Acetylated fiber and preparation method thereof

Abstract

The invention belongs to the technical field of cellulose modification and surface esterification, and discloses acetylated fiber and a preparation method thereof. The preparation method comprises the following steps: loading a catalyst spray on the surface of a cellulose raw material, drying, and atomizing and spraying vinyl acetate on the dried cellulose material for reaction; wherein each gram of the dried cellulose material is loaded with 0.5 to 50 milligrams of a catalyst. According to the present invention, the side reaction can be inhibited, and the significantly higher acetylation degree, the higher esterification agent effective utilization rate and the less by-product generation can be obtained under the same reaction material ratio or the lower reaction material ratio, which are difficult to simultaneously achieve in the existing aqueous phase esterification or gas phase contact method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cellulose modification and surface esterification, and particularly relates to acetylated fibers and a preparation method thereof. BACKGROUND

[0002] The hydroxyl groups on the surface of cellulose molecules result in strong hydrophilicity, poor compatibility with hydrophobic materials, and insufficient chemical stability, which seriously limits its application in high-end functional materials. In order to improve the performance, the scientific community widely uses chemical modification methods such as esterification and etherification, among which the surface esterification method is concerned because it can introduce hydrophobic groups while maintaining the integrity of the cellulose backbone.

[0003] Traditional cellulose esterification methods mainly include solution method, gas phase method and solid phase method. The solution method usually uses acid anhydride, acyl chloride and other esterification agents, assisted by acid or base catalysts, to react in organic solvents. Although the esterification degree is high, there are problems such as solvent toxicity, flammability, environmental burden, etc. The gas phase method has high requirements for equipment and strict process conditions. In recent years, researchers have tried to develop aqueous phase esterification method, which uses alkali catalyst and vinyl ester such as vinyl acetate in aqueous solution to modify the surface of cellulose, aiming to avoid the problems of traditional organic solvent system.

[0004] However, in the aqueous phase esterification method, vinyl acetate can produce a side reaction, i.e. saponification reaction. This side reaction directly consumes the vinyl acetate used for acetylated cellulose, converting it into acetic acid and acetaldehyde, instead of the expected acetyl group grafted onto cellulose, which reduces the effective utilization rate of vinyl acetate. SUMMARY

[0005] The present application aims to solve at least one of the above technical problems, and provides acetylated fibers and a preparation method thereof.

[0006] To achieve the above purpose, the technical solution adopted by the present application is as follows: The preparation method of acetylated fibers comprises the following steps: spraying a catalyst on the surface of cellulose raw materials, drying, and then spraying vinyl acetate on the dried cellulose materials for reaction; wherein, 0.5-50 milligrams of catalyst are loaded on each gram of dried cellulose materials.

[0007] Preferably, the drying temperature is 60-80℃, and the residual moisture content of the dried cellulose materials is not more than 0.5%.

[0008] Preferably, the reaction temperature is 20-30℃.

[0009] Preferably, the cellulose raw materials include any one of paper pulp fibers, wood fibers, regenerated cellulose fibers, and cotton fibers.

[0010] Preferably, the mass ratio of cellulose raw materials to vinyl acetate is 1:2.

[0011] Preferably, the catalyst is an inorganic base and / or an alkaline inorganic salt.

[0012] Preferably, the catalyst comprises any one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and sodium carbonate.

[0013] Preferably, the catalyst is loaded on the surface of the cellulose raw material by electrostatic spraying, and during the electrostatic spraying, the voltage applied is 15-30 kV, the liquid flow rate is 0.05-10 ml / min, and the distance between the nozzle and the cellulose raw material is 10-15 cm.

[0014] Preferably, the process further comprises collecting the vinyl acetate that has not contacted the cellulose material during the atomized spraying of the vinyl acetate, and recycling the purified vinyl acetate for use in the atomized spraying.

[0015] Preferably, during the atomized spraying, the pressure of the atomized gas is 0.05-0.4 MPa, and the liquid flow rate of the vinyl acetate is 1-30 g / min.

[0016] The application also discloses an acetylated fiber prepared by any of the above preparation methods.

[0017] Compared with the prior art, the application has the following beneficial effects: After the catalyst is loaded on the surface of the cellulose raw material by spraying or atomization, the water content in the cellulose is controlled by drying, and the vinyl acetate is loaded on the dried cellulose raw material by atomized spraying, so that the occurrence of side reactions can be inhibited, and under the same or lower reactant ratio, the application can obtain significantly higher acetylation degree, higher effective utilization rate of the esterifying agent, and less by-products, which is difficult to achieve simultaneously in the prior art water phase esterification or gas phase contact method. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the application, the following will briefly introduce the drawings needed to be used in the examples. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be considered as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings: Figure 1 is the infrared spectrum of the fiber after acetylation reaction in Example 1 of the application; Figure 2 is the infrared spectrum of the fiber after acetylation reaction in Comparative Example 1 of the application; Figure 3 is the infrared spectrum of the fiber after acetylation reaction in Comparative Example 2 of the application; Figure 4 In (a), (b) are SEM-EDS characterization diagrams of the fibers after acetylation reaction of the present application comparative example 2; Figure 5 In (a), (b) are SEM-EDS characterization diagrams of the fibers after acetylation reaction of the present application comparative example 2; Figure 6 In (a), (b) are SEM-EDS characterization diagrams of the fibers after acetylation reaction of the present application comparative example 2. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0020] In the prior art, the organic solvent method and the aqueous phase esterification method are commonly used for cellulose acetylation. The organic solvent method relies on anhydrous environment, which can solve the problem of side reactions, but brings more serious organic solvent pollution. The aqueous phase esterification method is a method improved to solve the defects of the organic solvent, namely the liquid phase immersion method, which uses a water solution containing a catalyst to first immerse the fiber raw material, and then reacts with an esterifying agent. However, the presence of water and OH - in the catalyst can jointly cause the hydrolysis of the esterifying agent, which is a side reaction. To solve this problem, the prior art indirectly controls the total amount of OH - in the reaction system by adjusting the alkali concentration. This method only finds an acceptable balance point between the main reaction (acetylation) and the side reaction (hydrolysis), and cannot fundamentally solve the problem of side reactions.

[0021] For the side reaction that occurs in the liquid phase immersion method, namely the saponification reaction, the main reaction includes the ester exchange reaction of the cellulose surface hydroxyl group and vinyl acetate (acetylation reaction), to generate cellulose acetate (acetyl cellulose) and ethylene alcohol, and the ethylene alcohol is unstable and will isomerize into acetaldehyde. The equation of the main reaction is: Ester exchange reaction: Cell-OH + CH3COOCH=CH2→ Cell-OCOCH3 + CH2=CHOH; in the formula, Cell-OH is the cellulose hydroxyl group, and CH2=CHOH is ethylene alcohol; The equation of the side reaction includes the saponification reaction of vinyl acetate (under the action of NaOH): CH3COOCH=CH2+ H2O→ CH3COOH + CH2=CHOH; The reaction equation of vinyl alcohol isomerization is: CH2=CHOH→CH3CHO; wherein, CH3CHO is acetaldehyde.

[0022] The reaction equation of vinyl alcohol isomerization is: CH2=CHOH→CH3CHO; wherein, CH3CHO is acetaldehyde.

[0023] The main reaction is that the cellulose hydroxyl reacts with vinyl acetate to form acetylated cellulose; the main side reaction is that the vinyl acetate is hydrolyzed in the presence of NaOH and water to generate acetic acid (further forming sodium acetate) and acetaldehyde, which will consume the vinyl acetate and NaOH, and reduce the efficiency of the main reaction.

[0024] Therefore, by inhibiting the side reaction, the acetylation degree can be significantly improved.

[0025] The present application provides a method for preparing acetylated cellulose, wherein a catalyst is sprayed and loaded on the surface of a cellulose raw material, and after drying, vinyl acetate is atomized and sprayed on the dried cellulose material to perform a reaction; wherein, 0.5-50 mg of catalyst is loaded on each gram of the dried cellulose material.

[0026] The principle of the "spraying" is to use a high-voltage electric field to charge the liquid droplets, and the charged liquid droplets will repel each other and be attracted to the grounded cellulose raw material under the action of electric field force, thereby achieving self-dispersing uniform coverage and firm adhesion.

[0027] The "atomization" is that the liquid will repel each other and be attracted to the grounded cellulose material under the action of force, thereby achieving self-dispersing uniform coverage and firm adhesion; generally, the kinetic energy of high-pressure gas (such as nitrogen) is used to mechanically tear and break the liquid into extremely fine droplets to form an aerosol (mist).

[0028] In cellulose chemistry, those skilled in the art believe that water can swell the cellulose fibers, destroy their tight hydrogen bond network, and thus expose the internal hydroxyl reaction sites, making them more susceptible to chemical reactions. Therefore, retaining a certain amount of water in the reaction system is beneficial to the main reaction. The present application breaks the technical prejudice of needing to retain water in the fiber, i.e., directly performing esterification reaction after impregnation by soaking, dries the cellulose raw material after loading the catalyst, controls the water content to be not more than 0.5%, and then sprays the esterifying agent on the surface of the dried cellulose material by atomization to perform esterification reaction. This not only makes the esterifying agent uniformly loaded on the fiber surface, but also fundamentally changes the reaction environment, so that the esterification reaction is converted from a low-efficiency, serious side-reaction liquid-solid-liquid heterogeneous reaction to a high-efficiency, high-selectivity quasi-gas-solid reaction. It is found through experiments that this spraying method unexpectedly further inhibits the occurrence of side reactions.

[0029] It should be noted that the present application does not have special limitations on the concentration of the catalyst, and only the loading amount of the catalyst needs to be controlled.

[0030] In the present application, when vinyl acetate is sprayed by atomization, the atomization is a mechanical process, in which the liquid vinyl acetate is dispersed into extremely fine liquid droplets suspended in air by external force such as high-pressure air flow. This process does not require heating and can be carried out at 20-30℃, i.e., the esterification reaction temperature is 20-30℃. This mild reaction condition not only maximizes the physical integrity of the fiber, but also avoids unnecessary self-polymerization of vinyl acetate at high temperatures, thereby improving the acetylation degree. After spraying vinyl acetate, the acetylation reaction is completed within 2 minutes, and after washing and drying the cellulose material, acetylated fiber is obtained. In actual industrial applications, in order to ensure that the cellulose material is uniformly sprayed with vinyl acetate and the reaction is sufficient, the spraying and reaction time can be extended, for example, to 5-30 minutes. At the same time, the amount of vinyl acetate used can also be adjusted according to actual needs. Generally, atomization spraying can greatly reduce the amount of vinyl acetate used, but in order to ensure sufficient reaction, it can also be appropriately increased. For example, the mass ratio of cellulose raw material to ethyl acetate can be controlled to be 1:2.

[0031] In some preferred embodiments, in order to minimize raw material waste, it is also possible to collect the vinyl acetate that does not contact the cellulose material during the atomization spraying process, purify it, and recycle it for use in the atomization spraying process. The drying method is not particularly limited and common drying methods such as heat drying, physical and mechanical dewatering, normal temperature drying, adsorption drying, etc. can be used, such as drying, hot air circulation drying, wringing, centrifugal dewatering, airing, air drying, and shade drying. In some preferred embodiments, the temperature for drying and hot air circulation drying is 60-80℃.

[0032] It should be noted that the present application does not limit the cellulose raw material, and common cellulose such as any one of paper pulp fiber, wood fiber, regenerated cellulose fiber, cotton fiber, etc. can be used in the present application.

[0033] The catalyst used in the present application is a commonly used catalyst in acetylation reactions and is not particularly limited, and those skilled in the art can select it according to actual needs. Common catalysts are inorganic bases and / or basic inorganic salts, such as any one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, etc.

[0034] In some preferred embodiments, the catalyst is loaded on the surface of the cellulose raw material by the method of electrostatic spraying, and in the electrostatic spraying process, the applied voltage is 15-30 kV, the liquid flow rate is 0.05-10 ml / min, the distance between the nozzle and the cellulose raw material is 10-15 cm, and the size of the mist droplets of the catalyst solution is 10-15 μm. By further adjusting the parameters of electrostatic spraying, the esterification efficiency can be further improved.

[0035] In some preferred embodiments, when atomized spraying, the pressure of the atomizing gas is 0.05-0.4 MPa, the liquid flow rate of the vinyl acetate is 1-30 g / min, and the size of the vinyl acetate mist droplets is 1-5 μm. By further adjusting the parameters of atomized spraying, the esterification efficiency can be further improved.

[0036] The preparation and performance of acetylated fibers are described in detail below through a plurality of specific examples and comparative examples.

[0037] The method for calculating the overall acetylation degree in the following examples and comparative examples is as follows: the near-infrared spectrometer (ATR diamond) experiment is performed on each sample to obtain an infrared spectrum. Through the obtained infrared spectrum, after baseline correction, the acetylation degree Ac% of the esterification product on the surface of the cellulose is calculated by dividing the absorbance ratio at 1731 cm -1 and 1061 cm -1 by the coefficient 0.0282. The 1731 cm -1 in the infrared spectrum is the corresponding acyl group, Wavenumber represents wave number, and Transmittance represents transmission coefficient. Under the same raw material amount, the higher the acetylation degree of the product, the lower the side reaction.

[0038] Example 1 Method for preparing acetylated fibers: 7.5 g of cotton fiber non-woven fabric cut into 15 cm x 15 cm pieces was taken; A NaOH aqueous solution with a mass concentration of 3% was prepared, and the NaOH solution was loaded on both sides of the non-woven fabric by using an electrostatic spraying device. In the electrostatic spraying process, the applied voltage was 30 kV; the liquid flow rate was 8.0 mL / min; the distance between the nozzle and the surface of the non-woven fabric was 15 cm to ensure that the entire surface was uniformly wetted; and the loading amount of NaOH on each gram of dried non-woven fabric was controlled to be 11.2 mg; The non-woven fabric loaded with NaOH was dried at 80°C for 1 h to obtain a non-woven fabric material with a water content of 0.5%; The dried non-woven fabric material is placed in an air atomization device for esterification, the gas-liquid ratio is 0.5:1; the liquid flow rate of vinyl acetate is 15 g / min, the total amount is 15 g, the vinyl acetate droplet size is 1 μm, the temperature of the atomization process is 20℃, after the reaction is completed, the atomization is stopped, the material is washed and dried, and the acetylated non-woven fabric is obtained.

[0039] The overall acetylation degree Ac% of this embodiment is calculated to be 15.20; the SEM-EDS characterization graph shows that the acetylated non-woven fabric obtained in this embodiment is not broken.

[0040] Example 2 The specific operation is as in Example 1, the difference is only that in the electrostatic spraying process, the loading amount of NaOH on each gram of dried non-woven fabric is controlled to be 8 mg, the applied voltage is 15 kv, the liquid flow rate is 10 ml / min, the distance between the nozzle and the cellulose material is 10 cm, and the NaOH droplet size is 15 μm; The liquid flow rate of vinyl acetate in the air atomization process is 20 g / min, the total amount is 15 g, the gas-liquid ratio is 2:1, the vinyl acetate droplet size is 5 μm, and the acetylated non-woven fabric sample is obtained.

[0041] The overall acetylation degree Ac% of this embodiment is calculated to be 11.34; the SEM-EDS characterization graph shows that the acetylated non-woven fabric obtained in this embodiment is not broken.

[0042] Example 3 The specific operation is as in Example 1, the difference is only that in the electrostatic spraying process, the loading amount of NaOH on each gram of dried non-woven fabric is controlled to be 0.5 mg.

[0043] The overall acetylation degree Ac% of this embodiment is calculated to be 1.32%; the SEM-EDS characterization graph shows that the acetylated non-woven fabric obtained in this embodiment is not broken.

[0044] Example 4 The specific operation is as in Example 1, the difference is only that in the electrostatic spraying process, the loading amount of NaOH on each gram of dried non-woven fabric is controlled to be 30 mg.

[0045] The overall acetylation degree Ac% of this embodiment is calculated to be 19.3%; the SEM-EDS characterization graph shows that the acetylated non-woven fabric obtained in this embodiment is not broken.

[0046] Example 4 The specific operation is as in Example 1, the difference is only that in the electrostatic spraying process, the loading amount of NaOH on each gram of dried non-woven fabric is controlled to be 50 mg.

[0047] The overall acetylation degree Ac% of the embodiment was calculated to be 25.6%; and the acetylated non-woven fabric obtained in the embodiment was found to have no breakage through SEM-EDS characterization diagram.

[0048] Comparative Example 1 In a 500 ml beaker, 200 ml of a 3% mass concentration sodium hydroxide solution was added, and 10 g of non-woven fabric was placed in the sodium hydroxide solution, reacted for 10 min, and after the reaction was completed, it was left to stand and washed with deionized water and ethanol, and after drying, the non-woven fabric material was obtained, and the overall acetylation degree Ac% was calculated to be 0.00.

[0049] Comparative Example 2 In a 500 ml beaker, 200 ml of a 3% mass concentration sodium hydroxide solution was added, and 7.5 g of non-woven fabric was added to the sodium hydroxide solution for immersion, and then 15 g of vinyl acetate was added, and stirring was carried out at room temperature, and the reaction was carried out for 10 min, and the reacted non-woven fabric material was obtained, and after washing with deionized water and hot ethanol and drying, the acetylated non-woven fabric was obtained, and the overall acetylation degree Ac% was calculated to be 0.80. The acetylated non-woven fabric obtained in the comparative example was found to have breakage through SEM-EDS characterization diagram.

[0050] Comparative Example 3 The specific operation steps were the same as in Example 1, and the specific difference was that the vinyl acetate was added in a dropwise manner, and the specific steps were as follows: 15 g of vinyl acetate was added dropwise to the non-woven fabric material loaded with NaOH, and after the reaction was completed, it was left to stand and washed with deionized water and ethanol, and after drying, the acetylated non-woven fabric material was obtained, and the overall acetylation degree Ac% was calculated to be 2.68. The acetylated non-woven fabric obtained in the comparative example was found to have no breakage through SEM-EDS characterization diagram.

[0051] Comparative Example 4 Compared with Example 1, the only difference was that the method of spraying NaOH solution on the non-woven fabric was replaced by directly immersing the non-woven fabric in the NaOH solution, and the remaining parameters and steps were the same as in Example 1.

[0052] The acetylation degree Ac% of the comparative example was calculated to be 2.30. The acetylated non-woven fabric obtained in the comparative example was found to have no breakage through SEM-EDS characterization diagram.

[0053] Comparative Example 5 Compared with Example 1, the only difference was that the drying treatment of the non-woven fabric loaded with NaOH was cancelled, and the remaining parameters and steps were the same as in Example 1.

[0054] The overall acetylation degree Ac% of the comparative example was calculated to be 2.10. The acetylated non-woven fabric obtained in the comparative example was found to have breakage through SEM-EDS characterization diagram.

[0055] Analysis of the acetylated fibers prepared in various embodiments and comparative examples reveals that if vinyl acetate is sprayed directly without drying after being loaded with NaOH, the undried moisture is still sufficient to trigger significant vinyl acetate hydrolysis side reactions. Because the NaOH catalyst remains in the aqueous environment, uneven spraying, large droplets, or insufficient drying can lead to the formation of high-concentration alkaline solutions in localized areas, potentially causing some degradation of the cellulose. While spraying NaOH alone is superior to impregnation in controlling the initial alkali and water content, the side reactions of vinyl acetate cannot be fundamentally avoided as long as significant moisture remains on the fiber surface during subsequent esterification. The issues of byproduct particles and catalyst consumption persist. Although fiber damage may be mitigated, the risk of degradation cannot be completely eliminated as long as liquid alkaline solutions remain in prolonged contact with the fibers.

[0056] If the cellulose raw material is loaded with NaOH through soaking before drying and atomizing with esterifying agents, the side reaction problem cannot be solved. When water containing a large amount of dissolved NaOH evaporates from the fiber, the NaOH may migrate and recrystallize. This may result in a more uneven distribution of NaOH on the fiber surface after drying, forming high-concentration local alkaline spots or large NaOH crystal particles. During the drying process, the NaOH concentration on the fiber surface will increase sharply as the moisture decreases. Prolonged exposure to this high-concentration alkaline environment at high temperatures (even 80°C) may also accelerate the degradation of cellulose, causing the fiber to become brittle, lose strength, and even be damaged during the drying process, with byproducts still remaining on the fiber.

[0057] If NaOH is loaded onto the cellulose raw material through soaking without drying, and then the esterifying agent is atomized and sprayed onto the impregnated nonwoven fabric, the problem of side reactions cannot be solved. The fiber substrate itself is a fiber that has not been effectively dried and has been loaded with a large amount of water and alkali through the traditional impregnation method. This cannot fundamentally solve the problem of the side reaction of vinyl acetate hydrolysis caused by water, nor can it avoid the resulting byproduct particles and potential fiber damage.

[0058] Figure 1 The infrared spectrum of the acetylated fibers prepared in Example 1 is shown below. Figure 1 It can be seen that by using "precise spray loading" + "intermediate key drying" + "atomized esterification" to solve a number of technical problems existing in the prior art, a nonwoven material with a significantly improved degree of acetylation was obtained. Figure 2 The infrared spectrum of the fiber prepared in Comparative Example 1 is shown. Since it has not undergone esterification, there is no acetyl absorption peak in the infrared spectrum, only at 1640 cm⁻¹. -1 There is a peak at that point. Figure 3The infrared spectrum of the fiber prepared in Comparative Example 2, prepared by liquid phase immersion, has a peak at 1731 cm -1 which is much different from that obtained in Example 1, which also reflects the unexpected technical effects and advantages of the "spray precise loading" + "intermediate key drying" + "atomized esterification" process.

[0059] From the SEM images of Figures 4-6 , it can be seen that the microstructure of the non-woven fabric sample obtained by liquid phase immersion has many fiber fractures, and there are also many particles formed by saponification reaction (sodium acetate). The source of the particles is acetic acid generated by the side reaction. After neutralizing part of the NaOH, there is still Na+ in the system, which will form sodium acetate. The solubility of sodium acetate in water is limited. When the water evaporates or the concentration reaches saturation, it will precipitate in the form of solid particles and adhere to the surface of the fiber. And the acetaldehyde formed in the side reaction will undergo polymerization under alkaline conditions for a long time to form oligomer substances, which will also appear in the form of insoluble particles after drying. Then through "spray precise loading" + "intermediate key drying" + "atomized esterification", the side reaction is inhibited, and in the SEM images in Figure 5 , it can be seen that the surface of the fiber is smooth and has no cracks and fractures, and from Figure 4 and Figure 6 , it can be seen that the fibers obtained by the method of liquid phase immersion have particles loaded on the surface of the fibers, and there are also fractured parts, which will affect the esterification efficiency.

[0060] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. Process for the preparation of acetylated cellulose, characterized in that, The catalyst is sprayed on the surface of the cellulose raw material, and after drying, the ethylene acetate is atomized and sprayed on the dried cellulose material for reaction; wherein 0.5-50 mg of catalyst is loaded on each gram of dried cellulose material.

2. The method for preparing acetylated fibers according to claim 1, characterized by, The drying temperature is 60-80℃, and the residual moisture content of the dried cellulose material is not more than 0.5%.

3. The method for preparing acetylated fibers as described in claim 1, characterized in that, The reaction temperature is 20-30℃.

4. The method of preparing acetylated cellulose according to claim 1, wherein The cellulose raw material includes any one of paper pulp fiber, wood fiber, regenerated cellulose fiber, and cotton fiber.

5. The method of preparing acetylated cellulose according to claim 1, wherein, The mass ratio of the cellulose raw material to ethylene acetate is 1:

2. ​ 6. The method of preparing acetylated cellulose according to claim 1, wherein, The catalyst is an inorganic base and / or an alkaline inorganic salt.

7. The method of preparing acetylated cellulose according to claim 6, wherein The catalyst includes any one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and sodium carbonate.

8. The method for preparing acetylated fibers as described in claim 1, characterized in that, It also includes collecting ethylene acetate that does not contact the cellulose material during the atomized spraying process, purifying the ethylene acetate, and recycling it for the atomized spraying process.

9. The method for preparing acetylated fibers as described in claim 1, characterized in that, During the atomized spraying, the atomized gas pressure is 0.05-0.4 MPa, and the ethylene acetate liquid flow rate is 1-30 g / min.

10. An acetylated fiber obtained by the preparation method of any one of claims 1-9.

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