Oxidative process for fabrication of regenerated cellulose yarns derived from recycled waste feedstocks

Abstract

Method for the production of cellulose yarns from recycling cellulose material, wherein the method comprises the following steps: (a) dissolution of the recycling cellulose material in solution containing at least a molten ionic liquid, wherein the solution containing ionic liquid preferably comprises a protic liquid in an amount of less than 5 wt. %; (a1) adding and dissolving and / or dispersing at least one active substance or a precursor thereof in said solution; (b) adapting the conditions such that said active substances dissolved or dispersed in the solution containing molten ionic liquid or generated in situ in the solution containing molten ionic liquid act to degrade non-cellulose material initially contained in the recycling cellulose material and contained in the solution containing molten ionic liquid due to the dissolution of the recycling cellulose material, (c) extruding the molten ionic liquid cellulose material solution through at least one spinning nozzle, wherein the molten ionic liquid cellulose material solution during extrusion through at least one spinning nozzle comprises a protic liquid in an amount of less than 5 wt. %; wherein preferably step (a) at least partly takes place under an oxidative atmosphere.

Description

[0001] TITLE

[0002] OXIDATIVE PROCESS FOR FABRICATION OF REGENERATED CELLULOSE YARNS DERIVED FROM RECYCLED WASTE FEEDSTOCKS

[0003] TECHNICAL FIELD

[0004] The present invention relates to a process for conditioning recycled materials containing cellulose based on dissolution in ionic liquids and addition of active substances to degrade and remove colors and / or modify the molecular weight distribution of the cellulose polymers. The process enables direct processing of recycled materials and subsequent spinning into fibers. The process is advantageous for enabling processing of a wide range of postconsumer and post-industrial recycled articles for reuse in production of regenerated cellulose fibers.

[0005] PRIOR ART

[0006] Recycling in the textile field has become increasingly important, however its implementation and impact remains far from reaching its ultimate potential. In fact, most of the recycled textiles are not recycled to the same level again (like to like), but rather used after recycling for low level applications, e.g. for use as construction materials (insulation), et cetera (downgrading). There is a need to provide for circular methods which allow the recycling of textiles in a way which allows the recycled material to be reused at an as high as possible level, ideally for producing the same kind of textiles as used as input for the recycling.

[0007] The sustainability profile of regenerated cellulose yarns can be further improved when cellulose sources based on recycled cellulose raw materials are used. Examples include post-industrial fabrics and post-consumer apparel such as articles that contain cotton, viscose, lyocell and other forms of cellulose. Additional cellulose-containing streams (e.g. agricultural waste, lignocellulose extracted pulp, bacteria-derived cellulose, algae-derived cellulose etc.) may also be used as sources of cellulose.

[0008] Key challenges of using post-consumer articles include the following: o Wide assortment of colors due to dyestuffs in apparel items; o Impurities such as fats, oils, mineral matter picked up during the use of the articles; o Presence of non-cellulose components in the articles (e.g. synthetic blend components, sewing thread, surface treatments, zippers, buttons etc.). o Different distribution of cellulose molecular weight distribution or degree of polymerisation (DP), due to the different origin of the polymer (e.g. cotton has. a larger DP compared with the cellulose that might be found in end of life textiles like viscose) Conventional processing techniques to address the above challenges involve intensive scouring and bleaching steps that involve significant consumption of water and energy to provide clean and color-free cellulose.

[0009] Conventional approaches to remove non-cellulose components involve mechanical disassembly for macro items or selective dissolution for different fiber components.

[0010] WO-A-03029329 discloses how cellulose is dissolved in an ionic liquid without derivatization, and is regenerated in a range of structural forms without requiring the use of harmful or volatile organic solvents. Cellulose solubility and the solution properties can be controlled by the selection of the ionic liquid constituents, with small cations and halide or pseudohalide anions favoring solution.

[0011] WO-A-2004084627 discloses a regenerated cellulose-encapsulated active substance and a method for encapsulating an active substance in a regenerated cellulose matrix. The distribution of the active substance is preferably substantially homogeneous within the matrix of regenerated cellulose. The regenerated cellulose (i) has about the same molecular weight as the original cellulose from which it is prepared (ii) is substantially free of added substituent groups relative to the starting cellulose and is also substantially free of entrapped ionic liquid degradation products.

[0012] WO-A-2009062723 relates to a method for producing regenerated biopolymers in the form of carbohydrates, using a solvent system that contains the biopolymers dissolved therein. The solvent system is based on a melted ionic liquid and optionally a protic solvent or a mixture thereof. The biopolymers dissolved in the solvent system are precipitated in a coagulation medium, said medium comprising a protic coagulant or a mixture of protic coagulants. The method according to the invention is characterized in that the surface tension o of the coagulant or the mixture of coagulants is 99% to 30% of the surface tension o of water, the surface tension being measured according to ASTM D 1590-60 at a temperature of 50° C. The method according to the invention is economical and flexible and leads to advantageous products, especially in the form of staple fibers which are especially not fibrillated and have an advantageous wet to dry strength ratio.

[0013] WO-A-2007076979 proposes a solvent system for biopolymers in the form of carbohydrates which is based on a molten ionic liquid, with additives being present in the solvent system if appropriate. This solvent system comprises a protic solvent or a mixture of a plurality of protic solvents, and if the protic solvent is water alone, this is present in the solvent system in an amount of more than about 5% by weight. Carbohydrates can be incorporated into the solvent system, in particular in the form of starch, cellulose and derivatives thereof, and the solvent system can then be employed for regenerating the carbohydrates dissolved therein. In addition, a particularly advantageous method of producing the solvent system containing the carbohydrates and for producing regenerated carbohydrates, in particular in the form of regenerated cellulose fibres, is described. The invention accordingly also provides such spinning fibres which are nonfibrillating. The invention offers, in particular, economic advantages over the systems of the prior art.

[0014] CN-A-106146877 discloses a method for recovering waste textile by the aid of an ionic liquid. The method comprises steps as follows: 1) pretreatment of the waste textile: the waste textile is crushed, and pretreated waste textile is obtained; 2) water swelling and dissolution in the ionic liquid: the pretreated waste textile, the ionic liquid and water are mixed and stirred under the vacuum condition, and a liquid containing cellulose is obtained. After the waste textile is pretreated and swollen in water, the dissolution process is uniform and mild, the dissolution efficiency is high, the effect is good, and the waste textile is thoroughly separated from insoluble matters. A cellulose solution obtained through dissolution can be used for preparing a regenerated cellulose material with excellent performance, and polyester obtained through separation can serve as a polyester raw material to be recycled.

[0015] WO-A-2021234226 provides a process for the production of a cellulose filaments or films, comprising the steps of dissolving a cellulose substrate in an ionic liquid consisting of the superbase cation 7-methyl-l,5,7-triazabicyclo[4.4.0]dec-5-enium [mTBDH]+ and an anion to produce a solution forming a spinning dope, said anion being derived from an acid which is present at a stoichiometric excess to the superbase, extruding the spinning dope through a spinneret in a coagulation bath containing water to form filaments or films from the solution, withdrawing ionic liquid in an aqueous mixture with water from the coagulation bath, recovering the ionic liquid [mTBDH][OAc] from the aqueous mixture by removing water and optionally recycling the recovered ionic liquid to the dissolution step.

[0016] WO-A-2017019802 discloses methods and systems which use mixed textile feedstock, which may include post-consumer waste garments, scrap fabric and / or other textile materials as a raw feed material to produce isolated cellulose and other isolated molecules having desirable properties that can be used in the textile and apparel industries, and in other industries. A multi-stage process is provided, in which mixed textile feed material is subjected to one or more pretreatment stages, followed by at least two pulping treatments for isolating cellulose molecules and other molecular constituents, such as polyester. The isolated cellulose and polyester molecules may be used in a variety of downstream applications. In one application, isolated cellulose and polyester molecules are extruded to provide regenerated cellulose fibers and regenerated polyester fibers having desirable (and selectable) properties that are usable in various industrial applications, including textile production. SUMMARY OF THE INVENTION

[0017] It is an object of the present invention to provide an improved method for the production of cellulose yarns from recycling cellulose material.

[0018] The object of the present invention is the corresponding improved method as defined in claim 1.

[0019] Specifically, the present invention relates to a method to produce cellulose yarns from recycling cellulose material, wherein the method comprises the following steps:

[0020] (a) dissolution of the recycling cellulose material in solution containing at least a molten ionic liquid, wherein the solution containing ionic liquid preferably comprises a protic liquid in an amount of less than 5 wt. %;

[0021] (a1) adding and dissolving and / or dispersing at least one active substance or a precursor thereof in said solution;

[0022] (b) adapting the conditions (e.g. by at least one of heating, irradiation such as UV, VIS, IR, pressure change) such that said active substances dissolved or dispersed in the solution containing molten ionic liquid or generated in situ in the solution containing molten ionic liquid act to degrade non-cellulose material initially contained in the recycling cellulose material and contained in the solution containing molten ionic liquid due to the dissolution of the recycling cellulose material,

[0023] (c) extruding the molten ionic liquid cellulose material solution through at least one spinning nozzle, wherein the molten ionic liquid cellulose material solution during extrusion through at least one spinning nozzle comprises a protic liquid in an amount of less than 5 wt. %.

[0024] Surprisingly it was found that contrary to expectations a protic liquid content of the ionic liquid cellulose materials solution of less than 5 weight percent at the moment of extrusion is possible and tolerated.

[0025] Note that generally when talking about a protic liquid presence of less than a certain value, in the present context this means that there is protic liquid in the corresponding solution, so the wording is to be construed as excluding the situation where there is no protic liquid.

[0026] The solution containing at least one molten ionic liquid used for step (a) can be fresh ionic liquid or can be ionic liquid recycled from the process. As mentioned, preferably the initial molten ionic liquid for step (a) and / or the molten ionic liquid solution resulting from step (a) and / or step (a1) and / or step (b) preferably comprises a protic liquid in an amount of less than five weight percent. However, also higher percentages are possible. This provided that it is made sure that during extrusion in step (c) the protic liquid content in the ionic liquid solution is less than five weight percent.

[0027] It is to be noted that in many cases, for example when hydrogen peroxide is used, the active substances in step (b) will release water and will further increase the water content of the initial solution obtained in step (a) and / or (a1). It is possible to adjust the protic liquid content in the corresponding solution by degassing (e.g. by applying a underpressure or a vacuum), which will also carry protic liquid, in particular water, contained in the solution out of the solution. This is possible for establishing a desired protic liquid content, so for establishing the desired protic liquid content for the initial molten ionic liquid as starting material for step (a), in particular in case of using molten ionic liquid recycled from the same process, or for controlling the protic liquid content further downstream in the process. In particular it can be used for adjusting the conditions for the step (c), where a specific protic liquid content is requested.

[0028] The active substances here act to degrade non-cellulose material initially contained in the recycling cellulose material. This is in contrast to the prior art solutions, e.g. in WO-A- 2021234226 only substances are used which react with the ionic liquid.

[0029] Here, a ionic liquid bath is used for at the same time degrading non-cellulosic components and preparing for the spinning process. This is in contrast to the prior art solutions, e.g. in WO-A-2017019802 the ionic liquid is only used for an intermediate step in the preparation of a cellulose base material for spinning, and there are distinct steps of pre-treatment and dissolving, but there is no use of active substances to degrade non-cellulose material in the ionic liquid. In any case in the process as proposed here no pulping agent is normally used, while this is key in the process of WO-A-2017019802.

[0030] According to yet another preferred embodiment therefore the method includes a step before step (c), which reduces the protic liquid content in the molten ionic liquid cellulose solution to the desired level, e.g. by degassing, in particular if the protic liquid is water.

[0031] Preferably step (a) at least partly takes place under an oxidative atmosphere.

[0032] According to a first preferred embodiment, the oxidative atmosphere during step (a) is an oxygen containing atmosphere, more preferably air, preferably under atmospheric conditions.

[0033] According to yet another preferred embodiment, the oxidative atmosphere at a humidity of less than 30 g / m3, more preferably at a humidity of less than 15 g / m3, most preferably at a humidity of zero or less than 10 or less than 5 g / m3.

[0034] Preferably, the exposure to the oxidative atmosphere in step (a) takes place during a time span of at least 10 minutes, preferably at least 30 minutes, or in the range of 40-300 minutes, or in the range of 60-120 minutes.

[0035] Typically, the exposure takes place under ambient temperature conditions.

[0036] Oxidizing as chemical reaction is a function of temperature and time, kinetics is controlled also by temperature. So, the given conditions of temperature and time also equally extend to situations where an equivalent oxidizing effect is achieved for example at a lower temperature over a longer time span or at a higher temperature over a shorter time span. In fact, it was surprisingly found, contrary to expectations, that there is a beneficial effect associated with keeping the mixture of cellulose in the ionic liquid under an oxidative atmosphere leading to first break down of the cellulose. Unexpectedly neither the ionic liquid nor the cellulose nor the subsequent treatment with the active agent is negatively influenced by subjecting the ionic liquid with the cellulose to the oxidative atmosphere. The contrary is the case, the oxidative surrounding in the mixing process and dissolution process or after the dissolution process starts the oxidative degradation of the cellulose and prepares the cellulose even better for subsequent treatment with the active agent. It was thought that exposure to oxidants would be a problem for the stability of the ionic liquid, which was found not to be true.

[0037] This exposure to oxidative atmosphere can be carried out as just exposing the corresponding container with the liquid on the surface to the oxidative atmosphere, however it can also be strengthened by active stirring of the solution under this atmosphere, and even more can be forced by bubbling oxidative atmosphere through the solution to speed up the process. It is also possible to circulate the ionic liquid cellulose solution through a specific gas / liquid mixing device to increase the efficiency of the process.

[0038] In the context of this disclosure, the expressions “atmospheric pressure” and “ambient temperature” refer to the pressure and temperature conditions to that a reactor is normally exposed to, i.e. typically atmospheric pressure stands for pressures in the range of 0.8 to 1.1 bar (absolute pressure) and typically ambient temperature refers to temperatures in the range of 10 to 60° C, more typically 20 to 35°C. The gas mixture used as input for the process is preferably ambient atmospheric air, i.e. air at ambient atmospheric pressure and at ambient atmospheric temperature, which normally implies a CO2 concentration in the range of 0.03-0.06% by volume. However, also air with lower or higher CO2 concentration can be used as input for the process, e.g. with a concentration of 0.1 -0.5% by volume, so generally speaking, preferably the input CO2 concentration of the input gas mixture is in the range of 0.01-0.5% by volume. An oxidative atmosphere is a gas which contains an oxidative species, preferably oxygen. Typically, that oxidative species is present in the oxidative atmosphere in a percentage of at least 10%, preferably at least 15% or in the range of 15-99%. As mentioned, preferably the oxidative atmosphere is air, i.e. a mixture of 20-25% oxygen, supplemented by nitrogen and less than 1% of other gases. This composition, when talking about air as oxidative atmosphere, is present at least at the beginning of the exposure of the ionic liquid solution to that oxidative atmosphere, during the process due to consumption of the oxygen the oxygen content in the oxidative atmosphere may decrease. Regenerated cellulose yarns produced with ionic liquids (IL) offer appealing fiber properties and a better sustainability profile (e.g. reduced global warming potential, energy use, biodegradability) compared to fibers from synthetic polymers such as polyester and polyamide.

[0039] Conventional approaches to tackle the above key challenges for recycling would involve distinct processing steps preceding, and separate to, the preparation of a ionic liquid cellulose dope and subsequent fiber spinning.

[0040] The approach presented here provides a means of directly processing recycled cellulose- containing articles in a medium containing ionic liquid to achieve the following:

[0041] • Direct dissolution of recycled cellulose-containing articles to prepare a dope for subsequent fiber spinning;

[0042] • The dissolution firstly acts to separate out the non-soluble components e.g. synthetic fibers, mineral matter;

[0043] • Active substances dispersed in the ionic liquid (or generated in-situ) act to degrade the diverse dyestuffs associated with the cellulose, and also to degrade fatty and other organic impurities;

[0044] • Absorbents (inert and inorganic) may be homogeneously dispersed in the IL to specifically absorb impurities e.g. dyes and other unwanted ingredients. The loaded absorbents are filtered off from the cellulose-IL solution and may be reused after a suitable regeneration process.

[0045] Active substances may also be chosen in such a way to reduce the molecular weight of the cellulose polymer chains to assist in subsequent fiber spinning. Reduction of molecular weight can be achieved through exposure to short wavelength radiation e.g. UV light or photocatalysis in the presence of a catalyst.

[0046] Following dissolution of the cellulose materials in the ionic liquid and exposure to the oxidative atmosphere the active reagents (e.g. hydrogen peroxide and / or enzymes and / or catalyst salts) are added and the mixture is heated while stirring to a temperature between 40 and 120 °C and maintained at temperature for 0.5 to 24 hours duration to achieve the desired decolorization. The resulting solution may then be heated / cooled to achieve the desired target temperature and then may be used directly to the fiber spinning process.

[0047] Key advantages for the proposed method include:

[0048] 1 . Degradation of diverse dyestuffs directly and / or removal by a specific absorbents in the ionic liquid processing medium that can be directly used in subsequent fiber spinning. Enables a wide range of recycled sources to be used to generate fresh non-colored yarn.

[0049] 2. Degradation of fats, oils and other organic impurities that would otherwise impact yarn quality.

[0050] 3. Selective dissolution of cellulose and separation of insoluble components (e.g. synthetic polymer components, mineral matter).

[0051] 4. Processing directly within the ionic liquid medium used for subsequent fiber spinning avoids intensive conventional pre-processing steps that would otherwise require intensive water and energy use, further improving the sustainability profile of the recycling path. The resulting processing path requires less processing steps and enables a more direct utilization of recycled waste materials containing cellulosic components.

[0052] 5. Use of ionic liquids and fiber spinning process as described by W02007076979 and W02009062723 (the disclosure of which is included) provides a basis for achieving favorable regenerated cellulose fibers with ionic liquids that are tolerant to significant presence of protic components including water. The process advantageously enables the pre-processing active substances that provide the in-situ decolorization and impurity degrading / absorbing actions without impacting the performance of the subsequent fiber spinning. This pre-processing would otherwise not be feasible with ionic liquid systems and fiber spinning processes that are less tolerant of water content.

[0053] 6. Use of catalytic chemistry (enzymes, ozone, short wavelength radiation) vs. stoichiometrical chemistry currently used for the adjusting of cellulose degree of polymerisation (DP) (e.g. NaOH), in situ generation of H2O2 in direct proximity to the substances to bleach reduces the amount of H2O2 required vs. a dosing in the bulk phase translates in less chemicals needed.

[0054] It is one of the key features of the present invention, that it was surprisingly found that ionic liquids can be used for dissolving under oxidative atmosphere for the dissolution of the cellulose and also for the dissolution or dispersion of active substances, and can tolerate water or other protic solvents up to certain amount for the dissolution of cellulose and spinning while achieving excellent fiber properties, allowing at the same time for the introduction of catalytic components which do not increase the water or other protic solvents levels to a level that would adversely impact proper fiber spinning and consequently the fiber properties.

[0055] Degradation / absorbing of dyestuffs and organic impurities is possible as follows:

[0056] • Bleaching / decolorization of dyestuffs associated with recycled cellulose directly within the ionic liquid medium used to dissolve the cellulose components.

[0057] • Possible approaches include:

[0058] Addition of (in)organic absorbents, which will be filtered off after absorbing the impurities and can be subjected to a recycling process;

[0059] Addition of hydrogen peroxide or ozone to the ionic liquid solution of cellulose or exposed to short wavelength light or photocatalysis;

[0060] In situ generation of bleaching active substances like hydrogen peroxide through addition of enzymes to the ionic liquid solution of cellulose (e.g. cellobiose dehydrogenase for the localized generation of H2O2, but also peroxidases can take H2O2 and produce radicals able to bleach);

[0061] Addition of enzymes e.g. Laccases to decolorize and destroy impurities.

[0062] • In each case the hydrogen peroxide breaks down into residual water (ionic liquid process is tolerant to presence of remaining water), oxygen and non-colored residual degradation by-products. The residual by-products may optionally be removed directly without degradation or through use of sorbent materials after its breakdown in contact with the ionic liquid processing medium.

[0063] Reduction in molecular weight of cellulose is advantageous and possible as follows:

[0064] • The molecular weight of the cellulose polymer has a direct impact on the fiber spinning performance and also the mechanical properties of the resulting yarn;

[0065] • For some recycled cellulose raw materials (e.g. cotton-rich apparel) it may be advantageous to reduce the molecular weight distribution of the cellulose to enable improved fiber spinning performance and fiber properties;

[0066] • Homogenisation of the DP of different streams to a more constant DP cellulose stream which increases the stability of the spinning process ensuring more steady state process conditions.

[0067] • Reduction of the molecular weight may occur through action of hydrogen peroxide alone and / or with addition of other components e.g. ozone or UV light or photocatalysis selected to cleave the cellulose polymer resulting in reduced average molecular weight;

[0068] • Such additives may include enzymes and / or salts. The action of such additives in the ionic liquid medium is facilitated by the presence of water in the ionic liquid that is a feature of W02007076979 and W02009062723 (the disclosure of which is included).

[0069] The use of enzymes (e.g. Laccases) to decolorize dyestuffs is established art in detergents and laundry processing. The use of active substances like for example enzymes to achieve decolorization effect in ionic liquid processing medium is a new feature of the present invention.

[0070] The use of hydrogen peroxide in ionic liquid for oxidative conversion of lignocellulosic feedstock is described in US10724060 however the patent instructs that the action of the hydrogen peroxide is targeting degradation of lignin - degradation of color components such as dyestuffs associated with recycled cellulose materials is not addressed. US10724060 also mentions use of cellulases and / or hemicellulases however the enzyme components are specifically selected to convert the biomass into sugar components from cellulose rather than reducing the molecular weight while maintaining the cellulose polymer character. It is important to note that US10724060 contacts oxidizing substances and enzymatic substances in aqueous medium prior to a subsequent process step for the addition of ionic liquids.

[0071] WO2016087186A1 and US8445704 describe use of ionic liquids as a processing medium for chemical modification and transformation of polysaccharides however there is no use of hydrogen peroxide / ozone, short wavelength radiation, photocatalysis and / or enzymes to address colors and impurities or to address the molecular weight of the cellulose.

[0072] US11168196 describes an approach to facilitate separation of blended cellulose / polyester waste however there is no provision for actively addressing colors, impurities, and / or molecular weight within the ionic liquid used to dissolve the cellulose component.

[0073] The adaptation of the conditions according to step (b) can be carried out in different ways, for example by changing the solvent composition, by adding said active substances (alone or in a carrier solvent), by activating said active substances, by changing the temperature, the pH or by changing the pressure, or by introducing activation energy for example by irradiation, or a combination of such adaptations.

[0074] The term active substance in the context of (b) includes substances which are suitable and adapted to fulfil the function to degrade non-cellulose material initially contained in the recycling cellulose material, and examples thereof are given further below.

[0075] The recycling cellulose material is preferably selected from at least one of cellulose containing streams such as waste, recycling yarns, recycling fabrics, recycling tissue, recycling clothing.

[0076] The non-cellulose material is typically selected from at least one of non-cellulosic material, including non-cellulosic fibres (e.g. PET, PA, elastane, PE, etc. or mixtures thereof), dyestuffs, fatty and other organic impurities, including oils, waxes and detergent residues, inorganic substances such as sand or clay, water soluble and water insoluble pigments. After step (a) and before or after step (b) there can be and preferably there is a step (c) of separation of non-dissolved or non-dissolvable impurities due to the dissolution of the recycling cellulose material or of absorbents, wherein preferably this step includes at least one of filtration, decanting, centrifugation, sieving.

[0077] The ionic liquid solution preferably comprises a protic liquid, preferably water.

[0078] The active substance is preferably selected from the group of absorbents, cleaving agents, including biological cleaving agents, physical cleaving agents and chemical cleaving agents, wherein preferably absorbents are selected from the group of substances adsorbing at least one of dyestuffs, fatty impurities and other organic impurities, and wherein preferably cleaving agents are selected from the group of direct cleaving agents or activatable cleaving agents, preferably activated by irradiation of electromagnetic irradiation, wherein the cleaving agents can be selected from the group of enzymatic systems including proteases, oxidoreductases, amylases, laccases and lipases, ozone, peroxides, photocatalysts, and a combination thereof. In the examples given further below for the active substance hydrogen peroxide or an enzyme such as a peroxidase, or a combination thereof is used. However, this is just one possibility and the above-mentioned substances can fulfil the function of the active substance in a complementary and / or alternative way to this example with hydrogen peroxide. Preferably the active substance is a substance with acts as an oxidizer and has a bleaching effect or is a degradation agent, preferably an enzymatic system such as peroxidase.

[0079] Preferably, the ionic liquid from the beginning comprises or is supplemented after step (b) or after (c), if present, with a system to reduce the molecular weight of the cellulose polymer, preferably selected from the group of enzymatic systems including cellulases or hemicellulases or cellulose oxidases, in particular endoglucanases, exoglucanases peroxidases, or cleaving agents activated by irradiation of electromagnetic irradiation, or strong bases, or a combination thereof.

[0080] In step (b) the temperature is preferably increased to a range of 40-120°C, and preferably maintained at this temperature for a timespan in the range of 0.5-24 hours.

[0081] After step (b) or after step (c) the cellulose yarn can directly be spun from the cellulose dissolved in the ionic liquid.

[0082] Said molten ionic liquid further comprises a protic solvent or a mixture of several protic solvents, wherein, in the case where the protic solvent is solely water, the cellulose dissolved in the molten ionic liquid, during or downstream of step (c), are precipitated in a coagulation medium, the coagulation medium comprising a solvent which does not dissolve the cellulose and is miscible with the molten ionic liquid, wherein preferably the molten ionic liquid is comprising a cation that is formed from compounds which contain at least one five- to six membered heterocyclic ring and a protic solvent, and the process involves precipitating dissolved cellulose in the form of carbohydrates in a coagulation medium, comprising a solvent which does not dissolve the cellulose and is miscible with the molten ionic liquid, wherein said protic solvent is selected from the group consisting of

[0083] 1) water as the sole protic solvent which is present in said solution system in an amount of less than 5 wt. %,

[0084] 2) at least 0.1 wt. % based on said solution system of at least one protic solvent selected from the group consisting of alcohols such as methanol, ethanol, 1-propanol, 2-propanol 1- butanol, amylalcohol and linear and branched alcohols and higher linear and branched alcohols; and

[0085] 3) water and at least one protic solvent selected from the group consisting of alcohols, carboxylic acids or amines, such as methanol, ethanol, 1-propanol, 2-propanol and 1- butanol, amylalcohol and linear and branched alcohols and higher linear and branched alcohols.

[0086] Suitable systems acting as ionic liquids are for example those, which are described in US8163215 or in US8841441 or as in WO-A-03029329, the disclosure of which is included into this specification as concerns the ionic liquid systems.

[0087] Ionic liquids in the context of the present invention are preferably

[0088] (A) salts of the general formula (I):

[0089] [A]+n[Y]n- (I) in which n represents 1 , 2, 3 or 4, [A]+represents a quaternary ammonium cation, an oxonium cation, a sulfonium cation or a phosphonium cation and [Y]n" represents a mono-, di-, tri- or tetravalent anion; or they are (B) mixed salts of the general formulae (II)

[0090] [A1]+[A2]+[Y]n“ (Ila), wherein n=2;

[0091] [A1]+[A2][A3]+[y]n-(lib), wherein n=3; or

[0092] [A1]W[A3]+[A4]+[Y]n- (He), wherein n=4; and wherein [A1]+, [A2]+, [A3]+and [A4]+independently of one another are chosen from the groups mentioned for [A]+and [Y]n" has the meaning mentioned under (A).

[0093] Possible is e.g. the use of 1-ethyl-3-methylimidazolium chloride. This is also what is used in the examples, but this is just one possibility and the ionic liquid substances mentioned in this general section can act as such equally in a complementary (ionic liquid mixture) and / or alternative way to this example with 1-ethyl-3-methylimidazolium chloride. In particular systems based on methylimidazolium, in particular based on 1-ethyl-3-methylimidazolium, clearly fulfil the same function, so 1-ethyl-3-methylimidazolium with different anions such as fluoride, acetate, or dicyanamide, (C2Hs)(CH3)C3H3N+2 N(CN)_2, and also systems based on 1-butyl-2,3-dimethylimidazolium or 1-butyl-3,5-dimethylpyridinium, 1-butyl-3- methylimidazolium, such as 1-butyl-3,5-dimethylpyridinium bromide, 1-butyl-3- methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide or combinations thereof.

[0094] Compounds which are suitable for forming the cation [A]+ of ionic liquids are known e.g. from DE 102 02 838 A1. Such compounds can thus contain oxygen, phosphorus, sulfur or, in particular, nitrogen atoms, for example at least one nitrogen atom, preferably 1 to 10 nitrogen atoms, particularly preferably 1 to 5, very particularly preferably 1 to 3 and in particular 1 to 2 nitrogen atoms. They can optionally also contain further hetero atoms, such as oxygen, sulfur or phosphorus atoms. The nitrogen atom is a suitable carrier of the positive charge in the cation of the ionic liquid, from which a proton or an alkyl radical can then transfer to the anion in equilibrium in order to generate an electrically neutral molecule. The system of the ionic liquid may also be one based systems containing a cationic 1 ,5,7- triazabicyclo[4.4.0]dec-5-enium [TBDH]+ moiety and an anion selected from the group according to Formula a), Formula b) and Formula c), as for example described in WO2018 / 138416, which is also included into this specification as concerns ionic liquid systems.

[0095] According to yet another preferred embodiment, said molten ionic liquid comprises a protic solvent or a mixture thereof, and the method involves, during or downstream of step (c), precipitating the cellulose in a coagulation medium, a protic coagulation agent or a mixture of protic coagulation agents being present in the coagulation medium, and wherein the surface tension o of the protic coagulation agent or the mixture of protic coagulation agents is 99% to 30% of the surface tension o of water, each surface tension being measured in accordance with ASTM D 1590-60 at a temperature of 50° C, wherein preferably the protic coagulation agent is selected from 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, 1-tridecanol, 1 -tetradecanol, 2-ethyl- 1-hexanol, 1 ,2-ethanediol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,2-butanediol, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5- pentanediol, 1 ,6-hexanediol, 1 ,2,3-propanetriol, 2,2-dimethyl-1 ,5-propanediol, cyclohexanol, diethylene glycol, triethylene glycol and mixtures thereof, and wherein further preferably the coagulation medium does not contain more than 5% of carboxylic acid.

[0096] According to a further aspect of the present invention it relates to cellulose yarn produced using a method as described above.

[0097] According to yet another aspect of the present invention, it relates to the use of cellulose yarn as given above for the production of textiles, in particular of clothing.

[0098] The produced cellulose yarn may be used directly in a variety of textile processes including texturizing; twisting; covered yards (core spun yarns); knitting; weaving; seamless; circular knitting with other yarns (such as cotton, nylon, polyester, polypropylene, cellulosics, wool, silk, polyurethane); warp knitting; beaming process; staple fibers; nonwovens. The produced cellulose yarn may be used directly in a variety of textile forms including Denim; Hosiery; Intimate; Sportswear; Fashion; Shoes; Sewing threads; Upholstery; Home textiles; Industrial textiles.

[0099] Further embodiments of the invention are laid down in the dependent claims.

[0100] BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

[0102] Fig. 1 shows the schematic process steps for conventional processing of recycled cellulose into regenerated cellulose fibers compared to the invention;

[0103] Fig. 2 shows UV / Vis spectra of the measured dope solution before (empty circles) and after (5 min squares, 30 min diamonds, 60min solid circles) addition of hydrogen peroxide; in this case the 2-hour oxidation took place using N2 atmosphere;

[0104] Fig. 3 shows UV / Vis spectra of the measured dope solution before (empty circles) and after (5 min squares, 30 min diamonds, 60min solid circles) addition of hydrogen peroxide; in this case the 2-hour oxidation took place using air;

[0105] Fig. 4 shows UV / Vis spectra of the measured dope solution before (empty circles) and after (5 min squares, 30 min diamonds, 60min solid circles) addition of hydrogen peroxide; in this case the 2-hour oxidation took place using N2 atmosphere;

[0106] Fig. 5 shows UV / Vis spectra of the measured dope solution before (empty circles) and after (5 min squares, 30 min diamonds, 60min solid circles) addition of hydrogen peroxide. In this case the 2-hour oxidation took place using air.

[0107] DESCRIPTION OF PREFERRED EMBODIMENTS

[0108] Fig. 1 shows in the upper row a schematic process for conventional pre-processing of recycled cellulose materials to remove colors and impurities followed by dissolution in ionic liquid and subsequent fiber spinning. In contrast the present invention as illustrated in the lower row involves direct dissolution of the recycled cellulose in ionic liquid under an oxidative atmosphere and subsequent active agent addition enabling colors and impurities to be processed directly in the ionic liquid dope with subsequent fiber spinning. The present invention enables reduced process complexity and reductions in energy and water use compared to conventional processes.

[0109] There is a certain unclarity in the filed regarding the definition of direct dissolution cellulose spinning processes, whether the definition of Lyocell constrains to the use of the solvent N- methylmorpholine n-oxide (NMMO). Through the text here we adopt the Lyocell fiber definition according to the Ell regulation No 1007 / 2011 of 27th of September where the names of textile fibers are defined. There, Lyocell fibers are defined as a regenerated cellulose fibre obtained by dissolution, and an organic solvent (mixture of organic chemicals and water) spinning process without formation of derivatives, without limitation to NMMO. The method for the production of a regenerated fiber using a Lyocell type of process are known for a person skilled in the art an can be found in numerous publications such as recently WO2022153170A1.

[0110] Briefly the fiber spinning process normally contains the steps: a) Cutting the cellulose pulp into pieces < 4 mm (may be carried out in a high-speed mixer, ball mill, shredder and the like) b) Preparation of a pre-mix: by putting in contact the cut cellulose pulp (< 4 mm) with an organic solvent, potentially adding H2O. (Equipment selected from a group consisting of sigma mixer, reactor kneader, wiped film evaporator and the like) c) Homogenizing the pre-mix. the pre-mixing is homogenized through mechanical agitation mixing the dope for a time-period between 0 to 6 hours until a homogenous solution has been obtained. d) Removing the excess water until the final H2O content is significantly < 5%. (Equipment selected from a group consisting of sigma mixer, reactor kneader, wiped film evaporator and the like) e) The dope solution is extruded through suitable nozzles at a range of temperatures 65°C ± 30°C depending on the viscosity of the solution. The extruded solution is subjected to an air gap spinning and regenerated into the spinning bath. The spinning bath comprises of solvent in a concentration ranging between 5 to 30 wt% in water. The fibers are drawn off, optionally cut into staple fibers, washed, bleached, finished, dried.

[0111] Experimental examples, Part 1 :

[0112] Materials and Methods

[0113] Knitted fabric used in this work was made from cellulosic fibers (Viscose). The knitted fabric was dyed with a reactive dye (Robana Blue Hispasol HEGN).

[0114] UV / Vis spectra (U-2000, Hitachi, Japan) of the experimental solutions were measured in Quartz cuvettes (Hellma GmbH, Germany). Decolorization steps

[0115] The experiments involved 3 steps:

[0116] 1 . Dope preparation: Dissolution of dyed cellulose in an ionic liquid (IL)

[0117] 2. Oxidation step: Conditioning of the dope solution under different headspace gases

[0118] 3. Reaction step: Addition of hydrogen peroxide solution to bleach the cellulose

[0119] In a first step, 1 % cellulose was added into 114.76 g of each IL. The IL / cellulose mixture was heated and maintained at a temperature of 90°C in a sealable glass vial while stirring the solution for two hours, with the goal of oxidizing the cellulose, and therefore reducing the molecular weight via oxidation. As a negative control a second sample was performed replacing the air in the headspace with nitrogen. After 2 hours the absorbance was measured using UVA / is spectroscopy. After the UV / VIS measurement 3.47 g hydrogen peroxide solution (30% H2O2 in water) was added to the mixture at a temperature of 90°C while stirring. The concentrations following addition of the hydrogen peroxide solution are shown in Table 1.

[0120] Table 1. Concentration of the different species in the final spinning solution.

[0121] The dope mixture preparation features a water content less than 5% w / w. The addition of hydrogen peroxide defines the reaction start. UVA / IS measurements were taken 5 minutes, 30 minutes and 60 minutes after the reaction was started.

[0122] Example 1 : fEMIMIOAc

[0123] The spinning solution dope was prepared using the above procedure and using 1 -Ethyl-3- methylimidazolium acetate ([EMIM]OAc; CAS 143314-17-4) as the ionic liquid. UV / Vis spectra were measured directly before the addition of hydrogen peroxide and 5 minutes, 30 minutes and 60 minutes after the reaction was started.

[0124] In Fig. 2 [EMIM]OAc / cellulose mixtures were oxidized for 2 hours using N2 atmosphere.

[0125] In Fig. 3 [EMIM]OAc / cellulose mixtures were oxidized for 2 hours using air.

[0126] In all cases, the bleaching experiments were performed after the oxidation process using hydrogen peroxide solution (30%). Example 2: [EMIMIOPr

[0127] The spinning solution dope was prepared using the above procedure and using 1 -Ethyl-3- methylimidazolium propionate ([EMIM]OPr; CAS 865627-64-1) as the ionic liquid. UV / Vis spectra were measured directly before the addition of hydrogen peroxide and 5 minutes, 30 minutes and 60 minutes after the reaction was started.

[0128] In Fig. 4 [EMIM]OPr / cellulose mixtures were oxidized for 2 hours using N2 atmosphere.

[0129] In Fig. 5 [EMIM]OPr / cellulose mixtures were oxidized for 2 hours using air.

[0130] In all cases, the bleaching experiments were performed after the oxidation process using hydrogen peroxide solution (30%).

[0131] Results:

[0132] Addition of the hydrogen peroxide directly to the dope mixture of cellulose dissolved in ionic liquid results in a significant and rapid degradation of the color as measured by UV / vis absorbance at 640nm wavelength (Table 2).

[0133] The degradation of the color proceeds rapidly in both air and nitrogen headspace conditions with contact time between 5 minutes and 30 minutes producing a distinct removal of color from the cellulose mixture.

[0134] Table 2. UV / vis absorbance intensity @640nm for different ionic liquids and under either air or nitrogen headspace.

[0135] Experimental examples, Part 2:

[0136] Materials and Methods

[0137] Knitted fabric used in this work was made from cellulosic fibers (Viscose). The knitted fabric was dyed with a reactive dye (Robana Blue Hispasol HEGN).

[0138] UV / Vis spectra (U-2000, Hitachi, Japan) of the experimental solutions were measured in Quartz cuvettes (Hellma GmbH, Germany).

[0139] Hydrogen peroxide solution (5% in citrate buffer) was prepared from 30% starting solution (Carl Roth).

[0140] Horseradish peroxidase (Carl Roth; >250 ll / mg) solution was prepared with a final concentration of 0.176 g / L (in citrate buffer, pH = 5).

[0141] Decolorization steps (Enzyme)

[0142] The experiments involved 2 steps:

[0143] 1 . Dope preparation: Dissolution of dyed cellulose in an ionic liquid (IL)

[0144] 2. Reaction step: Addition of hydrogen peroxide solution and / or peroxidase solution to the cellulose / IL mixture.

[0145] In a first step, 1 % of cellulosic fibers (0.15g) were added into 14.3g of 1-Ethyl-3- methylimidazolium propionate ([EMIM]OPr; CAS 865627-64-1) as the ionic liquid. The I L / cellulose mixture was heated and maintained at a temperature of 45°C in a sealable glass vial while stirring the solution for minimum of 1 hour. Two reference samples were prepared with the only addition of 600 pL hydrogen peroxide solution or 600 pL of peroxidase solution. A test sample was prepared with addition of 600 pL hydrogen peroxide solution in combination with 600 pL of peroxidase solution. Samples were stirred for 16 hours and 65 hours followed by absorbance measurement by UV / Vis spectroscopy.

[0146] Results:

[0147] The addition of hydrogen peroxide and peroxidase in combination directly to the dope mixture of cellulose dissolved in ionic liquid results in a significant degradation of the color as measured by UV / vis absorbance at 640nm wavelength (Table 2). Enzyme activity is observed to be preserved in the IL and the color is observed to degrade more rapidly for the combination of hydrogen peroxide + peroxidase compared to the blank samples, hydrogen peroxide alone or peroxidase alone.

[0148] Table 3. UV / vis absorbance intensity @640nm for [EMIM]OPr dope solution (after 16 and 65 hours contact time) with Peroxidase only (control) relative to H2O2 only and H2O2 with peroxidase.

Claims

CLAIMS1. Method for the production of cellulose yarns from recycling cellulose material, wherein the method comprises the following steps:(a) dissolution of the recycling cellulose material in a solution containing at least a molten ionic liquid, wherein the solution containing ionic liquid with dissolved cellulose material preferably comprises a protic liquid in an amount of less than 5 wt. %;(a1) adding and dissolving and / or dispersing at least one active substance or a precursor thereof in said solution;(b) adapting the conditions such that said active substances dissolved or dispersed in the solution containing molten ionic liquid or generated in situ in the solution containing molten ionic liquid act to degrade non-cellulose material initially contained in the recycling cellulose material and contained in the solution containing molten ionic liquid due to the dissolution of the recycling cellulose material,(c) extruding the molten ionic liquid cellulose material solution through at least one spinning nozzle, wherein the molten ionic liquid cellulose material solution during extrusion through at least one spinning nozzle comprises a protic liquid in an amount of less than 5 wt. %.

2. Method according to claim 1 , wherein at least step (a) at least partly takes place under an oxidative atmosphere, wherein preferably the oxidative atmosphere during step (a) is an oxygen containing atmosphere, more preferably air, preferably under atmospheric conditions, more preferably at a humidity of less than 30 g / m3, more preferably at a humidity of less than 15 g / m3, most preferably at a humidity of zero or less than 10 or less than 5 g / m3.

3. Method according to claim 2, wherein the exposure to the oxidative atmosphere in step (a) takes place during a time span of at least 10 minutes, preferably at least 30 minutes, or in the range of 40-300 minutes, or in the range of 60-120 minutes.

4. Method according to any of the preceding claims, wherein the recycling cellulose material is selected from at least one of cellulose waste, recycling yarns, recycling fabrics, recycling tissue, recycling clothing, other cellulose streams including cellulose containing waste streams.

5. Method according to any of the preceding claims, wherein the non-cellulose material initially contained in then of non recycling cellulose material is selected from at least one of the following non-cellulosic material, including non-cellulosic fibres, dyestuffs, fatty and other organic impurities including oils, waxes and detergents and residues thereof, inorganic substances including sand, clay, water-soluble and water-insoluble pigments.

6. Method according to any of the preceding claims, wherein after step (a) and before or after step (b) there is a step (c) of separation of non-dissolved or non-dissolvable impurities due to the dissolution of the recycling cellulose material or of absorbents, wherein preferably this step includes at least one of filtration, decanting, centrifugation, sieving.

7. Method according to any of the preceding claims, wherein the solution containing ionic liquid comprises a protic liquid, preferably in the form of water, in an amount of less than 4.5%, or less than 4% or less than 3.5 wt. %.

8. Method according to any of the preceding claims, wherein the active substance is selected from the group of absorbents, cleaving agents, including biological cleaving agents, physical cleaving agents and chemical cleaving agents, wherein preferably absorbents are selected from the group of substances adsorbing at least one of dyestuffs, fatty impurities and other organic impurities, and wherein preferably cleaving agents are selected from the group of direct cleaving agents or activatable cleaving agents, preferably activated by irradiation of electromagnetic irradiation, wherein the cleaving agents can be selected from the group of enzymatic systems including proteases, amylases, laccases, oxidoreductases, and lipases, ozone, peroxides, in particular hydrogen peroxide, photocatalysts, and a combination thereof.

9. Method according to any of the preceding claims, wherein the solution containing ionic liquid from the beginning comprises or is supplemented after step (b) or after (c), if present, with a system to reduce the molecular weight of the cellulose polymer, preferably selected from the group of enzymatic systems including cellulases or hemicellulases or cellulose oxidases, in particular exoglucanases and / or endoglucanases, or cleaving agents activated by irradiation of electromagnetic irradiation, or strong bases, or a combination thereof.

10. Method according to any of the preceding claims, wherein in step (b) the temperature is increased to a range of 40-120°C, and preferably maintained at thistemperature for a timespan in the range of 0.5-24 hours.11 . Method according to any of the preceding claims, wherein after step (b) or after step (c) the cellulose yarn is directly spun from the cellulose dissolved in the solution containing ionic liquid.

12. Method according to any of the preceding claims, wherein said molten ionic liquid comprises a protic solvent or a mixture of several protic solvents, wherein the protic solvent is solely water and is present in the solution system in an amount of less than 5 wt. %, the cellulose dissolved in the molten ionic liquid are, during or downstream of step (c), precipitated in a coagulation medium, the coagulation medium comprising a solvent which does not dissolve the cellulose and is miscible with the molten ionic liquid, wherein preferably the molten ionic liquid is comprising a cation that is formed from compounds which contain at least one five-to six membered heterocyclic rings and a protic solvent, and the process involves precipitating dissolved cellulose in the form of carbohydrates in a coagulation medium, comprising a solvent which does not dissolve the cellulose and is miscible with the molten ionic liquid, and / or wherein said molten ionic liquid comprises a protic solvent or a mixture thereof, and the method, during or downstream of step (c), involves precipitating the cellulose in a coagulation medium, a protic coagulation agent or a mixture of protic coagulation agents being present in the coagulation medium, and wherein the surface tension o of the protic coagulation agent or the mixture of protic coagulation agents is 99% to 30% of the surface tension o of water, each surface tension being measured in accordance with ASTM D 1590-60 at a temperature of 50° C.

13. Method according to any of the preceding claims 10-12, wherein the protic coagulation agent is selected from 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, 1-tridecanol, 1 -tetradecanol, 2-ethyl- 1-hexanol, 1 ,2-ethanediol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,2-butanediol, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5- pentanediol, 1 ,6-hexanediol, 1 ,2,3-propanetriol, 2,2-dimethyl-1 ,5-propanediol, cyclohexanol, diethylene glycol, triethylene glycol and mixtures thereof, and wherein further preferably the coagulation medium does not contain more than 5% of carboxylic acid.

14. Cellulose yarn produced using a method according to any of the preceding claims.

15. Use of cellulose yarn according to claim 14 for the production of textiles, in particular of clothing, preferably directly in textile processes including texturizing; twisting; covered yards; knitting; weaving; seamless; circular knitting with other yarns, including cotton, nylon, polyester, polypropylene, cellulosics, wool, silk, polyurethane; warp knitting; beaming process; staple fibers; nonwovens, wherein the textiles are preferably selected from the group of Denim; Hosiery; Intimate; Sportswear; Fashion; Shoes; Sewing threads; Upholstery; Home textiles; Industrial textiles.

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