A method for preparing nanoregenerated cellulose at high yield at room temperature using industrial waste silk / gum

Abstract

The application discloses a method for preparing nanometer regenerated cellulose at a high yield at room temperature by using industrial waste silk / gum, and comprises the following steps: S1, dissolving cellulose slurry in a solvent and dehydrating under low pressure, then defoaming, filtering, spinning, forming regenerated cellulose in a coagulation bath, stretching the regenerated cellulose, and obtaining regenerated cellulose hydrogel after washing (or continuously drying to obtain regenerated cellulose industrial silk); S2, cutting the hydrogel (or silk) in the step S1, adding into a sulfuric acid solution to stir and hydrolyze, and obtaining a cellulose suspension; S3, adding deionized water into the cellulose suspension obtained in the step S2 to dilute, then centrifugally separating, removing supernatant, continuously adding deionized water to wash multiple times, adding alkali liquor to neutralize after washing, and obtaining a purified cellulose suspension; and S4, drying the purified cellulose suspension in the step S3, and obtaining the nanometer regenerated cellulose.

Description

Technical Field

[0001] This invention belongs to the field of nano-regenerated cellulose preparation technology, specifically relating to a method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste fibers / glue. Background Technology

[0002] The spinning process of cellulose industrial filaments requires continuous spinning followed by winding. During this process, the quality of the cellulose spinning solution is highly unstable before and after equipment adjustments, leading to abnormalities such as large differences in the fineness of the cellulose industrial filament products, resulting in defective waste filaments. Industrial filaments used in tire cords directly affect vehicle safety, and defective waste filaments are difficult to reuse in high-standard industrial applications. Therefore, the high scrap rate keeps the cost of cellulose industrial filaments high. The raw material used in the production of cellulose industrial filaments is high-purity cellulose pulp, which itself is costly. Direct landfill disposal of the waste filaments without recycling not only wastes resources but also increases production costs for enterprises. Since the occurrence of defective products in the spinning process of cellulose industrial filaments is unavoidable, the ability to immediately and parallelly transfer waste filaments to other production lines at the source, turning waste into valuable resources, is of great significance for the survival of enterprises and improving their competitiveness in the international market.

[0003] Among these, the high-yield preparation of high-margin and high-value-added cellulose fine chemicals—nano-regenerated cellulose (NRC)—at room temperature is one of the most direct and feasible industrial pathways. Transforming industrial waste fibers into cellulose fine chemicals not only represents a high-value utilization of resources, reducing corporate losses and even increasing profits, but also serves as a sustainable and clean production approach to reduce the environmental pressure caused by the disposal of waste chemical products.

[0004] As a naturally biodegradable nanomaterial, NRC not only possesses the high specific surface area characteristic of typical nanomaterials, but also boasts numerous advantages compared to inorganic fibers, including low density, low cost, excellent mechanical and physical properties, renewability, and biodegradability. It is widely used in pharmaceuticals, cosmetics, food packaging, paints and coatings, composite materials, and building materials. Meanwhile, competing nanocellulose products on the market are generally priced between 3,500 and 175,000 RMB / kg. In conclusion, nanocellulose products have a wide range of applications and high market value.

[0005] For example, Chinese patent application number 202010973408.2 discloses a method for preparing nanocellulose using agricultural waste sugarcane leaves as raw material. After pretreatment, bleaching, and alkali treatment, nanocellulose is prepared by hydrolysis with sulfuric acid at 45°C. Chinese patent application number 201710617641.5 discloses a method for preparing nanocellulose from plant fibers. Plant fibers are pretreated with sulfuric acid at 30-55°C, followed by centrifugation, washing, neutralization, and collection of the pretreated solids. The solids are then mechanically treated by disc milling and high-pressure homogenization to obtain nanocellulose. Chinese patent application number 200910025794.6 discloses a method for preparing rod-shaped nanocellulose. Fiber raw materials are dispersed in a 50%-65% sulfuric acid aqueous solution, hydrolyzed by single-mode microwave radiation at 20-50°C, and then post-treated by dilution, centrifugation, dialysis, filtration, and ultrasound to obtain nanocellulose.

[0006] There are three main methods for producing nanocellulose: acid hydrolysis, enzymatic hydrolysis, and physical-mechanical methods. Enzymatic hydrolysis is more expensive and costly than acid treatment, with a longer production cycle and more complex processes. Physical-mechanical methods require specialized equipment, primarily involving fine grinding, and consume significant energy. Therefore, the art generally employs inorganic strong acid hydrolysis of natural cellulose to produce nanocellulose. This involves hydrolyzing the amorphous and partially crystalline regions of cellulose with concentrated sulfuric acid or hydrochloric acid to obtain the desired nanocellulose. Sulfuric acid is the most commonly used inorganic acid in acid hydrolysis. Typically, 64% sulfuric acid is used at 45°C for about 30 minutes to hydrolyze nanocellulose, but this method usually yields a low yield (approximately 30%).

[0007] The raw materials selected for this invention are high-orientation (high draw ratio) regenerated cellulose industrial filament waste or hydrogel (hydrogel refers to the product of omitting the final drying process in the preparation of industrial filaments). Compared with traditional wood fibers, due to the multi-layered hierarchical structure of the cell walls of wood fibers, it is difficult to break the hierarchical structure when preparing nanocellulose using acid treatment. Figure 6 ).

[0008] Compared to the regenerated cellulose filament used in this invention, ordinary lyocell staple fiber yarn, although having its multi-layered structure of wood fiber cell walls disrupted after dissolution and regeneration, and both using similar raw materials—high-purity cellulose pulp—differs in their yarn structure. The spinning process of lyocell fiber involves a low draw ratio and low orientation, resulting in lower crystallinity and strength for lyocell staple fiber yarn compared to the industrial regenerated cellulose filament used in this invention. Furthermore, lyocell staple fiber yarn exhibits twisting and entanglement between short fibers (…). Figure 7The tightly bound fibers create a dense structure, hindering acid penetration into the yarn during the production of nano-regenerated cellulose, thus affecting the NRC reaction rate and dimensional stability. In contrast, the regenerated cellulose filaments used in this invention consist of bundles of multiple filaments, belonging to the category of untwisted multifilament yarns. The high-purity cellulose slurry used as raw material, after dissolution and regeneration, not only loses the multi-layered structure found in wood plant cells, but also exhibits a loose structure due to the absence of twisting between the individual filaments, facilitating hydrolysis after acid penetration. Furthermore, the regenerated cellulose filaments used in this invention employ a high draw ratio during spinning, resulting in high orientation and easy fibrillation of the filaments, which is beneficial for the preparation of nano-cellulose.

[0009] When preparing nanocellulose using wood and ordinary lyocell staple fiber, acid has difficulty penetrating the fiber interior. Heating can promote this process, but it will also cause some cellulose macromolecular chains to degrade, resulting in a decrease in yield. Furthermore, heating will further increase energy consumption. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste filaments / glue. This method utilizes waste filaments generated during the spinning process of industrial cellulose filaments to prepare nano-regenerated cellulose with high yield at room temperature. Due to the unique structure of regenerated cellulose hydrogels and the industrial waste filaments used in this invention, nano-cellulose can be prepared at room temperature. This solves the problems of low utilization rate of waste filaments / glue in existing cellulose spinning technologies, complex and low-yield processes for fine chemical preparation, and difficulty in timely turning waste into treasure, thus achieving efficient production technology.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] A method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste fibers / glue includes the following steps:

[0013] S1. After uniformly mixing the waste cellulose gel raw material with the spinning solvent, vacuum dehydration is performed, followed by degassing, filtration, and spinning. Regenerated cellulose is formed in the coagulation bath antisolvent. The regenerated cellulose is stretched, with the total orientation factor between 0.92 and 0.96. After washing with water, regenerated cellulose hydrogel is obtained (the hydrogel is dried by roller drying to obtain industrial filaments).

[0014] S2. Cut the regenerated cellulose hydrogel from step S1, add it to sulfuric acid solution, and stir the reaction at room temperature. After the reaction is complete, a cellulose suspension is obtained.

[0015] S3. Add deionized water to dilute the cellulose suspension obtained in step S2, then centrifuge to remove the supernatant, continue to add deionized water for multiple centrifugation and washing, and after washing, add alkali solution to neutralize to obtain the purified cellulose suspension.

[0016] S4. The purified cellulose suspension from step S3 is dried to obtain the nano-regenerated cellulose.

[0017] The source of waste cellulose gel raw materials can be substandard cellulose slurry (dirty) produced during production, or spinning solution used to "wash" the production line during regular equipment maintenance. Since it is impossible to produce filaments that meet customer requirements, the hydrogel "waste filaments" formed after spinning and washing (to reduce energy consumption and costs, some substandard hydrogels do not need to be dried into industrial filaments) are also considered waste filaments in this scheme.

[0018] Preferably, the spinning solvent in step S1 includes, but is not limited to, imidazole ionic liquids and N-methylmorpholine-N-oxides. The imidazole ionic liquids include, but are not limited to, [AMIM][Cl], [EMIM][Cl], [EMIM][Ac], [BMIM][Ac], [BMIM][Cl], [BMIM]Br, and [BMIM]PF6. The mass ratio of the cellulose gel waste filtrate to the spinning solvent is 5-15:85-95.

[0019] Preferably, the vacuum dehydration temperature in step S1 is 90-120℃, and the time is 2-5h; the spinning process is a pressure of 3-20MPa, a spinneret orifice diameter of 0.02-0.2mm, and a number of orifices of 600-3000; the coagulation bath reaction solvent includes, but is not limited to, water and ethanol; and the stretching ratio is 1-10.

[0020] Preferably, the mass concentration of the sulfuric acid solution in step S2 is 50-75%, the material-to-liquid ratio of the regenerated cellulose hydrogel to the sulfuric acid solution is 1g:8-25mL, and the stirring reaction time is 30-360min.

[0021] Preferably, the alkaline solution in step S3 is one or both of NaOH solution and KOH solution, with a concentration of 0.1-0.5 mol / L.

[0022] Preferably, the drying process in step S4 is either spray drying or freeze drying.

[0023] A method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste fibers / glue includes the following steps:

[0024] S1. After the cellulose slurry is mixed evenly with the spinning solvent, it is vacuum dehydrated to obtain the spinning solution. Then, it is degassed, filtered, and spun. Regenerated cellulose is formed in the coagulation bath antisolvent. The regenerated cellulose is stretched with a total orientation factor between 0.92 and 0.96. After washing with water and drying, regenerated cellulose yarn is obtained.

[0025] S2. Cut the regenerated cellulose industrial waste filaments (unqualified regenerated cellulose filaments) generated in step S1, add deionized water to wash and loosen them, press to remove moisture, then add them to sulfuric acid solution and stir to react at room temperature. After the reaction is completed, a cellulose suspension is obtained.

[0026] S3. Add deionized water to dilute the cellulose suspension obtained in step S2, then centrifuge to remove the supernatant, continue to add deionized water for multiple centrifugation and washing, and after washing, add alkali solution to neutralize to obtain the purified cellulose suspension.

[0027] S4. The purified cellulose suspension from step S3 is dried to obtain the nano-regenerated cellulose.

[0028] Preferably, the spinning solvent in step S1 includes, but is not limited to, imidazole ionic liquids and N-methylmorpholine-N-oxides. The imidazole ionic liquids include, but are not limited to, [AMIM][Cl], [EMIM][Cl], [EMIM][Ac], [BMIM][Ac], [BMIM][Cl], [BMIM]Br, and [BMIM]PF6. The mass ratio of the cellulose slurry to the spinning solvent is 5-15:85-95.

[0029] Preferably, the vacuum dehydration temperature in step S1 is 90-120℃, and the time is 2-5h; the spinning process is a pressure of 3-20MPa, a spinneret orifice diameter of 0.02-0.2mm, and a number of orifices of 600-3000; the coagulation bath reaction solvent includes, but is not limited to, water and ethanol; and the stretching ratio is 1-10.

[0030] Preferably, the drying temperature in step S1 is 50-110°C.

[0031] Preferably, the mass concentration of the sulfuric acid solution in step S2 is 50-75%, the material-to-liquid ratio of the regenerated cellulose industrial waste filaments to the sulfuric acid solution is 1g:8-25mL, and the stirring reaction time is 30-360min.

[0032] Preferably, the alkaline solution in step S3 is one or both of NaOH solution and KOH solution, with a concentration of 0.1-0.5 mol / L.

[0033] Preferably, the drying process in step S4 is either spray drying or freeze drying.

[0034] This invention also protects a nano-regenerated cellulose prepared by the method described above.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) This invention is the first to utilize regenerated cellulose hydrogel to achieve high-yield preparation of NRC directly at room temperature. Compared with the preparation of NRC using regenerated cellulose filaments, it eliminates the energy-intensive drying step, reducing energy consumption. Furthermore, the use of highly oriented regenerated cellulose hydrogel to prepare NRC at room temperature allows for the use of cellulose slurry that cannot meet the requirements for industrial filaments, turning waste into treasure from the source and preventing losses in a timely manner. At the same time, the high draw ratio used in the spinning process of the regenerated cellulose filaments used in this invention leads to high orientation, making it easy for the filaments to fibrillate, which is beneficial for the preparation of NRC. After the spinning solution is extruded through the spinneret, it is drawn and washed to produce monofilaments. The loose characteristics of the monofilaments without twisting enable low-energy preparation at room temperature. When using regenerated cellulose hydrogel to prepare NRC, not only is energy consumption significantly reduced, but the yield of nano-regenerated cellulose is also higher, about 58% higher than that of slurry (Comparative Example 1) and about 233% higher than that of civilian filaments (Comparative Example 2).

[0037] (2) The method for preparing nano-regenerated cellulose using industrial waste filaments / glue at room temperature provided by this invention utilizes waste filaments generated during the spinning process of industrial cellulose filaments to prepare nano-regenerated cellulose at room temperature, reducing the problem of low utilization rate of waste filaments during production, increasing the sustainability of the entire production chain of cellulose industrial filament products, and is of great significance to the survival of enterprises and improving their competitiveness in the international market. At the same time, the prepared nano-regenerated cellulose is a high-margin, high-value-added fine chemical product with extremely high product value. The transformation from waste filaments to fine chemicals is not only a high-value utilization of resources, reducing enterprise losses and even increasing profits, but also a way to achieve sustainable and clean production. Attached Figure Description

[0038] Figure 1 A schematic diagram of industrial regenerated cellulose filament spinning using a spinneret;

[0039] Figure 2 Schematic diagram of an industrial regenerated cellulose spinneret;

[0040] Figure 3 This is a flowchart of the NRC process for preparing cellulose hydrogel in Example 1;

[0041] Figure 4 This is a process flow diagram for preparing NRC from industrial waste fibers in Example 3;

[0042] Figure 5 This is a longitudinal SEM image of the industrial regenerated cellulose filaments in Example 3;

[0043] Figure 6 A model of the cell wall structure of wood fibers;

[0044] Figure 7 A structural model of lyocell staple fiber yarn;

[0045] Figure 8 AFM images of NRC were prepared for Example 3 of this invention;

[0046] Figure 9 AFM image of the nanocellulose prepared in Comparative Example 1 of this invention;

[0047] Figure 10 This is a physical image of the NRC prepared in Example 3 of the present invention. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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.

[0049] Example 1

[0050] A method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste fibers / glue includes the following steps:

[0051] S1. Mix 100g of substandard cellulose slurry with 900g of [BMIM][Cl] evenly, and vacuum dehydrate at 100℃ for 4 hours. After degassing, filter through a 0.05mm filter screen. In the melt pipeline, the mixture is pumped by a metering pump and a booster pump to reach a spinneret pressure of 10MPa. Then, it is spun through a spinneret with a diameter of 0.06mm and 660 holes. After the spinning solution flows out of the spinneret, it passes through an air gap. The temperature of the air gap is controlled at 20℃, the relative humidity at RH60%, and the length at 30mm. The flow rate of the slow cooling air is controlled at 2m³ / h. 3 Regenerated cellulose is produced in deionized water at a temperature of 15℃ and a draw ratio of 2 times. The regenerated cellulose is then stretched at a roller speed of 20m / min. Positive drawing is used during the spinning process to produce regenerated cellulose filaments with high orientation and a total orientation factor of 0.94. The regenerated cellulose is then washed with water to obtain regenerated cellulose hydrogel.

[0052] S2. Cut the 5g regenerated cellulose hydrogel from step S1 to 5mm, add it to 50mL of 65% sulfuric acid solution, and stir at 25℃ and 400rpm for 60min. After the reaction is complete, a cellulose suspension is obtained.

[0053] S3. Add 1L of deionized water to the cellulose suspension obtained in step S2 for dilution, centrifuge at 10000rpm for 18min, remove the supernatant, add 1L of deionized water again, mechanically homogenize at 8000rpm for 2min, centrifuge again, remove the supernatant, repeat the above operation 4 times for washing, after washing, place the suspension in a dialysis bag for dialyzing until the pH is stable, sonicate for 2min, and then add 0.1mol / L NaOH solution dropwise until neutral to obtain the purified cellulose suspension;

[0054] S4. Spray dry the purified cellulose suspension from step S3 to obtain the highly oriented nano-regenerated cellulose (NRC).

[0055] The obtained NRC yield was 60.09%, and the crystallinity was 91.8%; its length was about 76 nm, and its aspect ratio was about 35; its Zeta potential was about -35.1 mV, and its surface had good electronegativity.

[0056] Example 2

[0057] A method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste fibers / glue includes the following steps:

[0058] S1. Mix 100g of substandard cellulose slurry with 900g of [AMIM][Cl] evenly, vacuum dehydrate at 90℃ for 4h, and after degassing, filter through a 0.05mm filter screen. The slurry is then fed through a metering pump and a booster pump in the melt pipeline to reach a spinneret pressure of 15MPa. It is then spun through a spinneret with 0.1mm orifice diameter and 1000 orifices. The spinning solution flows out of the spinneret and passes through an air gap. The air gap temperature is controlled at 25℃, relative humidity at RH50%, and length at 30mm. The slow cooling airflow rate is controlled at 2m³ / h. 3 Regenerated cellulose is produced in deionized water at a temperature of 20℃ and a draw ratio of 2.5. The regenerated cellulose is then stretched at a roller speed of 40m / min. Positive drawing is used during the spinning process to produce regenerated cellulose filaments with high orientation and a total orientation factor of 0.94. The regenerated cellulose is then washed with water to obtain regenerated cellulose hydrogel.

[0059] S2. Cut the 5g regenerated cellulose hydrogel from step S1 to 15mm, add it to 75mL of 55% sulfuric acid solution, and stir at 20℃ and 400rpm for 90min. After the reaction is complete, a cellulose suspension is obtained.

[0060] S3. Add 1L of deionized water to the cellulose suspension obtained in step S2 for dilution, centrifuge at 10000rpm for 18min, remove the supernatant, add 1L of deionized water again, mechanically homogenize at 8000rpm for 2min, centrifuge again, remove the supernatant, repeat this operation 5 times for washing, after washing, place the suspension in a dialysis bag for dialyzing until the pH is stable, sonicate for 2min, and then add 0.2mol / L NaOH solution dropwise until neutral to obtain the purified cellulose suspension;

[0061] S4. Freeze-dry the purified cellulose suspension from step S3 to obtain the highly oriented nano-regenerated cellulose (NRC).

[0062] The obtained NRC yield was 63.17%, and the crystallinity was 90.5%; its length was about 80 nm, and its aspect ratio was about 35; its Zeta potential was about -34.2 mV, and its surface had good electronegativity.

[0063] Example 3

[0064] A method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste fibers / glue includes the following steps:

[0065] S1. Mix 50g of cellulose slurry with 950g of [BMIM][Cl] until homogeneous. Vacuum dehydrate at 90℃ for 4 hours to obtain the spinning solution. After degassing, filter the homogeneous spinning solution through a 0.05mm filter screen. In the melt pipeline, use a metering pump and a booster pump to reach a spinneret pressure of 20MPa. Then, pass the solution through a spinneret with 1500 holes and a 0.06mm orifice for spinning. After exiting the spinneret, the spinning solution passes through an air gap. Control the air gap temperature at 20℃, relative humidity at RH 60%, and length at 30mm. Control the slow cooling airflow rate at 2m³ / h. 3At a temperature of 15℃, regenerated cellulose is produced in deionized water. The regenerated cellulose is then stretched using a draw ratio of 2.5 times, with a roller speed of 40m / min. Positive drawing is used during the spinning process, resulting in highly oriented regenerated cellulose filaments with a total orientation factor of 0.94. After being washed with water, the regenerated cellulose is dried using rollers at 80℃ to obtain regenerated cellulose yarn with a density of 2000dtex. Substandard regenerated cellulose yarns are collected to obtain industrial waste regenerated cellulose filaments.

[0066] S2. Cut the 5g of regenerated cellulose industrial waste fibers generated in step S1 to 10mm, add 1L of deionized water, and then decompose it in a pulp decomposition machine at a speed of 2000rpm for 20000 revolutions. Filter to remove water, add 75mL of 65% sulfuric acid solution, and stir at 23℃ and a stirring speed of 400rpm for 90min. After the reaction is completed, a cellulose suspension is obtained.

[0067] S3. Add 1L of deionized water to the cellulose suspension obtained in step S2 for dilution, centrifuge at 10000rpm for 18min, remove the supernatant, add 1L of deionized water again, mechanically homogenize at 8000rpm for 2min, centrifuge again, remove the supernatant, repeat the above operation 4 times for washing, after washing, place the suspension in a dialysis bag for dialyzing until the pH is stable, sonicate for 2min, and then add 0.3mol / L NaOH solution dropwise until neutral to obtain the purified cellulose suspension;

[0068] S4. Spray dry the purified cellulose suspension from step S3 to obtain the highly oriented nano-regenerated cellulose (NRC).

[0069] The obtained NRC yield was 58.10%, and the crystallinity was 88.6%; its length was about 80 nm, and its aspect ratio was about 40; its Zeta potential was about -33.1 mV, and its surface had good electronegativity.

[0070] Example 4

[0071] A method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste fibers / glue includes the following steps:

[0072] S1. Mix 120g of cellulose slurry with 880g of NMMO aqueous solution (NMMO concentration 80wt%) until homogeneous. Dehydrate under vacuum at 1500Pa for 3 hours at 100℃ to obtain spinning solution. After degassing, the homogeneous spinning solution is filtered through a 0.05mm filter screen. The solution is then passed through a metering pump and a booster pump in the melt pipeline to reach a spinneret pressure of 20MPa. It is then spun through a spinneret with 1500 holes and a 0.06mm orifice. After flowing out of the spinneret, the spinning solution passes through an air gap. The temperature of the air gap is controlled at 20℃, the relative humidity at RH 60%, and the length at 30mm. The flow rate of the slow cooling air is controlled at 2m³ / h. 3 At a temperature of 15℃, regenerated cellulose is produced in deionized water. The regenerated cellulose is then stretched using a draw ratio of 2.5 times, with a roller speed of 40m / min. Positive drawing is used during the spinning process, resulting in highly oriented regenerated cellulose filaments with a total orientation factor of 0.94. After being washed with water, the regenerated cellulose is dried using rollers at 80℃ to obtain regenerated cellulose yarn with a density of 2000dtex. Substandard regenerated cellulose yarns are collected to obtain industrial waste regenerated cellulose filaments.

[0073] S2. Cut the 5g of regenerated cellulose industrial waste fibers generated in step S1 to 10mm, add 1L of deionized water, and then decompose it in a pulp decomposition machine at a speed of 2000rpm for 20000 revolutions. Filter to remove water, add 75mL of 65% sulfuric acid solution, and stir at 23℃ and a stirring speed of 400rpm for 90min. After the reaction is completed, a cellulose suspension is obtained.

[0074] S3. Add 1L of deionized water to the cellulose suspension obtained in step S2 for dilution, centrifuge at 10000rpm for 18min, remove the supernatant, add 1L of deionized water again, mechanically homogenize at 8000rpm for 2min, centrifuge again, remove the supernatant, repeat the above operation 4 times for washing, after washing, place the suspension in a dialysis bag for dialyzing until the pH is stable, sonicate for 2min, and then add 0.3mol / L NaOH solution dropwise until neutral to obtain the purified cellulose suspension;

[0075] S4. Spray dry the purified cellulose suspension from step S3 to obtain the highly oriented nano-regenerated cellulose (NRC).

[0076] The obtained NRC yield was 62.15%, and the crystallinity was 89.6%; its length was about 90 nm, and its aspect ratio was about 25; its Zeta potential was about -32.3 mV, and its surface had good electronegativity.

[0077] Comparative Example 1

[0078] A method for preparing nano-regenerated cellulose includes the following steps:

[0079] Take 5g of a 10mm×10mm sizing sheet (the sizing sheet is undissolved natural cellulose, which is the wood fiber with a multi-layered structure mentioned in the background) and mix it with 50mL of 65% sulfuric acid solution in a round-bottom flask. React at 40℃ with magnetic stirring at 400rpm for 60min. After the reaction is complete, a cellulose suspension is obtained. Add 1L of deionized water to the cellulose suspension for dilution, centrifuge at 10000rpm for 18min, remove the supernatant, add another 1L of deionized water, and mechanically homogenize at 8000rpm for 2min. Centrifuge again and remove the supernatant. Repeat the above operation 4 times for washing. After washing, place the suspension in a dialysis bag for dialyzing until the pH is stable. After sonication for 2min, add 0.3mol / L NaOH solution dropwise until neutral to obtain a purified cellulose suspension. Spray dry the purified cellulose suspension to obtain nanocellulose.

[0080] The yield of the obtained nanocellulose was 38.06%, and the crystallinity was 86.3%. Its length was about 90 nm, and its aspect ratio was about 45. Its Zeta potential was about -34.7 mV, and its surface had good electronegativity.

[0081] Comparative Example 2

[0082] A method for preparing nano-regenerated cellulose includes the following steps:

[0083] Take 5g of hand-torn lyocell regenerated cellulose civilian filaments to 10mm, add 1L of deionized water, and then decompose in a pulp descrambling machine at 2000rpm for 20000 revolutions. Filter to remove water, add 75mL of 65% sulfuric acid solution, and react at 40℃ with magnetic stirring at 400rpm for 90min. After the reaction, a cellulose suspension is obtained. Add 1L of deionized water to the cellulose suspension for dilution, centrifuge at 10000rpm for 18min, remove the supernatant, add another 1L of deionized water, and mechanically homogenize at 8000rpm for 2min, then centrifuge again to remove the supernatant. Repeat the above operation 4 times for washing. After washing, place the suspension in a dialysis bag for dialyzing until the pH is stable. After sonication for 2min, add 0.3mol / L NaOH solution dropwise until neutral to obtain a purified cellulose suspension. Spray dry the purified cellulose suspension to obtain nanocellulose.

[0084] The yield of NRC obtained was 18.2%, and the crystallinity was 83.4%. Its length was about 100 nm, and the aspect ratio was about 25. Its Zeta potential was about -35.4 mV, and the surface had good electronegativity.

[0085] 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 nano-regenerated cellulose with high yield at room temperature using industrial waste filaments / glue, characterized in that, Includes the following steps: S1. After uniformly mixing the cellulose gel waste filament raw material with the spinning solvent, vacuum dehydration is performed, followed by degassing, filtration, and spinning. Regenerated cellulose is formed in the coagulation bath antisolvent. The regenerated cellulose is stretched, with a total orientation factor between 0.92 and 0.

96. After washing with water, regenerated cellulose hydrogel is obtained. S2. Cut the regenerated cellulose hydrogel from step S1, add it to sulfuric acid solution, stir and react. After the reaction is complete, a cellulose suspension is obtained. S3. Add deionized water to dilute the cellulose suspension obtained in step S2, then centrifuge to remove the supernatant, continue to add deionized water for multiple centrifugation and washing, and after washing, add alkali solution to neutralize to obtain the purified cellulose suspension. S4. The purified cellulose suspension from step S3 is dried to obtain the nano-regenerated cellulose. Among them, the source of cellulose gel waste filament raw materials is unqualified dirty cellulose pulp in production or spinning solution used to rinse the production line during regular equipment maintenance. The spinning process in step S1 involves a pressure of 3-20 MPa, a spinneret orifice diameter of 0.02-0.2 mm, and a number of orifices of 600-3000; the coagulation bath reaction solvent is water; the stretching ratio is 1-10; the sulfuric acid solution in step S2 has a mass concentration of 50-75%, and the material-to-liquid ratio of the regenerated cellulose hydrogel to the sulfuric acid solution is 1 g: 8-25 mL; the stirring reaction time is 30-360 min.

2. A method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste filaments / glue, characterized in that, Includes the following steps: S1. After the cellulose slurry is mixed evenly with the spinning solvent, it is vacuum dehydrated to obtain the spinning solution. Then, it is degassed, filtered, and spun. Regenerated cellulose is formed in the coagulation bath antisolvent. The regenerated cellulose is stretched, and the total orientation factor is between 0.92 and 0.

96. After washing with water and drying, regenerated cellulose yarn is obtained. The unqualified regenerated cellulose yarn is collected to obtain industrial waste regenerated cellulose yarn. S2. Cut the regenerated cellulose industrial waste fibers generated in step S1, add deionized water to wash and loosen them, press to remove moisture, then add them to sulfuric acid solution and stir to react. After the reaction is completed, a cellulose suspension is obtained. S3. Add deionized water to dilute the cellulose suspension obtained in step S2, then centrifuge to remove the supernatant, continue to add deionized water for multiple centrifugation and washing, and after washing, add alkali solution to neutralize to obtain the purified cellulose suspension. S4. The purified cellulose suspension from step S3 is dried to obtain the nano-regenerated cellulose. The spinning process in step S1 involves a pressure of 3-20 MPa, a spinneret orifice diameter of 0.02-0.2 mm, and a number of orifices of 600-3000; the coagulation bath reaction solvent is water; the stretching ratio is 1-10; the sulfuric acid solution in step S2 has a mass concentration of 50-75%, and the material-to-liquid ratio of the regenerated cellulose hydrogel to the sulfuric acid solution is 1 g: 8-25 mL; the stirring reaction time is 30-360 min.

3. The method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste filaments / glue as described in claim 1 or 2, characterized in that, The spinning solvent mentioned in step S1 includes, but is not limited to, imidazole ionic liquid and N-methylmorpholine-N-oxide, and the mass ratio of the cellulose gel waste filament raw material to the spinning solvent is 5-15:85-95.

4. The method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste filaments / glue as described in claim 1 or 2, characterized in that, The vacuum dehydration temperature in step S1 is 90-120℃, and the time is 2-5 hours.

5. The method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste filaments / glue according to claim 2, characterized in that, The drying temperature in step S1 is 50-110℃.

6. The method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste filaments / glue according to claim 2, characterized in that, In step S2, the mass concentration of the sulfuric acid solution is 50-75%, the material-to-liquid ratio of the regenerated cellulose industrial waste fibers to the sulfuric acid solution is 1g:8-25mL, and the stirring reaction time is 30-360min.

7. The method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste filaments / glue according to claim 1 or 2, characterized in that, The alkaline solution mentioned in step S3 is one or both of NaOH solution and KOH solution, with a concentration of 0.1-0.5 mol / L.

8. The method for preparing nano-regenerated cellulose with high yield at room temperature using industrial waste filaments / glue according to claim 1 or 2, characterized in that, The drying process described in step S4 is either spray drying or freeze drying.

9. A nano-regenerated cellulose prepared by the method described in claim 1 or 2.

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