative.

[0127] The carboxymethylated samples CMC and CMC-BP were analyzed by conductometric titration to determine the carboxyl content after carboxymethylation. The total charge of CMC was 0.745 ± 0.019 mmol.g -1 , which corresponds to a degree of substitution (DS) of 0.13 ± 0.01. When the fibers were simultaneously carboxymethylated and functionalized with benzophenone derivatives (CMC-BP), the total charge was 0.709 ± 0.037 mmol.g -1 and the corresponding DS was 0.12 ± 0.01. Therefore, there was no significant decrease in the total charge when both reactions were carried out simultaneously, indicating that both carboxymethyl and benzophenone functional groups were successfully grafted.

[0128] solid state 13C CP / MAS NMR experiments were performed to demonstrate the covalent grafting of carboxymethyl and benzophenone derivative functional groups onto cellulose fibers. The obtained spectra are shown in Figure 3. The spectrum of the unmodified fiber (Cell) shows characteristic resonances of cellulose at 110–55 ppm: C1 at δ 100–108 ppm, C4 at δ 79–90 ppm, C2,3,5 at δ 68–78 ppm and C6 at δ 58–67 ppm. Carboxymethylated cellulose (CMC and CMC-BP) show the same peaks as well as a peak at 174 ppm that is likely to be the carboxymethyl group, indicating that carboxymethylation of the cellulose fibers has occurred sufficiently.

[0129] As mentioned above, the presence of charges from carboxymethyl groups on cellulose fibers affects their mechanical and viscoelastic properties, imparting gel-like behavior. Dynamic rheology was used to evaluate the properties of CMC-BP dispersions in water at various concentrations (0.5%, 1%, 2%, 4.5% w / w) to characterize the gel behavior of these carboxymethylated bifunctionalized cellulose fibers. The results are shown in Figure 4. Over the entire concentration range from 0.5 to 4.5% w / w, G'>G'', characteristic of gel-like behavior, was observed. The values ​​obtained are in agreement with those observed for microfibrillated cellulose, as described in Paakko et al., Biomacromolecules, 2007, 8, 1934-1941.

[0130] The loss tangent (tan δ=G' / G'') was calculated. The results are shown in Figure 5. At all concentrations tested, the loss tangent is less than 1, which characterizes gel behavior, and even less than 0.3, clearly indicating the formation of an entangled network structure.

[0131] A.3 / Polymerization assay Benzophenone is one of the best-known photoinitiators for radical polymerization. Benzophenone abstracts hydrogen from H-donors such as monomers to form two types of radicals: a ketyl radical on the benzophenone moiety and an alkyl radical generated on the H-donor, which initiates the polymerization. Thus, the benzophenone functional group grafted onto the cellulose surface could act as an initiator for grafting polymer chains onto the cellulose surface. Thus, the resulting polymer has one chain end tethered to the benzophenone moiety on the cellulose surface and can adopt various conformations depending on the grafting density.

[0132] Three types of monomers were used: methyl methacrylate, dodecyl methacrylate, or styrene. Polymerization was carried out by UV irradiation. The monomers were impregnated into bifunctionalized fiber CMC-BP (20 mmol per 1 g of cellulose). 365 nm (UV Lightningcure, 4500 mW.cm -2 After irradiation for 30 min at 400 nm, the fibers were washed with tetrahydrofuran to remove excess monomer.

[0133] The growth of hydrophobic, uncharged polymer chains on the cellulose fibers was monitored by FT-IR. The spectra obtained for each monomer are shown in Figure 6, together with the spectrum of the initial bifunctionalized cellulose fiber ("CMC-BP"). Compared to the latter, the spectrum obtained after incubating the fibers with the monomers shows the presence of new bands corresponding to the growth of the polymer. As the samples were not acidified, the carboxylates (COO - ) is 1600cm -1 For polymethacrylate (methyl and dodecyl), it is 1730 cm -1 The new bands at 1450, 1490 and 1585 cm are due to the carbonyl groups from the acrylate. Finally, the polymerization of styrene is accompanied by the new bands at 1450, 1490 and 1585 cm, which correspond to the CH aromatic stretching. -1 This is indicated by the presence of a band.

[0134] In contrast, when, as a comparative example, native cellulose fibers were incubated with the monomers, after washing with THF and water, the FT-IR spectra showed no trace of any monomer, rejecting the hypothesis of monomer adsorption on the fiber surface.

[0135] Example B - Bifunctionalization by introducing allyl and carboxymethyl groups The same protocol as described in Example A was applied, using allyl bromide (11 μL dissolved in 0.5 mL of isopropanol) instead of the benzophenone derivative as reactant for the functionalization of cellulose fibers.

[0136] Bifunctionalized cellulose fibers containing carboxymethyl and allyl groups were obtained.

[0137] They were analyzed by conductometric titration to determine the carboxyl content. The total charge was 0.53 ± 0.04 mmol.g -1 This corresponds to a degree of substitution (DS) of 0.09±0.01.

[0138] Example C - Bifunctionalization to introduce ethyl acetate and carboxymethyl groups The same protocol as described in Example A was applied, using ethyl chloroacetate (11 μL dissolved in 0.5 mL isopropanol) instead of the benzophenone derivative as reactant for the functionalization of cellulose fibers.

[0139] Bifunctionalized cellulose fibers containing carboxymethyl and ethyl acetate groups were obtained.

[0140] They were analyzed by conductometric titration to determine the carboxyl content. The total charge was 0.71 ± 0.09 mmol.g -1 which corresponds to a degree of substitution (DS) of 0.12±0.02.

[0141] Similar results were obtained when ethyl bromoacetate was used instead of ethyl chloroacetate, indicating that the nature of the halide does not significantly affect the grafting.

[0142] Similar results were obtained when octyl chloroacetate was used instead of ethyl chloroacetate, indicating that the length of the alkyl chain had no effect on grafting.

[0143] Example D - Bifunctionalization by introducing decane and carboxymethyl groups The same protocol as described in Example A was applied, using dibromodecane (20 μL dissolved in 0.5 mL of isopropanol) instead of the benzophenone derivative as reactant for the functionalization of cellulose fibers.

[0144] Bifunctionalized cellulose fibers containing carboxymethyl and decane groups were obtained.

[0145] They were analyzed by conductometric titration to determine the carboxyl content. The total charge was 0.53 ± 0.04 mmol.g -1 which corresponds to a degree of substitution (DS) of 0.09±0.01.

[0146] Example E - Trifunctionalization to introduce carboxymethyl, ethyl acetate, and allyl groups Cellulose fibers were trifunctionalized with carboxymethyl, ethyl acetate and allyl groups according to the following reaction scheme.

[0147] TIFF2025506191000006.tif135170

[0148] Here, n is an integer from 200 to 5000.

[0149] Trifunctionalization was carried out following the same procedure as for the bifunctionalization described above in Example A, except that three successive 30 min impregnations of cellulose fibers (100 mg) were carried out with monochloroacetic acid (10 mg) dissolved in 0.5 mL of isopropanol, followed by ethyl chloroacetate (11 μL) dissolved in 0.5 mL of isopropanol, followed by allyl bromide (11 μL) dissolved in 0.5 mL of isopropanol. The impregnated fibers were then added to a sodium hydroxide solution, and the same procedure as for the bifunctionalization was followed.

[0150] The surface charge of the resulting trifunctionalized fiber ("CMC-EA-Allyl") was determined by conductometric titration to be 0.227 ± 0.045 mmol.g -1 It was.

[0151] These trifunctionalized fibers were analyzed by FT-IR at neutral pH and at pH 2 (samples were acidified with a few drops of 0.01 M HCl to obtain a pH equivalent to 2). The spectra obtained are shown in Figure 7. They confirm the presence of carboxymethyl groups in both samples. At neutral pH, the spectrum ("CMC-EA-Allyl") indeed corresponds to COO - Equivalent to 1600cm -1 At pH 2, a shoulder appears at 1733 cm due to protonation to COOH. -1 ("CMC-EA-Allyl pH2"). At neutral pH, the peak shifts to 1733 cm -1 Peaks were also detected at 1195–1210 cm, indicating the presence of ethyl acetate functional groups on the cellulose surface. -1 , 1410~1442cm -1 , 3011~3100cm -1 ) overlaps with the cellulose band, so the allyl groups are not detected in the FT-IR spectrum.

[0152] To detect the presence of allyl groups on the fiber surface, post-modification by thiol-ene coupling with 3-mercaptopropionic acid was performed. For this purpose, 100 mg of trifunctionalized fiber was subjected to solvent exchange into water (100 mL), ethanol (100 mL, 99%), and then methanol (100 mL). The fiber was then dispersed in methanol (10 mL) and stirred for 60 min. Then, 4 μL of methyl 3-mercaptopropionate and 400 μg of 4,4'-azobis-(4-cyanovaleric acid) were added. The reaction was carried out at 60 °C for 18 h. Afterwards, the fiber was washed with methanol.

[0153] The increase in surface charge due to the presence of propionic acid groups on the cellulose surface was quantified by electrical conductivity measurements. The total surface charge measured for the modified cellulose fibers was 0.314 ± 0.068 mmol.g -1 The increase in the total surface charge of the propionic acid derivative ("CMC-EA-PA") compared to the allyl derivative ("CMC-EA-Allyl") clearly indicated the successful coupling of the allyl group with 3-mercaptopropionic acid, thus confirming the allylation of cellulose fibers.

[0154] FT-IR analysis was performed on the post-modified fibers at both neutral pH and pH 2. The spectra of the fibers at neutral pH ("CMC-EA-PA") and pH 2 ("CMC-EA-PA pH2") are shown in Figure 7. The FT-IR spectra show a peak at 1600 cm at neutral pH. -1 COO - Increase in the band and 1733 cm at acidic pH (COOH) -1 The corresponding shift to 1733 cm was obtained for the sample CMC-EA-Allyl pH2, which was not post-modified. -1 The increase in band intensity at can be clearly attributed to the new propionic acid groups grafted to the allyl functional groups of the cellulose fibers.

[0155] To exclude the physical adsorption of 3-mercaptopropionic acid onto cellulose fibers, a control reaction was carried out between native cellulose fibers and 3-mercaptopropionic acid, and the amount of adsorption was extremely low compared to the thiol-ene bond.

[0156] Example F - Nanofibrillation mechanical treatment The bifunctionalized cellulose fibers obtained in Examples A, B, C and D and the trifunctionalized cellulose fibers obtained in Example E can be subjected to a nanofibrillation treatment by homogenization.

[0157] For this purpose, the fibres are passed through a piston pump at high pressure and then pumped through Z-shaped interaction chambers with inner diameters of 400, 200 and 100 µm at a constant flow rate of 350 mL.min - 1, and several passes were made at pressures of 100, 1500 and 2000 bar, respectively.

[0158] This results in multifunctionalized nanofibrillated cellulose for each sample.

[0159] Example G - Trifunctionalization to introduce carboxymethyl, decane and allyl groups The cellulose fibers were trifunctionalized with carboxymethyl, decane and allyl groups.

[0160] Trifunctionalization was carried out following the same procedure as for the difunctionalization described above in Example A, except that the cellulose fibers (100 mg) were impregnated three successive times for 30 min with monochloroacetic acid (10 mg) dissolved in 0.5 mL of isopropanol, followed by 1,10-dibromodecane (0.10 mmol) in 0.5 mL of isopropanol, followed by allyl bromide (0.10 mmol) in 0.5 mL of isopropanol. The impregnated fibers were then added to a sodium hydroxide solution, and the same procedure as for the difunctionalization was followed.

[0161] The introduction of monochloroacetic acid resulted in a 0.218 ± 0.024 mmol g -10.618±0.030mmol.g -1 This was indicated by the amount of surface charge.

[0162] The introduction of the allyl functionality was demonstrated by post-functionalization with 3-mercaptopropionic acid via a thiol-ene coupling reaction carried out as described in Example E. Thus, the surface charge was 0.713 ± 0.065 mmol.g -1 , indicating the introduction of the 3-mercaptopropionic acid group.

[0163] Finally, the cross-linking and plasticity behavior of the fibers indicated the presence of decane after trifunctionalization, as shown in Figure 8. In this figure, the behavior and microscopic images of native cellulose fibers ("Cell", a1 / , b1 / ), carboxymethylated cellulose fibers ("CMC", a2 / , b2 / ) and allyl- and decane-functionalized carboxymethylated cellulose fibers ("CMC-Allyl-Dec", a3 / , b3 / ) are shown, with a gel-like behavior and fiber collapse obtained for both carboxymethylated samples ("CMC" and "CMC-Allyl-Dec"). The introduction of negative charges on the cellulose surface by the carboxymethyl groups promoted the separation between the fibers.

[0164] Example H - Bifunctionalization of cellulose fibers by introducing benzophenone-derived moieties and acrylate groups The cellulose fibers were difunctionalized with acrylate groups and benzophenone-derived moieties bearing benzophenone functional groups.

[0165] H.1 / preparation Cellulosic fibers (delignified bleached softwood kraft pulp) (100 mg) were first dispersed in water using a blender. The fibers were filtered using a vacuum filtration system and washed with ethanol. The fibers were then impregnated with sodium acrylate (0.10 mmol) dissolved in 0.5 mL of isopropanol (1 / 4) at room temperature for 30 minutes. Then, (4-(bromomethyl)phenyl)(4-(prop-2-yn-1-yloxy)phenyl)methanone (0.03 mmol) dissolved in diethyl ether (2 mL) was added to the fibers. The solution was impregnated into the fibers at room temperature for 30 minutes. After impregnation, the fibers were added to a solution of sodium hydroxide (16 mg) in isopropanol (1 mL) heated to 60 °C in a two-neck round bottom flask. 2.5 mL of isopropanol was added to bring the total isopropanol reaction volume to 5 mL. The reaction was carried out at reflux for 60 minutes at 70 °C. The fibers were purified by filtration and subjected to washing steps with isopropanol (3 times) and then water (3 times) until neutral pH.

[0166] Fibrillation was carried out by magnetic stirring in water overnight to obtain cellulose microfibrils.

[0167] H.2 / Characterization The presence of acrylate functional groups was indicated by the surface charge measured by conductometric titration (0.633 ± 0.166 mmol g -1 ).

[0168] The presence of benzophenone functionality was demonstrated by a post-polymerization assay with dodecyl methacrylate, performed as described in Example A. The results are shown in FIG. 9, which shows the FT-IR spectra of the bifunctionalized fiber before polymerization ({Cell-BP-Acryl}) and after polymerization ("Cell-BP-Acryl Poly dodecyl methacrylate"). The 1750 cm peak in the spectrum of the post-polymerized fiber shows a 100% benzophenone functional group. -1 The band is absent in the spectrum of fibers that were not post-polymerized, clearly indicating the presence of polymer.

[0169] Furthermore, films of the resulting post-polymerized bifunctionalized cellulose fibers were prepared by vacuum filtration. The induced removal of water favored the interactions between the cellulose fibers, and the resulting dry films were self-supporting. The presence of the polymer was confirmed by the hydrophobicity of the film, and water droplets deposited on the film did not penetrate the film, as shown in Figure 10 (water droplets indicated by arrows).

[0170] These results demonstrate the possibility of polyfunctionalizing cellulose fibers according to the present invention using sodium acrylate instead of monochloroacetic acid.

Claims

1. A method for preparing multi-functionalized cellulose fibers comprising the steps of: a first functionalization step for grafting a first organic functional group onto said cellulose fibers by reacting said cellulose fibers with a first reactant comprising halogen atoms and / or vinyl and / or phenyl groups and said first functional group, and not comprising a hydroxyl functional group; and a second functionalization step for grafting a second organic functional group onto said cellulose fibers by reacting said cellulose fibers with a second reactant comprising halogen atoms and / or vinyl groups and / or phenyl groups and said second functional group, but not comprising hydroxyl functional groups. including providing wherein the first functionalization step and the second functionalization step are carried out simultaneously in one pot in an alkaline reaction medium, and each of the first reactant and the second reactant is present in the reaction medium in an amount of 0.015 to 10 mmol per gram of cellulose.

2. 2. The method of claim 1, comprising a dispersing step of dispersing the cellulose fibers in water prior to subjecting the cellulose fibers to the first and second functionalization steps, and no intermediate solvent exchange step between the dispersing step and the first and second functionalization steps.

3. 3. The process according to claim 1 or 2, wherein the reaction medium is an alcohol medium.

4. 4. The method according to claim 1, comprising at least one further functionalization step for grafting at least one further organic functional group onto the cellulose fibers by reacting the cellulose fibers with at least one further reactant comprising halogen atoms and / or vinyl groups and / or phenyl groups and said further functional group and not comprising a hydroxyl functional group, said further functionalization step being carried out simultaneously with the first and second functionalization steps in one pot in said alkaline reaction medium, said further reactant being present in said reaction medium in an amount of 0.015 to 10 mmol per g of cellulose.

5. 5. The method according to any one of claims 1 to 4, comprising the steps of impregnating the cellulose fibres with a first impregnation solution comprising the first reactant, a second impregnation solution comprising the second reactant and, where appropriate, at least one further impregnation solution comprising the further reactant, each impregnation step being carried out for a period of between 10 minutes and 1 hour prior to the first and second functionalisation steps and, where appropriate, the further functionalisation step.

6. 6. The method according to any one of claims 1 to 5, wherein the first and second functionalization steps and, where appropriate, the further functionalization step are carried out for a period of 30 to 90 minutes.

7. 7. The method according to any one of claims 1 to 6, wherein the first and second functionalization steps and, where appropriate, the further functionalization step are carried out at a temperature of 60 to 82°C.

8. The first reactant and / or the second reactant and / or, where appropriate, the further reactant, have the general formula (I): Y-R (I) having During the ceremony, Y represents a halogen atom, a vinyl group or a phenyl group, which may be optionally substituted; and R represents a moiety that contains a functional group and does not contain a hydroxyl group; The method according to any one of claims 1 to 7.

9. 9. The method of claim 8, wherein in formula (I), R represents a linear, branched and / or cyclic C2-C20 hydrocarbon group, saturated and / or unsaturated, aromatic or non-aromatic, including functional groups, optionally substituted, optionally interrupted by one or more heteroatoms and / or one or more groups containing at least one heteroatom, and R does not contain a hydroxyl group.

10. The method of any one of claims 1 to 9, wherein the first functional group is a carboxyl-containing group.

11. A method for preparing multifunctionalized nanofibrillated cellulose, comprising the steps of: A method for preparing the multifunctionalized cellulose fibers of claim 10 , Then, a nanofibrillation step by mechanical treatment The method of claim 1, further comprising subjecting the

12. 12. The method for preparing multi-functionalized nanofibrillated cellulose according to claim 11, wherein the nanofibrillation step is carried out by homogenization or high pressure microfluidization.

13. A multifunctionalized nanofibrillated cellulose, characterized in that it is functionalized by the covalent grafting of a carboxyl-containing group and at least two additional organic functional groups.

14. 14. Use of the multifunctionalized nanofibrillated cellulose according to claim 13 for the preparation of a composite material.

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