CN1916027A

CN1916027A - Method for preparing carboxymethyl cellulose in high degree of substitution

Info

Publication number: CN1916027A
Application number: CN 200610078867
Authority: CN
Inventors: 邵自强; 李博; 杨斐霏; 王飞俊; 王文俊
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2006-05-11
Filing date: 2006-05-11
Publication date: 2007-02-21

Abstract

The invention provides a method for preparing ultra-high degree of substitution carboxymethyl cellulose ether by stage feeding. Cotton and wood cellulose are alkalized with 18% to 50% NaOH aqueous solution, and then in an organic solvent and under the protection of an inert gas, chloroacetate, chloroacetic acid or Carboxymethyl cellulose ether with a carboxymethyl molar substitution degree of not less than 2.0 is obtained through the etherification reaction of its sodium salt, followed by alkali and temperature rise for secondary etherification, and neutralization, washing and drying processes.

Description

Preparation method of carboxymethyl cellulose with ultrahigh substitution degree

One, the technical field

The invention belongs to the preparation and synthesis of carboxymethyl cellulose ether with ultrahigh substitution degree, and belongs to the technical field of polymer chemistry.

Second, background Art

The cellulose ether is a high molecular polymerobtained by chemically modifying, alkalizing and etherifying natural cellulose. The water-soluble cellulose ether has good properties of thickening, suspending, dispersing, film forming, bonding, colloid keeping, microorganism stability and the like, so the water-soluble cellulose ether is applied to industrial departments such as petroleum drilling, food, medicine, coating, building, daily chemical industry, ceramics, paper making, electronic departments and the like, and has wide application.

Carboxymethyl cellulose ether is the most important ionic cellulose ether, is an ionic cellulose ether obtained by alkalization, carboxymethylation, intermediate washing and purification of natural cellulose, is one of the most important water-soluble polymers in industry, and has extremely wide application in industry. The substitution degree of carboxymethyl cellulose ether sold in the current market is about 0.60-1.20. With the continuous expansion of application fields, various complex and deteriorated application environments require that carboxymethyl cellulose ether with higher degree of substitution and more uniform substitution is a common trend at home and abroad in a use environment with high temperature, low pH value and high salt content. The carboxymethyl cellulose with ultrahigh substitution degree has wider substitution degree and viscosity range, higher storage stability and thermal stability, better acid and alkali resistance and salt resistance, good rheological property, smaller thixotropy and the like, and can be better applied to various industries such as toothpaste, alkaline batteries, oil exploitation, reactive dye printing and dyeing slurry and the like.

The development of carboxymethyl cellulose with ultrahigh substitution degree begins in countries such as the United states and Japan in the eighties and ninety years of the last century, and patents U.S. Pat. No. 4,426,206 and U.S. Pat. No. 5,455,341 report methods for synthesizingcarboxymethyl cellulose with ultrahigh substitution degree in multiple steps, but more methods have complex processes and high energy consumption and have the defects of reduced polymerization degree and viscosity of products, high process cost and the like; in order to obtain a carboxymethyl cellulose product with moderate degree of polymerization and ultrahigh degree of substitution, the research on a reasonable reaction mechanism and a preparation process is very meaningful, and the carboxymethyl cellulose has very wide market and application prospects.

The invention belongs to a preparation method of carboxymethyl cellulose ether with ultrahigh substitution degree.

Third, the invention

The invention provides measures of stepwise continuous alkali addition, control of acid-base ratio of each reaction stage and the like, develops a method for etherification in the continuous alkali addition stage, does not need repeated cooling and heating steps, and can ensure that the product has higher etherification degree to obtain the carboxymethyl cellulose ether with ultrahigh substitution degree.

The synthesis of the carboxymethyl cellulose with ultrahigh substitution degree belongs to heterogeneous liquid-solid reaction, and is a process for realizing alkali addition and staged etherification reaction in situ after an inert organic solvent is alkalized. The following preparation processes are expressed in parts by weight unless otherwise specified:

under the reaction condition of 10-30 ℃, adding 200 parts of cellulose into 1600-3000 parts of organic solvent dissolved with a proper amount of 40% NaOH aqueous solution, and alkalizing the cellulose for 0.5-2 hours; slowly adding 800-1200 parts of 45-75% chloroacetic acid-organic solvent solution, then adding a proper amount of alkali, and adding 350-500 parts of total alkali in one-time alkalization; heating to 50-65 ℃ and keeping the temperature for 0.5-4 hours; then adding 350-450 parts of 35-45% NaOH aqueous solution, heating to 70-80 ℃, and keeping the temperature for reaction for 0.5-5 hours; neutralizing the solution with acid until the pH value is 7, centrifuging the solution, washing the solution with 70 to 80 percent aqueous alcohol solution, and drying the solution for 2 to 5 hours in a vacuum oven at the temperature of between 60 and 85 ℃.

The preparation principle of the highly substituted sodium carboxymethylcellulose can be represented by the following chemical reaction equation:

alkalization of cellulose to alkali cellulose:

conversion of chloroacetic acid to sodium chloroacetate:

conversion of alkali cellulose and sodium chloroacetate to:

neutralizing and washing:

here, x is a number less than 3 and greater than 2; n is the number of carboxymethyl groups substituted on each cellulose glucose ring, Cell- (ONa)_3-n(CH2COO^-Na⁺)_nAfter washing, the Cell becomes Cell- (OH)_3-n(OCH₂COO^-Na⁺)_n. In addition, the reaction system is alkaline, some side reactions are generated in the presence of water, and by-products such as sodium glycolate and glycolic acid are generated and expressed by chemical equationsComprises the following steps:

the control of the side reactions is key in the process of preparing the product with ultrahigh substitution degree, and on one hand, the side reactions consume alkali and etherifying agent, so that the etherification efficiency is reduced; on the other hand, sodium glycolate, sodium ethoxide and more salt impurities in the product cause difficulty in product purification, influence the service performance of the product, such as acid resistance, temperature resistance and salt resistance, and greatly reduce the predictability of the calculation amount of the neutralizing acid. The degree of the side reaction is firstly related to the amount of free (or free) alkali in the system, namely the excessive alkali which is not used for cellulose to form alkali cellulose, and the higher the amount of the free alkali is, the stronger the side reaction is; in addition, the side reaction is directly related to the water amount of the system. The water in the system is used for promoting the cellulose to be alkalized, but the excessive water can cause the generated alkali cellulose to be hydrolyzed to be increased, so that the amount of free alkali is increased, and the side reaction degree is increased. Therefore, in order to prepare the side reaction, alkali needs to be reasonably used, and the water quantity of the system is controlled at the same time, namely the concentration, the adding mode and the adding quantity of the alkali in the reaction process are controlled, so that the aim of fully alkalizing to generate more complete alkali cellulose is fulfilled. In addition, temperature has a direct influence on side reactions. The reasonable control of the temperature rise speed and the reaction temperature is beneficial to the uniform etherification of the cellulose, the etherification efficiency is improved, and the occurrence of side reactions is inhibited.

The organic solvent medium can be selected from isopropanol, n-propanol, n-butanol, isobutanol, tert-butanol, ethanol, toluene, etc., and any one of their aqueous mixed organic solvents; the etherifying agent may be selected from chloroacetic acid, sodium chloroacetate, etc.; the activating agent is any one of sodium hydroxide or potassium hydroxide or a mixture thereof.

Description of the drawings

FIG. 1: a flow chart of a preparation process of carboxymethyl cellulose with ultrahigh substitution degree.

Fifth, the detailed description

Example 1

Preparing 2300 parts of mixed solution from 450 parts of 40% NaOH aqueous solution and 1850 parts of isopropanol/toluene (85/15) under the reaction condition of 20 ℃, adding 200 parts of cellulose, and alkalizing for 45 minutes; slowly adding 1050 parts of 65% chloroacetic acid-isopropanol/toluene solution in 1 hour, stirring for 30 minutes, and then adding 690 parts of 40% alkali liquor, wherein the reaction temperature can not exceed 40 ℃ all the time; heating to 60 ℃ and keeping the temperature to react for 1.5 hours; and adding 425 parts of 40% NaOH aqueous solution, heating to 72-74 ℃, and keeping the temperature for reacting for 1.5 hours. Then, the mixture was neutralized with glacial acetic acid to PH 7, centrifuged, and the filter cake was washed once with 72% and 75% aqueous ethanol solutions, respectively, and dried in a vacuum oven at 80 ℃ for 4 hours to obtain a product.

Example 2

Under the reaction condition of 35 ℃, 500 parts of 35% NaOH aqueous solution and 2050 parts of n-butanol are prepared into 2550 parts of mixed solution, 200 parts of cellulose is added, and alkalization is carried out for 1 hour; slowly adding 950 parts of 70% chloroacetic acid-n-butanol solution within 70 minutes, stirring for 20 minutes, and then additionally adding 190 parts of NaOH solid, wherein the reaction temperature can not exceed 40 ℃ all the time; heating to 65 ℃ and keeping the temperature to react for 2 hours; adding 400 parts of 45% NaOH aqueous solution, heating to 75 ℃, and keeping the temperature for reaction for 1 hour. Then, the mixture was neutralized with glacial acetic acid to pH 7, centrifuged, and the cake was washed once with 79% and 82% aqueous methanol solutions and dried in a vacuum oven at 70 ℃ for 6 hours to obtain a product.

Example 3

Under the reaction condition of 10 ℃, 350 parts of 40% KOH aqueous solution and 1650 parts of isopropanol/ethanol (86/14) are prepared into 2000 parts of mixed solution, 200 parts of cellulose is added, and alkalization is carried out for 30 minutes; slowly adding 995 parts of 60% chloroacetic acid-propanol/ethanol solution in 50 minutes, stirring for 40 minutes, and then adding 750 parts of 45% alkali liquor in a supplementing manner until the reaction temperature can not exceed 40 ℃ all the time; heating to 55 ℃ and keeping the temperature to react for 3 hours; then adding 180 parts of KOH solid, heating to 70 ℃, and keeping the temperature for reaction for 2.5 hours. Then, the mixture was neutralized with glacial acetic acid to PH 7, centrifuged, and the filter cake was washed once with 70% and 78% aqueous acetone solutions, and dried in a vacuum oven at 85 ℃ for 2 hours to obtain a product.

Example 4

Preparing 2200 parts of mixed solution of 450 parts of 40% NaOH aqueous solution and 1850 parts of isopropanol under the reaction condition of 20 ℃, adding 200 parts of cellulose, and alkalizing for 45 minutes; slowly adding 1050 parts of 55% chloroacetic acid-isopropanol solution within 1 hour, stirring for 30 minutes, and then adding 690 parts of 40% alkali liquor, wherein the reaction temperature is not more than 40 ℃ all the time; heating to 60 ℃ and keeping the temperature to react for 1.5 hours; then 425 parts of 40% NaOH aqueous solution is added, the temperature is increased to 72-74 ℃, and the temperature is kept for reaction for 1.5 hours. Then, the mixture was neutralized with glacial acetic acid to PH 7, centrifuged, and the filter cake was washed once with 72% and 75% aqueous ethanol solutions, respectively, and dried in a vacuum oven at 80 ℃ for 4 hours to obtain a product.

Claims

1. The preparation method of ultra-high degree of substitution carboxymethyl cellulose ether: After the natural cellulose is alkalized by 18% to 50% NaOH aqueous solution, in an inert organic solvent medium, in a certain proportion and under the protection of an inert gas Under the conditions of heating and stirring, add chloroacetic acid or its compounds dissolved in an inert solvent for etherification, then add 30% to 50% NaOH aqueous solution and raise the temperature for secondary etherification, then neutralize, wash and dry dry to obtain carboxymethyl cellulose ether with a degree of substitution not lower than 2.0.

2. according to the described method of right 1, it is characterized in that adopting natural cotton, wood cellulose is raw material.

3. according to the described method of right 1, it is characterized in that alkalization, heating up and etherification process should be divided into two stages and carry out continuously at least.

4. The method according to claim 1, wherein the etherification agent can be selected from chloroacetic acid, sodium chloroacetate or chloroacetate etc. as the etherification agent.

5. The method according to claim 1, characterized in that the etherification should be carried out at a temperature of 50-70° C. for 1-5 hours for the first etherification, and the reaction should be carried out under nitrogen protection.

6. The method according to claim 1, characterized in that an appropriate amount of alkali should be added for secondary etherification, and the temperature should be raised to 70-80°C for 1-3 hours of etherification, and the reaction should be under nitrogen protection conduct.

7. The method according to claim 1, characterized in that the alkali-acid ratio range of the primary etherification reaction is 1.3-1.9, and the alkali-acid ratio range of the secondary etherification reaction is 2.0-2.3.

8. The method according to right 1, characterized in that the inert organic solvent medium can be selected from organic solvents such as isopropanol, n-propanol, n-butanol, isobutanol, tert-butanol, ethanol, toluene and its aqueous mixed organic solvent.

9. The method according to claim 1, characterized in that the temperature of the system is lowered to 40-55° C., and neutralized by adding a certain concentration of hydrochloric acid, acetic acid and other alcoholic aqueous solutions.

10. The method according to claim 1, wherein the detergent is methanol/water solution, ethanol/water solution, isopropanol/water solution, methanol/isopropanol/water solution, isopropanol/ethanol/water solution, etc. with a certain concentration.

11. according to the method described in right 1, its general formula of the synthesized ultra-high degree of substitution carboxymethyl cellulose ether is:

R=-OCH ₂ COONa or OH, the product is characterized in that the carboxymethyl molar substitution degree on the cellulose molecule can be controlled to be no less than 2.3.