A method for the production of regenerated cellulose fibers

Abstract

The application discloses a preparation method of regenerated cellulose fibers, and belongs to the technical field of regenerated cellulose fibers. In view of the problems of easy fibrillation of existing fibers, brittleness caused by cross-linking modification, and insufficient strength and heat resistance, the application adopts an eight-arm hyperbranched polyhedral oligomeric silsesquioxane cross-linking modifier to blend with cellulose pulp, N-methyl morpholine-N-oxide aqueous solution, antioxidant and spinning aid to prepare a spinning dope, and the fibers are prepared through dry-jet wet spinning and post-processing. The modifier is cross-linked with the hydroxyl groups of cellulose through the epoxy groups to form a three-dimensional network, and the rigid POSS core and the flexible polyether arm are combined, so that the fibrillation is inhibited while the flexibility is maintained, the wet strength and heat resistance are significantly improved, and the technical bottleneck that the traditional modification cannot simultaneously consider the strength and toughness is solved.

Description

Technical Field

[0001] This invention relates to the field of regenerated cellulose fiber technology, and more specifically, to a method for preparing regenerated cellulose fibers. Background Technology

[0002] Regenerated cellulose fibers, especially those prepared using N-methylmorpholine-N-oxide aqueous solution as a solvent system, have been widely used in textiles, apparel, nonwovens, and industrial textiles due to their significant advantages such as green and environmentally friendly production process, excellent moisture absorption and breathability, and high dry strength.

[0003] However, existing regenerated cellulose fibers exhibit several technical defects that urgently need to be overcome in practical applications and post-processing. Firstly, due to their extremely high crystallinity and highly oriented microfibrils during spinning and coagulation, and the fact that the cellulose macromolecular chains are primarily bound by weak hydrogen bonds, lacking strong transverse chemical bonds, the fibers are highly susceptible to fibrillation under the combined effects of wet environments and mechanical friction. This fibrillation results in the longitudinal shedding of fine hairs from the fiber surface. Fibrillation not only leads to pilling and severe damage to the appearance of the fabric during use, but also significantly reduces the fiber's wet strength and dimensional stability.

[0004] To address the problem of fibrillation, existing technologies typically employ cross-linking modification, such as introducing bifunctional or multifunctional small-molecule cross-linking agents into the cellulose matrix. However, the cross-linking networks formed between cellulose macromolecular chains by traditional small-molecule cross-linking agents are usually short and very rigid. While this rigid chemical bond binding can inhibit microfibril stripping to some extent, it inevitably destroys the original flexibility of the fiber, leading to a significant increase in fiber brittleness, a sharp drop in elongation at break, and a deterioration in hand feel. This creates a dilemma where the rigidity and toughness of the fiber are difficult to balance.

[0005] Furthermore, with the development of high-performance applications such as special protection and industrial filter materials, the shortcomings of conventional regenerated cellulose fibers in terms of upper limit of bulk mechanical modulus and high-temperature resistance are becoming increasingly prominent. Traditional physical blending or simple small-molecule crosslinking modification techniques are insufficient to significantly improve the overall structural strength and thermal stability of fibers at the molecular level. Therefore, how to develop a new preparation and modification strategy that can fundamentally construct a stable three-dimensional crosslinked network to inhibit fibrillation and improve fiber wet strength, effectively introduce a flexible structure to prevent fiber embrittlement, and simultaneously improve the comprehensive mechanical and heat resistance properties of the fiber, is a core technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the technical problems of existing regenerated cellulose fibers being prone to fibrillation and traditional cross-linking modification leading to fiber brittleness and insufficient overall mechanical strength and heat resistance, the present invention aims to provide a method for preparing regenerated cellulose fibers. This method, by constructing a rigid-flexible three-dimensional nano-cross-linked network in situ between cellulose macromolecules, suppresses fibrillation defects, improves the wet strength and high-temperature resistance of the fiber, and overcomes the problem of modification-induced brittleness. This endows the fiber with excellent flexibility and hand feel, achieving a comprehensive upgrade of the fiber's macroscopic properties.

[0007] To achieve the objectives of this invention and solve the problems existing in the prior art, this invention provides a method for preparing regenerated cellulose fibers, employing the following technical solution:

[0008] A method for preparing regenerated cellulose fiber, wherein the raw materials for preparing the regenerated cellulose fiber include the following components in parts by weight: 10 to 15 parts by weight of cellulose pulp; 85 to 90 parts by weight of an aqueous solution of N-methylmorpholine-N-oxide with a mass concentration of 73% to 87%; 0.1 to 0.5 parts by weight of an antioxidant; 0.8 to 3.5 parts by weight of an octagonal hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier; and 0.2 to 1.2 parts by weight of a spinning aid.

[0009] As a preferred embodiment of the present invention, the cellulose pulp is selected from one or more of softwood pulp, hardwood pulp, cotton linter pulp, bamboo pulp, and hemp pulp.

[0010] As a preferred embodiment of the present invention, the antioxidant is selected from one or more of propyl gallate, octyl gallate, dodecyl gallate, 2,6-di-tert-butyl-4-methylphenol, and tetramethylmethylene-3-3,5-di-tert-butyl-4-hydroxyphenylpropionate methane.

[0011] As a preferred embodiment of the present invention, the spinning aid is selected from one or more of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polysorbate 20, polysorbate 60, and polysorbate 80.

[0012] As a preferred embodiment of the present invention, the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier is an eight-arm terminal epoxy-polyether polyurethane-polyhedral oligomeric silsesquioxane star macromolecule.

[0013] The method for preparing the regenerated cellulose fiber includes detailed steps and cannot be generalized. Specifically, it includes the following steps:

[0014] Step 1, Synthesis of the Eight-Arm Hyperbranched Polyhedral Oligomeric Silsesquioxane Crosslinking Modifier: Eight-p-aminophenyl polyhedral oligomeric silsesquioxanes were dissolved in anhydrous N,N-dimethylformamide, and isophorone diisocyanate was added dropwise to react and obtain isocyanate-terminated polyhedral oligomeric silsesquioxane intermediates; vacuum-dehydrated polytetrahydrofuran ether diol was added to the above reaction system, and dibutyltin dilaurate was added as a catalyst, and the reaction was carried out at a constant temperature to synthesize polyhedral oligomeric silsesquioxane polyurethane prepolymers; glycidyl ether was slowly added dropwise to the system, and the reaction was carried out at a constant temperature until the absorption peak of isocyanate groups was no longer detectable in the system; the solvent was removed from the system to obtain the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier.

[0015] Further, in step one, the specific synthesis method and parameters are as follows: 1 mole of octaaminophenyl polyhedral oligomeric silsesquioxane is dissolved in anhydrous N,N-dimethylformamide, and 8 to 8.5 moles of isophorone diisocyanate are slowly added dropwise, maintaining the system temperature at 40 to 45 degrees Celsius during the addition. After the addition is complete, the temperature is raised to 65 degrees Celsius and reacted at a constant temperature for 3 hours. Subsequently, 8 moles of polytetrahydrofuran ether diol with a molecular weight of 1000 to 2000 are added, along with 0.05% of the total monomer mass of dibutyltin dilaurate, and the reaction is carried out at a constant temperature of 80 degrees Celsius for 4 hours. Then, 8.2 to 8.5 moles of glycidyl ether are added to the system, and the reaction is carried out at a constant temperature of 50 degrees Celsius. The solvent is removed from the system in a vacuum distillation apparatus.

[0016] Step 2, Preparation of spinning solution: The cellulose pulp is pulverized to obtain pulverized cellulose; the N-methylmorpholine-N-oxide aqueous solution is added to a dissolving vessel, and the antioxidant, the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier, and the spinning aid are added sequentially and stirred until uniformly mixed; the pulverized cellulose is added to the mixed solution, and a dehydration reaction is carried out under reduced pressure while stirring until the water content in the system drops to 5% to 13%, forming the spinning solution.

[0017] Furthermore, in step two, the specific parameters for the decompression dehydration reaction are as follows: the decompression dehydration reaction is carried out under conditions of a temperature of 80 to 95 degrees Celsius and a vacuum degree of -0.06 to -0.08 MPa while stirring.

[0018] Step 3, spinning and post-processing: After degassing, the above spinning solution is spun by dry-jet wet spinning through a spinning machine. After being extruded through the spinneret, the solution first passes through an air layer and then enters an aqueous coagulation bath to solidify and form the nascent fiber. The solidified nascent fiber is drawn out, washed with hot water to remove the solvent, and then put into an oven for hot air drying and heat setting treatment. Finally, it is wound up to obtain the regenerated cellulose fiber.

[0019] Furthermore, in step three, the specific parameters for spinning and post-treatment are as follows: dry-jet wet spinning is carried out at 95 to 110 degrees Celsius, the temperature of the aqueous solution coagulation bath is 15 to 25 degrees Celsius and the mass concentration of N-methylmorpholine-N-oxide is 10% to 20%, the temperature of hot water washing is 60 to 80 degrees Celsius, and the temperature of hot air drying and heat setting treatment in the oven is 130 to 150 degrees Celsius.

[0020] Furthermore, the regenerated cellulose fiber described in this invention can be used in continuous and discontinuous fiber-reinforced composite materials.

[0021] The components of this invention exhibit synergistic effects in both microstructure and macroscopic processing. Cellulose pulp, in an N-methylmorpholine-N-oxide aqueous solution system, combined with spinning aids and antioxidants, achieves efficient dissolution without degradation. The core synergistic effect is manifested in the specific structure of the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier, which modifies the fiber: First, the modifier has eight highly active epoxy groups at its ends. During spinning and subsequent hot-air drying and setting, these epoxy groups can undergo ring-opening chemical reactions with the hydroxyl groups on the cellulose molecular chains, thereby constructing a strong three-dimensional chemical crosslinking network between the cellulose macromolecular chains. This lateral chemical bonding force greatly restricts the relative slippage and peeling of microfibers under wet conditions and mechanical friction, inhibiting the fibrillation phenomenon that easily occurs in regenerated cellulose fibers, and improving the wet strength and dimensional stability of the fibers. Second, the polytetrahydrofuran ether diol introduced into the modifier's molecular structure acts as a flexible polyether long arm, playing the role of a molecular spring and internal toughening in the crosslinking network. When the fiber is subjected to external stress stretching or bending... When folded, the flexible long arms can absorb and dissipate a large amount of deformation energy through conformational changes, overcoming the problems of traditional small molecule crosslinking agents that easily lead to shortening, stiffening, and embrittlement of the fiber network structure. This endows cellulose materials with excellent flexibility, elongation at break, and a soft feel. Finally, the polyhedral oligomeric silsesquioxane at the core of the modifier is a rigid inorganic and organic nano-hybrid cage-like framework. It is uniformly anchored and distributed in the cellulose matrix through chemical crosslinking bonds, constructing molecular-level nano-reinforcing origins. This rigid core not only significantly improves the overall mechanical modulus and tensile strength of the fiber, but also effectively blocks heat conduction due to the excellent thermal stability of its inorganic siloxane structure, improving the heat resistance and mechanical retention rate of the final fiber product at high temperatures. The inorganic rigid nano-core, organic flexible long-chain bridge arms, and multi-terminal highly active crosslinking groups perfectly complement each other in the cellulose matrix, solving the technical bottlenecks of traditional regenerated cellulose fibers, such as difficulty in balancing strength and toughness and insufficient heat resistance.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. The eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier used in this invention has highly active epoxy groups at its ends. During the fiber heat setting stage, it can undergo ring-opening crosslinking reactions with free hydroxyl groups on the cellulose macromolecular chains, constructing an extremely robust three-dimensional transverse chemical crosslinking network between the molecular chains. This structure restricts the relative slippage and longitudinal peeling of microfibers under water molecule swelling and external mechanical friction, suppressing the fibrillation defects that easily occur in regenerated cellulose fibers, thereby significantly improving its wet strength and dimensional stability, ensuring excellent appearance retention and anti-pilling properties of the final fabric.

[0024] 2. By introducing polytetrahydrofuran ether diol as a long-chain flexible polyether bridge into the molecular structure of the crosslinking modifier, this flexible long arm acts as an internally toughened molecular spring in the crosslinking network. When the fiber is subjected to external tensile or bending stress, the flexible long arm can absorb and dissipate deformation energy through the conformational transformation of molecular chain segments. This allows the resulting regenerated cellulose fiber to retain excellent elongation at break, resistance to bending fatigue, and a soft, skin-friendly feel while possessing a high crosslinking density.

[0025] 3. The modifier uses polyhedral oligomeric silsesquioxane as a rigid core framework, uniformly anchoring it within the cellulose matrix to construct molecular-level nano-reinforcing points. This enhances the overall mechanical modulus and tensile strength of the fiber, and significantly improves its heat resistance due to the excellent thermal barrier effect of the inorganic siloxane structure. Furthermore, the preparation method of this invention combines the chemical cross-linking and curing process of the modifier with the hot air drying and heat setting processes in the post-spinning treatment of the fiber, avoiding the cumbersome secondary cross-linking padding and high-temperature baking processes, thus greatly shortening the production process and reducing energy consumption. Attached Figure Description

[0026] Figure 1 This is a comparison diagram of fracture strength in the embodiments and comparative examples of the present invention.

[0027] Figure 2 This is a comparison chart of the dry-state elongation at break, wet-state strength retention, and solvent swelling degree in the embodiments and comparative examples of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment provides a method for preparing regenerated cellulose fibers, the raw materials of which include the following components:

[0031] 10 parts by weight of softwood pulp;

[0032] 85 parts by mass of an aqueous solution of N-methylmorpholine-N-oxide with a mass concentration of 73%;

[0033] 0.1 parts by weight of propyl gallate;

[0034] 0.8 parts by weight of an eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier;

[0035] Polyethylene glycol 400 is 0.2 parts by weight.

[0036] Furthermore, the CAS number of the N-methylmorpholine-N-oxide is 7529-22-8;

[0037] Furthermore, the softwood pulp was purchased from:

[0038] The preparation method includes the following steps:

[0039] Step 1: Synthesis of an eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier:

[0040] In a nitrogen-protected reactor, 1 mole of octa-aminophenyl polyhedral oligomeric silsesquioxane (octa-polyhedral oligomeric octa-aminophenyl silsesquioxane, CAS: 518359-82-5) was dissolved in 500 ml of anhydrous N,N-dimethylformamide. Then, 8 moles of isophorone diisocyanate were slowly added dropwise, maintaining the system temperature at 40 degrees Celsius during the addition. After the addition was complete, the temperature was raised to 65 degrees Celsius and the mixture was stirred for 3 hours to obtain isocyanate-terminated polyhedral oligomeric silsesquioxane intermediate (POSS-NCO).

[0041] Add 8 moles of polytetrahydrofuran ether diol with a molecular weight of 1000 that has been vacuum dehydrated to the above reaction system, and add 0.05% of dibutyltin dilaurate as a catalyst. Stir and react at 80 degrees Celsius for 4 hours to synthesize a polyhedral oligomeric silsesquioxane polyurethane prepolymer (POSS-PU) with flexible polyether arms.

[0042] The temperature was lowered to 50°C, and 8.2 mol of glycidyl ether was slowly added dropwise to the system at a rate of 1.5 mL / min. The reaction was maintained at this temperature for 6 hours, with samples taken every hour for Fourier transform infrared spectroscopy (FT-IR) to detect the isocyanate group (-NCO) at 2270 cm⁻¹. -1 The intensity of the characteristic absorption peak at the point is measured until the absorption peak completely disappears, indicating that the reaction is complete, and an eight-armed epoxy-polyether polyurethane-polyhedral oligomeric silsesquioxane star macromolecule is obtained.

[0043] The reaction system was transferred to a rotary evaporator and the solvent N,N-dimethylformamide was removed by vacuum distillation for 2 hours at a vacuum of -0.095 MPa and a temperature of 80 °C. The concentrate was then transferred to a vacuum drying oven and dried for 12 hours at 60 °C and a vacuum of -0.1 MPa to obtain a colorless, transparent, viscous eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier (denoted as POSS-EP) with a yield of 92.3%.

[0044] Step 2, Preparation of spinning solution:

[0045] Ten parts by weight of softwood pulp (α-cellulose content ≥96%, degree of polymerization DP 650) were pulverized using a high-speed pulverizer at 3000 rpm for 5 minutes to obtain pulverized cellulose with a length of 2-5 mm. 85 parts by weight of a 73% N-methylmorpholine-N-oxide aqueous solution were added to a stainless steel dissolving vessel, followed by the sequential addition of 0.1 parts by weight of propyl gallate, 0.8 parts by weight of an octagonal hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier (POSS-EP), and 0.2 parts by weight of polyethylene glycol 400. The mixture was stirred at 100 rpm for 30 minutes at 60°C to ensure thorough and uniform mixing of all components.

[0046] The pulverized cellulose was added to the above mixed solution, the temperature was raised to 80°C, and a vacuum pump was turned on to carry out a dehydration reaction under reduced pressure. The vacuum degree was controlled at -0.06 MPa, the stirring speed was increased to 150 rpm, and the dehydration reaction was carried out for 4 hours. During this period, the moisture content in the system was monitored in real time using a Karl Fischer moisture analyzer until the mass content of moisture dropped to 13%. At this time, the cellulose was completely dissolved, forming a uniform, transparent, and viscosity-stable spinning solution with a viscosity of 4500 mPa·s (measured at 80°C).

[0047] Step 3, Spinning and Post-processing:

[0048] The above spinning solution was transferred to a degassing kettle and statically degassed for 2 hours at a temperature of 85°C and a vacuum of -0.08MPa to remove residual bubbles from the solution. The degassed solution was then transported to the spinning machine via a metering pump and subjected to dry-jet wet spinning at a spinning temperature of 95°C.

[0049] Spinning process parameters: Spinneret specifications: 1000 holes, hole diameter 0.08 mm, hole length 0.24 mm (length-to-diameter ratio 3:1); Spinning speed (metering pump supply): 20 mL / min; Air gap height (air layer distance): 15 mm; Coagulation bath composition: N-methylmorpholine-N-oxide aqueous solution at 15℃, wherein the NMMO mass concentration is 10%; Draw ratio: spinneret draw ratio is 1.2 times;

[0050] After the raw solution is extruded through a spinneret, it first passes through a 15mm air layer (temperature 25℃, relative humidity 65%), and then enters a coagulation bath to solidify and form fibers, with a coagulation time of 0.5 seconds. The solidified nascent fibers are then drawn out and passed through a three-stage hot water washing tank to remove residual solvent. The washing conditions for each stage are as follows: Stage 1: 60℃ hot water, residence time 30 seconds; Stage 2: 70℃ hot water, residence time 30 seconds; Stage 3: 60℃ hot water, residence time 20 seconds.

[0051] After washing, the fibers are placed in a hot air circulating oven for drying and heat setting. The oven is divided into three temperature zones: Zone 1: 130℃, residence time 2 minutes (pre-drying); Zone 2: 145℃, residence time 3 minutes; Zone 3: 130℃, residence time 1 minute (setting and cooling); Finally, the fibers are wound up by a winding machine at a speed of 80m / min to obtain regenerated cellulose fibers.

[0052] Example 2

[0053] This embodiment provides a method for preparing regenerated cellulose fiber. Referring to the preparation method of Example 1, the amount of the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier is adjusted from 0.8 parts by mass to 2.5 parts by mass, while the rest remains the same as in Example 1.

[0054] Example 3

[0055] This embodiment provides a method for preparing regenerated cellulose fiber. Referring to the preparation method of Example 1, the coniferous wood pulp is replaced with cotton linter pulp (α-cellulose content ≥98%, degree of polymerization DP is 750), and the rest is the same as in Example 1.

[0056] Example 4

[0057] This embodiment provides a method for preparing regenerated cellulose fiber. Referring to the preparation method of Example 1, in step one, the molecular weight of polytetrahydrofuran ether diol is adjusted from 1000 to 2000, while the rest remains the same as in Example 1.

[0058] Comparative Example 1

[0059] This comparative example provides a method for preparing regenerated cellulose fibers, referring to the preparation method of Example 1, but without adding the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier, and otherwise remaining the same as in Example 1.

[0060] Comparative Example 2

[0061] This comparative example provides a method for preparing regenerated cellulose fibers, referring to the preparation method of Example 1, except that the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier is replaced with nano-silica, and the rest remains the same as in Example 1.

[0062] Comparative Example 3

[0063] This comparative example provides a method for preparing regenerated cellulose fibers, referring to the preparation method of Example 1, except that the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier is replaced with a conventional small molecule crosslinking agent (butanediol diglycidyl ether), and the rest remains the same as in Example 1.

[0064] Comparative Example 4

[0065] This comparative example provides a method for preparing regenerated cellulose fibers, referring to the preparation method of Example 1, except that polytetrahydrofuran ether diol (PTMEG) is not added during the preparation of the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier, and the rest remains the same as in Example 1.

[0066] Comparative Example 5

[0067] This comparative example provides a method for preparing regenerated cellulose fibers. Referring to the preparation method of Example 1, the polytetrahydrofuran ether glycol (PTMEG) in the process of preparing the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier is replaced with an equimolar amount of polypropylene glycol (PPG, molecular weight 1000), and the rest remains the same as in Example 1.

[0068] Comparative Example 6

[0069] This comparative example provides a method for preparing regenerated cellulose fibers. Referring to the preparation method of Example 1, the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier is replaced with eight-p-aminophenyl polyhedral oligomeric silsesquioxane, and the rest remains the same as in Example 1.

[0070] Comparative Example 7

[0071] This comparative example provides a method for preparing regenerated cellulose fibers. Referring to the preparation method of Example 1, the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier is replaced with polytetrahydrofuran ether diol (PTMEG), and the rest remains the same as in Example 1.

[0072] Performance testing:

[0073] 1. Dry mechanical properties were tested according to GB / T14337-2008. Tensile strength was assessed using a single-fiber electronic tensile tester under standard atmospheric conditions. The clamping distance was 20 mm, the tensile speed was 20 mm / min, and the pre-tension was 0.05 cN / dtex. Fifty fibers were tested in each sample group, and the average value was recorded. The breaking strength (cN / dtex) was recorded, and the data are shown in Table 1.

[0074] 2. Wet mechanical properties: The fiber sample was completely immersed in deionized water at 20±2℃ for 2 hours. After removal, the surface free water was quickly absorbed with absorbent paper (keeping the fiber saturated with water). The wet tensile properties were then tested immediately according to the dry test method described above. The wet breaking strength was recorded, and the wet strength retention rate was calculated using the formula. The data is shown in Table 1.

[0075] 3. Solvent swelling test: Accurately weigh the fiber sample dried to constant weight and record the mass as m1. Place it in an N-methylmorpholine-N-oxide aqueous solution (mass concentration of 20%) at 25℃ for 48 hours to swell. After reaching swelling equilibrium, remove it, quickly absorb the surface solvent with filter paper, and weigh it as m2. Calculate the swelling degree (Q) according to the formula.

[0076] ;

[0077] The lower the swelling degree, the higher the density of the cross-linked network inside the fiber and the more stable the structure. The data are shown in Table 1.

[0078] 4. Dry heat shrinkage test: After the fiber sample is conditioned to moisture equilibrium under standard atmospheric conditions, a pre-tension (0.1 cN / dtex) is applied, and the original length L0 is marked on a scale. The sample is then placed in a hot air circulating oven at 180℃ for 30 minutes (without tension). After removal, it is rehydrated under standard atmospheric conditions for 4 hours (standard atmospheric pressure, 20℃, relative humidity 65%), and the length between the marks L1 is measured again. The dry heat shrinkage rate is calculated using the formula.

[0079] The data is shown in Table 1.

[0080] Table 1

[0081] sample Dry fracture strength (cN / dtex) Elongation at break in dry state (%) Wet fracture strength (cN / dtex) Wet strength retention rate (%) Solvent swelling degree (%) Dry heat shrinkage rate (%) Example 1 5.2 18.5 4.1 78.8 35 2.8 Example 2 5.8 15.2 4.8 82.8 28 1.9 Example 3 5.6 17.8 4.5 80.4 32 2.3 Example 4 5 22.3 3.9 78 38 3.2 Comparative Example 1 4 16 2 50 65 8.5 Comparative Example 2 4.3 15.5 2.4 55.8 58 7.2 Comparative Example 3 4.8 8.5 3.6 75 42 3.8 Comparative Example 4 5 9.2 3.8 76 40 3.5 Comparative Example 5 4.9 12 3.5 71.4 45 4.2 Comparative Example 6 4.1 15.8 2.2 53.7 62 7.8 Comparative Example 7 3.8 20.5 2.1 55.3 68 8

[0082] Table 1 shows that the examples using the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier are significantly superior to the comparative examples in terms of mechanical properties, structural stability, and heat resistance, exhibiting a synergistic improvement trend in wet strength retention, solvent swelling, and dry heat shrinkage. Increasing the amount of modifier further improves fiber strength but slightly reduces elongation at break, while using flexible arms with longer molecular weight polyether chains allows the fiber to achieve better elongation at break while maintaining high strength. In contrast, the fiber without modifier has the worst wet strength retention and heat resistance. Modification with nano-silica or simple polyether glycol has limited effect, while using small-molecule crosslinking agents or modifiers lacking flexible polyether chain arms can improve strength but leads to significant fiber embrittlement and a sharp decrease in elongation at break. This demonstrates that the rigid inorganic cage-like core, flexible long-chain polyether bridge arms, and multi-terminal epoxy crosslinking groups in the eight-arm hyperbranched structure are all indispensable, jointly achieving a balance between the strength and heat resistance of regenerated cellulose fibers.

[0083] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing regenerated cellulose fibers, characterized in that, The raw materials for preparing the regenerated cellulose fiber include the following components in parts by weight: 10 to 15 parts of cellulose pulp, 85 to 90 parts of an aqueous solution of N-methylmorpholine-N-oxide with a mass concentration of 73% to 87%, 0.1 to 0.5 parts of antioxidant, 0.8 to 3.5 parts of an eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier, and 0.2 to 1.2 parts of spinning aid; The preparation method includes the following steps: Step 1, Synthesis of the Eight-Arm Hyperbranched Polyhedral Oligomeric Silsesquioxane Crosslinking Modifier: Eight-p-aminophenyl polyhedral oligomeric silsesquioxanes were dissolved in anhydrous N,N-dimethylformamide, and isophorone diisocyanate was added dropwise to react and obtain isocyanate-terminated polyhedral oligomeric silsesquioxane intermediates; vacuum-dehydrated polytetrahydrofuran ether diol was added to the above reaction system, and dibutyltin dilaurate was added as a catalyst, and the reaction was carried out at a constant temperature to synthesize polyhedral oligomeric silsesquioxane polyurethane prepolymers; glycidyl ether was added dropwise to the system, and the reaction was carried out at a constant temperature until the absorption peak of isocyanate groups was no longer detectable in the system; the solvent was removed from the system to obtain the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier; Step 2, Preparation of spinning solution: The cellulose pulp is pulverized to obtain pulverized cellulose; the N-methylmorpholine-N-oxide aqueous solution is added to a dissolving vessel, and the antioxidant, the eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier, and the spinning aid are added sequentially and stirred until uniformly mixed; the pulverized cellulose is added to the mixed solution, and a dehydration reaction is carried out under reduced pressure while stirring until the mass content of water in the system drops to 5% to 13%, forming the spinning solution; Step 3, spinning and post-processing: After degassing, the above spinning solution is spun by dry-jet wet spinning through a spinning machine. After being extruded through the spinneret, the solution first passes through an air layer and then enters an aqueous coagulation bath to solidify and form the nascent fiber. The solidified nascent fiber is drawn out, washed with hot water to remove the solvent, and then put into an oven for hot air drying and heat setting treatment. Finally, it is wound up to obtain the regenerated cellulose fiber.

2. The method for preparing regenerated cellulose fiber according to claim 1, characterized in that, The cellulose pulp is selected from one or more of the following: softwood pulp, hardwood pulp, cotton linter pulp, bamboo pulp, and hemp pulp.

3. The method for preparing regenerated cellulose fiber according to claim 1, characterized in that, The antioxidant is selected from one or more of propyl gallate, octyl gallate, dodecyl gallate, 2,6-di-tert-butyl-4-methylphenol, and tetramethylmethylene-3,3,5-di-tert-butyl-4-hydroxyphenylpropionate methane.

4. The method for preparing regenerated cellulose fiber according to claim 1, characterized in that, The spinning aid is selected from one or more of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polysorbate 20, polysorbate 60, and polysorbate 80.

5. The method for preparing regenerated cellulose fiber according to claim 1, characterized in that, The eight-arm hyperbranched polyhedral oligomeric silsesquioxane crosslinking modifier is an eight-arm terminal epoxy-polyether polyurethane-polyhedral oligomeric silsesquioxane star macromolecule.

6. The method for preparing regenerated cellulose fiber according to claim 1, characterized in that, In step one, 1 mole of octaaminophenyl polyhedral oligomeric silsesquioxane is dissolved in anhydrous N,N-dimethylformamide, and 8 to 8.5 moles of isophorone diisocyanate are slowly added dropwise. During the dropwise addition, the system temperature is maintained at 40 to 45 degrees Celsius. After the dropwise addition is completed, the temperature is raised to 65 degrees Celsius and reacted at a constant temperature for 3 hours.

7. The method for preparing regenerated cellulose fiber according to claim 1, characterized in that, In step one, 8 moles of polytetrahydrofuran ether diol with a molecular weight of 1000 to 2000 are added, along with 0.05 percent dibutyltin dilaurate by mass of the monomers. The mixture is reacted at a constant temperature of 80 degrees Celsius for 4 hours. Then, 8.2 to 8.5 moles of glycidyl ether are added, and the reaction is carried out at a constant temperature of 50 degrees Celsius. The solvent is removed from the system in a vacuum distillation apparatus.

8. The method for preparing regenerated cellulose fiber according to claim 1, characterized in that, In step two, a decompression dehydration reaction is carried out while stirring under conditions of a temperature of 80 to 95 degrees Celsius and a vacuum degree of -0.06 to -0.08 MPa.

9. The method for preparing regenerated cellulose fiber according to claim 1, characterized in that, In step three, the dry-jet wet spinning is carried out at 95 to 110 degrees Celsius, the temperature of the aqueous solution coagulation bath is 15 to 25 degrees Celsius and the mass concentration of N-methylmorpholine-N-oxide is 10% to 20%, the temperature of hot water washing is 60 to 80 degrees Celsius, and the temperature of hot air drying and heat setting treatment in the oven is 130 to 150 degrees Celsius.

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