Regenerated cellulose fiber and preparation method thereof

Abstract

The preparation method of the regenerated cellulose fiber provided by the embodiment of the invention comprises the following steps: S1, mixing cellulose pulp with compound enzyme and glycine, performing enzyme treatment, and performing ultrasonic treatment to obtain activated pulp; s2, mixing and swelling the activated pulp with an NMMO aqueous solution, lysine and oxidized nanocellulose, and performing vacuum dehydration dissolution, dry-jet wet spinning and gradient coagulating bath forming to obtain nascent fibers; s3, adding the nascent fiber into an aspartic acid / citric acid mixed solution, and performing UV catalytic crosslinking treatment to obtain the regenerated cellulose fiber. The cellulose supramolecular structure is precisely regulated and controlled through compound enzyme-amino acid synergistic pretreatment, the transverse binding force of the fibers is reinforced on the molecular level by combining nanocellulose enhancement and the UV catalytic in-situ crosslinking technology, the fibrillation problem of the regenerated cellulose fibers is fundamentally solved, and the regenerated cellulose fibers have the advantages of being high in mechanical strength, high in mechanical strength and the like. Meanwhile, good mechanical property, dyeing property and hydrophilic comfort are achieved.

Description

Technical Field

[0001] This application relates to the technical field of regenerated cellulose fibers, and specifically, to a regenerated cellulose fiber and a preparation method thereof. Background Art

[0002] Regenerated cellulose fibers are extracted from natural plants rich in cellulose, such as cotton, hemp, bamboo, shrubs, reeds, etc., to obtain pure cellulose. Then, it is impregnated with caustic soda, undergoes chemical reactions with carbon disulfide and alkali solution, and is reduced to cellulose fibers with a certain degree of parallelism and crystallinity through wet spinning. Finally, different specifications of staple fibers or filaments are produced through post-treatment.

[0003] Currently, the commonly used regenerated cellulose fibers in the textile and clothing market mainly include Lyocell fibers, Modal fibers, bamboo pulp fibers, etc. These fibers have excellent biodegradability, hygroscopicity, and air permeability compared with synthetic fibers. At the same time, they also have good dyeability, washability, resistance to deformation, and good elasticity, and are deeply welcomed by the market. However, when regenerated cellulose fibers and their fabrics are mechanically rubbed in the wet state, fibrillation is likely to occur, that is, fine fibers split axially are separated from the fiber surface, resulting in pilling and color fading on the fabric surface, and affecting the smooth hand feeling of the fabric, which limits their wide application in the textile and clothing field. Existing methods, such as crosslinking agents, blending modification, and plasma treatment, often sacrifice the mechanical properties or environmental friendliness of the fibers, and the equipment cost is relatively high. Summary of the Invention

[0004] In the embodiments of this application, a regenerated cellulose fiber and a preparation method thereof are provided. By using a composite enzyme - amino acid synergistic pretreatment to precisely regulate the cellulose supramolecular structure, combined with nano - cellulose reinforcement and UV - catalyzed in - situ crosslinking technology, the transverse binding force of the fiber is strengthened at the molecular level, fundamentally solving the fibrillation problem of regenerated cellulose fibers, and at the same time having good mechanical properties, dyeing properties, and hydrophilic comfort.

[0005] To achieve the above object, in the first aspect, this application provides the following technical solution: A preparation method of a regenerated cellulose fiber, comprising the following steps: S1. Mix cellulose pulp with a composite enzyme and glycine for enzymatic treatment, and then obtain activated pulp through filtration, drying, and ultrasonic treatment.

[0006] S2. Swell the activated pulp with an NMMO aqueous solution, lysine, and oxidized nano - cellulose, and form a primary fiber through vacuum dehydration and dissolution, dry - jet wet - spinning, and gradient coagulation bath molding.

[0007] S3. Add the primary fiber to an aspartic acid / citric acid mixed solution and perform UV - catalyzed crosslinking treatment to obtain the regenerated cellulose fiber.

[0008] Among them, the composite enzyme includes neutral endoglucanase and alkaline xylanase with a mass ratio of 3-5:1; the oxidized nanocellulose is TEMPO-oxidized nanocellulose, with a carboxyl content of 1.1 mmol / g - 1.3 mmol / g and an aspect ratio > 100.

[0009] Currently, it is generally believed that the reason for the easy fibrillation of regenerated cellulose fibers is mainly related to their microstructure. For example, the diameter of Lyocell fibers is about 10 - 30 microns, which are composed of macrofibrils with a diameter of about 0.5 - 1 micron, and the macrofibrils are in turn composed of microfibrils with a diameter of about 100 nanometers. The elementary fibril diameter of the microfibrils is about 5 - 20 nanometers. In addition, Lyocell fibers have a skin-core structure, with a relatively low order degree on the surface and a thickness between dozens and hundreds of nanometers. More importantly, the special forming technology of Lyocell fibers makes the structural units at all levels highly oriented, resulting in strong intermolecular forces within the units, but weak lateral forces between the units, showing the structural characteristics of high crystallinity and high orientation. In the wet state, fiber swelling is not likely to cause axial slippage of the structural units, but after a small amount of lateral hydrogen bonds are broken, if mechanical friction external force is applied, the fibrils are prone to separation, resulting in fibrillation on the fiber surface.

[0010] In this application, cellulose is pretreated with a composite enzyme - amino acid in a specific ratio. The composite enzyme can selectively cut the chain segments in the amorphous region of cellulose, reduce fines, reduce the tendency of fibril peeling, and reduce the degree of polymerization. Glycine can bind to the active center of the composite enzyme through hydrogen bonds, significantly enhancing the efficiency and performance of the composite enzyme system. At the same time, ultrasonic treatment is supplemented to disrupt the microfibril aggregation bundles and reduce the formation of highly oriented structures in subsequent spinning.

[0011] In this application, nanocellulose crystals (CNC) and lysine are introduced into the NMMO (N-methylmorpholine N-oxide) solution. The nano-size effect of CNC enables it to be embedded in the gaps between cellulose microfibrils, enhancing the binding force between microfibrils through a hydrogen bond network. The flexible long chain of lysine can fill the areas not covered by CNC, and a three-dimensional cross-linked network of "cellulose - CNC - lysine" is constructed through condensation to form amide bonds and ionic bonds, inhibiting the peeling of microfibrils in the wet state and improving the mechanical properties and anti-fibrillation properties of the fiber; at the same time, the -COO - on the surface of CNC and the -NH3 + of lysine can form an amphoteric ion layer in the wet state, locking water molecules through electrostatic attraction and reducing the destruction of cellulose hydrogen bonds by water molecules; in addition, the negatively charged surface of CNC preferentially adsorbs dye anions, while the -NH2 of lysine provides cationic sites to achieve dual-site dyeing, and the condensation reaction of lysine can reduce the free hydroxyl groups of cellulose and reduce the dye hydrolysis rate, greatly improving the dyeing performance.

[0012] This application uses an aspartic acid / citric acid system to achieve green crosslinking of cellulose under UV catalysis, avoiding toxic chemical residues of traditional crosslinking agents (such as TAHT, glutaraldehyde, etc.). The carboxyl group of aspartic acid can undergo an esterification reaction with the cellulose hydroxyl group to form a covalent bond. As a ternary carboxylic acid, citric acid can connect multiple cellulose chains and can condense with aspartic acid to form amide-ester composite crosslinking points, synergistically constructing a composite crosslinking network, enhancing the lateral binding force of the fibers, and the crosslinking network has moderate flexibility.

[0013] In any of the above technical solutions, further, in step S1, the addition amount of the composite enzyme is 0.8% - 1.0% of the dry weight of the cellulose pulp; the addition amount of glycine is 0.7% - 0.9% of the dry weight of the cellulose pulp.

[0014] In any of the above technical solutions, further, in step S1, the degree of polymerization of the cellulose pulp is 300 - 600, and it is selected from at least one of wood pulp, cotton pulp, bamboo pulp, and straw pulp.

[0015] In any of the above technical solutions, further, in step S1, the pH of the enzyme treatment is 8 - 9, the temperature is 45°C - 50°C, and the reaction time is 30 min - 45 min.

[0016] In any of the above technical solutions, further, in step S1, the frequency of the ultrasonic treatment is 20 kHz - 25 kHz, the power is 250 W - 350 W, and the time is 20 min - 40 min.

[0017] Preferred ultrasonic treatment parameters can break the microfibril aggregation bundles, reduce the size of cellulose aggregates in the solution, improve the dissolution uniformity of the pulp, and reduce the formation of highly oriented structures in subsequent spinning.

[0018] In any of the above technical solutions, further, in step S1, the waste liquid after filtration can use a 50 kDa membrane ultrafiltration to retain the composite enzyme and the enzyme - glycine complex, and glycine can be recovered by electrodialysis and can be recycled.

[0019] In any of the above technical solutions, further, in step S2, the mass concentration of the NMMO aqueous solution is 85% - 90%.

[0020] In any of the above technical solutions, further, in step S2, the addition amount of lysine is 0.5% - 2% of the mass of the activated pulp, and the addition amount of oxidized nanocellulose is 0.5% - 2% of the mass of the activated pulp.

[0021] In any of the above technical solutions, further, in step S2, the pore diameter of the spinneret plate in the dry-jet wet spinning is 0.08 mm - 0.12 mm, and the length of the air section is 80 mm - 120 mm. The gradient coagulation bath includes: the first coagulation bath: 15% - 25% NMMO aqueous solution, with a temperature of 20°C - 30°C; the second coagulation bath: 3% - 8% Na2CO3 aqueous solution, with a temperature of 35°C - 45°C.

[0022] The preferred gradient coagulation process realizes gradient regulation of the skin structure through the solvent diffusion rate. The parameters of the first coagulation bath can delay the coagulation of the core layer, reduce pores, and create conditions for the initial densification of the skin layer. The parameters of the second coagulation bath can quickly foam the core layer, form a dense skin layer, reduce the porosity of the fiber cross-section, and improve the wet abrasion resistance of cellulose.

[0023] In any of the above technical solutions, further, in step S3, the aspartic acid / citric acid mixed solution contains 0.4 wt% - 0.6 wt% aspartic acid and 2.8 wt% - 3.2 wt% citric acid.

[0024] The preferred dosage of aspartic acid can provide appropriate active cross-linking sites, ensuring sufficient cross-linking density of the fiber while maintaining the flexibility of the molecular chain. If the dosage is too high, the fiber will become brittle due to excessive formation of amide bonds, interfering with the hydrogen bond network between microfibrils; if the dosage is insufficient, the cross-linking point density will decrease, making it difficult to effectively inhibit the peeling of microfibrils. The preferred dosage of citric acid can precisely regulate the pH environment and three-dimensional cross-linking structure of the reaction system. If the concentration is too high, side reactions are likely to occur, resulting in uneven cross-linking; if the concentration is insufficient, the pore distribution in the core layer will be disordered and the phase separation process will get out of control.

[0025] In any of the above technical solutions, further, in step S3, the wavelength of the UV is 363 nm - 367 nm, the intensity is 5 mW / cm 2 -10 mW / cm 2 , and the irradiation time is 3 min - 8 min.

[0026] Adopting one provided in the embodiment of the present application, compared with the prior art, it has the following technical effects: (1) The present application precisely regulates the cellulose supramolecular structure through the synergistic pretreatment of composite enzymes - amino acids, combined with nanocellulose filling and lysine flexible cross-linking, strengthens the transverse binding force of the fiber at the molecular level, effectively inhibits the peeling of microfibrils in the wet state, and fundamentally solves the fibrillation problem.

[0027] (2) The present application improves the tensile strength of the fiber through CNC nano-enhancement and UV-catalyzed in-situ cross-linking technology. The cross-linking network has both rigidity and flexibility. At the same time, CNC and lysine can form a double-site dyeing structure and an amphoteric ion layer, improving the dye adsorption rate and maintaining the moisture absorption and air permeability characteristics of natural fibers.

[0028] (3) The method and process of the present application are simple and easy to realize industrial production. The raw materials are all cheap food-grade raw materials or industrial-grade preparations, with low costs, no toxic or harmful chemical residues, and the cellulose maintains biodegradability throughout the process.

[0029] (4) The regenerated cellulose composite fiber prepared by the method of the present application has the characteristics of good fibrillation resistance, high strength, good moisture absorption and air permeability, etc. It can be used alone or blended with cotton, wool and other synthetic fibers, and is used in fields such as high-grade clothing fabrics and industrial textiles.

[0030] In the second aspect, the present application also provides a regenerated cellulose fiber prepared according to the above preparation method.

[0031] In the third aspect, the present application also provides the application of the above regenerated cellulose fiber in the field of textiles.

[0032] It should be understood that the foregoing general description and the following specific embodiments are both for the purpose of illustration and example and do not necessarily limit the present disclosure. At the same time, the specification is used to explain the principles of the present disclosure. Specific Embodiments

[0033] In order to make the technical solutions and advantages in the embodiments of the present application clearer, the exemplary embodiments of the present application are further described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than an exhaustive list of all embodiments. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0034] The term "and / or" in the present application is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B is specifically understood as: A and B can be included simultaneously, A can exist alone, or B can exist alone, and any of the above three situations can be satisfied.

[0035] Example 1 This example provides a preparation method of a regenerated cellulose fiber, specifically as follows: (1) Take 1 kg of cellulose pulp (wood pulp, water content ≤ 8%, degree of polymerization 550), add a composite enzyme (neutral endoglucanase and alkaline xylanase = 4:1, total addition amount 0.9% of the dry weight of the pulp) and glycine (0.8% of the dry weight of the pulp), beat the above pulp to a water content of 90%, and carry out mechanical stirring reaction at 45 °C and pH = 8.5 for 40 minutes. The degree of polymerization drops to 417. After the reaction is completed, filter through a 200-mesh sieve, dry, and then carry out ultrasonic treatment (300 W, 25 kHz) for 30 minutes to obtain activated pulp; the separated filter waste liquid is ultrafiltered through a 50 kDa membrane to retain the composite enzyme and the enzyme-glycine complex, and glycine is recovered by electrodialysis.

[0036] (2) Mix and swell the above activated pulp with an NMMO aqueous solution (mass concentration 87%), lysine (1.5% of the dry weight of the activated pulp), and oxidized CNC (TEMPO oxidation, carboxyl content 1.2 mmol / g, 1% of the dry weight of the pulp, aspect ratio > 100), where the solid content of the activated pulp is 10%, and dehydrate under vacuum (-0.095 MPa) at 90 °C until completely dissolved to obtain a spinning solution.

[0037] (3) Extrude the above spinning solution through a 0.10 mm spinneret, with an air section length of 100 mm, and pass through a 20% NMMO coagulation bath (25 °C, time 5 s) and a 5% Na2CO3 coagulation bath (40 °C) in sequence to obtain primary fibers.

[0038] (4) Immerse the above primary fibers in a mixed aqueous solution of 0.5% aspartic acid / 3% citric acid, and irradiate with a 365 nm ultraviolet lamp (intensity 8 mW / cm 2 ) for 5 minutes, wash with water and dry to obtain regenerated cellulose fibers.

[0039] Example 2 This example provides a method for preparing regenerated cellulose fibers, specifically: (1) Take 1 kg of cellulose pulp (bamboo pulp, water content ≤ 8%, degree of polymerization 500), add a composite enzyme (neutral endoglucanase and alkaline xylanase = 3.1, total addition amount 0.8% of the dry weight of the pulp) and glycine (0.7% of the dry weight of the pulp), beat the above pulp to a water content of 90%, and carry out mechanical stirring reaction at 45 °C and pH = 8 for 30 minutes. The degree of polymerization drops to 400. After the reaction is completed, filter through a 200-mesh sieve, dry, and then carry out ultrasonic treatment (250 W, 20 kHz) for 20 minutes to obtain activated pulp; the separated filter waste liquid is ultrafiltered through a 50 kDa membrane to retain the composite enzyme and the enzyme-glycine complex, and glycine is recovered by electrodialysis.

[0040] (2) The above-mentioned activated pulp is mixed and swollen with an NMMO aqueous solution (mass concentration of 85%), lysine (0.5% of the dry weight of the activated pulp), and oxidized CNC (TEMPO oxidation, carboxyl content of 1.1 mmol / g, 0.5% of the dry weight of the pulp, aspect ratio > 100). The solid content of the activated pulp is 10%. It is dehydrated under vacuum at 90 °C (-0.095 MPa) until completely dissolved to obtain a spinning solution.

[0041] (3) The above-mentioned spinning solution is extruded through a spinneret plate with a diameter of 0.08 mm, the air section length is 80 mm, and it passes through a 15% NMMO coagulation bath (20 °C, for 5 s) and a 3% Na2CO3 coagulation bath (35 °C) in sequence to obtain nascent fibers.

[0042] (4) The above-mentioned nascent fibers are immersed in a mixed aqueous solution of 0.4% aspartic acid / 2.8% citric acid, and irradiated with a 363 nm ultraviolet lamp (intensity 5 mW / cm 2 ) for 3 minutes, washed with water and dried to obtain regenerated cellulose fibers.

[0043] Example 3 This example provides a method for preparing regenerated cellulose fibers, specifically as follows: (1) Take 1 kg of cellulose pulp (cotton pulp, moisture content ≤ 8%, degree of polymerization of 600), add a composite enzyme (neutral endoglucanase and alkaline xylanase = 5:1, total addition amount is 1.0% of the dry weight of the pulp) and glycine (0.9% of the dry weight of the pulp). The above-mentioned pulp is beaten to a water content of 90%, and mechanically stirred and reacted at 50 °C and pH = 9 for 45 minutes. The degree of polymerization is reduced to 430. After the reaction is completed, it is filtered through a 200-mesh sieve and dried, and then ultrasonically treated (350 W, 25 kHz) for 40 minutes to obtain activated pulp; the separated filtration waste liquid is ultrafiltered and retained with a 50 kDa membrane for the composite enzyme and the enzyme-glycine complex, and glycine is recovered by electrodialysis.

[0044] (2) The above-mentioned activated pulp is mixed and swollen with an NMMO aqueous solution (mass concentration of 90%), lysine (2% of the dry weight of the activated pulp), and oxidized CNC (TEMPO oxidation, carboxyl content of 1.3 mmol / g, 2% of the dry weight of the pulp, aspect ratio > 100). The solid content of the activated pulp is 10%. It is dehydrated under vacuum at 90 °C (-0.095 MPa) until completely dissolved to obtain a spinning solution.

[0045] (3) The above-mentioned spinning solution is extruded through a spinneret plate with a diameter of 0.12 mm, the air section length is 120 mm, and it passes through a 25% NMMO coagulation bath (30 °C, for 5 s) and an 8% Na2CO3 coagulation bath (45 °C) in sequence to obtain nascent fibers.

[0046] (4) Immerse the above-mentioned nascent fibers in a mixed aqueous solution of 0.6% aspartic acid / 3.2% citric acid, and irradiate them with a 367 nm ultraviolet lamp (intensity 10 mW / cm 2 ), irradiate for 8 minutes, wash with water and dry to obtain regenerated cellulose fibers.

[0047] Comparative Example 1 The preparation method provided in this comparative example is the same as that of Example 1 except for the following parameter settings: in step (1), the mass ratio of neutral endoglucanase to alkaline xylanase is 2:1.

[0048] Comparative Example 2 The preparation method provided in this comparative example is the same as that of Example 1 except for the following parameter settings: in step (1), the mass ratio of neutral endoglucanase to alkaline xylanase is 6:1.

[0049] Comparative Example 3 The preparation method provided in this comparative example is the same as that of Example 1 except for the following parameter settings: in step (2), arginine is used to replace lysine in equal amounts.

[0050] Comparative Example 4 The preparation method provided in this comparative example is the same as that of Example 1 except for the following parameter settings: in step (2), unoxidized ordinary CNC is used to replace oxidized CNC in equal amounts.

[0051] Comparative Example 5 The preparation method provided in this comparative example is the same as that of Example 1 except for the following parameter settings: in step (4), the above-mentioned nascent fibers are immersed in glutaraldehyde (1%), crosslinked at 60 °C for 20 minutes, washed with water and dried to obtain regenerated cellulose fibers.

[0052] The properties of the regenerated cellulose fibers obtained in Examples 1-3 and Comparative Examples 1-5 were tested, and the results are shown in Table 1.

[0053] Index detection method: Anti-fibrillation performance: For the wet friction test, FZ / T 52019-2018 "Lyocell Staple Fibers" is used. At a constant rotation speed, the wet friction time corresponds to the number of wet friction times. The longer the wet friction time or the more the number of wet friction times, the stronger the anti-fibrillation ability.

[0054] Mechanical properties: The dry tensile strength / (cN / dtex) and dry elongation at break / (%) were measured for the fiber mechanical properties with reference to GB / T 14337-2022 "Test Method for Tensile Properties of Chemical Fiber Staple Fibers". The wet tensile strength test method is the same as the dry tensile strength, but the test fiber is immersed in water for 24 h before testing.

[0055] Dyeing performance: Using reactive dyes (C.I.Reactive Red 195), dyeing was carried out under the same dyeing conditions (temperature 60°C, pH = 11, time 60 min). The absorbance of the residual solution was measured by an ultraviolet spectrophotometer, and the adsorption rate of the fiber to the dye was calculated.

[0056] Moisture regain: The moisture absorption and air permeability of the fiber were measured with reference to GB / T 9994-2008 (under constant temperature and humidity conditions).

[0057] Table 1 Wet friction / s Dry tensile strength (cN / dtex) Wet tensile strength (cN / dtex) Dry elongation at break / % Dye uptake / % Moisture regain / % Example 1 25.0 5.1 3.8 13.0 96 10.5 Example 2 20.8 4.5 3.3 13.5 93 11.0 Example 3 22.5 4.8 3.5 12.5 95 10.2 Comparative Example 1 9.4 3.9 2.3 15.2 82 13.5 Comparative Example 2 10.7 4.0 2.5 14.8 85 13.0 Comparative Example 3 10.2 4.2 2.6 14.0 88 12.8 Comparative Example 4 9.3 3.6 2.0 16.5 83 14.0 Comparative Example 5 8.9 3.4 1.8 18.0 87 15.5

[0058] As can be seen from Table 1, Examples 1-3 have excellent anti-fibrillation performance and good mechanical properties, while Comparative Examples 1-5 show significantly deteriorated performance due to component adjustment; the dye uptake rate of Examples 1-3 is significantly higher than that of Comparative Examples 1-5, indicating that the oxidation of CNC + amino acid crosslinking in this application provides more dye binding sites; the moisture regain of Examples 1-3 is moderate, indicating that the fiber has both hydrophilicity and strength, while the moisture regain of Comparative Examples 1-5 is too high, showing that their structures are loose, resulting in deteriorated mechanical properties although their moisture absorption is enhanced.

[0059] Based on the embodiments in this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this disclosure.

[0060] Although the preferred embodiments of this application have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0061] Obviously, those skilled in the art can make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalent technologies, this application is also intended to include these modifications and variations.

Claims

1. A method for preparing regenerated cellulose fibers, characterized in that, It includes the following steps: S1. Mix cellulose pulp with a composite enzyme and glycine for enzymatic treatment, and then obtain activated pulp through filtration, drying, and ultrasonic treatment; S2. Swell the activated pulp by mixing it with an NMMO aqueous solution, lysine, and oxidized nanocellulose, and form a nascent fiber through vacuum dehydration dissolution, dry-jet wet spinning, and gradient coagulation bath molding; S3. Add the nascent fiber into an aspartic acid / citric acid mixed solution and perform UV catalytic cross-linking treatment to obtain the regenerated cellulose fiber; Among them, the composite enzyme includes neutral endoglucanase and alkaline xylanase with a mass ratio of 3-5:1; the oxidized nanocellulose is TEMPO-oxidized nanocellulose with a carboxyl content of 1.1 mmol / g - 1.3 mmol / g and an aspect ratio > 100.

2. The preparation method of the regenerated cellulose fiber according to claim 1, wherein, In step S1, the addition amount of the composite enzyme is 0.8% - 1.0% of the dry weight of the cellulose pulp; the addition amount of glycine is 0.7% - 0.9% of the dry weight of the cellulose pulp.

3. The preparation method of the regenerated cellulose fiber according to claim 1, wherein, In step S1, the degree of polymerization of the cellulose pulp is 300 - 600, and it is selected from at least one of wood pulp, cotton pulp, bamboo pulp, and straw pulp.

4. The preparation method of the regenerated cellulose fiber according to claim 1, wherein, In step S1, the pH of the enzymatic treatment is 8 - 9, the temperature is 45°C - 50°C, and the reaction time is 30 min - 45 min; and / or In step S1, the frequency of the ultrasonic treatment is 20 kHz - 25 kHz, the power is 250 W - 350 W, and the time is 20 min - 40 min.

5. The preparation method of the regenerated cellulose fiber according to claim 1, wherein, In step S2, the mass concentration of the NMMO aqueous solution is 85% - 90%; and / or In step S2, the addition amount of lysine is 0.5% - 2% of the mass of the activated pulp, and the addition amount of the oxidized nanocellulose is 0.5% - 2% of the mass of the activated pulp.

6. The preparation method of the regenerated cellulose fiber according to claim 1, characterized in that, In step S2, the pore diameter of the spinneret in the dry-jet wet spinning is 0.08 mm - 0.12 mm, and the length of the air section is 80 mm - 120 mm; and / or the gradient coagulation bath includes: the first coagulation bath: 15% - 25% NMMO aqueous solution, with a temperature of 20°C - 30°C; the second coagulation bath: 3% - 8% Na2CO3 aqueous solution, with a temperature of 35°C - 45°C.

7. The preparation method of the regenerated cellulose fiber according to claim 1, characterized in that, In step S3, the aspartic acid / citric acid mixed solution contains 0.4 wt% - 0.6 wt% of aspartic acid and 2.8 wt% - 3.2 wt% of citric acid.

8. The preparation method of the regenerated cellulose fiber according to claim 1, characterized in that, In step S3, the wavelength of the UV is 363 nm - 367 nm, and the intensity is 5 mW / cm 2 - 10 mW / cm 2 , and the irradiation time is 3 min - 8 min.

9. A regenerated cellulose fiber, characterized in that, It is prepared by the preparation method according to any one of claims 1 - 8.

10. Application of the regenerated cellulose fiber according to claim 9 in the textile field.