A method for improving the properties of regenerated lignocellulose fibers based on lignin degradation

Abstract

This invention belongs to the field of textile engineering technology and relates to a method for improving the performance of regenerated lignocellulose fibers based on lignin degradation. Corn stalks are mixed with an ionic liquid and tyrosine, then heated to dissolve, obtaining a spinning solution. The spinning solution is then subjected to wet spinning, and the spun fibers are solidified in a coagulation bath to obtain regenerated fibers. Compared with existing technologies, this invention uses corn stalks as the spinning raw material, which is widely available and inexpensive. Furthermore, this invention can achieve complete dissolution of the stalks and effectively remove lignin, reducing the lignin content in the regenerated fibers and improving their performance.

Description

Technical Field

[0001] This invention belongs to the field of textile engineering technology and relates to a method for improving the performance of regenerated lignocellulose fibers based on lignin degradation. Background Technology

[0002] Synthetic fibers, as important textile materials, are closely related to daily life, and their chemical industry plays a vital role in driving national economic development. However, as a significant petrochemical product, synthetic fibers are difficult to biodegrade, and their large-scale use places enormous pressure on the environment. With the increasing depletion of chemical resources, the shortage and rising prices of raw materials for synthetic polymer products pose a severe challenge to the country's textile industry. Developing natural fiber materials has become inevitable, and research in this direction is of considerable strategic significance.

[0003] Straw cellulose can compensate for insufficient cotton production and has significant applications in the spinning industry. However, straw usually contains high levels of lignin and other inorganic salt impurities, which cannot meet the requirements for spinning. Traditional lignocellulose spinning involves two steps: the first step is to purify the lignocellulose, removing non-cellulose impurities such as lignin; the second step is to spin the purified cellulose. Common purification processes include physical methods, chemical methods, and biomass methods. Before the second step of spinning, the purified cellulose needs to be dissolved. Commonly used dissolving systems include dimethyl sulfoxide / tetraethylammonium chloride (DMSO / TEAC) system, paraformaldehyde / dimethyl sulfoxide (PF / DMSO) system, nitrogen tetroxide / dimethylformamide (N2O4 / DMF(DMSO)) system, amine oxide system (NMMO), traditional viscose, copper amine and acetic acid systems, inorganic acid (H2SO4, HCl, H3PO4, HNO3) systems, and alkaline solvent systems. The aforementioned systems suffer from drawbacks such as the volatile and toxic nature of the chemical reagents used, complex processes, cellulose degradation during dissolution, and high equipment requirements, all of which necessitate improvement. For the sustainable development of the fiber industry, a more environmentally friendly technology for spinning lignocellulose is needed.

[0004] Ionic liquids (ILs) composed of cations and anions possess advantages such as tunable structure, low vapor pressure, and high thermal stability, making them novel green solvents, particularly suitable for dissolving natural polymers. Since Robin D. Rogers discovered in 2002 that [C4mim]Cl can efficiently dissolve cellulose, various room-temperature ILs with good cellulose-dissolving effects have been developed. Building on this, researchers have attempted to use ILs to dissolve lignocellulose biomass and spin it. However, relying solely on pure IL systems in a one-step process makes it difficult to obtain cellulose fibers with mechanical properties meeting practical requirements from lignocellulose. The key to solving this problem lies in achieving sufficient dissolution of lignocellulose while removing impurities such as lignin. A combination of ionic liquids and additives may enable a one-step process to obtain cellulose fibers with the required mechanical properties from lignocellulose. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing technology cannot simultaneously achieve the full dissolution of corn stalks and the removal of lignin from the stalks. The present invention provides a method for preparing regenerated fibers by selectively degrading lignin to achieve the full dissolution of corn stalks and then spinning them. This method achieves the full dissolution of the stalks while greatly reducing the lignin content in the regenerated fibers and improving the mechanical properties of the regenerated fibers.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] This invention discloses a method for improving the performance of regenerated lignocellulose fibers based on lignin degradation. Corn stalks are mixed with ionic liquid and tyrosine, and then heated to dissolve to obtain a spinning solution. The spinning solution is then subjected to wet spinning, and the resulting fibers are solidified in a coagulation bath to obtain regenerated fibers.

[0008] The tyrosine used in this invention is an auxiliary agent that selectively depolymerizes lignin at high temperatures while retaining cellulose.

[0009] In some embodiments, the ionic liquid is composed of anions and cations.

[0010] In some embodiments, the anion is a halide anion, preferably any one of chloride ion, bromide ion and iodide ion.

[0011] In some embodiments, the cation is any one of imidazole cation, pyridine cation, pyrrolidine cation, piperidine cation, and morpholine cation.

[0012] In some embodiments, preferably, the ionic liquid is any one or a combination of several of the following: 1-allyl-3-methylimidazolium chloride ionic liquid, N-allylpyridine chloride ionic liquid, N-allyl-N-methylpyrrolidine chloride ionic liquid, N-allyl-N-methylpiperidine chloride ionic liquid, N-allyl-N-methylmorpholine chloride ionic liquid, N-allylpyridine bromide ionic liquid, and N-allylpyridine iodide ionic liquid.

[0013] In some embodiments, the mass ratio of corn stalks to ionic liquid and tyrosine is 0.5:10.00:0.75 to 2.25.

[0014] In some embodiments, the heating and melting process is carried out at a heating temperature of 130°C to 145°C.

[0015] In some embodiments, the heating and dissolving process takes 10 to 16 hours.

[0016] In some embodiments, when the spinning solution is used for wet spinning, preferably, the spinning is performed at a speed of 2 mL / min when the temperature of the spinning solution is 60°C.

[0017] In some embodiments, the coagulation bath is an aqueous solution of an ionic liquid with a mass concentration of 0% to 20%.

[0018] In some embodiments, the ionic liquid is composed of anions and cations; the anion is a halide anion, preferably any one of chloride ions, bromide ions, and iodide ions; the cation is any one of imidazole cations, pyridine cations, pyrrolidine cations, piperidine cations, and morpholine cations.

[0019] In some embodiments, preferably, the ionic liquid is any one or a combination of several of the following: 1-allyl-3-methylimidazolium chloride ionic liquid, N-allylpyridine chloride ionic liquid, N-allyl-N-methylpyrrolidine chloride ionic liquid, N-allyl-N-methylpiperidine chloride ionic liquid, N-allyl-N-methylmorpholine chloride ionic liquid, N-allylpyridine bromide ionic liquid, and N-allylpyridine iodide ionic liquid.

[0020] In some embodiments, the temperature of the coagulation bath is 5°C to 25°C.

[0021] Beneficial effects:

[0022] (1) Compared with the prior art, the spinning raw material used in this invention is corn stalk, which is widely available and inexpensive; furthermore, this invention can achieve complete dissolution of straw and can better remove lignin, reduce the lignin content in regenerated fiber, and improve the performance of regenerated fiber.

[0023] (2) The improved method of the present invention can achieve the full dissolution of straw and the full removal of lignin from regenerated fibers through the synergistic effect of ionic liquid and tyrosine, and the regenerated fibers prepared have good mechanical properties. Attached Figure Description

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0025] Figure 1 This is a representative SEM image of the regenerated cellulose prepared in the embodiments of the present invention. Detailed Implementation

[0026] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as detailed in the claims.

[0027] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0028] The corn stalks used in this embodiment of the invention have a lignin content of approximately 19%.

[0029] Representative SEM images of the regenerated cellulose prepared in the embodiments of the present invention are shown below. Figure 1 As shown.

[0030] Example 1:

[0031] (1) Mix 0.50g of corn stalks and 10.00g of 1-allyl-3-methylimidazolium chloride ionic liquid in a glass tube reactor, then add 0.75g of tyrosine to the glass tube, and use an air heating block to heat the test tube to dissolve and prepare the spinning solution. The heating temperature is 145℃ and the heating time is 10h.

[0032] (2) Transfer the spinning solution obtained in step (1) to the spinneret of the spinning machine. The spinning solution temperature is 60℃ and it is extruded from the spinneret at a speed of 2mL / min. Use pure water at 5℃ as the coagulation bath and let the fiber stand in the coagulation bath. Replace the old water in the washing tank with new water every 12 hours. Repeat the replacement 5 times. Then, take out the fiber from the exchange tank with the winding roller and dry it at room temperature to obtain the regenerated fiber.

[0033] The regenerated fiber prepared in this embodiment has a lignin content of 1.33 wt%, a tensile strength of 342 MPa, and an elongation at break of 4.12%.

[0034] Example 2:

[0035] (1) Mix 0.50 g of corn stalks and 10.00 g of N-allylpyridinium chloride ionic liquid in a glass tube reactor. Then add 2.25 g of tyrosine to the glass tube to selectively degrade lignin, promote corn stalk dissolution and delignin removal. Use an air heating block to heat the test tube to prepare the spinning solution. The heating temperature is 130 °C and the heating time is 16 h.

[0036] (2) The spinning solution obtained in step (1) is transferred to the spinneret of the spinning machine. The spinning solution is 60°C and is extruded from the spinneret at a speed of 2 mL / min. A 10 wt% N-allylpyridine chloride aqueous solution at 5°C is used as the coagulation bath. The fiber is left to stand in the coagulation bath. The old coagulation bath in the washing tank is replaced with a new coagulation bath every 12 hours. After the replacement is repeated 5 times, the fiber in the exchange tank is taken out with a winding roller and dried at room temperature to obtain the regenerated fiber.

[0037] The regenerated fiber prepared in this embodiment has a lignin content of 1.23 wt%, a tensile strength of 405 MPa, and an elongation at break of 10.08%.

[0038] Example 3:

[0039] (1) Mix 0.50g of corn stalks and 10.00g of N-allyl-N-methylpyrrolidine chloride ionic liquid in a glass tube reactor, then add 0.75g of tyrosine to the glass tube, and use an air heating block to heat the test tube to dissolve and prepare the spinning solution. The heating temperature is 135℃ and the heating time is 16h.

[0040] (2) The spinning solution obtained in step (1) is transferred to the spinneret of the spinning machine. The spinning solution is 60°C and extruded from the spinneret at a speed of 2 mL / min. A 20 wt% N-allyl-N-methylpyrrolidine chloride aqueous solution at 10°C is used as the coagulation bath. The fiber is left to stand in the coagulation bath. The old coagulation bath in the washing tank is replaced with a new coagulation bath every 12 hours. After the replacement is repeated 5 times, the fiber in the exchange tank is taken out with a winding roller and dried at room temperature to obtain the regenerated fiber.

[0041] The regenerated fiber prepared in this embodiment has a lignin content of 1.07 wt%, a tensile strength of 380 MPa, and an elongation at break of 9.45%.

[0042] Example 4:

[0043] (1) Mix 0.50g of corn stalks and 10.00g of N-allyl-N-methylpiperidine chloride ionic liquid in a glass tube reactor. Then add 2.25g of tyrosine as an additive to the glass tube. Use an air heating block to heat the test tube to dissolve and prepare the spinning solution. The heating temperature is 135℃ and the heating time is 16h. The spinning solution is then obtained.

[0044] (2) The spinning solution obtained in step (1) is transferred to the spinneret of the spinning machine. The spinning solution temperature is 60℃ and it is extruded from the spinneret at a speed of 2mL / min to spin fibers. A 15 wt% N-allyl-N-methylpiperidine chloride aqueous solution at 15℃ is used as a coagulation bath. The fibers are left to stand in the coagulation bath. The old water in the washing tank is replaced with new water coagulation bath every 12 hours. After the replacement is repeated 5 times, the fibers in the exchange tank are taken out with a winding roller and dried at room temperature to obtain regenerated fibers.

[0045] The regenerated fiber prepared in this embodiment has a lignin content of 1.35 wt%, a tensile strength of 425 MPa, and an elongation at break of 7.63%.

[0046] Example 5:

[0047] (1) Mix 0.50g of corn stalks and 10.00g of N-allyl-N-methylmorpholine chloride ionic liquid in a glass tube reactor. Then add 2.25g of tyrosine as an additive to the glass tube. Use an air heating block to heat the test tube to dissolve and prepare the spinning solution. The heating temperature is 135℃ and the heating time is 16h.

[0048] (2) The spinning solution obtained in step (1) is transferred to the spinneret of the spinning machine. The spinning solution temperature is 60℃ and it is extruded from the spinneret at a speed of 2mL / min to spin fibers. A 15wt% N-allyl-N-methylmorpholine chloride aqueous solution at 20℃ is used as the coagulation bath. The fibers are left to stand in the coagulation bath. The old coagulation bath in the washing tank is replaced with a new coagulation bath every 12 hours. After the replacement is repeated 5 times, the fibers in the exchange tank are taken out with a winding roller and dried at room temperature to obtain regenerated fibers.

[0049] The regenerated fiber prepared in this embodiment has a lignin content of 1.47 wt%, a tensile strength of 370 MPa, and an elongation at break of 8.07%.

[0050] Example 6:

[0051] (1) Mix 0.50g of corn stalks and 10.00g of N-allylpyridine bromide ionic liquid in a glass tube reactor, and then add 0.75g of tyrosine as an additive to the glass tube. Use an air heating block to heat the test tube to dissolve and prepare the spinning solution. The heating temperature is 135℃ and the heating time is 16h.

[0052] (2) The spinning solution obtained in step (1) is transferred to the spinneret of the spinning machine. The spinning solution is 60°C and is extruded from the spinneret at a speed of 2 mL / min to spin fibers. A 5 wt% N-allylpyridine bromide aqueous solution at 25°C is used as the coagulation bath. The fibers are left to stand in the coagulation bath. The old coagulation bath in the washing tank is replaced with a new coagulation bath every 12 hours. After the replacement is repeated 5 times, the fibers in the exchange tank are taken out with a winding roller and dried at room temperature to obtain regenerated fibers.

[0053] The regenerated fiber prepared in this embodiment has a lignin content of 6.23 wt%, a tensile strength of 300 MPa, and an elongation at break of 8.13%.

[0054] Example 7:

[0055] (1) Mix 0.50g of corn stalks and 10.00g of N-allylpyridine iodide ionic liquid in a glass tube reactor, and then add 2.25g of tyrosine as an additive to the glass tube. Use an air heating block to heat the test tube to dissolve and prepare the spinning solution. The heating temperature is 135℃ and the heating time is 16h.

[0056] (2) The spinning solution obtained in step (1) is transferred to the spinneret of the spinning machine. The spinning solution is 60°C and is extruded from the spinneret at a speed of 2 mL / min to spin fibers. A 10 wt% N-allylpyridine iodide aqueous solution at 15°C is used as a coagulation bath. The fibers are left to stand in the coagulation bath. The old coagulation bath in the washing tank is replaced with a new coagulation bath every 12 hours. After the replacement is repeated 5 times, the fibers in the exchange tank are taken out with a winding roller and dried at room temperature to obtain regenerated fibers.

[0057] The regenerated fiber prepared in this embodiment has a lignin content of 1.20 wt%, a tensile strength of 431 MPa, and an elongation at break of 10.12%.

[0058] Comparative Example 1:

[0059] (1) Weigh 0.50g of corn stalks and process the corn stalks through a planetary ball mill for 1 hour to obtain lignocellulose powder.

[0060] (2) Weigh 5g of lignocellulose powder that has been processed in a ball mill for 1.0h, add 5mL of ethanol-ether (volume ratio 1:1) mixture to remove dissolved substances, soak for 24 hours, filter and dry, and wash the sample repeatedly with hot water until the washing solution is clear.

[0061] (3) The sample obtained in step (2) was heated at 80°C for 2 hours with about 30 mL of 5 wt% NaOH solution to remove lignin and non-cellulose substances. After treatment, hydrochloric acid was added to neutralize it. The pH value after neutralization should be controlled at about 6-8. Then, five times the volume of distilled water was added to the mixed solution, stirred and dispersed evenly, and then allowed to stand for a period of time before filtration to remove all residual chemicals. The solution was dried to constant weight to obtain the purified cellulose-rich material.

[0062] (4) Dissolve 0.30g of the purified cellulose-rich material obtained in step (3) in 10.00g of N-allylpyridine chloride ionic liquid to obtain a cellulose solution. The dissolution temperature is 100℃ and the heating time is 1h to obtain the spinning solution.

[0063] (5) Transfer the spinning solution to the spinneret of the spinning machine. The solution temperature is 60℃ and it is extruded from the spinneret at a constant speed of 2mL / min. The solution is solidified in a 10wt% N-allylpyridine chloride aqueous solution coagulation bath at 5℃ to form fibers. The old coagulation bath in the washing tank is replaced with a new coagulation bath every 12 hours. After repeating the replacement 5 times, the fibers in the exchange tank are taken out with a winding roller and dried at room temperature.

[0064] The regenerated fiber has a lignin content of 5.20 wt%, a tensile strength of 296 MPa, and an elongation at break of 8.42%.

[0065] Comparative Example 2:

[0066] (1) Mix 0.50g of corn stalks and 10.00g of N-allylpyridine iodide ionic liquid in a glass tube reactor, and use an air heating block to heat the test tube to dissolve and prepare the spinning solution. The heating temperature is 135℃ and the heating time is 16h.

[0067] (2) The spinning solution obtained in step (1) is transferred to the spinneret of the spinning machine. The spinning solution is 60°C and is extruded from the spinneret at a speed of 2 mL / min to spin fibers. A 10 wt% N-allylpyridine iodide aqueous solution at 15°C is used as a coagulation bath. The fibers are left to stand in the coagulation bath. The old coagulation bath in the washing tank is replaced with a new coagulation bath every 12 hours. After the replacement is repeated 5 times, the fibers in the exchange tank are taken out with a winding roller and dried at room temperature to obtain regenerated fibers.

[0068] The regenerated fiber prepared in this embodiment has a lignin content of 15.30 wt%, a tensile strength of 231 MPa, and an elongation at break of 3.32%.

[0069] This invention provides a method and approach for improving the performance of regenerated lignocellulose fibers based on lignin degradation. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for improving the properties of regenerated lignocellulose fibers based on lignin degradation, characterized in that, Corn stalks are mixed with ionic liquid and tyrosine and then heated to dissolve, resulting in a spinning solution. The spinning solution is then subjected to wet spinning, and the resulting fibers are solidified in a coagulation bath to obtain regenerated fibers.

2. The method according to claim 1, characterized in that, The ionic liquid is composed of anions and cations.

3. The method according to claim 2, characterized in that, The anion is a halide anion, preferably any one of chloride ion, bromide ion and iodide ion.

4. The method according to claim 2, characterized in that, The cation is any one of imidazole cation, pyridine cation, pyrrolidine cation, piperidine cation and morpholine cation.

5. The method according to claim 1, characterized in that, The mass ratio of corn stalks, ionic liquid, and tyrosine is 0.5:10.00:0.75 to 2.

25.

6. The method according to claim 1, characterized in that, The heating and melting process is carried out at a temperature of 130℃~145℃.

7. The method according to claim 1, characterized in that, The heating and dissolving process takes 10 to 16 hours.

8. The method according to claim 1, characterized in that, The coagulation bath is an aqueous solution of an ionic liquid with a mass concentration of 0% to 20%.

9. The method according to claim 8, characterized in that, The ionic liquid is composed of anions and cations; the anions are halide anions, preferably any one of chloride ions, bromide ions and iodide ions; the cations are any one of imidazole cations, pyridine cations, pyrrolidine cations, piperidine cations and morpholine cations.

10. The method according to claim 1, characterized in that, The temperature of the coagulation bath is 5℃~25℃.

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