Bi-oriented regenerated cellulose fiber and preparation method thereof

Abstract

The invention provides a bi-oriented regenerated cellulose fiber and a preparation method thereof, and belongs to the technical field of high-performance fibers. The preparation method comprises the following steps: S1, mixing alkali, urea and water to obtain a cellulose solvent; s2, mixing a cellulose solvent with cellulose to obtain a cellulose solution; s3, centrifuging the cellulose solution to obtain supernate; and S4, performing micro-fluidic spinning on the supernate to obtain the bi-oriented regenerated cellulose fiber. According to the invention, natural degradable cellulose is taken as a raw material, an alkali / urea system with low price is taken as a solvent, and a micro-fluidic spinning technology is adopted, so that a double-orientation structure with surface radial orientation and internal axial orientation is formed on a single fiber through shearing and scouring of a good solvent in sheath flow in a spinning process. The preparation method provided by the invention also has the advantages of greenness, high efficiency, low cost, mass production and the like.

Description

Technical Field

[0001] This invention relates to the field of high-performance fiber technology, and in particular to a bi-oriented regenerated cellulose fiber and its preparation method. Background Technology

[0002] Cellulose, with its good biocompatibility, biodegradability and wide availability, has become an ideal high-performance fiber raw material that combines economic and ecological benefits.

[0003] Currently, in industrial production or experimental research, the preparation methods for high-performance cellulose fibers typically rely on existing cellulose fiber preparation technologies, such as wet spinning, dry-jet wet spinning, and microfluidic spinning. While these methods can achieve molecular chain orientation and high strength, excessive one-dimensional ordering and close packing lead to excessively strong self-cohesive forces between molecular chains, severely sacrificing the material's ductility and resulting in generally low fracture strain and low toughness. This inherent contradiction between strength and toughness is the core bottleneck restricting the development of high-performance cellulose fibers. The applicant previously focused on strengthening and toughening regenerated cellulose materials through a physical-chemical dual crosslinking strategy; however, the properties of the constructed materials remain limited, indicating that traditional one-dimensional ordering strategies fundamentally restrict toughness.

[0004] Microfluidic spinning technology, due to its ability to precisely manipulate, rapidly distribute, and confinedly assemble multiphase fluids within micro- and nano-channels, offers novel possibilities for simultaneously controlling the multi-level orientation structure of cellulose and synergistically enhancing its strength and toughness. The applicant previously developed a class of cellulose sponge fibers with differentiated structures (sparse outer layer, dense inner layer) using a multi-sheath microfluidic spinning method based on a microfluidic field device (patent application number: 202110341408.5). However, to date, no technology has been reported for controlling complex orientation structures on a single fiber based on microfluidic spinning.

[0005] Therefore, this invention aims to utilize the unique advantages of microfluidic spinning to develop a new method for preparing "dual-oriented" regenerated cellulose fibers with both high strength and high toughness through innovative pre-crosslinking processes and multiphase microfluidic shear curing. Summary of the Invention

[0006] The purpose of this invention is to provide a bi-oriented regenerated cellulose fiber and its preparation method to solve the above-mentioned technical problems.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing bi-oriented regenerated cellulose fibers, comprising the following steps: S1. A cellulose solvent is obtained by mixing alkali, urea and water. S2. Mix cellulose solvent and cellulose to obtain a cellulose solution; S3. Centrifuge the cellulose solution to obtain the supernatant; S4. The supernatant and crosslinking agent are mixed and reacted to obtain the spinning solution; the spinning solution is passed into a microfluidic chip, and bi-oriented regenerated cellulose fibers are obtained by microfluidic spinning.

[0008] Furthermore, the mass ratio of the alkali, urea, and water is 30~50:60~80:350~500.

[0009] Furthermore, the alkali comprises sodium hydroxide and / or lithium hydroxide.

[0010] Furthermore, the cellulose concentration in the cellulose solution is 3-10% by mass; the mixing is carried out by stirring for 1-15 minutes.

[0011] Furthermore, the centrifugation speed is 3000~12000 rpm, and the centrifugation time is 10~60 min.

[0012] Furthermore, the volume ratio of the supernatant to the crosslinking agent is 80~200:1, and the crosslinking agent is epichlorohydrin; The reaction temperature is -10~10℃, and the reaction time is 1~3 h.

[0013] Furthermore, the parameters of the microfluidic spinning are as follows: the flow rate of the spinning solution is 100~1000 μL / min; an alkali / urea solution is introduced into the first sheath flow of the microfluidic chip at a flow rate of 200~2000 μL / min; an acid solution is introduced into the second sheath flow of the microfluidic chip, the type of acid solution being the same as that of the coagulation bath, at a flow rate of 300~2500 μL / min; the coagulation bath contains 5~30% acid solution, wherein the acid is one or more of sulfuric acid, phytic acid, acetic acid, and citric acid.

[0014] Furthermore, the mass ratio of alkali, urea and water in the alkali / urea solution is 3~10:6~20:35~100.

[0015] The present invention also provides bi-oriented regenerated cellulose fibers prepared by the above preparation method.

[0016] The beneficial effects of this invention are: This invention uses natural, biodegradable cellulose as raw material and an inexpensive alkali / urea system as solvent. It employs a dissolution-regeneration method, replacing conventional wet spinning with microfluidic spinning technology to achieve complex fluid flow at a microscale. A dual-orientation structure design, with radial orientation on the surface and axial orientation inside, is achieved on a single fiber to prepare a dual-orientation regenerated cellulose fiber. Furthermore, the thickness of the radial orientation layer on the fiber's outer surface is controlled by designing the microfluidic spinning system structure.

[0017] The preparation method provided by this invention has the advantages of being simple, fast, low-cost, and mass-producible. The prepared bi-oriented regenerated cellulose fiber has a unique structure and high tensile mechanical properties, and can be widely used in aerospace, defense, sports and leisure, industrial manufacturing, construction engineering, and automotive transportation. Attached Figure Description

[0018] Figure 1 SEM image of the bi-oriented regenerated cellulose fiber prepared in Example 1; Figure 2 SEM image of the bi-oriented regenerated cellulose fibers prepared in Example 2; Figure 3 SEM image of the bi-oriented regenerated cellulose fibers prepared in Example 2; Figure 4 SEM image of the bi-oriented regenerated cellulose fibers prepared in Example 4; Figure 5 SEM image of the unidirectional cellulose fibers prepared in Comparative Example 1; Figure 6 SEM image of the unidirectional cellulose fibers prepared in Comparative Example 2; Figure 7 SEM image of the unidirectional cellulose fibers prepared in Comparative Example 3; Figure 8 This is a schematic diagram of a three-phase, five-channel microfluidic chip. Detailed Implementation

[0019] This invention provides a method for preparing bi-oriented regenerated cellulose fibers, comprising the following steps: S1. A cellulose solvent is obtained by mixing alkali, urea and water. S2. Mix cellulose solvent and cellulose to obtain a cellulose solution; S3. Centrifuge the cellulose solution to obtain the supernatant; S4. The supernatant and crosslinking agent are mixed and reacted to obtain the spinning solution; the spinning solution is passed into a microfluidic chip, and bi-oriented regenerated cellulose fibers are obtained by microfluidic spinning.

[0020] In this invention, the mass ratio of alkali, urea and water is 30~50:60~80:350~500, preferably 35~45:65~77:380~460, and more preferably 40:75:400.

[0021] In this invention, the alkali comprises sodium hydroxide and / or lithium hydroxide, preferably sodium hydroxide.

[0022] In this invention, the mass concentration of cellulose in the cellulose solution is 3-10%, preferably 4-5%; the mixing is carried out by stirring for 1-15 min, preferably 2-10 min, and more preferably 3-5 min.

[0023] In this invention, the centrifugation speed is 3000~12000 rpm, preferably 6000~10000 rpm, and more preferably 8000 rpm; the centrifugation time is 10~60 min, preferably 20~50 min, and more preferably 30 min.

[0024] In this invention, the volume ratio of the supernatant to the crosslinking agent is 80~200:1, preferably 90~150:1, and more preferably 100:1; the crosslinking agent is preferably epichlorohydrin. The reaction temperature is -10~10℃, preferably 2~8℃, and more preferably 4~6℃; the reaction time is 1~3h, preferably 1.5~2.5h, and more preferably 2h.

[0025] In this invention, the parameters of the microfluidic spinning are as follows: the flow rate of the spinning solution is 100~1000 μL / min, preferably 100~600 μL / min, and more preferably 100~300 μL / min; an alkali / urea solution is introduced into the first sheath flow of the microfluidic chip at a flow rate of 200~2000 μL / min, preferably 200~1500 μL / min, and more preferably 300~800 μL / min; an acid solution is introduced into the second sheath flow of the microfluidic chip, the type of acid solution being the same as that of the coagulation bath, at a flow rate of 300~2500 μL / min, preferably 500~2000 μL / min, and more preferably 500~1000 μL / min; the coagulation bath contains 5~30% acid solution, preferably 10~25%, and more preferably 15~20%; wherein the acid is one or more of sulfuric acid, phytic acid, acetic acid, and citric acid, preferably sulfuric acid.

[0026] In this invention, the microfluidic chip has a three-phase, five-channel structure, with a channel cross-sectional dimension of 0.3 × 0.3 mm. 2 ~2×2 mm 2 Preferably, it is 0.5~1.5 mm. 2 More preferably, it is 0.8~1.2 mm. 2 The angle between the sheath flow channel and the center flow channel is 3. ~9 Preferably 5 ~8 , further preferably 6 .

[0027] In this invention, the product obtained by microfluidic spinning is washed with water until neutral and then dried to obtain bi-oriented regenerated cellulose fibers. The drying temperature is 20~60℃, more preferably 20~40℃.

[0028] In this invention, the mass ratio of alkali, urea and water in the alkali / urea solution is 3~10:6~20:35~100, preferably 10:20:70.

[0029] The present invention also provides bi-oriented regenerated cellulose fibers prepared by the above preparation method.

[0030] The bi-oriented regenerated cellulose fiber of this invention can be applied in aerospace, defense, sports and leisure, industrial manufacturing, construction engineering and automotive transportation.

[0031] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing bi-oriented regenerated cellulose fibers includes the following steps: S1. Put 40 g of sodium hydroxide and 75 g of urea into a beaker, add 400 g of water, dissolve completely, and then pre-cool to obtain a mixture. S2. Add microcrystalline cellulose to the mixture and stir for 3 min to obtain a cellulose solution with a mass concentration of 3%. S3. Centrifuge the cellulose solution to obtain the supernatant; S4. Add epichlorohydrin at a ratio of 5:100 relative to the supernatant to pre-crosslink the supernatant, and then centrifuge at 5000 rpm to remove air bubbles to obtain the spinning solution. S5. Perform microfluidic spinning on the spinning solution, using a flow channel cross-section of 1×1 mm. 2 The angle between the sheath flow and the central flow channel is 6°. Three-phase five-channel microfluidic spinning chip spinning (such as Figure 8 (As shown in the figure) The spinning solution is introduced into the central channel at a flow rate of 200 μL / min; an alkali / urea solution is introduced into the first sheath at a flow rate of 400 μL / min, with a mass ratio of alkali, urea and water of 10:20:70; a 0.5 wt% H2SO4 solution is introduced into the second sheath at a flow rate of 600 μL / min; a 5 wt% H2SO4 solution coagulation bath is introduced; then the fibers are repeatedly rinsed with deionized water until neutral, and dried at 25°C for 4 h to obtain bi-oriented regenerated cellulose fibers (average diameter of approximately 30 μm).

[0034] Example 2

[0035] A method for preparing bi-oriented regenerated cellulose fibers includes the following steps: S1. Put 35 g of sodium hydroxide and 65 g of urea into a beaker, add 380 g of water, dissolve completely, and then pre-cool to obtain a mixture. S2. Add cotton linters to the mixture and stir for 2 minutes to obtain a cellulose solution with a mass concentration of 4%. S3. Centrifuge the cellulose solution at 6000 rpm for 20 min to obtain the supernatant; S4. Epichlorohydrin was added at a ratio of 150:1 relative to the volume of the supernatant. After pre-crosslinking at 2°C for 1.5 h, the solution was centrifuged at 4000 rpm to remove air bubbles and obtain the spinning solution. S5. Perform microfluidic spinning on the spinning solution, using a flow channel with a cross-sectional size of 0.5 × 0.5 mm. 2 Spinning was performed using a three-phase, five-channel microfluidic spinning chip with a 50° angle between the sheath flow and the central channel. Spinning solution was introduced into the central channel at a flow rate of 150 μL / min. An alkali / urea solution was introduced into the first sheath flow at a mass ratio of 7:13:80 and a flow rate of 300 μL / min. A 1 wt% phytic acid solution was introduced into the second sheath flow at a flow rate of 500 μL / min. A 5 wt% phytic acid solution was introduced as a coagulation bath. The fibers were then repeatedly rinsed with deionized water until neutral and dried at 20°C for 5 h to obtain bi-oriented regenerated cellulose fibers (average diameter approximately 50 μm).

[0036] Example 3

[0037] A method for preparing bi-oriented regenerated cellulose fibers includes the following steps: S1. Put 45 g of sodium hydroxide and 77 g of urea into a beaker, add 460 g of water, dissolve completely, and then pre-cool to obtain a mixture. S2. Add cotton linters to the mixture and stir for 4 minutes to obtain a cellulose solution with a mass concentration of 5%. S3. Centrifuge the cellulose solution at 10,000 rpm for 50 min to obtain the supernatant; S4. Epichlorohydrin was added at a ratio of 90:1 relative to the volume of the supernatant. After pre-crosslinking at 8°C for 2.5 h, the solution was centrifuged at 6000 rpm to remove air bubbles and obtain the spinning solution. S5. Microfluidic spinning was performed on the spinning solution using a three-phase five-channel microfluidic spinning chip with a channel cross-sectional size of 1.5 × 1.5 mm² and an angle of 80° between the sheath flow and the central channel. The spinning solution was introduced into the central channel at a flow rate of 300 μL / min. An alkali / urea solution was introduced into the first sheath flow at a mass ratio of alkali, urea, and water of 10:20:70 at a flow rate of 800 μL / min. A 1 wt% acetic acid solution was introduced into the second sheath flow at a flow rate of 1000 μL / min. Finally, a 5 wt% acetic acid solution was introduced as a coagulation bath. The solution was repeatedly rinsed with deionized water until neutral and dried at 40°C for 3 h to obtain bi-oriented regenerated cellulose fibers (average diameter of approximately 35 μm).

[0038] Example 4

[0039] A method for preparing bi-oriented regenerated cellulose fibers includes the following steps: S1. Put 40 g of sodium hydroxide and 75 g of urea into a beaker, add 400 g of water, dissolve completely, and then pre-cool to obtain a mixture. S2. Add cotton linters to the mixture and stir for 3 minutes to obtain a cellulose solution with a mass concentration of 4.5%. S3. Centrifuge the cellulose solution at 8000 rpm for 30 min to obtain the supernatant; S4. Add epichlorohydrin at a ratio of 100:1 relative to the volume of the supernatant, react at 5°C for 2 h for pre-crosslinking, and then centrifuge at 5000 rpm to remove bubbles to obtain the spinning solution. S5. Microfluidic spinning of the spinning solution was performed using a three-phase five-channel microfluidic spinning chip with a channel cross-sectional size of 1×1 mm² and an angle of 60° between the sheath flow and the central channel. The spinning solution was introduced into the central channel at a flow rate of 150 μL / min. An alkali / urea solution was introduced into the first sheath flow at a mass ratio of 8:15:80 and a flow rate of 500 μL / min. A 0.5 wt% H₂SO₄ solution was introduced into the second sheath flow. Finally, a 5 wt% H₂SO₄ solution was introduced. S The solution was used as a coagulation bath; the fibers were repeatedly rinsed with deionized water until neutral, and dried at 30°C for 4 h to obtain bi-oriented regenerated cellulose fibers (average diameter of about 28 μm).

[0040] Comparative Example 1

[0041] A method for preparing unidirectional regenerated fiber includes the following steps: S1. Put 40 g of lithium hydroxide and 75 g of urea into a beaker, add 400 g of water, dissolve completely, and then pre-cool to obtain a mixture. S2. Add cotton linters to the mixture and stir for 4 minutes to obtain a cellulose solution with a mass concentration of 4%. S3. Centrifuge the cellulose solution to obtain the supernatant; S4. Add epichlorohydrin at a ratio of 100:1 relative to the volume of the supernatant, react at 5°C for 2 h for pre-crosslinking, and then centrifuge at 5000 rpm to remove bubbles to obtain the spinning solution. S5. The supernatant was mixed with 1 mL of epichlorohydrin and reacted at 0℃ for 2 h to obtain a spinning solution. The spinning solution was wet spun using a spinneret with a 0.2 mm orifice. The spinning solution was extruded into a 40 wt% sulfuric acid solution coagulation bath at a feed rate of 800 μL / min to obtain fibers. The fibers were washed with deionized water until neutral and dried at 25℃ for 4 h to obtain unidirectional regenerated cellulose fibers (average diameter of about 60 μm).

[0042] Comparative Example 2

[0043] A method for preparing unidirectional regenerated fiber includes the following steps: S1. Put 40 g of sodium hydroxide and 75 g of urea into a beaker, add 400 g of water, dissolve completely, and then pre-cool to obtain a mixture. S2. Add cotton linters to the mixture and stir for 1 min to obtain a cellulose solution with a mass concentration of 4%. S3. Centrifuge the cellulose solution at 12,000 rpm for 10 min to obtain the supernatant. S4. Add epichlorohydrin at a ratio of 200:1 relative to the volume of the supernatant, react at 10°C for 1 h for pre-crosslinking, and centrifuge at 5000 rpm to remove bubbles to obtain the spinning solution. S5. Wet spinning is performed on the spinning solution using a spinneret with a 0.2 mm orifice. The spinning solution is extruded into a 40 wt% sulfuric acid solution coagulation bath at a feed rate of 1000 μL / min to obtain fibers. The fibers are washed with deionized water until neutral and dried at 50°C for 4 h to obtain unidirectional regenerated cellulose fibers (average diameter of about 80 μm).

[0044] Comparative Example 3

[0045] A method for preparing unidirectional regenerated fiber includes the following steps: S1. Put 40 g of lithium hydroxide and 75 g of urea into a beaker, add 400 g of water, dissolve completely, and then pre-cool to obtain a mixture. S2. Add cotton linters to the mixture and stir for 5 minutes to obtain a cellulose solution with a mass concentration of 4%. S3. Centrifuge the cellulose solution at 3000 rpm for 60 min to obtain the supernatant. S4. Add epichlorohydrin at a ratio of 80:1 relative to the volume of the supernatant, react at -10℃ for 3 h for pre-crosslinking, and centrifuge at 5000 rpm to remove bubbles to obtain the spinning solution. S5. Wet spinning was performed on the spinning solution using a spinneret with an aperture of 0.2 mm. The spinning solution was extruded into a 5 wt% sulfuric acid solution coagulation bath at a feed rate of 1500 μL / min to obtain fibers. The fibers were washed with deionized water until neutral and dried at 25°C for 4 h to obtain unidirectional regenerated cellulose fibers (average diameter of about 75 μm).

[0046] Performance Characterization

[0047] The regenerated cellulose fiber prepared in Example 1 has a tensile breaking strength of 480 MPa, a tensile breaking strain of 35%, and a toughness of 105 MJ / m. -3 . Figure 1 This is a SEM image of the bi-oriented regenerated cellulose fibers prepared in Example 1. Figure 1 It can be seen that the prepared fiber has a dual orientation structure with radial orientation on the surface and axial orientation inside; The regenerated cellulose fiber prepared in Example 2 has a tensile breaking strength of 490 MPa, a tensile breaking strain of 42%, and a toughness of 120 MJ / m. -3 . Figure 2 This is a SEM image of the bi-oriented regenerated cellulose fibers prepared in Example 2. Figure 2 It can be seen that the prepared fiber has a dual orientation structure with radial orientation on the surface and axial orientation inside; The regenerated cellulose fiber prepared in Example 3 has a tensile breaking strength of 460 MPa, a tensile breaking strain of 50%, and a toughness of 96 MJ / m. -3 . Figure 3 This is a SEM image of the bi-oriented regenerated cellulose fibers prepared in Example 3. Figure 3 It can be seen that the prepared fiber has a dual orientation structure with radial orientation on the surface and axial orientation inside; The regenerated cellulose fiber prepared in Example 4 has a tensile breaking strength of 500 MPa, a tensile breaking strain of 30%, and a toughness of 90 MJ / m. -3 . Figure 4 This is a SEM image of the bi-oriented regenerated cellulose fibers prepared in Example 4. Figure 4 It can be seen that the prepared fiber has a dual orientation structure with radial orientation on the surface and axial orientation inside; The regenerated cellulose fiber prepared in Comparative Example 1 had a tensile breaking strength of 500 MPa, a tensile breaking strain of 20%, and a toughness of 60 MJ / m. -3 . Figure 5 This is a SEM image of the unidirectional cellulose fibers prepared in Comparative Example 1. Figure 5 It can be seen that the surface and interior of the prepared fiber are oriented along the fiber axis, which is a unidirectional structure; The regenerated cellulose fiber prepared in Comparative Example 2 had a tensile breaking strength of 560 MPa, a tensile breaking strain of 15%, and a toughness of 70 MJ / m. -3 . Figure 6 This is a SEM image of the unidirectional cellulose fibers prepared in Comparative Example 2. Figure 6 It can be seen that the surface and interior of the prepared fiber are oriented along the fiber axis, which is a unidirectional structure; The regenerated cellulose fiber prepared in Comparative Example 3 had a tensile breaking strength of 580 MPa, a tensile breaking strain of 12%, and a toughness of 65 MJ / m. -3 . Figure 7 This is a SEM image of the unidirectional cellulose fibers prepared in Comparative Example 3. Figure 7 It can be seen that the prepared fiber surface and interior are both oriented along the fiber axis, which is a unidirectional structure.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for the production of bioriented regenerated cellulose fibers, characterized by, The method comprises the following steps: S1, mixing alkali, urea and water to obtain a cellulose solvent; S2, mixing the cellulose solvent and cellulose to obtain a cellulose solution; S3, centrifuging the cellulose solution to obtain a supernatant; S4, mixing the supernatant and a crosslinking agent and then performing a reaction to obtain a spinning dope; and passing the spinning dope into a microfluidic chip to obtain a double-oriented regenerated cellulose fiber through microfluidic spinning.

2. The process for the production of bioriented regenerated cellulose fibers according to claim 1, characterized in that, The mass ratio of the alkali, urea and water is 30-50:60-80:350-500.

3. The method of producing bi-oriented regenerated cellulose fibers according to claim 1, characterized by, The alkali comprises sodium hydroxide and / or lithium hydroxide.

4. The method for producing bi-oriented regenerated cellulose fibers according to claim 1 or 2, characterized by, The mass concentration of the cellulose in the cellulose solution is 3-10%; and the mixing is performed through stirring for 1-15 min.

5. The method of producing bi-oriented regenerated cellulose fibers according to claim 4, characterized in that, The centrifugation is performed at a speed of 3000-12000 rpm for 10-60 min.

6. The method of producing bi-oriented regenerated cellulose fibers according to claim 1 or 2 or 5, characterized in that, The volume ratio of the supernatant to the crosslinking agent is 80-200:1, and the crosslinking agent is epichlorohydrin; The reaction is performed at a temperature of-10-10℃ for 1-3 h.

7. The method of producing bi-oriented regenerated cellulose fibers according to claim 6, characterized in that, The parameters of the microfluidic spinning are as follows: the flow speed of the spinning dope is 100-1000 μL / min; the alkali / urea solution is passed into a first sheath flow of the microfluidic chip at a flow speed of 200-2000 μL / min; an acid solution is passed into a second sheath flow of the microfluidic chip, the acid solution is of the same type as the coagulation bath, and the flow speed is 300-2500 μL / min; and the coagulation bath comprises 5-30% of the acid solution, wherein the acid is one or more of sulfuric acid, phytic acid, acetic acid and citric acid.

8. The method of producing bi-oriented regenerated cellulose fibers according to claim 7, characterized in that, The mass ratio of the alkali, urea and water in the alkali / urea solution is 3-10:6-20:35-100.

9. The double-oriented regenerated cellulose fiber prepared by the preparation method of any one of claims 1-8.

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