A low cost process for the preparation of sodium carboxymethyl cellulose

Abstract

The application 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 performing alkalization, etherification and neutralization to obtain sodium carboxymethyl cellulose; the mass fraction of the bamboo pulp in the fiber raw materials is 10-50%, the mass fraction of the wood pulp is 10-50%, and the mass fraction of the refined cotton is 10-50%; the alkali liquor needs to be pretreated before being used for alkalization, and the pretreatment steps are as follows: mixing ethanol, isopropyl alcohol, soft water and sodium hydrosulfite, adding a sodium hydroxide solution, heating to 70-80 DEG C and keeping for 30-50 min, then cooling to 40-50 DEG C and keeping for 20-30 min, finally cooling to room temperature, and completing the pretreatment to obtain a pretreated alkali liquor. The method can ensure high sodium carboxymethyl cellulose content and product quality, greatly reduce the production cost under the premise of not reducing the product quality, the product quality meets the market demand, and the method is beneficial to market promotion and application.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium carboxymethyl cellulose preparation, and relates to a low-cost preparation method of sodium carboxymethyl cellulose. BACKGROUND

[0002] Carboxymethyl cellulose (CMC) is a water-soluble cellulose ether obtained by alkalization, etherification, neutralization and washing centrifugation and the like chemical modification of natural cellulose. Since the water solubility of carboxymethyl cellulose acid is poor, in order to better apply it, it is usually prepared into a salt sodium. At present, the raw materials for producing carboxymethyl cellulose sodium on the market mainly include the following: one is refined cotton (cotton linter) as the main raw material, and the other is wood pulp or bamboo pulp as the main raw material, and the preparation methods mainly include a water medium method and a solvent method.

[0003] Chinese patent CN118580378A discloses a preparation method of carboxymethyl cellulose. First, etherified bamboo cellulose fibers are acidified with an acid solution to convert carboxymethyl cellulose sodium in the etherified cellulose into carboxymethyl cellulose acid, and then most of the water-soluble impurities are eluted with an acid solution to obtain eluted cellulose. Then, the hydrogen ions in the carboxymethyl cellulose acid are replaced with an acid-sodium solution to obtain carboxymethyl cellulose sodium with a purity of 99.5% and a degree of substitution of 0.98.

[0004] Chinese patent CN105949329A discloses a production process of super-high-viscosity sodium carboxymethyl cellulose, which comprises the following operation steps: (1) cellulose, alkali and ethanol are proportionally put into an alkalization kneader to perform alkalization under nitrogen protection, and then an etherification agent, i.e., an ethanolic chloroacetic acid solution, is put in to perform initial etherification on the materials; (2) the above materials are transported into an etherification kneader to control the temperature and reaction time for etherification reaction, and after the etherification reaction is completed, the materials are transported to a washing kettle; (3) the materials after the etherification reaction are washed with a dilute ethanol solution to remove the generated salt, so that the purity of the product reaches more than 99.5%; (4) then, the materials are subjected to centrifugal pressing, the solid materials are transported to a stripping machine, and the materials are extracted by the stripping machine to extract the ethanol solvent; (5) the materials after the stripping machine are put into a vibration fluidized bed to remove excess water and are crushed to obtain the product, the viscosity of which is greater than 7000 mpa.s at a concentration of 1%, and the purity is greater than 99.5%.

[0005] Chinese patent CN105801710A provides a production process of carboxymethyl cellulose sodium with ultra-low viscosity. The specific production steps are as follows: (1) cellulose, alkali and ethanol are put into an alkali kneader in proportion to carry out alkali treatment, and then an etherifying agent, ethanolic chloroacetic acid solution, is put in to carry out initial etherification, and a viscosity reducer, hydrogen peroxide ethanol solution, is added to carry out viscosity reduction for the first time; (2) the above-mentioned material is transported into an etherification kneader to carry out etherification reaction, and the material is transported to a washing kettle after the etherification reaction is completed; (3) the material after etherification reaction is washed with dilute ethanol solution to remove the salt generated in the reaction, so that the purity of the product reaches more than 99%; (4) then the material is centrifuged and pressed, and the solid material is transported to a stripping machine; (5) the material after the stripping machine enters a vibrating fluidized bed to dry and remove excess water, and is crushed to obtain the product, the degree of substitution is 0.8-1.0, and the 4% viscosity is 20-100 mpa.

[0006] In the prior art, the carboxymethyl cellulose sodium prepared by using refined cotton has the characteristics of high product quality specific gravity and high cost; the carboxymethyl cellulose sodium prepared by using wood pulp has the defects of low content and light specific gravity, and can only be used as a well drilling mud treating agent, a synthetic detergent, a washing agent and the like; the carboxymethyl cellulose sodium prepared by using bamboo pulp has the problems of too low carboxymethyl cellulose sodium content and uneven product degree of substitution, and is mostly used in low-end fields such as textile printing and dyeing sizing agent and daily chemical tackifier. In addition, the production of carboxymethyl cellulose sodium by using the water medium method and the solvent method has some defects, such as the water medium method lacks a large amount of liquid medium, the heat generated in the reaction promotes the temperature to rise, and the speed of the side reaction is accelerated, so that the etherification efficiency is low and the quality is poor; the solvent method has relatively poor temperature controllability, high space requirement and processing cost, and strict control of feeding time. Therefore, there is a lack of a carboxymethyl cellulose sodium preparation method with low cost, stable quality, high performance, high safety and environmental protection in the market at present. SUMMARY

[0007] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a low-cost preparation method of carboxymethyl cellulose sodium. The carboxymethyl cellulose sodium prepared by using the method can ensure product quality, meet market demand, and greatly reduce production cost, which is conducive to market promotion and application.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0009] A low-cost preparation method of carboxymethyl cellulose sodium, which comprises bamboo pulp, refined cotton and wood pulp as fiber raw materials, and is prepared by alkali treatment, etherification and neutralization; wherein,

[0010] The mass fraction of bamboo pulp in the fiber raw material is 10-50%, the mass fraction of wood pulp is 10-50%, and the mass fraction of refined cotton is 10-50%;

[0011] The alkali liquor needs to be pretreated before being alkalinized with the alkali liquor, and the pretreatment step is as follows:

[0012] The ethanol, isopropyl alcohol, soft water and sodium hydrosulfite are mixed, the sodium hydroxide solution is added, the temperature is raised to 70-80℃ and kept for 30-50 min, then the temperature is lowered to 40-50℃ and kept for 20-30 min, and finally the temperature is lowered to room temperature, and the pretreatment is completed to obtain the pretreated alkali liquor.

[0013] Preferably, the mass fraction of the bamboo pulp in the fiber raw material is 20%, the mass fraction of the wood pulp is 30-50%, and the mass fraction of the refined cotton is 30-50%, that is, the mass ratio of the bamboo pulp, the wood pulp and the refined cotton is 2:(3-5):(3-5).

[0014] Further, the bamboo pulp, the refined cotton and the wood pulp are further subjected to a crushing treatment before being subjected to the alkalinization treatment, and the bulk density of the crushed bamboo pulp is preferably 130-230 g / L, the bulk density of the crushed refined cotton is preferably 110-210 g / L, and the bulk density of the crushed wood pulp is preferably 80-180 g / L. The fiber raw material after the crushing treatment can obtain a more optimal fiber cross section and bulk density, which is beneficial to the alkalinization treatment.

[0015] Further, the mass ratio of the ethanol, isopropyl alcohol, soft water, sodium hydrosulfite and sodium hydroxide solution is (28-35):(35-42):(2-5):(0.12-0.15):(7-12).

[0016] Further, the ethanol and isopropyl alcohol are added to the alkali liquor in the present application, the addition of the ethanol can promote the dispersion of the fiber raw material in the alkali liquor, the addition of the isopropyl alcohol can disperse the reaction heat, and the abrupt overheating phenomenon will not occur in the high-temperature reaction stage, and the isopropyl alcohol also has a certain penetration-promoting effect, which is helpful to promote the subsequent alkalinization etherification treatment to a certain extent; the ethanol and isopropyl alcohol have a certain synergistic effect when they are used in combination according to the proportion, which can greatly promote the alkalinization etherification treatment, thereby improving the product quality.

[0017] Further, the mass concentration of the sodium hydroxide solution is 30-35%.

[0018] The alkali liquor of the present application is pretreated before being subjected to the alkalinization treatment of the cellulose raw material, sodium hydrosulfite is added to the alkali liquor, which is uniformly distributed in the alkali solution under high-temperature activation, thereby enhancing the reaction activity of the entire solution system, improving the alkalinization effect and product performance; the alkali liquor is subjected to a staged cooling treatment in the pretreatment process, which can reduce the damage to the alkali liquor system, the activity of the pretreated alkali liquor is improved, which is helpful to improve the alkalinization effect and also improves the batch stability of the product.

[0019] Further, the alkali treatment process is: adding the fiber raw material into the pretreatment alkali liquor, cold stirring for 20-40 min under vacuum, then heating to 30-32℃, and alkali treatment for 140-250 min at this temperature.

[0020] Further, the mass ratio of the pretreatment alkali liquor to the fiber raw material is (11-12):1.

[0021] In some schemes, the etherification process is carried out using sodium chloroacetate as the etherification agent, and the mass ratio of the fiber raw material to sodium chloroacetate is 1:(1-1.5), preferably 1:1.34; the etherification process is: mixing the fiber raw material after the alkali treatment with sodium chloroacetate, cold stirring for 20-60 min, then heating for three-stage etherification:

[0022] First-stage etherification: heating to 45-60℃ to start the first-stage etherification, and the etherification time is 1-3 h;

[0023] Second-stage etherification: heating to 60-70℃ to start the second-stage etherification, and the etherification time is 1-3 h;

[0024] Third-stage etherification: heating to 70-75℃ to start the third-stage etherification, and the etherification time is 1-2 h.

[0025] In other schemes, the etherification process uses sodium carbonate and chloroacetic acid as the etherification agent, and the mass ratio of the fiber raw material to sodium carbonate, chloroacetic acid is 10:(2.8-3.2):(4.7-5.3); the etherification process is: mixing the fiber raw material after the alkali treatment with sodium carbonate and chloroacetic acid, cold stirring for 30-50 min, then heating for three-stage etherification:

[0026] First-stage etherification: heating to 45-55℃ to start the first-stage etherification, and the etherification time is 2-3 h, and the stirring speed is 15-18 rpm;

[0027] Second-stage etherification: heating to 58-62℃ to start the second-stage etherification, and the etherification time is 1.5-2 h; and the stirring speed is 22-30 rpm;

[0028] Third-stage etherification: heating to 68-72℃ to start the third-stage etherification, and the etherification time is 1-2 h; and the stirring speed is 33-40 rpm.

[0029] The etherification process is a nucleophilic substitution reaction, which grafts carboxymethyl groups to the glucose units of cellulose to form the high molecular derivative sodium carboxymethyl cellulose. Compared with direct etherification using sodium chloroacetate, the etherification using chloroacetic acid and sodium carbonate is more likely to diffuse and penetrate through the small pores of the material, improve the penetration of the cellulose raw material, increase the substitution rate, and the bleaching function of sodium carbonate can improve the whiteness of the product. In addition, the use of chloroacetic acid and sodium carbonate together can adjust the pH value of the system, gently penetrate the reaction, and produce less by-product, which helps to increase the content of sodium carboxymethyl cellulose in the product.

[0030] Further, in the neutralization process, any one or more of the acids of glacial acetic acid, glacial acetic acid, and acetic acid is added for neutralization; specifically, the neutralization step is as follows: the etherification product is cooled to below 60℃, and the acid is added for 30-50min, and the neutralization is completed.

[0031] Further, the low-cost composite preparation method of the sodium carboxymethyl cellulose further comprises post-treatment of the neutralized product, and the post-treatment process comprises: centrifugation, washing, drying, and crushing.

[0032] The washing process uses ethanol solution for gas stripping washing, and the concentration of the ethanol solution is preferably 70% or higher. Centrifugation, drying, and crushing are all conventional operations in the art, and will not be described here.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] 1. The present application uses bamboo pulp, refined cotton, and wood pulp as raw materials, and produces sodium carboxymethyl cellulose through alkalization, etherification, and neutralization, etc. steps, which can greatly reduce the production cost under the premise of ensuring high sodium carboxymethyl cellulose content and product quality, and the product quality meets market demand, which is conducive to market promotion and application.

[0035] 2. The present application uses pretreated alkali solution for alkalization treatment of the fiber raw material, and the activity of the pretreated alkali solution is improved, which helps to improve the alkalization effect.

[0036] 3. The present application uses sodium chloroacetate, or sodium carbonate and chloroacetic acid as etherification agent for etherification, and cooperates with the corresponding etherification method, which can reduce the production cost under the premise of ensuring the product quality; compared with direct etherification using sodium chloroacetate, the etherification using chloroacetic acid and sodium carbonate can improve the penetration of the cellulose raw material, increase the degree of substitution, and also has a certain effect on improving the whiteness of the product. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments

[0038] Figure 1 The infrared spectrum of sodium carboxymethyl cellulose prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0039] The application will be described in greater detail below with reference to the embodiments. However, the application is not limited to these embodiments. Unless otherwise specified, the raw materials and catalysts in the embodiments of the present application are all purchased through commercial channels.

[0040] Example 1

[0041] This embodiment relates to a low-cost composite preparation method for producing sodium carboxymethyl cellulose, comprising the following steps:

[0042] (1) Fiber raw material blending: the mass fraction of bamboo pulp in the fiber raw material is 10%, the mass fraction of wood pulp is 40%, and the mass fraction of refined cotton is 50%;

[0043] (2) Alkali liquor pretreatment: ethanol, isopropyl alcohol, soft water, and sodium hydrosulfite are mixed, a 30% sodium hydroxide solution is added, the temperature is raised to 70°C and kept for 30 min, then the temperature is lowered to 40°C and kept for 20 min, and finally the temperature is lowered to room temperature, and the pretreatment is completed to obtain pretreated alkali liquor;

[0044] The mass ratio of ethanol, isopropyl alcohol, soft water, sodium hydrosulfite, and sodium hydroxide solution is 35:35:2:0.12:7;

[0045] (3) Alkali treatment: the fiber raw material is added to the pretreated alkali liquor, and the mass ratio of the pretreated alkali liquor to the fiber raw material is 11:1; under vacuum conditions, cold stirring is performed for 20 min, then the temperature is raised to 30°C, and alkali treatment is performed at this temperature for 140 min;

[0046] (4) Etherification: the alkali-treated fiber raw material is mixed with sodium chloroacetate at a mass ratio of 1:1, cold stirring is performed for 20 min, then the temperature is raised to 45°C to start the first-stage etherification, the etherification time is 3 h; then the temperature is raised to 60°C to perform the second-stage etherification, the etherification time is 3 h; finally, the temperature is raised to 70°C to perform the third-stage etherification, the etherification time is 1 h, and the etherification is completed;

[0047] (5) Neutralization: the etherification product is cooled to below 60°C, 10% of ice acetic acid based on the mass of the fiber raw material is added, and neutralization is performed for 30 min, and then the neutralized material is centrifuged;

[0048] (6) Post-treatment: the centrifuged product is washed by air stripping with 70% ethanol solution, and then dried and crushed to obtain the product.

[0049] The product obtained in the present application was subjected to infrared spectrum test, and the infrared spectrum diagram thereof is shown in Figure 1. Figure 1 As can be seen from the figure, the peak of the stretching vibration of -OH on the sodium carboxymethyl cellulose skeleton is at 3320 cm -1 , the peak of -COO -1 is at 1620 cm - , the anti-symmetrical stretching peak of -COO -1 is at 1400 cm - , the symmetrical stretching peak of -COO -1 is at 1000-1150 cm .

[0050] Example 2

[0051] The present example relates to another low-cost composite production method for producing sodium carboxymethyl cellulose, comprising the following steps:

[0052] (1) Fiber raw material blending: bamboo pulp, refined cotton and wood pulp are respectively pulverized, the bulk density of the pulverized bamboo pulp is preferably 130 g / L, the bulk density of the pulverized refined cotton is preferably 110 g / L, and the bulk density of the pulverized wood pulp is preferably 80 g / L, and then mixed to obtain a fiber raw material; the mass fraction of bamboo pulp in the fiber raw material is 20%, the mass fraction of wood pulp is 30%, and the mass fraction of refined cotton is 50%;

[0053] (2) Alkali liquor pretreatment: ethanol, isopropyl alcohol, soft water and sodium hydrosulfite are mixed, a sodium hydroxide solution with a mass fraction of 35% is added, the temperature is raised to 80°C and kept for 50 min, then the temperature is lowered to 50°C and kept for 30 min, and finally the temperature is lowered to room temperature, and the pretreatment is completed to obtain a pretreated alkali liquor;

[0054] The mass ratio of ethanol, isopropyl alcohol, soft water, sodium hydrosulfite and sodium hydroxide solution is 28:42:5:0.15:12;

[0055] (3) Alkali treatment: the fiber raw material is added to the pretreated alkali liquor, and the mass ratio of the pretreated alkali liquor to the fiber raw material is 12:1; under vacuum conditions, cold stirring is performed for 20 min, then the temperature is raised to 32°C, and alkali treatment is performed at this temperature for 250 min;

[0056] (4) Etherification: the fiber raw material after alkali treatment is mixed with sodium carbonate and chloroacetic acid according to a mass ratio of 10:3.2:5.3, cold stirring is performed for 20 min, then the temperature is raised to 45°C to start the first-stage etherification, the etherification time is 3 h, and the stirring speed is 18 rpm; then the temperature is raised to 58°C to perform the second-stage etherification, the etherification time is 2 h, and the stirring speed is 30 rpm; finally, the temperature is raised to 68°C to perform the third-stage etherification, the etherification time is 2 h, and the stirring speed is 36 rpm, and the etherification is completed;

[0057] (5) Neutralization: the etherification product is cooled to below 60°C, 11% of acetic acid based on the mass of the fiber raw material is added for neutralization for 50 min, and the neutralized product is centrifuged;

[0058] (6) Post-treatment: the centrifuged product is washed by air stripping with 70% ethanol solution, dried, and crushed to obtain the product.

[0059] Example 3

[0060] This example relates to another low-cost composite production method for producing sodium carboxymethyl cellulose, comprising the following steps:

[0061] (1) Fiber raw material blending: bamboo pulp, refined cotton, and wood pulp are respectively crushed, the bulk density of the crushed bamboo pulp is preferably 230 g / L, the bulk density of the crushed refined cotton is preferably 210 g / L, and the bulk density of the crushed wood pulp is preferably 180 g / L, and then mixed to obtain the fiber raw material; the mass fraction of bamboo pulp in the fiber raw material is 20%, the mass fraction of wood pulp is 50%, and the mass fraction of refined cotton is 30%;

[0062] (2) Alkali liquor pretreatment: ethanol, isopropyl alcohol, soft water, and sodium hydrosulfite are mixed, a 35% sodium hydroxide solution is added, heated to 80°C and kept for 50 min, then cooled to 50°C and kept for 30 min, and finally cooled to room temperature to complete the pretreatment to obtain the pretreated alkali liquor;

[0063] The mass ratio of ethanol, isopropyl alcohol, soft water, sodium hydrosulfite, and sodium hydroxide solution is 28:42:5:0.15:12;

[0064] (3) Alkali treatment: the fiber raw material is added to the pretreated alkali liquor, and the mass ratio of the pretreated alkali liquor to the fiber raw material is 12:1; under vacuum conditions, cold stirring is performed for 40 min, then heated to 32°C, and alkali treatment is performed at this temperature for 250 min;

[0065] (4) Etherification: the alkali-treated fiber raw material is mixed with sodium carbonate and chloroacetic acid according to a mass ratio of 10:2.8:4.7, cold stirring is performed for 30 min, then heated to 55°C to start the first-stage etherification, the etherification time is 2 h, and the stirring speed is 18 rpm; then heated to 62°C to perform the second-stage etherification, the etherification time is 1.5 h, and the stirring speed is 30 rpm; finally, heated to 72°C to perform the third-stage etherification, the etherification time is 1 h, and the stirring speed is 36 rpm, to complete the etherification;

[0066] (5) Neutralization: the etherification product is cooled to below 60°C, 11% of acetic acid based on the mass of the fiber raw material is added for neutralization for 50 min, and the neutralized product is centrifuged;

[0067] (6) Post-treatment: The centrifuged product is washed by air stripping with 70% ethanol solution, dried, and crushed to obtain the product.

[0068] Example 4

[0069] The difference from Example 3 is that the mass fraction of bamboo pulp in the fiber raw material is 40%, the mass fraction of wood pulp is 50%, and the mass fraction of refined cotton is 10%.

[0070] Example 5

[0071] The difference from Example 3 is that the mass fraction of bamboo pulp in the fiber raw material is 40%, the mass fraction of wood pulp is 10%, and the mass fraction of refined cotton is 50%.

[0072] Example 6

[0073] The difference from Example 3 is that the mass ratio of ethanol, isopropyl alcohol, soft water, sodium hydrosulfite, and sodium hydroxide solution in the lye is 40:30:5:0.15:12.

[0074] Example 7

[0075] The difference from Example 3 is that the mass ratio of ethanol, isopropyl alcohol, soft water, sodium hydrosulfite, and sodium hydroxide solution in the lye is 20:50:5:0.15:12.

[0076] Example 8

[0077] The difference from Example 3 is that sodium carbonate and chloroacetic acid are replaced with an equal amount of sodium chloroacetate, i.e., the mass ratio of fiber raw material to sodium chloroacetate is 10:7.5.

[0078] Example 9

[0079] The difference from Example 3 is that sodium carbonate and chloroacetic acid are replaced with an equal amount of chloroacetic acid and sodium chloroacetate, i.e., the mass ratio of fiber raw material to chloroacetic acid and sodium chloroacetate is 10:2:5.5.

[0080] Example 10

[0081] The difference from Example 3 is that the etherifying agent remains unchanged, and the etherification process is the same as in Example 1.

[0082] Example 11

[0083] The difference from Example 3 is that the two-stage etherification process is omitted.

[0084] Example 12

[0085] The difference from Example 3 is that the one-stage etherification process is omitted.

[0086] Example 13

[0087] The difference from Example 3 is that the frequency of the stirring motor in the three-stage etherification process is 36 rpm.

[0088] Comparative Example 1

[0089] The difference from Example 3 is that the fiber raw material is only refined cotton.

[0090] Comparative Example 2

[0091] The difference from Example 3 is that the fiber raw material is only wood pulp.

[0092] Comparative Example 3

[0093] The difference from Example 3 is that the fiber raw material is only bamboo pulp.

[0094] Comparative Example 4

[0095] The difference from Example 3 is that the mass fraction of bamboo pulp in the fiber raw material is 60%, the mass fraction of wood pulp is 20%, and the mass fraction of refined cotton is 20%.

[0096] Comparative Example 5

[0097] The difference from Example 3 is that sodium hyposulfite is not added in the pretreatment lye.

[0098] Comparative Example 6

[0099] The difference from Example 3 is that sodium hyposulfite in the pretreatment lye is replaced by an equal amount of sodium sulfite.

[0100] Comparative Example 7

[0101] The difference from Example 3 is that the lye pretreatment: ethanol, isopropyl alcohol, soft water, and sodium sulfite are mixed, a 35% mass fraction of sodium hydroxide solution is added, the temperature is raised to 80°C and kept for 50 min, then the temperature is lowered to room temperature, and the pretreatment is completed to obtain the pretreatment lye.

[0102] Comparative Example 8

[0103] The difference from Example 3 is that ethanol is not added in the lye, i.e. the mass ratio of isopropyl alcohol, soft water, sodium hyposulfite, and sodium hydroxide solution is 70:5:0.15:12.

[0104] Comparative Example 9

[0105] The difference from Example 3 is that isopropyl alcohol is not added in the lye, i.e. the mass ratio of ethanol, soft water, sodium hyposulfite, and sodium hydroxide solution is 70:5:0.15:12.

[0106] Test Example

[0107] The sodium carboxymethyl cellulose obtained in the above examples and comparative examples was configured into a 2% aqueous solution, and tested in a test environment at 25°C. The specific test items and standards are shown in Table 1 below.

[0108] Table 1. Test items and standards

[0109]

[0110] The test results are shown in Tables 2 and 3 below.

[0111] Table 2. Test results of sodium carboxymethyl cellulose

[0112]

[0113] Table 3. Test results of sodium carboxymethyl cellulose

[0114]

[0115] As shown in Tables 2 and 3, the sodium carboxymethyl cellulose in Comparative Examples 1-3 was prepared using refined cotton, wood pulp, and bamboo pulp as the fiber raw material, respectively. The content of sodium carboxymethyl cellulose in the products obtained in Comparative Examples 2 and 3 was low, and the number of side reactions was high. The degree of substitution of the sodium carboxymethyl cellulose obtained from bamboo pulp was slightly low due to the natural density of the bamboo pulp. The content of sodium carboxymethyl cellulose in the product obtained in Comparative Example 1 was high, and the product had high viscosity, degree of substitution, and whiteness, etc. However, the market price of refined cotton was about 15000 yuan per ton, which was about 3 times the price of wood pulp (about 5000 yuan per ton) and bamboo pulp (about 5000 yuan per ton), and the production cost was high.

[0116] Compared with Comparative Example 1, the content of sodium carboxymethyl cellulose and the whiteness of the product obtained in Example 3 were equivalent, but the degree of substitution and the viscosity were improved, and the use effect was better. In addition, the bamboo pulp, wood pulp, and refined cotton were compounded in a ratio of 2:5:3 in Example 3, and the cost was about 8000 yuan, which greatly reduced the production cost. Therefore, the bamboo pulp, wood pulp, and refined cotton were compounded in a specific ratio to produce sodium carboxymethyl cellulose, which greatly reduced the production cost while improving the product quality.

[0117] Examples 1 and 2 used sodium chloroacetate, or chloroacetic acid and sodium carbonate as etherifying agents for etherification, and the content of sodium carboxymethyl cellulose, the degree of substitution, the viscosity, and the whiteness of the obtained products were all maintained at a high level. Therefore, using sodium chloroacetate, or chloroacetic acid and sodium carbonate as etherifying agents for etherification can reduce the production cost while ensuring the product quality. In addition, using chloroacetic acid and sodium carbonate as etherifying agents for the preparation of sodium carboxymethyl cellulose has more advantages, as it can ensure the content of sodium carboxymethyl cellulose, the degree of substitution, and the viscosity index, and the content of by-products such as chlorides, arsenic, and lead is also reduced, which helps to improve the whiteness of the product.

[0118] But compared with example 3, in example 8, the etherifying agent is sodium chloroacetate, in example 9, the etherifying agent is sodium chloroacetate and chloroacetic acid, the sodium carboxymethyl cellulose content, the degree of substitution and the whiteness of the product obtained are decreased; in example 10, the etherification process is carried out according to the method of example 1, the sodium carboxymethyl cellulose content and the viscosity of the product obtained are decreased, while the arsenic and lead are too high; the pH value is too high, which is easy to reduce the colloidal stability, viscosity and functionality (such as thickening, suspension, emulsification, etc.) or cause delamination; in addition, the etherification process of examples 11 and 12 reduces one stage or two stages, the sodium carboxymethyl cellulose content of the product obtained decreases linearly, and the degree of substitution and viscosity also decrease significantly. Therefore, although both etherifying agents can achieve the effect of the present application, the effect needs to be achieved by the etherifying agent in combination with the etherification method.

[0119] In addition, the in-batch and batch-to-batch quality stability of sodium carboxymethyl cellulose was tested. Specifically, samples were taken from 5 consecutive batches of normally produced products, 10 samples per batch, and the whiteness and degree of substitution were tested to calculate the coefficient of variation CV value and standard deviation SD for evaluating the batch-to-batch quality stability. The specific results are as follows in Table 4:

[0120] Table 4. Batch-to-batch quality stability test results

[0121]

[0122] As shown in the table, compared with the comparative example, the standard deviation and the coefficient of variation of the whiteness and the degree of substitution of the product produced according to the technical solution provided in example 3 for 5 consecutive batches are lower, which indicates that the batch-to-batch quality stability is good.

[0123] The above is only an embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. The present application can have various changes and variations for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the technical idea and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A low cost process for the preparation of sodium carboxymethylcellulose, characterized in that, The preparation method comprises the following steps of: taking bamboo pulp, refined cotton and wood pulp as fiber raw materials, and performing alkalization, etherification and neutralization to obtain the product. The mass fraction of the bamboo pulp in the fiber raw materials is 10-50%, the mass fraction of the wood pulp is 10-50%, and the mass fraction of the refined cotton is 10-50%. The alkali liquor needs to be pretreated before being used for alkalization, and the pretreatment steps are as follows: The pretreated alkali liquor is obtained by mixing ethanol, isopropyl alcohol, soft water and sodium hydrosulfite, adding a sodium hydroxide solution, heating to 70-80 DEG C and keeping for 30-50 min, then cooling to 40-50 DEG C and keeping for 20-30 min, and finally cooling to room temperature; the mass ratio of the ethanol, isopropyl alcohol, soft water, sodium hydrosulfite, sodium hydroxide solution is (28-35):(35-42):(2-5):(0.12-0.15):(7-12). In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents.

2. A process for the low cost preparation of sodium carboxymethyl cellulose according to claim 1, characterized in that, In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents.

3. A process for the low cost preparation of sodium carboxymethyl cellulose as claimed in claim 1, wherein, In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents.

4. A process for the low cost preparation of sodium carboxymethyl cellulose as claimed in claim 1, wherein, In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents.

5. A process for the low cost preparation of sodium carboxymethylcellulose according to any one of claims 1 to 4, characterized in that, In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium carbonate and chloroacetic acid are used as etherification agents. In the etherification process, sodium chloroacetate is used as an etherification agent, or sodium

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