Functionalization and reinforcement in the dry state and in the wet state of a cellulosic material by an oxidized polysaccharide

Description

[0001] The present invention relates to compounds, particularly those based on polysaccharides, that adsorb onto a cellulosic material. The present invention relates in particular to the application of such compounds (polysaccharides) as a reinforcing agent for cellulosic materials, in both wet and dry states. State of the art

[0002] One of the technical challenges is developing easy-to-use, and preferably inexpensive, reinforcing agents, particularly for industrial applications. Cellulosic materials, such as paper fibers or textile fibers, are widely used in numerous applications (paper and cardboard for packaging, graphic printing, specialty papers, reinforcement for composites, etc.). In many applications, the water sensitivity of these materials is a major obstacle to their use, although their biorenewable nature makes them attractive from a sustainable development perspective. Many additives have already been developed to give treated cellulosic materials Wet Strength (WSE).

[0003] The solutions recommended in the state of the art generally require specific and more or less complex processes, mostly using compounds derived from petrochemicals and whose toxicity is recognized (glyoxal, formaldehyde, epichlorohydrin, etc.).

[0004] Furthermore, in general, the additives or reinforcing agents used exhibit either strength-enhancing properties for cellulosic materials in their dry or wet state. However, it is not easy to identify agents that enhance the strength of cellulosic materials in both their wet and dry states. The prior art generally uses different additives to fulfill these two technical functions. Therefore, there is an interest in developing new reinforcing agents to overcome this technical problem.

[0005] Furthermore, existing petrochemical products are generally toxic or suspected of being so. To circumvent this difficulty, dosages are reduced and / or restrictions are placed on the commercial use of these products.

[0006] In general, for applications where reinforcing agents must be effective in a wet state, currently available solutions are unsatisfactory, particularly because reinforcement requires the use of toxic products and cumbersome processes, or materials with complex structures and / or containing aluminum or plastic foils. Often, manufacturers will prefer a plastic material, which is unfortunate.

[0007] We know from US patent 3,205,125 a process for forming paper, comprising a step of adding to the paper pulp before the formation of sheets 0.1 to 5% of an oxidized polygalactomannan gum, the oxidizing agent being periodic acid or its alkali metal salts and being used in an amount of 0.01 to 0.4 mole per anhydrous hexose unit.

[0008] US patent 5,554,745 also discloses galactose-containing polysaccharide derivatives containing cationic aldehydes obtained by oxidation with the enzyme galactose oxidase. The products oxidized by the enzyme have an aldehyde group at a specific position on the polysaccharide, namely the C6 position of the galactose unit. These cationic derivatives are used as paper strength additives. Objectives of the invention

[0009] The inventors have discovered that a compound according to the present invention makes it possible to solve at least one, and preferably all, of the technical problems mentioned in the present invention.

[0010] The present invention aims in particular to solve the technical problem of providing a new compound (polysaccharide) that can serve as a reinforcing agent for a cellulosic material, in particular for reinforcing the resistance of the cellulosic material in the dry and / or wet state.

[0011] The present invention aims to solve the technical problem of providing a cellulosic material that is resistant in particular in the wet state, and preferably in both the dry and wet states.

[0012] The present invention aims to solve the technical problem of providing a process enabling the controlled preparation of such a compound.

[0013] The present invention aims in particular to solve the technical problem of providing such a compound, its preparation process in environmentally friendly ways, and in particular to use compounds of natural origin and to limit the use of toxic materials.

[0014] The present invention aims to solve technical problems in an industrial, reliable, and preferably inexpensive manner without modification of the existing process. Description of the invention

[0015] In particular, the present invention relates to the preparation of polysaccharide compounds, their complexation with a cellulosic material and their applications, in particular as resistance strengthening agents for cellulosic materials, in dry and / or wet state.

[0016] The present invention relates to a compound comprising an association of at least one polysaccharide adsorbed on a cellulosic material, said polysaccharide being an oxidized xyloglucan comprising at least two different monosaccharide units, forming first and second monosaccharide units, said second monosaccharide units being branched on a chain comprising at least said first monosaccharide units, at least some of the second monosaccharide units being non-cyclic and bearing aldehyde functions, said aldehyde functions forming hemiacetal functions with hydroxy functions of the cellulosic material.

[0017] According to one embodiment, non-cyclic branched monosaccharides bearing aldehyde functions are oxidized xyloses.

[0018] According to one embodiment, the adsorbed polysaccharide is selected from the group consisting of a tamarind seed xyloglucan (TXG), a pea xyloglucan, and any of their mixtures.

[0019] The inventors discovered that this hemicellulose, which adsorbs onto cellulosic materials, and in particular onto cellulose, such as xyloglucan extracted from tamarind (especially the seeds), once oxidized, still retains the property of adsorbing onto the cellulosic material and, after drying, forms hemiacetal bonds with the cellulosic material, giving the material interesting properties. This water-soluble molecule has a branched structure described figure 1, with a skeleton of D-glucopyranose units linked together by Pl--+4 bonds and branched. On average, 3 out of 4 units are substituted at position O6 by D-xylose chains. These can also be substituted at position O2 and form side chains with galactose, fucose and / or arabinose ( figure 1 ).

[0020] The nature and distribution of these side chains vary according to plant tissues and species. Xyloglucan from tamarind seeds, used according to the invention, generally has a galactosylation rate of approximately 85% (generally from 80 to 90%).

[0021] The process for preparing a compound according to the invention includes an oxidation of the polysaccharide, advantageously by periodate or any other reagent enabling the cleavage of the C2-C3 bond and producing up to 2 aldehydes per sugar.

[0022] The amount of aldehyde formed varies advantageously depending on the kinetics and / or the amount of oxidant introduced. This results in the percentage of oxidation, the quantity that characterizes the extent of the reaction, the measurement of which is detailed in the invention.

[0023] Preferably, the polysaccharide is oxidized by an oxidizing agent. Preferably, the polysaccharide is oxidized by a periodate, and preferably sodium metaperiodate.

[0024] In the present invention, Xg means xyloglucan and XgOx means oxidized xyloglucan.

[0025] The polysaccharide is preferably solubilized before oxidation, but can also be oxidized in the form of a "slurry," which is a highly concentrated paste-like mixture of polymer and water. Solubilization preferably takes place in an aqueous phase, and even more preferably with water as the sole solvent.

[0026] The oxidation protocol is preferably as follows

[0027] Xyloglucan is solubilized in deionized water using deflocculating mechanical stirring. Concentrations are set by weighing between 0.1 and 2% depending on the test. Metaperiodate is then added in concentrated solution, and the reaction is carried out overnight. The reaction mixture is then purified by dialysis.

[0028] The reaction can, for example, be advantageously characterized by its percentage of oxidation. According to the present invention, an oxime formation titration is used: The amount of aldehyde formed is measured by oxime titration. The amount of Xg oxidized, equivalent to a dry mass of 0.1g, is weighed and placed in a 100 mL beaker. 25 mL of a 0.25 M NH₂OH,HCl solution, the pH of which has been previously measured, are added. The reaction is carried out for 2 hours with stirring at room temperature. A white precipitate appears (oxime formation). The solution is then titrated with 0.02 M sodium hydroxide, the equivalence point corresponding to the return to the initial pH of the NH₂OH,HCl solution.

[0029] Using the volume of sodium hydroxide, the percentage of oxidation is calculated according to equation 1: %Ox = V NaOH × C NaOH × M XG m Xgoxs / 18

[0030] With M Xg = 1350g / mol (molar mass of one unit of Xg), V NaOH = equivalent volume of sodium hydroxide, C NaOH = exact concentration of the sodium hydroxide solution and m Xgoxs = dry mass of XgOx introduced.

[0031] According to one embodiment, a polysaccharide is preferred having a percentage of oxidation greater than 0% and less than or equal to 50%, and preferably less than or equal to 40%, and preferably even less than or equal to 30%, expressed as the number of oxidized saccharide units out of the total number of saccharidic units.

[0032] The following notation will be adopted in the remainder of this document: abbreviation of the oxidized polysaccharide of the type "Ox(%Oxidation)", such that a xyloglucan oxidized to 20% will be noted XgOx20, or a guar gum oxidized to 30% will be noted GOx30, or a carob gum ("locust beam gum") oxidized to 63% will be noted LOx63.

[0033] Preferably the percentage of oxidation is greater than 0 and less than 40%, and preferably less than 20% (the percentages are expressed as the quantity of oxidized saccharide units out of the total quantity of saccharide units). In the case of Tamarind xyloglucan, the percentage of oxidation corresponds, for example, to 0 to 0.5 mol of aldehyde / 100g of polysaccharide.

[0034] Advantageously, the percentage of oxidation influences the adsorption capacity on the one hand, and the crosslinking density on the other.

[0035] According to one variant, the polysaccharide is covalently linked to the cellulosic material by hemiacetal functions between aldehyde functions of branched monosaccharides and hydroxy functions of the cellulosic material.

[0036] According to one variant, the polysaccharide is further covalently linked by one or more reactive molecules reacting with aldehyde functions of the polysaccharide, said reactive molecules being for example selected from the group comprising amines, polyamines, hydroxylamines, imines, hydrazide and any of their combinations.

[0037] Advantageously, the polysaccharide is further covalently linked by at least two reactive molecules reacting with aldehyde functions of the polysaccharide, said reactive molecules being for example selected from the group comprising amines, polyamines, hydroxylamines, imines, hydrazide and any combination thereof.

[0038] The invention also relates to a method for covalently linking a cellulosic material to a polysaccharide, said method comprising adsorbing the polysaccharide onto a cellulosic material to form a compound according to the present invention and reacting aldehyde functions of the polysaccharide with hydroxy functions of the cellulosic material to form hemiacetal functions.

[0039] According to one variant, the oxidation step is carried out in an aqueous medium in solution or in slurry in the form of a concentrated paste.

[0040] The method includes, prior to the adsorption of the polysaccharide onto the cellulosic material, an oxidation step of a precursor polysaccharide of the polysaccharide to be adsorbed onto the cellulosic material. The adsorbable polysaccharide is an oxidized xyloglucan comprising non-cyclic branched monosaccharides bearing aldehyde groups.

[0041] The oxidation step can be controlled to oxidize only the branches of the polysaccharide.

[0042] Advantageously, the method according to the invention is implemented under conditions preserving the adsorption properties of the cellulosic material and the oxidized polysaccharide.

[0043] Advantageously, the method according to the invention is implemented under conditions that best preserve the molar mass of the polysaccharide.

[0044] According to one variant, the mass molar mass of the polysaccharide ranges from 20 to 700 kDa (Mw).

[0045] According to one variant, the mass molar mass of the polysaccharide ranges from 70 to 700 kDa (Mw).

[0046] According to one variant, the mass molar mass of the polysaccharide ranges from 100 to 500 kDa (Mw) and for example from 100 to 400 kDa (Mw).

[0047] According to one embodiment, adsorption is carried out with the cellulosic material in an aqueous medium.

[0048] The invention also relates to a method in which a compound according to the invention is shaped and dried into papers, fibers, non-woven materials, etc. (Drying allows for the stabilization of the crosslinking by the hemiacetal bonds.)

[0049] Polysaccharide adsorption is a key property for the application of reinforcing additives. The present invention supports the link between oxidation and adsorption on a cellulosic material, and in particular cellulose. If oxidation is too extensive, adsorption ceases. Advantageously, the aim is to preserve the glycosidic sequence of the polysaccharide's backbone during oxidation so that it interacts sufficiently with the cellulosic material to be adsorbed. This adsorption then advantageously allows the polysaccharide to be fixed via hemiacetal bonds between the cellulosic material and the aldehydes produced by oxidation during the drying of the cellulosic material.

[0050] According to one embodiment, the polysaccharide is covalently linked to the cellulosic substrate and is made to react with one or more reactive molecules reacting with aldehyde functions of the polysaccharide, said reactive molecules being for example selected from the group comprising amines, polyamines, hydroxylamines, imines, hydrazide and any of their combinations.

[0051] Among cellulosic materials, we can mention in particular cellulose fibers, and especially textile fibers such as flax, hemp, jute, kenaf fibers, paper pulp, in particular kraft pulp, sulfite pulp or cotton linters, nanocelluloses for example cellulose nanofibrils (or NFC) or cellulose nanocrystals (or CNC). According to one variant, the oxidized polysaccharide according to the invention is added at a mass concentration of 0.001% to 1%, preferably 0.001% to 0.5%, and even more preferably 0.001% to 0.2%, in the fibrous suspension to be treated, that is to say typically to be reinforced.

[0052] According to one variant, the oxidized polysaccharide is added by spraying or deposition onto the already formed product before drying, or onto the already dried product with an additional drying step.

[0053] According to another variation, a reactive product possessing a chemical function capable of reacting with aldehydes can be added to increase strength in the wet or dry state, or to impart functionalities to the cellulosic material such as antiseptic or antioxidant properties, or specific coloring. The reactive product can be chosen from the group of amines, polyamines, hydroxylamines, imines, hydrazides, or any other compound capable of reacting with the remaining aldehyde functional groups.

[0054] Advantageously, a compound (polysaccharide) according to the present invention can be added at different stages of paper pulp preparation. Schematically, as illustrated in the figure 8, a papermaking process may include in one of the steps 10 of refining or beating paper pulp using refiners or beaters, 20 of mixing the refined pulp in the case where there is more than one feed of paper pulp, 30 of adding chemicals to obtain the desired paper or board product, 40 of transferring the prepared paper pulp or board to the papermaking machine, 50 of manufacturing paper from the prepared paper pulp 'wet end'.

[0055] For example, a compound (polysaccharide) according to the present invention can be added to one or more of these steps, and in particular to steps 10, 20, 30 or 40. Or to the pulp prepared before the actual preparation of the paper pulp, generally called the "wet end".

[0056] Thus, according to one variant, a compound (polysaccharide) according to the present invention is added during the preparation of the dough (“stock preparation” in English).

[0057] According to another variant, a compound (polysaccharide) according to the present invention is added during the wet end.

[0058] Advantageously, existing processes do not need to be modified for a compound according to the present invention to be added. This is referred to as isoprocess addition.

[0059] The invention also relates to the use of a polysaccharide as a reinforcing additive for a cellulosic material comprising hydroxy functions, said polysaccharide being an oxidized xyloglucan comprising non-cyclic branched monosaccharides bearing aldehyde functions, in which aldehyde functions possibly form hemiacetal functions with hydroxy functions of the cellulosic material, said polysaccharide being capable of adsorbing onto the cellulosic material, and preferably to form a compound defined according to the present invention.

[0060] According to one variant, the polysaccharide is used as an additive to enhance the wet strength of a cellulosic material comprising hydroxy functions.

[0061] According to one variant, the polysaccharide is used as a strength-enhancing additive in the dry state, and preferably in the dry and wet state, of a cellulosic material comprising hydroxy functions.

[0062] The invention also relates to the use of one or more reactive molecules reacting with aldehyde functions of the compound as defined according to the invention, to provide a new functionality to the compound, for example antiseptic, coloring, and / or increase the mechanical properties of the material thus formed, said reactive molecules being for example selected from the group comprising amines, polyamines, hydroxylamines, imines, hydrazide and any of their combinations.

[0063] In the figures: There figure 1represents a branched structure of a compound (polysaccharide) of the invention with a backbone of D-glucopyranose units linked together by β1→4 bonds and branched; The figure 2 represents the mass yield of the reaction according to example 2 for different oxidation percentages on 1.42 g of xyloglucan in a 0.8% solution; The figure 3 represents the evolution of the adsorption of oxidized xyloglucan as a function of its degree of oxidation for mass proportions of xyloglucan and cellulose in 0.2% solution of 1 to 1 (•) and 1 to 3 (Δ); The figure 4 represents the influence of the proportion of xyloglucan (white), XgOx11 (grey) and XgOx23 (hatched) on the ultimate stress of NFC films; The figure 5 represents the influence of the proportion of xyloglucan (white), XgOx11 (grey) and XgOx23 (hatched) on the ultimate stress of wet NFC films; The figure 6shows the influence of the mass proportion of xyloglucan (white) and XgOx12 (grey) and XgOx23 (hatched) on the ultimate stress of NFC films post-treated in a 0.3% wt adipic hydrazide solution. figure 7 represents the ultimate constraint of NFC and xyloglucan films (white, left column), XgOx12 (hatched, second column from the left) and XgOx23 without (grey, third column from the left) and with post-treatment (hatched, right column) by adipic dihydrazide, for different constitutions; The figure 8 schematically represents a paper or cardboard manufacturing process.

[0064] Other purposes, features and advantages of the invention will become clear to those skilled in the art upon reading the explanatory description, which refers to examples given only by way of illustration and which shall in no way limit the scope of the invention.

[0065] The examples form an integral part of the present invention and any feature which appears new compared with any prior art from the description taken as a whole, including the examples, forms an integral part of the invention in its function and in its generality.

[0066] Thus, each example has a general scope.

[0067] On the other hand, in the examples, all percentages are given by weight unless otherwise stated, and temperature is expressed in degrees Celsius unless otherwise stated, and pressure is atmospheric pressure unless otherwise stated.

[0068] The xyloglucan oxidation percentages shown in the examples are evaluated by oxime formation assay. EXAMPLES Example 1: Preparing an XgOx 1.1. Oxidation of Xyloglucan.

[0069] Material : Raw Materials: - 2 beakers of 1L. - 10g of Tamarind Xyloglucan. - Balance. - Sufficient quantity of NaO4. - 2 magnetic stirrers. - Approximately 650mL of distilled water. - Magnetic plate. Operating Procedure:

[0070] Weigh approximately 10g of tamarind xyloglucan into a 1L beaker. In a separate 1L beaker, weigh the required amount of sodium periodate and dissolve it with stirring in approximately 650mL of distilled water. Pour the dissolved periodate solution into the beaker containing the xyloglucan. Stir the beaker (approximately 700 rpm) until the mixture becomes no longer too viscous and the stirrer stops rotating. Cover the beaker with Parafilm and let it stand overnight. 1.2. Purification of the solution Principle:

[0071] To purify the solution, a dialysis process is performed, allowing salts and small molecules to pass through a membrane and into the water basin. The water must therefore be changed frequently because, once equilibrium is reached between the ions in the solution and the pure water, further purification is no longer possible.

[0072] Dialysis is complete when the water conductivity is less than 10µS / cm.

[0073] This yields a purified oxidized xyloglucan. Example 2: Influence of oxidation on oxidized xyloglucan Yields

[0074] The mass yield of the reaction was studied for different oxidation percentages on 1.42 g of xyloglucan in a 0.8% solution. The final mass was calculated after dialysis by gravimetry; the results are presented. figure 2The reaction has a good yield of approximately 95% for moderate oxidation levels up to about 30%. The low material loss in this case is a result of the various handling steps. However, for higher oxidation levels, the yield decreases, dropping to 82% for an oxidation level of 49%, and then to 77.5% for an oxidation level of 62%. The material loss here is explained by the dialysis purification process. The cutoff point of the equipment used is 14,000 g / mol. Thus, after chain breaks, a significant amount of material with a lower molar mass can be removed. These phenomena will be studied in the following sections. Molecular masses

[0075] The oxidation of polysaccharides is systematically accompanied by a decrease in molar mass. Oxidation was carried out on 1 g of xyloglucan in a 0.4% solution. Different oxidation percentages were achieved, and the molar masses of the resulting products were checked. The measured results are shown in Table 1. Table 1: Evolution of the molar mass in mass (Mw), in number (Mn) and of the polydispersity index (Ip) of Xg as a function of the oxidation state Mw (kDa) Mn (kDa) IP Xyloglucan 863 ± 5,4 652 ± 15,9 1,32 ± 0,03 XgOx9 376 ± 1,9 283 ± 4,9 1,33 ± 0,02 XgOx21 130 ± 1,8 99 ± 1,4 1,31 ± 0,02 XgOx30 155 ± 2,5 108 ± 1,3 1,44 ±0,007 XgOx46 133 ± 4,8 103 ± 4,4 1,29 ± 0,01 XgOx59 28 ± 1,1 23 ± 1,0 1,25 ± 0,01

[0076] Oxidation can have a significant impact on the molar mass of the polysaccharide.

[0077] For example, under the preparation conditions described in Example 1, at an oxidation state of 10%, the molar mass is significantly altered, being halved. It decreases by a further factor of 2 at 20% oxidation, then appears to stabilize up to approximately 50%. However, it drops to 23 kDa at 60% oxidation, which is just twice the cutoff value of the membranes used during the purifications, which is 14 kDa. This final drop occurs at an oxidation state that necessarily involves the oxidation of the glucose molecules that form the backbone of the molecule, and its degradation explains such a significant decrease in molar mass. Influence on adsorption

[0078] The influence of the oxidation reaction on the molar masses and structure of the polymer can modify its physicochemical properties. Therefore, the adsorption properties of XgOx were controlled: the XgOx solution and the NFC suspension were stirred for 1 hour. The equivalent dry masses introduced were 0.3 g of XgOx and either 0.3 g or 0.9 g of NFC, depending on the study. Different concentrations were investigated. After centrifugation at 11,200 rpm at 10°C for 30 minutes, the supernatant was removed, and the pellet was redispersed in deionized water. After a second centrifugation under the same conditions, the pellet was placed in an oven and weighed. The difference between the mass obtained and the initial dry mass of NFC gives the amount of XgOx adsorbed.

[0079] There figure 3This diagram shows the evolution of the amount of Xg adsorbed at a concentration of 0.2 wt% in solution, as a function of its oxidation percentage, for two different proportions of cellulose nanofibrils (circle: 1:1; triangle: 1:3). The adsorption capacity of Xg remains unaffected until the oxidation level approaches 30%. A significant decrease in adsorption properties is then observed, becoming virtually zero beyond 50%. At this oxidation level, the glycosidic backbone of the chain responsible for Xg adsorption begins to oxidize, thus altering its behavior. The presence of aldehydes and the breaking of a carbon-carbon bond, in particular, increase the chain's flexibility and modify its ability to form hydrophobic interactions and hydrogen bonds.Therefore, XgOx should preferably be used between oxidation percentages of approximately 0 and 25%, in order to ensure that the product's adsorption capacity is maintained. Example 3 Use as a strengthening additive

[0080] Oxidized xyloglucans have been used as paper strengthening additives, both in dry and wet states.

[0081] Different formulations were tested, with different ODs, different concentrations, different sources of paper pulp and different molar masses. 1. Variations in cellulose sources i. NFC films

[0082] NFC and XgOx films were produced by casting: a 2.23% wt. NFC suspension was added to achieve the desired quantity, followed by xyloglucan solution, and the total volume was adjusted to 50 mL with deionized water. The final dry film masses were 0.5 g, with Xg / XgOx proportions of 0, 1, 5, 10, and 25% wt. The mixture was stirred for 2 hours at room temperature and then poured into a Petri dish. Casting was carried out under a fume hood at room temperature until completely dry. The films were then tensile tested.

[0083] There figure 4 This shows the evolution of the properties of dry films as a function of the proportion of XgOx and for different percentages of oxidation.

[0084] Xyloglucan and oxidized xyloglucan strengthen NFC films in the dry state in the same way with a gain of about 50% in breaking strength, the proportions and percentage of oxidation not showing significant influence.

[0085] The same experiment was then repeated on wet films; after immersion for 1 hour in water, the results are shown. figure 5 .

[0086] The strengthening effect is marked for both different oxidation percentages, while it is zero for unoxidized Xg. ii. Flax fiber

[0087] The role of the additive was also tested on flax fibers. Technical bundles were soaked in a solution of approximately 20% oxidized XgOx, concentrated at 1% by mass (XgOx22 meaning oxidized xyloglucan at a percentage of 22%. This reference is used in the other examples by analogy). After rinsing and drying, these fibers were tested in tensile strength, first in the dry state (Table 2). Table 2: Mechanical properties of treated technical fibers, standard deviations are indicated in parentheses. Breaking stresses (MPa) Young's modulus (GPa) σ / E Untreated fibers 813 (270) 58 (13) 1,38 (0,21) XgOx22 755 (157) 55 (5,6) 1,37 (0,24)

[0088] No significant difference in properties was observed between treated and untreated fibers. However, Table 3 presents the results obtained on wet fibers. Table 3: Mechanical properties of wet technical fibers, standard deviations are indicated in parentheses. Maximum stress (MPa) Young's modulus (GPa) Maximum deformation (%) Untreated fibers 159 (81) 27 (8) 0,60 (0,33) XgOx22 375 (185) 23 (9) 1,28 (0,42)

[0089] We observe a significant increase in the stress at which the fibers break, despite the large standard deviations. iii. Paper pulp

[0090] Paper samples were produced using a mold-type pulping process, using different pulps: Kraft pulp, sulfite pulp, and cotton linters. Suspensions containing 2 g / L of cellulose and 0.01% XGOX20 (XgOx20) were prepared, then filtered and dried on a mold to obtain a paper weighing approximately 60 g / m². The samples were tested for tensile strength before and after 48 hours of immersion in water. The results are detailed in Table 4. Table 4: Effect of the XGOX20 additive on papers made from different types of pulp. Dry (MPa) Wet (MPa) Ratio Ref• Wet / Dry Kraft Ref 22 0,05 10% XGOX20 40 2,5 Sulphite Ref 6,15 0,15 20% XGOX20 10,13 1,25 Cotton Ref 4,7 0,12 30% XGOX20 10,1 1,25

[0091] Significant reinforcement is observed with XGOX20 in its dry state, amounting to approximately 100% of the initial stress. Reinforcement is also noted in its wet state, ranging from 10% to 30% depending on the paste composition, under these conditions. 2. Effect of concentrations

[0092] XGOX20 is introduced directly into the paper pulp before shaping. The XGOX20 then binds to the fibers by adsorption. Different concentrations of the additive in the pulp were tested, and the properties of the papers produced as follows are detailed in Table 5: One liter of 2g / L fibrous suspension and one liter of water are added to a Büchner funnel containing three filter papers stacked on a nylon buttering cloth with a porosity of 215 µm and a diameter of 18.5 cm. Filtration is carried out under vacuum using a water aspirator, and the resulting paper is then dried at Tamb (25°C) for 24 hours and then in an oven at 60°C overnight. Reference solutions: 100% Kraft pulp in tap water; 0.001 XGOX20: XgOx20 in a 0.001% solution in Kraft pulp suspension; 0.01 XGOX20: XgOx20 in a 0.01% solution in Kraft pulp suspension; 0.5 XGOX20: XgOx20 in a 0.5% solution in Kraft pulp suspension. Table 5: Evolution of the effect of the XGOX20 additive as a function of Mass concentration in paper pulp (Kraft). Standard deviations are shown in parentheses. on 0% 0,001 % 0,01 % 0,5 % XGOX20 XGOX20 XGOX20 XGOX20 Ultimate stress (MPa) dry 6,53 (1,2) 12,76 (0,6) 14,68 (2,5) 18,80 (2,78) humid 0,00 0,98 (0,1) 1,25 (0,2) 2,28 (0,3)

[0093] We observe very clear gains in tensile strength in both dry and wet conditions, even at a concentration of just 0.001% by mass of XGOX20 in the initial fibrous suspension (2 g / l). However, the effect appears to increase with concentration. 3. Effect of the percentage of oxidation (DO)

[0094] Xyloglucan has been used as an additive for different percentages of oxidation.

[0095] One liter of a 2 g / L fibrous suspension containing 0.1% by mass of XgOx, along with one liter of water, is added to a Büchner funnel containing three filter papers stacked on a nylon sifter with a porosity of 215 µm and a diameter of 18.5 cm. Filtration is carried out under vacuum using a water aspirator, and the resulting paper is then dried in a Tamb oven for 24 hours and then in an oven at 60°C overnight.

[0096] The percentage of oxidation will influence the adsorption capacity on the one hand, and the crosslinking density on the other. Table 6: Influence of the percentage of xyloglucan oxidation on the mechanical properties of the treated papers. Standard deviations are indicated in parentheses. Ref %Ox = 1% %Ox = 12% %Ox = 20% %Ox = 35% %Ox = 47% Ultimate stress (MPa) dry 6,53 (1,2) 13,06 (1,9) 13,9 (2,9) 13,8 (1,6) 8,3 (1,8) 11,04 (2,7) humid 0 0,012 (0,09) 0,9 (0,09) 1,48 (0,19) 0,36 (0,13) 0,54 (0,09)

[0097] It is noted that at very low oxidation percentages (1%), the product adsorbs and reinforces the paper in its dry state through the hydrogen bonding network formed by the presence of xyloglucan. However, in its wet state, no reinforcement is observed due to the disappearance of hydrogen bonds and the absence of hemiacetal covalent bonds. At medium oxidation percentages (10 < oxidation percentage < 25%), the balance between product adsorption and crosslinking density is optimal. Above 25%, the glycosidic skeleton is oxidized, and the adsorption capacity decreases. This results in a reduction of mechanical properties in both the dry and wet states. A certain percentage of reinforcement is still observed, which can be explained by the adsorption of a fraction of the chains that retain a structure compatible with adsorption, and by the deposition of the product within the paper mass during the filtration manufacturing process.In this case, the high proportion of aldehyde functions present on the chains allows for significant cross-linking, the effects of which are translated mechanically. 4. Conclusion

[0098] The synthesis of the product was controlled, particularly in controlling the percentage of oxidation.

[0099] The physico-chemical characterization of the adsorption shows the formation of the XgOx-cellulose complex.

[0100] Various applications have demonstrated the product's effectiveness on diverse cellulosic substrates. Example 4: Over-crosslinking i. Mechanical Properties of NFC Films

[0101] NFC films containing different proportions of XgOx undergo post-treatment in an aqueous solution of adipic dihydrazide. After drying, the films are tested in tensile strength. The results presented on the figure 6shows the influence of the mass proportion of xyloglucan, XgO12 and XgO23 on the ultimate stress of post-treated NFC films.

[0102] The post-treated films were tested after immersion in water. The breaking strengths of the wet post-treated films were compared. figure 7 with those of NFC-XgOx films.

[0103] In a humid environment, XgOx helps maintain film cohesion through the formation of hemiacetals. The addition of dihydrazide further enhances the mechanical properties, especially with higher DO and XgOx proportions. For example, at 25% XgOx23, the film exhibits an average stress of 0.4 MPa, increasing to 17 MPa after post-processing, which is 40% of the value of a dry NFC film. ii. Mechanical Properties of Papers

[0104] The effect of this over-crosslinking is then tested on paper. Chitosan, a bio-based amino polymer, was used to obtain a 100% bio-based additive system. - Unpressed papers

[0105] A first phase of testing is carried out on papers prepared as follows: 1 L of a 2% wt. Kraft fiber suspension is prepared, with the XgOx 20 concentrations specified in the table below. Just before filtration, the volume is increased to 2 L under vigorous stirring, and then the suspension is filtered under vacuum. Once the water has been extracted, the vacuum is maintained, and a 0.01% wt. Chitosan solution is sprayed onto the cake. The resulting papers are then dried at room temperature.

[0106] The mechanical properties shown in Table 7 are obtained. Table 7: Breaking stresses of additive-treated papers in the dry and wet states (standard deviations on (samples indicated in parentheses) treated by chitosan impregnation 5 dry (MPa) wet (MPa) Ref 7,1 (0,82) 0,1 (0,06) 0.001% XgOx20 12,8 (0,6) 1 (0,1) 0.01% XgOx20 14,7 (2,5) 1,25 (0,22) 0.5% XgOx20 18,8 (2,82) 2,28 (0,33) 0.001% XgOx20 + Chitosan 19,8 (2,5) 2,3 (0,51) 0.01% XgOx20 + Chitosan 16,2 (3,48) 3 (0,49) 0.5% XgOx20 + Chitosan 19,7 (3,7) 4 (0,35)

[0107] Similarly, papers treated with XgOx35 were further cross-linked after drying. Following the same protocol, the papers were dried after filtration, then soaked in a 0.01% (w / m) chitosan solution before being dried again. The mechanical properties are described in Table 8. Table 8: Breaking stresses of additive-treated papers in the dry and wet states (standard deviations on (samples indicated in parentheses) post-treated with chitosan. 5 σ(MPa) sec σ(MPa) wet ref 6,9 (1,2) 0,1 (0,02) 0.1% XgOx20 12 (1,9) 1,9 (0,14) 0.1% XgOx20 + Chitosan 10,3 (2,25) 2,7 (0,62) 0.01% XgOx20 13,1 (0,18) 1,6 (0,22) 0.01% XgOx20 + Chitosan 11,6 (1,33) 2,9 (0,33) - Papers produced on Franck Formettes

[0108] Additive-treated papers were produced on Franck molds, starting with 1 L of a 2 g / L fibrous suspension containing 0.01% XgOx20 by mass. After filtration, a 0.01% chitosan solution was sprayed onto the filter cakes before vacuum drying at 90°C for 7 minutes. The results are described in Table 9. Table 9: Breaking stresses of additive-treated papers in the dry and wet states (standard deviations on (samples indicated in parentheses) treated by chitosan spraying. 5 Classic Paper XgOx 20 XgOx20 + Chitosan dry 20,1 (0,6) 38,6 (1,9) 37,2 (4,0) humid 0,09 (0,06) 4,0 (0,07) 6,73 (0,29)

[0109] Overcrosslinking with chitosan systematically allows, regardless of the initial XgOx level or the treatment process, a very significant increase in wet-state properties. Example 5: Use of another oxidized polysaccharide Summary:

[0110] 10 g of polymer are dissolved in 1 L of water with vigorous stirring. Periodate is added, and the reaction is carried out for 12 hours at room temperature, protected from light. This yields a 1% (w / w) oxidized polysaccharide solution. Table 10 describes the stoichiometric conditions. Table 10 Stoichiometry (NaO4 / Polym) Designation n Mass of polysaccharide added (9) Mass of periodate added (9) carob gum (locust bean gum) 0,10 LOx10 10,00 1,32 0,19 LOx20 10,43 2,64 guar gum 0,10 GOx10 9,96 1,32 0,20 GOx20 10,12 2,64

[0111] The cellulose was purified to avoid side effects from residual periodate and to allow for analysis of the resulting products. Dialysis was therefore performed until a conductivity equal to that of deionized water from the laboratory was achieved.

[0112] After dialysis, concentrations are measured by dry matter content. The additives will then be used as is. Paper Characterization:

[0113] Oxidized polysaccharides are added to a fibrous Kraft pulp suspension at 2 g / l to achieve an additive concentration of 0.01% by mass. After 1 hour of stirring, the mixture is formed by filtration.

[0114] The resulting papers are tested in tensile strength in the dry state and then after 48 hours of immersion in deionized water. The different polysaccharides will be compared to XGOX20 and to a reference paper without additives in Table 11 (below). Conclusion :

[0115] Under the test conditions, the performance of oxidized polysaccharides derived from guar gum and locust bean gum differs significantly from that of oxidized xyloglucan. The differences are striking in both dry and wet conditions. Table 11 Paper ref 0.01% XGOX20 0.01% GOx10 0.01% GOx20 0.01% LOx10 0.01% LOx20 Ultimate stress (MPa) dry 6,53 (1,2) 14,68 (2,5) 9,60 (1,36) 8,66 (0,95) 8,85 (0,32) 7,10 (1,01) humid 0 1,25 (0,2) 0,03 (0,02) 0,06 (0,04) 0,10 (0,06) 0,14 (0,03) Example 6: Functionalization test using a dye

[0116] To demonstrate the reactivity of the remaining available aldehyde functions, an unadditized Kraft paper is made as follows: 1 l of suspension at 2 g / l of Kraft fiber is filtered under vacuum, then dried at room temperature.

[0117] Papers with added XgOx20, XgOx44 and Oxidized Guar (GOx44) or Oxidized Carob (Cox44) oxidized as in the previous protocol are made as follows: 1l of 2 g / l Kraft fiber suspension containing 0.1% or 0.01% mass of XgOx20 or XgOx44 or GOx44 or Cox44 are vacuum filtered, then dried at room temperature.

[0118] A 1 cm² sample of each of the papers, additive or not, is taken and then immersed in a 2,4-Dinitrophenylhydrazine (DNPH) solution prepared as follows: 0.19813 of DNPH is weighed and then dissolved in a mixture of 3 mL of 37% HCl, 20 mL of ethanol, and 20 mL of water in a 100 mL volumetric flask. After adding ethanol up to the calibration mark, a 0.01 mol / L DNPH solution is obtained.

[0119] The samples are left in the DNPH solution for 48 hours. After thorough rinsing, the unadditized paper has a pale yellow color, while the added papers show a very marked orange color (particularly Cox44 0.1%, XgOx44 0.1 and 0.01%), indicating the grafting of DNPH onto the aldehydes of the oxidized polysaccharide present in the paper, depending on the dosage and nature of the additive, according to the following reaction:

[0120] In a photograph (not shown) it can be seen that the non-additized paper and the additized paper after contact with the DNPH solution and rinsing show different colours with a pale yellow paper for the non-additized paper and orange for the additized paper.

Claims

1. A compound comprising an association of at least one polysaccharide adsorbed on a cellulosic material, said polysaccharide being an oxidized xyloglucan comprising at least two different monosaccharide units, forming first and second monosaccharide units, said second monosaccharide units being branched on a chain comprising at least said first monosaccharide units, at least some of the second monosaccharide units being non-cyclic and bearing aldehyde functions, said aldehyde functions possibly forming hemiacetal functions with hydroxy functions of the cellulosic material.

2. The compound according to claim 1, characterized in that the non-cyclic branched monosaccharides bearing aldehyde functions are oxidized xyloses.

3. The compound according to claim 1 or 2, characterized in that the adsorbed polysaccharide is selected from the group composed of a tamarind seed xyloglucan (TXG), a pea xyloglucan and any of the mixtures thereof.

4. The compound according to any of claims 1 to 3, characterized in that the polysaccharide is oxidized by a periodate, and preferably the sodium metaperiodate.

5. The compound according to any of claims 1 to 4, characterized in that the polysaccharide has a degree of oxidation higher than 0 % and lower than or equal to 50%, and preferably lower than or equal to 40 %, and preferably still lower than or equal to 30 %, expressed in number of oxidized saccharide units out of the total number of saccharide units.

6. The compound according to any of claims 1 to 5, characterized in that the polysaccharide is covalently bonded to the cellulosic material by hemiacetal functions between aldehyde functions of branched monosaccharides and hydroxy functions of the cellulosic material.

7. The compound according to any of claims 1 to 6, characterized in that the polysaccharide is also covalently bonded by one or more reactive molecules, and in particular at least two reactive molecules, reacting with aldehyde functions of the polysaccharide, said reactive molecules being for example selected from the group comprising amines, polyamines, hydroxylamines, imines, hydrazide, and any of the combinations thereof.

8. A method for covalently binding a cellulosic material with a polysaccharide, said method comprising the adsorption of a polysaccharide on a cellulosic material, the adsorption being conducted with the cellulosic material in an aqueous medium, the said method comprising prior to adsorption of the polysaccharide on the cellulosic material, a step to oxidize a precursor polysaccharide of the adsorbable polysaccharide on the cellulosic material, the oxidation step being controllable to oxidize solely the branches of the polysaccharide, the oxidation of the polysaccharide being carried out by an oxidizing agent, preferably a periodate, said adsorbable polysaccharide being an oxidized xyloglucan comprising non-cyclic branched monosaccharides bearing aldehyde functions, said aldehyde functions forming hemiacetal functions with hydroxy functions of the cellulosic material to form a compound according to any of claims 1 to 7.

9. The method according to claim 8, characterized in that the compound according to any of claims 1 to 7 is formed and dried in the form of paper, fibres, nonwovens.

10. The method according to claim 8 or 9, characterized in that the polysaccharide which is covalently bonded to the cellulosic substrate is caused to react with one or more reactive molecules reacting with aldehyde functions of the polysaccharide, said reactive molecules being for example selected from the group consisting amines, polyamines, hydroxylamines, imines, hydrazide, and any of the combinations thereof.

11. Use of a polysaccharide as reinforcing additive for cellulosic material comprising hydroxy functions, said polysaccharide being an oxidized xyloglucan comprising non-cyclic branched monosaccharides bearing aldehyde functions, wherein some aldehyde functions possibly form hemiacetal functions with hydroxy functions of the cellulosic material, said polysaccharide being able to adsorb on the cellulosic material, and preferably to form a compound according to any of claims 1 to 7.

12. The use according to claim 11, characterized in that the polysaccharide is used as additive to reinforce the strength in the wet state, and preferably in the dry and wet state, of a cellulosic material comprising hydroxy functions.