Bamboo powder raw material suitable for lyocell fiber production and preparation method thereof

Abstract

The invention discloses a bamboo powder raw material suitable for lyocell fiber production and a preparation method of the bamboo powder raw material, and belongs to the technical field of lyocell fibers.The bamboo powder raw material suitable for lyocell fiber production is prepared by conducting two alkali treatment procedures on bamboo powder obtained after bamboo wood is smashed and ground and then conducting subsequent bleaching, acid pickling and drying treatment, and then the bamboo pulp raw material suitable for lyocell fiber production is obtained. Compared with a traditional pulping and papermaking cooking process and oxygen delignification process, the method has the advantages that the conditions are milder, the equipment requirement is lower, the production energy consumption is lower, the operation is safer, the indexes of the finally prepared raw materials can meet the lyocell production requirement, the operation process is simpler, and the method has great industrial application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of lyocell fibers, and particularly relates to a bamboo powder raw material suitable for producing lyocell fibers and a preparation method thereof. Background Art

[0002] Lyocell fiber is a new type of regenerated cellulose fiber, hailed as the green fiber of the 21st century. It is produced through a dry-jet wet spinning process, using N-methylmorpholine-N-oxide (NMMO) as a solvent to directly dissolve pulp raw materials without chemical reaction to form a spinning solution. Lyocell fiber is not only soft, silky, breathable, and lustrous, but also possesses superior mechanical properties and hygroscopicity, making it widely used in many textile fields. Currently, Lyocell fiber production is primarily based on wood, most of which is imported wood pulp. To address the problem of reliance on imported wood pulp, research into alternative raw materials for Lyocell fiber production has begun in recent years.

[0003] Bamboo is a unique resource in China. Bamboo pulp, produced using the pre-hydrolysis sulfate process, has successfully replaced wood pulp in viscose fiber production. However, due to the specificity of the production process, bamboo pulp used in lyocell fiber production requires higher quality than conventional viscose bamboo pulp. Existing lyocell bamboo pulp production processes generally require cooking to effectively remove lignin and hemicellulose from the raw material. Cooking requires high temperature and pressure, which places a significant energy burden on the equipment, increasing pulp production costs and increasing operator safety risks.

[0004] For example, Chinese patent CN1129680C discloses a method for producing bamboo lyoceil fiber from bamboo. This method involves crushing the bamboo, pulping it, removing impurities with concentrated alkali, rinsing it, thoroughly rinsing it with an integrator, and drying it to produce bamboo cellulose with a molecular weight greater than 800, which is then used in lyoceil fiber production. Because the pulping process requires high-pressure cooking at 160-180°C, this leads to high energy consumption and production costs.

[0005] For example, Chinese patent CN109234826B discloses a method for preparing lyocell fiber using bamboo as raw material. In this method, bamboo is used as raw material. Small pieces of cleaned raw bamboo are added to 3-5 g / L pectinase and treated at 50-60°C for 35-48 hours for degumming. The bamboo fibers are then immersed in 2-5 g / L sodium hypochlorite solution at 40-50°C for 2-3 hours, and further immersed in sodium hydroxide solution at 90-100°C for 2-3 hours to remove lignin. Finally, the bamboo fibers are placed in a high-temperature, high-pressure, sealed aqueous solution and treated at 170-200°C and 5-10 atm for 2-3 hours to remove hemicellulose, thereby obtaining bamboo pulp for preparing lyocell fiber. However, this patented method uses sodium hypochlorite to remove lignin, which produces chlorine gas and organic chlorides, which are harmful to human health and also burden sewage treatment. It is less environmentally friendly and has low lignin removal efficiency. Secondly, the processing time of bamboo raw materials is too long. The degumming and enzymatic hydrolysis process alone takes more than 36 hours, which results in low pulping efficiency and great difficulty in industrial application. In addition, because it uses a high-temperature and high-pressure water environment to remove hemicellulose from the raw material, the high-pressure treatment at a temperature of 170-200°C will also degrade the cellulose in the raw material, resulting in a reduction in the raw material yield.

[0006] For example, Chinese patent CN113529195A discloses a method for producing lyocell bamboo fiber. The method involves crushing bamboo pulp that meets quality requirements twice to achieve a bulk density of 80g / L or above before using it to produce lyocell bamboo fiber. Although the patent states that the raw material of the bamboo pulp is Sichuan bamboo pulp, the quality indicators are: DP512, 94.8% methylcellulose, 0.18% ash, 0.14% resin, 85% whiteness, and 33mm fine dust. 2 / kg, 4.5% polypentose, 20 mg / kg of iron, 2 mg / kg of copper, 400 mg / kg of calcium, and 60 mg / kg of magnesium, but the patent does not record the preparation process of bamboo pulp with the above quality indicators, and the bamboo pulp with such quality indicators, when used as a raw material for the preparation of lyocell fiber, still has the problems of high ash content and iron ion content. The slightly high ash content will affect the quality of the spinning solution and easily lead to difficulty in filtering the spinning solution; the high iron ion content will easily lead to the decomposition of the solvent NMMO, thereby causing accidents such as explosions, posing a great safety risk.

[0007] Therefore, in the production process of lyocell fiber, developing a high-quality bamboo pulp raw material suitable for its preparation, and at the same time solving the high energy consumption and safety problems brought about by the traditional high-temperature cooking process of bamboo pulp, are key technical difficulties that urgently need to be broken through. Summary of the Invention

[0008] The present invention aims to provide a bamboo powder raw material suitable for lyocell fiber production and a preparation method thereof. The bamboo powder obtained by crushing and grinding bamboo materials is subjected to two alkali treatment processes, and then subjected to subsequent bleaching, acid washing and drying processes to obtain a bamboo pulp raw material for lyocell fiber production. The combined use of these processes is more gentle than the steaming process and oxygen delignification conditions of traditional pulping and papermaking, with lower equipment requirements, lower production energy consumption and safer operation. The indicators of the raw material finally obtained can meet the production requirements of lyocell, the operation process is simpler, and the raw material has great prospects for industrial application.

[0009] The present invention is achieved through the following technical solution: a method for preparing bamboo powder raw materials suitable for lyocell fiber production, which uses bamboo as raw material, and sequentially undergoes crushing and grinding, a first alkali treatment, a second alkali treatment, bleaching, acid washing, and drying to obtain the bamboo powder raw materials for lyocell fiber production. The first alkali treatment is to add the crushed and ground bamboo powder into an alkali solution, and then add H2O2, controlling the mass ratio of bamboo powder, alkali and H2O2 to be 10-20:2-10:0.01-0.1, and then stirring in a closed manner at 60-90°C for 60-150 minutes, and then washing with water and centrifuging and dehydrating to obtain the alkalized bamboo powder after the first alkali treatment. The second alkali treatment is to add the alkalized bamboo powder after the first alkali treatment into the alkali solution, and then add H2O2, and control the mass ratio of the alkalized bamboo powder after the first alkali treatment, alkali and H2O2 to be 10-20:0.1-1:0.01-0.1, and then stir in a closed manner at 60-80°C for 60-150min, wash with water and then centrifuge to dehydrate to obtain the alkalized bamboo powder after the second alkali treatment, and then bleach.

[0010] The mesh size of the bamboo powder after crushing and grinding is 1 to 40 meshes.

[0011] In the first alkali treatment and the second alkali treatment, the alkali used is NaOH or KOH.

[0012] Bleaching involves the following steps: A. adding the alkalized bamboo powder after the second alkali treatment to a chlorine dioxide solution, and then adding hydrochloric acid, controlling the mass ratio of the alkalized bamboo powder after the second alkali treatment, chlorine dioxide, and hydrochloric acid to be 10-20:0.01-0.1:0.01-0.1, and then stirring in a closed manner at 60-70° C. for 60-120 minutes, and then washing with water and centrifuging and dehydrating to obtain a first-stage bleached bamboo powder; B. adding a first-stage bleached bamboo powder to an alkaline solution, and then adding H2O2, controlling the mass ratio of the first-stage bleached bamboo powder, alkali, and H2O2 to be 10-20:0.01-0.5:0.01-0.1, and then stirring in a closed manner at 70-80°C for 60-150 minutes, and then washing with water and centrifuging and dehydrating to obtain the alkaline-treated bamboo powder; C. adding the alkali-treated bamboo powder to a chlorine dioxide solution, and then adding NaOH, controlling the mass ratio of the alkali-treated bamboo powder, chlorine dioxide, and NaOH to be 10-20:0.01-0.1:0.01-0.1, and then stirring in a closed manner at 70-80° C. for 60-120 minutes, and then washing with water and centrifuging and dehydrating to obtain a second-stage bleached bamboo powder; D. Add the second-stage bleached bamboo powder to H2O2, and then add NaOH, controlling the mass ratio of the second-stage bleached bamboo powder, H2O2 and NaOH to be 10-20:0.01-0.1:0.01-0.1, and then stir in a closed manner at 70-80°C for 60-120 minutes, and then wash with water and centrifuge to dehydrate to obtain hydrogen peroxide-bleached bamboo powder.

[0013] During bleaching, the alkali used in step B is NaOH or KOH.

[0014] The acid washing process comprises adding the bleached bamboo powder into an acid solution, and then adding a chelating agent, controlling the mass ratio of the bleached bamboo powder, the acid and the chelating agent to be 10-20:0.01-0.1:0.001-0.05, and then stirring in a closed manner at 60-80° C. for 30-90 minutes, and then washing with water and centrifugal dehydration to obtain the acid washed bamboo powder.

[0015] During pickling, the acid used is formic acid or acetic acid.

[0016] During pickling, the complexing agent used is sodium hexametaphosphate or EDTA.

[0017] Drying is done with hot air at 90-120°C.

[0018] The present invention also provides a bamboo powder raw material suitable for lyocell fiber production prepared by the above preparation method, wherein the bamboo powder raw material meets the following performance index system: Degree of polymerization: DP576~735, acetic acid content: ≥92.1%, whiteness: ≥84%, ash content: ≤0.09%, iron content: ≤6ppm, copper content: ≤0.97 ppm, calcium content: ≤88 ppm, magnesium content: ≤66 ppm, resin content: ≤0.11%, silica content: ≤193 ppm.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The present invention can significantly improve the wetting effect of the reagent on the raw material by crushing and grinding the bamboo material into bamboo powder and then processing it, thereby improving the processing efficiency and uniformity of each process.

[0020] (2) The present invention adopts two steps of alkali treatment, bleaching and pickling in combination. The highest temperature in all the steps is only 90°C, and no high pressure conditions are required. Compared with the traditional pulping and papermaking cooking process and oxygen delignification conditions, the present invention is more gentle, has lower equipment requirements, lower production energy consumption, and is safer to operate.

[0021] (3) The present invention adopts two alkali treatment processes for the first time. In each alkali treatment process, lignin and hemicellulose in bamboo powder are removed by alkali solution respectively. At the same time, the use of H2O2 is increased to provide sufficient oxygen for the alkali treatment process. Under the continuous operation of the two alkali treatment processes with different parameter conditions, the traditional pulping cooking and oxygen delignification processes are efficiently replaced. The raw material indicators finally obtained can meet the production requirements of lyocell. The operation process is also simpler, the equipment investment cost is lower, and the production cost is also lower, which has great prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the method of the present invention.

[0023] Figure 2 The bamboo powder (a) and bamboo powder raw material (b) prepared in Example 1.

[0024] Figure 3 The bamboo powder prepared in Example 1 was dissolved in an NMMO aqueous solution to form a solution with a concentration of 10 wt %.

[0025] Figure 4 This is an image of a solution formed by dissolving the bamboo powder raw material prepared in Example 1 in an NMMO aqueous solution under a microscope.

[0026] Figure 5 They are the bamboo chips (a) and bamboo pulp raw material (b) prepared in Comparative Example 1, the bamboo powder (c) and bamboo powder raw material (d) prepared in Comparative Example 2, the bamboo powder (e) and bamboo powder raw material (f) prepared in Comparative Example 3, and the bamboo powder (g) and bamboo powder raw material (h) prepared in Comparative Example 4.

[0027] Figure 6 The solution (a) formed by dissolving the bamboo pulp raw material prepared in Comparative Example 1 in the NMMO aqueous solution, the solution (b) formed by dissolving the bamboo powder raw material prepared in Comparative Example 2 in the NMMO aqueous solution, the solution (c) formed by dissolving the bamboo powder raw material prepared in Comparative Example 3 in the NMMO aqueous solution, and the solution (d) formed by dissolving the bamboo powder raw material prepared in Comparative Example 4 in the NMMO aqueous solution, all have a solution concentration of 10 wt%.

[0028] Figure 7The following are images of a solution formed by dissolving the bamboo pulp raw material prepared in Comparative Example 1 in an NMMO aqueous solution (a), an image of a solution formed by dissolving the bamboo powder raw material prepared in Comparative Example 2 in an NMMO aqueous solution (b), an image of a solution formed by dissolving the bamboo powder raw material prepared in Comparative Example 3 in an NMMO aqueous solution (c), and an image of a solution formed by dissolving the bamboo powder raw material prepared in Comparative Example 4 in an NMMO aqueous solution (d). DETAILED DESCRIPTION

[0029] The objectives, technical solutions and beneficial effects of the present invention are further described in detail below.

[0030] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the claimed invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs.

[0031] The present invention aims to solve the drawbacks of the prior art of using a cooking or oxygen delignification process to remove lignin and hemicellulose from fiber raw materials to prepare lyocell fiber raw materials. For the first time, a bamboo powder raw material is proposed, which is prepared from bamboo as raw material through crushing and grinding, two alkali treatment steps of bleaching, acid washing, and drying. The bamboo powder raw material meets the following performance indicators: degree of polymerization: DP576-735, methyl fiber content: ≥92.1%, whiteness: ≥84%, ash content: ≤0.09%, iron content: ≤6 ppm, copper content: ≤0.97 ppm, calcium content: ≤88 ppm, magnesium content: ≤66 ppm, resin content: ≤0.11%, and silica content: ≤193 ppm. Therefore, it can be used as a raw material for preparing lyocell fiber.

[0032] Specifically, the present invention relates to a process for preparing bamboo powder raw materials (see Figure 1 ) can be summarized as follows: (1) Bamboo crushing and grinding Raw bamboo (such as bamboos of the Chinese bamboo family, such as Phyllostachys chinensis and Phyllostachys pubescens) is ground and sieved to obtain a 1-40 mesh bamboo powder. This step significantly improves the impregnation effect of the reagents on the raw material, thereby increasing the efficiency and uniformity of each step.

[0033] (2) First alkali treatment The bamboo powder raw material with a certain mesh size after screening is added into a stirring device filled with an alkaline solution, and then a certain amount of H2O2 is added, and the mass ratio of bamboo powder, alkali (NaOH or KOH) and H2O2 is controlled to be 10-20:2-10:0.01-0.1, and then the mixture is stirred in a closed manner at 60-90°C for 60-150 minutes, and then washed with water and centrifuged for dehydration to obtain the alkalized bamboo powder after the first alkali treatment.

[0034] In the present invention, the purpose of the first alkali treatment is to remove most of the lignin and hemicellulose in the bamboo powder raw material. H2O2 is added during the alkali treatment of the bamboo powder raw material mainly to allow the H2O2 to decompose and provide sufficient oxygen for the alkali treatment process, because oxygen can effectively degrade lignin under alkaline conditions and dissolve the degraded lignin in the alkaline solution. At the same time, H2O2 can also play a bleaching role, thereby improving the whiteness of the bamboo powder raw material.

[0035] In this step, by properly controlling the mass ratio of bamboo powder, alkali, and H₂O₂, the removal efficiency of hemicellulose and lignin can be effectively guaranteed while avoiding excessive degradation. If the bamboo powder concentration is too high, stirring will be difficult, resulting in uneven mixing. If the bamboo powder concentration is too low, it will lead to low efficiency and increased costs. If the alkali concentration is too low, the hemicellulose and lignin removal from the bamboo powder raw material will be insufficient. If the alkali concentration is too high, the cellulose in the bamboo powder raw material will be significantly degraded, which can easily lead to excessive degradation. If the H₂O₂ concentration is too low, the oxygen supply is insufficient, resulting in an inability to effectively remove the lignin from the bamboo powder raw material. If the H₂O₂ concentration is too high, the cellulose in the bamboo powder raw material will be significantly degraded, resulting in a low degree of polymerization of the final raw material, making it unsuitable for lyocell fiber production.

[0036] This step further rationally controls the alkali treatment temperature and alkali treatment stirring time, can control the alkali treatment temperature to below 90 ℃, reduce equipment energy consumption, and the operation method is simple. In actual operation, if the temperature is too low, the alkali treatment process has a poor effect on the removal of lignin in the bamboo powder raw material, resulting in a hard raw material and a darker color. If the temperature is too high, it will cause an increase in equipment energy consumption, and manual operation has a potential safety hazard. If the alkali treatment time is too short, the hemicellulose and lignin removal in the bamboo powder raw material will not be sufficient. If the alkali treatment time is too long, the cellulose in the bamboo powder raw material will be significantly degraded, resulting in a low degree of polymerization of the final raw material, which cannot be used for lyocell fiber production. As for stirring time, it is usually determined by the concentration of alkali and H2O2. The higher the concentration of alkali and H2O2, the shorter the stirring time. Otherwise, the stirring time increases.

[0037] (3) Second alkali treatment The alkalized bamboo powder after the first alkali treatment is added back into a stirring device filled with an alkali solution, and a certain amount of H2O2 is added, and the mass ratio of the alkalized bamboo powder after the first alkali treatment, alkali (NaOH or KOH) and H2O2 is controlled to be 10-20:0.1-1:0.01-0.1, and then stirred in a closed manner at 60-80°C for 60-150min, washed with water and then centrifuged for dehydration to obtain the alkalized bamboo powder after the second alkali treatment.

[0038] In the present invention, the purpose of the second alkali treatment is to play an extraction role, dissolving the residual lignin and hemicellulose in the bamboo powder, thereby reducing the amount of various chemicals used in subsequent bleaching.

[0039] (4) Bleaching The alkalized bamboo powder after the second alkali treatment is bleached, then washed with water and centrifuged for dehydration to obtain the bleached bamboo powder raw material. The bleaching process includes the following four steps: Step 1: Chlorine dioxide bleaching The alkalized bamboo powder after the second alkali treatment is added to a chlorine dioxide solution, and then hydrochloric acid is added, and the mass ratio of the alkalized bamboo powder after the second alkali treatment, chlorine dioxide and hydrochloric acid is controlled to be 10-20:0.01-0.1:0.01-0.1, and then the mixture is stirred in a closed manner at 60-70° C. for 60-120 minutes, and then washed with water and centrifuged for dehydration to obtain a first-stage bleached bamboo powder.

[0040] Step 2: Alkaline extraction The first-stage bleached bamboo powder is added to an alkaline solution, and then H2O2 is added, and the mass ratio of the first-stage bleached bamboo powder, alkali and H2O2 is controlled to be 10-20:0.01-0.5:0.01-0.1, and then the mixture is stirred in a closed manner at 70-80°C for 60-150 minutes, and then washed with water and centrifuged for dehydration to obtain the alkali-extracted bamboo powder.

[0041] Step 3: Chlorine dioxide secondary bleaching The alkali-extracted bamboo powder is added to a chlorine dioxide solution, and then NaOH is added, and the mass ratio of the alkali-treated bamboo powder, chlorine dioxide and NaOH is controlled to be 10-20:0.01-0.1:0.01-0.1, and then the mixture is stirred in a closed manner at 70-80° C. for 60-120 minutes, and then washed with water and centrifuged for dehydration to obtain the second-stage bleached bamboo powder.

[0042] Step 4: Hydrogen peroxide bleaching The second-stage bleached bamboo powder is added to H2O2, and then NaOH is added, and the mass ratio of the second-stage bleached bamboo powder, H2O2 and NaOH is controlled to be 10-20:0.01-0.1:0.01-0.1, and then the mixture is stirred in a closed manner at 70-80°C for 60-120 minutes, and then washed with water and centrifuged for dehydration to obtain hydrogen peroxide bleached bamboo powder.

[0043] (5) Pickling The bleached bamboo powder is added to a stirring device filled with an acid solution, and then a certain amount of a complexing agent is added to control the mass ratio of the bleached bamboo powder, acid and complexing agent to be 10-20:0.01-0.1:0.001-0.05. Then, the mixture is stirred in a closed manner at 60-80°C for 30-90 minutes, and then washed with water and centrifuged for dehydration to obtain acid-washed bamboo powder.

[0044] In the present invention, weak acid is used in the pickling process to avoid significant degradation of cellulose in the bamboo powder raw material during the acidic process. The addition of the chelating agent can effectively remove metal ions, so that the final raw material meets the production requirements of lyocell fiber.

[0045] Optionally, the acid in the acid solution is formic acid or acetic acid. The addition of acid can effectively remove ash from the pulp. Using a weak acid can prevent significant degradation of the cellulose in the bamboo powder during the acidic process. If the acid concentration is too low, the ash removal effect from the pulp is poor. If the acid concentration is too high, significant degradation of the cellulose can occur.

[0046] Optionally, the complexing agent is sodium hexametaphosphate or EDTA. The addition of a complexing agent can effectively remove metal ions. The metal ion content in the pulp used in Lyocell fiber production must be kept to a minimum, as this can easily cause solvent decomposition and lead to explosions. If the complexing agent concentration is too low, the removal of metal ions from the pulp will be poor. If the concentration is too high, wastewater treatment will be difficult and increase costs.

[0047] In this step, by properly controlling the pickling temperature and stirring time during the pickling process, equipment energy consumption can be effectively controlled, while ensuring that the bamboo powder raw material meets the production requirements of lyocell fiber. If the temperature is too low, the acidification effect will be poor, while if the temperature is too high, the equipment operating energy consumption will increase significantly. If the stirring time is too short, the ash and metal ion removal in the pulp will not be sufficient to meet the requirements of lyocell fiber production. If the stirring time is too long, the equipment operating energy consumption will increase, leading to higher costs.

[0048] (6) Drying The acid-washed bamboo powder raw material is dried by hot air to obtain the bamboo powder raw material that can be used for producing lyocell fiber.

[0049] The drying temperature is 90-120°C.

[0050] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0051] Example 1: This embodiment relates to the preparation of bamboo powder raw materials: The bamboo is crushed and ground, and then sieved to obtain bamboo powder with a mesh size of 10 mesh. The powder is added to a stirring device filled with a 10 wt% NaOH solution, and then a certain amount of 0.05 wt% H2O2 solution is added to obtain a bamboo powder concentration of 10 wt%. The mixture is stirred in a closed manner at 90°C for 120 min, and then washed with water and centrifuged and dehydrated to obtain the alkalized bamboo powder after the first alkali treatment. The alkalized bamboo powder after the first alkali treatment is added to a stirring device filled with a 0.5 wt% NaOH solution, and then a certain amount of 0.05 wt% H2O2 solution is added to obtain a bamboo powder concentration of 10 wt%. The mixture is stirred in a closed manner at 80°C for 120 min, and then washed with water and centrifuged and dehydrated to obtain the alkalized bamboo powder after the second alkali treatment, which is then bleached.

[0052] The alkalized bamboo powder after the second alkali treatment is added to a stirring device filled with 0.08 wt% chlorine dioxide solution, and then a certain amount of 0.05 wt% hydrochloric acid is added. The concentration of the alkalized bamboo powder after the second alkali treatment is 10 wt%. The mixture is stirred in a closed container at 60°C for 120 min, and then washed with water and centrifuged to obtain a first-stage bleached bamboo powder; the first-stage bleached bamboo powder is continued to be added to a stirring device filled with 0.2 wt% NaOH solution, and then a certain amount of 0.05 wt% H2O2 solution is added. The concentration of the first-stage bleached bamboo powder is 10 wt%. The mixture is stirred in a closed container at 75°C for 60 min, and then washed with water and centrifuged to obtain alkali-extracted bamboo powder; the alkali-extracted bamboo powder is added to a stirring device filled with 0.06 wt% chlorine dioxide solution, and then a certain amount of 0.01 wt% NaOH solution is added. The concentration of the alkali-extracted bamboo powder is 10 wt%. The mixture is stirred in a closed container at 75°C for 120 min. min, then washed with water and centrifuged to dehydrate to obtain the second-stage bleached bamboo powder; the second-stage bleached bamboo powder was added to a stirring device filled with 0.07 wt% H2O2 solution, and then a certain amount of 0.07 wt% NaOH solution was added, the concentration of the second-stage bleached bamboo powder was 10 wt%, and the mixture was stirred in a closed manner at 75°C for 60 min, then washed with water and centrifuged to dehydrate to obtain the hydrogen peroxide bleached bamboo powder.

[0053] The bleached bamboo powder is added to a stirring apparatus containing 0.05 wt% acetic acid solution. A certain amount of 0.005 wt% sodium hexametaphosphate is then added to achieve a 10 wt% concentration of the bleached bamboo powder. The mixture is stirred in a closed container at 80°C for 60 minutes. The mixture is then washed with water and centrifuged for dehydration to obtain acid-washed bamboo powder. The acid-washed bamboo powder is then dried with hot air at 90°C to obtain the raw bamboo powder suitable for lyocell fiber production.

[0054] Example 2: The only difference between this embodiment and embodiment 1 is that different raw bamboo is used. Specifically, bamboo nanmu is used instead of bamboo tung in embodiment 1. The remaining operation steps and process parameters are the same as those in embodiment 1. Thus, bamboo powder raw material for lyocell fiber production can be prepared.

[0055] Example 3: The difference between this embodiment and embodiment 1 lies in the difference in the process of the first alkali treatment. Specifically, the concentration of the NaOH solution used in the first alkali treatment is adjusted to 5 wt %. The remaining operating steps and process parameters are the same as those in embodiment 1. In this way, a bamboo powder raw material for lyocell fiber production can be prepared.

[0056] Example 4: The difference between this embodiment and embodiment 1 is that the process of the first alkali treatment is different. Specifically, the concentration of the H2O2 solution used in the first alkali treatment process is adjusted to 0.1wt%. The remaining operating steps and process parameters are consistent with those of embodiment 1. In this way, a bamboo powder raw material for lyocell fiber production can be prepared.

[0057] Example 5: The difference between this embodiment and embodiment 1 lies in the difference in the process of the second alkali treatment. Specifically, the concentration of the NaOH solution used in the second alkali treatment is adjusted to 1 wt %. The remaining operating steps and process parameters are consistent with those of embodiment 1. In this way, a bamboo powder raw material for lyocell fiber production can be prepared.

[0058] Example 6: The difference between this embodiment and embodiment 1 lies in the difference in the process of the second alkali treatment. Specifically, the concentration of the H2O2 solution used in the second alkali treatment is adjusted to 0.1 wt%. The remaining operating steps and process parameters are consistent with those of embodiment 1. In this way, a bamboo powder raw material for lyocell fiber production can be prepared.

[0059] Comparative Example 1: The difference between this comparative example and Example 1 lies in the different processing methods of the raw bamboo. Specifically, the bamboo was cut into 3 mm × 2 mm uniform bamboo slices using a slicer, and then subjected to a first alkali treatment, a second alkali treatment, bleaching, pickling, and drying to produce the bamboo powder raw material. The operation methods and process parameters of the first alkali treatment, the second alkali treatment, bleaching, pickling, and drying steps involved were the same as those in Example 1.

[0060] Comparative Example 2: The difference between this comparative example and Example 1 is that the first and second alkali treatment processes are not adopted, but the traditional pulping and papermaking technology of sulfate cooking process and oxygen delignification process are adopted to prepare the bamboo powder raw material.

[0061] Specifically, the kraft cooking process involves adding 10 wt% bamboo flour to a cooking solution with a NaOH dosage of 17.5% (on a dry basis) and a sulfidation degree of 20% (i.e., the ratio of Na2S added to the total active alkali content). The cooking temperature is 165°C, the oxygen pressure is 0.5 MPa, and the cooking time is 120 minutes. The oxygen delignification process involves placing the 10 wt% bamboo flour in an environment at a temperature of 160°C, an oxygen pressure of 0.2 MPa, and a NaOH dosage of 5% (on a dry basis) for 120 minutes.

[0062] Comparative Example 3: The difference between this comparative example and Example 1 is that only the first alkali treatment process is used, and then the alkalized bamboo powder after the first alkali treatment is directly bleached. The remaining operating steps and process parameters are the same as those in Example 1, thereby preparing a bamboo powder raw material.

[0063] Comparative Example 4: The difference between this comparative example and Example 1 is that the concentrations of the NaOH solution and the H2O2 solution in the first and second alkali treatment processes are different, and the remaining operating steps and process parameters are the same as those in Example 1, thereby preparing a bamboo powder raw material.

[0064] Specifically, during the first alkali treatment, the concentration of the NaOH solution was adjusted to 15 wt%, and during the second alkali treatment, the concentration of the H2O2 solution was adjusted to 0.5 wt%.

[0065] The bamboo powder raw materials of Examples 1 to 6 and Comparative Examples 1 to 4 were subjected to performance tests. The test results are shown in Table 1.

[0066] The index performance testing method involved in the present invention includes: Degree of polymerization: FZ / T 50010.3-202 is used to measure the viscosity of the raw materials and then convert it into degree of polymerization. Nail fiber ( ) content: FZ / 50010.4-2011 is used to determine the content of raw materials content.

[0067] Whiteness: FZ / T 50010.7-1998 was used to determine the whiteness of the raw materials.

[0068] Ash content: FZ / T 50010.5-2023 was used to determine the ash content in raw materials.

[0069] Iron content: FZ / T 50010.6-1998 was used to determine the iron content in the raw materials.

[0070] Copper content: GB / T 8943.1-2008 was used to determine the copper content in the raw materials.

[0071] Calcium and magnesium content: The calcium and magnesium content in the raw materials was determined by digestion method (the method is from "Man-made Fibers" June 2009 edition, Volume 39, Issue 3).

[0072] Resin content: FZ / T 50010.11-1998 is used to determine the resin content in the raw materials.

[0073] Silica content: The silica content in the raw materials was determined by spectrophotometry (the method is from the October 2006 edition of Man-Made Fibers, Vol. 36, No. 5).

[0074] Table 1 Performance indicators of bamboo powder raw materials prepared in different examples and comparative examples The following conclusions can be drawn from the results in Table 1: (1) As can be seen from Examples 1 and 2, the present invention can produce bamboo powder raw materials that can be used for lyocell fiber production, regardless of whether bamboo or bamboo is used as the raw material. Of course, depending on the type of raw material, the bamboo powder raw materials finally prepared under the same process conditions are not completely consistent in terms of indicators, and there are certain differences. However, they can all meet the requirements of lyocell fiber production, which also shows that the present invention method has a certain universality in terms of raw material types.

[0075] (2) It can be seen from Examples 1, 3 to 6 that by changing the process parameters in the two alkali treatment processes, the performance indicators of the bamboo powder raw materials finally prepared can be adjusted, thereby achieving the controllability of the performance indicators of the bamboo powder raw materials. For example, by reducing the amount of alkali used in the first alkali treatment process (Example 3), the degree of polymerization of the bamboo powder raw materials finally prepared will increase. For another example, by increasing the concentration of H2O2 in the first alkali treatment process (Example 4), the degree of polymerization of the bamboo powder raw materials finally prepared will decrease, and the fiber ( ) content will also decrease, but the whiteness will slightly increase. For another example, increasing the amount of alkali used in the second alkali treatment (Example 5) will reduce the degree of polymerization of the final bamboo powder raw material. For another example, increasing the H2O2 concentration in the second alkali treatment (Example 6) will also reduce the degree of polymerization of the final bamboo powder raw material.

[0076] (3) It can be seen from Example 1 and Comparative Example 1 that when the original bamboo is cut into bamboo chips for processing, the poor permeability and wettability of the reagents to the bamboo chips lead to a significant decline in the processing effect of each process. Not only does the final raw material polymerization far exceed the polymerization index range of lyocell pulp, but also the fiber ( ) content is also very low because the raw material still contains a large amount of unremoved lignin, making it completely unsuitable for dissolution. Furthermore, the resulting raw material falls far short of standards in terms of whiteness, ash content, metal ion content, resin content, and silica content. Therefore, the present invention, which crushes and grinds the bamboo into bamboo powder for processing, significantly improves the wettability of the raw material with reagents, thereby enhancing the processing efficiency and uniformity of each step. Furthermore, only by crushing the bamboo into bamboo powder can the present method be used to prepare the bamboo into raw material suitable for lyocell fiber production.

[0077] (4) It can be seen from Example 1 and Comparative Example 2 that if the two alkali treatment processes in the method of the present invention are replaced by the sulfate cooking process and oxygen delignification process in traditional pulping and papermaking, raw materials that can be used for lyocell fiber production can also be prepared. Although there are certain differences in the indicators, both can meet the production requirements of lyocell fibers. However, the two alkali treatment processes in the method of the present invention do not require any high-pressure conditions, the process conditions are milder, and the operation is safer. This shows that the two alkali treatment processes in the method of the present invention can effectively replace the traditional pulping and oxygen delignification processes, not only achieving good hemicellulose and lignin removal effects, but also lower equipment energy consumption and simpler operation procedures.

[0078] (5) It can be seen from Example 1, Comparative Example 3 and Comparative Example 4 that if the two alkali treatment processes in the method of the present invention are adjusted, the performance indicators of the bamboo powder raw material finally prepared will change significantly. For example, when the second alkali treatment process is reduced (Comparative Example 3), the polymerization degree of the bamboo powder raw material finally prepared will increase significantly, and the fiber ( ) content will be reduced. For another example: when the concentration of NaOH solution in the first alkali treatment process is increased to 15wt%, and the concentration of H2O2 solution in the second alkali treatment process is increased to 0.5 wt% (Comparative Example 4), the degree of polymerization of the bamboo powder raw material finally obtained will be significantly reduced, and the methyl fiber ( ) content will also be significantly reduced.

[0079] In summary, the method of the present invention provides a new production process suitable for preparing bamboo powder raw materials for lyocell fiber production from bamboo as raw materials. The new production process consists of continuous steps of crushing and grinding, first alkali treatment, second alkali treatment, bleaching, pickling, and drying. It has universal applicability to bamboo as raw materials, and based on the combined operation of the first alkali treatment and the second alkali treatment steps, it can meet the performance requirements of preparing bamboo powder raw materials for lyocell fiber production from bamboo powder. At the same time, it can reduce the energy consumption of the entire production process, the operation is simpler, and it has prospects for industrial-scale production.

[0080] For further information, see Figures 2 to 4 , Figure 2The bamboo powder (a) and bamboo powder raw material (b) prepared in Example 1, Figure 3 The solution is formed by dissolving the bamboo powder raw material prepared in Example 1 in the NMMO aqueous solution. Figure 4 for Figure 3 The image of the solution under a microscope shows that the method of the present invention can prepare bamboo powder from crushed raw bamboo into a raw material for lyocell fiber production, and the prepared raw material can be well dissolved in the NMMO aqueous solution to form a spinning solution. Microscopic observation results also show that the prepared raw material has a good solubility effect, and there are no undissolved cellulose crystals or other substances in the solution.

[0081] For further information, see Figures 5 to 7 , Figure 5 The bamboo chips (a) and bamboo pulp raw materials (b) prepared in Comparative Example 1, the bamboo powder (c) and bamboo powder raw materials (d) prepared in Comparative Example 2, the bamboo powder (e) and bamboo powder raw materials (f) prepared in Comparative Example 3, and the bamboo powder (g) and bamboo powder raw materials (h) prepared in Comparative Example 4 are shown. Figure 6 The figures show a solution (a) formed by dissolving the bamboo pulp raw material prepared in Comparative Example 1 in an NMMO aqueous solution, a solution (b) formed by dissolving the bamboo powder raw material prepared in Comparative Example 2 in an NMMO aqueous solution, a solution (c) formed by dissolving the bamboo powder raw material prepared in Comparative Example 3 in an NMMO aqueous solution, and a solution (d) formed by dissolving the bamboo powder raw material prepared in Comparative Example 4 in an NMMO aqueous solution. Figure 7 The following are images of a solution formed by dissolving the bamboo pulp raw material prepared in Comparative Example 1 in an NMMO aqueous solution (a), an image of a solution formed by dissolving the bamboo powder raw material prepared in Comparative Example 2 in an NMMO aqueous solution (b), an image of a solution formed by dissolving the bamboo powder raw material prepared in Comparative Example 3 in an NMMO aqueous solution (c), and an image of a solution formed by dissolving the bamboo powder raw material prepared in Comparative Example 4 in an NMMO aqueous solution (d).

[0082] This shows that: (1) After the bamboo powder raw material was replaced with bamboo chips (Comparative Example 1), due to the poor permeability and wettability of the reagent to the bamboo chips, the raw material finally prepared still contained crude fibers that were not completely disintegrated, and the whiteness was also relatively poor. The dissolution effect in the NMMO solution was also very unsatisfactory, and obvious undissolved fiber aggregates were observed in the solution under a microscope.

[0083] (2) The two alkali treatment processes were replaced by the sulfate cooking process and the oxygen delignification process (Comparative Example 2). Although the raw materials finally prepared had certain differences in indicators, they were not much different in appearance, and the solubility in the NMMO solution was also good. No obvious undissolved cellulose crystals were observed under the microscope. This further illustrates that the two alkali treatment processes in the method of the present invention can effectively replace the traditional pulping cooking and oxygen delignification processes.

[0084] (3) If the two alkali treatment processes in the method of the present invention are adjusted, such as reducing the second alkali treatment process (Comparative Example 3), the raw material finally prepared will not only have obvious changes in indicators, but also have poor whiteness in appearance, and poor solubility in NMMO solution. Under a microscope, a small amount of undissolved cellulose crystals are observed in the solution; if the concentration of NaOH solution in the first alkali treatment process is increased to 15 wt%, and the concentration of H2O2 solution in the second alkali treatment process is increased to 0.5 wt% (Comparative Example 4), although the raw material finally obtained has no obvious difference in appearance, the solubility in NMMO solution is also better, and no undissolved cellulose crystals can be observed under a microscope, but due to the obtained raw material polymerization degree and cellulose methyl ester ( ) content is obviously too low. If it is used to produce lyocell fiber, the final fiber performance will be reduced, so it cannot meet the production needs of lyocell fiber.

[0085] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing bamboo powder raw material suitable for lyocell fiber production, characterized in that: Bamboo is used as raw material, and the bamboo powder used in the production of lyocell fiber is obtained through the process of crushing and grinding, first alkali treatment, second alkali treatment, bleaching, pickling and drying. The first alkali treatment is to add the crushed and ground bamboo powder into an alkali solution, and then add H2O2, controlling the mass ratio of bamboo powder, alkali and H2O2 to be 10-20:2-10:0.01-0.1, and then stirring in a closed manner at 60-90°C for 60-150 minutes, and then washing with water and centrifuging and dehydrating to obtain the alkalized bamboo powder after the first alkali treatment. The second alkali treatment is to add the alkalized bamboo powder after the first alkali treatment into the alkali solution, and then add H2O2, and control the mass ratio of the alkalized bamboo powder after the first alkali treatment, alkali and H2O2 to be 10-20:0.1-1:0.01-0.1, and then stir in a closed manner at 60-80°C for 60-150min, wash with water and then centrifuge to dehydrate to obtain the alkalized bamboo powder after the second alkali treatment, and then bleach.

2. The preparation method according to claim 1, wherein: The mesh size of the bamboo powder after crushing and grinding is 1 to 40 meshes.

3. The preparation method according to claim 1, wherein: In the first alkali treatment and the second alkali treatment, the alkali used is NaOH or KOH.

4. The preparation method according to claim 1, wherein: Bleaching involves the following steps: A. adding the alkalized bamboo powder after the second alkali treatment to a chlorine dioxide solution, and then adding hydrochloric acid, controlling the mass ratio of the alkalized bamboo powder after the second alkali treatment, chlorine dioxide, and hydrochloric acid to be 10-20:0.01-0.1:0.01-0.1, and then stirring in a closed manner at 60-70° C. for 60-120 minutes, and then washing with water and centrifuging and dehydrating to obtain a first-stage bleached bamboo powder; B. adding a first-stage bleached bamboo powder to an alkaline solution, and then adding H2O2, controlling the mass ratio of the first-stage bleached bamboo powder, alkali, and H2O2 to be 10-20:0.01-0.5:0.01-0.1, and then stirring in a closed manner at 70-80°C for 60-150 minutes, and then washing with water and centrifuging and dehydrating to obtain the alkaline-treated bamboo powder; C. adding the alkali-treated bamboo powder to a chlorine dioxide solution, and then adding NaOH, controlling the mass ratio of the alkali-treated bamboo powder, chlorine dioxide, and NaOH to be 10-20:0.01-0.1:0.01-0.1, and then stirring in a closed manner at 70-80° C. for 60-120 minutes, and then washing with water and centrifuging and dehydrating to obtain a second-stage bleached bamboo powder; D. Add the second-stage bleached bamboo powder to H2O2, and then add NaOH, controlling the mass ratio of the second-stage bleached bamboo powder, H2O2 and NaOH to be 10-20:0.01-0.1:0.01-0.1, and then stir in a closed manner at 70-80°C for 60-120 minutes, and then wash with water and centrifuge to dehydrate to obtain hydrogen peroxide-bleached bamboo powder.

5. The preparation method according to claim 4, characterized in that: During bleaching, the alkali used in step B is NaOH or KOH.

6. The preparation method according to claim 1, wherein: The acid washing process is to add the bleached bamboo powder into an acid solution, and then add a chelating agent, controlling the mass ratio of the bleached bamboo powder, acid and chelating agent to be 10-20:0.01-0.1:0.001-0.05, and then stirring in a closed manner at 60-80°C for 30-90 minutes, and then washing with water and centrifugal dehydration to obtain the acid-washed bamboo powder.

7. The preparation method according to claim 6, characterized in that: During pickling, the acid used is formic acid or acetic acid.

8. The preparation method according to claim 6, characterized in that: During pickling, the complexing agent used is sodium hexametaphosphate or EDTA.

9. The preparation method according to claim 1, wherein: Drying is done with hot air at 90-120°C.

10. The bamboo powder raw material suitable for lyocell fiber production prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The bamboo powder raw material meets the following performance index system: Degree of polymerization: DP576~735, acetic acid content: ≥92.1%, whiteness: ≥84%, ash content: ≤0.09%, iron content: ≤6ppm, copper content: ≤0.97 ppm, calcium content: ≤88 ppm, magnesium content: ≤66 ppm, resin content: ≤0.11%, silica content: ≤193 ppm.

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