EP4695460A1

EP4695460A1 - A method for producing a structured fibrous mat

Info

Publication number: EP4695460A1
Application number: EP24729387.1A
Authority: EP
Inventors: Karl HÅKANSSON; Söderberg DANIEL; Jakob Redlinger-Pohn; Fredrik LUNDELL; Mathias KVICK
Original assignee: Celluxtreme AB
Current assignee: Celluxtreme AB
Priority date: 2023-05-24
Filing date: 2024-05-15
Publication date: 2026-02-18
Also published as: WO2024241155A1

Abstract

The invention relates to a method for producing a structured fibrous mat, comprising the following steps: a) injecting a dispersion comprising polymer(s) and/or non-spherical particles in a suitable liquid into a reaction chamber (4) comprising at least an inlet (9) and an outlet (8), b) coagulating the dispersion into a continuous wet thread (6) in the reaction chamber by the introduction of a co-flowing coagulation liquid into the reaction chamber (4), c) separating the liquid (5) from the continuous wet thread (6) at the reaction chamber outlet (8), d) positioning the coagulated thread at the reaction chamber outlet between at least two attachment points on or into a solid, liquid or gas collector (7) thereby allowing for the generation of a weave at the reaction chamber outlet and controlling the geometry of the fibrous mat, and e) optionally, drying the produced mat.

Description

A method for producing a structured fibrous mat

Technical field

The invention relates to a method for producing a structured fibrous mat from long-chained polymer(s) and/or non-spherical particles, preferably from nanocellulose.

Background

In composite manufacturing, continuous fibers or staple fibers are combined with a liquid or melted matrix to produce a solid composite after solidification, i.e. a component. The alignment of the fibers is crucial to the engineering performance of the component. Therefore, a manufacturing process that can control the alignment will maximize the possibility of designing the properties of the final composite component.

For lightweight composite materials, where the highest performance is needed, continuous fibers with no twist are used. Today, continuous fibers are firstly spun from a spin dope, which often is post-processed, e.g., carbonized for the case of carbon fibers, and thereafter made into a weave or tape, which in turn can be coated with a matrix into so-called pre-pregs. The weaves or tapes are then possible to place and align in a specified direction, either by hand or in an automatic lay-up process. Besides the many processing steps, these two-dimensional weaves or tapes limit the possible structures, leading to a lot of waste material and is timeconsuming to put together, especially when put together into complex three-dimensional structures. Therefore, fewer manufacturing steps, less waste, as well as increased degrees of freedom of design are wanted.

At the same time, more environmentally friendly materials are sought after for the lightweight composite segments, which are dominated by carbon and glass fibers. Cellulose nanofibrils are stiff and strong [https://doi.org/10.1021/bm301674e], in the same range as glass fiber and low-grade carbon fiber, which could make them suitable for lightweight composites. To utilize the mechanical properties of the cellulose nanofibrils the need for alignment control is crucial. It has been shown that the cellulose nanofibrils can be aligned to form macroscopic pm-sized fibers (EP2909365B1) using a compact reaction chamber. However, to produce a centimeter to meter-sized component, the fibers should, in turn, be aligned and positioned in accordance with performance specifications. This could be accomplished by traditional weaving of the dry thread in different manners [https://spinnova.com/collaboration/pusu/]. However, detailed structures, complex designs and positioning of individual fibers have not yet been presented. It should also be noted that weaving introduces extra process steps.

Another way of achieving high-resolution fiber alignment is to use one of the many technologies that use continuous fiber additive manufacturing. However, these technologies are also designed for starting with dry fibers on a roll, which means that the fibers must first be produced, dried, and rolled before they can be fed into the machine.

Wet spinning usually relies on producing a continuous fiber from a nozzle submerged into a bath and thereafter stretching and washing steps before drying the fibers. Also here, the alignment of the components inside the fiber determines the properties of the final fiber and the alignment is primarily achieved by stretching the fiber prior to or in the coagulation bath, or during the washing and drying steps. In the spinning of cellulose nanofibrils described in EP2909365B1, the alignment is achieved in the nozzle and locked with a coagulation liquid. This closed system constituted by the nozzle is here referred to as the reaction system.

US2024058077 discloses a method for classical wet spinning, where a dope is injected into a bath containing a coagulation agent that gels/solidifies the dope into a gel thread. This method always incorporates rolls to transport the gel thread through the bath until the gelling is complete and for further processing after the bath. The injection can be directly into to bath or with an air gap prior to entering the bath. The dope is thus extruded through nozzles into the bath. Thus, the nozzle and orifices make up the "extruder," and the solidification is achieved by the bath. The reaction system for this case is thus constituted by the nozzle(s) and the bath, which is 'always open and contains significant amounts of liquid, typically >1000 times the total volume of the gel thread in the reaction system.

Forming a mat using the method described in US2024058077 requires the gel thread to be dried, and this is done by controlling the position of the gel thread using an auxiliary system that is not disclosed. This is done by manually lifting the gel threads into a so-called 0°-90° weave. US2024058077 does not present any method of automatically producing a structured fiber network/weave.

Furthermore, it is possible to use cellulose nanofibrils at concentrations of >1%, with or without rheology modifiers, to directly and additively manufacture structures (ES2886127T3). However, at these concentrations, the fibrils are highly entangled, and a high alignment has not yet been demonstrated.

It is still a challenge to produce a cm-m sized component with precise alignment of nanoscale cellulose nanofibrils in one single process/method step.

Summary

It is an aim of the present invention to at least partly overcome the above-mentioned problems, and to provide an improved method for producing a structured fibrous mat or stack of mats.

The method comprises or consists of the following steps: a) injecting a dispersion comprising long-chained polymer(s) and/or non-spherical particles in a suitable liquid into a reaction chamber comprising at least an inlet and an outlet, b) coagulating the dispersion into a continuous wet thread in the reaction chamber by the introduction of a coagulation liquid into the reaction chamber, c) separating the liquid from the continuous wet thread at the reaction chamber outlet, d) positioning the coagulated thread between at least two attachment points on a solid, liquid or gas collector thereby controlling the geometry of the fibrous mat, and e) optionally, drying the produced mat.

In some aspects, the method comprises or consists of the following steps: a) injecting a dispersion comprising polymer(s) and/or non-spherical particles in a suitable liquid into a reaction chamber comprising at least an inlet and an outlet, b) coagulating the dispersion into a continuous wet thread in the reaction chamber by the introduction of a co-flowing coagulation liquid into the reaction chamber, c) separating the liquid from the continuous wet thread at the reaction chamber outlet, d) positioning the coagulated thread at the reaction chamber outlet between at least two attachment points on or into a solid, liquid or gas collector thereby allowing for the generation of a weave at the reaction chamber outlet and controlling the geometry of the fibrous mat, and e) optionally, drying the produced mat.

The invention relates to a method of direct wet-spinning and deposition (lay-up) of wet but coagulated fibers (or film) from an outlet of a reaction chamber, such as a nozzle, resulting in a three-dimensional fibrous mat with controlled alignment of the components. This is achieved by coagulating the components present in the dispersion liquid and thereafter separating the coagulated fiber from the liquid, which results in a wet fiber that can be positioned in any desired position, either by moving the nozzle or a surface under the nozzle. The alignment of the components in the dispersion liquid is achieved inside the reaction chamber, while the alignment of the fibers is achieved by moving the nozzle in three dimensions or by moving the collector.

In some aspects, the separation in step c) is achieved by pulling the thread out of the liquid, sucking or blowing away the liquid at the outlet of the reaction chamber/tank, such as a nozzle, using liquid absorbing material, controlling the wetting properties of the reaction chamber outlet, or by using electrostatics forces at said outlet. In some aspects, the separation in step c) is achieved by pulling the thread out of the liquid. Pulling means that the thread is attached to an attachment point and from the attachment point, the thread is pulled away from the liquid surrounding the thread.

For the present invention, the weave is generated at the outlet/nozzle/tip of the reaction chamber at the same time as the gel thread is separated from the coagulation liquid and laid down in a controlled position. By using the method of the invention, there is no limit to the possible structures of the mats to be produced. In some aspects, the mat is two-dimensional. In some aspects, the mat is three-dimensional.

In some aspects, method step d) is automated. In some aspects, the whole method is automated. This method can be fully robotic and allows arbitrary complex structures and not only weaves made from straight fibers. With the method of the invention described here, a complete composite component can be produced in one automated and robotic method, which will lead to drastically reduced waste and reduced transport, and allow for increased freedom of design and shape complexity. The method is environmentally friendlier compared to the known methods. Furthermore, this method significantly reduces the number of processing steps compared with traditional composite methods, where there is one process to produce the fiber, another to produce the pre-preg, a third to align the fibers, a fourth to cure the resin and a fifth for trimming, drilling, and polishing.

An advantage of the method of the invention is the reduced volume of total liquid needed to make a weave due to the use of the compact reaction chamber, in comparison to the volume of the wet spinning reaction system in the prior art. In some aspects, the volume ratio in step b) of dispersion liquid to coagulation liquid is 0.5: 50.

In some aspects, the chamber is a closed chamber having one or more inlet and one or more outlets. An advantage of a closed chamber is that it improves control of the method regarding pressure in the chamber. A closed chamber prevents the evaporation of liquids and contamination of the liquids by dirt and the like. A closed chamber facilitates the automation of the method.

In some aspects, the polymer(s) in step a) is a long-chained polymer(s), i.e. a polymer having more than 25 monomer units. In some aspects, the (long-chained) polymer(s) and/or non- spherical particles are selected from the group comprising or consisting of nanocellulose, polymeric proteins, metal nano-rods and non-spherical carbon particles. In some aspects, the (long-chained) polymer(s) and/or non-spherical particles are nanocellulose. Nanocellulose may be nanocellulose crystal particles or nanocellulose fibers. Nanocellulose exists in abundance and is eco-friendly to use. The use of nanocellulose reduces costs for producing weaves, especially at large scale.

In some aspects, the concentration of the gel threads at the time of forming the weave is <10wt%, or <5wt%, or <3wt%, wherein weight percentages (wt%) is a percentage of the total weight of the mass present in the chamber. In some aspects, the dispersion liquid has a crowding number ranging from 10 to 100. In a further aspect, the dispersion liquid has a crowding number in the range of 50 to 70. The crowding number of the liquid is important for the alignment of the components in the dispersion liquid and, therefore, imperative for the strength and other characteristics of the fibers and/or mats obtained. As explained above, alignment control is crucial when using nanocellulose. The method of the invention allows for the alignment of the components in the dispersion liquid as well as the alignment of the fibers. No additional weaving is needed. There are no limitations regarding the complexity of the detailed structures that can be made using the method of the invention.

The dispersion liquid from step a) and the coagulation liquid from step b) are co-flowing through the reaction chamber, preferably continuously co-flowing. In some aspects, the flowing speed of the two liquids does not deviate by more than 10%.

In some aspects, the flowing speed of the dispersion liquid from step a) and the coagulation liquid from step b) through the reaction chamber are the same or similar and have a maximum difference in flow speed of 10% or less. In some aspects, the liquids used in step a) are selected from the group comprising or consisting of water, acid solutions, organic solvents and ionic liquids, or mixtures thereof. In some aspects, the liquid used is water. Water is relatively cheap and often readily accessible. The use of water reduces costs for producing weaves, especially at a larger scale.

In some aspects, the dispersion liquid further comprises one or more components selected from the group comprising or consisting of conductive polymers, alginate thermoset polymers, thermoplastic polymers, biopolymers, conductive polymers, clay nanoparticles, epoxy polymers, epoxy particles, polymer nanoparticles, polymer microparticles, metal nanoparticles, metal microparticles, carbon nanoparticles, carbon microparticles, magnetic nanoparticles, magnetic microparticles, clay particles and living cells. In some aspects, the dispersion liquid further comprises one or more components selected from the group comprising or consisting of clay particles, conductive polymers and alginate.

The addition of these components will alter or further improve the characteristics of the obtained fiber and mats. The addition of clay may be used to improve the fire resistance of the mats. Biopolymers, such as alginate may be added to improve coagulation. Conductive components can be added to improve the conductivity of the fibers. The addition of a polymer will lead to a composite fiber. One implication of this is that after the structured mat is complete, the matrix and the reinforcement fiber are already in place and when the polymer is cured a composite component is produced. The reduction of method steps reduces time and costs, especially at large scale production. In some aspects, the components above may be attached to the surface of the wet thread to form a coating.

In some aspects, the coagulation liquid is selected from the group comprising or consisting of one or more acid, salt and organic solvent. In some aspects, the coagulation liquid is one or more organic or inorganic acids selected from the group comprising or consisting of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, boric acid, acetic acid and citric acid. In some aspects, the coagulation liquid is one or more salts selected from the group comprising or consisting of Na⁺, Ca²⁺, Fe²⁺, Fe³⁺, Mg²⁺, K⁺, Cu²⁺ and one anion such as Cl’, NO^-3, NO^-2, PO4³ SO4² F and COa²’. In a further aspect, the coagulation liquid is an organic solvent selected from the group comprising or consisting of ethanol, acetone, butanol and isopropanol. Preferably cheap and accessible acids or salts are used, especially in large scale production of fibers and/or mats. The coagulation liquid may also comprise the polymers and particles mentioned above.

In some aspects, the coagulation time is extended by adding a flexible tube at the exit from the coagulation channel. Thus, the coagulation time can be extended by attaching a flexible tube to the one or more chamber outlet, such that a coflowing period of the dispersion liquid from step a) and the coagulation liquid from step b) is extended. The extension of coflowing period may be needed depending on the type of liquids used. The addition of the flexible tube therefore improves the flexibility of the method and allows for a greater variation in types of liquids that can be used in the method. In some aspects, the collector is a solid collector. In some aspects, the collector is a liquid collector. In a further aspect, the collector is a gas collector. The weave is produced at the position of the one or more chamber outlet. This allows for use of different types of collectors, which in turn improves the flexibility of the method.

In some aspects, the method includes step e) and the strength of the fibers are controlled by varying the drying rate and drying time using one or a combination of increasing air flow, increased ambient temperature, reduced ambient humidity, or application of vacuum drying. The drying parameters can be tuned to control and optimize the mechanical performance of the produced fibers.

In some aspects, the method comprises or consists of a further step to be performed after step d) or step e) comprising or consisting of a post-treatment of the obtained mat selected from the group comprising or consisting of crosslinking, surface modification and addition of further material, such as a coating. In some aspects, the method comprises or consists of a further step of carbonization of the mat or stack of mats. The post-treatment can modify the performance of the material towards end use, such as mechanical, electrical, optical, thermal properties.

The invention also relates to a system adapted to perform the method as disclosed herein, comprising or consisting of a first container comprising the dispersion liquid, and a second container comprising the coagulation liquid, hoses adapted to transport the liquid from the containers into a reaction chamber having an inlet and an outlet, whereby the non-coagulated liquid is removed at the outlet and a wet thread is collected on a collector. The angle a between the outlet (extending substantially in the direction of the y- axis) and the surface of the collector (extending substantially in the direction of the x-axis) can vary depending on the geometry of the product to be obtained and the type of collector to be used.

In some aspects, the angle may be between 90 and 5°.

The invention also relates to a fibrous mat obtained by the method as defined anywhere herein, or a stack of fibrous mats obtained by stacking 2 to 10 000 of fibrous mats obtained by the method as defined anywhere herein.

Brief description of the drawings

The invention will now be explained more closely by the description of different embodiments of the invention and with reference to the appended figures.

Fig. 1 shows an apparatus adapted to perform the method of the invention.

Fig. 2 shows a traversable nozzle depositing a wet, just coagulated, filament. The coagulation liquid is seen in the droplet at the nozzle exit. Fig. 3 shows a dry mat of cellulose with attached crossings.

Fig. 4 shows dried fiber intersections. The top row is 30 seconds before the top fiber is placed, and the bottom row is 150 seconds before the top fiber is placed.

Fig. 5 shows a stack of layers of fibrous mats after drying.

Fig. 6 shows a reaction chamber submerged in water, and the wet thread is flowing out of the reaction chamber exit.

Fig. 7 shows a falling droplet and a pulling wet thread from the reaction chamber exit. Fig. 7a. droplet 10 in reaction chamber outlet 8. Fig. 7b. falling droplet 10, pulling wet thread 6 from the reaction chamber outlet 8. Fig. 7c. new liquid droplet 10 builds up with wet thread 6 pulled through the liquid droplet surface.

Fig. 8 shows a reaction chamber, moving from right to left.

Fig. 9 shows a hole positioned at the reaction chamber exit.

Fig. 10 shows a reaction chamber outlet with droplets in different sizes.

Fig. 11 shows a stack of layers of fibrous mats after drying.

Fig. 12 shows a stack of layers of fibrous mats after drying.

Detailed description

Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The method can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to elements throughout.

The terminology used herein is for the purpose of describing particular aspects of the disclosure only, and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The term "geometry" refers to the shape of the obtained mat.

The term "long-chained polymer(s)" refers to a polymer having more than 25 monomer units.

Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

The invention relates to a method for producing a structured fibrous mat, comprising the following steps.

In step a) a dispersion liquid comprising (long-chained) polymer(s) and/or non-spherical particles in a suitable liquid is injected into a reaction chamber 4 comprising at least an inlet 9 and an outlet 8.

The polymer(s) and/or non-spherical particles may be selected from the group comprising or consisting of nanocellulose, polymeric proteins, metal nano-rods and non-spherical carbon particles. The polymer(s) and/or non-spherical particles may be nanocellulose. The polymer may be carboxymethylated cellulose nanofibril.

The dispersion liquid may further comprise or consist of one or more components selected from the group comprising clay particles, conductive polymers, alginate thermoset polymers, thermoplastic polymers, biopolymers, conductive polymers, epoxy polymers, epoxy particles, polymer nanoparticles, polymer microparticles, metal nanoparticles, metal microparticles, carbon nanoparticles, carbon microparticles, magnetic nanoparticles, magnetic microparticles and living cells. The dispersion liquid may be clay particles. The dispersion liquid may be conductive polymers.

The suitable liquid may be selected from the group comprising or consisting of water, acid solutions, organic solvents and ionic liquids, or mixtures thereof. The dispersion liquid may have a crowding number in the range of 10 to 100, or of 20 to 80, or 30 to 70.

In step b) the dispersion from step a) is coagulated into a continuous wet thread 6 in the reaction chamber 4 by the introduction of a coagulation liquid into the reaction chamber.

The coagulation liquid may be selected from the group comprising or consisting of one or more acid, salt, and organic solvents. The coagulation liquid may be one or more organic or inorganic acids selected from the group comprising or consisting of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, boric acid, acetic acid and citric acid. The coagulation liquid may be one or more salts selected from the group comprising or consisting of Na⁺, Ca²⁺, Fe²⁺, Fe³⁺, Mg²⁺, K⁺, Cu²⁺ and one anion such as Cl", NO^-3, NO^-2, PCU³’, SCU²’, F and CC>3²‘. The coagulation liquid may be an organic solvent selected from the group comprising or consisting of ethanol, acetone, butanol and isopropanol. The coagulation liquid may be HCI, at a pH of 1 to 4, or 1 to 3.

The volume ratio in step b) of dispersion liquid to coagulation liquid may be 0.5 to 50, or 1 to 40. In step c) the liquid 5 is separating from the continuous wet thread 6 at the reaction chamber outlet 8.

The coagulation time may be extended by attaching a flexible tube to the one or more chamber outlet 8, which extends a coflowing period of the dispersion liquid from step a) and the coagulation liquid from step b). The tube may have a length of 1 cm to 100 cm, or 1 to 15 cm, or 1 to 10 cm.

The separation in step c) may be achieved by pulling the thread out of the liquid, sucking, or blowing away the liquid at the outlet 8 of the reaction chamber 4. A nozzle or liquid absorbing material may be used for this purpose. Alternatively, the wetting properties of the liquids at the reaction chamber outlet 8 may be controlled. As a further alternative, electrostatics forces at said outlet 8 may be used for this purpose.

In step d) the coagulated thread at the reaction chamber outlet 8 is positioned between at least two attachment points on a solid, liquid or gas collector 7. This allows for the generation of a weave at the reaction chamber outlet 8 and controlling the geometry of the fibrous mat. The concentration of the gel threads at the time of forming the weave, i.e. at the outlet 8, is <10wt%, or <5wt% or <3wt%, wherein weight percentages (wt%) is a percentage of the total weight of the mass present in the chamber.

The flowing speeds of the dispersion liquid from step a) and the coagulation liquid from step b) through the reaction chamber 4 are the same or similar and have a maximum difference flow speed of 2, 5, 7 or 10% or less.

Optionally, the method includes a step e) of drying the produced mat.

Drying may be done using one or combinations of the following techniques: ambient drying, forced air flow, increased ambient temperature, reduced ambient humidity, or application of vacuum drying. All of these techniques include the possibility of using heat recovery. Examples of such techniques may be Ambient, oven, IR, microwave, techniques.

The obtained mat may have any design or geometric structure. The mat may be two- dimensional or three-dimensional.

Figure 1 shows an apparatus suitable for performing the method of the invention. The apparatus comprises a first container 1 comprising the dispersion liquid, and a second container 2 comprising the coagulation liquid. Hoses 3 transport the liquid from the containers 1,2 into a reaction chamber 4. At outlet 8 of the reaction chamber, the non-coagulated liquid 5 is removed and a wet thread 6 is collected on a collector 7. The angle a between the outlet (extending substantially in the direction of the y-axis) and the surface of the collector (extending substantially in the direction of the x-axis) can vary depending on the geometry of the product to be obtained and the type of collector to be used.

Figure 2 shows the exit 8 of a reaction chamber 4, a droplet 10 of the coagulation liquid and the wet fiber 6 being laid out on already placed dry fibers on a collector 7. Here, the reaction chamber is moved in order to place the wet fiber in the correct position. The wet fiber comprises a coagulated carboxymethylated cellulose nanofibril dispersion with a degree of substitution of 0.17, charge 1000 peqv/g, homogenized 2 times and the concentration is 3 g/l. The coagulation liquid is hydrochloric acid at a pH of 2.

A dry fibrous mat is shown in figures 3 and 4 and a stack of mats in figure 5, 11 and 12.

The method of the invention may comprise the following steps; a) injection of a central flow dispersion comprising long-chained polymer(s) and/or non- spherical particles in a suitable liquid into a central flow channel of a reaction chamber comprising at least an inlet and an outlet, wherein the central flow dispersion has a crowding factor N that is less than 100, wherein N is determined by the equation N = 2/3*Cv*(L/d) 2, and wherein Cv is the volume fraction of the long-chained polymer(s) and/or non-spherical particles in the central flow dispersion, L is the characteristic length of the long-chained polymers or non-spherical particles, and d is the characteristic diameter of the long-chained polymers or non-spherical particles, a-1) acceleration of the central flow of the dispersion in the reaction chamber by at least two oppositely directed, aligning liquid flow of the coagulation liquid essentially perpendicular to the central flow, whereby the long-chained polymer(s) and/or non-spherical particles are aligned in the central flow direction, and wherein by essentially perpendicular it is meant that an angle between the central flow and each aligning flow stream is from 70° to 90°, a-2) gelling of the aligned long-chained polymer(s) and/or non-spherical particles, through the diffusion of salt, chelating agent or acid contained in the aligning flow streams, into the aligned long-chained polymer(s) and/or non-spherical particles, followed by coagulation of the gel string obtained,

This step a) may be repeated multiple times using passive or coagulant liquids, b) coagulating the dispersion into a continuous wet thread in the reaction chamber by the introduction of a coflowing coagulation liquid into the reaction chamber, b-1) optionally, polymerization of a polymerizable component contained in the central flow dispersion, c) separating the liquid from the continuous wet thread at the reaction chamber outlet, d) positioning the coagulated thread between at least two attachment points on a solid, liquid or gas collector thereby controlling the geometry of the fibrous mat, and e) optionally, drying the produced mat.

The properties of the fibers are ensured since alignment is achieved at the point of coagulation before separation from the coagulation liquid, and since drying with fixed ends is the only post process step necessary.

In the reaction chamber, the alignment of the components present in the dispersion liquid is achieved, the fiber is formed, and the flow dispersion is coagulated. The alignment of the long- chained polymer(s) and/or non-spherical particles is induced either by a shear flow or an electrical or magnetic field. The method disclosed in EP2909365B1 can be used, which is hereby incorporated by reference. The formation of the flow dispersion into the desired shape can be performed either by the flow fields or the geometry of the reaction chamber.

After forming the fiber, the flow dispersion is coagulated, and the alignment is locked by the introduction of a coagulation liquid. The coagulation liquid contains a coagulation agent and may be chosen from the group of acids, salts and organic solvents. Alternatively, coagulation can be performed by an ultra-violet light activated coagulation, if the long-chained polymer(s) or non-spherical can be cross-linked by ultra-violet light.

At the nozzle exit 8, the wet fiber (coagulated dispersion) is surrounded by a layer of coagulation liquid. The wet fiber must now be separated from the coagulation liquid. The wet fiber can now be extracted from the hanging droplet (coagulation liquid) which can be achieved by pulling the thread out of the surface of the coagulation liquid, sucking, or blowing away the coagulation liquid by a nozzle or liquid absorbing material, controlling the wetting properties (electro, surface design) of the reaction chamber outlet. By moving the nozzle or the collector a fibrous mat is now produced. As an additional step, a flexible tube can be connected to the exit 8 of the reaction chamber outlet, thereby extending the contact time with the coagulation liquid.

The wet fibers 6 are laid out on a collector 7 consisting of two or more attachment points, the attachment points may be wet fibers previously placed, dried fibers or another surface. A hydrophobic surface, for example Teflon or a Teflon coated material is used if the mat should be possible to remove. Strong adhesion can be achieved if a wet fiber is placed on top of another wet fiber. It is possible to tune the joint strength between two fibers placed on top of each other by varying the drying time of the fibers. If the wet fiber is placed on surface, the fiber dries into a film or coating on the surface. Wet fibers can be placed on top of wet fibers already on the collector or on dried fibers. If fibers are placed in contact and parallel on top of another fiber, the fibers will stick together.

The wet fiber may be laid out in gas, such as air or in a liquid such as water, ethanol, acetone, or other organic solvents. Furthermore, the liquid may comprise dissolved salts, polymers or dispersed nanoparticles which could be used to coat the surface of the fibrous mat or penetrate into the wet fibers.

The fibrous mat may now be dried.

The fibrous mat may be subjected to post-treatment either before or after the drying step, by for example electromagnetic irradiation, dipping in a bath, spraying or vapor deposition. The post-treatment may include the additions of material to the surface of the fibers, cross-linking of the components, surface functionalization or impregnation into the fibers.

Parallel nozzles 8 placed in different grid patterns, and/or at different heights may be used. 2 to 1000 or 100 to 1000 or 10 to 500, or 2 to 24 nozzles may be used. The nozzles may be positioned in series or in parallel.

Each nozzle may have its own reaction chamber 4, or one reaction chamber may comprise more than one nozzle 8. Any combination of these two alternatives may be applied in the methos of the invention.

For maximal alignment of the components in the fiber direction, the wet fiber should be shrinking freely which is possible between the attachment points where the wet fiber will be dried and shrink in two directions, with the end points fixed.

The dry fibrous mats can be stacked to form a thicker fibrous mat. A mat may comprise 2 to 10000, or 2 to 500, or 2 to 1000 stacked layers.

The long-chained polymer(s) and/or non-spherical particles may be chosen from the group of nanocellulose, metal nano-rods, polymeric protein(s), and non-spherical carbon materials, are contained in the flow dispersion. The flow dispersion may comprise a combination of the long- chained polymer(s) and/or non-spherical particles. The flow dispersion may additionally comprise clay particles, conductive polymers, alginate thermoset polymers, thermoplastic polymers, biopolymers, conductive polymers, epoxy polymers, epoxy particles, polymer nanoparticles, polymer microparticles, metal nanoparticles, metal microparticles, carbon nanoparticles, carbon microparticles, magnetic nanoparticles, magnetic microparticles and living cells. The flow dispersion may additionally comprise clay particles, conductive polymers, and alginate.

Nanocellulose represents a group of cellulose materials with at least one dimension in the nanometer range. Nanocellulose can be produced by bacteria or extracted from hard wood, soft wood, herbaceous energy crops, and short-rotation energy crops.

As used herein "herbaceous energy crops" means plants with no or little woody tissue and grown for production of food or feed. Examples may be grasses, sugarcanes, corn, soybeans, wheat, barley, sunflower, rapeseed, and the like.

As used herein "short-rotation energy crops" means fast-growing softwoods, such as pine, spruce, birch and cedar or hardwoods, such as poplar, willow, and eucalyptus.

Nanocellulose is the smallest crystalline particle consisting of cellulose with typical sizes of widths from 2 nm - 50 nm and lengths from 100 nm - 5000 nm. These sizes would result in aspect ratios (length divided by width) from 2 to 2500, with typical aspect ratios of a few hundred. The nanocellulose can be functionalized by the addition of surface charge, for example by TEMPO oxidation, carboxymethylation, phosphorylation, sulfonation or cationization. The functionalization can make the nanocellulose possible to coagulate. CNF, CNC, homogenization.

Due to the high aspect ratios of the nanocellulose, the nanocellulose entangle and for aggregates at low concentrations. When the nanocellulose is in an aggregated state, the individual nanocellulose particles are too entangled to align, therefore, the spinning of the nanocellulose should be performed at a low enough concentration. This concentration is directly related to the aspect ratio and the crowding factor. The dispersion liquid may have a crowding number in the range of 10 to 100.

The concentration of cellulose nanofibers may be between 0.1 and 0.9 wt%. The concentration of cellulose nanocrystals may be between 0.1 to 10 wt% or 1 to 6wt%, or 0.9 to 2.5 wt%, or 2.5 to 10 wt%. Weight percentage or wt% is a percentage of the total weight of the liquid.

The fibrous mat produced in accordance with the invention comprises long-chained polymer(s) and/or non-spherical particles. The mat comprises continuous fibers (aspect ratio < 5 000) of the cellulose crystal structure. The mat comprises thin fibers with a diameter of preferably 5 to 20 pm (3 to 50 pm, 1 to 100 pm), with a high degree of cellulose alignment and tunable joint adhesion. The fibrous mat may be carbonized.

Experimental

The liquid droplet can be drained at the reaction chamber exit by suction. As an example of suction, a hole/outlet 8 was positioned at the reaction chamber exit. A hose 3 and a suction pump were connected to the hole 8. By adjusting the pump speed, the liquid 5 in the droplet could be held constant and the wet thread 6 was continuously extracted, see Fig. 9.

The liquid at the reaction chamber outlet 8 can be transferred to a collector surface 7 by placing the liquid 5 in contact with the surface. In one example shown in fig. 8, the wet thread 6 also attached to the surface and was pulled out of the liquid at the reaction chamber outlet 8, see Fig. 8.

The liquid droplet will detach from the reaction chamber outlet when the liquid droplet 10 is heavier than the surface tension can hold. The droplet will then bring the wet thread 6 with it but will only tare the wet thread apart if the droplet falls far enough, see Fig. 7.

The time between drops of the liquid at the exit can be tuned by the wetting, angle, and size of the surface at the reaction chamber exit. For example, a small area will lead to a short time between drops falling and a larger area will increase the time. As seen in Fig. 10 larger droplets 10a are formed on the left side due to large surface area to attach to, while smaller droplets 10b are formed on the right side due to smaller surface area to attach to.

The reaction chamber exit has been placed in a water bath and the wet thread placed between two vertical pins by moving the reaction chamber exit from one pin to the other. The process is seen in Fig 6 where the reaction chamber is submerged in water and the wet thread is flowing out of the reaction chamber exit can be seen on the left side of the reaction chamber as the reaction chamber is moving from left to right in the pictures.

The adhesion between two dry fibers in the mat can be tuned by tuning the water content of the wet threads when they are placed in contact with each other. For example, if a wet thread is placed on a dry fiber the wet thread will stick to a large surface of the dry fiber and an intersection seen in upper two pictures in Fig. 4. If a drier wet thread, in this case one that has been allowed to dry for 150 s, is placed on a dry fiber, the intersection is different as is seen in the lower two pictures in Fig. 4.

Different material has been demonstrated to work in the invention. TEMPO-oxidized CNFs with 1100 peqv/g which was homogenized four times at 1% at 1700 bar was tested and observed to work at both 0.3% and 0.25%.

A few different variations of carboxymethylated CNFs have also been proven to work. The charge has been both 1000 peqv/g and 580 peqv/g, a varying number of homogenizationpasses from 2 to 4 times as well as concentrations run at 0.3%, 0.25% and 0.2% was tested.

HCI at pH 2 has been tested as coagulation liquid. The flow rate of the dispersion was 0.2-2 ml/min and the coagulation liquid was 0.5-10 ml/min. In one experiment, the outlet was moved at speeds between 3 m/min and 10 m/min, while a fibre was placed on a frame. In another experiment the frame was moved in z-direction and the nozzle was moved in the x- direction.

A rotating wheel has been used to provide attachment points for the the wet thread. The material of the attachment points have been tested to be aluminum, steel, PLA, Teflon and nylon.

Fabrics can be produced when mats are stacked. The fiber alignment can be adjusted during the stacking, two examples are, firstly to place all fibers in the same direction (uni-directional) and secondly when the fibers are placed at a 90-degree angle (bi-directional) , see figure Fig 11a and Fig lib.

The length of the hose has been varied between 1 cm and 150 cm.

The drying time is related to the thickness of the wet thread, ranging from 3-20 min. When heat and air convection is added, the drying times are decreased to 1-4 minutes. Please add further experimental data you may have, e.g. strength data, drying times, flow speed differences, etc...

The present invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.

Claims

1. A method for producing a structured fibrous mat, comprising the following steps: a) injecting a dispersion comprising polymer(s) and/or non-spherical particles in a suitable liquid into a reaction chamber (4) comprising at least an inlet (9) and an outlet (8), b) coagulating the dispersion into a continuous wet thread (6) in the reaction chamber by the introduction of a co-flowing coagulation liquid into the reaction chamber (4), c) separating the liquid (5) from the continuous wet thread (6) at the reaction chamber outlet (8), d) positioning the coagulated thread at the reaction chamber outlet between at least two attachment points on or into a solid, liquid or gas collector (7) thereby allowing for the generation of a weave at the reaction chamber outlet and controlling the geometry of the fibrous mat, and e) optionally, drying the produced mat.

2. The method according to claim 1, wherein the polymer(s) and/or non-spherical particles are selected from the group comprising nanocellulose, polymeric proteins, metal nano-rods and non-spherical carbon particles.

3. The method according to claim 1 or 2, wherein the suitable liquid used in step a) is selected from the group comprising water, acid solutions, organic solvents and ionic liquids, or mixtures thereof.

4. The method according to any one of the preceding claims, wherein the dispersion liquid of step a) has a crowding number in the range of 10 to 100.

5. The method according to any one of the preceding claims, wherein the dispersion liquid further comprises one or more components selected from the group comprising conductive polymers, alginate thermoset polymers, thermoplastic polymers, biopolymers, conductive polymers, epoxy polymers, epoxy particles, polymer nanoparticles, polymer microparticles, metal nanoparticles, metal microparticles, carbon nanoparticles, carbon microparticles, magnetic nanoparticles, magnetic microparticles, clay particles and living cells.

6. The method according to any one of the preceding claims, wherein the dispersion liquid further comprises one or more components selected from the group comprising of clay particles, conductive polymers and alginate.

7. The method according to any one of the preceding claims, wherein the coagulation liquid in step b) is selected from the group comprising one or more acid, salt, and organic solvents.

8. The method according to any one of the preceding claims, wherein the coagulation liquid is one or more organic or inorganic acids selected from the group comprising hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, boric acid, acetic acid and citric acid, or the coagulation liquid is one or more salts selected from the group comprising Na⁺, Ca²⁺, Fe²⁺, Fe³⁺, Mg²⁺, K⁺, Cu²⁺ and one anion such as Cl’, NO^-3, NO^-2, PCU³’, SCh²’, F and COa²’, or the coagulation liquid is an organic solvent selected from the group comprising ethanol, acetone, butanol and isopropanol.

9. The method according to any one of the preceding claims, wherein the volume ratio in step b) of dispersion liquid to coagulation liquid is 0.5: 50.

10. The method, according to any one of the preceding claims, wherein the coagulation time is extended by attaching a flexible tube to the one or more chamber outlets (8), which extends a coflowing period of the dispersion liquid from step a) and the coagulation liquid from step b).

11. The method according to any one of the preceding claims, wherein the separation in step c) is achieved by pulling the thread out of the liquid, sucking, or blowing away the liquid at the reaction chamber outlet (8), such as a nozzle, using liquid absorbing material, controlling the wetting properties of the reaction chamber outlet, or by using electrostatics forces at said outlet.

12. The method according to any one of the preceding claims, wherein the concentration of the gel threads at the time of forming the weave is <10wt%, or <5wt% or <3wt%, wherein weight percentages (wt%) is a percentage of the total weight of the mass present in the chamber.

13. The method according to any one of the preceding claims, wherein the flowing speed of the dispersion liquid from step a) and the coagulation liquid from step b) through the reaction chamber are the same or similar and have a maximum difference in flow speed of 10% or less.

14. The method according to any one of the preceding claims, wherein method step d) is automated or the whole method is automated.

15. The method according to any one of the preceding claims, wherein the method comprises a further step to be performed after step d) or step e) comprising of a post -treatment of the obtained mat selected from the group comprising crosslinking, surface modification, carbonization, and addition of further material, such as a coating.

16. The method according to any one of the preceding claims, wherein the obtained mat is two-dimensional or wherein the obtained mat is three-dimensional.

17. A system adapted to perform the method according to any one of the preceding claims, comprising a first container (1) comprising the dispersion liquid, and a second container (1) comprising the coagulation liquid, hoses (3) adapted to transport the liquid from the containers into a reaction chamber (4) having an inlet (9) and an outlet (8), whereby the non-coagulated liquid (5) is removed at the outlet (8) and a wet thread (6) is collected on a collector (7).

18. The system according to claim 17, wherein the angle (a) between the outlet (extending substantially in the direction of the y-axis) and the surface of the collector (extending substantially in the direction of the x-axis) is between 90 and 5°.