Field of the Invention

The present invention relates to cellulose-based shaped articles, such as fibers, films, beads and sponges. In particular, the invention concerns a method of manufacturing cellulose- based shaped articles by dissolving a cellulosic raw material in an organic medium to form a dope and by extruding and coagulating cellulose-based shaped articles from the dope.

The invention also relates to spinning dopes comprising cellulosic materials dissolved in an ionic liquid mixture.

Background

Certain ionic liquids (hereinafter also ILs) are known to dissolve cellulose-containing materials (e.g. wood pulps) efficiently and thus, generate so-called dopes (a.k.a. spinning solutions). Some ionic liquids also allow for spinning good-quality regenerated, lyocell- type fibers (or other shaped articles) from such dopes. Despite these positive premises, an ionic liquid-based concept has not yet reached a commercial/industrial scale. Lyocell-type fibers are, however, manufactured on an industrial scale since 1990, but by utilizing another solvent, N-methylmorpholine N-oxide (NMMO).

The properties of the cellulosic raw material and solvent in question, the dissolution conditions and subsequently, the characteristics of the generated dope form a very complex entirety. On the one hand, one might find a working combination of raw material, solvent and dissolution conditions that is feasible for industrial production. On the other hand, even though a dope can be manufactured efficiently, including good prospects of recovering the solvent for re-use, achieving also optimal visco-elastic properties of the dope for the moment of extrusion and spinning is far from self-evident. In other words, not all solvents that dissolve well, generate a dope that has the optimal conditions for regeneration into specific shapes.

The difference between what is possible in a laboratory environment (typically batch- wise production) and in an industrial environment (typically continuous production) can be quite significant. One key factor is water. In laboratory-scale experiments, water can typically be almost completely omitted. In the case of dissolution of cellulosic raw materials into a solvent, the content of water can be low in both the cellulosic raw material and in the solvent. In other words, one reaches the correct water content window for dissolution to take place very quickly in laboratory environment. On industrial-scale, on the other hand, water must be added to allow for solutions to flow using pumps and pipes. In regard to the field of this invention, the cellulosic raw material can easily contain more than 50 weight-% water, when it is mixed with the solvent. The solvent usually also contains water, because separating all the water away from the solvent can be very expensive on industrial scale. This and the fact that one is usually not limited by time in laboratory work, in turn, allows for using lower temperatures in laboratory experiments than what is feasible on industrial-scale.

Nevertheless, from an industrial point-of-view, it is still important to try to keep the process temperatures on moderate levels, not to go to too high levels. This is especially tricky in the dissolution stage. Within a dissolution department one has three parallel goals: 1) mixing the cellulosic material and solvent efficiently to form a mash (at this stage still too much water present stopping any dissolution from taking place), 2) removing enough water from the mash to reach the water content window that allows for dissolution, and 3) actual dissolution of cellulosic material into the solvent. On the one hand, increasing the temperatures in the equipment responsible for water removal and dissolution will accelerate water removal as well as accelerate dissolution, as soon as the dissolution window has been achieved. On the other hand, a too high temperatures might break-down the solvent and cause other challenges. A typical industrial processing limitation spurs from the fact that having generously of production capacity is simply too expensive, i.e. the capital expenditure needed to purchase such large equipment, in relation to the whole production process, is economically too high. In other words, one cannot apply very low water removal/ dissolution temperatures as this would take too long in respect to the available production capacity. Therefore, the limited capacity of the equipment on industrial scale pushes to increase the temperatures, which in turn puts more pressure on the property of the solvent.

NMMO was identified as a potential solvent in the 1970s, i.e. it fulfilled the basic criteria of efficient dissolution and generating a dope with good properties for regeneration as fibers. In those days NMMO was selected as the most promising from a group of alternative solvents. Cellulose-dissolving ILs were first identified around year 2000 and have since been studied in varying degrees. Today, a number of ILs have been reported to fulfil the two basic criteria mentioned above. Lately, especially a family that comprises a superbase as the cation has proven to be exceptionally interesting. Superbase-based ILs do not suffer from radical reactions (with e.g. cellulose), they dissolve pulp efficiently and create spinnable visco-elastic dopes. The first generation of this IL family was 1,5- diazabicyclo[4.3.0]non-5-ene acetate ([DBNH][OAc]). The dissolution temperature of [DBNH][OAc] in batch- wise processing is around 80-85 °C (in laboratory) and dopes made with this IL could be spun at temperatures around 70 °C (in laboratory). Importantly, [DBNH][OAc] could not be recycled efficiently due extensive cation (superbase) hydrolysis. Additional research efforts then identified 7-methyl-l,5,7-triazabicyclo[4.4.0] dec-5-enium acetate ([mTBDH][OAc]). This new superbase-based IL is more stable towards hydrolysis, but has a high melting point (>80 °C), which is not practical in industrial operations. As a consequence, the dissolution temperature for [mTBDH][OAc] must thus be at least approximately 85 °C (i.e. already somewhat higher than with [DBNH][OAc]). In practice, however, the restricted capacity of a continuous dissolution equipment (responsible for efficient water removal and the actual dissolution, both benefitting of higher temperatures) typically increases the dissolution temperature to much higher values (typically 100-130 °C at the end of the dissolution equipment). Such temperatures subject the superbase(s), including several other cations, among other, to significant hydrolysis. This presented dilemma puts pressure on finding improved process configurations and even better ILs.

The optimal temperature of spinning is a result of other factors. Here the goal is to reach the optimal visco-elastic properties of the dope, particularly at the moment of actual extrusion into the air-gap. The external parameters (equipment with specific shear forces, process conditions applied, etc.) will have an impact, but importantly also the solvent will have an impact. The angular frequency at the cross-over point (COP) of a typical dope made using paper-grade pulp and [mTBDH][OAc], at approximately 13.5 weight-% pulp, at 85 °C and less than 5 weight-% water, is below 1 rad/s. To reach a more feasible COP area (i.e. angular frequency at COP typically over 1 rad/s), the spinning temperature (the actual extrusion temperature) must be increased from 85 °C. In other words, finding the optimal visco-elastic properties with [mTBDH][OAc], with industrially relevant spinning equipment, requires increasing the spinning temperature to areas where some hydrolysis already occur (approx. 100 °C). It would thus be beneficial to find a solvent with COP at angular frequency over 1 rad/s at 85 °C, which would potentially allow to spin at 85 °C or actually decrease the spinning temperature from 85 °C for optimal visco-elastic properties. Summary of the Invention

In a first aspect, the present invention provides a method of manufacturing cellulose-based shaped articles, which comprises the steps of

- providing a cellulosic material;

- providing a solvent for the cellulosic material, said solvent having a cationic component and an anionic component, wherein the cationic component comprises two or more isomers and/or the anionic component comprises two or more anions, whereby the cationic component and the anionic component together form an ionic liquid mixture;

- dissolving said cellulosic material in the solvent at a temperature of less than 130 °C; and

- extruding the dissolved cellulosic material to form the shaped articles at a temperature of less than 110 °C.

Various embodiments of the first aspect may comprise one or more features from the following bulleted list:

• The method comprises dissolving the cellulosic material in the ionic liquid mixture at a temperature of less than 85 °C.

• The method comprises extruding the dissolved cellulosic material to form the shaped articles at a temperature of less than 80 °C.

• The cation is an organic superbase comprising at least two isomers.

• The ionic liquid mixture is or comprises an acetate salt.

• The cation is an isomeric superbase with 5-methyl-l,5,7-triaza-bicyclo[4.3.0]non- 6-enium as main component.

• The method comprises dissolving the cellulosic material in the ionic liquid mixture at a temperature of 60 to 80 °C, in particular about 65 to 75 °C.

• The cellulosic material is selected from industrial cellulosic pulps manufactured from a lignocellulosic feedstock, the feedstock typically containing cellulose and hemicellulose and optionally some lignin.

• The hemicellulose content of the cellulosic material is up to 30%, for example 16 to 20%, by total weight of the cellulosic material. • The cellulosic material is selected from dissolving pulps, paper-grade pulps and combinations thereof.

• The cellulosic material is selected from the group of cotton fibers and recycled cellulosic fibers, such as recycled textile waste.

• The cellulosic material is selected from the group of recycled textile fibers mixed with virgin cotton fibers and/or in mixture with industrial cellulosic pulp manufactured from a lignocellulosic feedstock.

• The shaped articles are in the form of fibers, filaments, films or beads, preferably in the form of fibers.

• The shaped articles are in the form of fibers suitable for textile manufacturing.

• The solution of the cellulosic material in the ionic liquid mixture, after extrusion, is contacted with a non-solvent to coagulate the shaped articles in the form of fibers, filaments, films or beads.

• The solution of the cellulosic material in the ionic liquid mixture, after extrusion, is contacted with a non-solvent to coagulate the shaped articles in the form of fibers.

• The solution of the cellulosic material in the ionic liquid mixture, after extrusion, is coagulated at a temperature of less than 80 °C, for example less than 50 °C, preferably less than 30 °C.

• The dissolved cellulosic material is extruded and taken through an air-gap and then coagulated in the non- solvent in a coagulation bath.

• The dissolved cellulosic material is coagulated into a spinning bath to form continuous filaments.

• The dissolved cellulosic material is extruded using a spinneret, typically at a pressure of 15 to 100 bar, in particular 40 to 60 bar.

• Said extruding comprises an industrial spinning process.

• Said extruding comprises dry-jet-wet spinning.

• The cationic component of the ionic liquid mixture exhibits, during the steps of dissolution of the cellulosic material and the extrusion of the cellulosic material, a degree of total hydro lyzation of less than 5 mol-%, in particular less than 1 mol-% or even less than 0.5 mol-%.

• The ionic liquid mixture is recovered and recycled.

• The ionic liquid mixture, in recovery and recycling, is concentrated by distillation, and then re-used for dissolution. • The cellulosic material is dissolved in the ionic liquid mixture to achieve a cellulosic material concentration greater than 1%, in particular greater than 5%, for example greater than 10%, such as greater than 11.5%, or greater than 12% by weight of the total solution.

• The cellulosic material is dissolved in the ionic liquid mixture to achieve a cellulosic material concentration greater than 10%, by weight of the total solution.

• The cellulosic material is dissolved to produce a dope having its cross-over point, measured at 85 °C, with less than 5 weight-% of water and at a concentration of 13.5 weight-% of the cellulosic material, at an angular frequency greater than 1 rad/s.

• The cationic component comprises two or more isomers; and the cellulosic material is dissolved in the ionic liquid mixture to achieve a cellulosic material concentration greater than 10% by weight of the total solution.

• The shaped articles are in the form of fibers having a fineness less than 10 dtex.

• The shaped articles are in the form of fibers having a fineness less than 1.8 dtex, such as 0.1 to 1.8 dtex.

The present invention also provides dopes (spinning solutions) comprising a cellulosic material dissolved, at a temperature of less than 130 °C, typically less than 100 °C, typically even below 80 °C, if batch- wise processing is allowed, in an ionic liquid mixture having a cationic component and an anionic component, the ionic liquid mixture being of a kind wherein the cationic component comprises two or more isomers or the anionic component comprises two or more anions or both the cationic and the anionic component comprise two or more isomers. A dope of the instant kind may exhibit several favorable properties compared to a dope manufactured used an ionic liquid. For instance, dopes of the present invention may have optimal processing temperatures lower than with state-of- the-art dopes and this in turn, may e.g. lower the risk of solvent decomposition.

In a second aspect, the present invention provides a dope comprising a cellulosic material dissolved at a temperature of less than 130 °C in an ionic liquid mixture having a cationic component and an anionic component, the ionic liquid mixture being of a kind wherein the cationic component comprises two or more isomers and/or the anionic component comprises two or more anions or both the cationic and the anionic component comprise two or more isomers, said dope having its cross-over point, measured at 85 °C, with less than 5 weight-% of water and at a concentration of 13.5 weight-% of the cellulosic material, at an angular frequency greater than 1 rad/s.

Various embodiments of the second aspect may comprise one or more features from the following bulleted list:

• The cation is an organic superbase comprising at least two isomers.

• The ionic liquid mixture is an acetate salt.

• The cation is an isomeric superbase with 5-methyl-l,5,7-triaza-bicyclo[4.3.0]non- 6-enium typically as the main component.

• The cellulosic material is selected from industrial cellulosic pulps manufactured from a lignocellulosic feedstock, the feedstock typically containing cellulose and hemicellulose and optionally some lignin.

• The hemicellulose content of the cellulosic material is up to 30%, for example 16 to 20%, by total weight of the cellulosic material.

More specifically, the present invention is characterized by what is stated in the characterizing part of the independent claims.

Considerable advantages are obtained. By the present invention, a reduction of 10 to 30 °C, in particular 15 to 30 °C of the dissolution temperature, or of the spinning (extrusion) temperature, or of both, may be reached compared to use of conventional ionic liquids.

In at least some of the embodiments of the present invention, hydrolysis of the cation (e.g. superbase) may be reduced or even essentially prevented. Since hydrolysis impairs the dissolution properties of the solvent, the present ionic liquid mixtures may exhibit good dissolution properties over extended periods of time.

In at least some of the embodiments of the present invention, reductions in energy consumption may be reached, due to the lower processing temperatures, as may savings in costs.

In at least some of the embodiments of the present invention, thermal damage to the polymers (cellulose) during dissolution and extrusion may be reduced. The lower temperatures of the processing may therefore open for the use of temperature-sensitive materials. Moreover, a lower temperature range may also hinder unwanted polymer-related reactions.

Spinning of dopes comprising a cellulosic raw material is typically carried out within a specified viscosity range. An indicative viscosity range can be determined by measuring the zero-shear viscosity. An increase of temperature will lower viscosity and vice versa.

At least some of the embodiments of the present invention may allow for a lowering of the temperature of the extrusion/ spinning. Thus, the solution of the cellulosic material in the ionic liquid mixture may be extruded at a temperature of less than 110 °C, for example less than 100 °C, preferably less than 80 °C.

In embodiments of the present invention, it has surprisingly been found that the viscosity levels of the present dopes, i.e. using the present ionic liquid mixtures as solvents, may be much lower than with [mTBDH][OAc], which is an ionic liquid, not an ionic liquid mixture. This, in turn, may open up for several beneficial possibilities, including the possibility to lower the spinning temperature (which increases the viscosity). Decreasing the spinning temperature may lower the risk of cation hydrolysis. Alternatively, a low viscosity may also allow for using higher concentrations of cellulose (pulp) or, respectively, cellulose (pulp) with a higher degree of polymerization.

Embodiments

Next, further features and advantages of embodiments of the present technology will be examined more closely with the aid of a detailed description.

In the present context, unless otherwise indicated, any percentages are given as weight percentages, typically calculated from the total weight of the compositions.

Any weights and weight percentages given for solid matter are based on the dry weight of the matter, unless otherwise indicated.

Similarly, any ratios given, unless otherwise indicated, are given as weight ratios. Unless otherwise stated, properties that have been experimentally measured or determined herein have been measured or determined at room temperature. Unless otherwise indicated, room temperature is 25 °C.

In the present context, the term “cellulose-based”, when used in respect to the products obtained by embodiments of the present invention, indicates that the products contain at least some cellulose, and in particular primarily consist of cellulose. However, there can be other components derived from the raw material present also. Such components are exemplified by hemicellulose(s) and lignin. Typically, at least 80 % by weight, in particular at least about 84 % by weight of the cellulose-based extrudate is formed by cellulose.

“Non-solvent” stands for a substance, which as such is incapable of dissolving cellulose at least at the conditions employed for forming the solution or dope.

“Protic” for example used in connection with “protic non-solvent” and “protic salt” has the conventional meaning of a compound, which has a hydrogen atom bound to an oxygen, in particular to an oxygen as in a hydroxyl group.

The term “superbase” stands for an organic compound whose basicity is greater than that of proton sponge, which has a conjugate pKa of 12.1. The term is used in analogous way to the term “superacid” (cf. IUPAC Gold Book, https://goldbook.iupac.org/terms). Examples of organic superbases include the following: protonated amidines, protonated guanidines, and combinations thereof.

“Unmodified cellulose fibers” stands for cellulose fibers, which have not been chemically functionalized for example by forming into cellulose derivatives, i.e. into chemical cellulose derivatives.

Generally, in the present context, fibers of the lyocell-type, i.e. unmodified cellulose fibers, are produced by, primarily, directly dissolving cellulosic raw material in an organic solvent from which the cellulose is extruded and coagulated.

In oscillatory shear rheology, loss and storage moduli of a sample are typically measured as function of angular frequency. The term “angular frequency” stands for the number of oscillations per second. The term “cross-over point” (COP) stands for the point where the loss and storage moduli curves overlap in such rheological determination.

For the determination of COP in the present context, the cellulosic material is dissolved in a solvent, in particular in an ionic liquid or an ionic liquid mixture, to produce a dope having a concentration of, for instance, 13.5 weight-% of the cellulosic material and containing less than 5 weight-% water. The COP for the dope can be determined using an oscillatory shear rheometer (e.g. a rheometer supplied by Anton Paar GmbH, Austria) at a temperature of the dope sample of 85 °C.

Typically, a dope of the present kind (i.e. made using an ionic liquid mixture), assessed as explained in the fore-going, will have a COP at an angular frequency greater than 1 rad/s, in particular greater than 2 rad/s.

Embodiments of the present technology comprise typically the basic steps of providing a cellulosic material and of providing a solvent for the cellulosic material to prepare a cellulose solution, i.e. a dope (or spinning solution).

Typically, the cellulosic material is selected from any suitable cellulosic feedstock, which is rich in cellulose.

In one embodiment, the cellulosic material is selected from industrial cellulosic pulps. Such pulps are generally manufactured from a lignocellulosic feedstock, containing cellulose and hemicellulose and optionally some lignin. Thus, the lignocellulosic feedstock can be a bleached or unbleached cellulosic pulp, bleached pulps being particularly preferred.

In an embodiment, the cellulosic material comprises or is a cellulosic pulp, typically a bleached or unbleached cellulosic pulp, preferably a bleached cellulosic pulps.

The pulp can be prepared by chemical, mechanical or chemi-mechanical pulping methods. Examples of chemical pulping methods included kraft (sulphate) pulping, sulphite pulping, polysulphide pulping, organosolv pulping, and soda pulping. Mechanical and chemimechanical pulping methods are exemplified by ground wood and pressure ground wood, refiner mechanical pulp, thermomechanical pulping and chemi-thermomechanical pulping. The pulp can be bleached for example by methods involving oxidizing bleaching chemicals, such as chlorine dioxide, ozone, peroxide and peroxo acids and combinations thereof.

In preferred embodiments, the cellulosic material comprises or consists of pulps selected from chemical pulps, where the hemicellulose content is typically up to 30%, for example 3 to 25%, in particular 5 to 22%, for example 10 to 20%, such as 12 to 18%, by total weight of the cellulosic material. The lignin content is typically on the order of 0.1 to 5%, in particular 0.1 to 2.5% by total weight of the cellulosic material.

In one embodiment, the cellulosic material is selected from dissolving pulps, paper grade pulps and combinations thereof.

The term “paper grade pulp” stands for pulp, which is suitable for manufacturing of paper and products alike (tissue paper, board, etc.). Such a pulp conventionally contains up to, but typically less than, 25%, in particular less than 20% or less than 15%, by weight of hemicellulose, calculated from the total weight of the pulp.

The term “dissolving pulp” stands for pulp which is suitable for being dissolved, typically either in a solvent or by derivatization into a solution. The dissolved pulp can then, for example, be spun into fibers or chemically reacted to produce cellulose derivatives. The dissolving pulp typically contains up to, but in particular less than 10%, by weight of hemicellulose, calculated from the total weight of the pulp.

The cellulose feedstock can be obtained from wood raw materials or from annual or perennial plants. Preferably the feedstock is obtained from wood, such as hardwood, such as birch, maple, oak, alder, aspen, poplar, eucalyptus, abaca or tropical mixed hardwood, or softwood, such as pine or spruce or combinations thereof. The cellulose feedstock can be obtained from virgin fibers, or it can comprise recycled cellulose fibers.

In one embodiment, the cellulosic material is selected from the group of cotton fibers, such as virgin cotton fibers, or recycled cotton fibers, also referred to as polycotton fibers, and recycled cellulosic fibers, such as recycled textile waste, including recycled viscose and lyocell fibers. In one embodiment, the cellulosic material is selected from the group of recycled textile fibers mixed with virgin cotton fibers and/or in mixtures with industrial cellulosic pulp manufactured from a lignocellulosic feedstock. In embodiments, the bulk, i.e. more than 50% by weight of the cellulosic material is formed by recycled fibers and less than 50% by weight of the cellulosic material is formed by virgin fibers, such as virgin cotton fibers, or industrial cellulosic pulp, such as dissolving pulp or bleached paper pulp, acting as a reinforcing component.

The cellulosic material can be treated and purified (relieved of impurities) before use. For example, the degree of polymerization can be adjusted to a predetermined value using chemicals or enzymes. In one embodiment, the pulp can be subjected to hydrolysis, such as acid or alkaline hydrolysis, after pulping.

In one embodiment, a never-dried cellulosic pulp is employed as at least a part of the cellulosic material.

In one embodiment, the cellulosic material comprises or consists of a never-dried cellulosic pulp.

In one embodiment, the cellulose pulp is free from lignin, or contains less than about 5% lignin, in particular less than about 1% lignin, by weight of the fibers.

In embodiments of the present technology, the degree of polymerization of the cellulose provided, which can be determined by the Cuoxam-DP test, is in the range from about 300 and up to even 800, for example 350 to 700, such as 400 to 660 or 550 to 650. In the Cuoxam test capillary viscosity is used for determination the average degree of polymerisation (Cuoxam-DP). Intrinsic viscosity [ |]cuoxam (ml/g) is detected by means of capillary viscometer measurement for example using an automatic capillary viscometer (SCHOTT AVS 360).

The solvent for the cellulose comprises an ionic liquid mixture having a cationic component and an anionic component. The solvent is a mixture rather than a single ionic liquid or salt. Thus, in one embodiment of the present technology, in the ionic liquid mixture the cationic component comprises two or more isomers. In another embodiment, the anionic component comprises two or more anions. In a further embodiment, an ionic liquid mixture is provided in which both the cationic and the anionic component comprise two or more isomers.

In one embodiment, the cation is an organic superbase comprising at least two isomers, for example a protic superbase comprising at least two isomers. The ionic liquid mixture is preferably selected from the group consisting of protonated amidines, protonated guanidines, and combinations thereof.

In one embodiment, the cation is an isomeric superbase with 5 -methyl- 1,5, 7-triaza- bicyclo[4.3.0]non-6-ene as main cation component.

The counter-ion of the protic superbases is typically an anion. The anion is for example selected from the group consisting of chloride, acetate, propionate, and alkylated phosphate and mixtures thereof and from a similar simple, small-molar mass ion. In one embodiment, the anion comprises two different anions selected from the fore-going anions.

The anion is capable, together with the superbase, of forming an ionic liquid mixture having a melting point lower than about 70 °C. Preferably, the ionic liquid mixture has a melting point lower than about 50 °C, in particular lower than about 30 °C. In one embodiment, the ionic liquid mixture is a liquid at room temperature.

In one embodiment, the ionic liquid mixture is an acetate salt and the cation is an isomeric superbase.

In one embodiment, the cation is an isomeric superbase with methyl- 1,5, 7-triaza- bicyclo[4.3.0]non-6-ene as main cation component, in particular the ionic liquid mixture is an acetate salt and the cation is an isomeric superbase with 5 -methyl- 1,5, 7-triaza- bicyclo[4.3.0]non-6-enium as main component. This ionic liquid mixture is also referred to by the abbreviation [mTBNH][OAc],

The isomers of [mTBNH][OAc] are shown in the following formula:

Formula I

The cellulosic material is dissolved in the solvent provided to yield a solution, a “dope”, typically containing 0.01 to 30%, generally about 0.05 to 20%, for example 0.1 to 15% cellulose, calculated from the total weight of the solution.

In a preferred embodiment, a dope is provided comprising a solution of a cellulosic material dissolved in an ionic liquid mixture selected from 5 -methyl- 1,5, 7-triaza- bicyclo[4.3.0]non-6-enium acetate in the form of an anisomer and racemic mixtures thereof, said dope having a cellulose concentration in excess of 1%, in particular greater than 5%, for example greater than 10%, such as greater than 11.5%, or greater than 12.5% by weight.

In an embodiment, a dope is provided comprising a solution of a cellulosic material dissolved in an ionic liquid mixture selected from 5-methyl-l,5,7-triaza-bicyclo[4.3.0]non- 6-enium acetate in the form of an isomer and racemic mixtures thereof.

In addition to the cellulose, the dope may also contain hemicelluloses up to 2.5% by weight of the solution, or up to about 15% or more, such as up to 20%, by weight of the dissolved material.

The water content of the dope is, in some embodiments, less than 5% or even less than 3%, by weight of the dope.

In embodiments, the cellulosic material is dissolved, de facto, in a solvent mixture of the above kind, not a pure solvent (e.g. one specific cation and one specific anion) at a temperature of less than 130 °C, typically less than 100 °C to form a dope. In one embodiment, the cellulosic material is dissolved in the ionic liquid at a temperature of less than 85 °C. In one embodiment, the cellulosic material is dissolved in a solvent, e.g. of the afore- discussed type, to produce a dope having its cross-over point (COP), measured at 85 °C, with less than 5 weight-% water in the dope and at a concentration of 13.5 weight-% of the cellulosic material in the dope, at an angular frequency greater than 1 rad/s.

The dissolved cellulosic material is extruded into an air-gap at a temperature of less than 110 °C, typically less than 100 °C, preferably less than 80 °C. Typically, the temperature is at least 50 °C.

In one embodiment, the dissolved cellulosic material is extruded through the air-gap into a coagulation bath containing a non-solvent to form the shaped articles at a temperature of less than 80 °C, for example less than 50 °C, preferably less than 30 °C. Typically, the temperature is at ambient pressure at least 10 °C.

The non-solvent is, in one embodiment, a protic antisolvent for cellulose. It can be selected from OH-group containing compounds, which are liquids at the temperature used for dispersion of the cellulose fibers. In particular the protic antisolvent is selected from the group of water, alkanol, aromatic alcohols, alkane acid, for example from water, n- or isoalcohols, such as ethanol, n-propanol, isopropanol, n-butanol, isobutanol and tert-butanol, acetic acid, and combinations and mixtures thereof. During continuous operation of the present method, the coagulation bath may also contain ionic liquid mixed with the nonsolvent. The amount of ionic liquid or ionic liquid mixture is typically not greater than 50% of the total weight of the liquid in the coagulation bath.

In one embodiment, the protic antisolvent for cellulose comprises a mixture or solution of water and an alcohol, such as ethanol, n- or isopropanol, n-, i- or tert-butanol or acetic acid. The weight ratio of water and alcohol is typically 10:90 to 90:10, for example 20:80 to 80:20, such as 40:60 to 60:40.

In the present context, the term “extrusion” stands for a processing step in which the dope is conducted or forced under pressure through a nozzle, such as through a spinneret, into an air-gap and further into a bath containing a non- solvent for the cellulosic material, where coagulation of the cellulosic material is achieved. In particular, during spinning and coagulation, products of a predetermined shape is obtained. Such products are also referred to herein as “extrudates” or “shaped articles”, their shape being determined by the equipment used during extrusion, such as nozzle and nozzle size, as well as extrusion conditions.

In the present context, the term “predetermined shape” stands, in particular, for products being provided in the form of filaments, fibers, films, beads and sponges and combinations thereof.

Filaments can be provided for example as tows of filaments and as multifilament threads. Fibers can be provided as continuous filament fibers having an infinite length as well as staple fibers, typically having a length of some 10 to 500 mm, for example 20 to 60 mm. The fineness of individual fibers is typically about 0.1 to 50 dtex, in particular 0.3 to 20 dtex, such as 0.5 to 10 dtex. Films can be provided having a thickness of 0.001 to 6 mm, for example about 0.01 to 1 mm. Beads can be provided with a largest dimension of 1 to 25 mm.

In an embodiment, the fineness of individual fibers is less than 10 dtex, such as less than 5 dtex, such as less than 2 dtex, for example less than 1.8 dtex.

In an embodiment, the fineness of individual fibers is at least 0.1 dtex, such as at least 0.3 dtex, for example at least 0.5 dtex.

When using an ionic liquid mixture of the present kind, in which, for example the anion is acetate and the cation is an isomeric superbase with 5 -methyl- 1,5, 7-triaza- bicyclo[4.3.0]non-6-ene, in at least some embodiments, the advantage is reached that the ionic liquid mixture used for dissolution of cellulose material is a liquid already at room temperature and thereby no melting of the solvent is needed at the beginning of the process, which reduces the thermal load of the process.

Thus, dissolution may be carried out in solvents which are liquids at room temperature and which, accordingly, result in dopes having a lower viscosity than conventional ionic liquids (assuming otherwise same conditions). As a result, the cellulose concentration may be increased in the dope while still maintaining a viscosity which is suitable for extrusion. Alternatively, the molecular weight of the cellulose of the raw material may be higher than the one conventionally used in production of cellulosic shaped articles. For example, it is possible in embodiments of the present technology to use cellulosic raw materials, such as cellulose pulps, having a Cuoxam-DP of 500 to 800, such as 550 to 750.

In one embodiment, the pressure at extrusion is in the range of about 30 to 200 bar, for example about 40 to 100 bar.

In one embodiment, the solution of the cellulosic material in an ionic liquid mixture is extruded using a spinneret and typically at a pressure of 15 to 100 bar, in particular at 40 to 60 bar.

The lower temperatures employed may limit thermally induced hydrolysis of the isomeric superbase. In one embodiment, the ionic liquid mixture exhibits, during the steps of dissolution of the cellulosic material and the extrusion of the cellulosic material, a degree of hydrolysis of less than 5 mol-%, in particular less than 1 mol-%, or even less than 0.5 mol-% or less than 0.1 mol-%, calculated from the superbase or superbase derivatives. In one embodiment, the cationic component of the ionic liquid mixture exhibits, during the steps of dissolution of the cellulosic material and the extrusion of the cellulosic material, a degree of hydrolysis of less than 5 mol-%, in particular less than 1 mol-%, or even less than 0.5 mol-% or less than 0.1 mol-%.

After the extrusion and coagulation step, the ionic liquid mixture may be recovered from the coagulation bath and recycled. Preferably, the ionic liquid mixture, during recovery and recycling, is concentrated by distillation, and then re-used for dissolution. Other purification methods may also be employed.

The following non-limiting example illustrates an embodiment of the present technology.

Example

Dopes were prepared from pulp and subjected to dry-jet-wet spinning at laboratory conditions.

The original pulp was commercial bleached softwood kraft pulp (NBSK) from Metsa Fibre Ltd, Finland, with the exception that it was taken out from production before the drying machine. This never-dried pulp was subjected to acid hydrolysis for viscosity adjustment. In the acid hydrolysis the pulp was treated with diluted sulphuric acid at elevated temperatures in order to decrease the intrinsic viscosity to approx. 450 ml/g. The pulp was not dried after this treatment.

A dope (spinning solution) was prepared by mixing the wet pulp with an aqueous ionic liquid mixture ([mTBNH][OAc]) in a relation that corresponds to 13 weight-% pulp consistency after removing most of the water present. The water evaporation and pulp dissolution was performed using a Netzsch PML 40 mixing device. The temperature was set at 85 °C and the pressure at 20 mbar. The full dissolution of the pulp was verified optically with light and polarizing microscope.

The spinning was performed successfully in a dry-jet-wet spinning device at 70 °C (set point, dope temperature 67 °C). The titre of the obtained fibre was approximately 1.7 dtex. The spinning was first attempted at conditions optimised for dopes made using ionic liquid [mTBDH][OAc], i.e. 100 °C set point, 97 °C dope temperature, but the spinning was unsuccessful due to a too low viscosity and a too high angular frequency at COP. Lowering the spinning temperature stabilized the spinning as the viscosity increases and angular frequency of COP decreases as a function of decreasing temperature.

The process conditions and dope properties of good quality spinning for [mTBNH][OAc] are listed in the below table. The table also contains, for comparative reasons, corresponding data on the same equipment for dopes prepared using [mTBDH][OAc], It is to be noted that these are not universal values, but distinctive for the laboratory equipment.

Table. Properties of dopes made using [mTBNH] [OAc] and [mTBDH] [OAc] as solvents Abbreviations

IL ionic liquid

NMMO N-methylmorpholine N-oxide [DBNH][OAc] 1 ,5 -diazabicyclo [4.3 ,0]non-5 -ene acetate

[mTBDH][OAc] 7-methyl-l,5,7-triazabicyclo[4.4.0] dec-5-enium acetate

[mTBNH][OAc] 5 -methyl- 1 ,5 ,7-triaza-bicyclo [4.3.0]non-6-enium acetate

COP cross-over point