FIELD

[0001] The present invention relates to a method for producing wood-based yarn filaments from DES-pulp suspension.

BACKGROUND

[0002] Cellulose plays an important role in textile and filament production. For example, the long fibers of natural cotton are ideal for forming strong filaments and yarns, whereby cotton is traditionally utilized in textiles. However, the use of cotton requires lots of water, pesticides and fertilizers in the production phase.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] Deep eutectic solvents (DES) are a type of ionic solvents which refer to eutectic mixtures, which melting points are lower than the individual components of separately. 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. For example WO 2012/145522 relates to deep eutectic solvents for the purpose of dissolving cellulose.

[0007] DES-pulp is typically manufactured into the fibre yarn filament by extruding it into ethanol bath. The function of the ethanol has been to dissolve the DES away, which requires long time, such as up to 15 minutes. In addition, NFC fibre yarn filaments have a tendency to stick into the rollers/cylinders in the production process.

[0008] Thus, there is a need to discover a process for manufacturing yarn filaments from wood-based material in more efficient and less time-consuming manner.

SUMMARY OF THE INVENTION

[0009] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0010] According to a first aspect, it is provided herein a method for producing wood-based yarn filaments from DES-pulp by extrusion and laminar solvent flow system.

[0011] This and other aspects, together with the advantages thereof over known solutions are achieved by the present invention, as hereinafter described and claimed.

[0012] The method according to an embodiment of the present invention is mainly characterized by what is stated in the characterizing part of claim 1.

[0013] The fiber yarn filament according to an embodiment of the present invention is mainly characterized by what is stated in claim 9 and the use thereof by what is stated in claim 10.

[0014] Considerable advantages are obtained by means of the invention. The present invention provides a simple non-toxic method that uses DES-pulp and laminar solvent flow to produce strong and water- stable fiber yarn filaments. The method enables producing more fibre yarn filaments in the same time span as currently has been possible. In addition, the solvent can be circulated and used again during the production process. Furthermore, the present invention reduces the investment costs and the production time and enables easier upscaling of the process. [0015] Next, the present technology will be described more closely with reference to certain embodiments.

EMBODIMENTS

[0016] The present technology describes a method for manufacturing DES-pulp suspension into a fibre yarn filament. Preferably, the method is continuous.

[0017] 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.

[0018] FIGURE 1 is a process scheme describing one embodiment of the present invention.

[0019] FIGURE 2 is a process scheme describing another embodiment of the present invention.

[0020] The present invention is based on extruding DES-pulp suspension into flowing solvent. The function of the flowing solvent is to dissolve DES from the extruded filament. Laminar flow of the solvent immediately starts the dissolution process of DES, providing substantially shortened DES-removal time. In turn, this enables less time consuming method for yarn filament production from such starting material.

[0021] According to one embodiment of the present invention, 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.

[0022] According to another embodiment of the present invention, the DESs 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.

[0023] 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.

[0024] One embodiment of the present invention is a method for continuously producing wood-based yarn filaments, the method having at least the steps of: suspending a cellulosic material in a DES (deep eutectic solvent) comprising choline chloride and urea at temperature of 10 to 280 °C for obtaining a DES-pulp suspension, and extruding the DES-pulp suspension into a solvent, wherein the DES-pulp suspension is extruded into a running laminar solvent flow at a speed of 1 to 15 cm/s, after which the produced fiber yarn filaments are collected and dried.

[0025] According to one embodiment of the present invention, the method uses a solvent which is an alcohol that is capable to dissolve the components of the used DES.

[0026] According to another embodiment of the present invention, the solvent is ethanol.

[0027] According to one embodiment, suspending a cellulosic material in DES comprising choline chloride and urea is carried out at temperature of 10 to 130 °C for obtaining the desired DES-pulp suspension.

[0028] According to further embodiment of the present invention, the laminar solvent flow speed is between 2 and 10 cm s, preferably between 3 and 6 cm/s, such as 4.5 cm/s. It is possible to change the solvent flow speed for example by altering the pumping speed or by changing the angle of the gutter, wherein the extrusion takes place.

[0029] According to one embodiment of the present invention, the solvent is recycled back to the process by a pump and used at least two times. [0030] According to one embodiment of the present invention, the cellulosic material may comprise a wide variety of cellulose based raw materials. For example pulp fibres derived from wood pulp may be used. Also 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, micro fibrillated cellulose, nanocellulose, enzymatically fibrillated cellulose, and combinations thereof may be used.

[0031] According to one embodiment of the present invention, the cellulosic material is hardwood pulp. This is preferred in order to obtain continuous fibre yarn filaments.

[0032] Thickness of the fiber yarn filament may be changed according to the end-use purpose by altering the nozzle size in the extrusion. Single filaments with variable thickness can also 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.

[0033] Fibre yarn filaments 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 present invention is the recyclability of the DES and solvents used in the process.

[0034] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0035] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0036] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0037] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0038] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0039] The verbs "to comprise" and "to include" are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

[0040] At least some embodiments of the present invention find industrial application among for example yarns, ropes, textiles and cloths. The obtained filaments are stable in water. For some applications the water stable filaments are used as such, but plying them into multifilament yarns and ropes further widens their use. In addition, textile applications benefit from lightness and possibility for coloured or multicoloured yarn.

[0041] Furthermore, the obtained high quality wood cellulose filaments 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.

EXAMPLE 1 - General method

The DES-pulp solution was prepared as follows. ChCl/urea DES was prepared by mixing ChCl 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 ChCl/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 ChCl/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).

The DES containing typically 4 % of anhydrous pulp fibres was place into a syringe containing a nozzle with required dimensions. The DES-pulp suspension is extruded into a laminar ethanol flow in a canal with downward slope (5-20 degrees). The ethanol flow takes the wet filament ribbon from the nozzle and transports the wet filament ribbon into the collection chamber. The flow rate of ethanol is above the flow rate of the DES-pulp suspension from the nozzle. The difference in the flowrate maintains straight filament direction and can stretch the filament. The continuous flow around the filament accelerates the diffusion out of the DES chemicals from the filament. After keeping the filament in the collection chamber for 30 to 120 min, the filament is wound and heat activated in an oven at 130 °C for 20 min.

CITATION LIST

Patent Literature:

WO 2012/145522