Method for reducing gel water insoluble substances in carboxymethyl cellulose

Abstract

The invention relates to the technical field of cellulose ether, and provides a method for reducing gel water insoluble substances in carboxymethyl cellulose. The method comprises the following steps: mixing alkali metal hydroxide, an organic solvent-water mixed solvent, a cellulose raw material and an additive, and carrying out alkalization reaction to obtain alkalization reaction liquid; the additive comprises a polyhydric alcohol; and mixing the alkalization reaction solution with an etherifying agent for etherification reaction to obtain the carboxymethyl cellulose. According to the method, the additive is added in the process of preparing the carboxymethyl cellulose by the slurry method, and a stable interface is formed among the cellulose, the alkali and the etherifying agent by utilizing the additive, so that the reaction uniformity is improved, and the content of gel water insoluble substances in the carboxymethyl cellulose is effectively reduced. The result of the embodiment shows that the content of gel particles in the product can be reduced from 49 to 23 by 53% when the carboxymethyl cellulose is prepared by adopting the method disclosed by the invention.

Description

Technical Field

[0001] The invention relates to the technical field of cellulose ethers, in particular to a method for reducing water-insoluble gel matter in carboxymethyl cellulose. Background Art

[0002] Carboxymethyl cellulose (CMC) is an important water-soluble anionic cellulose ether, widely used in food, medicine, toothpaste, batteries, daily chemicals, papermaking, textiles, construction and other industries as a thickener, dispersant, stabilizer, emulsifier, film-forming agent, water-retaining agent, etc.

[0003] The amount of water-insoluble gel in carboxymethyl cellulose is a key quality indicator. This refers to the gel-like insoluble matter that remains after carboxymethyl cellulose is dissolved in water and cannot be removed by filtration or centrifugation. The presence of water-insoluble gel can significantly reduce the quality and performance of carboxymethyl cellulose. For example, in the food industry, water-insoluble gel reduces the transparency and taste of food systems. In the pharmaceutical industry, it can reduce the stability of drug formulations, affecting drug release and absorption. In the daily chemical industry, it can affect product texture and stability.

[0004] In recent years, the new energy industry has developed extremely rapidly. Carboxymethyl cellulose can be used as a negative electrode additive in lithium batteries. The gel water-insoluble matter of carboxymethyl cellulose will have a significant impact on battery performance: the gel water-insoluble matter will cause the solid particles of the battery slurry to be unevenly distributed, forming agglomerates, resulting in uneven coating, affecting the quality and consistency of the electrode sheets. In summary, the gel water-insoluble matter content of carboxymethyl cellulose has a great impact on the battery, and will also lead to a decrease in the yield of battery electrodes and an increase in costs. Therefore, reducing the gel water-insoluble matter content in carboxymethyl cellulose will help improve its application performance and processing performance in batteries and reduce production costs.

[0005] At present, the common production process of carboxymethyl cellulose is the solvent method, that is, cellulose and alkali are reacted with organic solvents to form alkali fibers, which are then etherified. According to the amount of solvent used, it is divided into two types: kneading method and slurry method. Compared with the kneading method, the slurry method can significantly improve the dispersibility of cellulose and reduce local reaction imbalances due to the higher amount of solvent used. Therefore, it is more commonly used in scenarios with high requirements for product purity and solubility. Although the amount of solvent used in the slurry method is higher, since cellulose is a relatively stable natural high molecular polymer and cannot be dissolved in it, the reaction is still a solid-liquid two-phase reaction, and the reaction system itself still has many inhomogeneities, which is also the core reason for the formation of water-insoluble gel.

[0006] Currently, two approaches are commonly used in the field to reduce the amount of water-insoluble matter in gels: one is to select high-purity cellulose raw materials to reduce impurity interference; the other is to increase the amount of etherifying agent to increase the degree of substitution (DS) and reduce insoluble matter by improving overall water solubility. However, this leads to increased reagent consumption and reaction costs. Moreover, neither of these methods can improve the uniformity of the reaction process and cannot fundamentally reduce the formation of water-insoluble matter in gels, resulting in limited reduction effects. Summary of the Invention

[0007] In view of this, the present invention provides a method for reducing the amount of water-insoluble gel in carboxymethyl cellulose. The present invention improves the uniformity of the reaction during the preparation of carboxymethyl cellulose by adding additives, thereby effectively and fundamentally reducing the amount of water-insoluble gel in carboxymethyl cellulose.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] A method for reducing water-insoluble matter in gel in carboxymethyl cellulose comprises the following steps:

[0010] An alkali metal hydroxide, an organic solvent-water mixed solvent, a cellulose raw material and an additive are mixed to perform an alkalization reaction to obtain an alkalization reaction liquid; the additive includes a polyol; and the mass ratio of the cellulose raw material to the additive is 12:1-4;

[0011] The alkalization reaction liquid and the etherifying agent are mixed to carry out etherification reaction to obtain carboxymethyl cellulose.

[0012] Preferably, the polyol includes one or more of small molecule polyols, polyether polyols and polyvinyl alcohol; the small molecule polyol includes one or more of ethylene glycol, glycerol and pentaerythritol; the polyether polyol includes polyethylene glycol.

[0013] Preferably, the cellulose raw material includes one or more of cotton powder, straw, wood fiber and bamboo fiber.

[0014] Preferably, the alkali metal hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; the mass ratio of the cellulose raw material to the alkali metal hydroxide is 15:4-16;

[0015] The organic solvent in the organic solvent-water mixed solvent includes one or more of alcohol, acetone and toluene; the mass fraction of the organic solvent in the organic solvent-water mixed solvent is 42.5-99%; and the mass ratio of the cellulose raw material to the organic solvent-water mixed solvent is 3:20-80.

[0016] Preferably, the alkalization reaction is carried out at a temperature of 10 to 40° C. and for a time of 30 to 180 minutes.

[0017] Preferably, the etherifying agent includes one or more of chloroacetic acid, chloroacetate and chloroacetate ester.

[0018] Preferably, the mass ratio of the cellulose raw material to the etherifying agent is 60:10.5-90.

[0019] Preferably, the temperature of the etherification reaction is 50-80° C., and the time is 45-180 min.

[0020] Preferably, after the etherification reaction, the product liquid is subjected to post-treatment, and the post-treatment comprises: neutralizing the product liquid with acid, washing and solid-liquid separation in sequence to obtain a solid product, and drying and crushing the solid product to obtain carboxymethyl cellulose.

[0021] Preferably, the degree of substitution of the carboxymethyl cellulose is 0.6 to 1.8.

[0022] The present invention provides a method for reducing water-insoluble gel matter in carboxymethyl cellulose, comprising the following steps: mixing an alkali metal hydroxide, an organic solvent-water mixed solvent, a cellulose raw material, and an additive to conduct an alkalization reaction to obtain an alkalization reaction solution; the additive comprises a polyol; the mass ratio of the cellulose raw material to the additive is 12:1 to 4; and mixing the alkalization reaction solution with an etherifying agent to conduct an etherification reaction to obtain carboxymethyl cellulose. The present invention incorporates the additive during the preparation of the carboxymethyl cellulose. The additive forms a hydrophilic layer on the cellulose surface, uniformly dispersing the cellulose in the solvent system and ensuring sufficient contact between the cellulose, alkali, and etherifying agent, thereby improving the uniformity of the alkalization and etherification reactions. Furthermore, the additive itself has high chemical stability and does not participate in or interfere with the etherification reaction. In summary, the present invention innovatively proposes improving reaction uniformity by incorporating an additive, thereby effectively reducing the content of water-insoluble gel matter in carboxymethyl cellulose. Experimental results show that the gel particle content in the carboxymethyl cellulose produced using the method of the present invention can be reduced from 49 to 23 particles, a 53% reduction. DETAILED DESCRIPTION

[0023] The present invention provides a method for reducing water-insoluble matter in gel in carboxymethyl cellulose, comprising the following steps:

[0024] An alkali metal hydroxide, an organic solvent-water mixed solvent, a cellulose raw material and an additive are mixed to perform an alkalization reaction to obtain an alkalization reaction liquid; the additive includes a polyol; and the mass ratio of the cellulose raw material to the additive is 12:1-4;

[0025] The alkalization reaction liquid and the etherifying agent are mixed to carry out etherification reaction to obtain carboxymethyl cellulose.

[0026] The present invention mixes an alkali metal hydroxide, an organic solvent-water mixed solvent, a cellulose raw material and an additive to carry out an alkalization reaction to obtain alkali cellulose. In the present invention, the additive includes a polyol; the polyol preferably includes one or more of a small molecule polyol, a polyether polyol and a polyvinyl alcohol; the small molecule polyol preferably includes one or more of ethylene glycol, glycerol and pentaerythritol; the polyether polyol preferably includes polyethylene glycol; the polyethylene glycol is preferably polyethylene glycol 2000, and the polyvinyl alcohol is preferably polyvinyl alcohol 17-88; in a specific embodiment of the present invention, the additive preferably includes one or more of ethylene glycol, glycerol, pentaerythritol, polyethylene glycol and polyvinyl alcohol; the cellulose raw material preferably includes cotton powder, straw, wood fiber, etc. one or more of fiber and bamboo fiber; the alkali metal hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide, more preferably sodium hydroxide; the organic solvent in the organic solvent-water mixed solvent preferably includes one or more of alcohol, acetone and toluene; the alcohol preferably includes ethanol, methanol, isopropanol and tert-butanol; in a specific embodiment of the present invention, the organic solvent-water mixed solvent is preferably an isopropanol-water solution; the mass fraction of the organic solvent in the organic solvent-water mixed solvent is preferably 42.5-99%, specifically 45%, 55%, 80%, 85% or 90%.

[0027] In the present invention, the mass ratio of the cellulose raw material and the additive is 12:1 to 4, specifically 12:1, 12:2, 12:3 or 12:4; the present invention controls the amount of the cellulose raw material and the additive within the above range, so that the additive can fully react with the cellulose, alkali and etherifying agent to form a stable interface, thereby improving the uniformity of the alkalization reaction and the etherification reaction.

[0028] In the present invention, the mass ratio of the cellulose raw material and the organic solvent-water mixed solvent is preferably 3:20 to 80, specifically 3:40, 3:60 or 3:70; the present invention preferably controls the mass ratio of the cellulose raw material and the organic solvent-water mixed solvent within the above range, which can improve the dispersibility of the cellulose raw material and further improve the uniformity of the reaction.

[0029] In the present invention, the mass ratio of the cellulose raw material to sodium hydroxide is preferably 15:4-16, specifically 15:6, 15:8, 15:10 or 15:12.

[0030] In the present invention, the alkalization reaction temperature is preferably 10-40°C, specifically 10°C, 20°C, 30°C, or 40°C. The alkalization reaction time is preferably 30-180 minutes, specifically 60 minutes, 80 minutes, 100 minutes, 120 minutes, or 160 minutes. The alkalization reaction is preferably carried out under a protective atmosphere, preferably nitrogen. During the alkalization reaction, the cellulose raw material and the alkali metal hydroxide react to produce alkali cellulose. After the alkalization reaction is completed, the resulting reaction solution can be directly used for the next reaction without any further treatment.

[0031] After obtaining the alkalized reaction solution, the present invention mixes the alkalized reaction solution with an etherifying agent to carry out an etherification reaction to obtain carboxymethyl cellulose. In the present invention, the etherifying agent preferably includes one or more of chloroacetic acid, chloroacetate salts, and chloroacetic acid esters; the chloroacetate salts are preferably sodium chloroacetate; the chloroacetic acid esters are preferably one or more of methyl chloroacetate, ethyl chloroacetate, and isopropyl chloroacetate; in a specific embodiment of the present invention, the etherifying agent is chloroacetic acid.

[0032] In the present invention, the mass ratio of the cellulose raw material to the etherifying agent is preferably 60:10.5 to 90, specifically 60:15, 60:30, 60:32.5 or 60:50. In a specific embodiment of the present invention, the etherifying agent is preferably used in the form of an etherifying agent solution. The solvent of the etherifying agent solution is preferably the same as the organic solvent used in the reaction system, more preferably isopropanol. The concentration of the etherifying agent in the etherifying agent solution is preferably 25 to 60 wt%, specifically 50 wt%.

[0033] In the present invention, the temperature of the etherification reaction is preferably 50-80° C., specifically 60° C. or 70° C., and the time of the etherification reaction is preferably 45-180 min, specifically 90 min or 120 min.

[0034] After the etherification reaction, the present invention preferably further comprises post-processing the product liquid. The post-processing comprises: neutralizing the product liquid with an acid, washing it, and performing solid-liquid separation in sequence to obtain a solid product, and drying and crushing the solid product to obtain carboxymethyl cellulose. The acid used for the neutralization is preferably hydrochloric acid.

[0035] In the present invention, the degree of substitution of the carboxymethyl cellulose is preferably 0.6 to 1.8, more preferably 0.9 to 0.93, and specifically may be 0.92 or 0.93.

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] In the following examples and comparative examples:

[0038] The degree of substitution of carboxymethyl cellulose was determined using the national standard ash-alkali method (GB 1886.232-2016);

[0039] Determination of gel water-insoluble matter (gel particles): Take 5g of sample and prepare a 1wt% aqueous solution. Then evenly apply the solution to a 20cm×60cm transparent PE board. Select the area with the most gel particles on the PE board (5×8cm 2 ) and manually counted to confirm the number of gel particles.

[0040] In the following examples and comparative examples, one portion is 1 g.

[0041] Example 1

[0042] Under stirring conditions, 32 parts of sodium hydroxide were added to 800 parts of an isopropyl alcohol-water solution (isopropyl alcohol content: 85 wt%), followed by the addition of 60 parts of cotton powder and 10 parts of polyethylene glycol 2000. The reaction apparatus was evacuated and filled with nitrogen, followed by an alkalization reaction at 20° C. for 120 minutes, and then 75 parts of a 50 wt% chloroacetic acid isopropyl alcohol solution was added. The temperature was raised to 60° C. and the reaction was carried out for 90 minutes. After the reaction was completed, the solution was neutralized with hydrochloric acid, washed, centrifuged, dried, and pulverized to obtain carboxymethyl cellulose. The degree of substitution was found to be 0.92, and the number of gel particles was 24.

[0043] Example 2

[0044] Under stirring conditions, 32 parts of sodium hydroxide are added to 800 parts of an isopropyl alcohol-water solution (isopropyl alcohol content is 85 wt%), followed by the addition of 60 parts of cotton powder and 10 parts of polyvinyl alcohol 17-88. The reaction apparatus is evacuated and filled with nitrogen, followed by an alkalization reaction at 20° C. for 120 minutes, followed by the addition of 75 parts of a 50 wt% chloroacetic acid isopropyl alcohol solution, the temperature is raised to 60° C., and the reaction is carried out for 90 minutes. After the reaction is completed, the solution is neutralized with hydrochloric acid, washed, centrifuged, dried, and pulverized to obtain carboxymethyl cellulose. The degree of substitution is 0.92, and the number of gel particles is 26.

[0045] Example 3

[0046] Under stirring conditions, 32 parts of sodium hydroxide were added to 800 parts of an isopropyl alcohol-water solution (isopropyl alcohol content: 85 wt%), followed by the addition of 60 parts of cotton powder and 15 parts of polyethylene glycol 2000. The reaction apparatus was evacuated and filled with nitrogen, followed by an alkalization reaction at 20° C. for 120 minutes, and then 75 parts of a 50 wt% chloroacetic acid isopropyl alcohol solution was added. The temperature was raised to 60° C. and the reaction was carried out for 90 minutes. After the reaction was completed, the solution was neutralized with hydrochloric acid, washed, centrifuged, dried, and pulverized to obtain carboxymethyl cellulose. The degree of substitution was found to be 0.93, and the number of gel particles was 23.

[0047] Example 4

[0048] Under stirring conditions, 32 parts of sodium hydroxide were added to 800 parts of an isopropyl alcohol-water solution (isopropyl alcohol content: 85 wt%), followed by the addition of 60 parts of cotton powder and 10 parts of ethylene glycol. The reaction apparatus was evacuated and filled with nitrogen, followed by an alkalization reaction at 20° C. for 120 minutes, followed by the addition of 75 parts of a 50 wt% chloroacetic acid isopropyl alcohol solution, the temperature was raised to 60° C., and the reaction was carried out for 90 minutes. After the reaction was completed, the solution was neutralized with hydrochloric acid, washed, centrifuged, dried, and pulverized to obtain carboxymethyl cellulose. The degree of substitution was found to be 0.92, and the number of gel particles was 29.

[0049] Example 5

[0050] Under stirring conditions, 32 parts of sodium hydroxide are added to 800 parts of an isopropyl alcohol-water solution (isopropyl alcohol content is 85 wt%), followed by the addition of 60 parts of cotton powder and 10 parts of glycerol. The reaction apparatus is evacuated and filled with nitrogen, followed by an alkalization reaction at 20° C. for 120 minutes, followed by the addition of 75 parts of a 50 wt% chloroacetic acid isopropyl alcohol solution, the temperature is raised to 60° C., and the reaction is carried out for 90 minutes. After the reaction is completed, the solution is neutralized with hydrochloric acid, washed, centrifuged, dried, and pulverized to obtain carboxymethyl cellulose. The degree of substitution is detected to be 0.91, and the number of gel particles is 23.

[0051] Example 6

[0052] Under stirring conditions, 32 parts of sodium hydroxide were added to 800 parts of an isopropyl alcohol-water solution (isopropyl alcohol content: 85 wt%), followed by the addition of 60 parts of cotton powder and 10 parts of pentaerythritol. The reaction apparatus was evacuated and filled with nitrogen, followed by an alkalization reaction at 20° C. for 120 minutes, and then 75 parts of a 50 wt% chloroacetic acid isopropyl alcohol solution was added. The temperature was raised to 60° C. and the reaction was carried out for 90 minutes. After the reaction was completed, the solution was neutralized with hydrochloric acid, washed, centrifuged, dried, and pulverized to obtain carboxymethyl cellulose. The degree of substitution was found to be 0.92, and the number of gel particles was 25.

[0053] Comparative Example 1

[0054] Under stirring conditions, 32 parts of sodium hydroxide were added to 800 parts of an isopropyl alcohol-water solution (isopropyl alcohol content: 85 wt%), and then 60 parts of cotton powder were added to the reaction apparatus, which was evacuated and filled with nitrogen. The reaction was then alkalized at 20° C. for 120 minutes, and then 75 parts of a 50 wt% chloroacetic acid isopropyl alcohol solution was added. The temperature was raised to 60° C. and the reaction was carried out for 90 minutes. After the reaction was completed, the solution was neutralized with hydrochloric acid, and then washed, centrifuged, dried, and pulverized to obtain carboxymethyl cellulose. The degree of substitution was determined to be 0.91, and the number of gel particles was 49.

[0055] According to the results of Comparative Example 1, it can be seen that after omitting the additive, the water-insoluble content of the obtained carboxymethyl cellulose gel is significantly increased.

[0056] Comparative Example 2

[0057] Under stirring conditions, 32 parts of sodium hydroxide were added to 800 parts of an isopropyl alcohol-water solution (isopropyl alcohol content: 85 wt%), followed by the addition of 60 parts of cotton powder and 10 parts of cetyltrimethylammonium bromide. The reaction apparatus was evacuated and filled with nitrogen, followed by an alkalization reaction at 20° C. for 120 minutes. Subsequently, 75 parts of a 50 wt% chloroacetic acid isopropyl alcohol solution were added, the temperature was raised to 60° C., and the reaction was carried out for 90 minutes. After the reaction was completed, the solution was neutralized with hydrochloric acid, washed, centrifuged, dried, and pulverized to obtain carboxymethyl cellulose. The degree of substitution was determined to be 0.92, and the number of gel particles was 47.

[0058] According to the results of Comparative Example 2, when cetyltrimethylammonium bromide is used as an additive, the content of water-insoluble matter in the obtained carboxymethyl cellulose gel is relatively high, indicating that cetyltrimethylammonium bromide cannot improve the reaction uniformity and reduce the content of water-insoluble matter in the gel.

[0059] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for reducing the water-insoluble matter in gel of carboxymethyl cellulose, characterized in that: The following steps are involved: An alkali metal hydroxide, an organic solvent-water mixed solvent, a cellulose raw material and an additive are mixed to perform an alkalization reaction to obtain an alkalization reaction liquid; the additive includes a polyol; and the mass ratio of the cellulose raw material to the additive is 12:1-4; The alkalization reaction liquid and the etherifying agent are mixed to carry out etherification reaction to obtain carboxymethyl cellulose.

2. The method according to claim 1, characterized in that The polyol includes one or more of small molecule polyol, polyether polyol and polyvinyl alcohol; the small molecule polyol includes one or more of ethylene glycol, glycerol and pentaerythritol; the polyether polyol includes polyethylene glycol.

3. The method according to claim 1, characterized in that The cellulose raw material includes one or more of cotton powder, straw, wood fiber and bamboo fiber.

4. The method according to claim 1 or 3, characterized in that The alkali metal hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; the mass ratio of the cellulose raw material to the alkali metal hydroxide is 15:4-16; The organic solvent in the organic solvent-water mixed solvent includes one or more of alcohol, acetone and toluene; the mass fraction of the organic solvent in the organic solvent-water mixed solvent is 42.5-99%; and the mass ratio of the cellulose raw material to the organic solvent-water mixed solvent is 3:20-80.

5. The method according to claim 1, characterized in that The temperature of the alkalization reaction is 10-40° C., and the time is 30-180 minutes.

6. The method according to claim 1, characterized in that The etherifying agent includes one or more of chloroacetic acid, chloroacetate and chloroacetate ester.

7. The method according to claim 1 or 6, characterized in that The mass ratio of the cellulose raw material to the etherifying agent is 60:10.5-90.

8. The method according to claim 1 or 6, characterized in that The temperature of the etherification reaction is 50-80° C., and the time is 45-180 minutes.

9. The method according to claim 1, characterized in that After the etherification reaction, the product liquid is subjected to post-treatment, and the post-treatment includes: neutralizing the product liquid with acid, washing and solid-liquid separation in sequence to obtain a solid product, and drying and crushing the solid product to obtain carboxymethyl cellulose.

10. The method according to claim 1, characterized in that The degree of substitution of the carboxymethyl cellulose is 0.6 to 1.8.