Low-cost preparation method of sodium carboxymethyl cellulose

Abstract

The invention provides a low-cost preparation method of sodium carboxymethyl cellulose, and relates to the technical field of sodium carboxymethyl cellulose preparation. The method comprises the following steps: taking bamboo pulp, refined cotton and wood pulp as fiber raw materials, and carrying out alkalization, etherification and neutralization, the mass fraction of the bamboo pulp in the fiber raw material is 10-50%, the mass fraction of the wood pulp in the fiber raw material is 10-50%, and the mass fraction of the refined cotton in the fiber raw material is 10-50%; the alkali liquor needs to be pretreated before alkalization by using the alkali liquor, and the pretreatment steps are as follows: mixing ethanol, isopropanol, soft water and sodium hydrosulfite, adding a sodium hydroxide solution, heating to 70-80 DEG C, keeping the temperature for 30-50 minutes, cooling to 40-50 DEG C, keeping the temperature for 20-30 minutes, and finally cooling to room temperature, thereby completing the pretreatment to obtain the pretreated alkali liquor. According to the method, the production cost can be greatly reduced on the premise that the content of sodium carboxymethyl cellulose is relatively high and the product quality is not reduced, the product quality meets the market demand, and market popularization and application are facilitated.

Description

Technical Field

[0001] The present application relates to the technical field of sodium carboxymethyl cellulose preparation, and in particular to a low-cost preparation method of sodium carboxymethyl cellulose. Background Art

[0002] Carboxymethylcellulose (CMC) is a water-soluble cellulose ether obtained from natural cellulose through chemical modification processes such as alkalization, etherification, neutralization, and washing and centrifugation. Due to the poor water solubility of carboxymethylcellulose acid, it is typically prepared as a sodium salt for better application. Currently, the raw materials for producing sodium carboxymethylcellulose on the market mainly include refined cotton (cotton linters) and wood pulp or bamboo pulp. Preparation methods mainly include aqueous and solvent methods.

[0003] Chinese patent CN118580378A discloses a method for preparing carboxymethyl cellulose. The method comprises the following steps: first, acidifying etherified bamboo cellulose fiber with an acid solution to convert the sodium carboxymethyl cellulose in the etherified cellulose into carboxymethyl cellulose acid; then, eluting most of the water-soluble impurities with the acid solution to obtain eluted cellulose; and then replacing the hydrogen ions in the carboxymethyl cellulose acid with an acid-sodium solution to obtain sodium carboxymethyl cellulose with a purity of 99.5% and a degree of substitution of 0.98.

[0004] Chinese patent CN105949329A discloses a production process for ultra-high viscosity sodium carboxymethyl cellulose, which comprises the following steps: (1) cellulose, alkali and ethanol are put into an alkalizing kneader in proportion and alkalized under nitrogen protection, and then an etherifying agent chloroacetic acid ethanol solution is put into the kneader to perform initial etherification of the material; (2) the above-mentioned material is conveyed into the etherification kneader to control the temperature and reaction time for etherification reaction, and the material is conveyed to a washing kettle after the etherification reaction is completed; (3) the material of the etherification reaction is washed with a dilute ethanol solution to remove the salt generated by the reaction, so that the purity of the product reaches more than 99.5%; (4) the material is then centrifuged and the solid material is conveyed to a stripper, and the ethanol solvent is extracted from the material by the stripper; (5) the material after the stripper is dried in a vibrating fluidized bed to remove excess water, and then pulverized to obtain a product with a viscosity of >7000 mPa.s at a concentration of 1% and a purity of >99.5%.

[0005] Chinese patent CN105801710A provides a production process for ultra-low viscosity sodium carboxymethyl cellulose. The specific production steps are as follows: (1) Cellulose, alkali, and ethanol are placed in an alkalizing kneader in proportion for alkalization, and then an etherifying agent, chloroacetic acid ethanol solution, is added to perform initial etherification of the material, and then a viscosity reducer, hydrogen peroxide ethanol solution, is added to perform a viscosity reduction; (2) The above-mentioned material is conveyed into the etherification kneader for etherification reaction, and after the etherification reaction is completed, the material is conveyed to a washing kettle; (3) The material of the etherification reaction is washed with a dilute ethanol solution to remove the salt generated by the reaction, so that the purity of the product reaches more than 99%; (4) The material is then centrifuged and the solid material is conveyed to a steam stripper; (5) The material after the steam stripper is dried in a vibrating fluidized bed to remove excess water and then pulverized to obtain a product with a degree of substitution of 0.8-1.0, a viscosity of 4% and a viscosity of 20-100 MPa.

[0006] In the prior art, sodium carboxymethyl cellulose produced from refined cotton suffers from high product weight and high cost. Sodium carboxymethyl cellulose produced from wood pulp suffers from low sodium carboxymethyl cellulose content and low specific gravity, limiting its use to well drilling mud treatment agents, synthetic detergents, and builders. Sodium carboxymethyl cellulose produced from bamboo pulp suffers from low sodium carboxymethyl cellulose content and uneven product substitution, primarily finding application in low-end applications such as textile printing and dyeing sizing agents and daily chemical thickeners. Furthermore, both the aqueous and solvent methods for producing sodium carboxymethyl cellulose have drawbacks. The aqueous method suffers from a lack of a large amount of liquid medium, resulting in a temperature increase caused by the heat generated by the reaction, which accelerates side reactions and ultimately results in low etherification efficiency and poor quality. The solvent method also suffers from relatively poor temperature controllability, high space requirements and processing costs, and strict control over the feeding time. Therefore, the market currently lacks a method for producing sodium carboxymethyl cellulose that is low-cost, stable in quality, efficient, safe, and environmentally friendly. Summary of the Invention

[0007] The purpose of this application is to address the deficiencies in the existing technology and provide a low-cost preparation method for sodium carboxymethyl cellulose. The sodium carboxymethyl cellulose prepared by this method ensures product quality, meets market demand, and significantly reduces production costs, which is conducive to market promotion and application.

[0008] To achieve the above objectives, the technical solutions adopted in this application are as follows: A low-cost preparation method of sodium carboxymethyl cellulose comprises the steps of alkalizing, etherifying and neutralizing bamboo pulp, refined cotton and wood pulp as fiber raw materials; wherein, The mass fraction of bamboo pulp in the fiber raw materials is 10% to 50%, the mass fraction of wood pulp is 10% to 50%, and the mass fraction of refined cotton is 10% to 50%; Before using alkali solution for alkalization, the alkali solution needs to be pretreated. The pretreatment steps are as follows: Ethanol, isopropyl alcohol, soft water and sodium dithionite are mixed, sodium hydroxide solution is added, the temperature is raised to 70-80° C. and kept warm for 30-50 minutes, then the temperature is lowered to 40-50° C. and kept warm for 20-30 minutes, and finally the temperature is lowered to room temperature to complete the pretreatment and obtain a pretreated alkali solution.

[0009] Preferably, the mass fraction of bamboo pulp in the fiber raw material is 20%, the mass fraction of wood pulp is 30-50%, and the mass fraction of refined cotton is 30-50%, that is, the mass ratio of bamboo pulp, wood pulp and refined cotton is 2: (3-5): (3-5).

[0010] Furthermore, the bamboo pulp, refined cotton, and wood pulp are pulverized before the alkalization treatment. The bulk density of the pulverized bamboo pulp is preferably 130-230 g / L, the bulk density of the refined cotton is preferably 110-210 g / L, and the bulk density of the pulverized wood pulp is preferably 80-180 g / L. The pulverized fiber raw materials can obtain a more optimal fiber cross-section and bulk density, which is conducive to the alkalization treatment.

[0011] Furthermore, the mass ratio of the ethanol, isopropanol, soft water, sodium dithionite, and sodium hydroxide solution is (28-35): (35-42): (2-5): (0.12-0.15): (7-12).

[0012] Furthermore, the present application adds ethanol and isopropanol to the alkali solution. The addition of ethanol can promote the dispersion of the fiber raw material in the alkali solution, and the addition of isopropanol can disperse the reaction heat, so that there will be no sudden overheating phenomenon in the high-temperature reaction stage. It also has a certain penetration-promoting effect, which helps to promote the subsequent alkalization and etherification treatment to a certain extent. The present application combines the two in proportion, and ethanol and isopropanol have a certain synergistic effect, which can greatly promote the alkalization and etherification treatment, thereby improving product quality.

[0013] Furthermore, the mass concentration of the sodium hydroxide solution is 30-35%.

[0014] The alkali solution of the present application is first pretreated and then the cellulose raw material is alkalized. Sodium dithionite is added to the alkali solution. Under high-temperature activation, its molecules are evenly distributed in the alkali solution, which enhances the reaction activity of the entire solution system, thereby improving the alkalization effect and enhancing product performance; the staged cooling treatment is adopted during the alkali solution pretreatment process, which can reduce the damage to the alkali solution system. The activity of the alkali solution after pretreatment is improved, which helps to improve the alkalization effect and also improve the stability of product batches.

[0015] Furthermore, the alkalization process is as follows: adding fiber raw materials to the pretreated alkali solution, cold stirring for 20 to 40 minutes under vacuum conditions, then heating to 30 to 32° C., and alkalizing at this temperature for 140 to 250 minutes.

[0016] Furthermore, the mass ratio of the pretreatment alkali solution to the fiber raw material is (11-12):1.

[0017] In some schemes, the etherification process is carried out using sodium chloroacetate as an etherifying agent, and the mass ratio of the fiber raw material to sodium chloroacetate is 1:(1-1.5) / fiber, preferably 1:1.34. The etherification process is as follows: the alkalized fiber raw material is mixed with sodium chloroacetate, stirred cold for 20-60 minutes, and then heated to perform three-stage etherification: One-stage etherification: heating to 45-60℃ to start one-stage etherification, etherification time 1-3h; Second stage etherification: heating to 60-70℃ for second stage etherification, etherification time 1-3h; Three-stage etherification: raise the temperature to 70-75°C for three-stage etherification, with an etherification time of 1-2 hours.

[0018] In other schemes, the etherification process uses sodium carbonate and chloroacetic acid as etherifying agents, and the mass ratio of fiber raw material to sodium carbonate and chloroacetic acid is 10: (2.8-3.2): (4.7-5.3). The etherification process is as follows: the alkalized fiber raw material is mixed with sodium carbonate and chloroacetic acid, stirred cold for 30-50 minutes, and then heated to perform three-stage etherification: One-stage etherification: heating to 45-55°C to start one-stage etherification, etherification time is 2-3h, stirring speed is 15-18rpm; Second stage etherification: heat to 58-62°C to start the second stage etherification, the etherification time is 1.5-2h; stirring speed is 22-30rpm; Three-stage etherification: heat to 68-72°C to start three-stage etherification, the etherification time is 1-2 hours; stirring speed is 33-40 rpm.

[0019] The two etherifying agents used in the etherification treatment described above both undergo a nucleophilic substitution reaction, grafting carboxymethyl groups onto the glucose units of cellulose to form the high-molecular-weight derivative sodium carboxymethyl cellulose. Compared to direct etherification with sodium chloroacetate, etherification using chloroacetic acid and sodium carbonate allows the etherifying agents to diffuse and penetrate more easily through the material's micropores, improving penetration into the cellulose raw material and increasing the substitution rate. The bleaching function of sodium carbonate also enhances the product's whiteness. Furthermore, the use of chloroacetic acid and sodium carbonate together can adjust the system's pH, resulting in a milder permeation reaction and fewer byproducts, which helps increase the sodium carboxymethyl cellulose content in the product.

[0020] Furthermore, during the neutralization process, any one or more acids selected from glacial acetic acid, glacial acetic acid, and acetic acid are added for neutralization; specifically, the neutralization steps are as follows: the etherification product is cooled to below 60° C., and acid is added for neutralization for 30 to 50 minutes, and the neutralization is completed.

[0021] Furthermore, the low-cost composite preparation method of sodium carboxymethyl cellulose also includes post-processing the neutralized product, and the post-processing steps include: centrifugation, washing, drying, and crushing.

[0022] The washing process uses an ethanol solution for air stripping washing, and the concentration of the ethanol solution is preferably 70% or above. Centrifugation, drying, and pulverization are all conventional operations in the art and will not be described in detail here.

[0023] Compared with the prior art, this application has the following beneficial effects: 1. This application uses bamboo pulp, refined cotton and wood pulp as raw materials, and produces sodium carboxymethyl cellulose through steps such as alkalization, etherification and neutralization. It can significantly reduce production costs while ensuring a high sodium carboxymethyl cellulose content and maintaining product quality. The product quality meets market demand and is conducive to market promotion and application.

[0024] 2. This application uses pre-treated alkali solution to alkalize the fiber raw materials. The activity of the pre-treated alkali solution is improved, which helps to improve the alkalization effect.

[0025] 3. This application uses sodium chloroacetate, or sodium carbonate and chloroacetic acid in combination as etherifying agents for etherification, and in combination with corresponding etherification methods, can reduce production costs while ensuring product quality; compared with direct etherification with sodium chloroacetate, etherification using chloroacetic acid and sodium carbonate can improve the penetration of cellulose raw materials, increase the degree of substitution, and at the same time have a certain effect on improving the whiteness of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 This is the infrared spectrum of the sodium carboxymethyl cellulose prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0027] The present application is described in detail below with reference to examples, but the present application is not limited to these examples. Unless otherwise specified, the raw materials and catalysts in the examples of the present application are purchased through commercial channels.

[0028] Example 1 This embodiment relates to a low-cost composite preparation method for producing sodium carboxymethyl cellulose, comprising the following steps: (1) Fiber raw material blending: the mass fraction of bamboo pulp in the fiber raw materials is 10%, the mass fraction of wood pulp is 40%, and the mass fraction of refined cotton is 50%; (2) Alkali solution pretreatment: ethanol, isopropanol, soft water and sodium dithionite were mixed, 30% sodium hydroxide solution was added, the temperature was raised to 70°C and kept warm for 30 minutes, then the temperature was lowered to 40°C and kept warm for 20 minutes, and finally the temperature was lowered to room temperature to complete the pretreatment and obtain the pretreated alkali solution; The mass ratio of ethanol, isopropyl alcohol, soft water, sodium dithionite, and sodium hydroxide solution is 35:35:2:0.12:7; (3) Alkalization: Add fiber raw materials to the pretreatment alkali solution, with the mass ratio of pretreatment alkali solution to fiber raw materials being 11:1; cold stirring for 20 minutes under vacuum conditions, then heating to 30°C and alkalizing at this temperature for 140 minutes; (4) Etherification: The alkalized fiber raw material was mixed with sodium chloroacetate in a mass ratio of 1:1, stirred cold for 20 min, and then heated to 45 °C to start the first stage of etherification for 3 h; then heated to 60 °C for the second stage of etherification for 3 h; finally heated to 70 °C for the third stage of etherification for 1 h to complete the etherification; (5) Neutralization: The etherification product is cooled to below 60°C, and glacial acetic acid (10% of the mass of the fiber raw material) is added for neutralization for 30 minutes. After neutralization, the material is centrifuged; (6) Post-treatment: The centrifugal product is washed with 70% ethanol solution, dried and crushed.

[0029] The infrared spectrum of the product obtained in this application is tested. Figure 1 As shown in the figure, it can be seen that 3320cm -1 Nearby is the stretching vibration peak of -OH on the sodium carboxymethyl cellulose skeleton, 1620cm -1 Nearby is -COO - Antisymmetric stretching peak, 1400 cm -1 Nearby is -COO - Symmetrical stretching peak, 1000~1150cm -1 The characteristic peaks of COC and CO are located at .

[0030] Example 2 This embodiment relates to another low-cost composite preparation method for producing sodium carboxymethyl cellulose, comprising the following steps: (1) Blending fiber raw materials: Bamboo pulp, refined cotton and wood pulp are pulverized separately, wherein the bulk density of the bamboo pulp after pulverization is preferably 130 g / L, the bulk density of the refined cotton after pulverization is preferably 110 g / L, and the bulk density of the wood pulp after pulverization is preferably 80 g / L, and then mixed to obtain a fiber raw material; the mass fraction of the bamboo pulp in the fiber raw material is 20%, the mass fraction of the wood pulp is 30%, and the mass fraction of the refined cotton is 50%; (2) Alkali solution pretreatment: ethanol, isopropanol, soft water and sodium dithionite were mixed, 35% sodium hydroxide solution was added, the temperature was raised to 80°C and kept warm for 50 min, then the temperature was lowered to 50°C and kept warm for 30 min, and finally the temperature was lowered to room temperature to complete the pretreatment and obtain the pretreated alkali solution; The mass ratio of ethanol, isopropyl alcohol, soft water, sodium dithionite, and sodium hydroxide solution is 28:42:5:0.15:12; (3) Alkalization: Add fiber raw materials to the pretreatment alkali solution, with the mass ratio of pretreatment alkali solution to fiber raw materials being 12:1; cold stirring for 20 min under vacuum conditions, then heating to 32 °C and alkalizing at this temperature for 250 min; (4) Etherification: The alkalized fiber raw material was mixed with sodium carbonate and chloroacetic acid in a mass ratio of 10:3.2:5.3, stirred cold for 20 min, and then heated to 45 °C for the first stage of etherification, with an etherification time of 3 h and a stirring speed of 18 rpm; then heated to 58 °C for the second stage of etherification, with an etherification time of 2 h and a stirring speed of 30 rpm; finally heated to 68 °C for the third stage of etherification, with an etherification time of 2 h and a stirring speed of 36 rpm to complete the etherification; (5) Neutralization: The etherification product is cooled to below 60°C, and acetic acid (11% of the mass of the fiber raw material) is added for neutralization for 50 minutes. After neutralization, the material is centrifuged; (6) Post-treatment: The centrifugal product is washed with 70% ethanol solution, dried and crushed.

[0031] Example 3 This embodiment relates to another low-cost composite preparation method for producing sodium carboxymethyl cellulose, comprising the following steps: (1) Blending fiber raw materials: Bamboo pulp, refined cotton and wood pulp are pulverized separately, wherein the bulk density of the bamboo pulp after pulverization is preferably 230 g / L, the bulk density of the refined cotton after pulverization is preferably 210 g / L, and the bulk density of the wood pulp after pulverization is preferably 180 g / L, and then mixed to obtain a fiber raw material; the mass fraction of the bamboo pulp in the fiber raw material is 20%, the mass fraction of the wood pulp is 50%, and the mass fraction of the refined cotton is 30%; (2) Alkali solution pretreatment: ethanol, isopropanol, soft water and sodium dithionite were mixed, 35% sodium hydroxide solution was added, the temperature was raised to 80°C and kept warm for 50 min, then the temperature was lowered to 50°C and kept warm for 30 min, and finally the temperature was lowered to room temperature to complete the pretreatment and obtain the pretreated alkali solution; The mass ratio of ethanol, isopropyl alcohol, soft water, sodium dithionite, and sodium hydroxide solution is 28:42:5:0.15:12; (3) Alkalization: Add fiber raw materials to the pretreatment alkali solution, with the mass ratio of pretreatment alkali solution to fiber raw materials being 12:1; cold stirring for 40 min under vacuum conditions, then heating to 32 °C and alkalizing at this temperature for 250 min; (4) Etherification: The alkalized fiber raw material was mixed with sodium carbonate and chloroacetic acid in a mass ratio of 10:2.8:4.7, stirred cold for 30 min, and then heated to 55 °C for the first stage of etherification, with an etherification time of 2 h and a stirring speed of 18 rpm; then heated to 62 °C for the second stage of etherification, with an etherification time of 1.5 h and a stirring speed of 30 rpm; finally heated to 72 °C for the third stage of etherification, with an etherification time of 1 h and a stirring speed of 36 rpm to complete the etherification; (5) Neutralization: The etherification product is cooled to below 60°C, and acetic acid (11% of the mass of the fiber raw material) is added for neutralization for 50 minutes. After neutralization, the material is centrifuged; (6) Post-treatment: The centrifugal product is washed with 70% ethanol solution, dried and crushed.

[0032] Example 4 The difference from Example 3 is that the mass fraction of bamboo pulp in the fiber raw materials is 40%, the mass fraction of wood pulp is 50%, and the mass fraction of refined cotton is 10%.

[0033] Example 5 The difference from Example 3 is that the mass fraction of bamboo pulp in the fiber raw materials is 40%, the mass fraction of wood pulp is 10%, and the mass fraction of refined cotton is 50%.

[0034] Example 6 The difference from Example 3 is that the mass ratio of ethanol, isopropyl alcohol, soft water, sodium dithionite and sodium hydroxide solution in the alkali solution is 40:30:5:0.15:12.

[0035] Example 7 The difference from Example 3 is that the mass ratio of ethanol, isopropyl alcohol, soft water, sodium dithionite and sodium hydroxide solution in the alkali solution is 20:50:5:0.15:12.

[0036] Example 8 The difference from Example 3 is that sodium carbonate and chloroacetic acid are replaced by equal amounts of sodium chloroacetate, that is, the mass ratio of the fiber raw material to sodium chloroacetate is 10:7.5.

[0037] Example 9 The difference from Example 3 is that sodium carbonate and chloroacetic acid are replaced by equal amounts of chloroacetic acid and sodium chloroacetate, that is, the mass ratio of the fiber raw material to chloroacetic acid and sodium chloroacetate is 10:2:5.5.

[0038] Example 10 The difference from Example 3 is that the etherifying agent remains unchanged and the etherification process is the same as that of Example 1.

[0039] Example 11 The difference from Example 3 is that the second-stage etherification process is omitted.

[0040] Example 12 The difference from Example 3 is that one section of the etherification process is omitted.

[0041] Example 13 The difference from Example 3 is that the frequency conversion rate of the stirring motor in the three-stage etherification process is 36 rpm.

[0042] Comparative Example 1 The difference from Example 3 is that the fiber raw material is only refined cotton.

[0043] Comparative Example 2 The difference from Example 3 is that the fiber raw material is only wood pulp.

[0044] Comparative Example 3 The difference from Example 3 is that the fiber raw material is only bamboo pulp.

[0045] Comparative Example 4 The difference from Example 3 is that the mass fraction of bamboo pulp in the fiber raw materials is 60%, the mass fraction of wood pulp is 20%, and the mass fraction of refined cotton is 20%.

[0046] Comparative Example 5 The difference from Example 3 is that no sodium dithionite is added to the pretreatment alkali solution.

[0047] Comparative Example 6 The difference from Example 3 is that the sodium dithionite in the pretreatment alkali solution is replaced by an equal amount of sodium sulfite.

[0048] Comparative Example 7 The difference from Example 3 is that, in the alkali solution pretreatment, ethanol, isopropanol, soft water and sodium sulfite are mixed, a 35% by mass sodium hydroxide solution is added, the temperature is raised to 80° C. and kept warm for 50 minutes, and then the temperature is cooled to room temperature to complete the pretreatment to obtain a pretreated alkali solution.

[0049] Comparative Example 8 The difference from Example 3 is that no ethanol is added to the alkali solution, that is, the mass ratio of isopropyl alcohol, soft water, sodium dithionite, and sodium hydroxide solution is 70:5:0.15:12.

[0050] Comparative Example 9 The difference from Example 3 is that no isopropyl alcohol is added to the alkali solution, that is, the mass ratio of ethanol, soft water, sodium dithionite, and sodium hydroxide solution is 70:5:0.15:12.

[0051] Test Case The sodium carboxymethyl cellulose obtained in the above examples and comparative examples was prepared into a 2% aqueous solution and tested under a test environment of 25° C., as shown in Table 1 below.

[0052] Table 1. Test items and standards

[0053] The test results are shown in Tables 2 and 3 below.

[0054] Table 2. Test results of sodium carboxymethyl cellulose

[0055] Table 3. Test results of sodium carboxymethyl cellulose

[0056] As shown in Tables 2 and 3, in Comparative Examples 1-3, sodium carboxymethyl cellulose was prepared using refined cotton, wood pulp, and bamboo pulp as fiber raw materials, respectively. The sodium carboxymethyl cellulose content in the products obtained in Comparative Examples 2 and 3 was relatively low, and there were many side reactions. The degree of substitution of bamboo pulp was slightly low due to its natural density. The product obtained in Comparative Example 1 had a high content of sodium carboxymethyl cellulose and had high viscosity, degree of substitution, whiteness, etc. However, since the market price of refined cotton per ton was about RMB 15,000 per ton, which was about three times the price of wood pulp (about RMB 5,000 / ton) and bamboo pulp (about RMB 5,000 / ton), the production cost was relatively high.

[0057] Compared with Comparative Example 1, the product obtained in Example 3 has a comparable sodium carboxymethyl cellulose content and whiteness, while having an improved degree of substitution and viscosity, resulting in a better use effect. In addition, in Example 3, bamboo pulp, wood pulp, and refined cotton are compounded in a ratio of 2:5:3, and the cost is approximately 8,000 yuan, which greatly reduces the production cost. Therefore, the present application produces sodium carboxymethyl cellulose by compounding bamboo pulp, wood pulp, and refined cotton in a specific ratio, thereby significantly reducing the production cost while improving product quality.

[0058] In Examples 1 and 2, sodium chloroacetate, or chloroacetic acid and sodium carbonate, were used as etherifying agents for etherification, respectively. The resulting products maintained high levels of sodium carboxymethyl cellulose content, degree of substitution, viscosity, and whiteness. Therefore, using sodium chloroacetate, chloroacetic acid, and sodium carbonate as etherifying agents for etherification can reduce production costs while maintaining product quality. Furthermore, using sodium carbonate and chloroacetic acid as etherifying agents is more advantageous for the production of sodium carboxymethyl cellulose, ensuring consistent sodium carboxymethyl cellulose content, degree of substitution, and viscosity while also reducing the content of byproducts such as chloride, arsenic, and lead, and improving product whiteness.

[0059] However, compared with Example 3, the etherifying agent in Example 8 is sodium chloroacetate, and Example 9 uses chloroacetic acid and sodium chloroacetate as etherifying agents. The sodium carboxymethyl cellulose content, degree of substitution, and whiteness of the obtained product are all reduced. In Example 10, the etherification process adopts the method of Example 1, and the sodium carboxymethyl cellulose content and viscosity of the obtained product are reduced, while arsenic and lead are relatively high. The pH value is too high, which can easily reduce the colloidal stability, viscosity, and functionality (such as thickening, suspending, emulsification, etc.) or cause delamination. In addition, the etherification process of Examples 11 and 12 reduces one or two stages, and the sodium carboxymethyl cellulose content in the obtained product decreases linearly, and the degree of substitution and viscosity also decrease significantly. Therefore, although both etherifying agents can achieve the effects of the present application, the realization of the effects requires the etherifying agent to be combined with the etherification method.

[0060] In addition, the intra-batch and inter-batch quality stability of sodium carboxymethyl cellulose was tested. Specifically, samples were taken from five consecutive batches of normal production, with 10 samples in each batch. Their whiteness and degree of substitution were tested, and the coefficient of variation (CV) and standard deviation (SD) were calculated to evaluate the inter-batch quality stability. The specific results are shown in Table 4: Table 4. Results of inter-batch quality stability test

[0061] As shown in the table, compared with the comparative example, the standard deviation and coefficient of variation of the whiteness and degree of substitution of sodium carboxymethyl cellulose produced in five consecutive batches according to the technical solution provided in Example 3 are lower, indicating good batch-to-batch quality stability.

[0062] The foregoing is merely an embodiment of the present application, and the scope of protection of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the technical ideas and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A low-cost preparation method of sodium carboxymethyl cellulose, characterized in that: The method comprises taking bamboo pulp, refined cotton and wood pulp as fiber raw materials, and carrying out alkalization, etherification and neutralization to prepare the fiber; The mass fraction of bamboo pulp in the fiber raw materials is 10-50%, the mass fraction of wood pulp is 10-50%, and the mass fraction of refined cotton is 10-50%; Before using alkali solution for alkalization, the alkali solution needs to be pretreated. The pretreatment steps are as follows: Ethanol, isopropyl alcohol, soft water and sodium dithionite are mixed, sodium hydroxide solution is added, the temperature is raised to 70-80° C. and kept warm for 30-50 minutes, then the temperature is lowered to 40-50° C. and kept warm for 20-30 minutes, and finally the temperature is lowered to room temperature to complete the pretreatment and obtain a pretreated alkali solution.

2. A low-cost preparation method of sodium carboxymethyl cellulose according to claim 1, characterized in that, The mass ratio of the ethanol, isopropanol, soft water, sodium dithionite and sodium hydroxide solution is (28-35): (35-42): (2-5): (0.12-0.15): (7-12).

3. A low-cost preparation method of sodium carboxymethyl cellulose according to claim 1, characterized in that, The alkalization process is as follows: adding fiber raw materials to the pretreated alkali solution, cold stirring for 20 to 40 minutes under vacuum conditions, then heating to 30 to 32° C. and alkalizing at this temperature for 140 to 250 minutes.

4. The low-cost preparation method of sodium carboxymethyl cellulose according to claim 3, characterized in that: The mass ratio of pretreatment alkali solution and fiber raw material is (11-12):

1.

5. The low-cost preparation method of sodium carboxymethyl cellulose according to claim 1, characterized in that: The etherification process is carried out using sodium chloroacetate as an etherifying agent, and the mass ratio of the fiber raw material to the sodium chloroacetate is 1: (1 to 1.5).

6. The low-cost preparation method of sodium carboxymethyl cellulose according to claim 5, characterized in that: The etherification process is as follows: the alkalized fiber raw material is mixed with sodium chloroacetate, stirred cold for 20 to 60 minutes, and then heated for three-stage etherification: One-stage etherification: heating to 45-60℃ to start one-stage etherification, etherification time 1-3h; Second stage etherification: heating to 60-70℃ for second stage etherification, etherification time 1-3h; Three-stage etherification: raise the temperature to 70-75°C for three-stage etherification, with an etherification time of 1-2 hours.

7. The low-cost preparation method of sodium carboxymethyl cellulose according to claim 1, characterized in that: The etherification process uses sodium carbonate and chloroacetic acid as etherifying agents.

8. The low-cost preparation method of sodium carboxymethyl cellulose according to claim 7, characterized in that: The etherification process is as follows: the alkalized fiber raw material is mixed with sodium carbonate and chloroacetic acid, stirred cold for 30 to 50 minutes, and then heated for three-stage etherification: One-stage etherification: heating to 45-55°C to start the first-stage etherification, the etherification time is 2-3 hours, and the stirring speed is 15-18 rpm; Second stage etherification: heat to 58-62°C to start the second stage etherification, the etherification time is 1.5-2h; stirring speed is 22-30rpm; Three-stage etherification: heat to 68-72°C to start three-stage etherification, the etherification time is 1-2 hours; stirring speed is 33-40 rpm.

9. The low-cost preparation method of sodium carboxymethyl cellulose according to claim 1, characterized in that: During the neutralization process, any one or more acids selected from glacial acetic acid, glacial acetic acid, and acetic acid are added for neutralization.

10. A low-cost preparation method for sodium carboxymethyl cellulose according to any one of claims 1 to 9, characterized in that: The method also includes post-processing the neutralized product, and the post-processing steps include: centrifugation, washing, drying, and crushing.

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