A method for preparing regenerated cellulose fiber based on corn cob

Abstract

The present invention relates to a method for preparing regenerated cellulose fibers based on corn cobs. The method proposed in the present invention uses corn cobs, which are discarded agricultural and sideline products, as raw materials to prepare dissolving pulp and spin regenerated cellulose fibers, so that corn cobs can be used at a high value, the cost of dissolving pulp can be reduced, the source of raw materials for dissolving pulp can be broadened, and the felling of forest trees can be reduced. By directly using wet corn cob pulp as raw material, the process of pulp drying, reactivation or crushing is omitted, thereby saving energy, shortening the regenerated cellulose fiber manufacturing process and reducing production costs.

Description

Technical Field

[0001] The invention belongs to the field of regenerated cellulose, and in particular relates to a method for preparing regenerated cellulose fibers based on corn cobs. Background Art

[0002] Corn is the most widely grown and produced cereal grain in the world. According to data, global corn production reached 1.129 billion tons in 2021, of which China produced approximately 261 million tons, accounting for 23% of global corn production and second only to the United States. Corncobs, also known as corn cobs, are the cobs of corn (grass) after threshing. They weigh approximately 20%-30% of the corn's weight. Based on a 25% corn yield, the comprehensive and high-value utilization of corncobs is gaining increasing attention to reduce resource waste and environmental pollution caused by burning them.

[0003] Corncobs are primarily composed of cellulose, hemicellulose, and lignin. In addition to these three components, corncobs also contain small or trace amounts of substances such as fats, waxes, resins, tannins, pigments, and inorganic salts. Corncobs are highly nutritious, especially with a high sugar content, making them an ideal raw material for edible fungi production. Patents such as CN107347455B, CN105418283B, and CN109429900A disclose methods for growing edible fungi using corncobs as a culture medium. Furthermore, corncobs can be processed into organic fertilizer and animal feed. Due to their loose structure, corncobs possess excellent adsorption capacity, allowing them to be modified to absorb heavy metals from water and dyes from printing and dyeing wastewater. Their lightweight and thermal insulation properties make them suitable for use as concrete modifiers, fillers in adhesives, and rubber additives. However, these applications offer limited added value.

[0004] Currently, a small portion of corncobs has been highly utilized, primarily for the production of xylo-oligosaccharides, xylose, xylitol, furfural, and more. CN1680415A provides a method for producing xylo-oligosaccharides using corncobs as raw materials. The resulting xylo-oligosaccharides are high in purity and light in color, making them widely used as additives in various foods, health products, and pharmaceuticals. CN113861140A discloses a method for producing high-purity furfural using corncobs as raw materials, sulfuric acid as a catalyst, and toluene and papermaking wastewater as solvents through heating, extraction, and distillation. CN101220381A provides a method for producing xylitol using corncobs or agricultural and forestry waste, such as straw, as raw materials. These inventions primarily utilize the hemicellulose in corncobs, while cellulose is not well utilized.

[0005] Lyocell fiber has experienced rapid development in China in recent years due to its excellent performance and environmentally friendly production process. Currently, China's Lyocell fiber production capacity ranks first in the world. However, the main raw material for producing Lyocell fiber is imported wood pulp. Therefore, it is of positive significance to actively expand the raw material sources of dissolving pulp, improve the quality of dissolving pulp, and reduce dissolving pulp. In summary, my country is rich in corn cob resources, but the added value of corn cob applications in agriculture and animal husbandry is generally low. Currently, the industry mainly separates cellulose and hemicellulose, and uses hemicellulose to produce related chemical products such as xylose, xylitol, and furfural. Only a small portion of cellulose waste is used to prepare nanocrystalline cellulose and bioethanol, and most of it is directly discarded and not well utilized. If cellulose waste is made into dissolving pulp, it can not only greatly improve the comprehensive utilization rate of corn cob resources and the added value of products, but also alleviate the pressure on dissolving pulp. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing regenerated cellulose fibers based on corn cobs.

[0007] A method for preparing regenerated cellulose fiber of the present invention comprises:

[0008] (1) Corncob crushing:

[0009] washing and drying the corn cobs and then crushing them to obtain crushed corn cobs;

[0010] (2) Alkali extraction:

[0011] adding sodium hydroxide solution to the crushed corn cobs, treating at 40-90° C. for 80-140 minutes to remove most of the hemicellulose in the corn cobs, and filtering to obtain a filter residue;

[0012] (3) Sulfate cooking:

[0013] Adding cooking liquid to the filter residue of step (2), sealing and heating to cook, filtering, separating, and washing to obtain cooked corn cobs;

[0014] (4) Metal ion removal:

[0015] adding the cooked corn cobs into a metal ion removal solution, treating the corn cobs at 50-70° C. for 50-70 minutes, filtering, separating, and washing to obtain corn cobs treated for metal ion removal;

[0016] (5) Bleaching

[0017] adding the bleaching liquid to the corn cob after metal ion removal treatment, treating at 50-70° C. for 50-90 minutes, filtering, washing, and pressing to obtain corn cob pulp;

[0018] (6) Lyocell fiber spinning:

[0019] The corncob pulp and N-methylmorpholine oxide (NMMO) of step (5) are mixed and stirred, vacuumed, and mechanically stirred.

[0020] The spinning solution is obtained and put into a coagulation bath for coagulation and forming, and then drawn, washed and dried to obtain regenerated cellulose fiber. The preferred method of the above preparation method is as follows:

[0021] The cleaning in step (1) is performed in water to remove dust and other impurities on the surface of the corn cob; and the corn cob is crushed into particles of 0.5 to 1 mm.

[0022] In the step (2), the solid-liquid ratio is 1:10-18, and the concentration of the sodium hydroxide solution is 50-100 g / L; the filtration is performed by filtering with a 200-mesh filter to separate the solid residue and the extract, and the filter residue is not washed with water and is directly used for subsequent cooking after squeezing.

[0023] The steps (2) and (3) are processed in an electric rotary cooking pot.

[0024] The solid-liquid ratio in step (3) is 1:4-10; the amount of sodium hydroxide in the cooking liquid is 18-28wt%, and the amount of sodium sulfide is 15-25wt%; the cooking temperature is 155-170°C, and the cooking time is 100-160 minutes.

[0025] The filtering, separation and cleaning in step (3) are as follows: using a 200-mesh filter to separate the black liquor from the pulp, and using deionized water to clean the corncob pulp until it is neutral.

[0026] In step (4), the solid-to-liquid ratio is 1:10-14; the demetallization solution is prepared by dissolving 0.3-1.0 wt% of sodium ethylenediaminetetraacetate (EDTA) and 0.3-1.0 wt% of sodium hexametaphosphate (SHMP) in water, and adjusting the pH to 1-5 with H2SO4. Further preferably, the sodium ethylenediaminetetraacetate (EDTA) is present in an amount of 0.4-0.8 wt%; and the sodium hexametaphosphate (SHMP) is present in an amount of 0.4-0.8 wt%.

[0027] In the step (4), the filtration separation and washing are as follows: the slurry is separated using a 300-mesh filter and washed with deionized water until it becomes neutral.

[0028] The solid-liquid ratio in step (5) is 1:10-14; the bleaching solution is prepared by dissolving 0.02-1 wt% MgSO4, 1-4 wt% NaSiO3, and 0.5-1.2 wt% NaOH in deionized water in sequence, and finally adding 1-5 wt% H2O2;

[0029] The filtering, washing and pressing are as follows: using a 300-mesh filter to separate the slurry, washing with deionized water until neutral, and then pressing, and controlling the moisture content of the corn cob to be 50-100 wt%.

[0030] The corncob pulp in step (5) has a polymerization degree of 450-710, a methyl fiber content ≥85%, a whiteness ≥75%, an ash content ≤0.15%, and an iron content ≤15 ppm.

[0031] Further preferably, the corncob pulp has a polymerization degree of 500-550, a methyl fiber content ≥92%, a whiteness ≥78%, an ash content ≤0.05%, and an iron content ≤12 ppm.

[0032] In the step (6), the mass ratio of corncob pulp to NMMO is 12-24:100; and the mass percentage concentration of NMMO is 80%.

[0033] Furthermore, the NMMO is obtained by distilling N-methylmorpholine oxide (NMMO) solvent with a mass concentration of 50% under reduced pressure and concentrating it to 80%.

[0034] The vacuuming in step (6) is performed at 80-110°C; the spinning solution enters a coagulation bath for coagulation and formation: the spinning solution is metered by a metering pump under a nitrogen pressure of 0.3-0.5 MPa and then extruded from the micropores of the spinneret, passing through an air section of 10-80 mm and entering the coagulation bath, wherein the concentration of the coagulation bath is 0-20 wt% and the solution is coagulated and formed in a coagulation bath at 5-30°C.

[0035] The mass percentage concentration of the spinning solution in step (6) is 6-15%; the coagulation bath is an aqueous solution of NMMO. The solid-liquid ratio in the present invention is a mass ratio.

[0036] The present invention provides regenerated cellulose fiber prepared by the method.

[0037] The preparation method includes the following steps: crushing washed corncobs into particles; extracting the corncobs with a sodium hydroxide solution to remove most of the hemicellulose; steaming the corncobs using a sulfate process to remove lignin; treating the corncobs with an acidic chelating agent aqueous solution to remove metal ions; bleaching the corncobs with hydrogen peroxide; and directly using wet corncob pulp as a raw material, dissolving it in N-methylmorpholine oxide (NMMO) and producing Lyocell fibers using a dry-jet wet spinning method. The method proposed in the present invention uses corncobs, a waste agricultural byproduct, as a raw material to prepare dissolving pulp and spin regenerated cellulose fibers. This method allows for high-value utilization of corncobs, reduces the cost of dissolving pulp, broadens the raw material source for dissolving pulp, and reduces deforestation. Using wet corncob pulp directly as a raw material eliminates the pulp drying, reactivation, or pulverization steps, thereby saving energy, shortening the regenerated cellulose fiber manufacturing process, and reducing production costs.

[0038] Beneficial effects

[0039] (1) The use of corncobs, a by-product of corn grain production, to prepare dissolving pulp not only reduces the environmental impact of corncob burning, improves the comprehensive utilization rate and added value of corncobs, but also reduces the dependence of dissolving pulp production on trees, thereby reducing the felling of forest trees and benefiting environmental protection.

[0040] (2) Corncobs are abundant, renewable, and inexpensive. The dissolving pulp prepared from them is low-cost. Using them to prepare regenerated cellulose fibers can reduce the cost of fiber products, thereby improving the economic benefits of production enterprises and the market competitiveness of products, and promoting the development of the Lyocell fiber industry.

[0041] (3) The preparation method disclosed in the present invention directly uses wet corncob pulp as raw material, eliminating the energy consumption required for pulp drying. At the same time, wet pulp is conducive to its dispersion, swelling and dissolution in NMMO, and a spinning solution with uniform quality can be obtained. It also reduces the pulp activation process in the Lyocell fiber production process, shortens the regenerated cellulose fiber manufacturing process and saves costs.

[0042] (4) The present invention uses corn cobs, an agricultural byproduct, as raw materials to prepare dissolving pulp through processes such as crushing, alkali extraction, cooking, metal ion removal, and bleaching. The dissolving pulp has a high α-cellulose content and low metal ion and ash content, so that the prepared solution has good stability and spinnability, and Lyocell fibers are further spun, and the spun fibers have excellent performance. DETAILED DESCRIPTION

[0043] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0044] Corncobs were provided by Shandong Yucheng Shengzhiyuan Agricultural Technology Co., Ltd. Pulp ash and iron content were tested according to standard FZ / T 50010.6-1998; average degree of polymerization was tested according to the copper-ethylenediamine solution method in FZ / T 50010.3-2011; cellulose alpha content was tested according to FZ / T 50010.4-2011; whiteness was determined according to FZ / T 50010.7-1998. Before testing, the pulp was dried, ground into a powder in a mortar, and then flattened in a sample preparation device for testing. Fiber mechanical properties were tested according to GB-T 14337-2008, Test Method for Tensile Properties of Chemical Staple Fibers.

[0045] Example 1

[0046] (1) Washing the threshed corn cobs with water to remove dust and impurities on the surface of the corn cobs, air-drying them, and then crushing them into particles of 0.5 to 1 mm;

[0047] (2) Weigh 600 g of corn cobs and place them in an electric rotary cooking pot. Add 7.2 L of 70 g / L sodium hydroxide solution, maintain a solid-liquid ratio of 1:12, and heat to 70°C for 120 min. After the treatment, filter the solid residue and extract with a 200-mesh filter to separate the solid residue and extract. Use an ethanol-acetic acid mixture (volume ratio 9:1) to extract the hemicellulose in the filtrate for other uses. The filter residue is not washed with water. After pressing, 1100 g of filter residue with a moisture content of approximately 70 wt% is directly used for subsequent cooking.

[0048] (3) The filter residue is placed in an electric rotary cooking pot. Cooking liquid is added at a solid-liquid ratio of 1:6 to ensure that the solids are immersed. The heating time is about 40-60 minutes. The cooking liquid contains 23wt% alkali and 20wt% sodium sulfide. The cooking temperature is 165°C and the cooking time is 100 minutes. After the cooking is completed, the black liquor and pulp are separated with a 200-mesh filter. The pulp is washed with deionized water to neutrality and pressed to a moisture content of about 70%. Since the raw material is granular, the cooking is relatively uniform, the pulp is loose, and there are no large particles of impurities. Therefore, it does not need to be beaten or screened and can be directly used for subsequent processing.

[0049] (4) Dissolve 0.4 wt% of sodium ethylenediaminetetraacetate (EDTA) and 0.4 wt% of sodium hexametaphosphate (SHMP) in deionized water, and adjust the pH to 1.5 with H2SO4 to obtain a deionized solution. Weigh approximately 300 g of the cooked pulp with an absolute dry mass and place it in a sealed bag. Pour the demetallization solution into the sealed bag at a solid-liquid ratio of 1:12, knead and mix thoroughly, and place in a water bath at 60°C for 60 min. Knead and mix every 10 min. After treatment, separate the pulp using a 300-mesh filter, wash with deionized water until neutral, and press for subsequent processing.

[0050] (5) Dissolve 0.05 wt% MgSO4, 2 wt% NaSiO3, and 1 wt% NaOH in deionized water in sequence, and finally add 3 wt% H2O2 to prepare a bleaching solution. Weigh approximately 300 g of the pulp treated in step (4) with an absolute dry mass and place it in a sealed bag. Add the bleaching solution at a solid-to-liquid ratio of 1:12, place it in a water bath at 60°C and treat for 70 min. During this period, knead and mix it every 10 min. After the pulp is separated using a 300-mesh filter, washed with deionized water until neutral, and then squeezed to obtain approximately 900 g of wet corncob pulp with a moisture content of approximately 70%. The pulp specifications are shown in Table 1.

[0051] (6) The 50% NMMO solvent was concentrated to 80% by mass by vacuum distillation. Then, approximately 2970 g of the corncob pulp and 80% NMMO were added to a dissolving kettle, thoroughly mixed and stirred, and then vacuumed and mechanically stirred at 90°C until the cellulose was completely dissolved to obtain a cellulose spinning solution with a concentration of 9 wt%. The prepared spinning solution was metered by a metering pump under a nitrogen pressure of 0.3 MPa and extruded from the micropores of the spinneret. The solution passed through a 30 mm air section (between the spinneret surface and the coagulation bath surface) and entered the coagulation bath, which was water at a temperature of 20°C. Lyocell fibers were obtained after drawing, washing, and drying. The spinning state of the pulp and the fiber properties are shown in Table 2.

[0052] Example 2

[0053] Steps (1) to (2) are the same as in Example 1.

[0054] (3) The filter residue is placed in an electric rotary cooking pot. The cooking liquid is added at a solid-liquid ratio of 1:6 to ensure that the solids are immersed. The heating time is about 40-60 minutes. The cooking liquid contains 28wt% alkali and 23wt% sodium sulfide. The cooking temperature is 165°C and the cooking time is 130 minutes. After the cooking is completed, the black liquor and pulp are separated with a 200-mesh filter. The pulp is washed with deionized water to neutrality and pressed to a moisture content of about 70wt%. Since the raw material is granular, the cooking is relatively uniform, the pulp is loose, and there are no large particles of impurities. Therefore, it does not need to be beaten or screened and can be directly used for subsequent processing.

[0055] (4) Dissolve 0.4 wt% of sodium ethylenediaminetetraacetate (EDTA) and 0.2 wt% of sodium hexametaphosphate (SHMP) in deionized water, and adjust the pH to 1.5 with H2SO4 to obtain a deionized solution. Weigh approximately 300 g of the cooked pulp with an absolute dry mass and place it in a sealed bag. Pour the demetallization solution into the sealed bag at a solid-liquid ratio of 1:12, knead and mix thoroughly, and place in a water bath at 60°C for 60 min. Knead and mix every 10 min. After the treatment, separate the pulp with a 300-mesh filter, wash with deionized water until neutral, and press for subsequent processing.

[0056] (5) Dissolve 0.05 wt% MgSO4, 2 wt% NaSiO3, and 1 wt% NaOH in deionized water in sequence, and finally add 1 wt% H2O2 to prepare a bleaching solution. Weigh approximately 300 g of the pulp treated in step (4) with an absolute dry mass and place it in a sealed bag. Add the bleaching solution at a solid-to-liquid ratio of 1:12, place it in a water bath at 60°C and treat for 70 min. During this period, knead and mix it every 10 min. After the pulp is separated using a 300-mesh filter, washed with deionized water until neutral, and then squeezed to obtain approximately 900 g of wet corncob pulp with a moisture content of approximately 70 wt%. The pulp specifications are shown in Table 1.

[0057] (6) The 50% NMMO solvent was concentrated to 80% by weight by vacuum distillation. Then, approximately 2380 g of the corncob pulp and 80% NMMO were added to a dissolving kettle, thoroughly mixed and stirred, and then vacuumed and mechanically stirred at 90°C until the cellulose was completely dissolved to obtain a cellulose spinning solution with a concentration of 11 wt%. The prepared spinning solution was metered by a metering pump under a nitrogen pressure of 0.3 MPa and extruded from the micropores of the spinneret. The solution passed through a 50 mm air section (between the spinneret surface and the coagulation bath surface) and entered the coagulation bath, which was water at a temperature of 20°C. Lyocell fibers were obtained after drawing, washing, and drying. The spinning state of the pulp and the fiber properties are shown in Table 2.

[0058] Example 3

[0059] Steps (1) to (3) are the same as in Example 2.

[0060] (4) Dissolve 0.4 wt% of sodium ethylenediaminetetraacetate (EDTA) and 0.8 wt% of sodium hexametaphosphate (SHMP) in deionized water, and adjust the pH to 1.5 with H2SO4 to obtain a deionized solution. Weigh approximately 300 g of the cooked pulp with an absolute dry mass and place it in a sealed bag. Pour the demetallization solution into the sealed bag at a solid-liquid ratio of 1:12, knead and mix thoroughly, and place in a water bath at 60°C for 60 min. Knead and mix every 10 min. After treatment, separate the pulp with a 300-mesh filter, wash with deionized water until neutral, and press for subsequent processing.

[0061] (5) Dissolve 0.05 wt% MgSO4, 2 wt% NaSiO3, and 1 wt% NaOH in deionized water in sequence, and finally add 5 wt% H2O2 to prepare a bleaching solution. Weigh approximately 300 g of the pulp treated in step (4) with an absolute dry mass and place it in a sealed bag. Add the bleaching solution at a solid-to-liquid ratio of 1:12, place it in a water bath at 60°C and treat for 70 min. During this period, knead and mix it every 10 min. After the pulp is separated using a 300-mesh filter, washed with deionized water until neutral, and then squeezed to obtain approximately 900 g of wet corncob pulp with a moisture content of approximately 70 wt%. The pulp specifications are shown in Table 1.

[0062] (6) The 50% NMMO solvent was concentrated to 80% by weight by vacuum distillation. Then, approximately 2380 g of the corncob pulp and 80% NMMO were added to a dissolving kettle. After thorough mixing and stirring, the mixture was vacuumed and mechanically stirred at 90°C until the cellulose was completely dissolved to obtain a cellulose spinning solution with a concentration of 11 wt%. The prepared spinning solution was metered by a metering pump under a nitrogen pressure of 0.3 MPa and extruded from the micropores of the spinneret. The solution passed through a 30 mm air section (between the spinneret surface and the coagulation bath surface) and entered the coagulation bath, which was water at a temperature of 20°C. Lyocell fibers were obtained after drawing, washing, and drying. The spinning state of the pulp and the fiber properties are shown in Table 2.

[0063] Example 4

[0064] Steps (1) to (3) are the same as in Example 1.

[0065] (4) Dissolve 0.2 wt% of sodium ethylenediaminetetraacetate (EDTA) and 0.2 wt% of sodium hexametaphosphate (SHMP) in deionized water, and adjust the pH to 3.5 with H2SO4 to obtain a deionized solution. Weigh approximately 300 g of the cooked pulp with an absolute dry mass and place it in a sealed bag. Pour the demetallization solution into the sealed bag at a solid-liquid ratio of 1:12, knead and mix thoroughly, and place in a water bath at 60°C for 60 min. Knead and mix every 10 min. After treatment, separate the pulp with a 300-mesh filter, wash with deionized water until neutral, and press for subsequent processing.

[0066] (5) Dissolve 0.05 wt% MgSO4, 2 wt% NaSiO3, and 1 wt% NaOH in deionized water in sequence, and finally add 2 wt% H2O2 to prepare a bleaching solution. Weigh approximately 300 g of the pulp treated in step (4) with an absolute dry mass and place it in a sealed bag. Add the bleaching solution at a solid-to-liquid ratio of 1:12, place it in a water bath at 60°C and treat for 70 min. During this period, knead and mix it every 10 min. After the pulp is separated using a 300-mesh filter, washed with deionized water until neutral, and then squeezed to obtain approximately 900 g of wet corncob pulp with a moisture content of approximately 70 wt%. The pulp specifications are shown in Table 1.

[0067] (6) The 50% NMMO solvent was concentrated to 80% by weight by vacuum distillation. Then, approximately 2970 g of the corncob pulp and 80% NMMO were added to a dissolving kettle, thoroughly mixed and stirred, and then vacuumed and mechanically stirred at 90°C until the cellulose was completely dissolved to obtain a cellulose spinning solution with a concentration of 9 wt%. The prepared spinning solution was metered by a metering pump under a nitrogen pressure of 0.3 MPa and extruded from the micropores of the spinneret. The solution passed through a 50 mm air section (between the spinneret surface and the coagulation bath surface) and entered the coagulation bath, which was water at a temperature of 15°C. Lyocell fibers were obtained after drawing, washing, and drying. The spinning state of the pulp and the fiber properties are shown in Table 2.

[0068] Comparative Example 1

[0069] Steps (1) to (3) are the same as in Example 1.

[0070] (4) Dissolve 0.2 wt% sodium ethylenediaminetetraacetate (EDTA) in deionized water and adjust the pH to 4.5 with H2SO4 to obtain a deionized solution. Weigh approximately 300 g of the cooked pulp with an absolute dry mass and place it in a sealed bag. Pour the demetallization solution into the sealed bag at a solid-liquid ratio of 1:12, knead and mix thoroughly, and place in a water bath at 60°C for 60 min. Knead and mix every 10 min. After treatment, separate the pulp using a 300-mesh filter, wash with deionized water until neutral, and press for subsequent processing.

[0071] (5) Dissolve 0.05 wt% MgSO4, 2 wt% NaSiO3, and 1 wt% NaOH in deionized water in sequence, and finally add 5 wt% H2O2 to prepare a bleaching solution. Weigh approximately 300 g of the pulp treated in step (4) with an absolute dry mass and place it in a sealed bag. Add the bleaching solution at a solid-to-liquid ratio of 1:12, place it in a water bath at 60°C and treat for 90 min. During this period, knead and mix it every 10 min. After the pulp is separated using a 300-mesh filter, washed with deionized water until neutral, and then squeezed to obtain approximately 900 g of wet corncob pulp with a moisture content of approximately 70 wt%. The pulp specifications are shown in Table 1.

[0072] (6) The 50% NMMO solvent was concentrated to 80% by weight by vacuum distillation. Then, approximately 2970 g of the corncob pulp and 80% NMMO were added to a dissolving kettle, thoroughly mixed and stirred, and then vacuumed and mechanically stirred at 90°C until the cellulose was completely dissolved to obtain a cellulose spinning solution with a concentration of 9 wt%. The prepared spinning solution was metered by a metering pump under a nitrogen pressure of 0.3 MPa and extruded from the micropores of the spinneret. The solution passed through a 50 mm air section (between the spinneret surface and the coagulation bath surface) and entered the coagulation bath, which was water at a temperature of 20°C. Lyocell fibers were obtained after drawing, washing, and drying. The spinning state of the pulp and the fiber properties are shown in Table 2.

[0073] Comparative Example 2

[0074] Commercial wood pulp (DP=633, α-cellulose content 91.1%) was pulverized into 2 cm x 2 cm pieces. A 50% NMMO solvent was concentrated to 74% by weight by vacuum distillation. Approximately 220 g of the pulverized wood pulp and 2090 g of the 74% NMMO solvent were added to a dissolving kettle, mixed, and allowed to swell for 30 minutes. The mixture was then vacuum-dehydrated at 90°C with mechanical stirring to completely dissolve the cellulose, producing a spinning solution with an 11% wt% concentration. The prepared spinning solution was then metered by a metering pump under 0.3 MPa nitrogen pressure and extruded through the micropores of a spinneret. The solution passed through a 50 mm air gap (between the spinneret surface and the coagulation bath) and entered a coagulation bath of 15°C water. Lyocell fibers were then drawn, washed, and dried to obtain the resulting fibers. The spinning state and fiber properties of the pulp are shown in Table 2.

[0075] Table 1 Corncob pulp and commercial wood pulp indicators

[0076]

[0077]

[0078] Table 2 Spinning state and fiber properties of corncob pulp and commercial wood pulp

[0079]

[0080] As can be seen from Tables 1 and 2, in Examples 1 and 4, it is relatively difficult to obtain a uniform spinning solution because the prepared pulp has a relatively high degree of polymerization, and the pulp prepared in Example 4 has high ash and iron contents, resulting in poor spinning performance.

Claims

1. A method for preparing regenerated cellulose fiber, comprising: (1) washing and drying corn cobs and then crushing them to obtain crushed corn cobs; (2) Add sodium hydroxide solution to the crushed corn cob, treat at 40-90°C for 80-140 minutes, filter, Obtaining filter residue; (3) adding a cooking liquid to the filter residue from step (2), sealing the filter residue, heating the mixture, performing cooking, filtering, separating, and washing the mixture to obtain cooked corn cobs; wherein the amount of sodium hydroxide in the cooking liquid is 18-28 wt %, and the amount of sodium sulfide is 15-25 wt %; the cooking temperature is 155-170° C., and the cooking time is 100-160 min; (4) adding the cooked corn cobs to a demetallization solution, treating the corn cobs at 50-70° C. for 50-70 min, filtering, separating, and washing to obtain corn cobs treated for metal ion removal; the solid-to-liquid ratio is 1:10-14; wherein the demetallization solution is prepared by dissolving 0.3-1.0 wt% of sodium ethylenediaminetetraacetate (EDTA) and 0.3-1.0 wt% of sodium hexametaphosphate (SHMP) in water in sequence, and adjusting the pH value to 1-1.5 with H2SO4; (5) adding a bleaching liquid to the corncob after metal ion removal treatment, treating at 50-70° C. for 50-90 min, filtering, washing, and pressing to obtain corncob pulp; the corncob pulp in step (5) has a degree of polymerization of 450-710, a methyl fiber content of ≥85%, a whiteness of ≥75%, an ash content of ≤0.05%, and an iron content of ≤15 ppm; (6) The corncob pulp and N-methylmorpholine oxide (NMMO) of step (5) are mixed and stirred, vacuumed, and mechanically stirred to obtain a spinning solution, which is placed in a coagulation bath for coagulation and forming, and then drawn, washed, and dried to obtain regenerated cellulose fibers.

2. The preparation method according to claim 1, characterized in that The cleaning in step (1) is performed in water; and the powder is crushed into particles of 0.5 to 1 mm.

3. The preparation method according to claim 1, characterized in that: In the step (2), the solid-liquid ratio is 1:10-18, and the concentration of the sodium hydroxide solution is 50-100 g / L; the filtration is performed by filtering with a 200-mesh filter to separate the solid residue and the extract, and the filter residue is not washed with water and is directly used for subsequent cooking after squeezing.

4. The preparation method according to claim 1, characterized in that In step (3), the solid-liquid ratio is 1:4-10; The filtering, separation and cleaning in step (3) are as follows: using a 200-mesh filter to separate the black liquor from the pulp, and using deionized water to clean the corncob pulp until it is neutral.

5. The preparation method according to claim 1, characterized in that: In the step (4), the filtration separation and washing are as follows: the slurry is separated using a 300-mesh filter and washed with deionized water until it becomes neutral.

6. The preparation method according to claim 1, characterized in that: The solid-liquid ratio in step (5) is 1:10-14; the bleaching solution is prepared by dissolving 0.02-1 wt% MgSO4, 1-4 wt% NaSiO3, and 0.5-1.2 wt% NaOH in deionized water in sequence. Finally, add 1-5 wt% H2O2; The filtering, washing and pressing are as follows: using a 300-mesh filter to separate the slurry, washing with deionized water until neutral, and then pressing, and controlling the moisture content of the corn cob to be 50-100 wt%.

7. The preparation method according to claim 1, characterized in that: In the step (6), the mass ratio of corncob pulp to NMMO is 12-24:100; and the mass percentage concentration of NMMO is 80%.

8. The preparation method according to claim 1, characterized in that: The vacuuming in step (6) is performed at 80-110°C; the spinning solution enters a coagulation bath for coagulation and formation: the spinning solution is metered by a metering pump under a nitrogen pressure of 0.3-0.5 MPa and then extruded from the micropores of the spinneret, passing through an air section of 10-80 mm and entering the coagulation bath, wherein the concentration of the coagulation bath is 0-20 wt% and the solution is coagulated and formed in a coagulation bath at 5-30°C.

9. A regenerated cellulose fiber prepared by the method of claim 1.

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