Method for extracting cellulose from straw and application thereof

Abstract

The invention belongs to the technical field of crop biological resource utilization, particularly relates to a method for extracting cellulose from straw and application of the method, and aims to solve the problem that the cellulose in the straw is difficult to directly utilize. The straw is subjected to negative-pressure dust removal, activation pretreatment and mechanical grinding, rubbing and tearing, and then cellulose is separated out through biological enzyme. According to the method for extracting the cellulose, the cellulose can be efficiently and green separated, and the method can be used for preparing fibers, films and hydrogel materials; the invention further provides a method for preparing the regenerated cellulose fiber, the cellulose fiber with the strength larger than 1.5 cN / dtex can be obtained, the cellulose fiber has excellent mechanical performance and appropriate moisture regain and can be used in the field of high-end textiles, and the additional value of straw cellulose is greatly increased.

Description

Technical Field

[0001] The invention belongs to the technical field of crop biological resource utilization, and particularly relates to a method for extracting cellulose. Background Art

[0002] Natural plant fiber is an extremely abundant renewable resource. It is widely present in plant straw in various forms. Straw fiber has attracted much attention due to its unique renewability and environmental protection characteristics. Especially for a large agricultural country like my country, a large amount of concentrated fiber agricultural waste is produced every year, such as corn straw and rice straw. These straws contain rich natural resources and are rich in natural polymers such as cellulose, hemicellulose and lignin. These components make straw have huge potential utilization value and can be converted into various valuable products, such as biofuels, bio-based materials, paper, etc. However, due to its tight internal structure, cellulose, hemicellulose and lignin are fused with each other, which makes direct utilization difficult. Therefore, how to effectively break these natural barriers of straw and realize its high-value utilization has become a key issue that needs to be solved in the current field of agricultural waste resource utilization.

[0003] Cellulose is a linear polymer compound formed by glucose units connected by β-1,4-glycosidic bonds. It is the most widely distributed and abundant substance in nature and the largest biomass resource in the plant kingdom. Its molecular structure contains hydroxyl active groups, so it can undergo many chemical reactions such as oxidation, reduction, hydrolysis, alcoholysis, sulfonation, alkylation, halogenation, nitration, polycondensation or graft copolymerization, and has high utilization value. Patent CN200810240326.6 discloses a method of first soaking the plant body in dilute alkali, then pressurizing steam, grinding and washing the pulp to obtain cellulose. The method needs to be carried out in stages, the process is cumbersome, and the cellulose is not utilized after removal, which has obvious shortcomings. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for extracting cellulose from straw and application thereof.

[0005] The technical solution of the present invention is achieved in this way: The present invention adopts sodium bisulfate and oligoethylene oxide aqueous solution to pretreat the straw, and utilizes the weakly acidic environment of sodium bisulfate to strengthen the hydrogen bond "dissolving" effect between the O atoms in the oligoethylene oxide and the cellulose, thereby changing the supramolecular structure of the cellulose and reducing the bonding energy between the cellulose and the lignin, so that the cellulose can be easily separated under subsequent mechanical and enzyme treatments, and can be used for the preparation of fibers, films, and hydrogel materials.

[0006] On the one hand, the present application proposes a method for extracting lignin from straw, the steps of which are as follows: (1) The straw is subjected to negative pressure dust removal and activation pretreatment, and then torn, ground and crushed to obtain straw fiber; (2) Adding a maturing agent to the straw fiber and stirring at high speed, performing ultrasound-assisted maturation, and filtering to obtain a precipitate, which is cellulose. Preferably, the activation pretreatment in the above step (1) is to spray a 3-10 wt% aqueous solution of sodium bisulfite and oligoethylene oxide on the surface of the straw for 60-300 min, wherein the mass of the aqueous solution is 10-30 wt% of the mass of the straw; and the number average molecular weight of the oligoethylene oxide is 500-2000.

[0007] Preferably, in the above step (1), the tearing time is 1-5 min; the grinding time is 1-5 min; the average length of the straw fiber does not exceed 10 mm, and the fineness is less than 500 μm.

[0008] Preferably, in the above step (2), the ripening agent is a composite system composed of laccase, pectinase, cellulose hydrolase and ethylene glycol, the total concentration of the composite system is 1000-6000 U / L, the dosage is 2-15 wt% of the total mass of the straw, wherein the concentration of laccase is 300-2000 U / L, the concentration of pectinase is 200-1500 U / L, the concentration of cellulose hydrolase is 500-2500 U / L, and the concentration of ethylene glycol is 10-100 g / L; the time of high-speed stirring is 20-60 min, and the time of ultrasonic-assisted ripening is 30-40 min.

[0009] On the other hand, the cellulose extracted by the above method is used in the preparation of straw regenerated cellulose fibers.

[0010] Preferably, the above application comprises the following steps: (1) dissolving cellulose in a spinning solvent, and obtaining a spinning solution after degassing and filtering; (2) Add polyvinyl alcohol or polyethylene oxide to the spinning solution, heat and extrude it through a screw, and then enter the coagulation bath after passing through an air gap. After stretching, water washing and heat setting, straw regenerated cellulose fiber is obtained.

[0011] Preferably, in the above step (1), the mass fraction of cellulose is 18-29%; and the spinning solvent is any one of ionic liquid, N-methoxymorpholine and phosphoric acid / polyphosphoric acid.

[0012] Preferably, in the above step (2), the weight average molecular weight of polyvinyl alcohol or polyethylene oxide is greater than 100,000, and the mass fraction is 0.5-2 wt %; the screw heating temperature is 35-80° C., and the air gap length is 0-100 mm.

[0013] Preferably, in the above step (2), the coagulation bath is a mixture of spinning solvent and water, the mass fraction of the spinning solvent is 10-30 wt%, the temperature of the coagulation bath is 20-50°C, and the length is 80-150 cm; the stretching times are twice, and the drafting ratios are 1.1-1.3 times and 1.2-1.5 times respectively; the heat setting is tensile heat setting with a tension of 10-100 cN and a temperature of 80-110°C; and the mechanical strength of the straw regenerated cellulose is greater than 1.5 cN / dtex.

[0014] The present invention has the following beneficial effects: 1. The present application pretreats the straw with sodium bisulfate and oligoethylene oxide aqueous solution, and utilizes the weakly acidic environment of sodium bisulfate to strengthen the "dissolving" effect of the hydrogen bonds between the O atoms in the oligoethylene oxide and the cellulose, thereby changing the supramolecular structure of the cellulose and reducing the binding energy between the cellulose and the lignin, so that the cellulose can be separated efficiently and greenly under subsequent mechanical and enzyme treatments, and can be used for the preparation of fibers, films and hydrogel materials. The technology of the present application has the characteristics of simple process and environmental protection.

[0015] 2. The present application also provides a method for preparing regenerated cellulose fibers by liquid crystal spinning of straw cellulose, which utilizes the high orientation and low viscosity rheological properties of the liquid crystal fluid under shear, and then obtains cellulose fibers with a strength of >1.5cN / dtex through secondary stretching and heat setting. These fibers have excellent mechanical properties and a suitable moisture regain, can be used in the field of high-end textiles, and greatly increase the added value of straw cellulose. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is the infrared spectrum of cellulose extracted in Example 1.

[0018] Figure 2 This is the morphology of cellulose extracted in Example 1.

[0019] Figure 3 The stress-strain curve of the regenerated cellulose fiber prepared in Example 1.

[0020] Figure 4 This is a morphology diagram of the regenerated cellulose fiber prepared in Example 1. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Unless otherwise specified, the experimental methods used in the following experimental examples are all conventional methods; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0023] The present application uses sodium bisulfate and oligoethylene oxide aqueous solution to pretreat the straw, and utilizes the weakly acidic environment of sodium bisulfate to strengthen the hydrogen bond "dissolving" effect between the O atoms in the oligoethylene oxide and the cellulose, thereby changing the supramolecular structure of the cellulose and reducing its bonding energy with the lignin, so that it can be easily separated under subsequent mechanical and enzyme treatments, and can be used for the preparation of fibers, films, and hydrogel materials.

[0024] Example 1 This embodiment provides a method for extracting cellulose from straw and the application of preparing regenerated cellulose fiber by spinning the extracted straw cellulose liquid crystal. The specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 3 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 500 was sprayed on the surface for 60 min, with the mass of the aqueous solution being 10 wt% of the mass of the straw. The straw was then torn for 1 min and ground for 1 min to obtain straw fibers.

[0025] (2) A composite system ripening agent consisting of 300 U / L laccase, 200 U / L pectinase, 500 U / L cellulose hydrolase and 10 g / L ethylene glycol was added to the straw fiber at a rate of 2 wt% of the total mass of the straw. The mixture was stirred at high speed for 20 min and then subjected to assisted ultrasound for 30 min. After filtration, cellulose with a content of 91% was obtained.

[0026] (3) Finally, cellulose with a mass percentage of 18% by weight of the solvent was dissolved in the ionic liquid, and the spinning solution was obtained by degassing and filtering. 0.5 wt% of polyvinyl alcohol with a weight average molecular weight of 110,000 was added to the spinning solution, and the spinning solution was heated to 35°C and extruded through a screw. After passing through an air gap of 50 mm in length, it entered a coagulation bath with a temperature of 20°C and a length of 80 cm. The ratio of the mass fraction of the spinning solvent to water in the coagulation bath was 1:9. After two stretching times of 1.1 times and 1.5 times respectively, it was washed with water and then subjected to tensile heat setting at a tension of 10 cN and a temperature of 80°C, a straw regenerated cellulose fiber with a mechanical strength of 2.72 cN / dtex was obtained.

[0027] like Figure 1 As shown in the FTIR spectrum of cellulose, at 896 cm -1 At 1060 cm -1 At 1116 cm -1 At 1325 cm -1 At 1650 cm -1 At , the characteristic peak of -OH was observed, indicating that cellulose was successfully prepared. Figure 2 This is a morphology picture of cellulose. The prepared cellulose is in powdery granular form with a small particle size and white with yellow in color. Figure 3 The stress-strain curve of the prepared regenerated cellulose fiber showed that its breaking strength was 4.98 cN, breaking elongation was 18.125%, fineness was 1.83 dtex, and strength was 2.72 cN / dtex, indicating excellent mechanical properties. Figure 4 This is the morphology of regenerated cellulose fiber. The surface is relatively smooth, the fineness is relatively uniform, and it has good textile processing performance.

[0028] Example 2 This embodiment provides a method for extracting cellulose from straw and the use of the extracted straw cellulose liquid crystal spinning to prepare regenerated cellulose fiber, the specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 10 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 2000 was sprayed on the surface for 300 min, with the mass of the aqueous solution being 30 wt% of the mass of the straw. The straw was then torn for 1 min and ground for 1 min to obtain straw fibers.

[0029] (2) A composite system ripening agent consisting of 2000 U / L laccase, 1500 U / L pectinase, 2500 U / L cellulose hydrolase and 10 g / L ethylene glycol was added to the straw fiber at a rate of 15 wt% of the total mass of the straw. The mixture was stirred at high speed for 60 min and then subjected to assisted ultrasound for 40 min. After filtration, cellulose with a content of 94% was obtained.

[0030] (3) Finally, cellulose with a solvent weight of 29% was dissolved in N-methoxymorpholine solution, and the spinning solution was obtained by degassing and filtering. 2 wt% polyethylene oxide with a weight average molecular weight of 150,000 was added to the spinning solution, and the spinning solution was heated to 80°C and extruded through a screw. After passing through an air gap of 100 mm in length, it entered a coagulation bath with a temperature of 40°C and a length of 150 cm. The ratio of the mass fraction of the spinning solvent to water in the coagulation bath was 1:9. After two stretching times of 1.3 times and 1.5 times respectively, it was washed with water and then subjected to tensile heat setting at a tension of 100 cN and a temperature of 110°C, a straw regenerated cellulose fiber with a mechanical strength of 2 cN / dtex was obtained.

[0031] Example 3 This embodiment provides a method for extracting cellulose from straw and the application of preparing regenerated cellulose fiber by spinning the extracted straw cellulose liquid crystal. The specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 5 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 1000 was sprayed on the surface for 60 min, with the mass of the aqueous solution being 30 wt% of the mass of the straw. The straw was then torn for 3 min and ground for 5 min to obtain straw fibers.

[0032] (2) A composite system ripening agent consisting of 2000 U / L laccase, 300 U / L pectinase, 1000 U / L cellulose hydrolase and 50 g / L ethylene glycol was added to the straw fiber at a rate of 2 wt% of the total mass of the straw. The mixture was stirred at high speed for 60 min and then subjected to assisted ultrasound for 40 min. After filtration, cellulose with a content of 93.6% was obtained.

[0033] (3) Finally, cellulose with a solvent weight of 18% was dissolved in a phosphoric acid / polyphosphoric acid solution, and the spinning solution was obtained by degassing and filtering. 0.5 wt% polyvinyl alcohol with a weight average molecular weight of 130,000 was added to the spinning solution, and the spinning solution was heated to 35°C and extruded through a screw. After passing through an air gap of 50 mm in length, it entered a coagulation bath with a temperature of 20°C and a length of 80 cm. The ratio of the mass fraction of the spinning solvent to the water in the coagulation bath was 1:9. After two stretching times of 1.1 times and 1.3 times respectively, it was washed with water and then subjected to tensile heat setting at a tension of 10 cN and a temperature of 80°C to obtain straw regenerated cellulose fiber with a mechanical strength of 1.86 cN / dtex.

[0034] Example 4 This embodiment provides a method for extracting cellulose from straw and the application of preparing regenerated cellulose fiber by spinning the extracted straw cellulose liquid crystal. The specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 10 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 1000 was sprayed on the surface for 150 min. The mass of the aqueous solution was 30 wt% of the mass of the straw. The straw was then torn for 1 min and ground for 5 min to obtain straw fibers.

[0035] (2) A composite system ripening agent consisting of 300 U / L laccase, 1500 U / L pectinase, 1500 U / L cellulose hydrolase and 100 g / L ethylene glycol was added to the straw fiber at a concentration of 2 wt% of the total mass of the straw. The mixture was stirred at high speed for 60 min and then assisted with ultrasound for 40 min. After filtration, cellulose with a content of 93.9% was obtained.

[0036] (3) Finally, cellulose with a solvent weight of 18% was dissolved in an ionic liquid, and a spinning solution was obtained after degassing and filtration. 2 wt% of polyethylene oxide with a weight average molecular weight of 120,000 was added to the spinning solution, and the spinning solution was heated to 35°C and extruded through a screw. After passing through an air gap of 100 mm in length, the spinning solution entered a coagulation bath with a temperature of 30°C and a length of 150 cm. The ratio of the mass fraction of the spinning solvent to water in the coagulation bath was 1:9. After two stretching times of 1.3 times and 1.2 times, respectively, washing, and tensile heat setting at a tension of 100 cN and a temperature of 110°C, straw regenerated cellulose fibers with a mechanical strength of 2.4 cN / dtex were obtained.

[0037] Example 5 This embodiment provides a method for extracting cellulose from straw and the application of preparing regenerated cellulose fiber by spinning the extracted straw cellulose liquid crystal. The specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 3 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 500 was sprayed on the surface for 150 min, with the mass of the aqueous solution being 30 wt% of the mass of the straw. The straw was then torn for 5 min and ground for 5 min to obtain straw fibers.

[0038] (2) A composite system ripening agent consisting of 2000 U / L laccase, 1500 U / L pectinase, 1500 U / L cellulose hydrolase and 100 g / L ethylene glycol was added to the straw fiber at a concentration of 15 wt% of the total mass of the straw. The mixture was stirred at high speed for 60 min and then assisted with ultrasound for 40 min. After filtration, cellulose with a content of 93.5% was obtained.

[0039] (3) Finally, cellulose with a solvent weight of 29% was dissolved in N-methoxymorpholine solution, and the spinning solution was obtained by degassing and filtering. 0.5 wt% of polyethylene oxide with a weight average molecular weight of 130,000 was added to the spinning solution, and the spinning solution was heated to 50°C and extruded through a screw. After passing through an air gap of 80 mm in length, it entered a coagulation bath with a temperature of 40°C and a length of 150 cm. The ratio of the mass fraction of the spinning solvent to water in the coagulation bath was 1:9. After two stretching times of 1.1 times and 1.5 times respectively, it was washed with water and then subjected to tensile heat setting at a tension of 100 cN and a temperature of 110°C, a straw regenerated cellulose fiber with a mechanical strength of 2 cN / dtex was obtained.

[0040] Example 6 This embodiment provides a method for extracting cellulose from straw and the application of preparing regenerated cellulose fiber by spinning the extracted straw cellulose liquid crystal. The specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 10 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 1200 was sprayed on the surface for 60 min, with the mass of the aqueous solution being 10 wt% of the mass of the straw. The straw was then torn for 1 min and ground for 3 min to obtain straw fibers.

[0041] (2) A composite system ripening agent consisting of 300 U / L laccase, 1500 U / L pectinase, 1500 U / L cellulose hydrolase and 100 g / L ethylene glycol was added to the straw fiber at a rate of 15 wt% of the total mass of the straw. The mixture was stirred at high speed for 20 min and then subjected to assisted ultrasound for 40 min. After filtration, cellulose with a content of 92.1% was obtained.

[0042] (3) Finally, cellulose with a solvent weight of 29% was dissolved in an ionic liquid, N-methoxymorpholine or phosphoric acid / polyphosphoric acid solvent system, and a spinning solution was obtained after degassing and filtration. 2 wt% polyethylene oxide with a weight average molecular weight of 110,000 was added to the spinning solution, and the spinning solution was heated to 35°C and extruded through a screw. After passing through an air gap of 50 mm in length, it entered a coagulation bath with a temperature of 40°C and a length of 80 cm. The ratio of the mass fraction of the spinning solvent to water in the coagulation bath was 1:9. After two stretching times of 1.3 times and 1.2 times, respectively, washing, and tensile heat setting at a tension of 50 cN and a temperature of 80°C, straw regenerated cellulose fibers with a mechanical strength of 1.7 cN / dtex were obtained.

[0043] Example 7 This embodiment provides a method for extracting cellulose from straw and the application of preparing regenerated cellulose fiber by spinning the extracted straw cellulose liquid crystal. The specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 3 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 500 was sprayed on the surface for 300 min. The mass of the aqueous solution was 15 wt% of the mass of the straw. The straw was then torn for 5 min and ground for 1 min to obtain straw fibers.

[0044] (2) A composite system ripening agent consisting of 2000 U / L laccase, 1500 U / L pectinase, 2500 U / L cellulose hydrolase and 50 g / L ethylene glycol was added to the straw fiber at a rate of 2 wt% of the total mass of the straw. The mixture was stirred at high speed for 60 min and then subjected to assisted ultrasound for 40 min. After filtration, cellulose with a content of 92.5% was obtained.

[0045] (3) Finally, 18% of the cellulose by weight was dissolved in an ionic liquid, N-methoxymorpholine or phosphoric acid / polyphosphoric acid solvent system, and the spinning solution was obtained by degassing and filtering. 0.5 wt% of polyethylene oxide with a weight average molecular weight of 120,000 was added to the spinning solution, and the spinning solution was extruded by heating the screw to 80°C. The spinneret was directly immersed in a coagulation bath with a temperature of 30°C and a length of 80 cm (i.e., the air gap length was 0 mm). The ratio of the mass fraction of the spinning solvent to the water in the coagulation bath was 1:9. After two stretching times of 1.1 times and 1.5 times, respectively, washing, and then tense heat setting at a tension of 100 cN and a temperature of 80°C, straw regenerated cellulose fibers with a mechanical strength of 2.1 cN / dtex were obtained.

[0046] Example 8 This embodiment provides a method for extracting cellulose from straw and the application of preparing regenerated cellulose fiber by spinning the extracted straw cellulose liquid crystal. The specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 10 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 2000 was sprayed on the surface for 60 min, with the mass of the aqueous solution being 10 wt% of the mass of the straw. The straw was then torn for 1 min and ground for 3 min to obtain straw fibers.

[0047] (2) A composite system ripening agent consisting of 400 U / L laccase, 300 U / L pectinase, 500 U / L cellulose hydrolase and 30 g / L ethylene glycol was added to the straw fiber at a rate of 15 wt% of the total mass of the straw. The mixture was stirred at high speed for 20 min and then subjected to assisted ultrasound for 30 min. After filtration, cellulose with a content of 92.3% was obtained.

[0048] (3) Finally, cellulose with a solvent weight of 20% was dissolved in a phosphoric acid / polyphosphoric acid solution, and the spinning solution was obtained by degassing and filtering. 2 wt% polyvinyl alcohol with a weight average molecular weight of 110,000 was added to the spinning solution, and the spinning solution was heated to 35°C and extruded through a screw. After passing through an air gap of 50 mm in length, it entered a coagulation bath with a temperature of 30°C and a length of 150 cm. The ratio of the mass fraction of the spinning solvent to water in the coagulation bath was 1:9. After two stretching times of 1.3 times and 1.5 times respectively, it was washed with water and then subjected to tensile heat setting at a tension of 10 cN and a temperature of 80°C, a straw regenerated cellulose fiber with a mechanical strength of 1.65 cN / dtex was obtained.

[0049] Example 9 This embodiment provides a method for extracting cellulose from straw and the use of the extracted straw cellulose liquid crystal spinning to prepare regenerated cellulose fiber, the specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 3 wt% sodium bisulfite and oligomeric ethylene oxide with a molecular weight of 1000 was sprayed on the surface for 300 min. The mass of the aqueous solution was 30 wt% of the mass of the straw. The straw was then torn for 5 min and ground for 1 min to obtain straw fibers.

[0050] (2) A composite system ripening agent consisting of 2000 U / L laccase, 1500 U / L pectinase, 2500 U / L cellulose hydrolase and 100 g / L ethylene glycol was added to the straw fiber at a concentration of 2 wt% of the total mass of the straw. The mixture was stirred at high speed for 60 min and then assisted with ultrasound for 40 min. After filtration, cellulose with a content of 91.4% was obtained.

[0051] (3) Finally, cellulose with a solvent weight of 30% was dissolved in an ionic liquid, and a spinning solution was obtained after degassing and filtration. 0.5 wt% of polyethylene oxide with a weight average molecular weight of 110,000 was added to the spinning solution, and the spinning solution was heated to 40°C and extruded through a screw. After passing through an air gap of 100 mm in length, the spinning solution entered a coagulation bath with a temperature of 40°C and a length of 80 cm. The ratio of the mass fraction of the spinning solvent to water in the coagulation bath was 1:9. After two stretching times of 1.1 and 1.2 respectively, washing with water, and then tense heat setting at a tension of 80 cN and a temperature of 80°C, straw regenerated cellulose fibers with a mechanical strength of 2.23 cN / dtex were obtained.

[0052] Example 10 This embodiment provides a method for extracting cellulose from straw and the use of the extracted straw cellulose liquid crystal spinning to prepare regenerated cellulose fiber, the specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 10 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 2000 was sprayed on the surface for 60 min, with the mass of the aqueous solution being 10 wt% of the mass of the straw. The straw was then torn for 1 min and ground for 5 min to obtain straw fibers.

[0053] (2) A composite system ripening agent consisting of 400 U / L laccase, 300 U / L pectinase, 1000 U / L cellulose hydrolase and 50 g / L ethylene glycol was added to the straw fiber at a rate of 15 wt% of the total mass of the straw. The mixture was stirred at high speed for 20 min and then subjected to assisted ultrasound for 40 min. After filtration, cellulose with a content of 91.6% was obtained.

[0054] (3) Finally, cellulose with a solvent weight of 30% was dissolved in an ionic liquid, N-methoxymorpholine or phosphoric acid / polyphosphoric acid solvent system, and a spinning solution was obtained after degassing and filtration. 1 wt% polyvinyl alcohol with a weight average molecular weight of 120,000 was added to the spinning solution, and the spinning solution was heated to 35°C and extruded through a screw. After passing through an air gap of 100 mm in length, the spinning solution entered a coagulation bath with a temperature of 40°C and a length of 100 cm. The ratio of the mass fraction of the spinning solvent to the water in the coagulation bath was 1:9. After two stretching times of 1.3 times and 1.5 times, respectively, washing, and tensile heat setting at a tension of 50 cN and a temperature of 80°C, straw regenerated cellulose fibers with a mechanical strength of 2.12 cN / dtex were obtained.

[0055] Embodiment 11 This embodiment provides a method for extracting cellulose from straw and the use of the extracted straw cellulose liquid crystal spinning to prepare regenerated cellulose fiber, the specific steps are as follows: (1) The straw was subjected to negative pressure dust removal, and an aqueous solution of 10 wt% sodium bisulfite and oligoethylene oxide with a molecular weight of 2000 was sprayed on the surface for 300 min, with the mass of the aqueous solution being 10 wt% of the mass of the straw. The straw was then torn for 3 min and ground for 5 min to obtain straw fibers.

[0056] (2) A composite system ripening agent consisting of 400 U / L laccase, 300 U / L pectinase, 2500 U / L cellulose hydrolase and 10 g / L ethylene glycol was added to the straw fiber at a rate of 10 wt% of the total mass of the straw. The mixture was stirred at high speed for 40 min and then subjected to assisted ultrasound for 35 min. After filtration, cellulose with a content of 91.6% was obtained.

[0057] (3) Finally, cellulose with a solvent weight of 30% was dissolved in an ionic liquid, N-methoxymorpholine or phosphoric acid / polyphosphoric acid solvent system, and a spinning solution was obtained after degassing and filtration. 1 wt% polyvinyl alcohol with a weight average molecular weight of 120,000 was added to the spinning solution, and the spinning solution was heated to 50°C and extruded through a screw. After passing through an air gap of 100 mm in length, the spinning solution entered a coagulation bath with a temperature of 45°C and a length of 100 cm. The ratio of the mass fraction of the spinning solvent to the water in the coagulation bath was 1:9. After two stretching times of 1.2 times and 1.5 times, respectively, washing, and then tense heat setting at a tension of 50 cN and a temperature of 100°C, straw regenerated cellulose fibers with a mechanical strength of 1.95 cN / dtex were obtained.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting cellulose from straw, characterized in that: Here are the steps: (1) The straw is subjected to negative pressure dust removal and activation pretreatment, and then torn, ground and crushed to obtain straw fiber; (2) Add a maturation agent to the straw fiber and stir to mix well, perform ultrasound-assisted maturation, and filter press to obtain a precipitate, which is cellulose.

2. The method for extracting cellulose from straw according to claim 1, characterized in that: In the step (1), the activation pretreatment is to spray an aqueous solution of sodium bisulfite and oligoethylene oxide on the surface of the straw for a treatment time of 60-300 minutes, the concentration of sodium bisulfite is 3-10 wt%, the mass of the aqueous solution is 10-30 wt% of the mass of the straw; and the number average molecular weight of the oligoethylene oxide is 500-2000.

3. The method for extracting cellulose from straw according to claim 2, characterized in that: In the step (1), the average length of the straw fibers does not exceed 10 mm, and the average fineness is less than 500 μm.

4. The method for extracting cellulose from straw according to claim 3, characterized in that: In the step (2), the ripening agent is a composite system composed of laccase, pectinase, cellulose hydrolase and ethylene glycol, the total concentration of the composite system is 1000-6000 U / L, and the dosage is 2-15 wt% of the total mass of the straw, wherein the concentration of laccase is 300-2000 U / L, the concentration of pectinase is 200-1500 U / L, the concentration of cellulose hydrolase is 500-2500 U / L, and the concentration of ethylene glycol is 10-100 g / L.

5. The method for extracting cellulose from straw according to claim 4, characterized in that: The time for ultrasound-assisted ripening in step (2) is 30-40 min.

6. Use of cellulose extracted by the method according to any one of claims 1 to 5 in preparing straw regenerated cellulose fibers.

7. The use according to claim 6, characterized in that: Here are the steps: (1) dissolving cellulose in a spinning solvent, and obtaining a spinning solution after degassing and filtering; (2) Add polyvinyl alcohol or polyethylene oxide to the spinning solution, heat and extrude it through a screw, and then enter the coagulation bath after passing through an air gap. After stretching, water washing and heat setting, straw regenerated cellulose fiber is obtained.

8. The use according to claim 7, characterized in that: The mass fraction of cellulose in step (1) is 18-29%; the spinning solvent is any one of ionic liquid, N-methoxymorpholine and phosphoric acid / polyphosphoric acid.

9. The use according to claim 8, characterized in that: In the step (2), the weight average molecular weight of polyvinyl alcohol or polyethylene oxide is greater than 100,000, and the mass fraction is 0.5-2 wt %; the screw heating temperature is 35-80° C., and the air gap length is 0-100 mm.

10. The use according to claim 9, characterized in that: In the step (2), the coagulation bath is a mixture of spinning solvent and water, the mass fraction of the spinning solvent is 10-30 wt%, the temperature of the coagulation bath is 20-50°C, and the length is 80-150 cm; the stretching times are two, and the drafting ratios are 1.1-1.3 times and 1.2-1.5 times respectively; the heat setting is tensile heat setting with a tension of 10-100 cN and a temperature of 80-110°C.

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