CN107254004A - Carboxymethyl cellulose acetate propionate ester and its production and use - Google Patents

Abstract

The present invention relates to a kind of carboxymethyl cellulose acetate propionate and its preparation method and application. The present invention obtains carboxymethyl cellulose acetate propionate that can replace CMCAB as a leveling agent for water-based coatings by preparing low-substituted sodium carboxymethyl cellulose, acidifying, activating, esterifying and purifying. The carboxymethyl cellulose acetate propionate provided by the invention can replace CMCAB for application in the coating field, and has better performance than CMCAB. The method provided by the invention has short production cycle, low production temperature, low raw material consumption, and greatly reduces the manufacturing cost of the operation process. Due to the strengthening of environmental protection awareness, the market demand for low-VOC water-based coatings is increasing, and the industry using water-based coatings is also gradually increasing. Increase, the application prospect of carboxymethylcellulose acetate propionate is broad, and the content of substituents can be adjusted to prepare different types of products, which are suitable for various fields and meet a wide range of market demands.

Description

Carboxymethyl cellulose acetate propionate and its preparation method and use

technical field

The invention belongs to the field of water-based paint leveling agent materials, and in particular relates to carboxymethyl cellulose acetate propionate and its preparation method and application.

Background technique

Cellulose and its derivatives are very important fine chemical products, and one of the important application fields is as a coating film former. A large number of hydrogen bonds between and within the cellulose molecules can provide sufficient strength to make the paint have properties such as sanding and waxing; while the modification of the hydroxyl group can obtain derivatives with different functions, which can give it Wider application space. Cellulose-based paints are mainly divided into two categories, one is traditional inorganic ester cellulose coatings, the other is organic ether ester coatings, especially the recently developed water-based ether ester coatings. Among the inorganic ester cellulose coatings, the coating represented by nitrocellulose is the most typical, and its application is also very large. However, due to the constraints of high VOC content, low solid content, and serious environmental pollution, people have developed Many nitrocellulose-based composite coatings are usually improved by adding other film-forming substances, but the degree of improvement is often limited. Therefore, the development of water-based cellulose nitrate ester coatings is also the direction of industry development.

The coatings represented by cellulose organic ether esters, especially cellulose acetate butyrate and carboxymethyl acetate butyrate, have important applications in many special occasions. The use of cellulose esters in binders, modified resins or pre-film materials can provide coatings with many excellent properties. For example: improve the fluidity of paint, reduce shrinkage, shorten drying time, reduce agglomeration, etc.; at the same time, it is also a stable carrier for metal pigments, with good polishing, UV stability, anti-yellowing performance, etc.; it can also improve paint spraying resistance, cold crack resistance, solvent resistance and smoothness, reduce the outflow of plasticizer during the use of the paint, improve the viscosity controllability of the paint during use, uniform dispersion of pigments, layer control of metal flakes and paint resolvability, etc. Coatings for different purposes have different performance requirements, and their physical and chemical properties can be controlled by changing the degree of group substitution, hydroxyl content and chain length in the polymer.

Cellulose esters improve the orientation of the metal flakes in the primer. Due to the presence of cellulose ester, the viscosity of the paint primer will drop rapidly during the drying process, especially through refrigeration drying, the cellulose ester will cause the film to shrink, and the metal foil will be arranged in parallel along the surface of the shell; during the drying process Generally, the transparent layer is used to protect the bottom layer of the paint, but the strong solvent in it will redissolve the bottom layer of the paint, resulting in uneven bright and black and spot areas on the surface. Due to its relatively high molecular weight, cellulose ester dissolves very slowly in solvents, so it can prevent the strong solvent in the transparent layer from redissolving the bottom layer of the paint during use. Cellulose organic or inorganic esters play a very important role in the field of coating applications.

Carboxymethyl cellulose acetate butyrate (CMCAB) is a carboxylated cellulose resin, which is produced by introducing carboxymethyl groups into general cellulose acetate butyrate (CAB). Cellulose esters are more widely used in coatings than general cellulose esters. The carboxymethyl groups introduced into the cellulose backbone make cellulose acetate butyrate (CAB) sufficiently hydrophilic, while The acetate and butyrate moieties in turn make it sufficiently lipophilic. The acid value of CMCAB is about 60mgKOH/g. It can be preformed into water dispersion or solution through alkali neutralization (such as: dimethylethanolamine), and can be used as an additive or film former in low-VOC water-based coatings. This water dispersion or solution not only maintains the characteristics of cellulose resin, but also can be easily added to various water-based coatings. Through the volatilization of water and solvent in the coating film, it can become a water-insoluble high relative molecule. High quality, high Tg rigid coating film. CMCAB has near-Newtonian rheology, high Tg, and a sharp viscosity/solids relationship. These are also the common characteristics of cellulose esters, which enable cellulose esters to be used in the coatings industry. A high Tg can improve the rate of dry contact, anti-blocking and anti-staining properties and hardness. The viscosity/solids power exponential relationship can improve the controllability, redissolution and sag resistance of metal flakes. CMCAB improves the leveling of coatings and prevents imperfections such as potholes and pinholes.

In actual production, the production process of CMCAB will cause a lot of interference, pollution and corrosion to the production process equipment, employees and environment due to the strong rancid smell of butyric acid, and the smell persists.

Contents of the invention

Aiming at the defects in the prior art, the present invention provides a carboxymethylcellulose acetate propionic acid that can replace CMCAB, has short production cycle, low temperature in the production process, small unit energy consumption, low raw material loss, and relatively simple operation process. Esters and methods for their production.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The preparation method of carboxymethyl cellulose acetate propionate provided by the invention comprises steps:

A. Preparation of low-substituted sodium carboxymethyl cellulose; Sodium carboxymethyl cellulose is CMC;

B. Prepare carboxymethyl cellulose hydrogen after acidifying the low-substituted sodium carboxymethyl cellulose;

C. Activation of carboxymethyl cellulose hydrogen;

D. Esterifying the activated carboxymethyl cellulose with hydrogen to prepare carboxymethyl cellulose acetate propionate.

That is to say, the method of the present invention uses low-substituted sodium carboxymethylcellulose as a raw material, and the degree of substitution of the low-substituted sodium carboxymethylcellulose is 0.1-1.5, and after acidification and activation treatment with acid solution, it is converted into Carboxymethyl cellulose hydrogen, wash with water and acetic acid to remove the acid and water in the slurry, then add acetic anhydride, propionic anhydride and catalyst to carboxylate the washed slurry to prepare CMCAP.

The CMCAP prepared by this method has reasonable distribution of carboxymethyl and carboxylate groups, good rigidity, fluidity, solubility, compatibility, hydroxyl stability, chemical resistance and oil resistance, and the process is compatible with industrial production Close connection, easy to apply to industrial production. In addition, compared with the production process of CMCAB, CMCAP does not need to use butyric acid, and the propionic acid used has a small taste, and it is easy to disperse and does not stay.

And the CMCAP prepared by the present invention has nearly the same physical and chemical properties as CMCAB, and can completely replace CMCAB for application in the field of coatings. The prepared CMCAP is even better than CMCAB in some aspects: the oil solubility of CMCAP is weaker than that of CMCAB, and the rigidity of CMCAP segments It is better than CMCAB, and because the acidity of propionic acid is stronger than that of butyric acid, the chemical stability of the combined ester CMCAP is better than that of CMCAB. Therefore, under the same degree of substitution, the chemical resistance, oil resistance and rigidity of CMCAP are better than those of CMCAB is good. Especially for coatings, glass transition temperature Tg is an important indicator. In rigid coatings requiring high Tg, CMCAP has higher Tg and rigidity than CMCAB as a short branched chain structure.

The parts added by the materials described in the present invention are all parts by mass unless otherwise specified.

Further, the preparation process of low-substituted sodium carboxymethylcellulose in step A described in the preparation method of above-mentioned carboxymethylcellulose acetate propionate is as follows:

a. Feeding: Add 100 parts of cellulose powder, 1000-3000 parts of organic solvent, and 30-60 parts of water into the reactor, wherein the organic solvent is one or more combinations of ethanol, propanol, isopropanol and acetone;

b. Gas protection: After feeding is completed, inert gas is introduced, and inert gas is introduced after removing the air in the reactor;

c. Alkalinization: add 100-500 parts of sodium hydroxide aqueous solution with a mass fraction of 20-35%, and alkalize at a constant temperature of 10-40°C for 40-120min;

d. Etherification: adjust the system temperature to 10-20°C, and add 100-500 parts of etherification agent by spraying evenly within 30-120 minutes. The etherification agent is 50%-80% chloroacetic acid organic solvent solution, of which organic The solvent is one of ethanol, propanol, isopropanol, acetone or a combination thereof, the temperature is raised to 30-60°C for constant temperature etherification for 30-180 minutes, and then the temperature is controlled at 50-80°C to continue etherification for 30-180 minutes;

e. Neutralization, washing and drying: add 10-50 parts of acid to terminate the reaction, and the crude product is preliminarily removed from the organic solvent in the material through a stripping process, and then washed with ethanol/water solution to remove reaction by-products and impurities, dried and pulverized; The components of the acid used in the reaction are one or more combinations of acetic acid, hydrochloric acid and sulfuric acid; the ethanol/water solution is the aqueous solution of ethanol.

Further, the preparation process of step B described in the above-mentioned preparation method of carboxymethylcellulose acetate propionate is: add 100 parts of low-substituted carboxymethyl cellulose prepared in step A into In the reactor, the acidification time is 20-120min, the acidification temperature is 10-50°C, and the acidification is completed and washed with water for 3-5 times.

Further, in the above-mentioned preparation method of carboxymethylcellulose acetate propionate, the acidifying solution is an aqueous solution of one or more combinations of hydrochloric acid, sulfuric acid, acetic acid, and propionic acid, and its mass fraction is 10-30% .

Further, in the preparation method of the above-mentioned carboxymethylcellulose acetate propionate, the preparation process of the step C is: add the carboxymethylcellulose hydrogen prepared in the step B into the activation solution for activation, and the activation time is 10 -30min, the temperature is 10-50°C, and then sealed and placed for use; the activation solution is one or a combination of hydrochloric acid, sulfuric acid, acetic acid, propionic acid.

Further, the preparation process of step D described in the preparation method of above-mentioned carboxymethylcellulose acetate propionate is:

1) Feeding: add the activated material to the reactor after filtering to remove part of the solvent;

2) Esterification: Slowly add the esterification agent into the reactor, heat and stir at a constant temperature to react;

3) Hydrolysis: add a hydrolyzate, the hydrolyzate is an aqueous solution of acetic acid, and stir and hydrolyze at a constant temperature for 60-180min;

4) Neutralization: After the hydrolysis is completed, the system is cooled and then added with a neutralizing solution to terminate the reaction, and the product is obtained by precipitation, washing and drying.

Further, the esterifying agent used in the step 2) of the above-mentioned preparation method of carboxymethyl cellulose acetate propionate includes the following components by weight: 1-5 parts of sulfuric acid and 10-50 parts of four A mixture of one or more of these substances: acetic acid, propionic acid, acetic anhydride, propionic anhydride. That is, the esterifying agent includes sulfuric acid and another substance, and the other substance is one or more of acetic acid, propionic acid, acetic anhydride, and propionic anhydride.

Further, the esterification agent described in the above-mentioned preparation method of carboxymethylcellulose acetate propionate includes the following weight components: 20-200 parts of acetic anhydride, 1000-4000 parts of propionic anhydride, and 1-5 parts of sulfuric acid.

Further, the constant temperature heating reaction process in the step 2) described in the preparation method of the above-mentioned carboxymethylcellulose acetate propionate is divided into two stages of low temperature and high temperature, wherein the reaction time of the low temperature stage is 60-180min, and the reaction temperature is 40 ±2°C; the reaction time in the high temperature stage is 60-180min, and the solution esterification reaction exotherms and heats up.

In the above preparation method of carboxymethylcellulose acetate propionate, the hydrolyzate used in step 3) is an aqueous solution of acetic acid, preferably the following component mixture in parts by weight: 50-100 parts of water and 50-100 parts of acetic acid.

In the preparation method of the above-mentioned carboxymethylcellulose acetate propionate, the neutralizing solution is an acid solution, and it is further preferred to proportion 20-120 parts by weight of magnesium acetate, 100-300 parts of acetic acid and 100-300 parts of water mixed solution.

The carboxymethyl cellulose acetate propionate prepared above is used as water-based paint leveling agent. Experiments have proved that the CMCAP prepared by the present invention can make the leveling of the water-based paint better than that of CMCAB when used as a water-based paint leveling agent.

It should be noted that the parts of each added component mentioned in the description are all parts by mass.

In summary, the carboxymethyl cellulose acetate propionate provided by the present invention can replace CMCAB for application in the coating field, and has better performance than CMCAB. The method provided by the invention has short production cycle, low production temperature, low raw material consumption, and greatly reduces the manufacturing cost of the operation process. Due to the strengthening of environmental protection awareness, the market demand for low-VOC water-based coatings is increasing, and the industry using water-based coatings is also gradually increasing. Increase, the application prospect of carboxymethylcellulose acetate propionate is broad, and the content of substituents can be adjusted to prepare different types of products, which are suitable for various fields and meet a wide range of market demands. Because the components and additives in the field of water-based paint are mostly monopolized by foreign companies, and its preparation method is rarely disclosed, so the water-based paint with good quality is expensive, and the performance of the water-based paint leveling agent developed by the present invention is better than that of CMCAB, and the present invention The production environment of the invention is friendly, and it is extremely beneficial for widespread promotion, so the invention has very important significance for the domestic water-based paint industry.

detailed description

The present invention will be further described below in conjunction with specific embodiments. It should be noted that the embodiments described in the present invention are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. The percentages without special instructions in the embodiments are all mass percentages.

The acidizing solution used in embodiment 1 and embodiment 2 is sulfuric acid with a mass fraction of 20%, and the acidizing solution used in embodiment 3 and embodiment 4 is hydrochloric acid with a mass fraction of 10%. The activation solution used in Example 1 and Example 2 is propionic acid, and the activation solution used in Example 3 and Example 4 is a mixture of acetic acid and propionic acid in a mass ratio of 1:4. The esterifying agent used in Examples 1 to 4 is a mixture of acetic anhydride, propionic anhydride, and sulfuric acid in a mass ratio of 100:4000:3, wherein the sulfuric acid is concentrated sulfuric acid with a mass fraction of 98%.

Example 1

(1) Preparation of CMC: The performance indicators of the prepared CMC are: degree of substitution DS=0.3, moisture content 20%, purity 98%. Disperse 100g of refined cotton in isopropanol/water solution, wherein 1950g of isopropanol and 50g of water. After removing the air in the reactor, pass inert gas. Then add 300g of 20% aqueous sodium hydroxide solution at 20°C for 120 minutes of alkalization; The duration is 60 minutes, then the temperature is raised to 60°C for etherification for 60 minutes, and then the temperature is raised to 80°C for 150 minutes for etherification. Add 30% hydrochloric acid aqueous solution for neutralization, use 80% alcohol/water solution to wash twice, dry, pulverize, and set aside. The 80% alcohol/water solution described here is the ethanol water solution with a mass fraction of 80%, and the following are similar.

(2) Preparation of CMC-H: Submerge 100g of CMC in the acidification solution for acidification. The acidification temperature is 25°C and the acidification time is 150min. Wash with pure water three times to remove excess acid, filter and set aside.

(3) Preparation of active CMC-H: immerse 100g of CMC-H in 1000g of activation solution for activation, the activation time is 20min, the activation temperature is 30°C, then filtered, sealed and placed for use.

(4) Preparation of CMCAP: After adding the active material prepared in (3) to the reactor, add 1063g of esterifying agent prepared by sulfuric acid and acetic acid according to the mass ratio of 1:10, add the esterifying agent and keep warm for 15min, then heat up to 40 Keep warm at ℃ for 100 minutes, then continue to keep warm for 100 minutes, then add 100g of 40% acetic acid aqueous solution, react at a constant temperature of 65℃ for 100 minutes, and finally add 50g of neutralizing solution, which is prepared by mass ratio of magnesium acetate, acetic acid and water at a ratio of 1:10:10 of the mixture. A large amount of water was added into the reactor to precipitate the product, and washed 3 times with a large amount of water to obtain pure CMCAP.

The performance index of the obtained CMCAP: carboxymethyl substitution degree 0.3, apparent acetyl content 43.82%, acetyl content 6.57%, propionyl content 38.77%, acidity 50mg/g KOH.

Example 2

(1) Preparation of CMC: The performance index of the prepared CMC is: DS=0.3, moisture content 20%, purity 98%. Disperse 100g of refined cotton in isopropanol/water solution, wherein 1950g of isopropanol and 50g of water. After removing the air in the reactor, pass inert gas. Then add 300g of 20% aqueous sodium hydroxide solution at 20°C for 120 minutes of alkalization; The duration is 60 minutes, then the temperature is raised to 60°C for etherification for 60 minutes, and then the temperature is raised to 80°C for 150 minutes for etherification. Add 30% acetic acid aqueous solution for neutralization, use 80% alcohol/water solution to wash 3 times, dry, pulverize, and set aside.

(2) Preparation of CMC-H: Submerge 100g of CMC in the acidification solution for acidification. The acidification temperature is 25°C and the acidification time is 150min. Wash with pure water three times to remove excess acid, filter and set aside.

(3) Preparation of active CMC-H: immerse 100g of CMC-H in 1000g of activation solution for activation, the activation time is 20min, the activation temperature is 30°C, then filtered, sealed and placed for use.

(4) Preparation of CMCAP: After the active matter prepared in (3) is added to the reactor, add sulfuric acid and acetic anhydride according to the mass ratio of 1:25 esterifying agent 1304g prepared, after adding the esterifying agent, keep warm for 15min, then heat up to Incubate at 40°C for 100 minutes, then continue to insulate for 100 minutes, then add 150g of acetic acid aqueous solution with a mass fraction of 50%, react at a constant temperature of 65°C for 100min, and finally add 60g of neutralizing solution, which is magnesium acetate, acetic acid and water in a mass ratio of 1: 1:1 prepared mixture. A large amount of water was added into the reactor to precipitate the product, and washed 4 times with a large amount of water to obtain pure CMCAP.

The performance index of the obtained CMCAP: carboxymethyl substitution degree 0.5, apparent acetyl content 40.75%, acetyl content 7.61%, propionyl content 40.93%, acidity 45mg/g KOH.

Example 3

(1) Preparation of CMC: The performance index of the prepared CMC is: DS=0.3, moisture content 20%, purity 98%. Disperse 100g of refined cotton in isopropanol/water solution, wherein 1950g of isopropanol and 50g of water. After removing the air in the reactor, pass inert gas. Then add 300g of 20% aqueous sodium hydroxide solution at 20°C for 120 minutes of alkalization; The duration is 60 minutes, then the temperature is raised to 60°C for etherification for 60 minutes, and then the temperature is raised to 80°C for 150 minutes for etherification. Add 30% hydrochloric acid aqueous solution for neutralization, use 80% alcohol/water solution to wash 3 times, dry, pulverize, and set aside.

(2) Preparation of CMC-H: Submerge 100g of CMC in the acidification solution for acidification. The acidification temperature is 25°C and the acidification time is 150min. Wash with pure water three times to remove excess acid, filter and set aside.

(3) Preparation of active CMC-H: immerse 100g of CMC-H in 1000g of activation solution for activation, the activation time is 10min, and the activation temperature is 30°C, then filtered, sealed and placed for use.

(4) Preparation of CMCAP: After the active substance prepared in (3) is added to the reactor, add sulfuric acid and propionic acid according to the mass ratio of 1:50 prepared esterification agent 1525g, after adding the esterification solution, keep warm for 15min, then heat up to Keep warm at 40°C for 100 minutes, then continue to keep warm for 100 minutes, then add 180g of 60% acetic acid aqueous solution, react at a constant temperature of 65°C for 100 minutes, and finally add 80g of neutralizing solution, which is magnesium acetate, acetic acid and water in a mass ratio of 1:4:6 Prepared mixture. A large amount of water was added into the reactor to precipitate the product, and washed 3 times with a large amount of water to obtain pure CMCAP.

The performance index of the obtained CMCAP: carboxymethyl substitution degree 0.4, apparent acetyl content 42.05%, acetyl content 9.80%, propionyl content 42.75%, acidity 43mg/g KOH.

Example 4

(1) Preparation of CMC: The performance index of the prepared CMC is: DS=0.3, moisture content 20%, purity 98%. Disperse 100g of refined cotton in isopropanol/water solution, wherein 1950g of isopropanol and 50g of water. After removing the air in the reactor, pass inert gas. Then add 300g of 20% aqueous sodium hydroxide solution at 20°C for 120 minutes of alkalization; The duration is 60 minutes, then the temperature is raised to 60°C for etherification for 60 minutes, and then the temperature is raised to 80°C for 150 minutes for etherification. Add 30% acetic acid aqueous solution for neutralization, use 80% alcohol/water solution to wash twice, dry, pulverize, and set aside.

(2) Preparation of CMC-H: Submerge 100g of CMC in the acidification solution for acidification. The acidification temperature is 25°C and the acidification time is 150min. Wash with pure water three times to remove excess acid, filter and set aside.

(3) Preparation of active CMC-H: immerse 100g of CMC-H in 1000g of activation solution for activation, the activation time is 10min, and the activation temperature is 30°C, then filtered, sealed and placed for use.

(4) Preparation of CMCAP: After adding the active matter prepared in (3) to the reactor, add sulfuric acid and propionic acid according to the mass ratio of 1:2 esterifying agent 1755g prepared, after adding the esterifying agent, keep warm for 15min, then heat up to Keep warm at 40°C for 100min, then continue to keep warm for 100min, then add 200g of 35% acetic acid aqueous solution, react at a constant temperature of 65°C for 100min, and finally add 100g of neutralizing solution, which is magnesium acetate, acetic acid and water in a mass ratio of 1:3:2 Prepared mixture. A large amount of water was added into the reactor to precipitate the product, and washed 4 times with a large amount of water to obtain pure CMCAP.

The performance index of the obtained CMCAP: carboxymethyl substitution degree 0.2, apparent acetyl content 41.04%, acetyl content 10.71%, propionyl content 45.75%, acidity 47mg/g KOH.

When the CMCAP prepared in Examples 1 to 3 is prepared as a coating with the same acidity value as the CMCAB with the same formula, the coating performance is the same.

CMCAP and CMCAB prepared in Example 1 to Example 4 are mixed with butyl composite solvent, resin-based solution, dimethylethanolamine, deionized water, and aluminum powder of the same proportion respectively to prepare an aqueous dispersion. After the layer is cured, use the wavelength scanning method to evaluate the leveling property through the long-wave LW, short-wave and R value scanned by the orange peel meter. The test results are shown in Table 1.

The leveling test data of different sample preparation aqueous dispersions of table 1

Classification Thickness/mm long wave shortwave CMCAB 92 4.8 15.6 Example 1 94 4.2 12.6 Example 2 92 4.3 12.7 Example 3 93 4.5 12.5 Example 4 94 4.1 12.6

From the test results shown in Table 1, it can be seen that when the thickness of the water-based paint (that is, the water dispersion) is equivalent, the leveling property of the water-based paint prepared by CMCAP is obviously better than that of CMCAB.

Claims (10)

1. a preparation method of carboxymethyl cellulose acetate propionate, is characterized in that: comprise steps: A. prepare low-substituted sodium carboxymethylcellulose; B. Prepare carboxymethyl cellulose hydrogen after acidifying the low-substituted sodium carboxymethyl cellulose; C. Activation of carboxymethyl cellulose hydrogen; D. Esterifying the activated carboxymethyl cellulose with hydrogen to prepare carboxymethyl cellulose acetate propionate. 2. the preparation method of carboxymethylcellulose acetate propionate according to claim 1 is characterized in that: the preparation process of low-substituted sodium carboxymethylcellulose in described step A is as follows: a. Feeding: add 100 parts of cellulose powder, 1000-3000 parts of organic solvent, and 30-60 parts of water into the reactor, wherein the organic solvent is one or more combinations of ethanol, propanol, isopropanol and acetone; b. Gas protection: After feeding is completed, inert gas is introduced, and inert gas is introduced after removing the air in the reactor; c. Alkalinization: add 100-500 parts of sodium hydroxide aqueous solution with a mass fraction of 20-35%, and alkalize at a constant temperature of 10-40°C for 40-120min; d. Etherification: adjust the system temperature to 10-20°C, and add 100-500 parts of etherification agent by spraying evenly within 30-120 minutes. The etherification agent is 50%-80% chloroacetic acid organic solvent solution, of which organic The solvent is one of ethanol, propanol, isopropanol, acetone or a combination thereof, the temperature is raised to 30-60°C for constant temperature etherification for 30-180 minutes, and then the temperature is controlled at 50-80°C to continue etherification for 30-180 minutes; e. Neutralization, washing and drying: add 10-50 parts of acid to terminate the reaction, and the crude product is preliminarily removed from the organic solvent in the material through a stripping process, and then washed with ethanol/water solution to remove reaction by-products and impurities, dried and pulverized; The acid component of reaction is one or more combination in acetic acid, hydrochloric acid, sulfuric acid; The above-mentioned parts are parts by mass. 3. according to the preparation method of claim 1 and 2 described carboxymethyl cellulose acetate propionate, it is characterized in that: the preparation process of described step B is: with 100 parts of low-substituted carboxymethyl carboxymethyl prepared by step A The base cellulose is added to the reactor containing 300-1000 parts of acidification solution, the acidification time is 20-120min, the acidification temperature is 10-50°C, and the acidification is completed and washed with water for 3-5 times; the above-mentioned parts are parts by mass. 4. the preparation method of carboxymethyl cellulose acetate propionate according to claim 3 is characterized in that: described acidification liquid is the aqueous solution of one or more combinations in hydrochloric acid, sulfuric acid, acetic acid, propionic acid, Its mass fraction is 10-30%. 5. the preparation method of carboxymethyl cellulose acetate propionate according to claim 1 is characterized in that: the preparation process of described step C is: the prepared carboxymethyl cellulose hydrogen of step B is added activation solution Activation in 10-30min at a temperature of 10-50°C, then sealed and placed for use; The activation solution is one or a combination of hydrochloric acid, sulfuric acid, acetic acid and propionic acid. 6. the preparation method of carboxymethylcellulose acetate propionate according to claim 1 is characterized in that: the preparation process of described step D is: 1) Feeding: add the activated material to the reactor after filtering to remove part of the solvent; 2) Esterification: Slowly add the esterification agent into the reactor, heat and stir at a constant temperature to react; 3) Hydrolysis: add a hydrolyzate, the hydrolyzate is an aqueous solution of acetic acid, and stir and hydrolyze at a constant temperature for 60-180min; 4) Neutralization: After the hydrolysis is completed, the system is cooled and then added with a neutralizing solution to terminate the reaction, and the product is obtained by precipitation, washing and drying. 7. the preparation method of carboxymethyl cellulose acetate propionate according to claim 6 is characterized in that: described step 2) in the esterifying agent used comprises following parts by weight: 1-5 parts of sulfuric acid Mixed with 10-50 parts of one or more of the following four substances: acetic acid, propionic acid, acetic anhydride, propionic anhydride. 8. the preparation method of carboxymethyl cellulose acetate propionate according to claim 6 is characterized in that: described step 2) in constant temperature heating reaction process, be divided into low temperature and high temperature two stages, wherein low temperature stage reaction time The reaction time is 60-180min, and the reaction temperature is 40±2°C; the reaction time in the high temperature stage is 60-180min, and the solution esterification reaction exotherms and heats up. 9. A carboxymethyl cellulose acetate propionate, characterized in that: it is prepared according to any one of the preparation methods in claims 1 to 8. 10. the purposes of carboxymethylcellulose acetate propionate as claimed in claim 9 is characterized in that: as water-based paint leveling agent.