Method for producing industrial cellulose derivatives from cellulose dissolved using organic ionic solvents

Abstract

The invention relates to the production of industrial cellulose derivatives at high yield from cellulose dissolved by using sustainable and environmentally friendly organic ionic solvents.

Description

[0001] METHOD FOR PRODUCING INDUSTRIAL CELLULOSE DERIVATIVES FROM CELLULOSE DISSOLVED USING ORGANIC IONIC SOLVENTS Technical Field of the Invention

[0002] The invention relates to the production of industrial cellulose derivatives at high yield from cellulose dissolved by means of sustainable and environmentally friendly organic ionic solvents.

[0003] State of the Art

[0004] Cellulose is the most abundant renewable resource in the world and is regarded as a promising raw material for the cleaner production of functional materials. The amphiphilic structure of cellulose, its high crystallinity, and its intra- and intermolecular hydrogen bonds render it insoluble in water and in common solvents. For the functional use of cellulose, in order to form its derivatives, the cellulose compound needs to be subjected to pre-treatment using efficient solvents. The dissolution of cellulose is a worldwide problem in the manufacturing industry. In particular, the development of highly efficient and green cellulose solvents has been regarded as a key factor limiting the wide application of various industries. Common solvents used in industry for these purposes are known for their potential environmental pollution effects and low efficiencies. At present, there are two types of cellulose dissolution methods, which can be classified as “non-derivatising” or “derivatising” solvents. In derivatising systems, the dissolution of cellulose is initially achieved via the in situ formation of esters, ethers, or acetals. Another solvent system, namely the “non-derivatising” systems, achieves cellulose dissolution without chemical modification, solely by physical intermolecular interactions through the disruption of the hydrogen bond network within the cellulose. In the conventional viscose process used in the state of the art, cellulose is used to produce industrially important artificial silk and cellophane by benefiting from a derivatising system known as “viscose” (NaOH + CS2). This method was developed by Charles Frederick Cross, Edward John Bevan, and Clayton Beadle and was patented in 1892. In a typical viscose process, a cellulose xanthate derivative soluble in aqueous NaOH is formed. After shaping and regeneration of the cellulose xanthate solution in NaOH, the cellulose xanthate is converted back into cellulose [1], Theviscose process is the most frequently used cellulose dissolution method in industry. Cellulose xanthate is formed by reacting cellulose with carbon disulfide (CS2) and sodium hydroxide, and is then converted back into cellulose. However, this method has serious disadvantages. It involves difficult and lengthy chemical processes, requires many reaction steps, and thus prolongs processing times. Cellulose having a high degree of polymerisation (DP) cannot be dissolved by this method. The obtained cellulose generally has low DP levels (250-300), which limits the mechanical properties of the products. The produced cellulose ethers have a low degree of substitution (0.5), which limits their functional application areas. The process contains high amounts of toxic carbon disulfide (CS2), which leads to serious environmental risks.

[0005] In another state of the art, in a study titled production of carboxymethyl cellulose (CMC) using sugar beet cellulose, sugar beet cellulose was used in the methyl ether cellulose production method. This is a method targeting a specific cellulose source. In the chemical process, cellulose is converted into alkali cellulose with sodium hydroxide (NaOH). Carboxymethylation is carried out using sodium chloroacetate (SCA). At the end of the process, the pH is adjusted with acetic acid and impurities are removed with ethyl alcohol. The carboxymethylation process is carried out at a temperature range of 30-70 °C and over a long period of time (60-360 minutes). The obtained product is produced in powder form by drying and grinding [2], In this study, the chemical reaction requires a long duration (60-360 minutes) and has low process efficiency. It involves energy- and time-costly conditions such as high temperature and long processing time. The process contains environmentally harmful chemicals (for example, SCA and intensive alcohol usage). The use of acetic acid and ethyl alcohol poses environmental risks. The process focuses only on a specific cellulose source (sugar beet), which means limited use with other cellulose sources.

[0006] In another state of the art, in the field of methyl cellulose ether production, in patent document numbered EP1453863B1, a water-soluble cellulose ether having a flocculation temperature below 100 °C is produced by reacting activated cellulose, obtained by mercerising cellulose with methyl chloride and aqueous alkali, in the presence of a C2-C3 alkyl chloride as a reaction medium, at a reaction temperature between 65 °C and 90 °C and at a pressure between 3 and 15 bar. The weight ratio between cellulose and C1-C3 alkyl chloride is normally between 1:1 and 1:5 [3], Therequirement of high pressure for the reaction disclosed in this document increases energy consumption and equipment costs. The process requires complex equipment and poses difficulties in terms of industrial scalability. An environmentally and health-hazardous solvent such as methyl chloride is used. Carrying out the process at a temperature between 65 °C and 90 °C may increase energy costs. This situation creates a disadvantage, particularly in terms of sustainability. The weight ratio between cellulose and alkyl chloride being between 1:1 and 1:5 may constitute an economic burden, especially in cases where a high amount of alkyl chloride is required. If the chemicals used in the process and the by-products that may be formed are not properly disposed of, the risk of environmental pollution increases. In particular, toxic byproducts that may mix with water constitute a significant disadvantage in this respect. Due to the limitations and inadequacies of the solutions in the current state of the art, such as the inability to easily dissolve cellulose having a high degree of polymerisation (DP) in cellulose dissolution processes, the requirement of high pressure for the reaction, high energy consumption and equipment costs, the risk of environmental pollution arising from the improper disposal of chemicals used in the process and the by-products that may be formed, and energy- and time-costly conditions such as high temperature and long processing time, it has become necessary to make an improvement in this field.

[0007] Brief Description and Aims of the Invention

[0008] The invention relates to the production of industrial cellulose derivatives at high yield from cellulose dissolved by means of sustainable and environmentally friendly organic ionic solvents.

[0009] An aim of the invention is to develop a method in which cellulose having a high degree of polymerisation (DP) can be easily dissolved in cellulose dissolution processes. In the method that is the subject of the invention, by using the solvent system, cellulose derivatives can be synthesised with viscosity and DS (degree of substitution) values suitable for the field of use of each cellulose derivative. In the said method, cellulose ether is obtained with a wide viscosity range of 400-200,000 cP and a controllable DS degree in a wide range of 0.80-2.60. By means of the method that is the subject of the invention, cellulose having high DP values (900-2000) can be dissolved. Another aim of the invention is to develop a cellulose dissolution method in whichenvironmental concerns are prioritised. In the method that is the subject of the invention, the organic ionic solvents used operate in an environmentally friendly manner and do not produce toxic gases. The recyclability and repeated usability of the organic ionic solvents increase environmental sustainability.

[0010] Another aim of the invention is to contribute to Turkiye’s chemical exports and to reduce the current account deficit in terms of cellulose derivatives by carrying out the domestic production of cellulose derivatives known as value-added chemicals.

[0011] Description of the Figures

[0012] Figure 1. FTIR analysis of cellulose and methylated cellulose A) Cellulose B) Methyl ether cellulose

[0013] Figure 2. Carbon and oxygen numbers present in the structure of cellulose

[0014] Detailed Description of the Invention

[0015] The invention relates to the production of industrial cellulose derivatives at high yield from cellulose dissolved by means of sustainable and environmentally friendly organic ionic solvents.

[0016] The method for producing industrial cellulose derivatives at high yield from cellulose dissolved by means of sustainable and environmentally friendly organic ionic solvents, which is the subject of the invention, comprises the process steps of;

[0017] i. synthesis of organic ionic solvents,

[0018] ii. drying of the obtained liquid,

[0019] iii. dissolution of cellulose with alkali and organic ionic solvents (0 IS),

[0020] iv. formation of regenerated cellulose,

[0021] v. mercerisation of the regenerated cellulose,

[0022] vi. isolation of the mercerised product from cellulose,

[0023] vii. derivatisation of cellulose,

[0024] viii. filtration of the cellulose derivative mixture,

[0025] ix. isolation of the cellulose derivative,

[0026] x. vacuum drying of the cellulose derivative,xi. separating the product as a solid substance after removing the solvent system and volatile substances under vacuum and synthesising the cellulose derivative by crystallising, purifying, and isolating it in organic solvents.

[0027] In one embodiment of the invention, in step (i) of said method, the cations used for the synthesis of the organic ionic solvent mentioned therein are 1 -butyl-3-methylimidazolium ([Bmim]+), 1-allyl-3-methylimidazolium ([AMIM]+), 1,5-diazabicyclo[4.3.0]non-5-enium ([DBNH]+), N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium ([N221ME]+), 1-butyl-3-methylpyridinium ([BMPy]+), 1-N-butyl-3-methylimidazolium ([C4mim]+), 1-ethyl-3-methylimidazolium ([EMIm]+), zinc (Zn2+), magnesium (Mg2+), or iron (Fe3+). The anions used are tetrafluoroborate (BF4“), chloride (Cl—), acetate (OAc-), alanine (Ala-), benzoate ([OBz]’), or salicylate ([OSc]’). In one embodiment of the invention, said organic ionic solvent systems are 1 -butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), 1-allyl-3-methylimidazolium chloride ([AMIM]CI), 1 ,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]), N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium alanine ([N221ME][Ala]), 1-N-butyl-3-methylimidazolium chloride ([C4mim]+CI-), 1-butyl-3-methylpyridinium chloride ([BMPy][CI]), 1-ethyl-3-methylimidazolium benzoate ([EMIm][OBz]), 1 -ethyl-3-methylimidazolium salicylate ([EMIm][OSc]), zinc chloride monohydrate (ZnCI2H2O), zinc chloride trihydrate (ZnCI23H2O), or iron (III) chloride pentahydrate (FeCI35H2O). In one embodiment of the invention, in step (i) of said method, when the organic ionic solvent is zinc chloride monohydrate (ZnCI2H2O), zinc chloride trihydrate (ZnCI23H2O), or iron (III) chloride pentahydrate (FeCI35H2O) chloride salts, the synthesised organic ionic solutions are mixed in a temperature range of 60-90 °C and dried for a period between 1 and 5 hours in a temperature range of 60-120 °C.

[0028] In another embodiment of the invention, in step (i) of said method, a cation and an anion are used for the synthesis of the organic ionic solvent. The cation solution and the anion molecules are mixed at molar ratios of 1:1, 1:2, 1:3, 1:4, or 1:5. The mixture reacts in a temperature range of 50-100 °C for a period between 8 and 12 hours. This stage enables the strengthening of the interactions between the cation and the anion and initiates ionic liquid formation. After the mixture becomes homogeneous, it is cooled to room temperature and phase separation is allowed to occur. The liquidportion obtained by decantation is separated from the precipitated portion. The precipitated portion is washed using acetone, diethyl ether, ethyl alcohol, or mixtures thereof, and residues of the target product are extracted. The obtained organic ionic solvent is concentrated using an evaporator and, after being filtered through a ceramic filter having 50 A pores, the obtained ionic liquid is dried and isolated under 100 millibar vacuum at a temperature range of 40-60 °C for a period between 12 and 24 hours. In one embodiment of the invention, in step (i) of said method, when the organic ionic solvent is 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), for its synthesis, 1 -methylimidazole is combined with 1 -chlorobutane at a 1:1 molar ratio. The mixture is stirred at a temperature of 60-70 °C for 24 hours and allowed to react. At the end of the reaction, the ionic liquid [Bmim]CI is obtained. The obtained [Bmim]CI is mixed with a sodium tetrafluoroborate solution. The mixture is further stirred at room temperature for 8-12 hours to perform anion exchange. The formed [Bmim][BF4] phase is separated using organic acetone, and the remaining sodium chloride (NaCI) by-product is filtered. After anion exchange, the ionic liquid is dried under 100 millibar vacuum pressure and, when necessary, washed again with solvents to increase purity. In another embodiment of the invention, in step (i) of said method, when the organic ionic solvent is 1-allyl-3-methylimidazolium chloride ([AMIM]CI), freshly distilled allyl chloride is slowly added dropwise to a freshly distilled methylimidazole solution in dry acetone. The mixture is slowly heated to 55 °C under a nitrogen atmosphere and allowed to react for 8-12 hours. For purification, after the mixture is cooled to room temperature, the acetone phase is separated. Excess methylimidazole is extracted using additional acetone. The ionic liquid phase is separated and concentrated using an evaporator. After being filtered through a ceramic filter having 50 A pores, the obtained ionic liquid is dried and isolated at 40 °C for 48 hours under 100 millibar vacuum pressure.

[0029] In one embodiment of the invention, in the dissolution of cellulose in OIS described in step (iii) of said method, cellulose is gradually added into the OIS contained in a flask. When a colour change is observed in the solution or when a completely dark-coloured material is observed under a polarisation microscope, the dissolution is completed.In step (iv) of the method that is the subject of the invention, regenerated cellulose samples are prepared by pouring the cellulose solution into a coagulation bath consisting of water or ethanol in order to precipitate the cellulose, and are collected by filtration. Subsequently, the regenerated cellulose samples are thoroughly washed with deionised water and vacuum-dried overnight at 70 °C.

[0030] In the method that is the subject of the invention, characterisation of the dissolved cellulose is carried out by crystallinity / amorphousness analysis, SEM / TEM analysis, and FTIR analysis. In the crystallinity / amorphousness analysis, during the dissolution process, the crystalline structure of cellulose is disrupted, and when the supramolecular structure is completely destroyed, complete dissolution is achieved, resulting in a solution in which the polymer is molecularly dispersed. A SEM microscope is used to observe the morphological properties of cellulose before, during, and after dissolution. Dissolved cellulose has a rougher and more irregular surface. In the FTIR analysis, the samples are compressed using potassium bromide (KBr), and the infrared spectra of the OIS are obtained using an FT-IR infrared device. Since the hydrogen bonds of the dissolved cellulose are broken, in the FTIR analysis, the peaks of unsynthesised compounds observed at 3400 cm-1shift leftwards to around 3500 cm-1.

[0031] In the method that is the subject of the invention, in the mercerisation stage of the regenerated cellulose product in step (v), the washing of cellulose by alkalis is accompanied by the rearrangement of the packing of cellulose chains, known as the transition between cellulose I (native cellulose) and cellulose II (regenerated cellulose). This transition allows the formation of new intermolecular hydrogen bonds that stabilise the anti-parallel form adopted by cellulose. Such a transformation is achieved by a mercerisation process involving intracrystalline swelling of cellulose in concentrated aqueous alkali lithium hydroxide, sodium hydroxide, or potassium hydroxide (LiOH, NaOH, or KOH). Successful mercerisation should allow alkali cations to interact with cellulose to disrupt the intrachain hydrogen bonds in anhydrous cellulose I, permit sufficient water to penetrate into and swell the fibrils, and allow the space and flexibility required for cellulose chains to fold onto themselves. For mercerisation, LiOH, KOH, or NaOH alkaline solutions are selected. Approximately 8-10% NaOH solutions have the highest swelling capacity towards cellulose and partially dissolve cellulose at temperatures below 10 °C. For mercerisation, the alkaline solution must at least disruptthe hydrogen bonds or hydrophobic interactions in the cellulose crystal. Mercerisation of cellulose is carried out at both low and high temperature ranges. Accordingly, for LiOH, NaOH, or KOH, weight concentrations (8%, 10%, or 18%), temperature values (15, 25, or 70 °C), and mercerisation durations (1, 6, or 48 hours) are combined. The FTIR % transmittance values and the relevant chemical shift values in1H- and13C-NMR spectroscopy of mercerised cellulose and non-mercerised cellulose are compared, and whether the reaction is completed is evaluated.

[0032] In the method that is the subject of the invention, characterisation of the mercerisation process is carried out by SEM imaging and XRD crystal structure analyses. In SEM analyses, it is observed that the mercerisation process leads to slight changes in the external morphology of the fibres, causing them to become smoother and additionally leading to an increase in their diameters. In XRD analyses, a decrease in the crystallinity index and crystal size is determined. While the crystallinity index for mercerised cellulose remains within a narrow range such as 0.50-0.66, it varies between 0.41 and 0.95 for native cellulose. The crystal size remains approximately constant between 3.4 and 4.4 nm in mercerised celluloses, whereas variation between 2.9 and 15.4 nm is observed in native celluloses. In the X-ray diffraction diffractograms of mercerised cellulose, the diffractions shift to smaller angles. The crystallinity of regenerated or mercerised cellulose having cellulose II is lower than the crystallinity of native cellulose having cellulose I.

[0033] In the method that is the subject of the invention, a washing process is carried out with distilled water in step (vi) in order to remove unwanted by-product salts from the mercerisation products obtained.

[0034] In the method that is the subject of the invention, cellulose derivatives are obtained by alkylation of metallised cellulose. At this stage (step vii), among the cellulose derivatives, cellulose methyl ether (MC) is synthesised. By this method, cellulose derivatives such as hydroxy methyl cellulose or hydroxy ethyl cellulose ether can be synthesised.

[0035] Cellulose derivatisation described in step (vii) of the method that is the subject of the invention comprises the process steps of:

[0036] • mixing a metallised cellulose product dissolved in solution by using organic ionic liquids with iodomethane, chloromethane, or dimethyl sulfate as a methylatingagent, 1,2-propylene oxide, 2-chloroethanol (CI-CH2CH2-OH), or allyl glycidyl ether (AGE) as a hydroxypropylating agent, and sodium monochloroacetate (NaMCA) as a carboxymethylating agent at molar ratios of 1 :3, 1 :4, or 1 :5, and heating under an inert gas for 6-12 hours at a stirring speed of 200-400 rpm, • comparing the absorption bands corresponding to the hydroxyl groups of cellulose and the alkylated groups in the product by performing FTIR analysis, • determining completion of the reaction by disappearance or reduction of the hydroxyl groups (-OH),

[0037] • filtering the mixture obtained at the end of the reaction to remove unwanted residues and isolating the filtrate from the medium by crystallisation after neutralisation using hydrochloric acid (HCI), sulfuric acid (H2SO4), sodium hydroxide (NaOH), or potassium hydroxide (KOH).

[0038] In step (viii) described in said method, filtration of the cellulose derivative mixture is carried out by heating the solution obtained in step (vi) and separating the precipitated cellulose derivative by filtration.

[0039] In step (ix) described in said method, the cellulose derivative mixture is washed three times with hot water and is vacuum-dried as described in step (x). After removal of the solvent system and volatile substances under vacuum, the product is separated as a solid substance and cellulose methyl ether is synthesised by crystallisation in organic solvents, followed by purification and isolation.

[0040] In said method, characterisation of the cellulose derivatives is carried out by FTIR analysis,1H-NMR / 13C-NMR analyses, and determination of the MS (molar substitution) value. The FTIR spectra of cellulose and the produced cellulose ethers are examined. Etherification significantly alters the characteristic peaks of cellulose. Significant changes in the characteristic peaks confirm successful synthesis of the cellulose derivatives. The substitution pattern of the cellulose derivatives can be monitored by both13C and1H NMR spectroscopy. The distribution of methyl and hydroxypropyl groups among the 0-2, O-3, and 0-6 positions is determined from the relative intensities of the C-1, C-4, and C-6 signals. When the1H NMR spectrum is examined, a strong peak at 1.04-1.38 ppm indicates methyl protons. In particular, with increasing content of substituent groups, both the peak height and the area of the methyl proton peaks increase significantly. When13C NMR spectral analysis is performed for thecellulose derivatives, it can be demonstrated that the -OH groups at the C-2, C-3, and C-6 carbons of the cellulose AGU (anhydroglucose unit) are substituted by hydroxypropyl groups. The MS (molar substitution) value is the average number of hydroxyl groups substituted per repeating unit by a given substituent, which is defined by the amount of chemically modifiable hydroxyl groups in the repeating unit. Therefore, the maximum DS varies according to the structures of polysaccharides, which are limited by the total number of hydroxyl groups present in the repeating unit. For cellulose, the maximum DS is 3. Molar substitution (MS) expresses the level of substitution as moles of monomeric units per mole of AGU (within polymeric substitution). Thus, the MS value can be greater than 3. The reaction is examined through the peak intensities observed in FTIR analysis. Substituent groups replace the hydroxyl groups at the 2-, 3-, and 6-positions of cellulose. Disappearance or reduction of the OH peaks in cellulose as observed by FTIR indicates completion of the reaction. In the method developed by the invention, organic ionic solvents form new hydrogen bonds with cellulose, thereby disrupting its intra- and intermolecular hydrogen-bond network and dissolving the cellulose in this manner. The developed solvent system enables the reactions to be carried out under conditions allowing higher selectivity, without pressure-based processing, under thermal treatment at 50-80 °C. Cellulose ether is obtained with a wide viscosity range of 400-200,000 cP and a controllable DS (degree of substitution) in a wide range of 0.80-2.60. By using the solvent system, cellulose derivatives having viscosity and DS values suitable for the field of use of each cellulose derivative can be synthesised. In this way, differentiation is achieved by developing sector-specific product ranges. By means of said method, cellulose can be recycled and reused repeatedly. By means of the method that is the subject of the invention, cellulose having high DP values (900-2000) can be dissolved. In the invention, a biodegradable, sustainable, and non-toxic solvent system is developed. This method is compliant with the European Green Deal and enables production with low carbon emissions.

[0041] In the invention, organic ionic solvents are used as the cellulose dissolution method. Since this method does not produce toxic gases, the method is sustainable and compliant with the Green Deal. Organic ionic solvents (OIS) are synthesised in an easily traceable manner with a simple and innovative approach compared to conventional methods, having low viscosity (10-20 cP), high hydrogen-bond basicity(0.80-1.20), and appropriate molar ratios. The synthesised solvents dissolve cellulose by disrupting its intra- and intermolecular hydrogen-bond network and forming new hydrogen bonds. Cellulose is mercerised with LiOH, NaOH, and KOH. The cellulose product is mixed with alkylating agents and heated under an inert gas for a certain period, and at the end of the reaction the mixture is filtered to remove unwanted residues. The obtained cellulose derivatives are separated as a solid substance and are purified and isolated by crystallisation in organic solvents. In the invention, it is aimed to produce cellulose derivatives for commercial use as many environmentally friendly materials with good properties and low cost that will contribute to sustainable development worldwide. Methyl cellulose that is the subject of the invention is used in food, paper, cosmetics, construction, paint, and biomedical fields.

[0042] In the method that is the subject of the invention, TG / DSC thermal analyses, viscosity measurement, FTIR analysis, and measurement of Kamlet-Abboud-Taft parameters (KAT values) are carried out for characterisation of the organic ionic solvents. The thermogravimetric properties of the OIS are measured by loading a sample into a TG / DSC thermal analysis device. The sample is first cooled to a required temperature such as -20 °C and is then heated to 140 °C at a rate of 1 °C / min. The freezing temperature is obtained at the temperature at which the OIS solid begins to melt. The molar ratios of the OIS are selected at the molar ratio at which the melting points are the lowest. The viscosity of the OIS is calculated using a rheometer. The preparation temperature of the OIS is selected according to viscosity values, and the temperature at which OIS having low viscosity is formed is determined. FTIR spectra reveal the chemical structure and hydrogen-bond interactions between the HBD and HBA. Since hydrogen bonds are formed during the formation of the OIS, in general, in FTIR analysis of the OIS, the peaks of unsynthesised compounds observed at 3400 cm-1shift rightwards to around 3300 cm-1. At the same time, newly formed hydrogen bonds of the components in the OIS systems are observed in the analysis. In ionic liquids, as the hydrogen-bond accepting ability of anions and cations increases, the solubility of cellulose increases almost linearly. The Kamlet-Abboud-Taft parameters (KAT values), which indicate three different solvent polarities including hydrogen-bond acidity (a), hydrogen-bond basicity (|3), and dipolarity / polarisability (IT*), are used to predict this ability. H-bond OIS satisfying the AaA[3<0 criterion exhibit positive capacities for cellulose dissolution. The stronger the hydrogen-bond acceptance of theOIS, the stronger the ability of the OIS to dissolve cellulose. MCC has cellulose a>|3 values with both high a (1.31 ) and [3 (0.62). According to the AaA[3<0 criterion, potential solvents should be strongly H-bonded basic solvents having [3 values greater than those of cellulose.REFERENCES

[0043] [1] Cross, E., Bevan, C. 1892. "Improvements in Dissolving Cellulose and Allied Com pounds".8.700

[0044] [2] Camtez, 0., Herdem,H. 2019. “§eker Pancan Selulozu Kullamlarak Karboksimetil Seluloz (CMC) Uretimi”. 2019-GE-530479.

[0045] [3] Berglund, L., Sundberg,K., Johansson, K. 2007. “"Method for the Production of Methyl Cellulose Ether"”. EP1453863B1.

Claims

CLAIMS1. A method for producing industrial cellulose derivatives at high yield from cellulose dissolved by using sustainable and environmentally friendly organic ionic solvents, comprising the process steps of:i. synthesis of organic ionic solvents,ii. drying of the obtained liquid,iii. dissolution of cellulose with alkali and organic ionic solvents (OiQ), iv. formation of regenerated cellulose,v. mercerisation of the regenerated cellulose,vi. isolation of the mercerised product from cellulose,vii. derivatisation of cellulose,viii. filtration of the cellulose derivative mixture,ix. isolation of the cellulose derivative,x. vacuum drying of the cellulose derivative,xi. separating the product as a solid substance after removing the solvent system and volatile substances under vacuum and synthesising the cellulose derivative by crystallisation in organic solvents followed by purification and isolation.

2. A method according to Claim 1 , wherein the cations used for the synthesis of the organic ionic solvent mentioned in step (i) of said method are 1 -butyl-3- methylimidazolium ([Bmim]+), 1-allyl-3-methylimidazolium ([AMIM]+), 1,5- diazabicyclo[4.3.0]non-5-enium ([DBNH]+), N,N-diethyl-N-(2-methoxyethyl)-N- methylammonium ([N221ME]+), 1-butyl-3-methylpyridinium ([BMPy]+), 1-N-butyl-3- methylimidazolium ([C4mim]+), 1-ethyl-3-methylimidazolium ([EMIm]+), zinc (Zn2+), magnesium (Mg2+), or iron (Fe3+).

3. A method according to Claim 1 , wherein the anions used for the synthesis of the organic ionic solvent mentioned in step (i) of said method are tetrafluoroborate (BF4“), chloride (Cl-), acetate (OAc“), alanine (Ala-), benzoate ([OBz]’), or salicylate ([OSc]’).

4. A method according to Claim 1 , wherein said organic ionic solvent systems are 1 - butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), 1-allyl-3- methylimidazolium chloride ([AMIM]CI), 1 ,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]), N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium alanine ([N221ME][Ala]), 1-N-butyl-3-methylimidazolium chloride ([C4mim]+CI“), 1- butyl-3-methylpyridinium chloride ([BMPy][CI]), 1-ethyl-3-methylimidazolium benzoate ([EMIm][OBz]), 1-ethyl-3-methylimidazolium salicylate ([EMIm][OSc]), zinc chloride monohydrate (ZnCI2H2O), zinc chloride trihydrate (ZnCI23H2O), or iron(lll) chloride pentahydrate (FeCI35H2O).

5. A method according to Claim 1 , wherein, in step (i) of said method, when the organic ionic solvent is zinc chloride monohydrate (ZnCI2H2O), zinc chloride trihydrate (ZnCI23H2O), or iron(lll) chloride pentahydrate (FeCI35H2O), the synthesised organic ionic solutions are mixed at a temperature range of 60-90 °C and dried at a temperature range of 60-120 °C for a duration of 1 to 5 hours.

6. A method according to Claim 1 , wherein the synthesis of the organic ionic solvent described in step (i) of the method comprises the process steps of:- mixing the cation solution and anion molecules at molar ratios of 1:1, 1:2, 1:3, 1:4, or 1:5,- allowing the mixture to react at a temperature range of 50-100 °C for a period of 8 to 12 hours, cooling the mixture to room temperature after it becomes homogeneous, and waiting for phase separation to occur, - separating the liquid portion obtained by the decantation method from the precipitated portion,- washing the precipitated portion using acetone, diethyl ether, ethyl alcohol, or a mixture thereof and extracting residues of the target product, - concentrating the obtained organic ionic solvent using an evaporator, and - isolating the ionic liquid obtained after filtering the organic ionic solvent through a ceramic filter having 50 A pores by drying under 100 millibar vacuum at a temperature range of 40-60 °C for a period of 12 to 24 hours.

7. A method according to Claim 1 , wherein the synthesis of the organic ionic solvent described in step (i) of the method comprises the process steps of:- combining 1 -methylimidazole with 1 -chlorobutane at a molar ratio of 1:1 for its synthesis in the case that the organic ionic solvent is 1 -butyl-3- methylimidazolium tetrafluoroborate ([Bmim][BF4]),- stirring the mixture at a temperature of 60-70 °C for 24 hours and allowing it to react,- obtaining 1-butyl-3-methylimidazolium chloride ([Bmim]CI) ionic liquid at the end of the reaction,- mixing the obtained [Bmim]CI ionic liquid with a sodium tetrafluoroborate solution,- further stirring the mixture at room temperature for 8-12 hours to carry out anion exchange,- separating the formed [Bmim][BF4] phase using organic acetone and filtering the remaining sodium chloride (NaCI) by-product, and- drying the ionic liquid under 100 millibar vacuum pressure after anion exchange and, when necessary, washing it again with solvents to increase purity.

8. A method according to Claim 1 , wherein the synthesis of the organic ionic solvent described in step (i) of the method comprises the process steps of:- slowly adding freshly distilled allyl chloride dropwise into a freshly distilled methylimidazole solution in dry acetone in the case that the organic ionic solvent is 1-allyl-3-methylimidazolium chloride ([AMIM]CI),- slowly heating the mixture up to 55 °C under a nitrogen atmosphere and allowing it to react for 8-12 hours,- for purification, cooling the mixture to room temperature and separating the acetone phase,- extracting the excess methylimidazole using additional acetone,- separating the ionic liquid phase and concentrating it using an evaporator, and- isolating the ionic liquid obtained after filtration through a ceramic filter having 50 A pores by drying at 40 °C under 100 millibar vacuum pressure for 48 hours.

9. A method according to Claim 1, wherein, in the cellulose dissolution process described in step (iii) of the method, cellulose is slowly added into the OIS contained in a flask.

10. A method according to Claim 1, wherein, in step (iv) of the method, regenerated cellulose samples are prepared by pouring the cellulose solution into a coagulation bath consisting of water or ethanol in order to precipitate the cellulose and are collected by filtration, and subsequently the regenerated cellulose samples are thoroughly washed with deionised water and vacuum-dried overnight at 70 °C.

11. A method according to Claim 1, wherein, in the mercerisation process, cellulose is mixed with concentrated aqueous alkali lithium hydroxide, sodium hydroxide, or potassium hydroxide (LiOH, NaOH, or KOH), with weight concentrations of 8%, 10%, or 18%, temperature values of 15, 25, or 70 °C, and mercerisation durations of 1 , 6, or 48 hours.

12. A method according to Claim 1, wherein, in order to remove unwanted by-product salts from the mercerisation products, a washing process is carried out with distilled water in step (vi).

13. A method according to Claim 1, comprising the process of obtaining cellulose derivatives by alkylation of metallised cellulose.

14. A method according to Claim 1, wherein cellulose methyl ether (MC), hydroxy methyl cellulose, or hydroxy ethyl cellulose ether cellulose derivatives are synthesised from the cellulose derivatives.

15. A method according to Claim 1, wherein the cellulose derivatisation described in step (vii) comprises the process steps of:- mixing a metallised cellulose product brought into solution by using organic ionic liquids with iodomethane, chloromethane, or dimethyl sulfate as a methylating agent, 1,2-propylene oxide, 2-chloroethanol (CI-CH2CH2-OH), or allyl glycidyl ether (AGE) as a hydroxypropylating agent, and sodium monochloroacetate (NaMCA) as a carboxymethylating agent at molar ratiosof 1 :3, 1 :4, or 1 :5, and heating under an inert gas for 6-12 hours at a stirring speed of 200-400 rpm,- comparing the absorption bands corresponding to the hydroxyl groups of cellulose and the alkylated groups in the product by performing FTIR analysis,- determining completion of the reaction by disappearance or reduction of the hydroxyl groups (-OH), and- filtering the mixture obtained at the end of the reaction to remove unwanted residues and isolating the filtrate from the medium by crystallisation after neutralisation using hydrochloric acid (HCI), sulfuric acid (H2SO4), sodium hydroxide (NaOH), or potassium hydroxide (KOH).

16. A method according to Claim 1 , wherein filtration of the cellulose derivative mixture described in step (viii) is carried out by heating the solution obtained in step (vi) and separating the precipitated cellulose derivative by filtration.

17. A method according to Claim 1 , wherein the cellulose derivative mixture is washed three times with hot water in step (ix) and vacuum-dried as described in step (x), and, after removal of the solvent system and volatile substances under vacuum, the product is separated as a solid substance and cellulose methyl ether is synthesised by crystallisation in organic solvents, followed by purification and isolation.

18. A cellulose derivative obtained by a method according to any one of Claims 1-17.

19. A cellulose derivative according to Claim 18, wherein the cellulose derivative is cellulose methyl ether, hydroxy methyl cellulose, or hydroxy ethyl cellulose ether.

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