Acetylated fibers and methods for making same

Abstract

The present application belongs to the technical field of cellulose modification and surface esterification, and discloses acetylated cellulose and a preparation method thereof. The preparation method is as follows: a catalyst is sprayed and loaded on the surface of cellulose raw materials, and after drying, ethylene acetate is atomized and sprayed on the dried cellulose materials for reaction; wherein, 0.5-50 milligrams of catalyst are loaded on each gram of the dried cellulose materials. The present application can inhibit the occurrence of side reactions, and under the same reactant material ratio or a lower reactant material ratio, the present application can obtain significantly higher acetylation degree, higher effective utilization rate of esterification agent and less by-product generation, which is difficult to achieve simultaneously in the existing water 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 the application of cellulose 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 esterifying 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 a water phase esterification method, which uses alkali catalysts and vinyl ester esterifying agents such as vinyl acetate in aqueous solution to modify the surface of cellulose, aiming to avoid the problems of traditional organic solvent systems.

[0004] However, in the water 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-mentioned purpose, the technical solution adopted by the present application is as follows:

[0007] 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.

[0008] Preferably, the drying temperature is 60-80℃, and the residual moisture content of the dried cellulose materials is not more than 0.5%.

[0009] Preferably, the reaction temperature is 20-30℃.

[0010] Preferably, the cellulose raw materials include any one of paper pulp fibers, wood fibers, regenerated cellulose fibers, and cotton fibers.

[0011] Preferably, the mass ratio of the cellulose raw material to vinyl acetate is 1:2.

[0012] Preferably, the catalyst is an inorganic base and / or an alkaline inorganic salt.

[0013] Preferably, the catalyst comprises any one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and sodium carbonate.

[0014] 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.

[0015] Preferably, the process further comprises collecting the vinyl acetate that has not contacted the cellulose material during the atomized spraying of the vinyl acetate, purifying the vinyl acetate, and recycling the purified vinyl acetate for use in the atomized spraying.

[0016] 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.

[0017] The application also discloses an acetylated fiber prepared by any one of the above preparation methods.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] 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 then 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 material ratio, the application can obtain significantly higher acetylation degree, higher effective utilization rate of the esterification 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

[0020] 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 embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be considered as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0021] Figure 1 is the infrared spectrum of the fiber after the acetylation reaction of Example 1 of the application;

[0022] Figure 2The infrared spectrum of the fiber after acetylation reaction of the present application comparative example 1;

[0023] Figure 3 The infrared spectrum of the fiber after acetylation reaction of the present application comparative example 2;

[0024] Figure 4 The SEM-EDS characterization diagram of the fiber after acetylation reaction of the present application comparative example 2 (a) and (b);

[0025] Figure 5 The SEM-EDS characterization diagram of the fiber after acetylation reaction of the present application example 1 (a) and (b);

[0026] Figure 6 The SEM-EDS characterization diagram of the fiber after acetylation reaction of the present application comparative example 2. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with 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 labor fall within the protection scope of the present application.

[0028] In the prior art, the organic solvent method and the aqueous phase esterification method are commonly used for cellulose acetylation. The organic solvent method depends on anhydrous environment, can solve the problem of side reaction, 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 existence 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 the side reaction.

[0029] For the side reaction of the liquid phase immersion method, namely the saponification reaction, the main reaction includes the ester exchange reaction (acetylation reaction) of the cellulose surface hydroxyl group and vinyl acetate, to generate cellulose acetate (acetylated cellulose) and ethylene alcohol, and the ethylene alcohol is unstable and can isomerize into acetaldehyde; the equation of the main reaction is as follows:

[0030] Ester exchange reaction: Cell-OH + CH3COOCH=CH2→ Cell-OCOCH3 + CH2=CHOH; wherein Cell-OH is a cellulose hydroxyl group and CH2=CHOH is vinyl alcohol;

[0031] Equations of side reactions include saponification of vinyl acetate (under the action of NaOH): CH3COOCH=CH2+ H2O→ CH3COOH + CH2=CHOH;

[0032] Equation of vinyl alcohol isomerization: CH2=CHOH→ CH3CHO; wherein CH3CHO is acetaldehyde.

[0033] CH3COOH + NaOH→ CH3COONa + H2O; wherein CH3COONa is sodium acetate.

[0034] The main reaction is the reaction of cellulose hydroxyl groups with vinyl acetate to form acetylated cellulose; the main side reaction is the hydrolysis of vinyl acetate in the presence of NaOH and water to form acetic acid (and further sodium acetate) and acetaldehyde, which consumes vinyl acetate and NaOH and reduces the efficiency of the main reaction.

[0035] Therefore, by inhibiting side reactions, the degree of acetylation can be significantly improved.

[0036] The present application provides a method for preparing acetylated cellulose, wherein a catalyst is sprayed onto the surface of a cellulose raw material, dried, and then vinyl acetate is atomized and sprayed onto the dried cellulose material to perform a reaction; wherein 0.5-50 mg of catalyst is loaded per gram of dried cellulose material.

[0037] The principle of "spraying" is to use a high-voltage electric field to charge droplets, and the charged droplets are repelled and attracted to the grounded cellulose raw material under the action of electric field force, thereby achieving uniform coverage and firm adhesion in a self-dispersing manner.

[0038] The "atomization" is that the liquid is repelled and attracted to the grounded cellulose material under the action of force, thereby achieving uniform coverage and firm adhesion in a self-dispersing manner; 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).

[0039] In cellulose chemistry, it is believed by those skilled in the art that water can swell cellulose fibers, destroy their tight hydrogen bond network, thus exposing the internal hydroxyl reaction sites, making them more susceptible to chemical reactions. Therefore, it is beneficial to retain a certain amount of water in the reaction system for the main reaction to proceed. The present application breaks the technical prejudice of needing to retain water in the fiber, i.e. directly performing esterification after impregnation by soaking, and 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 fiber material by atomization to perform esterification. Not only can the esterifying agent be uniformly loaded on the fiber surface, but also the reaction environment is fundamentally changed, making the esterification reaction change 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 the spraying method unexpectedly further inhibits the occurrence of side reactions.

[0040] It should be noted that the present application does not have special limitations on the concentration of the catalyst, and only needs to control the loading amount of the catalyst.

[0041] When using atomization to spray vinyl acetate, the atomization is a mechanical process, in which the vinyl acetate liquid is dispersed into extremely fine droplets suspended in the air by external force such as high-pressure air flow. This process does not require heating and can be performed 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 time is relatively short, and the reaction can be completed within 2 minutes. After the reaction is completed, the cellulose material is washed and dried to obtain acetylated fibers. In actual industrial applications, in order to ensure that the cellulose material can be 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.

[0042] In some preferred embodiments, in order to minimize the waste of raw materials, 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, shade drying, etc. In some preferred embodiments, the temperature for drying and hot air circulation drying is 60-80℃.

[0043] It should be noted that the present invention does not limit the cellulose raw materials, and common cellulose can be used in the present invention, such as pulp fiber, wood fiber, regenerated cellulose fiber, cotton fiber, etc.

[0044] The catalyst used in this invention is a commonly used catalyst in acetylation reactions and is not particularly limited thereto; those skilled in the art can select one according to actual needs. Commonly used catalysts are inorganic bases and / or basic inorganic salts, such as one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and sodium carbonate.

[0045] In some preferred embodiments, an electrostatic spraying method is used to load the catalyst onto the surface of the cellulose raw material. During the electrostatic spraying process, the applied voltage is 15kV~30kV, the liquid flow rate is 0.05ml / min~10ml / min, the distance between the nozzle and the cellulose raw material is 10cm~15cm, and the droplet size of the catalyst solution is 10μm~15μm. Further adjustments to the electrostatic spraying parameters can further improve the esterification efficiency.

[0046] In some preferred embodiments, during atomization spraying, the atomizing gas pressure is 0.05 MPa to 0.4 MPa, the vinyl acetate liquid flow rate is 1 g / min to 30 g / min, and the vinyl acetate droplet size is 1 μm to 5 μm. Further adjustments to the atomization spraying parameters can further improve the esterification efficiency.

[0047] The preparation and properties of acetylated fibers are described in detail below through several specific examples and comparative examples.

[0048] The method for calculating the overall degree of acetylation in the following examples and comparative examples is as follows: Mid-to-near infrared spectroscopy (ATR diamond) was performed on each sample to obtain infrared spectra. After baseline correction, the obtained infrared spectra were analyzed using a 1731 cm⁻¹ spectrometer. -1 and 1061cm -1 The degree of acetylation (Ac%) of the esterification products on the cellulose surface was calculated by dividing the absorbance ratio at 1731 cm⁻¹ by a coefficient of 0.0282. -1 The symbol represents the corresponding acyl group, wavenumber represents the wave number, and transmissiontance represents the transmission coefficient. With the same amount of raw materials, a higher degree of acetylation in the product indicates lower side reactions.

[0049] Example 1

[0050] Preparation method of acetylated cellulose:

[0051] Take 7.5g of cotton fiber nonwoven fabric that has been cut into 15cm×15cm sheets;

[0052] Aqueous solution of NaOH with a mass concentration of 3% was configured, and the NaOH solution was loaded on both sides of the non-woven fabric by using an electrostatic spraying device. During the electrostatic spraying process, the voltage applied 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, ensuring 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.

[0053] 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%.

[0054] The dried non-woven fabric material was placed in an air atomization device for esterification. The gas-liquid ratio was 0.5:1; the liquid flow rate of vinyl acetate was 15 g / min, and the total amount of vinyl acetate was 15 g; the droplet size of vinyl acetate was 1 μm; the temperature of the atomization process was 20°C; after the reaction was completed, the atomization was stopped, and the material was washed and dried to obtain an acetylated non-woven fabric.

[0055] It was calculated that the overall acetylation degree Ac% of this embodiment was 15.20; and it was found through the SEM-EDS characterization diagram that the acetylated non-woven fabric obtained in this embodiment was not broken.

[0056] Example 2

[0057] The specific operation was as in Example 1, except that during the electrostatic spraying process, the loading amount of NaOH on each gram of dried non-woven fabric was controlled to be 8 mg, the voltage applied was 15 kV, the liquid flow rate was 10 ml / min, the distance between the nozzle and the cellulose material was 10 cm, and the droplet size of NaOH was 15 μm.

[0058] The liquid flow rate of vinyl acetate in the air atomization process was 20 g / min, the total amount of vinyl acetate was 15 g, the gas-liquid ratio was 2:1, the droplet size of vinyl acetate was 5 μm, and an acetylated non-woven fabric sample was obtained.

[0059] It was calculated that the overall acetylation degree Ac% of this embodiment was 11.34; and it was found through the SEM-EDS characterization diagram that the acetylated non-woven fabric obtained in this embodiment was not broken.

[0060] Example 3

[0061] The specific operation was as in Example 1, except that during the electrostatic spraying process, the loading amount of NaOH on each gram of dried non-woven fabric was controlled to be 0.5 mg.

[0062] It was calculated that the overall acetylation degree Ac% of this embodiment was 1.32%; and it was found through the SEM-EDS characterization diagram that the acetylated non-woven fabric obtained in this embodiment was not broken.

[0063] Example 4

[0064] The specific operation is as in Example 1, with the only difference being that the loading of NaOH on the non-woven fabric after drying is controlled to be 30 mg per gram.

[0065] The overall acetylation degree Ac% of this example is calculated to be 19.3%; the SEM-EDS characterization graph shows that the acetylated non-woven fabric obtained in this example is not broken.

[0066] Example 4

[0067] The specific operation is as in Example 1, with the only difference being that the loading of NaOH on the non-woven fabric after drying is controlled to be 50 mg per gram.

[0068] The overall acetylation degree Ac% of this example is calculated to be 25.6%; the SEM-EDS characterization graph shows that the acetylated non-woven fabric obtained in this example is not broken.

[0069] Comparative Example 1

[0070] In a 500 ml beaker, 200 ml of a 3% mass concentration sodium hydroxide solution is added, and 10 g of non-woven fabric is placed in the sodium hydroxide solution, and reacted for 10 min. After the reaction is completed, it is allowed to stand, and is washed with deionized water and ethanol, and is dried to obtain a non-woven fabric material, and the overall acetylation degree Ac% is calculated to be 0.00.

[0071] Comparative Example 2

[0072] In a 500 ml beaker, 200 ml of a 3% mass concentration sodium hydroxide solution is added, and 7.5 g of non-woven fabric is added to the sodium hydroxide solution for immersion, and then 15 g of vinyl acetate is added, and stirring is performed at room temperature, and the reaction is allowed to proceed for 10 min. to obtain a reacted non-woven fabric material, which is washed with deionized water and hot ethanol, and is dried to obtain an acetylated non-woven fabric, and the overall acetylation degree Ac% is calculated to be 0.80. The SEM-EDS characterization graph shows that the acetylated non-woven fabric obtained in this comparative example is broken.

[0073] Comparative Example 3

[0074] The specific operation steps are as in Example 1, with the only difference being that the vinyl acetate is added by means of dropwise addition, and the specific steps are as follows: 15 g of vinyl acetate is added dropwise to the non-woven fabric material loaded with NaOH, and after the reaction is completed, it is allowed to stand, and is washed with deionized water and ethanol, and is dried to obtain an acetylated non-woven fabric material, and the overall acetylation degree Ac% is calculated to be 2.68. The SEM-EDS characterization graph shows that the acetylated non-woven fabric obtained in this comparative example is not broken.

[0075] Comparative Example 4

[0076] The difference compared with Example 1 is that the method of spraying NaOH solution on the non-woven fabric is replaced by directly immersing the non-woven fabric in NaOH solution, and the rest of the parameters and steps are the same as Example 1.

[0077] The calculated acetylation degree Ac% of this comparative example is 2.30. It is found by SEM-EDS characterization map that the acetylated non-woven fabric obtained in this comparative example has no breakage.

[0078] Comparative Example 5

[0079] The difference compared with Example 1 is that the drying treatment of the non-woven fabric loaded with NaOH is cancelled, and the rest of the parameters and steps are the same as Example 1.

[0080] The calculated overall acetylation degree Ac% of this comparative example is 2.10. It is found by SEM-EDS characterization map that the acetylated non-woven fabric obtained in this comparative example has breakage.

[0081] By analyzing the acetylated fibers prepared in each example and comparative example, it can be seen that if the NaOH is not dried after being sprayed, and directly sprayed with vinyl acetate, the moisture in this part that is not dried is still sufficient to cause significant vinyl acetate hydrolysis side reaction. Because the NaOH catalyst still exists in the aqueous environment, if the spraying is uneven or the droplets are large, and the drying is not sufficient, a high concentration of alkaline aqueous solution may be formed in the local area, which may still cause a certain degree of degradation of cellulose; the separate spraying of NaOH is superior to the immersion method in terms of controlling the initial amount of alkali and water, but as long as there is significant moisture on the surface of the fiber during the subsequent esterification reaction, the side reaction of vinyl acetate cannot be fundamentally avoided, and the related by-product particles and catalyst consumption problems still exist. As for fiber damage, although it may be reduced, as long as the liquid alkaline aqueous solution is in contact with the fiber for a long time, the risk of degradation cannot be completely ruled out.

[0082] If NaOH is loaded on the cellulose raw material by immersion and then dried and sprayed with esterification agent, the problem of side reaction cannot be solved either. When a large amount of water containing dissolved NaOH evaporates from the fiber, NaOH may migrate and recrystallize, which may result in more uneven distribution of NaOH on the surface of the fiber after drying, forming high-concentration local alkali spots or larger NaOH crystalline particles. During the drying process, as the moisture decreases, the concentration of NaOH on the surface of the fiber will increase sharply. Long-term exposure to such a high-concentration alkaline environment at a relatively high temperature (even 80°C) may accelerate the degradation of cellulose, leading to brittle fibers and reduced strength, and even damage during the drying process, and by-products will still remain on the fiber.

[0083] If NaOH is loaded on the cellulose raw material by soaking, without drying, and then the esterification agent is atomized and sprayed on the non-woven fabric after soaking, the problem of side reactions cannot be solved either. The fiber substrate itself is a fiber that has not been effectively dried and has a large amount of water and alkali loaded by traditional impregnation method, and it cannot fundamentally solve the problem of vinyl acetate hydrolysis side reaction caused by moisture, nor can it avoid the byproduct particles and potential fiber damage caused thereby.

[0084] Figure 1 The infrared spectrum of the acetylated fiber prepared for Example 1 is shown in FIG. 1. Figure 1 It can be seen that the "spray precise loading" + "intermediate key drying" + "atomized esterification" can solve many technical problems existing in the prior art, and the acetylation degree of the non-woven fabric material is greatly improved. Figure 2 The infrared spectrum of the fiber prepared for Comparative Example 1 is shown in FIG. 2. No esterification reaction was performed, and there was no acetyl absorption peak in the infrared spectrum, only a peak at 1640 cm -1 . Figure 3 The infrared spectrum of the fiber prepared for Comparative Example 2 is shown in FIG. 3. The fiber was prepared by liquid phase impregnation, and the peak at 1731 cm -1 in the obtained infrared spectrum is quite 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.

[0085] From the SEM images in FIG. 4, Figures 4-6 it can be seen that in the micro-morphology of the non-woven fabric sample obtained by liquid phase impregnation, many fibers are broken, and there are also many particles (sodium acetate) formed by saponification reaction. The source of the particles is acetic acid produced by side reaction, and after neutralizing part of the NaOH, Na⁺ still exists in the system, which will form sodium acetate. The solubility of sodium acetate in water is limited, and 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 acetaldehyde formed in the side reaction will polymerize 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" to inhibit the side reaction, in the SEM images in FIG. 5, Figure 5 it can be seen that the surface of the fiber is smooth and has no cracks and breaks, and from FIGS. 6 and Figure 4 7, Figure 6 it can be seen that the fibers obtained by the method of liquid phase impregnation have particles loaded on the surface of the fibers, and there are also broken parts, which will affect the esterification efficiency.

[0086] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the 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 milligrams of catalyst is loaded on each gram of dried cellulose material; the residual moisture content of the dried cellulose material is not more than 0.5%; and the catalyst is an inorganic base and / or an alkaline inorganic salt.

2. The method for preparing acetylated fibers according to claim 1, characterized by, The drying temperature is 60-80℃.

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 includes any one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and sodium carbonate.

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

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

9. An acetylated fiber obtained by the preparation method of any one of claims 1-8.

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