WO2016135385A1

WO2016135385A1 - Process for producing shaped articles based on cellulose

Info

Publication number: WO2016135385A1
Application number: PCT/FI2016/050117
Authority: WO
Inventors: Minna HAKALAHTI; Tiia-Maria Tenhunen; Tuomas HÄNNINEN; Jaakko Pere
Original assignee: Teknologian Tutkimuskeskus Vtt Oy
Priority date: 2015-02-27
Filing date: 2016-02-24
Publication date: 2016-09-01

Abstract

The present invention relates to a process for producing shaped articles, where the process comprises the steps, where cellulosic material is suspended in a DES comprising choline chloride and a hydrogen bond donor selected from urea, malonic acid, oxalic acid, phenylacetic acid and glycerol, whereby a dispersion is obtained, and shaped articles are formed from the dispersion. The present invention also relates to shaped articles obtainable by the process and to their uses.

Description

PROCESS FOR PRODUCING SHAPED ARTICLES BASED ON CELLULOSE

FIELD OF THE INVENTION

The present invention relates to a process for producing shaped articles based on cellulose. More particularly, the present invention relates to a process for producing shaped articles from cellulosic material dispersed in deep eutectic solvent. The invention also concerns shaped articles obtained by the process, and their use. BACKGROUND OF THE INVENTION

As the most abundant polymer on earth, cellulose has played an important role in textile and filament production for hundreds of years. The long fibres of natural cotton are ideal for forming strong filaments and yarns, and cotton is traditionally utilized widely in textiles. However, the use of cotton requires a lot of water, pesticides and fertilizers in the production phase.

Wood-based fabrics have been suggested as an ecologically friendly alternative for cotton. Currently, wood-based cellulose is generally formed as a filament made of dissolved and regenerated cellulose. This is also the process that the manmade cellulose-based textile fibres e.g. viscose, modal and lyocell are based on today. In the viscose process harmful or toxic chemicals are used, which also have negative effect on the properties of cellulose. Further, most of the regenerated cellulose processes are considered unsustainable, and as the crystalline form of cellulose changes in the process, the material properties change drastically as well. Cellulose I crystalline form of native cellulose has unique tensile strength of 7.5-7.7 GPa, which is lost if fibres are dissolved and regenerated, due to the change of the crystalline form.

Traditional paper yarns require paper making process prior to yarn spinning. Short wood fibres do not naturally form strong filaments and they have a tendency to disintegrate in water.

Ionic solvents have been proposed for dissolving cellulosic materials originating from natural sources. However, they are often harmful or toxic and very expensive for industrial use on a larger scale.

Deep eutectic solvents (DES) are a type of ionic solvents which refer to eutectic mixtures that are liquid at or below room temperature. Deep eutectic solvents are currently applied in large scale applications, such as electro winning of metals, electro polishing of stainless steel, as well as solvents in organic reactions.

WO 2012/145522 A2 describes DES systems for dissolving cellulose. DES comprising choline chloride and urea was tested for dissolving Avicel^® (cellulose), no suspension was formed and no dissolution was noticed.

Despite the ongoing research and development there is a need for an inexpensive and sustainable process for producing shaped articles based on cellulose. There is also a need for inexpensive, environmentally acceptable cellulosic filaments for replacing filaments manufactured from cotton.

SUMMARY OF THE INVENTION

It was surprisingly found that a simple, non-toxic process can be utilized for producing shaped articles based on non-dissolved cellulose, where the crystalline form of cellulose is maintained.

An object of the invention is to provide to a process for producing shaped articles based on cellulose. Another object of the invention is to provide a process for producing cellulosic filaments without dissolving cellulose fibres.

Another object of the invention is to provide shaped articles based on cellulose obtainable by said process.

A still another object of the invention is to provide uses of said shaped articles based on cellulose.

Thus the present invention relates to new a process for producing shaped articles based on cellulose.

The process for producing shaped articles comprises the steps, where 0.5 -20 wt% of cellulosic material, calculated from the total weight of the dispersion, is dispersed in a DES comprising choline chloride and a hydrogen bond donor selected from urea, malonic acid, oxalic acid, phenylacetic acid and glycerol, at a temperature from 10- 280°C, whereby a dispersion is obtained, and shaped articles are formed from the dispersion.

The present invention also relates to shaped articles comprising cellulose fibres comprising cellulose of crystalline form I.

The present invention also relates to the use of shaped articles based on cellulose in yarns, ropes, textiles, cloths, nonwovens, membranes, films, filters, isolation materials and composite structures. Characteristic features of the invention are presented in the appended claims.

DEFINITIONS

Deep eutectic solvents (DES) are a sub-class of ionic liquids with special properties. DES is composed of a mixture of two or more components and said mixture forms a eutectic with a melting point much lower than any of the individual components. The deep eutectic solvent useful in the present invention consists of hydrogen bond donor and hydrogen bond acceptor.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates one embodiment of the process of the invention.

Figure 2 shows NMR spectrum of bleached softwood pulp before and after dispersing in ChCI/urea.

Figure 3 illustrates SEM of filaments obtained by the process.

Figure 4 illustrates count related tenacity (a) and strain (b) measured from dry and wet filament samples.

Figure 5 shows stress/strain curves of the sample containing 5% of PAA.

Figure 6 presents FT-IR Spectra of unused and recycled ChCI/urea.

DETAILED DESCRIPTION OF THE INVENTION

The inventors of the present invention have developed a new, simple, non-toxic and non-dissolving process for producing shaped articles based on cellulose from a wide selection of different cellulosic materials, such as pulps. The approach is based on the usage of DES as swelling agent of the cellulosic fibres and dispersing agent for obtaining a dispersion suitable for forming shaped articles, such as dispersion for filament spinning process. There is no dissolution or regeneration, therefore the original cellulose I structure can be maintained in the process. The present invention also provides a simple, inexpensive and benign method for spinning cellulosic filaments from DES.

An additional polymer may be used as a polymer additive for modifying rheology of the dispersion (dope) and enabling crosslinking and providing water stability to the final product.

Said shaped articles comprise films, membranes, filaments, yarns, nonwovens, paperlike structures and structures having varying thickness and shape, and the like. The process exploits deep eutectic solvents as swelling agents and rheology modifiers, as well as separating agent for the fibres. Swelling without dissolving preserves the strength properties and maintains the characteristics of cellulose fibres, particularly native cellulose fibres. All chemicals used in the process can be fully recycled and reused, which makes this new production technology environmentally and economically attractive.

Deep eutectic solvent

The deep eutectic solvent is selected from the group consisting of DESs, which are able to swell cellulosic material without dissolving it whereby the cellulosic material can be dispersed in the DES.

The deep eutectic solvents suitable for the present invention are selected from DESs composed of choline chloride and urea, choline chloride and malonic acid, choline chloride and oxalic acid, choline chloride and phenylacetic acid, and choline chloride and glycerol. Choline chloride acts as the hydrogen bond acceptor and the hydrogen bond donor is selected from urea, malonic acid, oxalic acid, phenylacetic acid and glycerol. Preferably a DES composed of choline chloride and urea is used. Choline chloride has a melting point of 302°C and that of urea is 133°C. The eutectic mixture melts at 12°C. Choline chloride (ChCI) is inexpensive, biodegradable and nontoxic quaternary ammonium salt that can be extracted from biomass or readily synthesized from fossil reserves. The DES comprises a molar ratio from 5 : 1 to 1 : 3, preferably from 3 : 1 to 1 : 2 of choline chloride and the hydrogen bond donor, respectively. Particularly preferably a molar ratio 1 : 2 of choline chloride and the hydrogen bond donor, preferably urea is used.

The DES is obtainable by mixing the components at a temperature of 20-150°C, preferably 40-120°C, particularly preferably 50-110°C until a clear homogenous liquid is formed. The mixing may be carried out under a pressure from 100 mbar to 10 bar, suitably normal atmospheric pressure is used.

The DES may be dried to reduce the water of the DES to below 10 wt%, preferably to below 5 wt%. The drying may be carried using any suitable methods, such as drying under vacuum using elevated temperature, such as 30-60°C.

The DES is maintained in liquid form at a temperature, which is suitable for said DES, typically about room temperature. For example DES comprising choline chloride and urea is kept at the temperature of at least 25°C, preferably at least 40°C for maintaining it in solution.

Cellulosic material

The cellulosic material may comprise a wide variety of cellulose based raw materials. Pulp fibres derived from wood pulp and pulp from other natural sources, such as kenaf, straw, acaba, coir, flax, jute, kapok, raffia, bamboo, hemp, modal, pine, ramie, sisal etc. may be used. Softwood pulps and hardwood pulps and mixtures thereof are suitable for the present process. Mechanically treated pulp fibres, chemically treated pulp fibres and chemimechanically treated pulp fibres, such as chemithermomechanical pulp fibres (CTMP), bleached chemithermomechanical pulp fibres (BCTMP), thermomechanical pulp fibres (TMP), refiner groundwood pulp fibres, groundwood pulp fibres, enzymatically treated pulp, cellulose microparticles, cellulose nanoparticles, microfibrillated cellulose, nanocellulose, enzymatically fibrillated cellulose, and combinations thereof may be used.

Suitably chemical wood pulp fibres, which can be obtained from well-known chemical processes such as the kraft and sulfite processes, with or without subsequent bleaching may be used. Chemically treated pulp fibres, such as oxidized cellulose provides a final product with functional groups. According to a preferable embodiment softwood pulp and/or enzymatically treated softwood pulp is used.

According to a preferable embodiment the cellulosic material comprises native cellulose. Polymer additive

Optionally at least one polymer additive may be used. The polymer additive is selected from polyacrylic acids, preferably from polyacrylic acids having average molecular weight Mv in the range from 10 to 30 000 000 mol/g, preferably from 100 000 to 1 000 000.

Short wood fibres do not naturally form strong filaments and they have a tendency to disintegrate in water. Due to this it is preferable to add a polymer additive into the matrix, which comprises the cellulosic material. Polyacrylic acid can react with cellulose hydroxyl groups with its carboxyl functionality, and further, it can also be cross-linked simply by adding heat in order to make the shaped article, such as cellulose-polymer composite, water-stable. Cross-linking of pulp fibres with polyacrylic acid by heat initiated esterification is shown below.

Polyacrylic acid (PAA) is a hydrophilic and non-toxic polymer, thus it is particularly suitable for the present invention.

The final products comprising the polymer additive are cross-linked at a temperature from 120 to 180°C, preferably from 130 to 150°C.

Process for producing shaped articles

The process of the invention, for producing shaped articles comprises the steps, where 0.5 -20 wt% of cellulosic material, calculated from the total weight of the dispersion, is suspended in a DES comprising choline chloride and a hydrogen bond donor selected from urea, malonic acid, oxalic acid, phenylacetic acid and glycerol, at a temperature from 10-280°C, whereby a dispersion is obtained, and shaped articles are formed from the dispersion.

The DES comprises a molar ratio from 5 : 1 to 1 : 3, preferably from 3 : 1 to 1 : 2 of choline chloride and the hydrogen bond donor, respectively. Particularly preferably a molar ratio 1 : 2 of choline chloride and the hydrogen bond donor, preferably urea is used . Suitable molar ratio for choline chloride and malonic acid is 1 : 1.

The dispersion is used as a dope for forming the shaped articles. The dispersion is formed by mixing the components and the obtained dispersion is cooled to ambient temperature.

Preferably 3-10 wt% of the cellulosic material is dispersed in the DES.

The cellulosic material may comprise one material or a combination of two or more materials. Suitable cellulosic materials are listed above. Preferably the cellulosic material comprises wood-based pulp. The cellulosic material is suitably ground or milled prior to suspending step to obtain smaller particles, where by a more homogeneous dispersion is obtained. Prior to adding the cellulosic material in the DES the cellulosic material may be dried. Suitably the cellulosic material contains not more than 10 wt% of water, preferably from 0 to 5 wt%.

Preferably the cellulosic material is mixed in the DES at a temperature from 10-200°C, particularly preferably 70-130°C, even more preferably 80-110°C to obtain a mixture.

Elevated temperatures accelerate the swelling and separation of fibres and enhances the forming of a viscous dispersion. The mixture is further mixed vigorously (dispersed) for converting it to a high viscosity dispersion. The dispersing may be carried out by mixing with any suitable mixing, speedmixing or homogenizing apparatus. The mixing can be carried out in one step or step-wise in more than one steps. A pressure from 10 to 100 mbar may be used in the dispersing. The mixing time is suitably from 1 min to 30 hours.

According to a preferable embodiment a polymer additive selected from polyacrylic acids is added to the dispersion. The amount of the polymer additive ranges from 0-50 wt%, preferably from 0.1 to 25 wt%, calculated from the dry weight of the shaped article. The dispersion is mixed and/or homogenized after the addition of the polymer additive.

The polymer additive is preferably selected from polyacrylic acids having average molecular weight Mv in the range from 10 to 30 000 000 mol/g, preferably from 100 000 to 1 000 000.

The polymer additive is used for controlling the rheology of the dispersion, for providing stretchability and increasing spinnability of the dispersion, for increasing hardness of the final product and for modifying the properties of the final product. The polymer additive cross-links with the cellulose.

The obtained dispersion (dope) may be used directly for forming the shaped articled, or alternatively it may be stored, suitably protected from moisture. The dispersion (dope) is formed into the required shape. According to a preferred embodiment the shaped articles are fibres, fibrils or filaments, which are preferable formed by extruding the dispersion through a spinneret to produce fibrous material. However, any fibre, fibril or filament forming technique may be employed. According to one preferable embodiment the forming is carried out by spinning.

Likewise, in other embodiments where the shaped articles other than filaments are prepared, the dispersion may be moulded, casted, formed or shaped into desired arrangement using conventional techniques known in the art, such as extrusion, sedimentation, 3D-printing, casting, molding or formation. The shaped article retains its form when the DES is removed and the shaped article is washed.

The shaped articles are washed with a solvent selected from primary alcohols, water, ethyl acetate, isopropanol, hexane, toluene, acetic acid, tert-butanol and their mixtures, preferably ethanol is used. The washed articles are suitably dried. The drying is carried out at a temperature from 15 °C to 200 °C. Sedimentation is particularly suitable for providing porous structures, such as membranes, which are suitable for example for filter materials, non-woven and the like.

The spinning may suitably be carried out by wet-spinning where the dope is extruded into a spin bath to obtain a filament. The spin bath comprises a solvent selected from primary alcohols, water, ethyl acetate, isopropanol, hexane, toluene, acetic acid, tert- butanol and their mixtures, preferably ethanol is used. The obtained filaments are suitably washed with the solvent and dried.

In the embodiment where the polymer additive is used, the dried shaped articles, such as filaments, are treated with water and cross-linked at a temperature from 120-180°C, preferably 130-150°C.

Optionally additives, such as colouring agents, fragrants, polymeric fibres, natural fibres, mineral fibres, carbon nanotubes, reflecting particles etc. may be added to the dispersion prior to or after the forming.

Shaped articles

The shaped articles comprise cellulose fibres comprising cellulose of crystalline form I. According to a preferable embodiment the shaped articles are obtainable by the process of the invention.

The shaped articles may be in a form selected from films, membranes, filaments, yarns, nonwovens, paper-like structures, and structures having varying thickness and shape, i.e. thicker and non-planar structures, as well as composite structures.

The shaped articles may comprise 0 -50 wt%, preferably 0.1- 25 wt% of a polymer additive selected from polyacrylic acids.

Preferably said polyacrylic acids have average molecular weight Mv in the range from 10 to 30 000 000.

According to a preferable embodiment the shaped article comprises 0.1-25 wt% of polyacrylic acid, where the polyacrylic acid is cross-linked with the cellulose. According to preferable embodiment the shaped article is a filament, film, nonwoven or membrane. According to a preferable embodiment the cellulose is obtained from wood-based pulp.

According to a preferable embodiment the shaped article has porous or non-porous structure. Use of the shaped articles

The obtained shaped articles find use in several fields. The shaped articles may be used in various applications due to the versatility of the developed process and starting materials. Suitable applications are yarns, ropes, textiles, cloths, nonwovens, membranes, films, filters, isolation materials and composite structures.

The obtained filaments are stable in water, which is practically a must-have requirement for the vast majority of applications. For some applications the water stable filaments can be used as such, but plying them into multifilament yarns and ropes further widens their use.

Textile applications benefit from lightness and possibility for colored or multicolored yarn.

The high quality wood cellulose filaments produced from non-dissolved pulp, such as cellulose-PAA yarn can be used in wood-based cellulosic fabrics. These fabrics can be used where ever natural fibre fabrics are needed, e.g. clothing, technical textiles etc., thus providing inexpensive and eco-friendly wood-based textiles.

The high quality wood cellulose filaments are particularly suitable for products which are directly dependent on long fibre filament or yarn, including clothing textiles, technical textiles and interior textiles.

The membranes are particularly suitable for various filter applications, film applications, for isolating materials, and non-woven applications.

Further, the shaped articles may be used as components in composite structures. Besides light weight, stiffness of filaments is beneficial in supporting structures for composites. Oxidized pulp as starting material for filaments makes said filaments particularly suitable in the medical sector, such as nonwovens and textiles, due to the hemostatic property of oxidized pulp.

The present invention provides several advantages. A simple, non-toxic and affordable method is provided that uses deep eutectic solvent as swelling agent and rheological modifier for cellulosic materials, such as bleached pulps, in order to produce strong and water-stable filaments. The cellulosic material, such as pulp defines some of the properties of the final product, such as filament. The simplicity of the process allows one to use a variety of pulps including softwood, enzymatically treated pulps, oxidized pulps and cellulose nanofibrils or their combinations. The process allows the use of several cellulosic materials and mixtures thereof for tailoring the characteristics of the final product, such as the chemical composition, structure, porosity, color etc. of the product.

Due to the low dry matter contents used in the process, the process outcome is in one preferable embodiment a porous product, such as filament. Porous structure of the filament can also be considered as an advantage due to lightness and good insulation properties of the filament. Is can also be utilized as composite reinforcement as a polymer can be easily impregnated in to the structure.

Single filaments with variable thickness can be twisted and plied into multifilament yarns with texture depending on the plying technique. Twisting even a single filament improves tenacity values and plying and cabling several filaments improves the values even more. The produced filaments are porous, light and can be produced from bleached or dyed pulp. The filaments are quite stiff and have good strength properties in dry and moist conditions. They remain intact and can be easily handled even after several months after soaking in water. Pulp fibres are not dissolved in the process, meaning that the strength potential and unique moisture balance properties of cellulose I are retained.

Wood-based cellulose-PAA long filament/yarn made out of pulp is inexpensive and the manufacture is environmentally sustainable. The final product, such as filaments comprising cellulose I crystalline structure possesses all the good qualities of native cellulose. The spinning does not disintegrate the native crystalline structure of cellulose. Manmade fibre from cellulosic materials, particularly from wood-based cellulose is considered as a sustainable alternative for cotton. The use of these alternative wood- based raw materials reduces sweet water consumption, particularly for irrigation, as well as occupation of agricultural land and the use of plant protection chemicals.

A further advantage of the invention is the recyclability of the DES and solvents used in the process. As shown in the examples and in Figure 6 choline chloride/urea (ChCI/urea) can be easily recycled using simple evaporation or distillation techniques for separation and the obtained ChCI/urea can be reused in the process.

The invention will now be illustrated with the following examples.

Examples Example 1

MANUFACTURE OF SHAPED ARTICLES

This example illustrates a process where pulp filaments with PAA as a polymer additive (crosslinker) and without PAA are obtained. The process utilizes ChCI/urea as a medium for spinning dope due to its ability to disperse and swell pulp fibres and dissolve PAA. Ethanol was used in spin bath due to its ability to dissolve ChCI/urea without disintegrating the pulp-PAA filaments. The end product was a filament, which can be processed further into a yarn by combining several filaments by twisting or plying. In the process ChCI/urea is used as rheological modifier, swelling and dispersing agent. Swelling of the pulp fibres was achieved without dissolution with the help of DES, whereby well dispersed spinning dope for filament production was obtained. The suitability of ChCI/urea was based on high hydrogen bond-forming activity and high polarity, which are associated with high swelling power. In practice, the swelling of the pulp can be detected as gelling behavior of the pulp-ChCI/urea solution, which is related to formation of gel particles as a result initial swelling of the fibres.

Also filaments without PAA were produced with the same method, where no PAA was used.

The process of Example 1 is illustrated in Figure 1.

Never-dried bleached softwood pulp, polyacrylic acid (PAA, Mv ~450 000 mol/g), urea and choline chloride (ChCI) were used as starting materials. Preparation of spinning dopes

ChCI/urea DES was prepared by mixing ChCI and urea together in a mole ratio of 1 : 2, respectively and heated at 100°C with constant stirring until a clear homogenous liquid was formed, followed by drying at 40°C overnight under vacuum, whereby the water content was reduced to less than 1 wt%. Prior to adding in ChCI/urea, the pulp was washed with excess acetone and dried at 40°C overnight under vacuum whereby the water content was reduced to less than 1 wt%.

Spinning dopes were prepared by dispersing the pulp in ChCI/urea overnight at 100°C temperature with constant stirring. The dispersions were then cooled and mixed in a Speedmixer under vacuum (800 rpm for 2 min and 1500 rpm for 8 min). PAA was added to the mixture and subsequently mixed again in the Speedmixer. Dry matter contents of final samples were 4.5 wt-% with variable pulp-PAA ratios (100: 0, 95 : 5, 90: 10 and 75 : 25), the rest was ChCI/urea. Spinning dopes were stored in a desiccator until used.

Preparation of filaments by wet-spinning

Pulp-PAA filaments were produced using a laboratory scale wet spinning device.

Spinning dope was extruded using constant speed into ethanol spin bath from a 5 ml syringe through a tapered tip with 0.63 mm nozzle. Filaments were washed in ethanol for at least 10 minutes and dried at ambient conditions. Subsequently, filaments were dipped at room temperature to distilled water for 5 seconds and placed in an oven at 140°C for 30 minutes. Pulp fibres were cross-linked with PAA using heat initiated esterification where carboxyl groups of PAA form ester bonds with hydroxyl groups of cellulose. Immersing the dried filaments into water prior to crosslinking at 140°C enhances the crosslinking process. The process results water-stable filaments with improved strength properties. Characterization of pulp fibres

Viscosity average molecular weights of untreated pulp samples and pulp samples after ChCI/urea treatment were determined by capillary viscometry according to standard ISO 5351 : 2004. Prior to the measurement the samples were washed and filtrated using distilled water and dried in vacuum at 40°C. 13C cross polarization magic angle spinning (CP MAS) NMR spectra were measured from untreated pulp sample and pulp sample kept in ChCI/urea overnight at 100°C. Both samples were washed thoroughly with acetone and dried in vacuum oven (40 °C, overnight) prior to measurements. Filament properties

A C-Impact fast strain rate tensile tester was used for tensile testing. The span length of tensile tester was 50 mm. The strain rate was 1 mm/s (2 %/s) . Accuracy of displacement measurement was better than 6 μιη i.e. 0.012 % with sample length 50 mm. Accuracy of force measurement with the used measurement setup was better than 15 mN. The tests were performed at laboratory conditions at 23°C and 50 % relative humidity. Prior to tensile testing the dry filament samples were stored in laboratory conditions at least for 24 h and the wet samples were immersed in water for 24 hours. Tenacity and strain were determined from the results. Count related tenacity was calculated using linear density (tex).

Scanning electron microscopy (SEM) was used to study morphology of the filaments with different pulp-PAA ratios. Samples were prepared on double-sided carbon adhesive discs attached on aluminum specimen stubs. Prior to imaging the samples were sputter coated with platinum (Pt) to improve specimen conductivity. The imaging was conducted using 3.0 keV electron energy and 30 pA probe current. The pixel resolution was 2048 x 1536 dpi.

Recycling of ChCI/urea

To study the recycling of ChCI/urea, 4ml of filament mixture (ChCI/urea 95.5 %, pulp 4.05 %, PAA 0.45 %) was extruded in ethanol (50ml) that was evaporated at ambient conditions overnight and the remaining liquid fraction was studied using FT-IR spectrometer with ATR diamond. Pure ChCI/urea was measured as a reference. All spectra were obtained from 32 scans with resolution 4cm ¹ and transmission mode from 350 to 4000 cm^"1-

Effect of ChCI/urea on cellulose properties

Reference pulp and pulp after dispersion overnight in ChCI/urea at 100°C were measured using capillary viscometry and (CP MAS) NMR. (CP MAS) NMR gives the resonance profiles of the carbons in the anhydroglucose unit. These profiles have typical features for each allomorph and the changes in profiles implicate if the cellulose has been dissolved during the process. According to the measurements the spectra remained unaltered after ChCI/urea treatment. Wood pulp contains mostly cellulose crystalline form of Ιβ which differs from cellulose II form and the indicators for distinguishing these forms can be found in spectra of C-1 and C-4 and C-6 regions. In cellulose II form symmetric doublets in C-1 and C-4 regions are characteristic. NMR spectra of bleached softwood pulp before (bottom) and after (after) dispersing in ChCI/urea at 100°C for 24h are shown in Figure 2.

Capillary viscometry was used to measure intrinsic viscosity of cellulose in cupriethylene diamine (CED) solution, which can be used to approximate of degree of polymerization (DP). (ISO 5351 : 2010). DP of cellulose decreased only slightly after being dispersed in ChCI/urea for overnight in 100°C, from 1226 (± 0.5%) to 1194 (± 0.8%), which could be caused by mechanical damage due to stirring. But since the difference was less than 2%, the result indicates that there was no significant degradation.

Filament morphology

SEM images in Figure 3 show that the filament shape is irregular, which is caused by the manufacturing method. Only 4.5% of the extruded filament consists of pulp and PAA, and the rest, ChCI/urea, is rinsed away in ethanol spin bath. This causes the porous structure of the filament and affects the shape. The dispersing step and homogenizing the spinning dope has effect on the filament shape. Drying was done at ambient conditions. The fibre orientation in the filaments affects the strength of the filament and according to the SEM micrographs, the orientation was relatively good . From the SEM images it can be seen that filaments can also be obtained without PAA. However, the properties of the pulp-PAA are different, particularly with respect to water resistance.

Mechanical properties of filaments

Figure 4 illustrates count related tenacity (a) and strain (b) measured from dry and wet samples. Count related tenacity was used to measure the strength of dry and wet filaments. Count related tenacity is calculated using linear density, which allows better comparison due to porous nature of the filaments. Linear densities measured were between 20 to 25 tex. With dry filaments, clear improvement in tenacities was seen with 5% of PAA addition. The positive effect seemed to diminish when PAA addition was increased to 25%. Declining tenacity curve indicates that excess PAA that is left into filaments unbound, which weakens the structure. In wet filaments, without PAA addition, the filaments were not stable in water, except for quick immersion, and only one strength measurement was able to be conducted successfully. The long term water stability was also tested by immersing the filaments in water for several weeks. The filaments containing PAA remained intact in water and were fully manageable when taken out. Strain indicates elongation before breaking. The values for the filaments were in the similar level as cotton and half of the values for viscosity. Better understanding what happened during elongation can be achieved from the stress/strain curves.

In stress/strain curves increase in slopes were noted, which indicates that the fibres exhibit strain hardening in tensile tests (Fig. 5). This can be seen only in samples with added PAA, therefore can be assumed that after the fibres have been straighten out or oriented, the covalent bonds between PAA and pulp fibres resist breakage in the end. Figure 5 shows stress/strain curves of the sample containing 5% of PAA. Left side in 50% RH and right side in wet state.

The importance of materials recycling cannot be underestimated. It is important as an ecological point of view, but when entering an already saturated market the economical aspect becomes even more crucial. According to the FT-IR spectra (Fig 6), freshly prepared and recycled ChCI/urea from ethanol were identical and there were no peaks that could be identified as PAA, ethanol or pulp. This indicated that recycling of ChCI/urea can be easily done using simple evaporation or distillation and ChCI/urea can be reused in the process. In Figure 6 FT-IR Spectra of unused and recycled ChCI/urea are presented.

The present invention has been described herein with reference to specific embodiments. It is, however clear to those skilled in the art that the methods and products may be varied within the scope of the claims.

Claims

1. A process for producing shaped articles, characterized in that the process comprises the steps, where 0.5 -20 wt% of cellulosic material, calculated from the total weight of the dispersion, is suspended in a DES comprising choline chloride and a hydrogen bond donor selected from urea, malonic acid, oxalic acid, phenylacetic acid and glyserol, at a temperature from 10 to 280°C, whereby a dispersion is obtained, and shaped articles are formed from the dispersion.

2. The process according to claim 1, characterized in that the cellulosic material is selected from pulp fibres derived from wood-based pulps and from natural fibres.

3. The process according to claim 1 or 2, characterized in that the cellulosic material is selected from mechanically treated pulp fibres, chemically treated pulp fibres, chemimechanically treated pulp fibres, enzymatically treated pulp fibres, cellulose microparticles, cellulose nanoparticles, microfibrillated cellulose, nanocellulose, enzymatically fibrillated cellulose, and combinations thereof.

4. The process according to claim 1 or 2, characterized in that the cellulosic material is selected from kenaf, straw, acaba, coir, flax, jute, kapok, raffia, bamboo, hemp, modal, pine, ramie, sisal and combinations thereof.

5. The process according to any one of claims 1-4, characterized in that the cellulosic material is suspended in the DES at a temperature from 10-200°C, preferably 70-130°C.

6. The process according to any one of claims 1-5, characterized in that the DES comprises molar ratio from 5 : 1 to 1 : 3, preferably from 3 : 1 to 1 : 2 of choline chloride and the hydrogen bond donor.

7. The process according to any one of claims 1-6, characterized in that the hydrogen bond donor is urea.

8. The process according to any one of claims 1-7, characterized in that the forming is selected from spinning, molding, casting, shaping, extruding, sedimentating and 3D-printing.

9. The process according to any one of claims 1-8, characterized in that the shaped articles are washed with a solvent selected from primary alcohols, water, ethyl acetate, isopropanol, hexane, toluene, acetic acid, tert-butanol and their mixtures, preferably ethanol is used.

10. The process according to any one of claims 1-9, characterized in that the shaped articles are dried.

11. The process according to any one of claims 1-10, characterized in that from 0-50 wt%, preferably from 0.1 to 25 wt% of a polymer additive selected from polyacrylic acids is added to the dispersion, calculated from the dry weight of the shaped article.

12. The process according to claim 11, characterized in that the polyacrylic acids are selected from polyacrylic acids having average molecular weight Mv in the range from 10 to 30 000 000, preferably from 100 000 to 1 000 000.

13. The process according to claim 11 or 12, characterized in that the shaped articles are treated with water and cross-linked at a temperature from 120- 180°C, preferably 130-150°C.

14. Shaped articles, characterized in that they comprise cellulose fibres comprising cellulose of crystalline form I.

15. Shaped articles according to claim 13, characterized in that they are obtainable by the process of any one of the claims 1-13.

16. Shaped articles according to claim 14 or 15, characterized in that they comprise films, membranes, filaments, yarns, nonwovens, paper-like structures and structures having varying thickness and shape.

17. Shaped articles according to any one of claims 14-16, characterized in that they comprise 0-25 wt% of a polymer additive selected from polyacrylic acids.

18. Use of the shaped articles according to any one of claims 14-17 in yarns, ropes, textiles, cloths, nonwovens, membranes, films, filters, isolation materials and composite structures.