Method for preparing lyocell fiber using bagasse as raw material

Abstract

The invention relates to a method for preparing lyocell fiber by using bagasse as a raw material. The method comprises the following steps: step A, crushing the bagasse to 40-80 meshes to obtain bagasse powder; step B, adding the bagasse powder obtained in step A into a first solution, and obtaining pretreated bagasse powder after reaction; step C, adding the pretreated bagasse powder obtained in step B into a second solution, and obtaining bagasse cellulose after reaction; step D, adding the bagasse cellulose obtained in step C into an NMMO aqueous solution with a mass fraction of 85-88%, stirring and dissolving the solution in a reactor at 90-110° C. under vacuum conditions for 3-5 hours to obtain a transparent spinning solution, wherein the mass fraction of the bagasse cellulose in the solution is 6-10%; and step E, feeding the spinning solution obtained in step D into a spinning system for spinning.

Description

Technical Field

[0001] The invention relates to a method for preparing lyocell fiber by taking bagasse as raw material. Background Art

[0002] The increasing depletion of fossil resources has led people to pay more and more attention to renewable resources. Regenerated cellulose fiber has a very broad development prospect because its raw materials are renewable and its performance is similar to or even better than that of cotton. Cellulose is the most abundant renewable organic material with outstanding properties and many valuable applications. However, it cannot be melted or dissolved in conventional solvents due to its partially crystalline structure bound by hydrogen bonds. The production of cellulose fibers in China is mainly based on viscose fiber production technology, which is produced through metastable soluble cellulose derivatives (cellulose xanthate). The process is accompanied by environmental pollution and the generation of harmful by-products. Therefore, vigorously developing green and environmentally friendly new solvent-based cellulose fibers, improving the level of existing traditional regenerated cellulose fiber production technology, reducing environmental pollution, developing high-value-added differentiated regenerated cellulose fibers, and promoting industrial structure upgrading are the main tasks of major viscose fiber producing countries like my country in the future.

[0003] Lyocell fiber production involves dissolving cellulose directly in an aqueous solution of N-methylmorpholine-N-oxide (NMMO) followed by a specialized wet spinning process. This process produces cellulose fibers that exhibit high dry and wet strength, are comfortable to wear, are biodegradable, and feature a simple and advanced production process that is environmentally friendly. The NMMO solvent can be recovered and recycled, potentially fundamentally addressing the critical issue of sustainable development in the textile industry.

[0004] Currently, the main methods for producing lyocell fiber are as follows: Application Publication No. CN110230111A discloses a method for producing lyocell fiber using poplar wood as the raw material. Using poplar wood as the raw material, wood pulp cellulose is produced through processes such as sealed steaming, alkali treatment, and dissolution and precipitation using a LiCl / dimethylacetamide mixed solvent. The wood pulp cellulose is then dissolved in N-methylmorpholine-N-oxide to produce a spinning solution, which is then fed into a spinning system for spinning. Finally, the fiber strands are treated with alcohol washing, water washing, oiling, and drying to produce lyocell fiber. Application Publication No. CN109234826A discloses a method for producing lyocell fiber using bamboo as the raw material. Using bamboo as the raw material, cellulose is extracted from the bamboo through processes such as degumming, delignification, and hemicellulose removal. The bamboo cellulose is then dissolved in an aqueous solution of N-methylmorpholine-N-oxide to produce a spinning solution. The spinning solution enters a spinning system for spinning to form fibers. The fibers are then subjected to alcohol washing, bleaching, water washing, oiling, and drying to produce Lyocell fibers. The Lyocell fibers produced in this method have a dry breaking strength of 44-47 cN / tex, a dry breaking elongation of 13%-15%, a wet breaking strength of 29-32 cN / tex, and a wet breaking elongation of 15%-17%. Application Publication No. CN112813713A discloses a method for preparing pulp specifically for producing Lyocell fibers from bamboo and willow. The method comprises the following steps: a bamboo willow chip preparation step, a neutral high-temperature prehydrolysis step, an alkaline high-temperature cooking step, a coarse pulp washing and screening step, an oxygen delignification step, a multi-stage bleaching step, a multi-stage washing step, an acidification and chelating treatment step, a low-concentration sand removal and screening step, and a finished pulp papermaking step.

[0005] Although lyocell fibers can be produced from a variety of raw materials, most of them have problems such as difficulty in purification, complex sources of raw materials, and low cellulose recovery rates.

[0006] Based on the above issues, the applicant conducted research on the above issues and resulted in this case. Summary of the Invention

[0007] The object of the present invention is to provide a method for preparing lyocell fiber using bagasse as raw material, which is simpler in process, environmentally friendly and can reduce costs.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing lyocell fiber using bagasse as raw material comprises the following steps:

[0010] Step A, crushing bagasse into 40-80 mesh to obtain bagasse powder;

[0011] Step B, placing the bagasse powder obtained in step A into a first solution, stirring at 60-80° C. for 2-5 hours, filtering and washing after the reaction, drying the filter residue, and then crushing it into 40-80 mesh to obtain pretreated bagasse powder, wherein the first solution includes 0.5-1% by mass of hydrogen peroxide, 1-5% by mass of sodium hydroxide, and the balance of water, and the mass ratio of the first solution to the bagasse powder is 30-10:1;

[0012] Step C, adding the pretreated bagasse powder obtained in step B into a second solution, soaking it at 70-90° C. for 3-5 hours, filtering and washing it to neutrality after the reaction, and drying the filter residue in an oven at 50-70° C. to obtain bagasse cellulose, wherein the second solution comprises 15-17.5 mol / L glacial acetic acid, 10-15 g / L sodium hypochlorite, and the remainder water, and the mass ratio of the second solution to the pretreated bagasse powder is 20-25:1;

[0013] Step D, adding the bagasse cellulose obtained in step C to an 85-88% by mass NMMO aqueous solution, stirring and dissolving it in a reactor at 90-110° C. under vacuum conditions for 3-5 hours to obtain a transparent spinning solution, wherein the bagasse cellulose accounts for 6-10% by mass of the solution;

[0014] Step E: feeding the spinning solution obtained in step D into a spinning system for spinning.

[0015] As a preferred embodiment of the present invention, in step A, the sugarcane bagasse is crushed and treated in a water bath at 60-80° C. for 3-5 hours, filtered and washed, and then dried at 60-70° C. for 10-12 hours to obtain sugarcane bagasse powder.

[0016] As a preferred embodiment of the present invention, in step D, the NMMO aqueous solution with a mass fraction of 85-88% is obtained by distilling under reduced pressure the NMMO aqueous solution with a mass fraction of 45-50%.

[0017] As a preferred embodiment of the present invention, in step B, the drying is carried out under vacuum conditions at a drying temperature of 50-70°C.

[0018] As a preferred embodiment of the present invention, in step E, before entering the spinning system, the spinning solution is added to a screw extruder, dissolved at 90-130° C. for 10-20 minutes, and then filtered.

[0019] As a preferred embodiment of the present invention, step E, entering the spinning system, the ejected silk thread is vertically stretched in the air, enters the coagulation bath, and coagulates into shape. The coagulation bath temperature is 15-25 ° C, and the coagulation bath uses an aqueous solution of NMMO with a mass fraction of 15-20%. After that, the fiber is washed with alcohol, bleached, washed with water, oiled, and dried.

[0020] As a preferred embodiment of the present invention, the mass concentration of ethanol in the alcohol washing is 75-95%, and the alcohol washing time is 3-4 hours.

[0021] As a preferred embodiment of the present invention, the bleaching adopts a 0.1-0.3 g / L strong chlorine aqueous solution, a bleaching temperature of 30-50° C., and a bleaching time of 30-60 min.

[0022] As a preferred embodiment of the present invention, in step E, the water washing temperature is 70-90° C. and the washing time is 2-3 h.

[0023] As a preferred embodiment of the present invention, in step E, the drying temperature is 55-65° C. and the drying time is 22-26 hours.

[0024] According to the technical solution of the present invention, bagasse is selected as the raw material for preparing lyocell fiber. The cellulose content in bagasse is high and the lignin content is low. The cellulose purification process is relatively simple, which greatly reduces the production cost. The separation and purification of cellulose in bagasse is directly related to the purity of the cellulose. When the purity of the cellulose is lower than 90%, the cellulose cannot be completely dissolved in the solvent, which directly affects the uniformity of the spinning solution, causing the ejected silk thread to break or the strength of the prepared lyocell fiber to be greatly reduced. The lyocell fiber prepared by the present invention has a dry breaking strength between 2.8 and 4.0 cN / dtex, a wet breaking strength between 2.5 and 3.5 cN / dtex, and an elongation at break between 12% and 15%, which can meet the performance requirements of the fiber. The purification process of sugarcane cellulose and the production process of lyocell fiber are both green and environmentally friendly, and have good promotion and application prospects. DETAILED DESCRIPTION

[0025] In order to better understand the technical solution of the present invention, it is described in more detail below with reference to embodiments.

[0026] Implementation Case 1

[0027] Weigh 100g of bagasse, crush it to 80 mesh, stir it in a 70°C water bath for 3 hours, filter it, wash it with distilled water, and dry it at 60°C for 10 hours to obtain clean bagasse powder. Weigh 50g of the clean bagasse powder and add it to a beaker. Add 1000g of a mixed solution of 0.5% hydrogen peroxide and 5% sodium hydroxide to the beaker, and stir it magnetically in a 70°C water bath for 3 hours to pretreat the bagasse. After the reaction is completed, filter it, wash it until neutral, and place the filter residue in a vacuum dryer at 60°C to dry it. Then crush it to 60 mesh for later use. Weigh 10 g of the crushed filter residue and immerse it in a mixed solution of glacial acetic acid and sodium hypochlorite with a total mass of 250 g. The glacial acetic acid concentration in the mixed solution is 17.5 mol / L, the sodium hypochlorite concentration is 10 g / L, the treatment temperature is 90°C, and the immersion time is 3 h. After the reaction is completed, filter and wash until neutral, and place the filter residue in an oven and dry it at 60°C to obtain sugarcane bagasse cellulose.

[0028] A 50% (by mass) aqueous solution of NMMO (N-methylmorpholine-N-oxide) was distilled under reduced pressure to a 15% (by mass) NMMO solution. A 50% (by mass) NMMO solution is relatively stable, while a 15% (by mass) NMMO solution is suitable for dissolving cellulose. 3g of bagasse cellulose was slowly added to 47g of the 15% (by mass) NMMO solution, mixed thoroughly, and dissolved in a reactor at 90°C under vacuum for 3 hours to produce a uniform, transparent spinning solution with a 6% (by mass) content. The spinning solution is added to a screw extruder and further dissolved at 110° C. for 20 minutes. The solution is then filtered and fed into a spinning system. The spinning solution is spun at a spinning speed of 20 m / min. The spun yarns are vertically stretched in the air and fed into a coagulation bath, which is a 15% by mass NMMO aqueous solution at 20° C. The fiber is then alcohol-washed (with an ethanol concentration of 75% and an alcohol washing time of 3 hours), bleached (with a bleaching agent, strong chlorine, at a temperature of 30° C. for 60 minutes), washed (with pure water at 80° C. for 2 hours), oiled (with an oil bath solution concentration of 2 g / L and a temperature of 70° C. for 4 hours, using the oil bath oil model: HY-101, produced by Hangzhou Huaya Chemical Co., Ltd.), and dried (at a drying temperature of 60° C. for 24 hours). The resulting lyocell fiber has a dry breaking strength of 3.0 cN / dtex, a wet breaking strength of 2.7 cN / dtex, and an elongation at break of 12%.

[0029] Implementation Case 2

[0030] Weigh 100g of bagasse, crush it to 80 mesh, stir it in a 70°C water bath for 3 hours, filter it, wash it with distilled water, and dry it at 60°C for 10 hours to obtain clean bagasse powder. Weigh 50g of the clean bagasse powder and add it to a beaker. Add 1000g of a mixed solution of 0.8% hydrogen peroxide and 5% sodium hydroxide to the beaker, and stir it magnetically in a 70°C water bath for 3 hours to pretreat the bagasse. After the reaction is completed, filter it, wash it until it is neutral, and place the filter residue in a vacuum dryer at 60°C to dry it. Then crush it to 60 mesh for later use. Weigh 10 g of the crushed filter residue and immerse it in a mixed solution of glacial acetic acid and sodium hypochlorite with a total mass of 250 g, wherein the glacial acetic acid concentration is 17.5 mol / L, the sodium hypochlorite concentration is 10 g / L, the treatment temperature is 90°C, and the immersion time is 3 h. After the reaction is completed, filter and wash until neutral, and place the filter residue in an oven and dry it at 60°C to obtain sugarcane bagasse cellulose.

[0031] A 50% NMMO aqueous solution was distilled under reduced pressure to a 15% NMMO solution. 4g of bagasse cellulose was slowly added to 46g of the 15% NMMO solution, mixed thoroughly, and dissolved in a reactor at 100°C under vacuum for 3 hours to produce a uniform, transparent spinning solution with a mass fraction of 8%. The spinning solution is added to a screw extruder and further dissolved at 110° C. for 20 minutes. The solution is then filtered and fed into a spinning system. The spinning solution is spun at a spinning speed of 20 m / min. The ejected yarns are vertically stretched in the air and fed into a coagulation bath, which is a 15% by mass aqueous solution of NMMO at a temperature of 20° C. The fiber is then alcohol-washed (with an ethanol concentration of 75% and an alcohol washing time of 3 hours), bleached (with a bleaching agent of 0.1 g / L chloranil at a temperature of 30° C. for 60 minutes), washed (with pure water at 80° C. for 2 hours), oiled (with an oil bath solution concentration of 2 g / L at a temperature of 70° C. for 4 hours, using an oil bath model: HY-101, produced by Hangzhou Huaya Chemical Co., Ltd.), and dried (at a drying temperature of 60° C. for 24 hours). The resulting lyocell fiber has a dry breaking strength of 3.3 cN / dtex, a wet breaking strength of 3.1 cN / dtex, and an elongation at break of 14%.

[0032] Implementation Case 3

[0033] Weigh 100g of bagasse, crush it to 80 mesh, stir it in a 70°C water bath for 3 hours, filter it, wash it with distilled water, and dry it at 60°C for 10 hours to obtain clean bagasse powder. Weigh 50g of the clean bagasse powder and add it to a beaker. Add 1000g of a mixed solution of 1% hydrogen peroxide and 5% sodium hydroxide to the beaker, and stir it magnetically in a 70°C water bath for 3 hours to pretreat the bagasse. After the reaction is completed, filter it, wash it until it is neutral, and place the filter residue in a vacuum dryer at 60°C to dry it. Then crush it to 60 mesh for later use. Weigh 10 g of the crushed filter residue and immerse it in a mixed solution of glacial acetic acid and sodium hypochlorite with a total mass of 250 g, wherein the glacial acetic acid concentration is 17.5 mol / L, the sodium hypochlorite concentration is 10 g / L, the treatment temperature is 90°C, and the immersion time is 3 h. After the reaction is completed, filter and wash until neutral, and place the filter residue in an oven and dry it at 60°C to obtain sugarcane bagasse cellulose.

[0034] A 50% NMMO aqueous solution was distilled under reduced pressure to a 15% NMMO solution. 4g of bagasse cellulose was slowly added to 46g of the 15% NMMO solution, mixed thoroughly, and dissolved in a reactor at 100°C under vacuum for 3 hours to produce a uniform, transparent spinning solution with a mass fraction of 8%. The spinning solution is added to a screw extruder and further dissolved at 110° C. for 20 minutes. The solution is then filtered and fed into a spinning system. The spinning solution is spun at a spinning speed of 20 m / min. The ejected yarns are vertically stretched in the air and fed into a coagulation bath, which is a 20% by mass aqueous solution of NMMO at a temperature of 30° C. The fiber is then alcohol-washed (with an ethanol concentration of 75% and an alcohol washing time of 3 hours), bleached (with a bleaching agent of 0.1 g / L chloranil at a temperature of 30° C. for 60 minutes), washed (with pure water at 80° C. for 2 hours), oiled (with an oil bath solution concentration of 3 g / L at a temperature of 70° C. for 4 hours, using an oil bath model: HY-101, produced by Hangzhou Huaya Chemical Co., Ltd.), and dried (at a drying temperature of 60° C. for 24 hours). The resulting lyocell fiber has a dry breaking strength of 3.7 cN / dtex, a wet breaking strength of 3.4 cN / dtex, and an elongation at break of 15%.

[0035] The dry and wet breaking strength and elongation at break of this application are all tested in accordance with the national standard "GB / T14337-2022 Test method for tensile properties of chemical fiber staple fibers".

[0036] The separation and purification of cellulose from bagasse is directly related to the purity of the cellulose. When the purity of the cellulose is lower than 90%, the cellulose cannot be completely dissolved in the solvent, which directly affects the uniformity of the spinning solution, causing the ejected silk threads to break or the strength of the prepared lyocell fiber to be greatly reduced. In the extraction process of the present invention, the purity of the cellulose is ≥95%. The degree of polymerization of the cellulose has a decisive influence on the viscosity and spinnability of the final spinning solution, and also affects the physical properties of the finished fiber. In theory, the higher the pulp polymerization degree, the higher the finished fiber strength, but the greater the difficulty of spinning. The cellulose polymerization degree of the present invention is 500-650, which is suitable for spinning.

[0037] Of course, the protection scope of the present invention is not limited to this embodiment, and anyone making similar changes thereto shall be deemed to be within the scope of patent protection of the present invention.

Claims

1. A method for preparing lyocell fiber using bagasse as raw material, characterized in that: The steps include: Step A, crushing bagasse to 80 mesh to obtain bagasse powder; Step B, placing the bagasse powder obtained in step A into a first solution, stirring at 70° C. for 3 hours, filtering and washing after the reaction, drying the filter residue, and then crushing it into 60 mesh to obtain pretreated bagasse powder, wherein the first solution includes 1% by mass of hydrogen peroxide, 5% by mass of sodium hydroxide, and the balance of water, and the mass ratio of the first solution to the bagasse powder is 20:1; Step C, adding the pretreated bagasse powder obtained in step B into a second solution, soaking it at 90° C. for 3 hours, filtering and washing it until it is neutral after the reaction, and drying the filter residue in an oven at 60° C. to obtain bagasse cellulose, wherein the second solution comprises 17.5 mol / L glacial acetic acid, 10 g / L sodium hypochlorite, and the remainder water, and the mass ratio of the second solution to the pretreated bagasse powder is 25:1; Step D, adding the bagasse cellulose obtained in step C to an 85% by mass NMMO aqueous solution, stirring and dissolving the solution in a reactor at 100° C. under vacuum conditions for 3 hours to obtain a transparent spinning solution, wherein the bagasse cellulose accounts for 4 / 46 by mass of the solution; Step E, feeding the spinning solution obtained in step D into a spinning system for spinning; In step A, the sugarcane bagasse is crushed and treated in a water bath at 70° C. for 3 hours, filtered and washed, and then dried at 60° C. for 10 hours to obtain sugarcane bagasse powder; in step D, an 85% by mass NMMO aqueous solution is obtained by vacuum distillation of a 50% by mass NMMO aqueous solution.

2. A method for preparing lyocell fiber using bagasse as raw material according to claim 1, characterized in that: In step B, drying is carried out under vacuum conditions at a drying temperature of 60°C.

3. A method for preparing lyocell fiber using bagasse as raw material as claimed in claim 2, characterized in that: Step E: Before entering the spinning system, the spinning solution is added to a screw extruder and dissolved at 110° C. for 20 minutes, and then filtered.

4. A method for preparing lyocell fiber using bagasse as raw material as claimed in claim 3, characterized in that: Step E: Entering the spinning system, the ejected silk thread is vertically stretched in the air and enters the coagulation bath to solidify and form. The coagulation bath temperature is 30°C, and the coagulation bath uses an aqueous solution of NMMO with a mass fraction of 20%. After that, the fiber is washed with alcohol, bleached, washed with water, oiled, and dried.

5. The method for preparing lyocell fiber using bagasse as raw material according to claim 4, wherein: The mass concentration of ethanol in the alcohol washing is 75%, and the alcohol washing time is 3 hours.

6. The method for preparing lyocell fiber using bagasse as raw material according to claim 5, wherein: The bleaching was carried out using a 0.1 g / L strong chlorine aqueous solution, a bleaching temperature of 30° C., and a bleaching time of 60 min.

7. The method for preparing lyocell fiber using bagasse as raw material according to claim 6, wherein: In step E, the water washing temperature is 80° C. and the time is 2 h.

8. The method for preparing lyocell fiber using bagasse as raw material according to claim 7, wherein: In step E, the drying temperature is 60° C. and the drying time is 24 h.