Cationic dyes and their uses

Abstract

To provide a cationic dye and its use which enables highly efficient dyeing of fibers such as textile fibers. [Solution] The present invention relates to novel nanocellulose-based cationic dyes, processes for their synthesis, and their use in processes for dyeing fibers, such as textile fibers. The cationic dyes of the present invention comprise nanocellulose, at least one cationic moiety covalently attached to the nanocellulose, and at least one coloring moiety attached to the nanocellulose.

Description

[Technical field]

[0001] The present invention relates to novel nanocellulose-based cationic dyes, their synthesis process and their use in dyeing processes of fibers, especially textile fibers. [Background technology]

[0002] The growing population and current lifestyle have created an increasing demand for clothing consumption, amplifying the need for textile dyeing.

[0003] Textile dyeing processes are generally energy intensive, require long reaction times and / or the use of high temperatures, and produce large volumes of, and often toxic, wastewater.

[0004] Dyeing of cotton fibers has been mainly carried out with reactive dyes for the past few decades because they are cost-effective and can produce a wide range of colors. These dyes usually contain aromatic chromophores and amine auxochromes, which give the dye its color properties. These dyes further contain reactive groups, such as chlorine residues, which can attach the dye to the fabric surface by covalent bonds. Reactive dyes provide very strong fixation of the dye to the fabric and exhibit excellent dyeing properties. However, chloride ions are released during the chemical reaction, which results in chloride-containing wastewater and colored sewage. Reactive dyeing also requires high thermal energy and pretreatment with salt-saturated solutions to suppress the repulsion between the negatively charged dye molecules and the cotton fibers. Electrolytes such as sodium chloride, sodium carbonate, and sodium sulfate are added to the dye bath to improve the interaction between the dye and the fabric. The electrolyte concentration is gradually increased to accelerate the exhaustion of the dye, producing high concentrations of wastewater with a COD value equivalent to 50,000 ppm.

[0005] Mordant dyes can also be used for dyeing cotton fibers. Natural dyes, also called direct dyes, are derived from natural resources such as animals and plants, making natural dyes more environmentally friendly than reactive dyes. However, these dyes do not form strong covalent bonds with the surface of cotton. They bind with cellulose fibers through electrostatic bonds, weak van der Waals forces and / or hydrogen bonds. To increase the affinity of natural dyes, metal mordants are used as pretreatments for dyeing. Mordants bind with fibers and dyes through strong coordination bonds to fix the dye molecules on the fiber surface. Traditionally, toxic chromium, iodine, cobalt and / or nickel complexes were used as mordants. Recently, less toxic metals such as copper, iron and aluminum have been adopted as more environmentally friendly pretreatments. However, the problem of excessive metal concentrations in wastewater and the need for huge amounts of water still remains. Natural bio-mordants can also be used as green alternatives to metal mordants. For example, whey protein, a mixture of three proteins, bovine serum albumin, was used to improve the affinity of pomegranate natural dyes to cotton through hydrogen bonding and to reduce the negative charge repulsion between the fabric and the dye molecules. Unfortunately, such products are not widely used in industry due to their high manufacturing costs.

[0006] In recent years, several processes have been developed with the aim of reducing the environmental impact of the cotton dyeing process.

[0007] Anuradhi Liyanapathiranage et. al.”Nanocellulose-based sustainable dyeing of cotton textiles with minimized water pollution” ACS Omega 2020,5,16,p.9196-9203 (Non-Patent Document 1) discloses a dyeing process for cotton fibers using reactive dyes incorporated into pure nanocellulose fibers containing hemicellulose. The dyeing process is carried out at 60°C for 90 minutes, and salts are used to create affinity between the dye and the fiber. To further improve fixation and reduce hydrophilicity, a post-treatment with polycarboxylic acids such as citric acid or maleic acid is performed, and the fibers are immersed in the solution and dried at a high temperature of 120°C.

[0008] Smriti et al. "Environment-friendly nanocellulose-indigo dyeing of textiles" Green Chem.2021, 23, p.7937 (Non-Patent Document 2) discloses a dyeing process for cotton fibers with a dye containing natural indigo incorporated into nanocellulose fibers. The nanocellulose fiber dispersion is mixed with agglomerated indigo and surfactant Triton(R) X-100. The resulting suspension is mixed with cotton fibers and a drying step is carried out at 120°C. In order for the dyeing to withstand washing of the cotton fabric, a post-treatment is required that includes the adsorption of a chitosan solution. This post-treatment involves immersing the dyed cotton fabric in chitosan for 15 minutes and then drying at 120°C.

[0009] CN113914124 (Patent Document 1) discloses modified nanocellulose and its use for the preparation of base paper with improved mechanical properties. The modified nanocellulose is composited with titanium dioxide and can be used as an additive to base paper pulp.

[0010] CN105080503 (Patent Document 2) discloses nanocellulose-polyvinylamine-microgel and its use for absorbing dye substances, especially anionic dyes and heavy metal ions, in wastewater. Nanocellulose-polyvinylamine-microgel is not cationic and coloring at the same time: if the dispersion medium is acidic, the amine moiety is chelated to the anionic dye, resulting in a material that is not cationic. If the dispersion medium is neutral or basic, the amine moiety is not cationic.

[0011] US2013 / 0211308 (Patent Document 3) discloses nanocellulose coated with nanosilver and its use in the manufacture of medical devices and antibacterial clothing. This material is formed by oxidizing nanocellulose to form aldehyde functional groups, followed by a Schiff reaction between amine groups and the aldehydes. The resulting material is not cationic.

[0012] Cellulose (2015) 22:2443-2456 (Non-Patent Document 3) discloses amino-functionalized nanocrystalline cellulose (ANCC) as an adsorbent for anionic dyes in wastewater treatment. ANCC does not have cationic and coloring properties at the same time.

[0013] Molecules, 2021, 26, 7315 (Non-Patent Document 4) discloses amino-functionalized nanocrystalline cellulose and its use for adsorption and removal of cations and anions from wastewater. Amino-functionalized nanocrystalline cellulose does not have cationic and coloring properties at the same time.

[0014] US9506187 (Patent Document 4) discloses a method for dyeing textile products using dyed nanocellulose dispersions. Nanocellulose does not have cationic moieties, only colored moieties. This dyeing method requires heating the dye bath to 80°C and uses salt.

[0015] Materials, 2019, 12, 3144 (Non-Patent Document 5) discloses the functionalization of cellulose nanofibrils with chitosan. Carboxyl and aldehyde groups are introduced onto the viscose backbone by a TEMPO-based oxidation treatment. The resulting fibers exhibit antibacterial properties and improved resistance to washing cycles.

[0016] There remains therefore a need for the development of new dyes which are suitable for carrying out an efficient dyeing process of fibres, such as cotton fibres, allow efficient fixation of the dye on the fibre, preferably do not require any after-treatment, require as low an energy consumption as possible, e.g. by using only low temperatures, and limit the generation of waste liquors, both in terms of volume and toxicity, so as to limit the necessary re-treatment of the waste liquors. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Chinese Patent No. 113914124 [Patent Document 2] Chinese Patent No. 105080503 [Patent Document 3] US Publication No. 2013 / 0211308 [Patent Document 4] U.S. Patent No. 9,506,187 [Non-patent literature]

[0018] [Non-Patent Document 1] Anuradhi Liyanapathiranage et.”Nanocellulose-based sustainable dyeing of cotton textiles with minimized water pollution” ACS Omega 2020,5,16,p.9196-9203 [Non-Patent Document 2] Smriti et al. “Environment-friendly nanocellulose-indigo dyeing of textiles” Green Chem.2021, 23, p.7937 [Non-Patent Document 3] Cellulose (2015) 22 :2443-2456 [Non-Patent Document 4] Molecules, 2021, 26, 7315 [Non-Patent Document 5] Materials, 2019, 12, 3144 [Non-Patent Document 6] J. Phys. Chem.C 2011, 115, 2, 390 396, December 13, 2010 [Non-Patent Document 7] Journal of Nanoparticle Research, Vol. 14, Article No. 755 (2012), March 6, 2012 [Non-Patent Document 8] Journal of Nanoscience Volume 2017, Page 7, Article ID 8348507, January 3, 2017 Summary of the Invention [Problem to be solved by the invention]

[0019] The applicant has surprisingly demonstrated that the use of highly specific dyes containing both colored and cationic moieties attached to specific positions on the glycosidic rings of nanocellulose allows for highly efficient dyeing of fibres, such as textile fibres, which dyeing processes using said dyes provide, among other advantages, improved colour fastness, shorter dyeing times and / or reduced energy consumption. [Means for solving the problem]

[0020] Thus, the present invention relates to a cationic dye comprising: - nanocellulose, at least one cationic moiety covalently attached to the nanocellulose; and - at least one coloring moiety bound to said nanocellulose.

[0021] In a preferred embodiment, the cationic moiety and the coloring moiety are attached to different carbon atoms of the nanocellulose backbone.

[0022] In some embodiments, the cationic moiety is covalently attached to the nanocellulose at the C2 and / or C3 position(s) of at least one glucose moiety of the nanocellulose.

[0023] In some embodiments, the coloring moiety is linked to the nanocellulose by ionic and / or hydrogen bonds at the C6 position of at least one glucose moiety of the nanocellulose.

[0024] In some embodiments, the nanocellulose is selected from the group consisting of cellulose nanofibers, cellulose nanocrystals, and any mixture thereof, preferably, the nanocellulose is a cellulose nanocrystal.

[0025] In some embodiments, the at least one cationic moiety comprises a quaternized amine group, preferably a quaternized primary amine group.

[0026] In some embodiments, the at least one cationic moiety is selected from the group consisting of a quaternized diamine moiety, a quaternized amino acid, a quaternized peptide, and a quaternized protein.

[0027] In some embodiments, the colored portion is a colored mineral portion.

[0028] In some embodiments, the colored moiety is a metal or metal oxide.

[0029] In some embodiments, the colored mineral portion is iron oxide.

[0030] In a preferred embodiment of the method for synthesis of the cationic dye, the colouring moiety is introduced as a precursor.

[0031] In a preferred embodiment, the at least one cationic moiety and the at least one colored organic or mineral moiety are different moieties in said cationic dye.

[0032] The present invention further relates to a process for the synthesis of said cationic dye according to the present invention, comprising the following steps: (i) contacting the optionally modified nanocellulose with a coloring moiety or a precursor thereof; and (ii) contacting the optionally modified nanocellulose with a cationic moiety to obtain a cationic dye.

[0033] The present invention further relates to a process for the synthesis of said cationic dye according to the present invention, comprising the following steps: (i) contacting the optionally modified nanocellulose with a coloring moiety or a precursor thereof to obtain partially functionalized nanocellulose; and (ii) contacting the optionally modified partially functionalized nanocellulose obtained in step (i) with a cationic moiety to obtain a cationic dye according to the invention.

[0034] In one embodiment, the method for synthesizing the cationic dye comprises oxidizing at least a portion of the OH groups of the optionally modified nanocellulose to aldehyde moieties.

[0035] In a preferred embodiment of the method for the synthesis of cationic dyes, NaIO4 is used to oxidize at least a portion of the OH groups of the optionally modified nanocellulose to aldehyde moieties.

[0036] The present invention further relates to a process for dyeing at least a part of a textile material, comprising the following steps: a) contacting at least a portion of said textile material with a pretreatment agent, preferably selected from the group consisting of an oxidizing agent and a hydrolyzing agent, to obtain a pretreated textile material; and b) contacting said pretreated textile material obtained in step a) with at least one cationic dye according to the present invention to obtain a dyed textile material.

[0037] In some embodiments, the fiber material is a woven fiber material.

[0038] In some embodiments, the fiber material is selected from the group consisting of cotton fiber materials, polyester fiber materials, keratin fiber materials, and mixtures thereof.

[0039] In some preferred embodiments, the dyeing step is carried out at a temperature between 20°C and 50°C, more preferably between 20°C and 30°C.

[0040] In some preferred embodiments, the staining step is carried out in the absence of salts.

[0041] In some embodiments, the oxidizing agent is selected from the group consisting of TEMPO, TEMPO in the presence of iron, potassium hydrogen persulfate, hydrogen peroxide, hydrogen peroxide in the presence of iron (preferably the iron cation), and sodium metabisulfite.

[0042] In some embodiments, the process for dyeing at least a part of the fibrous material comprises, after step b), c) drying the dyed textile material obtained in step b) at a temperature below 100°C.

[0043] (definition) In the present invention, the following terms have the following meanings:

[0044] "About" before a number or numerical value refers to plus or minus 10% of the face value of that number or numerical value, preferably plus or minus 5%, and more preferably plus or minus 1%.

[0045] A "cationic moiety" is a moiety that carries at least one positive charge under the experimental conditions to which it is applied, preferably those used in the dyeing process.

[0046] A "cationic dye" is a dye that carries at least one positive charge under the experimental conditions under which it is applied, preferably those used in the dyeing process.

[0047] "Cellulose nanocrystals", also called CNCs, are crystalline nanostructures that consist essentially of cellulose molecules. CNCs do not contain amorphous regions and therefore exhibit an elongated crystalline rod-like shape with extremely limited flexibility compared to cellulose nanofibers. CNCs are also called nanowhiskers, nanorods, and rod-like cellulose crystals. CNCs are usually isolated from cellulose fibers by acid hydrolysis. CNCs have a relatively low aspect ratio, and CNCs have a typical diameter of 2-20 nm and a wide length distribution from 100-600 nm.

[0048] "Cellulose nanofibers", also called CNFs, are nanoscale fibers that consist essentially of cellulose molecules. CNFs are approximately 3 nm in diameter and micron-scale in length, and exhibit both crystalline and amorphous portions. CNFs can be prepared by TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxy)-mediated oxidation of cellulose, followed by mechanical treatment with a homogenizer.

[0049] A "coloring moiety" is a moiety that is itself colored and / or that imparts color to the dye when it is bound to nanocellulose. The coloring moiety is preferably bound to the nanocellulose via ionic and / or hydrogen bonds. The coloring moiety contained in the dye according to the invention can be bound to its precursor, e.g. Fe 2+, to nanocellulose and then forming a colouring moiety, preferably iron oxide, in situ from the precursor.

[0050] "Covalent bond", when used to modify binding or fixation, refers to the characteristic of the bond between two atoms resulting from a pool of electrons coming separately from their respective atoms. According to the present invention, the covalent bond of two moieties can be the bond of said two moieties via a linker moiety that is covalently bonded to each moiety. The linker moiety can be an atom or a chain of covalently bonded atoms.

[0051] "Dye" refers to a natural or synthetic substance used to impart color or change the color of textile materials, especially textile textile materials.

[0052] A "textile material" is a material that comprises or consists of at least one type of fiber. The textile material may be a material that comprises or consists of threads, which themselves comprise or consist of fibers. Preferably, the textile material that comprises or consists of fibers is a woven textile material. The term "woven fibers" includes any fiber that can be used in the textile field, in particular any fiber that can be dyed and used in the textile field. In some embodiments, the textile material comprises one type of fiber. In other embodiments, the textile material comprises at least two different types of fibers.

[0053] "From X to Y" refers to a range of values ​​between X and Y, where the limits X and Y are included in the range.

[0054] A "mineral" moiety is an atom or group of atoms that does not contain a carbon atom.

[0055] "Nanocellulose" refers to nanostructures of cellulose. Nanocellulose exists in three particular forms: cellulose nanofibers (CNF), cellulose nanofibrils and cellulose nanocrystals (CNC).

[0056] An "organic" moiety is a covalently bonded group of atoms containing at least one carbon atom.

[0057] A "pretreatment agent" is a chemical agent that is contacted with at least a portion of the textile material to be dyed before the textile material is contacted with the dye. In particular, the contact with the pretreatment agent and the contact with the dye may be performed simultaneously. By contacting the textile material with the pretreatment agent under suitable conditions, the textile material is endowed with interesting properties in view of its further dyeing. For example, by contacting the textile material with the pretreatment agent under suitable conditions, chemical moieties can be formed on the surface of the textile material, which chemical moieties make it possible to increase the effectiveness and / or shorten the duration of the further dyeing step.

[0058] "Quaternized," when referring to a chemical moiety that contains an amine moiety, means that the amine nitrogen atom is bonded to four different atoms, thereby carrying a positive charge. [Brief description of the drawings]

[0059] [Figure 1] 1 is a graph showing the XRD analysis of the cationic dye of Example 3, with the intensity in arbitrary units on the ordinate and the 2-theta angle on the abscissa. D shows the spectrum of the iron oxide dye and C shows the spectrum of the cellulose. [Diagram 2] 1 is a graph showing the XRD analysis of the cationic dye of Example 4, with the ordinate representing intensity in arbitrary units and the abscissa representing 2-theta angle. D shows the spectrum of the iron oxide dye and C shows the spectrum of the cellulose. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] (Cationic dyes) A first object of the present invention is to provide a cationic dye comprising: Nanocellulose, at least one cationic moiety covalently attached to the nanocellulose; and at least one coloring moiety bound to the nanocellulose; A cationic dye comprising:

[0061] (Nanocellulose) The nanocellulose constituting the cationic dye according to the present invention may be any nanostructure of cellulose. In some embodiments, the nanocellulose contained in the cationic dye according to the present invention is selected from the group consisting of cellulose nanofibers (CNF), cellulose nanofibrils and cellulose nanocrystals (CNC). In a preferred embodiment, the nanocellulose contained in the cationic dye according to the present invention is selected from the group consisting of cellulose nanofibers (CNF) and cellulose nanocrystals (CNC). In a more preferred embodiment, the nanocellulose contained in the cationic dye according to the present invention is cellulose nanocrystals (CNC).

[0062] Without wishing to be bound by any theory, the inventors believe that the use of CNCs as nanocellulose composed of cationic dyes according to the invention allows for better penetration of the dye into the fibres due to their smaller size than that of CNFs.

[0063] Typically, the CNCs contained in the cationic dyes according to the present invention have a length in the range of 100 nm to 600 nm, preferably in the range of 100 nm to 300 nm.Typically, the CNCs contained in the cationic dyes according to the present invention have a diameter in the range of 2 to 20 nm, preferably in the range of 2 to 5 nm.

[0064] Nanocellulose is a homopolymer formed from linear chains of D-glucose moieties. Each glycosidic ring of cellulose has three hydroxyl OH groups at positions C2, C3 and C6. The numbering of the positions on the glycosidic ring is as shown in the formula below:

[0065] [ka]

[0066] (cationic moiety) The cationic moiety contained in the cationic dye according to the invention may be any chemical moiety having at least one positive charge, preferably exactly one positive charge. In some embodiments, the cationic moiety has one or more positive charges, for example the cationic moiety has 2 to 10 positive charges, in particular the cationic moiety has 2, 3, 4, 5, 6, 7, 8, 9 or 10 positive charges. The presence of one or more positive charges on the cationic moiety may improve the binding of the cationic dye to the fiber material. The cationic moiety is preferably covalently bonded to at least one OH group at the C2 or C3 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the invention.

[0067] In some embodiments, all of the OH groups at the C2 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the present invention are substituted with a cationic moiety.

[0068] In other embodiments, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the OH groups at the C2 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the present invention are substituted with a cationic moiety.

[0069] In some embodiments, 10% to 90%, preferably 20% to 80%, more preferably 30% to 70%, even more preferably 40% to 60%, and especially about 50% of the OH groups at the C2 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the invention are substituted with a cationic moiety. The proportion of the OH groups at the C2 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the invention substituted with a cationic moiety can vary within a wide range, depending, inter alia, on the structure and steric hindrance of the cationic moiety.

[0070] In some embodiments, all of the OH groups at the C3 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the present invention are substituted with a cationic moiety.

[0071] In other embodiments, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the OH groups at the C3 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the present invention are substituted with a cationic moiety.

[0072] In some embodiments, 10% to 90%, preferably 20% to 80%, more preferably 30% to 70%, even more preferably 40% to 60%, and especially about 50% of the OH groups at the C3 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the invention are substituted with a cationic moiety. The proportion of the OH groups at the C3 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the invention substituted with a cationic moiety can vary over a wide range, depending, inter alia, on the structure and steric hindrance of the cationic moiety.

[0073] The cationic moiety may be any moiety that contains at least one positive charge under experimental conditions. In some embodiments, the cationic moiety comprises a positively charged nitrogen atom or phosphorus atom in its structure. In some embodiments, the cationic moiety comprises a quaternized ammonium or quaternized amine in its structure.

[0074] In some embodiments, the cationic moiety is selected from the group consisting of a quaternized diamine moiety, a quaternized amino acid, a quaternized peptide, and a quaternized protein.

[0075] (Colored part) The colored organic or mineral moiety may be any organic or mineral moiety that is colored by itself and / or that becomes colored once fixed to the nanocellulose of the cationic dye according to the invention. The colored moiety is preferably bonded to at least one OH group at the C6 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the invention.

[0076] In some embodiments, all of the OH groups at the C6 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the present invention are substituted with a coloring moiety.

[0077] In other embodiments, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the OH groups at the C6 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the invention are substituted with a coloring moiety.

[0078] In some embodiments, 10% to 90%, preferably 20% to 80%, more preferably 30% to 70%, even more preferably 40% to 60%, and especially about 50% of the OH groups at the C6 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the present invention are substituted with a coloring moiety. The proportion of OH groups at the C6 position of the glycosidic ring of the nanocellulose contained in the cationic dye according to the present invention substituted with a coloring moiety can vary over a wide range, depending, inter alia, on the structure and steric hindrance of the coloring moiety.

[0079] In some embodiments, the coloring moiety is a coloring organic moiety. The coloring organic moiety may be selected, for example, from the group consisting of direct dyes and natural dyes.

[0080] In some embodiments, the colored portion is a colored mineral portion. The colored mineral portion may be selected from the group consisting of metal oxides, colored structures formed from one or more metals, such as copper, zinc, titanium, vanadium, nickel, gold and / or silver, and any mixture or complex thereof. In a preferred embodiment, the colored mineral portion is selected from the group consisting of metal oxides. The colored mineral portion may exhibit different structures, such as a core-shell structure.

[0081] The metal oxide may be selected, for example, from the group consisting of iron oxide, cobalt oxide, chromium oxide, copper oxide, manganese dioxide, nickel oxide, and any mixtures or composites thereof.

[0082] In some embodiments, the iron oxide is selected from the group consisting of Fe3O4 (black), Fe(OH)O (yellow), and Fe2O3 (red), and mixtures thereof. In a preferred embodiment, the iron oxide is Fe3O4.

[0083] In some embodiments, the colored portion comprises a nanostructure, such as a nanoparticle or nanocomposite of the colored mineral portion. Preferably, the colored portion comprises or consists of iron oxide nanoparticles, particularly Fe3O4 nanoparticles.

[0084] The coloured mineral portion is preferably crystalline.

[0085] In some embodiments, the colored mineral portion further comprises at least one impurity. Classical impurities to be included in the colored mineral portion are well known in the art in terms of the chemical structure of the colored mineral portion and / or the desired color obtained. In some embodiments, the at least one impurity is selected from the group consisting of magnesium, potassium and calcium. In some embodiments, the colored mineral portion comprises at least one impurity selected from the group consisting of a metal oxide such as iron oxide and preferably magnesium, potassium and calcium.

[0086] The at least one impurity can be present in the colored mineral portion, which includes at least one metal oxide, preferably iron oxide, in any suitable amount to obtain the desired color.

[0087] To obtain a coloured mineral moiety comprising a metal oxide, in particular iron oxide, and at least one impurity, the impurity may be present during the in-situ formation of the coloured mineral moiety from its precursor, said precursor being bound to the nanocellulose.

[0088] Without wishing to be bound by any theory, the inventors believe that impurities fill some or all of the gaps in the crystal structure of the metal oxide, e.g., iron oxide, thereby modifying the reflection of light through the crystal and inducing a shift in the reflected wavelength.

[0089] In some embodiments, the coloring moiety has a positive charge and is therefore a cationic moiety, in such embodiments, the at least one cationic moiety and the at least one coloring moiety may be the same moiety or may be different moieties.

[0090] In one embodiment, the at least one cationic moiety and the at least one coloring moiety are different moieties.

[0091] The method according to the invention gives access to cationic dyes where the coloring moiety is either neutral or cationic, which was not possible with the prior art methods that use cationic functionalized nanocellulose to capture anionic dyes.

[0092] (synthesis) A second object of the present invention is the synthesis process of the cationic dye according to the present invention.

[0093] Despite the difficulties in selectively functionalizing different positions of the glycosidic ring of cellulose, the inventors of the present invention have unexpectedly demonstrated that by carrying out the synthetic process of the present invention, it is possible to successfully attach both colored organic or mineral moieties present only at the C6 position of the glycosidic ring of nanocellulose, and cationic moieties present only at the C2 and / or C3 positions of the glycosidic ring of nanocellulose.

[0094] The steps of the synthesis process according to the invention are suitable for covalently binding cationic moieties to at least a portion of the hydroxy groups at the C2 and / or C3 position(s) of the glycosidic ring of the nanocellulose, and for binding colouring moieties, preferably via ionic and / or hydrogen bonds, to at least a portion of the hydroxy groups at the C6 position of the glycosidic ring of the nanocellulose.

[0095] The synthesis process according to the present invention comprises the following steps: (i) contacting the optionally modified nanocellulose with a colouring moiety or a precursor thereof; (ii) contacting the optionally modified nanocellulose with a cationic moiety to obtain a cationic dye.

[0096] According to this embodiment, steps (i) and (ii) can be performed in the order recited ((i) then (ii)) or step (ii) can be performed before step (i). The two variants presented below illustrate these two possibilities.

[0097] According to a first variant, the synthesis process according to the invention comprises the following steps: (ia) contacting the optionally modified nanocellulose with a coloring moiety or a precursor thereof to obtain partially functionalized nanocellulose; and (iia) contacting the optionally further modified partially functionalized nanocellulose obtained in step (ia) with a cationic moiety to obtain a cationic dye.

[0098] According to another variant, the synthesis process according to the invention comprises the following: (iib) contacting the optionally modified nanocellulose with a cationic moiety to obtain partially functionalized nanocellulose; and (ib) contacting the optionally further modified partially functionalized nanocellulose obtained in step (iib) with a coloring moiety or a precursor thereof to obtain a cationic dye.

[0099] (Preliminary process)

[0100] The synthesis process according to the invention may comprise at least one preliminary step (0) of pretreatment of cellulose or nanocellulose before step (i) and before step (ii). Said step may comprise, for example, enzymatic desizing, cutting, mechanical desizing and / or swelling of cellulose or nanocellulose. Said step comprises, in another embodiment, a suitable pretreatment of cellulose to obtain nanocellulose, in particular to obtain cellulose nanofibers, cellulose nanocrystals or a mixture thereof.

[0101] (Step (i))

[0102] Step (i) may be carried out by any suitable technique known in the art.

[0103] The optional modification of nanocellulose in step (i) may be a modification to form negatively charged moieties, such as carboxylate COO- or sulfonate SO3- moieties, on the nanocellulose. For example, the optional modification of nanocellulose in step (i) may be selectively converting at least a portion of the primary OH groups at the C6 position of the nanocellulose to carboxylate or sulfonate moieties, preferably carboxylate moieties. In one embodiment, the conversion is the oxidation of at least a portion of the primary OH groups at the C6 position of the nanocellulose to carboxylate moieties.

[0104] In some embodiments, the coloring moiety, in particular the coloring organic or mineral moiety, is attached to the nanocellulose in step i) by reacting the coloring moiety with an optionally modified nanocellulose, for example oxidized nanocellulose containing a carboxylate moiety at the C6 position. For example, an organic colorant having an -OH group can be reacted with the carboxylate moiety at the C6 position to generate an ester bond between the nanocellulose backbone and the coloring moiety. Examples of such organic colorants include alizarin, hematoxylin, carminic acid, luteolin, curcumin, Disperse Red 60, Acid Orange 7, etc.

[0105] In another embodiment, the bond between the coloring moiety and the nanocellulose in step (i) is formed by the addition of a precursor of the coloring moiety, e.g., Fe 2+ The colored moieties can be obtained by reacting a metal positively charged ion such as CrN, ...

[0106] In another embodiment, the bond between the coloring moiety and the nanocellulose in step (i) is formed by the addition of a precursor of the coloring moiety, e.g. Fe 2+With nanocellulose, positively charged metal ions such as , and further converting the precursor into a colored moiety in situ, for example by contacting the precursor immobilized on nanocellulose with a reducing agent.

[0107] The in-situ conversion of the precursors into the colored moieties can be carried out under different temperature conditions and / or in the presence of different impurities such as calcium, potassium, magnesium, manganese, etc., in order to modify the chemical structure and / or size of the formed colored moieties, in particular the iron oxides.

[0108] In some embodiments, particularly when the coloring moiety is a coloring organic moiety, step (i) is carried out by contacting the unmodified nanocellulose with the coloring moiety. In that case, it is preferable to use a coloring moiety having a reactive group capable of forming a covalent bond with the -OH group at the C6 position of the nanocellulose. Examples of such organic colorants include direct dyes, reactive dyes, indigo dyes, etc.

[0109] (Step (ii))

[0110] Step (ii) may be carried out by any suitable technique known in the art.

[0111] The further optional modification of the partially functionalized or non-functionalized nanocellulose in step (ii) may be a modification to form reactive sites for further covalent attachment of cationic moieties. For example, the optional modification of the partially functionalized nanocellulose in step (ii) may be a selective oxidation of the OH groups at the C2 and / or C3 positions of the nanocellulose to aldehyde moieties. Preferably, the modification of the nanocellulose in step (ii) consists of a selective oxidation of the OH groups at the C2 and / or C3 positions of the nanocellulose to aldehyde moieties, and more advantageously, the method modification of the nanocellulose in step (ii) uses NaIO4 as an oxidizing agent.

[0112] In some embodiments, the synthetic process according to the present invention comprises the following: a) contacting nanocellulose with at least one oxidizing agent suitable for selectively oxidizing at least a portion of the primary OH groups at the C6 position of the nanocellulose to carboxylate moieties to obtain partially oxidized nanocellulose; b) contacting the partially oxidized nanocellulose obtained in step (a) with a coloring moiety or a precursor thereof as defined above to obtain a partially functionalized nanocellulose; c) contacting the partially functionalized nanocellulose obtained in step (b) with at least one oxidizing agent suitable for selectively oxidizing at least a portion of the OH groups at the C2 and / or C3 positions of the nanocellulose to aldehyde moieties to obtain an aldehyde-modified partially functionalized nanocellulose; and d) contacting the aldehyde-modified partially functionalized nanocellulose obtained in step (c) with a cationic moiety comprising an amine moiety, and optionally a reducing agent, to obtain a cationic dye according to the present invention.

[0113] (Oxidation step (a))

[0114] The oxidation step (a) may be carried out by any suitable method known in the art for oxidizing at least a portion of the primary OH groups at the C6 position of nanocellulose to carboxylate moieties. Any suitable oxidizing agent may be used to carry out the oxidation step (a). In some embodiments, the oxidizing agent used in step (a) is selected from the group consisting of TEMPO and potassium hydrogen persulfate (Oxone).

[0115] (Partial functionalization step (b))

[0116] The partial functionalization step (b) may be carried out under any suitable conditions to fix the coloring moiety or its precursor to the partially oxidized nanocellulose. The features and embodiments disclosed above for step (i) apply equally to the partial functionalization step (b).

[0117] (Further oxidation step (c))

[0118] The further oxidation step (c) may be carried out by any suitable method known in the art for oxidizing at least a portion of the OH groups at the C2 and / or C3 positions of the nanocellulose to aldehyde moieties. Any suitable oxidizing agent may be used to carry out the further oxidation step (c). In some embodiments, the oxidizing agent used in step (c) is a periodate, such as sodium metaperiodate.

[0119] (Further functionalization step (d))

[0120] The further functionalization step (d) may be carried out under any suitable conditions for fixing cationic moieties to the aldehyde-modified partially functionalized nanocellulose. The further functionalization step (d) may be carried out by reductive amination in the presence of cationic moieties comprising amine moieties, in particular diamines, and a reducing agent such as sodium borohydride. The cationic moieties contacted in step (d) with the aldehyde-modified partially functionalized nanocellulose do not necessarily carry a positive charge when both compounds are contacted. In such an embodiment, step (d) comprises a further step of subjecting the further functionalized nanocellulose to suitable experimental conditions for imparting at least one positive charge to the cationic moieties in order to obtain a cationic dye according to the invention. The further step may, for example, be exposing the further functionalized nanocellulose to acidic conditions to form quaternized amine moieties.

[0121] In some embodiments, the synthetic process according to the present invention comprises the following: a') contacting nanocellulose with at least one agent suitable for converting at least a portion of the primary OH groups at C6 position of the nanocellulose into sulfonic acid moieties to obtain partially sulfonated nanocellulose; b') contacting the partially sulfonated nanocellulose obtained in step (a') with a coloring moiety or a precursor thereof as defined above to obtain a partially functionalized nanocellulose; c') contacting the partially functionalized nanocellulose obtained in step (b') with at least one oxidizing agent suitable for selectively oxidizing at least a portion of the OH groups at the C2 and / or C3 positions of the nanocellulose to aldehyde moieties to obtain an aldehyde-modified partially functionalized nanocellulose; and d') contacting the aldehyde-modified partially functionalized nanocellulose obtained in step (c') with a reducing agent and a cationic moiety comprising an amine moiety to obtain a cationic dye according to the present invention.

[0122] Step (a') may be carried out by any suitable technique known in the art. In particular, step (a') may be carried out by sulfonic acid hydrolysis of nanocellulose.

[0123] Steps (b'), (c') and (d') may be carried out as described above for steps (b), (c) and (d), respectively.

[0124] In all embodiments relating to the synthesis process according to the invention, the steps may be carried out in the disclosed order. However, said steps may alternatively be carried out in any other order suitable for obtaining the cationic dye according to the invention. In other words, step (i) may for example be carried out before step (ii) or after step (ii). The same applies to steps (a) to (d) and / or steps (a') to (d').

[0125] For example, a method including steps (a) through (d) can be performed in the order (a), then (b), then (c), and finally (d), or the method can be performed in the order (c), then (d), then (a), and finally (b).

[0126] Similarly, a method comprising steps (a') through (d') can be performed in the order of (a'), then (b'), then (c'), and finally (d'), or in the order of (c'), then (d'), then (a'), and finally (b').

[0127] Steps (a) and (a') are optional, therefore, alternative operating sequences may be (b), (c) and (d), or (c), (d) and (b), (b'), (c') and (d'), or (c'), (d') and (b').

[0128] In the synthesis process of the invention, all references to "nanocellulose" as starting material for a step may also refer to a mixture of nanocellulose and cellulose. Indeed, in some embodiments, the first step (i), (a) or (a') of the synthesis process according to the invention is carried out directly on nanocellulose. In other embodiments, nanocellulose is formed gradually from cellulose during the steps of the synthesis process according to the invention, in particular during the oxidation step.

[0129] (dying process) A third object of the present invention is a process for dyeing at least part of a fibre material, preferably a textile fibre material, with a cationic dye according to the invention or prepared by the synthesis process according to the invention.

[0130] The fibrous material may be any material that comprises or consists of fibers, preferably fibers of a material that is negatively charged or that can be modified to carry at least one negative charge. Preferably, the surface of the fibrous material is negatively charged or can be modified to carry at least one negative charge.

[0131] The textile material can be, for example, selected from the group consisting of yarn, tissue, woven fabric, knitted fabric, and cloth.

[0132] The fibres of the textile material may be textile fibres.

[0133] The fibres of the textile material may be natural or synthetic. Among the natural fibres, mention may be made of vegetable and animal fibres. Among the vegetable fibres, mention may be made of abaca fibre, coco fibre, cotton fibre, flax fibre, hemp fibre, jute fibre, ramie fibre, sisal fibre and viscose fibre. Among the animal fibres, mention may be made of alpaca fibre, angora fibre, camel hair fibre, cashmere fibre, mohair fibre, silk fibre and wool fibre. Among the synthetic fibres, mention may be made of man-made cellulose fibre, rayon fibre, viscose fibre, polyester fibre, polyamide fibre and elastane fibre.

[0134] The fibers of the textile material can be selected from the group consisting of cellulosic and non-cellulosic fibers. The cellulosic fibers may be selected from the group consisting of cotton, flax, hemp, rayon, viscose, modal, lyocell and bamboo fibers, preferably the cellulosic fibers may be cotton fibers. The non-cellulosic fibers may be selected from the group consisting of polyester, nylon and silk fibers, preferably the non-cellulosic fibers may be polyester fibers. In a preferred embodiment, the fibers are textile fibers selected from the group consisting of cotton and polyester fibers. In one embodiment, the fibers are cotton fibers.

[0135] In some embodiments, the process for dyeing at least a portion of a fiber material according to the present invention comprises the steps of: a) contacting at least a portion of a textile material with a pretreatment agent to obtain a pretreated textile material; b) contacting said pretreated textile material obtained in step a) with at least one cationic dye according to the invention or obtained by a synthesis process according to the invention, to obtain a dyed textile material.

[0136] The inventors of the present invention have unexpectedly demonstrated that by carrying out the dyeing process according to the invention it is possible to obtain dyed textile materials having high colour fastness even after washing, whilst limiting the loss of mechanical properties of the textile, the amount of wastewater, the toxicity of the wastewater, the dyeing time and / or the energy consumption.

[0137] Furthermore, the dyeing process of the present invention provides efficient fixation of the dye onto the fiber without the use of salts or the need for post-treatment.

[0138] In some embodiments, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 70%, at least 80%, or at least 90% of the fiber material is dyed in the dyeing process according to the invention.

[0139] In a preferred embodiment, 100% of the textile material is dyed in the dyeing process according to the invention, the percentage here preferably meaning the percentage of the surface of the textile material which is provided with color in the dyeing step according to the invention.

[0140] The pretreatment agent may be any chemical agent suitable for modifying the textile material, preferably modifying the surface of the textile material. The modification of the textile material may be the creation of at least one negative charge on the textile material, preferably on the surface of the textile material.

[0141] The pretreatment agent can be selected by a person skilled in the art on the basis of his knowledge, depending on the type of fibers of the textile material and / or depending on the desired modification of the textile material.

[0142] The pretreatment agent may be selected from the group consisting of an oxidizing agent and a hydrolyzing agent.

[0143] In some embodiments, the textile fibers of the textile material include or consist of cotton fibers, and the pretreatment agent is an agent suitable for generating at least one negative charge on the surface of the cotton fibers. The negative charge may be carried by the carboxylate COO- moieties on the surface of the cotton fibers.

[0144] In such an embodiment, the pretreatment agent may be an oxidizing agent. The oxidizing agent may be selected from the group consisting of TEMPO, TEMPO in the presence of iron, potassium hydrogen persulfate (Oxone), hydrogen peroxide, hydrogen peroxide in the presence of iron, and sodium metabisulfite. Preferably, the oxidizing agent is TEMPO or potassium hydrogen persulfate (Oxone), or hydrogen peroxide in the presence of an iron salt, preferably TEMPO.

[0145] In some embodiments, the textile fibers of the textile material comprise or consist of polyester fibers, and the pretreatment agent is an agent suitable for generating at least one negative charge on the surface of the polyester fibers.

[0146] In such embodiments, the pretreatment agent may be a hydrolysis agent, which may be any suitable hydrolysis agent, such as a hydroxide, particularly sodium hydroxide.

[0147] The amount of pretreatment agent used in step a) may vary within wide limits depending on the type of pretreatment agent, the type of fiber material and / or the desired degree of modification of the fibers, in particular the desired degree of generation of a negative charge on the fibers.

[0148] In some embodiments, the pretreatment agent is used in an amount ranging from 0.2% to 200% by weight based on the weight of the textile material.

[0149] In some embodiments, the pretreatment agent is used in an amount ranging from 0.2% to 2% by weight based on the weight of the textile material. In some embodiments, the pretreatment agent is TEMPO and is used in an amount ranging from 0.2% to 2% by weight based on the weight of the textile material.

[0150] In other embodiments, the pretreatment agent is used in an amount ranging from 5% to 200% by weight based on the weight of the textile material. In some embodiments, the pretreatment agent is potassium hydrogen persulfate (Oxone) and is used in an amount ranging from 5% to 200% by weight based on the weight of the textile material. In some embodiments, the retreatment agent is potassium hydrogen persulfate (Oxone) and is used in an amount ranging from 0.01 to 2.5 molar equivalents based on the textile material.

[0151] The pretreatment step a) can be carried out under any suitable experimental conditions, such as temperature, time, nature of the solvent and / or amounts of the different reagents, in particular sodium hydroxide concentration, in order to obtain a suitably modified fibre material, also called pretreated fibre material. Preferably, said experimental conditions make it possible to prevent fibre breakage.

[0152] In some embodiments, the pretreatment step a) is carried out at a temperature in the range of 20° C. to 80° C., preferably at a temperature of about 50° C. Such temperatures are particularly suitable when the pretreatment agent is TEMPO or potassium hydrogen persulfate (Oxone).

[0153] In some embodiments, the pretreatment step a) is carried out for a time ranging from 30 minutes to 6 hours, preferably for a time of about 1 hour, which is particularly suitable when the pretreatment agent is TEMPO or potassium hydrogen persulfate (Oxone).

[0154] The particular conditions used in the pretreatment step a) of the dyeing process according to the invention make it possible to generate a negative charge on the surface of the fibres, preferably on the surface of textile fibres.

[0155] In some embodiments, in particular when the pretreatment agent used in the pretreatment step a) is potassium hydrogen persulfate (Oxone), the dyeing process further comprises a step a') between the pretreatment step a) and the dyeing step b) of rinsing the pretreated textile material with a rinsing solution. Preferably, the rinsing solution is water or an alkaline solution. The rinsing step a') serves to remove excess pretreatment agent, in particular excess potassium hydrogen persulfate (Oxone), avoiding said excess pretreatment agent reacting with the dye and / or altering the homogeneity of the coloration.

[0156] The dyeing step b) can be carried out under any suitable experimental conditions, such as temperature, time, nature of the solvent and / or amounts of the different reagents, in order to obtain a suitably dyed fibre material.

[0157] In some embodiments, the dyeing step b) is carried out at a temperature ranging from room temperature (20° C.) to 50° C. The present invention has the advantage, compared to prior dyeing methods, of being able to carry out at low temperatures while providing high quality dyeings, in particular satisfactory color strength and high fastness properties.

[0158] In some embodiments, the staining step b) is carried out for a period ranging from 15 minutes to 60 minutes.

[0159] The dyeing process according to the invention may further comprise at least one drying step c), which can be carried out between the pretreatment step a) and the dyeing step b) and / or after the dyeing step b).

[0160] Preferably, the drying step c) is carried out at a temperature below 120° C., preferably below 60° C., more preferably below 30° C. In a preferred embodiment, the drying step c) is carried out at room temperature between 15° C. and 30° C.

[0161] (Cationic dye precursor) A fourth object of the present invention is to provide a precursor of the cationic dye of the present invention, which comprises: Nanocellulose, at least one moiety susceptible to conversion to a cationic moiety, covalently attached to the nanocellulose; and at least one coloring moiety attached to the nanocellulose.

[0162] The precursor of the cationic dye of the present invention can be converted into the cationic dye of the present invention by adding at least one positive charge. For example, if the precursor of the cationic dye of the present invention consists of an amine moiety, it can be converted into the cationic dye of the present invention by quaternizing the amine, for example by subjecting the precursor to acidic conditions.

[0163] Alternatively, an amine moiety containing a cationic group can be directly incorporated into the cationic dye, for example, T of the Girard reagent.

[0164] All embodiments disclosed above with respect to the cationic dyes of the present invention and / or their synthesis process apply mutatis mutandis to the precursors of the cationic dyes according to the present invention.

[0165] (Use and dyeing of textile materials) A fifth object of the present invention is the use of the cationic dyes according to the invention or prepared by the synthesis process according to the invention in a dyeing process, in particular in at least part of the dyeing process of fibre materials, such as textile fibre materials.

[0166] A sixth object of the present invention is the dyeing of textile materials with cationic dyes according to the invention or with cationic dyes obtained by the synthesis process according to the invention. The dyed textile materials according to the invention can be obtained by the dyeing process according to the invention. EXAMPLES

[0167] The present invention is further illustrated by the following examples. Example 1: Synthesis of dyes according to the present invention

[0168] (material)

[0169] To carry out the synthesis of the cationic dyes according to the invention, the following materials were used: -Cellulose paste sheet (24cmx18cm): halbstoff-zelluseblatt 19164, -Sodium hydroxide 98+% Thermo Scientific, -NaClO2laboratorium discountcounter 99%, -NaClO 7.5%-Gaches Chimie SAS, -1,4 Butadiamine 99% Sigma Aldrich -TEMPO 2,2,6,6-Tetramethyl-1-piperidinyloxy, free radical, 98+%: Alfa Aesar -Oxone, monopersulfate Alfa Aesar, -Iron (III) nitrate anhydrate: Fisher Chemical Co. -Sodium metaperiodate: manufactured by Thermo Scientific, -Sodium borohydride 99+%: Fisher Chemical Co., -HCl ~37%: Fisher Chemical Co. -Ferrous sulfate heptahydrate 99.5% Thermo Scientific -Ferrous sulfate pentahydrate, Thermo Scientific -Manganese(II) sulfate monohydrate 99% manufactured by Thermo Scientific, - Arbocel Micronized Cellulose, Inc. -Isopropanol, manufactured by Thermo Scientific, -Girard's Reagent T 99% (Thermo Scientific) -Ethanol Denaturé 70%, MN France,

[0170] (method)

[0171] This process was carried out using cellulose as the starting material, which was gradually transformed into nanocellulose during the different steps A to E, especially during the oxidation step. XRD was performed on an Aeris Benchtop XRD Malvern Panalytical instrument.

[0172] (A) Swelling of cellulose

[0173] Cellulose sheets (1-10 g dry weight) were roughly cut with scissors and mechanically degreased in a kitchen blender for 10 min. The resulting material was dispersed in 100-500 mL of NaOH solution (0.5-2.0 mol / L) at 50-80 °C by mechanical or magnetic stirring (300-800 rpm). After 2 h, the dispersion was filtered and / or washed with deionized water (1-5 L) by centrifugation (1000-3600 RCF (relative centrifugal force) - 2-5 min at room temperature). The swollen cellulose was stored at room temperature with a solids concentration of 9.8 wt%.

[0174] (B1) Oxone oxidation)

[0175] Oxidation of swollen cellulose was carried out using Oxone (potassium hydrogen persulfate). Briefly, 1.0 g–15.0 g of swollen cellulose (dry weight) was dispersed in 50–500 mL of deionized water at 30–60 °C and 500 rpm. Then, 1–50 mL of Oxone solution (1–5 eq, relative to the mass of cellulose) was added. The reaction was allowed to continue for 1–5 h. Afterwards, the oxidized cellulose was filtered and / or washed with deionized water (1–5 L) by centrifugation (1000–3600 RCF – room temperature for 2–5 min). The oxidized cellulose was stored at room temperature with a solids concentration of 8.0 wt%.

[0176] (B2) TEMPO oxidation)

[0177] Instead of Oxone oxidation, TEMPO was also used for the oxidation of nanocellulose.

[0178] 1.0–15.0 g of swollen cellulose (dry weight) was dispersed in 50–500 mL of phosphate buffer (pH 4.5) at 50–80 °C and 500 rpm. After complete solubilization of TEMPO (1–3 min), the reaction was started by adding 20 mL of an aqueous solution containing 2.4 g of NaClO2 and 16 mL of NaClO. The reaction was continued for 2–8 h. The reaction was then stopped by adding 70% ethanol (2 eq. relative to TEMPO) and filtered or washed with deionized water (1–5 L) by centrifugation (1000–3600 RCF - 2–5 min at room temperature). The oxidized cellulose was stored at room temperature with a solids concentration of 8.0 wt%.

[0179] (C) Iron incorporation

[0180] 0.1-2.0 g of oxidized cellulose (dry weight) was dispersed in 25-100 mL of deionized water at 500 rpm for 5 min at room temperature. Then, 10 mL of an aqueous solution containing Fe2SO4.7H2O (0.01-0.1 eq) and Fe2(SO4)3 (0.01-0.1 eq) was added. After 5 min, 5 mL of NaOH (0.1-1 mol / L) was added dropwise or rapidly and stirred at room temperature for ≥ 5 min. The dispersion was then filtered or washed with deionized water (1-5 L) by centrifugation (2-5 min at 1000-3600 RCF-RT). The oxidized cellulose was stored at room temperature at a solids concentration of 8.0 wt%. A reducing agent was added in the final step to prevent aging of the iron oxide. The NaOH treatment converts the iron salts to iron oxide, as is well known to those skilled in the art. The presence of iron oxide particles is confirmed by XRPD.

[0181] (D) Periodate oxidation

[0182] 0.1-2.0 g of oxidized cellulose (with or without iron) obtained from step B1, step B2, or step C was dispersed in 25-100 mL of deionized water or acetate buffer (pH 3.5). The flask was shielded from light with aluminum foil, and 0.5-4 eq of sodium metaperiodate was added. The reaction was allowed to continue for 1-6 h. The dispersion was then filtered or washed with deionized water (1-5 L) by centrifugation (1000-3600 RCF-2-5 min, RT). The oxidized cellulose was stored at room temperature with a solids concentration of 8.0 wt%.

[0183] (E) Reductive amination

[0184] 0.1-2.0 g of periodate-oxidized cellulose (with or without iron) obtained in step D was dispersed in 25-100 mL of acetate buffer (pH 4.5) or deionized water (adjusted to pH 4.5 with hydrochloric acid solution) at 50 °C for 5 min at 500 rpm. Then, 1-75 eq (relative to aldehyde moles) of 1,4-butadiamine was added. The reaction was continued for 5-6 h. Then, the temperature was lowered to 25 °C, and 10 mL of NaBH4 solution (relative to cellulose aldehyde moles) was added dropwise, followed by reduction treatment for another 1-3 h. The dispersion was washed with deionized water (1-5 L) by filtration or centrifugation (1000-3600 RCF-RT for 2-5 min). Aminated cellulose (with or without iron) was stored at room temperature with a solids concentration of 8.0 wt%.

[0185] Example 2: Process for dyeing at least a portion of a textile material according to the invention: Model with simple cations To demonstrate the advantages of the process according to the invention, certain cationic dyes of the invention were eluted with the model metal cation Fe 2+ and Cu 2+ The dyeing process was carried out by replacing the cationic dyes according to the invention with the model metal cations. It is expected that the results will be at least comparable and that the fastnesses will be better than those obtained with the model metal cations.

[0186] (a) Pretreatment with TEMPO)

[0187] To 200 mL of sodium phosphate buffer (pH ~3.5), 1 eq of TEMPO was added along with 50-250 eq of NaClO2 and 0-50 eq of NaClO. The mixture was stirred for a few minutes until the TEMPO was dissolved. Then, 5 g of cotton fabric or yarn was immersed in the oxidizing solution under stirring at room temperature to 80°C for 1-8 hours. After the given time, the yarn or fabric was removed and washed twice with deionized water.

[0188] (b)Fe 2+ and Cu 2+ (Staining by

[0189] A 0.5g sample of yarn or a 4x4 square of oxidized cotton fabric was placed in 10 mL of 10 -3 The fabrics were immersed in an aqueous solution of CuSO4 or FeSO4 at 100 M for 10-30 min. The fabrics were removed from the metal salt solution, rinsed with water to remove excess ions, and then doped in an alkaline solution (pH=10). Finally, they were rinsed with deionized water and dried in an oven at 70°C or in air.

[0190] (c) Results of robustness tests

[0191] Pretreated with TEMPO, Fe 2+ or Cu 2+ After dyeing with, the treated fabric was subjected to a fastness test.

[0192] The tests included: - Breaking strength and elongation of individual wires according to NF EN ISO 2062:2010 - Fastness to household and industrial washing according to NF EN ISO 105 C06:2010 - Fastness to artificial light: Xenon arc lamp according to NF EN ISO 105 B02: 2014 - Sweat fastness according to NF EN ISO 105 E04: 2013 - Rubbing fastness according to NF EN ISO 105 X12:2016.

[0193] Table 1 below shows the results of the robustness tests.

[0194] [Table 1]

[0195] (d) A process involving potassium hydrogen persulfate pretreatment)

[0196] The same process was carried out, but the TEMPO oxidation step a) was replaced by potassium hydrogen persulfate (Oxone) oxidation according to the following conditions: Potassium hydrogen persulfate is cheaper than TEMPO and avoids the use of toxic chlorine compounds.

[0197] 0.1-2.5 eq of oxone was dissolved in deionized water. After a clear solution was obtained, 1 eq of cotton fabric was added to the flask and stirred at 25-50 °C for 0.5-2 h. After oxidation was complete, the fabric was taken out and rinsed several times with deionized water and, if necessary, aqueous sodium hydroxide solution to remove excess oxone. The fabric was then dried overnight or in an oven for several hours to obtain a white oxidized cotton fabric.

[0198] Staining was carried out under the same conditions as described in (b).

[0199] Similar results were obtained as with TEMPO oxidation pretreatment.

[0200] Example 3: Synthesis process of orange cationic dye according to the present invention A gel suspension containing 10 g (dry mass) of cellulose nanofibers produced by the TEMPO oxidation method (according to Example 1-B2) was added to a 1.0 L glass bottle.

[0201] The volume was adjusted to 800 mL with deionized water under magnetic stirring at 720 rpm.

[0202] After 30 min, 50 mL containing 10 g FeSO4.7H2O was added and stirred for 30 min.

[0203] 20 g of NaOH was dissolved in 50 mL of deionized water and cooled to room temperature.

[0204] The NaOH solution was added to the cellulose suspension and stirred for 30 minutes. The speed was adjusted to 740 RPM.

[0205] The suspension was then transferred to a 50 mL plastic centrifuge tube.

[0206] The formed suspension was washed with deionized water and centrifuged for 6 cycles (3220 RCF - 10 min). After adding deionized water between cycles, the solids were homogenized with an Ultraturax IKA T18 Basic for 1 min at maximum speed before a new cycle.

[0207] The solids were then suspended in 900 mL of deionized water and redispersed on a magnetic stir plate for 24 h.

[0208] The pH of the suspension was adjusted using HCl solution (~1.0 mol L -1 ) was used to adjust the pH to 3.5.

[0209] The glass flask was then completely covered with aluminum foil to protect the suspension from light.

[0210] 30 g of NaIO4 was added, and the pH of the suspension was adjusted to 3.5 using HCl solution (~1.0 mol / L) and NaOH solution (~1.0 mol / L).

[0211] The glass flask was then transferred to a 45°C water bath and connected to a magnetic stir plate with real-time temperature control.

[0212] The suspension was allowed to react under these conditions (600 RPM, 45° C.) for 3 hours.

[0213] The glass flask was then transferred to a water bath at room temperature to cool the suspension. After 5 minutes, 10 mL of ethylene glycol (99%) was added to the suspension to stop the reaction. The aluminum foil was removed.

[0214] The solids were washed with deionized water (800 mL each cycle) and centrifuged (3220 RCF - 10 min) for 6 cycles. After adding deionized water between cycles, the solids were homogenized with an Ultraturax IKA T18 Basic at maximum speed for 1 min before a new cycle.

[0215] The precipitated gel was transferred to a 1.0-neck flask and 600 mL of deionized water was added. The glass was then placed on a magnetic stirring plate (rotation adjusted to 500 RPM, 3 cm magnetic stirring bar) and allowed to redisperse for 30 min.

[0216] Then, 127 g of Girard's Reagent T was dissolved in 250 mL of deionized water.

[0217] The Girard's solution was then added to the cellulose suspension while continuing to stir. The pH of the resulting dispersion was adjusted to 3.5 using HCl solution (~1 mol / L). The glass was then transferred to a 55 °C water bath connected to a magnetic stir plate, the magnetic stirring was adjusted to 1000 RPM, and stirring was continued for 4 h 20 min with real-time control of temperature.

[0218] The glass was then transferred to a room temperature water bath to cool the suspension.

[0219] A solution of 10 g of NaBH4 dissolved in 100 mL of KOH solution (0.01 mol / L) was slowly added and reacted for 60 minutes.

[0220] The suspension was washed with deionized water and centrifuged for six cycles, then homogenized with an Ultraturax IKA T18 Basic for 1 min at maximum speed before a new cycle.

[0221] XRD analysis of the resulting material confirmed the presence of iron oxide particles (Figure 1).

[0222] Example 4: Synthesis process of black cationic dye according to the present invention

[0223] A gel suspension containing 10 g (dry mass) of cellulose nanofibers produced by the TEMPO oxidation method (according to Example 1-B2) was added to a 1.0 L glass bottle.

[0224] (Reaction 1: Oxidation with NaIO4)

[0225] Cellulose (1 g) was dispersed in 40 mL of demineralized water and homogenized by magnetic stirring at 500 rpm for 30 min. The vial was protected from light with double aluminum foil. 0.8 g of NaIO4 was added. The pH was adjusted to 3.5 with dilute hydrochloric acid. The flask was heated to 45 °C in a water bath. The reaction was left for 3 h with constant magnetic stirring at 500 RPM. The vial was transferred to a room temperature water bath and cooled for 5 min, after which the reaction was stopped by adding 2 mL of isopropanol. The suspension was transferred to a 50 mL centrifuge tube and the volume was adjusted to 50 mL with deionized water. The suspension was centrifuged at 3200 RCF for 10 min. The wash water was discarded and washed with deionized water. The centrifugation and rinsing procedures were repeated until the pH was 7 and there was no change in conductivity. The resulting gel was saved for the next reaction.

[0226] (Reaction 2: Cationization by Girard's reactive T)

[0227] 0.7 g of Girard's reagent was added and homogenized by magnetic stirring at 500 rpm for 30 min. The flask was heated in a 50 °C water bath and allowed to react for 5 h. The vial was transferred to a room temperature water bath and cooled for 5 min. The suspension was transferred to a 50 mL centrifuge tube and made up to 50 mL with deionized water. The suspension was centrifuged at 3200 RCF for 10 min. The wash water was discarded and washed with 70% ethanol. It was centrifuged again at 3200 RCF for 10 min, the wash water was discarded and washed with deionized water. The centrifugation and rinsing were repeated until the pH was 7 and there was no change in conductivity. The gel was saved for the next reaction.

[0228] (Reaction 3: Introduction of colored moieties)

[0229] The gel (1 g) obtained from the previous reaction was dispersed in 40 mL of demineralized water and homogenized by magnetic stirring at 500 rpm for 30 min under nitrogen bubbling. A solution of 0.533 g of iron II sulfate heptahydrate, 1.175 g of iron III sulfate pentahydrate and 0.081 g of manganese II sulfate monohydrate in 10 mL of demineralized water previously placed under nitrogen bubbling for 10 min was added and the reaction was homogenized by magnetic stirring at 500 rpm for 30 min under nitrogen bubbling. A solution of 2 g of NaOH in 10 mL of demineralized water previously placed under nitrogen bubbling for 10 min was added. The reaction was reacted for 30 min under nitrogen bubbling. The suspension was transferred to a 50 mL centrifuge tube and made up to 50 mL with deionized water. It was centrifuged for 10 min at 3200 RCF, the wash water was discarded and the mixture was washed with deionized water. Centrifugation and rinsing was repeated until the pH was 7 and there was no change in conductivity.

[0230] XRD analysis of the resulting material confirmed the presence of iron oxide particles (Figure 2).

[0231] Example 5: Preparation process of colored dye according to the prior art

[0232] 1 g (dry mass) of Tempo oxidized nanofibrillated cellulose was added to a 100 mL glass bottle. The volume was adjusted to 80 mL with deionized water. A 3 cm magnetic stir bar was added to the flask. The flask was placed on a magnetic stir plate and the rotation speed was adjusted to 720 RPM.

[0233] After 30 min, 5 mL containing 1 g FeSO4.7H2O was added and stirred for 30 min.

[0234] 2 g of NaOH was dissolved in 5 mL of deionized water and cooled to room temperature. The NaOH solution was added to the cellulose suspension and stirred for 30 minutes. The rotation speed was adjusted to 500 RPM.

[0235] The suspension was transferred to a 50 mL plastic centrifuge tube.

[0236] The cellulose was washed with deionized water (80 mL each cycle) and centrifuged (3220 RCF - 10 min) for 6 cycles. After adding deionized water between cycles, the solids were homogenized with an Ultraturax IKA T18 Basic at maximum speed for 1 min before a new cycle.

[0237] The solids were then suspended in 500 mL of deionized water and redispersed on a magnetic stir plate (500 RPM, using a 3 cm magnetic stir bar).

[0238] (Example 6: Step of dyeing at least a part of a textile material)

[0239] To demonstrate the advantages of the process according to the invention, a dyeing process was carried out with a specific cationic dye of the invention (Example 3). The fabric was pretreated with hydrogen peroxide and ferrous sulfate: 130 mL of 30% hydrogen peroxide, 0.02 g of ferrous sulfate (FeSO4.7H2O) and 10 mL of water were mixed and added to 20 g of fabric in a pot. The pot was heated to 50°C in a laboratory dyeing machine for 60 minutes.

[0240] After 60 minutes, the fabric was rinsed until no hydrogen peroxide residue remained on the fabric. The pretreated fabric was added to a pot along with 140 mL of dye from Example 3 or Comparative Example 5.

[0241] The pot was run in a lab dye machine at room temperature for 30 minutes, after which the fabric was removed from the pot and rinsed twice in the lab dye machine with 140 mL of water for 10 minutes each, then air-dried.

[0242] According to a variant, the staining material of Example 5 was used in combination with a treatment with polyethyleneimine (PEI) (designated 5 PEI).

[0243] (Pretreatment with PEI)

[0244] 10 g of fabric was pretreated with polyethyleneimine (PEI). 70 ml of dyebath containing 2.5 mg / mL PEI was added to the fabric in a pot. The pot was run in a laboratory dyer at room temperature for 10 minutes. After 10 minutes, two rinses were performed with 70 ml deionized water for 3 minutes each. Excess water was removed from the fabric. 70 ml of dye (with non-cationized cellulose) was added to the pot with the pretreated fabric. The pot was run in a laboratory dyer at room temperature for 30 minutes. After 30 minutes, the fabric was removed from the pot and air-dried.

[0245] The treated fabrics were subjected to fastness tests.

[0246] Table 2 below shows the results of color development and fastness testing.

[0247] [Table 2]

[0248] The coloring was characterized on the following scale: A = very strong coloring; B = strong coloring; C = average level of coloring; D = slight coloring; E = almost no coloring. The color change in the fastness test was rated on the following scale: 5 = no color change; 4 = slight color change; 3 = average level of color change; 2 = strong color change; 1 = very strong color change.

[0249] Prior art non-cationic dyes only show good resistance to disgorgement and dry rub tests due to very low initial color strength. These tests show that the dyes according to the invention are improved when used alone or in combination with PEI pretreatment compared to the prior art non-cationic dyes.

Claims

1. A cationic dye, Nanocellulose, at least one cationic moiety covalently attached to the nanocellulose; and at least one coloring moiety bound to the nanocellulose; A cationic dye comprising:

2. 2. The cationic dye of claim 1, wherein the cationic moiety is covalently attached to the nanocellulose at the C2 and / or C3 position of at least one glucose moiety of the nanocellulose.

3. 2. The cationic dye of claim 1, wherein the coloring moiety is linked to the nanocellulose at the C6 position of at least one glucose moiety of the nanocellulose by ionic and / or hydrogen bonds.

4. 2. The cationic dye of claim 1, wherein the nanocellulose is selected from the group consisting of cellulose nanofibers, cellulose nanocrystals, and any mixture thereof, preferably the nanocellulose is cellulose nanocrystals.

5. 2. The cationic dye of claim 1, wherein the at least one cationic moiety comprises a quaternized amine group, preferably a quaternized primary amine group.

6. 6. The cationic dye of claim 5, wherein the at least one cationic moiety is selected from the group consisting of a quaternized diamine moiety, a quaternized amino acid, a quaternized peptide, and a quaternized protein.

7. 10. The cationic dye of claim 1, wherein the colored moiety is a colored mineral moiety.

8. 8. The cationic dye of claim 7, wherein said colored mineral moiety is iron oxide.

9. 10. The cationic dye of claim 1, wherein the at least one cationic moiety and the at least one colored organic or mineral moiety are different moieties.

10. 10. A process for the synthesis of a cationic dye according to any one of claims 1 to 9, comprising the steps of: (i) contacting the optionally modified nanocellulose with a coloring moiety or a precursor thereof; and (ii) contacting the optionally modified nanocellulose with a cationic moiety to obtain a cationic dye.

11. 1. A process for dyeing at least a portion of a textile material, comprising: a) contacting at least a portion of said fibrous material with a pretreatment agent, preferably selected from the group consisting of an oxidizing agent and a hydrolyzing agent, to obtain a pretreated fibrous material; and b) contacting the pretreated textile material obtained in step a) with at least one cationic dye according to any one of claims 1 to 9 to obtain a dyed textile material.

12. 12. The process for dyeing at least a portion of a fibrous material according to claim 11, wherein said fibrous material is a woven fibrous material.

13. 13. The process for dyeing at least a portion of a textile material according to claim 12, wherein said textile textile material is selected from the group consisting of cotton textile materials, polyester textile materials, keratin textile materials and mixtures thereof.

14. 12. The process for dyeing at least a portion of a textile material according to claim 11, wherein the oxidizing agent is selected from the group consisting of TEMPO, TEMPO in the presence of iron, potassium hydrogen persulfate, hydrogen peroxide, hydrogen peroxide in the presence of iron, and sodium metabisulfite.

15. 12. The process for dyeing at least a portion of a fibrous material according to claim 11, wherein the dyeing step b) is carried out at a temperature ranging from 20°C to 50°C.

16. 12. A process for dyeing at least a part of a fibrous material according to claim 11, said process comprising, after step b), adding: c) drying the dyed textile material obtained in step b) at a temperature below 100°C.

Images