A method for preparing microcrystalline regenerated cellulose at room temperature using industrial waste rubber / silk

Abstract

The application discloses a method for preparing microcrystalline regenerated cellulose at room temperature by using industrial waste glue / silk, and comprises the following steps: (1) mixing cellulose slurry with a solvent, then performing dehydration, defoaming, filtration and spinning treatment, and then forming regenerated cellulose in a coagulation bath anti-solvent, and then stretching the regenerated cellulose, washing with water, and obtaining regenerated cellulose hydrogel (or continuously drying to obtain regenerated cellulose industrial silk); (2) adding the regenerated cellulose hydrogel / industrial silk into hydrochloric acid steam volatilized from an aqueous hydrochloric acid solution, and obtaining material A after standing, which is used for standby; (3) washing the material A by adding deionized water, and obtaining regenerated cellulose filter cake, and then adding deionized water into the cellulose filter cake, and obtaining cellulose suspension after ultrasonic treatment; and (4) drying the suspension, and obtaining microcrystalline regenerated cellulose.

Description

Technical Field

[0001] This invention belongs to the field of microcrystalline regenerated cellulose preparation technology, specifically relating to a method for preparing microcrystalline regenerated cellulose at room temperature using industrial waste gum / filament. Background Technology

[0002] Microcrystalline cellulose is currently produced from various cellulose sources. High-purity wood pulp (also known as dissolving pulp) and cotton are the main industrial sources of cellulose fibers. However, these two raw materials are not only expensive and have low yields, but also produce products with poor quality stability (e.g., large variations in monomer morphology) and typically require auxiliary heating, increasing energy consumption. These factors limit the large-scale production of microcrystalline cellulose. From an environmentally friendly and efficient perspective, more and more researchers are turning their attention to the field of waste biomass resources.

[0003] In the spinning process of cellulose industrial filaments, besides the continuous accumulation of industrial waste filaments due to regular equipment maintenance, a more common issue arises during the new product development phase (such as high-modulus, low-shrinkage filaments, and flame-retardant filaments). Repeated heating-cooling-stabilization operations occur, leading to problems like inconsistent fineness, kinking, slubs, and breakage due to the high technical difficulty of solution spinning (air gaps are only 7-30mm). Cellulose industrial filaments produced under these conditions, even after drying and winding, cannot be used in automotive tire cords, which are directly related to vehicle safety. Therefore, after washing (requiring solvent recovery) and before drying, they are usually treated as industrial "waste glue" and disposed of by a third-party environmental agency for a fee. However, the raw material used for cellulose industrial filaments is ultra-high purity dissolving pulp (α-cellulose content >95%), which has a high cost (>10,000 RMB / ton). If waste filaments generated during the spinning process are not recycled and are directly disposed of through landfill or incineration, it will not only pollute the environment but also constitute a serious waste of resources, indirectly reducing product profit margins and market competitiveness (cellulose industrial filament technology has long been monopolized by foreign countries, and China still lacks industrially viable cellulose industrial filaments). Therefore, in the spinning process of cellulose industrial filaments, the ability to immediately and continuously transfer cellulose industrial waste filaments at the source, turning waste into treasure, will be of great significance to the survival of domestic private enterprises and enhancing their international competitiveness. Realizing the transformation of industrial waste filaments into fine cellulose chemicals is not only a high-value utilization of resources, reducing corporate losses and even increasing profits, but also a sustainable and clean production approach that reduces the environmental pressure caused by the disposal of waste chemical products.

[0004] Microcrystalline cellulose possesses characteristics such as renewability, natural biodegradability, high specific surface area, and good mechanical properties, and is frequently used as a rheology modifier / composite material reinforcing agent in cosmetics, food, pharmaceuticals, and composite materials. For example, patent document CN109575144A provides a quaternary ammonium-sulfonated microcrystalline cellulose stabilizer to enhance the sustained-release active ingredient, making herbicides more efficient; patent document CN102327272A uses microcrystalline cellulose as an excipient for tableting, providing a drug for treating hypertension; patent document CN107814848A provides a microcrystalline cellulose ternary composite material with high mechanical properties and high conductivity, which can be used as a filler for blending and modification with existing resins, or as a main material for conductive films and other products; patent document CN104629105A provides a method for preparing microcrystalline cellulose-reinforced rubber wear-resistant materials, improving the long-term reliability of wear-resistant materials. Commercially available microcrystalline cellulose products vary greatly in quality and from batch to batch. The price of domestically produced microcrystalline cellulose is approximately RMB 300,000 per ton, while the price of imported microcrystalline cellulose is as high as RMB 4.5 million per ton.

[0005] A common and widely used method for producing microcrystalline cellulose is based on acid hydrolysis. For example, patent document CN113336863A uses acid hydrolysis, filtration, washing, pulping, and drying to prepare microcrystalline cellulose from plant fibers; patent document CN108410923B uses sorghum straw as raw material and prepares microcrystalline cellulose through alkali pretreatment, bleaching, acid hydrolysis, enzymatic hydrolysis, washing, and drying; patent document CN115874481A uses grape pomace as raw material, which is dried, pulverized, sieved, mixed with water, and then subjected to secondary enzymatic hydrolysis and centrifugation to obtain crude microcrystalline cellulose, which is then spray-dried to obtain microcrystalline cellulose; and patent document CN107629130B uses cotton stalk husks as raw material and prepares microcrystalline cellulose through washing, sun-drying, vacuum drying, degumming, bleaching, pulverizing, acid hydrolysis, ultrasonic treatment, centrifugation, dialysis, and freeze-drying. Existing microcrystalline cellulose production processes have several shortcomings. For example, patent document CN107629130A uses pretreated cotton stalks, followed by sulfuric acid hydrolysis and ultrasonic assistance to produce cotton stalk microcrystalline cellulose; organic acids (such as formic acid), as in patent document CN103122592B, involve mixing waste cotton with formic acid and then further processing to obtain microcrystalline cellulose; or acidic organic solvents (such as the DES system) are used in combination with auxiliary heating and mechanical decomposition processes for intermittent preparation. These methods (using acid treatment) have relatively high production costs (low yield), are prone to equipment corrosion, and variations in heating levels and raw materials can easily lead to poor dimensional stability and large batch-to-batch differences in the final product. Secondly, traditional methods suffer from problems due to the limited availability of raw materials and poor process stability. Currently, most mainstream manufacturers use expensive wood pulp or even cotton pulp to prepare microcrystalline cellulose: for example, mixing dissolving pulp with sulfuric acid solution, reacting under heating conditions to obtain an acid-hydrolyzed suspension, then filtering and washing to neutrality, followed by spray drying or freeze drying (laboratory level) to obtain microcrystalline cellulose. While some researchers have used biomass waste such as crop straw as raw materials to prepare microcrystalline cellulose, these methods require prior alkali pretreatment and bleaching before subsequent microcrystalline cellulose production. This process is not only cumbersome and involves the extensive use of chemicals, increasing environmental and economic costs, but also results in significant variations in the quality of the final product due to the instability of the raw materials. Therefore, the traditional batch acid hydrolysis process relying on cellulose pulp limits the large-scale and continuous production of high-size stable microcrystalline cellulose.

[0006] Therefore, this invention is proposed. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing microcrystalline regenerated cellulose (MRC) at room temperature using industrial waste glue / filaments. This method utilizes waste industrial regenerated cellulose glue / filaments to directly prepare high-quality (size-stable and uniform) and high-yield (80%) microcrystalline regenerated cellulose at room temperature, with low energy consumption and a simple preparation process.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing microcrystalline regenerated cellulose at room temperature using industrial waste glue / filament (process route one), comprising the following steps:

[0010] (1) After mixing the cellulose slurry with the solvent, dehydrate it, then degas, filter, and spin it. Then, regenerated cellulose is formed in the antisolvent of the coagulation bath. The resulting regenerated cellulose is stretched and washed with water to obtain regenerated cellulose hydrogel.

[0011] (2) Add the regenerated cellulose hydrogel obtained in step (1) to the hydrochloric acid vapor obtained by evaporating the hydrochloric acid aqueous solution, and let it stand to obtain material A for later use;

[0012] (3) Add deionized water to material A obtained in step (2) to wash and obtain regenerated cellulose filter cake. Then add deionized water to the obtained cellulose filter cake and sonicate to obtain cellulose suspension.

[0013] (4) The cellulose suspension obtained in step (3) is dried to obtain microcrystalline regenerated cellulose.

[0014] In the above technical solutions, cellulose slurry is used as raw material to prepare regenerated cellulose hydrogel (waste glue), and then microcrystalline regenerated cellulose is prepared.

[0015] Secondly, the present invention also provides a method for preparing microcrystalline regenerated cellulose using industrial waste glue / filament at room temperature (process route two), comprising the following steps:

[0016] (1) After mixing cellulose slurry with solvent, dehydration is carried out, followed by degassing, filtration, and spinning. Then, regenerated cellulose is formed in the antisolvent of the coagulation bath. The obtained regenerated cellulose is stretched, washed with water, and dried to obtain regenerated cellulose industrial yarn.

[0017] (2) After soaking the regenerated cellulose industrial filaments obtained in step (1) in water, add them to the hydrochloric acid vapor obtained by evaporating the hydrochloric acid aqueous solution. After standing, material B is obtained and set aside.

[0018] (3) Add deionized water to the material B obtained in step (2) to wash and obtain a regenerated cellulose filter cake. Then add deionized water to the obtained cellulose filter cake and sonicate to obtain a cellulose suspension.

[0019] (4) The cellulose suspension obtained in step (3) is dried to obtain microcrystalline regenerated cellulose.

[0020] In the above technical solution, after preparing regenerated cellulose hydrogel using cellulose slurry as raw material, it is dried to obtain regenerated cellulose industrial filaments (waste filaments), and then microcrystalline regenerated cellulose is prepared.

[0021] As a further preferred embodiment of the above technical solution, in process route one or process route two, the solvent mentioned in step (1) includes, but is not limited to, imidazole ionic liquid and N-methylmorpholine-N-oxide; the imidazole ionic liquid includes, but is 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 solvent is 5-15:85-95.

[0022] As a further preferred embodiment of the above technical solution, in process route one or process route two, in step (1), the dehydration temperature is 60-120℃, the time is 2-5h, and the pressure is 2-30mbar; the spinning process has a pressure of 3-20MPa, a spinneret orifice diameter of 0.02-0.2mm, and a number of orifices of 660-3000; the coagulation bath reaction solvent includes, but is not limited to, water and ethanol; the stretching ratio is 1-10, the roller speed during the stretching process is 10-100m / min, and positive stretching is used during the spinning process, so that the produced regenerated cellulose industrial filament has high orientation, with a total orientation factor between 0.92 and 0.96. Of course, during the spinning process, the spinning solution can also pass through the air gap after flowing out of the spinneret. During this process, the temperature of the air gap is controlled at 15℃-30℃, the relative humidity is RH30%-80%, the length is 7mm-30mm, and the flow rate of the slow cooling air is controlled at 1m. 3 / h~5m 3 / h, temperature is 10℃~25℃; the filtration mentioned above can be performed through a 0.05mm filter screen.

[0023] As a further preferred embodiment of the above technical solution, in process route two, the drying temperature in step (1) is 50–110°C. Drying can be carried out using three pairs of drying rollers, with a roller speed of 10–100 m / min.

[0024] As a further preferred embodiment of the above technical solution, in process route one, in step (2), the concentration of the hydrochloric acid aqueous solution is 6-12 mol / L, the ratio of the regenerated cellulose hydrogel to the hydrochloric acid aqueous solution is 1g:50-200mL, the standing time is 6-48h, and the standing temperature is room temperature (20-30℃).

[0025] As a further preferred embodiment of the above technical solution, in process route two, in step (2), the concentration of the hydrochloric acid aqueous solution is 6-12 mol / L, the ratio of the regenerated cellulose industrial filament to the hydrochloric acid aqueous solution is 1g:50-200mL, the standing time is 6-48h, and the standing temperature is room temperature (20-30℃).

[0026] As a further preferred embodiment of the above technical solution, in process route one or process route two, in step (3), the ultrasonic power is 1000-2000W and the ultrasonic treatment time is 5-30min.

[0027] As a further preferred embodiment of the above technical solution, in process route one or process route two, in step (4), the drying is one of spray drying and freeze drying; preferably, it is freeze drying.

[0028] It is important to emphasize that the cellulose pulp mentioned above, i.e. cellulose waste glue / filament raw material, can be derived from substandard cellulose pulp (dirty) produced during production, or from spinning solutions used to "wash" the production line during regular equipment maintenance. Because it cannot produce filaments that meet customer requirements, the hydrogel formed after spinning and washing (to reduce energy consumption and costs, some substandard hydrogels do not need to be dried into industrial filaments) is also referred to as waste glue in this invention.

[0029] Thirdly, the present invention also claims protection for microcrystalline regenerated cellulose prepared by process route one or process route two.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) This invention provides a method for preparing microcrystalline regenerated cellulose (MRC) at room temperature using industrial waste glue / filament. For the first time, it utilizes industrial waste glue / filament and hydrochloric acid vapor to prepare MRC. Compared with the natural plant cellulose commonly used in the production of microcrystalline cellulose, this method uses industrial waste glue / filament, which cannot be used to produce automobile tire cord, to prepare MRC, thus turning waste into treasure from the source. The raw materials used in this invention can be industrial waste filaments accumulated during the spinning process of cellulose industrial filaments due to regular equipment maintenance. These filaments are usually collected as industrial waste glue after washing and before drying. Alternatively, they can be industrial waste filaments produced during the new product development period due to repeated temperature rises and falls and stable operations, as well as the high technical difficulty of solution spinning, resulting in problems such as inconsistent fineness, kinking, slubs, and breakage. These industrial waste filaments are produced after drying and winding under these conditions. These types of industrial waste rubber / filaments cannot be used to produce tire cords for automobiles, which are related to vehicle safety. Furthermore, the ultra-high purity dissolving pulp used in the production of cellulose industrial filaments is itself costly. If the waste rubber / filaments generated during the spinning process are directly disposed of through landfills or incineration without recycling, it will not only pollute the environment but also constitute a serious waste of resources, indirectly reducing product profit margins and market competitiveness. Therefore, this invention, based on the raw materials used, offers both economic and environmental benefits.

[0032] (2) The present invention provides a method for preparing microcrystalline regenerated cellulose (MRC) at room temperature using industrial waste glue / filament. Since the industrial regenerated cellulose filaments are drawn and washed after being extruded from the spinneret and are not twisted, the filaments are loosely arranged, which is beneficial for the continuous preparation of MRC at room temperature with low energy consumption (see Figure 5 The raw material used in this invention can be industrial waste rubber that has not been dried after being drawn and washed. After spinning, the surface still retains moisture, and the water film on the surface of the waste rubber facilitates the adsorption of hydrochloric acid vapor, thereby promoting cellulose hydrolysis. Similarly, after soaking, the surface of industrial waste filaments is also covered with a water film, which is beneficial for hydrochloric acid vapor-catalyzed hydrolysis. Furthermore, after dissolution and regeneration, the multi-layered structure of natural cellulose disappears, accelerating the acid hydrolysis process (see...). Figure 4 ).

[0033] (3) This invention provides a method for preparing microcrystalline regenerated cellulose (MRC) from industrial waste glue / filament at room temperature. During the preparation of MRC using hydrochloric acid vapor hydrolysis, the hydrochloric acid aqueous solution can be reused multiple times, reducing chemical consumption. Furthermore, the material is easy to wash, shortening the washing process while saving washing water, resulting in less environmental pollution and cost savings. Compared to using acid solutions, hydrochloric acid vapor catalytic hydrolysis provides a milder hydrolysis environment, leading to a higher yield of up to 80%. The MRC prepared by the method provided in this invention has similar thermal stability to commercially available microcrystalline cellulose (Adamas-beta, LOT. P2354882), both around 330℃. Morphologically, it is more regular and uniform in size than commercially available products, with a similar length but a much smaller width. Its crystallinity is slightly lower than commercially available microcrystalline cellulose, but still around 90%. This invention not only provides a way to reuse industrial waste glue / filament for regenerated cellulose but also provides a simple method for preparing widely applicable MRC.

[0034] In summary, this invention not only broadens the ways to reuse industrial waste glue / filaments of regenerated cellulose, but also has both economic and environmental benefits. The microcrystalline regenerated cellulose prepared by this invention also has excellent performance, high industrial application value, and good market promotion and application prospects. Attached Figure Description

[0035] Figure 1 This is a product image of the microcrystalline regenerated cellulose prepared in Example 1 of the present invention;

[0036] Figure 2 The images provided are a comparison of microscope and fiber analyzer images of the MRC prepared in Example 1 of this invention and commercially available microcrystalline cellulose (Adamas-beta, LOT. P2354882); wherein: A is a microscope image of the MRC prepared in Example 1; B is a microscope image of commercially available microcrystalline cellulose; C is a fiber analyzer image of the MRC prepared in Example 1; and D is a fiber analyzer image of commercially available microcrystalline cellulose.

[0037] Figure 3 The image shows a comparison of SEM images of the MRC prepared in Example 1 of this invention and the commercially available microcrystalline cellulose (Adamas-beta, LOT. P2354882); wherein: A is the SEM image of the MRC prepared in Example 1; B is the SEM image of the commercially available microcrystalline cellulose.

[0038] Figure 4 SEM image of cross-section of waste cellulose gum monofilament from regenerated cellulose industry;

[0039] Figure 5 This is a SEM image of a cross-section of regenerated cellulose industrial waste rubber multifilament. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] A method for preparing microcrystalline regenerated cellulose using industrial waste gum at room temperature includes the following steps:

[0043] 100g of cellulose slurry was mixed with 900g of [BMIM][Cl] and then vacuum dehydrated at 100℃ for 3 hours. After degassing, the mixture was filtered through a 0.05mm filter to form a uniform spinning solution. This solution was then fed through a metering pump and a booster pump in a melt pipeline to a spinneret pressure of 10MPa. The solution was then spun through a spinneret with 660 holes and a 0.06mm orifice. After exiting the spinneret, the spinning solution passed through an air gap. The air gap temperature was controlled at 20℃, relative humidity at 60% RH, and length at 30mm. The slow cooling airflow rate was controlled at 2m³ / h. 3 / h, temperature 15℃. Regenerated cellulose is produced in deionized water. After initial orientation, the regenerated cellulose is stretched using a draw ratio of 2 times, with a roller speed of 20m / min. Positive drawing is used during the spinning process, resulting in highly oriented industrial filaments of regenerated cellulose with a total orientation factor of 0.95. The stretched regenerated cellulose is then washed with water and collected directly as industrial waste glue.

[0044] 200 mL of 12 mol / L hydrochloric acid aqueous solution was filled into a desiccator and allowed to stand for 24 hours to allow the hydrochloric acid to evaporate and reach equilibrium. 3.5 g of industrial waste adhesive was taken; its moisture content was tested to be 200%, and its dry weight was calculated to be 1.17 g. The regenerated cellulose waste adhesive was wrapped around a rack and quickly placed into the desiccator. After 18 hours, it was removed, washed with deionized water until neutral, and then sonicated at 1600 W for 15 minutes. The sonicated cellulose suspension was collected and freeze-dried for 24 hours to obtain MRC.

[0045] The obtained MRC yield was 72.8%, with a degree of polymerization of 50, and a length of 150±24 μm and a width of 14±2 μm. Its morphology was more regular compared to commercially available microcrystalline cellulose.

[0046] Example 2

[0047] A method for preparing microcrystalline regenerated cellulose using industrial waste gum at room temperature includes the following steps:

[0048] 10g of cellulose slurry was mixed with 90g of [AMIM][Cl] and then vacuum dehydrated at 90℃ for 4 hours. After degassing, the mixture was filtered through a 0.05mm filter to form a uniform spinning solution. This solution was then fed through a metering pump and a booster pump in a melt pipeline to a spinneret pressure of 10MPa. The solution was then spun through a spinneret with 660 holes and a 0.06mm diameter. After exiting the spinneret, the spinning solution passed through an air gap. The air gap temperature was controlled at 20℃, relative humidity at 60% RH, and length at 30mm. The slow cooling airflow rate was controlled at 2m³ / h. 3 / h, temperature 15℃. Regenerated cellulose is produced in deionized water. After initial orientation, the regenerated cellulose is stretched using a draw ratio of 2.5 times, with a roller speed of 40m / min. Positive drawing is used during the spinning process, which results in highly oriented regenerated cellulose industrial filaments. The stretched regenerated cellulose is then washed with water and collected directly as industrial waste glue.

[0049] 200 mL of 12 mol / L hydrochloric acid aqueous solution was filled into a desiccator and allowed to stand for 24 hours to allow the hydrochloric acid to evaporate and reach equilibrium. 4 g of regenerated cellulose industrial waste gum was taken; its moisture content was tested to be 200%, and its dry weight was calculated to be 1.33 g. The regenerated cellulose waste gum was wrapped around a rack and quickly placed into the desiccator. After 12 hours, it was removed, washed with deionized water until neutral, and then sonicated at 1600 W for 10 minutes. The sonicated cellulose suspension was collected and freeze-dried for 24 hours to obtain MRC.

[0050] The obtained MRC yield was 83.6%, the degree of polymerization was 51, and its length was 153±17μm and its width was 14±2μm.

[0051] Example 3

[0052] A method for preparing microcrystalline regenerated cellulose using industrial waste gum at room temperature includes the following steps:

[0053] 100g of cellulose slurry was mixed with 800g of NMMO solution (N-methylmorpholine-N-oxide) and then vacuum dehydrated at 100℃ for 3 hours. After degassing, the solution was filtered through a 0.05mm filter to form a uniform spinning solution. This solution was then fed through a metering pump and a booster pump in a melt pipeline to a spinneret pressure of 10MPa. The solution was then spun through a spinneret with 660 holes and a 0.06mm orifice. After exiting the spinneret, the spinning solution passed through an air gap. The air gap temperature was controlled at 20℃, relative humidity at 60% RH, and length at 30mm. The slow cooling airflow rate was controlled at 2m³ / h. 3 / h, temperature is 15℃. Regenerated cellulose is produced in deionized water. After preliminary orientation, the regenerated cellulose is stretched using a draw ratio of 2 times. The roller speed is 20m / min. Positive drawing is used during the spinning process, which makes the produced regenerated cellulose industrial filaments highly oriented. The stretched regenerated cellulose is then washed with water and collected directly as industrial waste glue.

[0054] A desiccator was filled with 250 mL of 10 mol / L hydrochloric acid solution and allowed to stand for 24 hours to allow the hydrochloric acid to evaporate and reach equilibrium. 3.7 g of regenerated cellulose industrial waste gum was taken; its moisture content was tested to be 200%, and its dry weight was calculated to be 1.23 g. The regenerated cellulose waste gum was wrapped around a rack and quickly placed into the desiccator. After 24 hours, it was removed, washed with deionized water until neutral, and then sonicated at 1600 W for 15 minutes. The sonicated cellulose suspension was collected and freeze-dried for 24 hours to obtain MRC.

[0055] The obtained MRC yield was 80.5%, the degree of polymerization was 60, and its length was 152±25μm and its width was 14±2μm.

[0056] Example 4

[0057] A method for preparing microcrystalline regenerated cellulose from industrial waste fibers at room temperature includes the following steps:

[0058] 10g of cellulose slurry was mixed with 90g of [AMIM][Cl] and then vacuum dehydrated at 90℃ for 4 hours. After degassing, the mixture was filtered through a 0.05mm filter to form a uniform spinning solution. This solution was then fed through a metering pump and a booster pump in a melt pipeline to a spinneret pressure of 10MPa. The solution was then spun through a spinneret with 660 holes and a 0.06mm diameter. After exiting the spinneret, the spinning solution passed through an air gap. The air gap temperature was controlled at 20℃, relative humidity at 60% RH, and length at 30mm. The slow cooling airflow rate was controlled at 2m³ / h. 3 / h, temperature 15℃. Regenerated cellulose is produced in deionized water. After initial orientation, the regenerated cellulose is 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 industrial filaments of regenerated cellulose. The stretched regenerated cellulose is then washed with water and dried by three pairs of drying rollers at 80℃ and a roller speed of 40m / min before the industrial waste filaments are collected.

[0059] Fill a desiccator with 200 mL of 12 mol / L hydrochloric acid aqueous solution and let it stand for 24 h to allow the hydrochloric acid to evaporate and reach equilibrium. Wrap 1.5 g of regenerated cellulose waste fibers around a rack, immerse them in water, and quickly place them in the desiccator. After 12 h, remove them, add deionized water, filter and wash until neutral, then sonicate at 1600 W for 10 min. Collect the sonicated cellulose suspension and freeze-dry it for 24 h to obtain MRC.

[0060] The obtained MRC yield was 78.6%, the degree of polymerization was 61, and its length was 158±13μm and its width was 14±2μm.

[0061] Example 5

[0062] A method for preparing microcrystalline regenerated cellulose from industrial waste fibers at room temperature includes the following steps:

[0063] 100g of cellulose slurry was mixed with 800g of NMMO solution and then vacuum dehydrated at 100℃ for 3 hours. After degassing, the solution was filtered through a 0.05mm filter to form a uniform spinning solution. This solution was then fed into a melt pipeline using a metering pump and a booster pump to reach a spinneret pressure of 10MPa. The solution was then spun through a spinneret with 660 holes and a 0.06mm orifice. After exiting the spinneret, the spinning solution passed through an air gap. The air gap temperature was controlled at 20℃, relative humidity at 60% RH, and length at 30mm. The slow cooling airflow rate was controlled at 2m³ / h. 3 / h, temperature 15℃. Regenerated cellulose is produced in deionized water. After initial orientation, the regenerated cellulose is stretched using a 2x draw ratio at a roller speed of 20m / min. Positive drawing is used during the spinning process, resulting in highly oriented industrial cellulose filaments. The stretched regenerated cellulose is then washed with water and dried by three pairs of drying rollers at 80℃ and a roller speed of 20m / min before the industrial waste filaments are collected.

[0064] Fill a desiccator with 250 mL of 10 mol / L hydrochloric acid aqueous solution and let it stand for 24 h to allow the hydrochloric acid to evaporate and reach equilibrium. Wrap 1.5 g of regenerated cellulose waste fibers around a rack, immerse them in water, and quickly place them in the desiccator. After 24 h, remove them, add deionized water, filter and wash until neutral, then sonicate at 1600 W for 15 min. Collect the sonicated cellulose suspension and freeze-dry it for 24 h to obtain MRC.

[0065] The obtained MRC yield was 79.5%, the degree of polymerization was 63, and its length was 154±21μm and its width was 14±2μm.

[0066] Table 1 compares the performance of Examples 1-5 of this invention with that of a commercially available microcrystalline cellulose product (Adamas-beta, LOT. P2354882). The degree of polymerization was tested according to ISO 5351, "Determination of limiting viscosity of pulp in copper-ethylenediamine (CED) solution". Length and width were measured manually using images taken with a ZEISS EVO MA10 scanning electron microscope, with gold sputtering for 30 seconds and an accelerating voltage of 10 kV. Thermal degradation temperature was measured using a NETZSCH / STA2500 thermal analyzer, starting at room temperature and heating to 800°C at a rate of 10°C / min, under a constant nitrogen flow rate of 30 mL / min. Crystallinity was measured using a combined multi-functional horizontal X-ray diffractometer operating at 40 kV and 40 mA, with a scan rate of 0.02 s per step within a measurement range of 5° to 60°, and data analysis was performed using the peak height method.

[0067] Table 1

[0068]

[0069]

[0070] As can be seen from Table 1, the microcrystalline regenerated cellulose prepared by this invention has a low degree of polymerization, a thermal degradation temperature comparable to that of commercially available products, and exhibits superior performance.

[0071] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of individual raw materials in the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing microcrystalline regenerated cellulose using industrial waste glue / filament at room temperature, characterized in that, Includes the following steps: (1) After mixing the cellulose slurry with the solvent, it is dehydrated, then defoamed, filtered, and spun. Then, it is regenerated cellulose is formed in the antisolvent of the coagulation bath. The resulting regenerated cellulose is stretched and washed with water to obtain regenerated cellulose hydrogel. (2) Add the regenerated cellulose hydrogel obtained in step (1) to the hydrochloric acid vapor obtained by evaporating the hydrochloric acid aqueous solution, and let it stand to obtain material A. The standing temperature is 20-30℃, and it is ready for use. (3) Add deionized water to material A obtained in step (2) to wash and obtain regenerated cellulose filter cake. Then add deionized water to the obtained cellulose filter cake and sonicate to obtain cellulose suspension. (4) The cellulose suspension obtained in step (3) is dried to obtain microcrystalline regenerated cellulose; In step (1), the dehydration temperature is 60~120℃, the time is 2~5 h, and the pressure is 2~30 mbar; the spinning process is a pressure of 3~20 MPa, a spinneret orifice diameter of 0.02~0.2 mm, and a number of orifices of 660~3000; the coagulation bath reaction solvent includes, but is not limited to, water and ethanol; and the stretching ratio is 1~10.

2. A method for preparing microcrystalline regenerated cellulose using industrial waste glue / filament at room temperature, characterized in that, Includes the following steps: (1) After mixing the cellulose slurry with the solvent, it is dehydrated, then defoamed, filtered and spun. Then, it is regenerated cellulose is formed in the antisolvent of the coagulation bath. The resulting regenerated cellulose is stretched, washed and dried to obtain regenerated cellulose industrial yarn. (2) After soaking the regenerated cellulose industrial filaments obtained in step (1) in water, add them to the hydrochloric acid vapor obtained by evaporating the hydrochloric acid aqueous solution. After standing, material B is obtained. The standing temperature is 20-30℃. It is ready for use. (3) Add deionized water to the material B obtained in step (2) to wash and obtain regenerated cellulose filter cake. Then add deionized water to the obtained cellulose filter cake and sonicate to obtain cellulose suspension. (4) The cellulose suspension obtained in step (3) is dried to obtain microcrystalline regenerated cellulose; In step (1), the dehydration temperature is 60~120℃, the time is 2~5 h, and the pressure is 2~30 mbar; the spinning process is a pressure of 3~20 MPa, a spinneret orifice diameter of 0.02~0.2 mm, and a number of orifices of 660~3000; the coagulation bath reaction solvent includes, but is not limited to, water and ethanol; and the stretching ratio is 1~10.

3. A method for preparing microcrystalline regenerated cellulose at room temperature using industrial waste glue / filament according to claim 1 or 2, characterized in that, The solvents mentioned in step (1) include, but are not limited to, imidazole ionic liquids and N-methylmorpholine-N-oxides, and the mass ratio of the cellulose slurry to the solvent is 5~15:85~95.

4. The method for preparing microcrystalline regenerated cellulose at room temperature using industrial waste glue / filament according to claim 2, characterized in that, The drying temperature in step (1) is 50~110℃.

5. The method for preparing microcrystalline regenerated cellulose at room temperature using industrial waste glue / filament according to claim 1, characterized in that, In step (2), the concentration of the hydrochloric acid aqueous solution is 6~12mol / L, the ratio of the regenerated cellulose hydrogel to the hydrochloric acid aqueous solution is 1g:50~200mL, and the standing time is 6~48h.

6. The method for preparing microcrystalline regenerated cellulose at room temperature using industrial waste glue / filament according to claim 2, characterized in that, In step (2), the concentration of the hydrochloric acid aqueous solution is 6~12mol / L, the ratio of the regenerated cellulose industrial filament to the hydrochloric acid aqueous solution is 1g:50~200mL, and the standing time is 6~48h.

7. A method for preparing microcrystalline regenerated cellulose at room temperature using industrial waste glue / filament according to claim 1 or 2, characterized in that, In step (3), the ultrasonic power is 1000~2000W and the ultrasonic treatment time is 5~30min.

8. A method for preparing microcrystalline regenerated cellulose at room temperature using industrial waste glue / filament according to claim 1 or 2, characterized in that, In step (4), the drying is either spray drying or freeze drying.

9. A microcrystalline regenerated cellulose prepared by the method according to any one of claims 1 to 8.

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