Surface esterification product of cellulose, and preparation method therefor and use thereo

Abstract

Disclosed in the present application are a surface esterification product of cellulose, and a preparation method therefor and the use thereof. The preparation method therefor comprises the following steps: mixing a cellulose raw material, an alkaline aqueous solution and a vinyl ester esterifying agent, and conducting an esterification reaction, so as to obtain a surface esterification product of cellulose, wherein a solute in the alkaline aqueous solution is an inorganic alkali and / or an inorganic salt (the aqueous solution thereof being alkaline). The method uses an inorganic alkali and / or an inorganic salt (the aqueous solution thereof being alkaline) as a catalyst and a vinyl ester as an esterifying agent, and achieves rapid esterification of the surface of the cellulose raw material in an aqueous solution. The method is simple to operate, involves a rapid reaction, solves the problem that it is difficult to directly esterify the cellulose raw material in an aqueous solution, and enables the cellulose raw material to directly undergo surface esterification without drying or solvent replacement, thereby obviously improving the reaction efficiency. Moreover, after being subjected to surface esterification using the method disclosed by the present application, cellulose fibers can replace cellulose acetate fibers in some fields.

Description

A cellulose surface esterification product and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 4, 2023, with application number CN202311641835.0 and invention name “A cellulose surface esterification product, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the field of cellulose modification, and in particular relates to a cellulose surface esterification product and its preparation method and application. Background Art

[0003] Cellulose is one of the most abundant organic compounds on Earth. Its molecular structure primarily consists of thousands of glucose molecules linked by β-1,4-glycosidic bonds, forming a linear, fibrous structure. Cellulose is used to make paper and fiberboard, while cellulose derivatives are also used to prepare various chemicals, such as cellulose ethers and cellulose esters, for applications in food, pharmaceuticals, textiles, and building materials.

[0004] Cellulose acetate fiber is a common modified cellulose fiber that is currently widely used as cigarette filter material and in the textile field. In industry, cellulose acetate production uses acetic acid as a solvent, acetic anhydride as an esterifying agent, and sulfuric acid as a catalyst. Since sulfuric acid is used as a catalyst in this reaction, the cellulose is severely degraded during the preparation process. In addition, the prepared cellulose acetate needs to be dissolved in an acetone solution for spinning. Therefore, the production of cellulose acetate has very high requirements for the purity, degree of polymerization, whiteness and other indicators of the cellulose raw materials used. Generally, high-purity wood pulp or cotton pulp is required as raw materials to prepare cellulose acetate fiber. In addition, the production process of cellulose acetate fiber contains many harmful media and a long process, and the production is highly dangerous. The technology and raw materials for the domestic production of cellulose acetate are heavily dependent on imports, and the cost of preparing cellulose acetate fiber is extremely high.

[0005] Cellulose esterification provides a method for modifying cellulose, imparting enhanced properties such as hydrophobicity, flame retardancy, transparency, and high flexibility, thereby significantly expanding the application range of cellulose. In particular, surface esterification of cellulose can improve its hydrophobicity without altering its internal structure, effectively enhancing its compatibility with hydrophobic substrates. Side chains can also be introduced to enhance the interactions between cellulose molecules, thereby improving the mechanical strength and durability of cellulose materials. The introduction of various functional groups can also impart new chemical properties and functionalities to cellulose. Cellulose surface esterification can improve cellulose's properties, making it more suitable for a variety of applications. For example, in the pulp and paper industry, cellulose surface esterification can enhance the water and oil resistance of paper. In the food industry, it can be used to prepare food packaging materials to improve food freshness. Furthermore, in the pharmaceutical and textile industries, cellulose surface esterification can be used to improve product performance. This chemical reaction also has broad application potential in materials science and engineering, enabling the development of customized materials to meet diverse needs.

[0006] Cellulose esterification is a chemical process that converts the hydroxyl groups in the cellulose molecular structure into ester groups through an esterification reaction. In the cellulose esterification process, reagents such as acid anhydrides or acid chlorides are usually used to react with cellulose. These reagents provide acyl groups (-C=O-) to replace the hydrogen atoms on the hydroxyl groups. Through the esterification reaction, the properties of cellulose will change significantly. For example, the hydrophilicity and lipophilicity of cellulose will change, making it more suitable for combination with other materials. Current cellulose esterification research mainly uses dry cellulose materials in organic solvents. However, this method is time-consuming, and the volatility, toxicity, flammability and explosiveness of organic solvents and organic catalysts also have serious negative effects on the environment and organisms.

[0007] Summary of the Invention

[0008] The primary objective of this application is to provide a cellulose surface esterification product, its preparation method, and its application. The technical problem to be solved is to provide a method for preparing a cellulose surface esterification product that is simple to operate and fast in reaction. This method allows cellulose raw materials to be esterified in aqueous solution, eliminating the need for drying or solvent replacement, allowing for direct surface esterification, thus making it more practical. Furthermore, cellulose fibers surface-esterified using the method proposed in this application can replace cellulose acetate fibers in some applications.

[0009] The purpose of this application and the solution of its technical problems are achieved by adopting the following technical solutions.

[0010] An embodiment of the present application provides a method for preparing a cellulose surface esterification product, comprising the following steps: mixing a cellulose raw material, an alkaline aqueous solution, and a vinyl ester esterifying agent, conducting an esterification reaction, and obtaining a cellulose surface esterification product; the solute in the alkaline aqueous solution is an inorganic base and / or the aqueous solution is an alkaline inorganic salt.

[0011] Preferably, the cellulose raw material is at least one of cellulose powder, pulp fiber, cotton fiber, nanocellulose, microcrystalline cellulose, regenerated cellulose and wood fiber.

[0012] Preferably, the inorganic base is an inorganic strong base or an inorganic weak base, the inorganic strong base is at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide, and the inorganic weak base is ammonia water; the alkaline inorganic salt of the aqueous solution is at least one of potassium carbonate, sodium carbonate and sodium bicarbonate.

[0013] Preferably, the mixing method is to add the cellulose raw material into the alkaline aqueous solution and stir evenly to form a mixed solution, and then add the vinyl ester esterifying agent into the mixed solution.

[0014] Preferably, taking the alkaline aqueous solution as 100%, the mass fraction of the solute in the alkaline aqueous solution is 0.15-25%.

[0015] Preferably, when the solute is an inorganic strong base, the mass fraction of the solute in the alkaline aqueous solution is 0.15-10%; when the solute is an inorganic weak base or the aqueous solution is an alkaline inorganic salt, the mass fraction of the solute in the alkaline aqueous solution is 1-25%.

[0016] Preferably, the mixing method is: soaking the cellulose raw material in the alkaline aqueous solution, then taking out the soaked cellulose raw material and contacting it with the vinyl ester esterifying agent.

[0017] Preferably, taking the alkaline aqueous solution as 100%, the mass fraction of the solute in the alkaline aqueous solution is 0.5-40%.

[0018] Preferably, when the solute is an inorganic strong base, the mass fraction of the solute in the alkaline aqueous solution is 0.5-10%; when the solute is an inorganic weak base or the aqueous solution is an alkaline inorganic salt, the mass fraction of the solute in the alkaline aqueous solution is 1-40%.

[0019] Preferably, the impregnated cellulose raw material is contacted with the vinyl ester esterifying agent by at least one of liquid phase impregnation and gas phase contact.

[0020] The present application also provides a cellulose surface esterification product, which is prepared by the preparation method described in the above technical solution.

[0021] The present application also provides an application of the cellulose surface esterification product described in the above technical solution in cigarette filter materials, pulp, paper, food packaging, textile fields or pharmaceutical industry.

[0022] Preferably, the cellulose surface esterification product is used as a substitute for cellulose acetate fiber.

[0023] Through the above technical solution, the present application provides a cellulose surface esterification product and its preparation method and application, which have at least the following advantages:

[0024] (1) The present application does not require drying or solvent replacement of the cellulose raw material, and the cellulose raw material can be directly surface esterified in an aqueous solution, which is more practical.

[0025] (2) Compared with organic base catalysts, this method uses inorganic bases and / or inorganic salts with alkaline aqueous solutions as catalysts, which has lower costs and faster reaction rates. The surface esterification of the cellulose raw material can be achieved by immersing the cellulose raw material in alkaline aqueous solutions and vinyl ester solutions, thereby greatly reducing the consumption of vinyl ester.

[0026] (3) The reaction can be completed rapidly at room temperature without the need for heating, further reducing the number of steps and equipment required, and lowering production costs. The preparation process proposed in this application is fast, simple to operate, and more environmentally friendly and economical, greatly promoting industrialization and enhancing the practical application potential of modified cellulose.

[0027] (4) The surface of cellulose fiber is esterified by the method proposed in this application. The surface-esterified cellulose fiber prepared can replace cellulose acetate fiber in some fields. The operation is very simple and does not require the tedious steps of completely esterifying cellulose and then dissolving and spinning to prepare cellulose acetate fiber through the traditional method. Cellulose acetate fiber has strict requirements on the purity, polymerization degree, whiteness and other indicators of cellulose raw materials. This application can directly use cellulose fibers such as cotton fiber and regenerated cellulose fiber as raw materials without considering the purity, polymerization degree and other indicators of cellulose raw materials. The use of traditional acid anhydride acetylation of cellulose fiber will cause severe degradation of cellulose fiber and dissolution in the acid anhydride system. The aqueous phase ester exchange reaction used in this application can make acetylation occur only on the surface of cellulose fiber without causing degradation and dissolution of cellulose fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is an infrared spectrum of the cellulose surface esterification product of Example 7;

[0029] FIG2 is an infrared spectrum of the cellulose surface esterification product of Example 22;

[0030] FIG3 is an infrared spectrum of the cellulose sample of Comparative Example 1. DETAILED DESCRIPTION

[0031] To further illustrate the technical means and effectiveness of this application to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, provides a detailed description of the specific embodiments, structures, features, and effectiveness of a cellulose surface-esterified product, its preparation method, and its application, as well as its specific implementation methods, structures, features, and effectiveness. In the following description, different "some embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0032] The present invention provides a method for preparing a cellulose surface esterification product, using an inorganic base catalyst to achieve surface esterification of cellulose in an aqueous solution. The method comprises the following steps: mixing a cellulose raw material, an alkaline aqueous solution, and a vinyl ester esterifying agent, and conducting an esterification reaction to obtain the cellulose surface esterification product. The solute in the alkaline aqueous solution is an inorganic base and / or the aqueous solution is an alkaline inorganic salt.

[0033] Specifically, a cellulose raw material, an alkaline aqueous solution, and a vinyl ester esterifying agent are mixed and vigorously stirred at room temperature to carry out an esterification reaction. After the reaction is completed, the mixture is allowed to stand, filtered, and the solid is washed and dried to obtain a cellulose surface esterified product.

[0034] In the aforementioned esterification reaction, the OH in the alkaline aqueous solution - On the one hand, it acts as a catalyst to make the cellulose raw material react with the vinyl ester esterifying agent to esterify the cellulose surface; on the other hand, OH - It will undergo hydrolysis reaction with esters, OH - It will react with vinyl ester esterifying agents and esters grafted on the cellulose surface. - After the cellulose is completely consumed, the reaction stops. Therefore, in this reaction system, the vinyl ester esterifying agent is in excess. In actual operation, the amount of alkaline aqueous solution and vinyl ester esterifying agent is adjusted according to the degree of esterification of the cellulose raw material surface.

[0035] The inorganic base in the alkaline aqueous solution is at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide and ammonia water, and the alkaline inorganic salt in the aqueous solution is at least one of potassium carbonate, sodium carbonate or sodium bicarbonate.

[0036] The aforementioned cellulose raw material is at least one of cellulose powder, pulp, cotton fiber, nanocellulose, regenerated cellulose and wood fiber.

[0037] The aforementioned vinyl ester esterifying agent is at least one of vinyl acetate, vinyl propionate, vinyl butyrate, vinyl hexanoate and vinyl benzoate.

[0038] The aforementioned esterification reaction can proceed at room temperature, and can also occur at lower temperatures of 0°C or above. It is generally performed at room temperature, and no temperature control measures such as heating are required. At room temperature, the esterification reaction lasts from 10 to 600 seconds. When using a strong inorganic base such as sodium hydroxide or potassium hydroxide, the reaction is complete in approximately 10 seconds. When using an alkaline aqueous solution of an inorganic salt, the reaction is complete in approximately 2 minutes.

[0039] In some embodiments, in the aforementioned preparation method, the mixing method comprises adding the aforementioned cellulose raw material to the aforementioned alkaline aqueous solution and stirring uniformly to form a mixed solution, and then adding the aforementioned vinyl ester esterifying agent to the mixed solution. By first mixing the aforementioned cellulose raw material with the aforementioned alkaline aqueous solution and then adding the vinyl ester esterifying agent to carry out an esterification reaction with the cellulose, this method does not require drying or organic solvent replacement of the cellulose raw material, thereby eliminating the need for processing the cellulose raw material.

[0040] In some embodiments, in the aforementioned preparation method, the aforementioned alkaline aqueous solution is 100%, and the mass fraction of the solute in the aforementioned alkaline aqueous solution is 0.15-25%.

[0041] Since the esterification reaction and hydrolysis reaction occur simultaneously in the reaction process, the OH - The content of OH is too low, the degree of esterification of cellulose surface is low, and the practical value of the product is low; - If the content is too high, a large amount of vinyl ester esterification agent will be consumed in vain, increasing product costs. Therefore, the mass fraction of the solute in the alkaline aqueous solution is controlled to be 0.15-25%. Specifically, when using a strong base such as sodium hydroxide or potassium hydroxide, the mass fraction of the solute in the alkaline aqueous solution is 0.15-10%; when using a weak base such as ammonia water or an alkaline inorganic salt such as potassium carbonate or sodium carbonate, the mass fraction of the solute in the alkaline aqueous solution is 1-25%.

[0042] In some embodiments, in the aforementioned preparation method, the mixing method is: soaking the aforementioned cellulose raw material in the aforementioned alkaline aqueous solution, then taking out the soaked cellulose raw material and contacting it with the aforementioned vinyl ester esterifying agent.

[0043] OH - While the esterification reaction is catalytic, the inorganic base reacts with the vinyl ester esterifying agent. The cellulose raw material is immersed in an alkaline aqueous solution, removed from the solution, and then added to the vinyl ester solution with vigorous stirring to initiate the esterification reaction. This method significantly reduces the consumption of alkaline aqueous solution and vinyl ester, significantly lowering costs.

[0044] In some embodiments, in the aforementioned preparation method, the mass fraction of the solute in the alkaline aqueous solution is 0.5-40%. Since this reaction primarily utilizes the inorganic base as an esterification catalyst, it is not consumed as a catalyst, but its catalytic hydrolysis of the esterifying agent is a side reaction and is consumed. Therefore, the mass fraction of the solute in the alkaline aqueous solution is selected based on the water absorption capacity of the cellulose fiber raw material and the degree of esterification of the cellulose surface. If the cellulose fiber has a strong water absorption capacity or a low degree of surface esterification is required, the concentration of the inorganic base is relatively low; if the cellulose fiber has a weak water absorption capacity or a high degree of surface esterification is required, the concentration of the inorganic base is relatively high. Therefore, the mass fraction of the solute in the alkaline aqueous solution is controlled to be 0.5-40%. Specifically, when using a strong base such as sodium hydroxide or potassium hydroxide, the mass fraction of the solute in the alkaline aqueous solution is 0.5-10%. When using a weak base such as ammonia or an alkaline inorganic salt such as potassium carbonate or sodium carbonate, the mass fraction of the solute in the alkaline aqueous solution is 1-40%.

[0045] In some embodiments, in the aforementioned preparation method, the contact between the impregnated cellulose raw material and the vinyl ester esterifying agent is at least one of liquid-phase impregnation and vapor-phase contact. The reaction can also occur after the vinyl ester esterifying agent is vaporized and then contacted with the cellulose raw material impregnated with the inorganic alkaline solution. This method eliminates the need for filtering and separating the product from the vinyl ester esterifying agent after the reaction, thereby conserving raw materials.

[0046] In some embodiments, in the aforementioned preparation method, the aforementioned cellulose raw material is at least one of pulp fiber, cotton fiber, regenerated cellulose fiber and wood fiber. The surface-esterified cellulose fiber prepared using cellulose fiber as raw material can replace cellulose acetate fiber in some areas. The operation is simple and there is no need to use the tedious steps of completely esterifying the cellulose and then dissolving and spinning the cellulose acetate fiber through the traditional method. Cellulose acetate fiber has strict requirements on the purity, degree of polymerization, whiteness and other indicators of the cellulose raw material. The present application directly uses cellulose fibers such as cotton fiber and regenerated cellulose fiber as raw materials, without considering the purity, degree of polymerization and other indicators of the cellulose raw material. The use of traditional acid anhydride acetylated cellulose fibers can easily lead to severe degradation of the cellulose fibers, thereby affecting their performance.

[0047] In some embodiments, in the aforementioned preparation method, the mass fraction of the solute in the aforementioned alkaline aqueous solution is 1-15%. Within this range, the surface esterification of cellulose is better and the degree of acetylation is higher, while using a smaller amount of reactants. This can significantly improve the surface hydrophobicity of the cellulose raw material and its compatibility with non-polar materials and solvents. Specifically, when using a strong base such as sodium hydroxide or potassium hydroxide, the mass fraction of the solute in the alkaline aqueous solution is 1-6%. When using a weak base such as ammonia water or an alkaline inorganic salt such as potassium carbonate or sodium carbonate as an aqueous solution, the mass fraction of the solute in the alkaline aqueous solution is 1-15%.

[0048] The present embodiment provides a cellulose surface esterification product, which is prepared by any of the aforementioned preparation methods.

[0049] The embodiments of the present application provide an application of the aforementioned cellulose surface esterification product in cigarette filter materials, pulp, paper, food packaging, textile fields or pharmaceutical industry.

[0050] The present application will be further described below in conjunction with specific embodiments, but this should not be construed as limiting the scope of protection of the present application. Non-essential improvements and adjustments made to the present application by technicians in this field based on the above-mentioned contents of the present application still fall within the scope of protection of the present application.

[0051] Unless otherwise specified, the materials and reagents mentioned below are all commercially available products familiar to those skilled in the art. Unless otherwise specified, the methods described are all well-known methods in the art. Unless otherwise defined, technical or scientific terms used should have the same meanings as those of ordinary skill in the art to which this application belongs.

[0052] In the following examples and comparative examples, the microcrystalline cellulose particles used are 40-60 μm in size; the cellulose powder particles are 25 μm in size; the regenerated cellulose fibers are viscose fiber bundles with a diameter of 200 μm; and the wood fibers are poplar veneers with a thickness of 1 mm, a length of 1 cm, and a width of 1 cm.

[0053] The overall acylation degree Ac% refers to the percentage of acylated groups in the sample after acylation to the total sample mass.

[0054] The calculation method of the overall acylation degree Ac% in Examples 1 to 17 is as follows: an infrared spectrometer is used to scan the esterification product on the surface of cellulose to obtain a characteristic spectrum, and the spectrum is baseline corrected and the wavelength is 1732 cm -1 and 1061cm -1 The absorbance ratio at 1732 cm was divided by the coefficient 0.0282 to calculate the degree of esterification of the cellulose surface esterification product. -1 where is the corresponding acyl group, Wavenuber represents the wave number, and Transmittance represents the transmission coefficient.

[0055] Example 1

[0056] (1) In a 30 mL conical flask, 9.5 mL of 0.15% sodium hydroxide solution and 0.5 g of microcrystalline cellulose were added to prepare a mixed solution. Then, 3 mL of vinyl acetate was added. The mixture was vigorously stirred at room temperature to form a vortex state to ensure that the reactants were evenly mixed and reacted for 30 seconds.

[0057] (2) After the reaction is completed, the mixture is allowed to stand and filtered to obtain a filtrate and a solid. The solid is washed and dried to obtain a cellulose surface esterification product. The degree of esterification of the cellulose surface esterification product is determined by infrared spectrometry, and the overall acetylation degree (Ac%) is calculated to be 0.12.

[0058] Example 2

[0059] The difference from Example 1 is that 8 mL of 1% sodium hydroxide solution, 2 g of microcrystalline cellulose, and 5 mL of vinyl acetate were added. The degree of esterification of the cellulose surface esterification product was measured using an infrared spectrometer, and the overall acetylation degree (Ac%) was calculated to be 0.75.

[0060] Example 3

[0061] The difference from Example 1 is that 8 mL of 6% sodium hydroxide solution, 2 g of microcrystalline cellulose, and 10 mL of vinyl acetate were added. The degree of esterification of the cellulose surface esterification product was measured using an infrared spectrometer, and the overall acetylation degree (Ac%) was calculated to be 1.20.

[0062] Example 4

[0063] The difference from Example 1 is that 8 mL of 10% sodium hydroxide solution, 2 g of microcrystalline cellulose, and 10 mL of vinyl acetate were added. The degree of esterification of the cellulose surface esterification product was measured using an infrared spectrometer, and the overall acetylation degree (Ac%) was calculated to be 0.71.

[0064] Example 5

[0065] The difference from Example 1 is that 7 mL of 1% sodium carbonate solution, 3 g of microcrystalline cellulose, and 10 mL of vinyl acetate were added and the reaction was carried out for 2 minutes. The degree of esterification of the cellulose surface esterification product was measured by infrared spectroscopy, and the overall acetylation degree (Ac%) was calculated to be 0.40.

[0066] Example 6

[0067] The difference from Example 1 is that 7 mL of 10% sodium carbonate solution, 3 g of microcrystalline cellulose, and 10 mL of vinyl acetate were added and the reaction was carried out for 2 minutes. The degree of esterification of the cellulose surface esterification product was measured by infrared spectroscopy, and the overall acetylation degree (Ac%) was calculated to be 1.09.

[0068] Example 7

[0069] The difference from Example 1 is that 7 mL of 15% sodium carbonate solution, 3 g of microcrystalline cellulose, and 10 mL of vinyl acetate were added and the reaction was allowed to proceed for 2 minutes. The degree of esterification of the cellulose surface esterification product was measured using infrared spectroscopy, as shown in Figure 1. The calculated overall acetylation degree (Ac%) was 1.45.

[0070] Example 8

[0071] The difference from Example 1 is that 9 mL of 20% potassium carbonate solution, 1 g of microcrystalline cellulose, and 10 mL of vinyl acetate were added and the reaction was carried out for 2 minutes. The degree of esterification of the cellulose surface esterification product was measured by infrared spectroscopy, and the overall acetylation degree (Ac%) was calculated to be 1.23.

[0072] Example 9

[0073] The difference from Example 1 is that 9 mL of 25% potassium carbonate solution, 1 g of microcrystalline cellulose, and 10 mL of vinyl acetate were added and the reaction was carried out for 2 minutes. The degree of esterification of the cellulose surface esterification product was measured by infrared spectroscopy, and the overall acetylation degree (Ac%) was calculated to be 1.10.

[0074] Example 10

[0075] The difference from Example 6 is that cellulose powder is used, vinyl propionate is used as the esterifying agent, and the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acylation degree is calculated to be 0.75.

[0076] Example 11

[0077] (1) 0.1 g of microcrystalline cellulose was immersed in a 0.5% sodium hydroxide aqueous solution for 30 seconds;

[0078] (2) The soaked microcrystalline cellulose was taken out and immersed in 10 mL of vinyl acetate. The mixture was vigorously stirred at room temperature to form a vortex state to allow the reactants to be evenly mixed and reacted for 60 seconds.

[0079] (3) The microcrystalline cellulose after the reaction was taken out, washed, and dried to obtain surface-esterified microcrystalline cellulose. The esterification degree of the cellulose surface esterification product was measured using an infrared spectrometer, and the overall acetylation degree (Ac%) was calculated to be 0.08.

[0080] Example 12

[0081] The difference from Example 11 is that a sodium hydroxide aqueous solution with a mass fraction of 1% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 0.25.

[0082] Example 13

[0083] The difference from Example 11 is that a sodium hydroxide aqueous solution with a mass fraction of 4% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 2.16.

[0084] Example 14

[0085] The difference from Example 11 is that a sodium hydroxide aqueous solution with a mass fraction of 6% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 1.85.

[0086] Example 15

[0087] The difference from Example 11 is that a sodium hydroxide aqueous solution with a mass fraction of 10% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 1.73.

[0088] Example 16

[0089] The difference from Example 11 is that a sodium carbonate aqueous solution with a mass fraction of 1% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 0.10.

[0090] Example 17

[0091] The difference from Example 11 is that a sodium carbonate aqueous solution with a mass fraction of 10% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 2.05.

[0092] Example 18

[0093] The difference from Example 11 is that a sodium carbonate aqueous solution with a mass fraction of 15% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 2.68.

[0094] Example 19

[0095] The difference from Example 11 is that a sodium carbonate aqueous solution with a mass fraction of 20% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 1.82.

[0096] Example 20

[0097] The difference from Example 11 is that a potassium carbonate aqueous solution with a mass fraction of 30% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 1.62.

[0098] Example 21

[0099] The difference from Example 11 is that a potassium carbonate aqueous solution with a mass fraction of 40% is used; the esterification degree of the esterified product on the cellulose surface is measured by infrared spectrometer, and the overall acetylation degree Ac% is calculated to be 1.25.

[0100] Example 22

[0101] (1) 0.1 g of regenerated cellulose fiber was immersed in a 5.0% sodium hydroxide aqueous solution for 30 seconds;

[0102] (2) The regenerated cellulose fibers were taken out after immersion, immersed in 10 mL of vinyl hexanoate and stirred vigorously for 60 seconds;

[0103] (3) The regenerated cellulose fibers after the reaction were taken out, washed, and dried to obtain surface-esterified regenerated cellulose fibers. The characteristic spectrum of the cellulose surface esterification products was measured by infrared spectrometer, as shown in FIG2 . The overall acylation degree Ac% was calculated to be 1.37, which can replace cellulose acetate fibers in some fields.

[0104] Example 23

[0105] The difference from Example 22 is that wood fiber and 10% sodium hydroxide aqueous solution were used; the characteristic spectrum of the esterification product on the cellulose surface was measured by infrared spectrometer, and the overall acylation degree Ac% was calculated to be 1.13.

[0106] Comparative Example 1

[0107] (1) Add 8 mL of 10% sodium carbonate solution and 2 g of microcrystalline cellulose to a 30 mL conical flask, stir vigorously at room temperature to make a mixed solution, and react for 30 seconds.

[0108] (2) After the reaction is completed, the cellulose sample is allowed to stand, filtered, and the solid is washed and dried to obtain the cellulose sample. The cellulose sample is measured by infrared spectrometer, as shown in FIG3 , and the overall acetylation degree Ac% is calculated to be 0.00%.

[0109] Comparative Example 2

[0110] (1) In a 30 mL conical flask, add 7.52 mL of water, 2 g of microcrystalline cellulose, and 0.48 g of 4-dimethylaminopyridine to prepare a mixed solution. Then add 10 mL of vinyl acetate and vigorously stir the mixture at room temperature until it forms a vortex state. The reactants are mixed evenly and react for 30 seconds.

[0111] (2) After the reaction is completed, the mixture is allowed to stand and filtered to obtain a filtrate and a solid. The solid is washed and dried to obtain a cellulose surface esterification product. The degree of esterification of the cellulose surface esterification product is determined by infrared spectrometry, and the overall acetylation degree (Ac%) is calculated to be 0.43.

[0112] The experimental data of Examples 1 to 10 are summarized in Table 1.

[0113] Table 1 Summary of experimental data of Examples 1 to 10

[0114] The experimental data of Examples 11 to 23 are summarized in Table 2.

[0115] Table 2 Summary of experimental data of Examples 11 to 23

[0116] It can be seen from the above examples and comparative examples that the method proposed in the present application uses inorganic bases and / or alkaline inorganic salts in aqueous solution as catalysts and vinyl esters as esterifying agents to achieve rapid esterification of the surface of cellulose raw materials in aqueous solution. This method is simple to operate and has a rapid reaction. The overall acylation degree Ac% of the cellulose surface esterification product can reach 2.68.

[0117] The technical features in the claims and / or the specification of this application may be combined, and the manner of combination is not limited to the combinations obtained by reference in the claims. The technical solutions obtained by combining the technical features in the claims and / or the specification are also within the scope of protection of this application.

[0118] The above is merely a preferred embodiment of the present application and does not constitute any form of limitation to the present application. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present application still fall within the scope of the technical solution of the present application.

Claims

1. A method for preparing a cellulose surface esterification product, characterized in that: The following steps are involved: The cellulose raw material, the alkaline aqueous solution and the vinyl ester esterifying agent are mixed to carry out an esterification reaction to obtain a cellulose surface esterification product; The solute in the alkaline aqueous solution is an inorganic base and / or the aqueous solution is an alkaline inorganic salt.

2. The preparation method according to claim 1, characterized in that: The cellulose raw material is at least one of cellulose powder, pulp fiber, cotton fiber, nanocellulose, microcrystalline cellulose, regenerated cellulose and wood fiber.

3. The preparation method according to claim 1, characterized in that: The inorganic base is an inorganic strong base or an inorganic weak base, the inorganic strong base is at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide, and the inorganic weak base is ammonia water; the aqueous solution is an alkaline inorganic salt is at least one of potassium carbonate, sodium carbonate and sodium bicarbonate.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The mixed method is: The cellulose raw material is added into the alkaline aqueous solution and stirred evenly to form a mixed solution, and then the vinyl ester esterifying agent is added into the mixed solution.

5. The preparation method according to claim 4, characterized in that: Taking the alkaline aqueous solution as 100%, the mass fraction of the solute in the alkaline aqueous solution is 0.15-25%.

6. The preparation method according to claim 5, characterized in that: When the solute is an inorganic strong base, the mass fraction of the solute in the alkaline aqueous solution is 0.15 to 10%; When the solute is an inorganic weak base or the aqueous solution is an alkaline inorganic salt, the mass fraction of the solute in the alkaline aqueous solution is 1-25%.

7. The preparation method according to any one of claims 1 to 3, characterized in that: The mixed method is: The cellulose raw material is immersed in the alkaline aqueous solution, and then the immersed cellulose raw material is taken out and brought into contact with the vinyl ester esterifying agent.

8. The preparation method according to claim 7, characterized in that: Taking the alkaline aqueous solution as 100%, the mass fraction of the solute in the alkaline aqueous solution is 0.5-40%.

9. The preparation method according to claim 8, characterized in that: When the solute is an inorganic strong base, the mass fraction of the solute in the alkaline aqueous solution is 0.5 to 10%; When the solute is an inorganic weak base or the aqueous solution is an alkaline inorganic salt, the mass fraction of the solute in the alkaline aqueous solution is 1 to 40%.

10. The preparation method according to claim 7, characterized in that: The contact between the impregnated cellulose raw material and the vinyl ester esterification agent is at least one of liquid phase impregnation and gas phase contact.

11. The preparation method according to claim 1, characterized in that: The vinyl ester esterifying agent is at least one of vinyl acetate, vinyl propionate, vinyl butyrate, vinyl hexanoate and vinyl benzoate.

12. The preparation method according to claim 1, characterized in that: The temperature of the esterification reaction is 0°C to room temperature, and the time of the esterification reaction is 10 to 600 seconds.

13. The preparation method according to claim 2, characterized in that: The particle size of the microcrystalline cellulose is 40 to 60 μm; The particle size of the cellulose powder is 25 μm; The regenerated cellulose fiber is a viscose fiber tow with a diameter of 200 μm; The wood fiber is a poplar veneer with a thickness of 1 mm, a length of 1 cm and a width of 1 cm.

14. A cellulose surface esterification product, characterized in that: Prepared by the preparation method according to any one of claims 1 to 13.

15. Use of the cellulose surface esterification product according to claim 14 in cigarette filter materials, pulp, paper, food packaging, textile fields or pharmaceutical industry.

16. The use according to claim 15, characterized in that The cellulose surface esterification product is used as a substitute for cellulose acetate fiber.

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