High-strength cellulose fiber as well as preparation method and application thereof

Abstract

The invention relates to the technical field of natural polymer material processing, in particular to a high-strength cellulose fiber and a preparation method and application thereof, and the preparation method comprises the following steps: preparing a solvent from an alkaline aqueous solution and a stabilizer to dissolve cellulose, defoaming and filtering to obtain a cellulose spinning solution; the cellulose spinning solution is regenerated in a salting-out bath after being extruded, and a carbonate solution or a mixed salt solution of carbonate and sulfate is selected as the salting-out bath; washing, oiling and drying the regenerated product to obtain the high-strength cellulose fiber. According to the method disclosed by the invention, the salt solution is adopted as a salting-out bath, so that the safety and the stability of the fiber preparation process are greatly improved, and the damage of volatile gases of acids and alcohols to body health, the damage of instruments and equipment and the risk of safety accidents are avoided. The cellulose fiber prepared by the method is excellent in mechanical property, simple in preparation process, convenient to mix with various functional fillers, biodegradable and wide in application prospect as an environment-friendly material.

Description

Technical Field

[0001] The invention relates to the technical field of natural polymer material processing, and in particular to high-strength cellulose fiber, a preparation method and application thereof. Background Art

[0002] Cellulose is the most abundant natural biopolymer and renewable resource in nature. It has excellent biocompatibility, biodegradability and outstanding mechanical properties. It has been widely studied and applied in various fields such as papermaking, medicine, environmental engineering and new material construction. Regenerated cellulose fiber has a long history. The viscose method and the cuprammonia method are mainly used in the industry to produce regenerated cellulose fiber. However, these two methods will produce a large number of toxic by-products during the production process, which seriously endangers human health and pollutes the environment. In addition, Lyocell fibers prepared using N-methylmorpholine-N-oxide have problems such as expensive solvents and difficult recycling.

[0003] In order to achieve green and environmental protection, low-cost preparation of regenerated cellulose fibers with ideal properties, many coagulation bath systems have been developed using alkali systems as solvent systems. However, regenerated cellulose fibers prepared by traditional alkali systems almost all use alcohol aqueous solution, acid aqueous solution or mixed aqueous solution of acid and its salt as coagulation bath. Alcohols are highly volatile as organic reagents. A large amount of volatile gas will seriously damage health after being inhaled by the human body. In addition, there is a large loss during the regeneration process, and the reuse rate is poor. More importantly, alcohols are flammable, and a large amount of coagulation bath is a safety hazard that cannot be ignored. Acids will react with the alkali in the solvent component to neutralize, consume the solvent and regenerate the fiber. Various acids are significantly corrosive and toxic, which will not only greatly shorten the service life of the equipment, but also cause serious damage once splashed on the skin. At the same time, the large amount of heat released by the neutralization reaction will cause continuous temperature fluctuations during the regeneration process, reduce the concentration of the coagulation bath and change the composition of the coagulation bath, making the coagulation bath unable to be recycled, which invisibly increases the difficulty and cost of recycling the coagulation bath. Summary of the invention

[0004] One of the objectives of the present invention is to provide a method for preparing high-strength cellulose fibers, which uses a salting-out bath for fiber regeneration. Inorganic salt ions with strong salting-out effects can polarize the hydrated water molecules around the cellulose molecular chains, disrupt the hydrogen bond interaction between the cellulose molecular chains and their hydrated water molecules, interfere with the hydrophobic interaction of the cellulose molecular chains, cause water molecules to be discharged from between the cellulose molecular chains, enhance the interaction between the hydroxyl groups on the cellulose backbone, lead to the lateral aggregation of cellulose molecular chains, and increase the number of hydrogen bonds between cellulose chains and the fiber crystallinity. The salting-out effects of carbonate ions and / or sulfate ions are particularly intense, and the solubility of carbonates at low temperatures is higher than that of sulfates. Therefore, a carbonate solution or a mixed salt solution of carbonate and sulfate can be used to successfully prepare a low-temperature, high-concentration, strong salting-out solution, which is beneficial to the efficient and rapid production of high-strength cellulose fibers.

[0005] Another objective of the present invention is to provide a high-strength cellulose fiber.

[0006] A further objective of the present invention is to provide an application of the high-strength cellulose fiber.

[0007] The solution adopted by the present invention to achieve the first objective is: a method for preparing high-strength cellulose fibers, comprising the following steps:

[0008] (1) Using an alkaline aqueous solution and a stabilizer to prepare a solvent to dissolve cellulose, and obtaining a cellulose spinning dope after defoaming and filtration;

[0009] (2) After the cellulose spinning dope is extruded, it is regenerated in a salting-out bath, and the salting-out bath is selected from a carbonate solution or a mixed salt solution of carbonate and sulfate;

[0010] (3) The regenerated product is washed with water, oiled, and dried to obtain high-strength cellulose fibers.

[0011] Preferably, in step (1), the solvent is precooled to -20 to 0 °C and then cellulose is added, and it can be completely dissolved after high-speed stirring.

[0012] Preferably, in step (1), the alkali used is at least one of lithium hydroxide and sodium hydroxide, and the concentration of the alkali in the solvent is 3 wt% to 12 wt%.

[0013] Preferably, in step (1), the concentration of the stabilizer in the solvent is 0 to 20 wt%, and the stabilizer is at least one of urea and thiourea.

[0014] Preferably, in step (1), the concentration of cellulose in the cellulose spinning dope is 2 wt% to 12 wt%.

[0015] Preferably, in step (2), the salting-out bath is a single salting-out bath or a multi-stage salting-out bath.

[0016] Preferably, in step (2), the total concentration of salt in the salting-out bath is 5 wt% to 60 wt%, carbonates and sulfates are selected from potassium salts, sodium salts, lithium salts, and ammonium salts, and the salting-out bath is prepared in any proportion within the solubility range of the salts.

[0017] Preferably, in step (2), the temperature of the coagulation bath is -15 to 20°C.

[0018] The technical solution adopted by the present invention to achieve the second purpose is: a high-strength cellulose fiber is prepared by the method described.

[0019] The technical solution adopted by the present invention to achieve the third purpose is: application of high-strength cellulose fiber, the cellulose fiber is prepared by the method described, and the cellulose fiber is applied to clothing manufacturing, medical textiles, and electrical materials.

[0020] Salt solution has long-term stability, is less volatile than organic reagents, and has more advantages in safety and price than acids. The regeneration mechanism of salt solution is different from that of alcohol and acid. Inorganic salt ions with strong salting-out effect, such as carbonate and sulfate ions, can polarize the hydrated water molecules around the cellulose molecular chain, destroy the hydrogen bond interaction between the cellulose molecular chain and its water and water molecules, interfere with the hydrophobic interaction of the cellulose molecular chain, and cause water molecules to be discharged from the cellulose molecular chain, thereby enhancing the interaction between the hydroxyl groups on the cellulose skeleton, leading to the lateral aggregation and recrystallization of the cellulose molecular chain, and forming dense and uniform nanofibers. The higher the ion concentration, the more intense the salting-out effect. The concentration of the salt solution plays an important role in the molding speed and mechanical properties of the fiber. Key role; published research papers have shown that in the gelation process of cellulose solution dissolved in alkali / urea at higher temperatures, hydrophobic aggregation is dominant, and cellulose nanofibers gradually wrap and aggregate to form nanofiber aggregates, resulting in a decrease in the mechanical properties of the material. Therefore, low-temperature salt solution is more conducive to reducing hydrophobic aggregation, promoting the formation of interchain hydrogen bonds and effectively inhibiting the generation of water vapor, ensuring the accuracy of the salting-out bath concentration during the preparation process; due to the reaction inertness of the salt solution and the solvent, the residual solvent in the salting-out bath can be separated from the salt by evaporation and crystallization process, and the recovered components can continue to be used to prepare the solvent and salting-out bath, and can be recycled many times without changing the properties of the salting-out bath, while saving a lot of costs, it also potentially reduces carbon emissions.

[0021] The present invention relates to a method for preparing high-strength cellulose fibers using a salt solution as a salting-out bath. The carbonate or sulfate ions in the solution can polarize the hydrated water molecules around the cellulose molecular chain, interfere with the hydrophobic interaction of the cellulose molecular chain, enhance the number and density of hydrogen bonds between the cellulose skeletons, promote the lateral aggregation and recrystallization of the cellulose molecular chain, and the solvent does not chemically react with the components of the salting-out bath, greatly improving the feasibility and stability of continuously preparing fibers in the salting-out bath for a long time, and also reducing the difficulty and cost of recovering the solvent and the salting-out bath.

[0022] The present invention has the following advantages and beneficial effects:

[0023] (1) Compared with the alcohol and acid components in the traditional salting-out bath, the method of the present invention using a salt solution as the salting-out bath greatly improves the safety and stability in the process of preparing fibers, avoiding the damage to physical health caused by the volatile gases of acids and alcohols, the damage to instrument equipment, and the risk of safety accidents.

[0024] (2) The salting-out bath in the method of the present invention has low recovery difficulty and low recovery cost. The solvent does not chemically react with the salt, ensuring the stability of the components and concentration of the salting-out bath, maximizing the consistency in the fiber preparation process, and greatly improving the economic benefits of fiber preparation.

[0025] (3) In the method of the present invention, the inorganic salt ions in the salt solution can polarize the hydrated water molecules around the cellulose molecular chain, destroy the hydrogen bond interaction between the cellulose molecular chain and its hydrated water molecules, interfere with the hydrophobic interaction of the cellulose molecular chain, cause the water molecules to be discharged from between the cellulose molecular chains, enhance the interaction between the hydroxyl groups on the cellulose skeleton, resulting in the lateral aggregation and recrystallization of the cellulose molecular chain, promoting the formation of nanofibers, significantly improving the mechanical properties of the fibers, and enabling the rapid, efficient, and long-term continuous preparation of high-strength fibers.

[0026] (4) In the method of the present invention, the temperature of the salt solution is controlled below room temperature to inhibit the hydrophobic aggregation of cellulose and water evaporation, which can improve the mechanical properties of the fibers and maintain the stability of the concentration of the salting-out bath.

[0027] (5) The cellulose fibers prepared by the method of the present invention have excellent mechanical properties, a simple preparation process, are easy to incorporate various functional fillers, are biodegradable, and have broad application prospects as environmentally friendly materials. Description of the Drawings

[0028] Figure 1 It is a scanning electron micrograph of the cross-section of the cellulose fiber prepared in Example 2;

[0029] Figure 2 It is a scanning electron micrograph of the surface of the cellulose fiber prepared in Example 2. Detailed Embodiments

[0030] For a better understanding of the present invention, the following examples further illustrate the present invention, but the content of the present invention is not limited to the following examples.

[0031] <Example 1>

[0032] Prepare an aqueous solution of LiOH at a concentration of 3 wt% and urea at 15 wt%. After pre-cooling to 0 °C, add cellulose. After high-speed stirring, a cellulose solution with a final concentration of 2 wt% is obtained. The cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters a 35 wt% K2CO3 solution at 0 °C for primary regeneration. After passing through a stretching unit with a draw ratio of 1.1, it is immersed in a second 5 wt% K2CO3 solution at 0 °C, and then enters a washing unit after passing through a second stretching unit with a draw ratio of 1.2. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 8% and 50.1 MPa respectively.

[0033] <Example 2>

[0034] Prepare an aqueous solution of LiOH / NaOH at concentrations of 2.5 wt% / 3.5 wt% and urea at 10 wt%. After pre-cooling to -10 °C, add cellulose raw materials. After high-speed stirring, a cellulose solution with a final concentration of 6 wt% is obtained. The cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters a 50 wt% K2CO3 solution at 0 °C for primary regeneration. After passing through a stretching unit with a draw ratio of 1.1, it enters a washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 27% and 151.2 MPa respectively.

[0035] Figure 1 The figure shows a scanning electron micrograph of the cross-section of the cellulose fibers prepared in Example 2; Figure 2 The figure shows a scanning electron micrograph of the surface of the cellulose filaments prepared in Example 2. It can be seen from the figure that the fiber regeneration is uniform and the surface is flat; the internal pore structure is dense and the nanofibers are arranged orderly.

[0036] <Example 3>

[0037] Prepare aqueous solutions of LiOH / NaOH with concentrations of 6 wt% / 3 wt% respectively, pre-cool to -15 °C, add the cellulose raw material, and obtain a cellulose solution with a final concentration of 8 wt% after high-speed stirring. The cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters a 40 wt% K2CO3 solution at -15 °C for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is then immersed in a second 20 wt% K2CO3 solution at -15 °C. After passing through a second drawing unit with a draw ratio of 1.1, it enters the washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 21% and 204.5 MPa respectively.

[0038] <Example 4>

[0039] Prepare aqueous solutions of LiOH / urea with concentrations of 12 wt% / 20 wt% respectively, pre-cool to -20 °C, add the cellulose raw material, and obtain a cellulose solution with a final concentration of 12 wt% after high-speed stirring. The cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters a 20 wt% K2CO3 solution at -15 °C for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.3, it is then immersed in a second 7 wt% Na2CO3 solution at 5 °C. After passing through a second drawing unit with a draw ratio of 1.4, it enters the washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 15% and 267.1 MPa respectively.

[0040] <Example 5>

[0041] Prepare aqueous solutions of LiOH / thiourea with concentrations of 7 wt% / 12 wt% respectively, pre-cool to -20 °C, add the cellulose raw material, and obtain a cellulose solution with a final concentration of 7 wt% after high-speed stirring. The cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters a 45 wt% K2CO3 solution at 15 °C for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.2, it is then immersed in a second 60 wt% mixed salt (45 wt% K2CO3 / 15 wt% Na2CO3) solution at 20 °C. After passing through a second drawing unit with a draw ratio of 1.3, it passes through the washing unit. After being washed clean, it passes through a third drawing unit with a draw ratio of 1.1, and then is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 17% and 266.1 MPa respectively.

[0042] <Example 6>

[0043] Prepare aqueous LiOH / urea solutions with concentrations of 7.5 wt% / 12 wt% respectively. After pre-cooling to -15 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 8 wt% after high-speed stirring. This cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters the first 5 °C 25 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Li2SO4) solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is then immersed in the second 10 °C 43 wt% mixed salt (35 wt% K2CO3 / 8 wt% Na2SO4) solution. After passing through the second drawing unit with a draw ratio of 1.2, it passes through the third 15 °C 25 wt% K2CO3 solution. Finally, after passing through the third drawing unit with a draw ratio of 1.1, it enters the washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of this regenerated cellulose fiber are 15% and 345.6 MPa respectively.

[0044] <Example 7>

[0045] Prepare aqueous LiOH / urea solutions with concentrations of 3 wt% / 20 wt% respectively. After pre-cooling to 0 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 5 wt% after high-speed stirring. This cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters the 20 °C 10 wt% mixed salt (5 wt% Na2CO3 / 5 wt% Na2SO4) solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is immersed in the second 0 °C 5 wt% Na2CO3 solution. After passing through the second drawing unit with a draw ratio of 1.1, it passes through the washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of this regenerated cellulose fiber are 20% and 147.3 MPa respectively.

[0046] <Example 8>

[0047] Prepare aqueous LiOH / thiourea solutions with concentrations of 4 wt% / 20 wt% respectively. After pre-cooling to 0 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 6 wt% after high-speed stirring. This cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters the 5 °C 10 wt% mixed salt (5 wt% Li2CO3 / 5 wt% Li2SO4) solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is immersed in the second 2.5 °C 7 wt% Li2CO3 solution. After passing through the second drawing unit with a draw ratio of 1.1, it passes through the washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of this regenerated cellulose fiber are 24% and 149.8 MPa respectively.

[0048] <Example 9>

[0049] Prepare an aqueous solution of LiOH / NaOH with a concentration of 5 wt% / 4 wt%, pre-cool it to 0 °C, add the cellulose raw material, and obtain a cellulose solution with a final concentration of 5.5 wt% after high-speed stirring. After centrifugal defoaming and filtration of the cellulose solution, wet spinning is carried out. The extruded spinning dope first enters a 5 °C 15 wt% mixed salt (10 wt% K2CO3 / 5 wt% K2SO4) solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is immersed in a second 0 °C 25 wt% K2CO3 solution, and then after passing through a second drawing unit with a draw ratio of 1.3, it passes through a water washing unit. After that, it passes through a third 15 °C 32.5 wt% (27.5 wt% K2CO3 / 5 wt% K2SO4) mixed solution and then through a third drawing unit with a draw ratio of 1.4 and enters the water washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 12% and 197.6 MPa respectively.

[0050] <Example 10>

[0051] Prepare an aqueous solution of LiOH / NaOH / urea with concentrations of 6 wt% / 5 wt% / 25 wt%, pre-cool it to 0 °C, add the cellulose raw material, and obtain a cellulose solution with a final concentration of 8 wt% after high-speed stirring. After centrifugal defoaming and filtration of the cellulose solution, wet spinning is carried out. The extruded spinning dope first enters a -5 °C 30 wt% mixed salt (15 wt% K2CO3 / 15 wt% (NH4)2SO4) solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.2, it is immersed in a second 0 °C 5 wt% Na2CO3 solution, and then after passing through a second drawing unit with a draw ratio of 1.4, it passes through a water washing unit. Then it enters the water washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 17% and 211.8 MPa respectively.

[0052] <Example 11>

[0053] Prepare aqueous solutions of LiOH / NaOH and urea with concentrations of 4 wt% / 4 wt% and 15 wt% respectively, pre-cool it to -10 °C, add the cellulose raw material, and obtain a cellulose solution with a final concentration of 4.5 wt% after high-speed stirring. After centrifugal defoaming and filtration of the cellulose solution, wet spinning is carried out. The extruded spinning dope first enters a -10 °C 25 wt% K2CO3 solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it passes through a water washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 24% and 107.3 MPa respectively.

[0054] <Example 12>

[0055] Prepare an aqueous solution of LiOH / NaOH with concentrations of 6 wt% / 6 wt% respectively. After pre-cooling to -15°C, add the cellulose raw material and obtain a cellulose solution with a final concentration of 5 wt% through high-speed stirring. After centrifugal defoaming and filtration of this cellulose solution, wet spinning is carried out. The extruded spinning dope first enters a 30 wt% K2CO3 solution at -10°C for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is then immersed in a second 25 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Na2SO4) solution at 40°C. After passing through a second drawing unit with a draw ratio of 1.3, it passes through a water washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of this regenerated cellulose fiber are 22% and 172.4 MPa respectively.

[0056] <Example 13>

[0057] Prepare an aqueous solution of NaOH / urea with concentrations of 9 wt% / 15 wt% respectively. After pre-cooling to -20°C, add the cellulose raw material and obtain a cellulose solution with a final concentration of 7 wt% through high-speed stirring. After centrifugal defoaming and filtration of this cellulose solution, wet spinning is carried out. The extruded spinning dope first enters a 25 wt% mixed salt (20 wt% K2CO3 / 5 wt% Na2CO3) solution at -15°C for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.3, it is then immersed in a second 25% mixed salt (20 wt% K2CO3 / 5 wt% Na2CO3) solution at -15°C. After passing through a second drawing unit with a draw ratio of 1.3, it passes through a water washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of this regenerated cellulose fiber are 16% and 233.4 MPa respectively.

[0058] <Example 14>

[0059] Prepare aqueous solutions of LiOH / urea with concentrations of 7 wt% / 12 wt% respectively, pre-cool to -20 °C, add cellulose raw materials, and obtain a cellulose solution with a final concentration of 7 wt% after high-speed stirring. This cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters a 10 °C 25 wt% mixed salt (15 wt% K2CO3 / 10 wt% Na2SO4) solution for preliminary regeneration. After passing through a stretching unit with a draw ratio of 1.2, it is then immersed in a second 10 °C 40 wt% mixed salt (30 wt% K2CO3 / 10 wt% Na2CO3) solution. After passing through a second stretching unit with a draw ratio of 1.4, it passes through a water washing unit. After being washed clean, it passes through a third stretching unit with a draw ratio of 1.1, and then through oiling and drying to obtain high-strength cellulose fibers. The elongation at break and breaking strength of this regenerated cellulose fiber are 13% and 219.2 MPa respectively.

[0060] <Example 15>

[0061] Prepare aqueous solutions of LiOH / NaOH, urea with concentrations of 7.5 wt% / 5 wt% and 12 wt% respectively, pre-cool to -15 °C, add cellulose raw materials, and obtain a cellulose solution with a final concentration of 6 wt% after high-speed stirring. This cellulose solution is centrifuged to remove air bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters a first 15 °C 25 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Li2SO4) solution for preliminary regeneration. After passing through a stretching unit with a draw ratio of 1.2, it is then immersed in a second 15 °C 25 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Li2SO4) solution. After passing through a second stretching unit with a draw ratio of 1.2, it passes through a third 15 °C 25 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Li2SO4) solution. After passing through a third stretching unit with a draw ratio of 1.2, it enters a water washing unit. After being washed clean, it passes through oiling and drying to obtain high-strength cellulose fibers. The elongation at break and breaking strength of this regenerated cellulose fiber are 12% and 210.4 MPa respectively.

[0062] <Example 16>

[0063] Prepare aqueous LiOH / urea solutions with concentrations of 7.5 wt% / 12 wt% respectively. After pre-cooling to -15 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 8 wt% through high-speed stirring. Add 5 wt% of hexagonal boron nitride powder to the solution. After centrifugal defoaming and filtration of the cellulose solution, wet spinning is carried out. The extruded spinning dope first enters the first 5 °C 45 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Li2SO4) solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is then immersed in the second 10 °C 43 wt% mixed salt (35 wt% K2CO3 / 8 wt% Na2SO4) solution. After passing through a second drawing unit with a draw ratio of 1.2, it passes through the third 15 °C 25 wt% K2CO3 solution. Finally, after passing through a third drawing unit with a draw ratio of 1.1, it enters the water washing unit. After being washed clean, it is oiled and dried to obtain boron nitride / cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 12% and 415.6 MPa respectively.

[0064] <Example 17>

[0065] Prepare aqueous LiOH / urea solutions with concentrations of 7.5 wt% / 12 wt% respectively. After pre-cooling to -15 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 8 wt% through high-speed stirring. Add 5 wt% of nano-silica powder to the solution. After centrifugal defoaming and filtration of the cellulose solution, wet spinning is carried out. The extruded spinning dope first enters the first 5 °C 25 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Li2SO4) solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is then immersed in the second 10 °C 43 wt% mixed salt (35 wt% K2CO3 / 8 wt% Na2SO4) solution. After passing through a second drawing unit with a draw ratio of 1.2, it passes through the third 15 °C 25 wt% K2CO3 solution. Finally, after passing through a third drawing unit with a draw ratio of 1.1, it enters the water washing unit. After being washed clean, it is oiled and dried to obtain nano-silica / cellulose fibers. The elongation at break and tensile strength of the regenerated cellulose fibers are 11% and 439.1 MPa respectively.

[0066] <Example 18>

[0067] Prepare aqueous LiOH / urea solutions with concentrations of 7.5 wt% / 12 wt% respectively. After pre-cooling to -15 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 8 wt% through high-speed stirring. Add 5 wt% of graphene oxide powder to the solution. The cellulose solution is centrifuged to remove bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters the first 5 °C 25 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Li2SO4) solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is then immersed in the second 10 °C 43 wt% mixed salt (35 wt% K2CO3 / 8 wt% Na2SO4) solution. After passing through a second drawing unit with a draw ratio of 1.2, it passes through the third 15 °C 25 wt% K2CO3 solution. Finally, after passing through a third drawing unit with a draw ratio of 1.1, it enters the water washing unit. After being washed clean, it is oiled and dried to obtain graphene oxide / cellulose fibers. The elongation at break and breaking strength of the regenerated cellulose fibers are 11%, 478.9 MPa respectively.

[0068] <Example 19>

[0069] Prepare aqueous LiOH / urea solutions with concentrations of 7.5 wt% / 12 wt% respectively. After pre-cooling to -15 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 8 wt% through high-speed stirring. Add 5 wt% of carbon nanotubes to the solution. The cellulose solution is centrifuged to remove bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters the first 5 °C 25 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Li2SO4) solution for preliminary regeneration. After passing through a drawing unit with a draw ratio of 1.1, it is then immersed in the second 10 °C 43 wt% mixed salt (35 wt% K2CO3 / 8 wt% Na2SO4) solution. After passing through a second drawing unit with a draw ratio of 1.2, it passes through the third 15 °C 25 wt% K2CO3 solution. Finally, after passing through a third drawing unit with a draw ratio of 1.1, it enters the water washing unit. After being washed clean, it is oiled and dried to obtain carbon nanotube / cellulose fibers. The elongation at break and breaking strength of the regenerated cellulose fibers are 12%, 447.7 MPa respectively.

[0070] <Example 20>

[0071] Prepare aqueous LiOH / urea solutions with concentrations of 7.5 wt% / 12 wt% respectively. After pre-cooling to -15 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 8 wt% after high-speed stirring. Add 5 wt% of ZIF-8 type metal-organic framework material (MOFs) to the solution. The cellulose solution is centrifuged to remove bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters the first 5 °C 25 wt% mixed salt (10 wt% Na2CO3 / 15 wt% Li2SO4) solution for preliminary regeneration. After passing through a stretching unit with a draw ratio of 1.1, it is then immersed in the second 10 °C 43 wt% mixed salt (35 wt% K2CO3 / 8 wt% Na2SO4) solution. After passing through a second stretching unit with a draw ratio of 1.2, it passes through the third 15 °C 25 wt% K2CO3 solution. Finally, after passing through a third stretching unit with a draw ratio of 1.1, it enters the washing unit. After washing clean, it is oiled and dried to obtain MOFs / cellulose fibers. The elongation at break and breaking strength of the regenerated cellulose fibers are 14% and 403.1 MPa respectively.

[0072] <Comparative Example 1>

[0073] Prepare aqueous LiOH / thiourea solutions with concentrations of 7 wt% / 12 wt% respectively. After pre-cooling to -20 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 7 wt% after high-speed stirring. The cellulose solution is centrifuged to remove bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters the first 0 °C 45 wt% NaBr solution for preliminary regeneration. After passing through a stretching unit with a draw ratio of 1.1, it enters the washing unit. After washing clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and breaking strength of the regenerated cellulose fibers are 19% and 75.1 MPa respectively.

[0074] <Comparative Example 2>

[0075] Prepare aqueous LiOH / thiourea solutions with concentrations of 7 wt% / 12 wt% respectively. After pre-cooling to -20 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 7 wt% after high-speed stirring. The cellulose solution is centrifuged to remove bubbles and filtered, and then wet spinning is carried out. The extruded spinning dope first enters the first 0 °C anhydrous ethanol solution for preliminary regeneration. After passing through a stretching unit with a draw ratio of 1.1, it passes through the second 0 °C 50 wt% ethanol aqueous solution and then enters the washing unit. Finally, after passing through a second stretching unit with a draw ratio of 1.1, it enters the washing unit. After washing clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and breaking strength of the regenerated cellulose fibers are 16% and 167.9 MPa respectively.

[0076] <Comparative Example 3>

[0077] Prepare aqueous LiOH / thiourea solutions with concentrations of 7 wt% / 12 wt% respectively. After pre-cooling to -20 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 7 wt% after high-speed stirring. This cellulose solution is subjected to centrifugal defoaming and filtration and then wet spinning. The extruded spinning dope first enters a 30 wt% KCl solution at 40 °C for preliminary regeneration, passes through a drawing unit with a draw ratio of 1.3, then enters a second 20 wt% KCl solution at 40 °C, and finally passes through a second drawing unit with a draw ratio of 1.2 and enters the water washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of this regenerated cellulose fiber are 12% and 109.5 MPa respectively.

[0078] <Comparative Example 4>

[0079] Prepare aqueous LiOH / thiourea solutions with concentrations of 7 wt% / 12 wt% respectively. After pre-cooling to -20 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 7 wt% after high-speed stirring. This cellulose solution is subjected to centrifugal defoaming and filtration and then wet spinning. The extruded spinning dope first enters a 20 wt% Na2SO4 solution at 30 °C for preliminary regeneration, passes through a drawing unit with a draw ratio of 1.2, then enters a second 15 wt% Na2SO4 solution at 20 °C, and finally passes through a second drawing unit with a draw ratio of 1.3 and enters the water washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of this regenerated cellulose fiber are 15% and 155.5 MPa respectively.

[0080] <Comparative Example 5>

[0081] Prepare aqueous LiOH / thiourea solutions with concentrations of 7 wt% / 12 wt% respectively. After pre-cooling to -20 °C, add cellulose raw materials and obtain a cellulose solution with a final concentration of 7 wt% after high-speed stirring. This cellulose solution is subjected to centrifugal defoaming and filtration and then wet spinning. The extruded spinning dope first enters a 35 wt% NaAc solution at 10 °C for preliminary regeneration, passes through a drawing unit with a draw ratio of 1.2, then enters a second 20 wt% NaAc solution at 10 °C, and finally passes through a second drawing unit with a draw ratio of 1.2 and enters the water washing unit. After being washed clean, it is oiled and dried to obtain high-strength cellulose fibers. The elongation at break and tensile strength of this regenerated cellulose fiber are 14% and 127.6 MPa respectively.

[0082] The above are the preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and changes can be made, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A method for preparing high-strength cellulose fibers, characterized in that, It includes the following steps: (1) Prepare a solvent by using an alkaline aqueous solution and a stabilizer to dissolve cellulose. After defoaming and filtration, a cellulose spinning dope is obtained; (2) The cellulose spinning dope is extruded and regenerated in a salting-out bath. The salting-out bath is selected from a carbonate solution or a mixed salt solution of carbonate and sulfate; (3) The regenerated product is washed with water, oiled, and dried to obtain high-strength cellulose fibers.

2. The method for preparing high-strength cellulose fibers according to claim 1, characterized in that: In the step (1), the solvent is precooled to -20 to 0 °C and then cellulose is added. After high-speed stirring, it can be completely dissolved.

3. The method for preparing high-strength cellulose fibers according to claim 1, characterized in that: In the step (1), the alkali used is at least one of lithium hydroxide and sodium hydroxide, and the concentration of the alkali in the solvent is 3 wt% to 12 wt%; the concentration of the stabilizer in the solvent is 0 to 20 wt%, and the stabilizer is at least one of urea and thiourea.

4. The method for preparing high-strength cellulose fibers according to claim 1, characterized in that: In the step (1), the concentration of cellulose in the cellulose spinning dope is 2 wt% to 12 wt%.

5. The method for preparing high-strength cellulose fibers according to claim 1, characterized in that: In the step (1), it further includes adding a functional filler to the cellulose solution to obtain a cellulose / functional filler composite solution. The functional filler is an organic or inorganic additive, including at least one of metal oxides, metal nitrides, graphene and its derivatives, carbon nanotubes and their derivatives, organic framework compounds, plasticizers, pore-forming agents, reinforcing agents, refractory additives, and dyes.

6. The method for preparing high-strength cellulose fibers according to claim 1, characterized in that: In the step (2), the salting-out bath is a single salting-out bath or a multi-stage salting-out bath.

7. The method for preparing high-strength cellulose fibers according to claim 1, characterized in that: In the step (2), the total concentration of salts in the salting-out bath is 5 wt% to 60 wt%. The carbonate and sulfate are arbitrarily selected from potassium salts, sodium salts, lithium salts, and ammonium salts, and the salting-out bath is prepared in any proportion within the solubility range of the salts.

8. The method for preparing high-strength cellulose fibers according to claim 1, characterized in that: In the step (2), the temperature of the coagulation bath is -15 to 20 °C.

9. A high-strength cellulose fiber, characterized in that: It is prepared by using the preparation method described in any one of claims 1 to 8.

10. An application of a high-strength cellulose fiber, characterized in that: The cellulose fiber is prepared by using the preparation method described in any one of claims 1 to 8, and the cellulose fiber is applied to clothing manufacturing, medical textiles, and electrical materials.

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