CN114645478B - Preparation method of refined cotton and cellulose ether - Google Patents

Abstract

A preparation method of refined cotton and cellulose ether belongs to the technical field of plant fiber processing. The preparation method is characterized by comprising the following preparation steps: crushing, removing impurities, decoloring and steaming; the impurity removal is to wash the plant fiber powder with an organic solvent to remove impurities. Adding alkali, solvent and etherifying agent into the refined cotton to carry out etherification reaction; and rinsing after the etherification reaction is finished to obtain the cellulose ether. According to the invention, the crushed plant fibers are dissolved with the organic solvent to dissolve impurities, and the organic solvent is used for dissolving impurities of natural plant fibers and breaking the primary wall. The organic solvent containing impurities generated in the process is easier to separate from the impurities, and the separated organic solvent can be reused without generating alkaline and salt-containing sewage.

Description

Preparation method of refined cotton and cellulose ether

Technical Field

A preparation method of refined cotton and cellulose ether belongs to the technical field of plant fiber processing.

Background

The basic steps of the conventional cellulose ether preparation process are: cooking, bleaching, crushing, etherification and rinsing. Wherein the cooking process is to heat the fiber to more than 100 ℃ in alkali liquor under pressure for reaction; the fiber material after steaming and bleaching is crushed. Wherein, the fiber after being steamed needs to be subjected to operations such as heating, rinsing, cooling, liquid removal and the like for a plurality of times in order to avoid the influence of alkali liquor on the bleaching process. In order to avoid the bleaching agent corroding the pulverizer, the bleached fiber material is subjected to operations such as heating, rinsing, cooling, liquid removal and the like for a plurality of times, so that etherification reaction can be carried out after pulverization. The repeated operations of steaming, bleaching, rinsing, dewatering and the like in the traditional cellulose ether preparation process not only greatly prolongs the production procedures, but also ensures that the cellulose ether preparation efficiency can not be greatly improved. Moreover, a large amount of alkaline sewage and salt sewage are generated in the process; the alkali liquor consumption is large, the energy consumption is high, and the production and sewage treatment costs are high.

Disclosure of Invention

The invention aims to solve the technical problems that: overcomes the defects of the prior art and provides a preparation method of refined cotton and cellulose ether with short working procedure, less sewage and low energy consumption.

The technical scheme adopted for solving the technical problems is as follows: the preparation method of the refined cotton comprises the following steps: crushing, removing impurities, decoloring and steaming; the impurity removal is to wash the plant fiber powder with an organic solvent to remove impurities.

According to the invention, the crushed plant fibers are dissolved with the organic solvent to dissolve impurities, and the organic solvent is used for dissolving impurities of natural plant fibers and breaking the primary wall. The organic solvent containing impurities generated in the process is easier to separate from the impurities, and the separated organic solvent can be reused without generating alkaline and salt-containing sewage.

Preferably, the plant fiber powder is obtained by crushing short cotton linters.

Preferably, the crushing is to crush the plant fiber raw material into plant fiber powder with the particle size of 50-500 meshes. The smaller and finer the particle diameter of the pulverized plant fiber powder, the smaller the energy consumption and the shorter the time required for dissolving the impurities.

Preferably, the crushing is performed by simultaneously adding the plant fiber raw material and the organic solvent into a wet crusher for wet crushing. The organic solvent needed in the impurity removal process is mixed with the fiber raw material in advance, wet crushing is carried out, fiber slurry is obtained, the organic solvent is directly supplemented in the fiber slurry, and the impurity removal concentration is reduced. After wet crushing, overheat and dust can not be generated in the crushing process, the noise is smaller, the production is safer, the dust pollution is avoided, and the operation environment is optimized.

Preferably, the vegetable fiber powder is washed by an organic solvent to remove impurities, the vegetable fiber powder and the organic solvent are mixed according to the mass ratio of 1:2-10, and then stirred for 20-120 minutes at 25-60 ℃, and then solid-liquid separation is carried out. The impurity removing process is a process of dissolving pectin, wax and other impurities by a solvent, the required temperature of the process is related to the proportion and the particle size of the crushed fibers, but the energy consumption of the impurity removing process is far lower than that of the traditional steaming process due to the obvious difference of specific heat of a medium and the required conditions. And the organic solvent containing impurities, which is separated after solid-liquid separation, can be directly concentrated, condensed and recovered, and the impurities are left in a concentration tank to be separated from the solvent without sewage treatment. The fiber after impurity removal can also be steamed to recover the solvent to obtain a dried semi-finished product, so that the subsequent treatment and transportation are convenient.

Preferably, the organic solvent is acetone, petroleum ether or No. six solvent naphtha. The preferable organic solvents not only can be dissolved and removed more easily for impurities in the plant fiber, but also can be concentrated and recovered conveniently.

Preferably, the decoloring is to adsorb impurities and pigments by using activated carbon. The invention uses active carbon to remove pigment, which is used to replace the bleaching with oxidant. The operation is more convenient, and no pungent smell is generated in the reaction process of the oxidant. The preferred process of decolorizing with activated carbon is to directly put the activated carbon in the organic solvent of the impurity removal step, and to decolorize while removing the impurities. In addition, after the vegetable fiber is subjected to impurity removal, the vegetable fiber can be soaked in water or other solvents, and then activated carbon is added to adsorb and decolorize.

Preferably, the decoloring step is completed at 20-90 ℃. The activated carbon in different solvents has different decolorizing efficiency, and can complete the decolorization in a shorter time at a lower temperature in a preferred organic solvent (acetone, petroleum ether or solvent oil six). In other solvents such as water, the decolorization needs to be accomplished under heating at approximately 90 ℃.

Preferably, the activated carbon is an activated carbon briquette or an activated carbon bag. The activated carbon is in the form of activated carbon briquettes or activated carbon bags and contacts with plant fiber powder in a solvent, and can be easily separated after decolorization is completed.

Preferably, the activated carbon is placed in a drum. The activated carbon is placed in a traditional purified cotton washing drum, the decoloring process is convenient and thorough, and the separation is convenient after the decoloring is finished.

A method for preparing cellulose ether, comprising the steps of:

1) Adding alkali into the refined cotton obtained by the preparation method to enable the mass concentration of alkali liquor in a system to be 45% -70%, and adding a solvent and an etherifying agent to carry out etherification reaction;

2) Rinsing: and (3) after the etherification reaction is finished, carrying out solid-liquid separation to obtain solid and liquid, and rinsing the solid separated from the solid-liquid.

The refined cotton obtained by the invention is normally subjected to subsequent etherification and rinsing to obtain cellulose ether.

Compared with the prior art, the preparation method of the purified cotton and the cellulose ether has the following beneficial effects: the preparation method replaces the traditional steaming and rinsing, and simultaneously improves the efficiency of each step and reduces the energy consumption, so the whole production efficiency is greatly improved. According to the invention, the crushed plant fibers are dissolved with the organic solvent to dissolve impurities, and the organic solvent is used for dissolving impurities of natural plant fibers and breaking the primary wall. The organic solvent containing impurities generated in the process is easier to separate from the impurities, and the separated organic solvent can be reused without generating alkaline and salt-containing sewage. Compared with the traditional preparation method, the preparation method has the advantages that the time required by the preparation method is shortened by 20% -30% under the condition of the same yield. In addition, the reaction conditions of each step in the preparation method can be carried out under milder conditions, and the energy consumption required by a batch of cellulose ether with the same yield is only 50% -60% of that required by the traditional preparation method.

Detailed Description

The present invention will be further illustrated with reference to specific examples in which the preparation of carboxymethyl cellulose is taken as an example for the convenience of comparison between examples and comparative examples, because the present invention is not modified for the step of etherification, and the reaction materials and reaction conditions of the etherification may still follow the conditions of the conventional preparation method. Wherein example 1 is the best practice.

Example 1

1) Crushing: adding short cotton linters and petroleum ether into a wet pulverizer at the same time, and pulverizing the fiber material to a particle size of 500 meshes to obtain fiber slurry, wherein the ratio of the short cotton linters to the petroleum ether is 1:1;

2) Removing impurities and decoloring: the mass ratio of petroleum ether to petroleum ether and short cotton linters in step 1) is 10:1, simultaneously adding an activated carbon briquette accounting for 10% of the mass of short cotton linters into a washing drum; stirring at 25℃for 20 min; removing impurities and decoloring at the same time; removing impurities and decoloring, and taking out the activated carbon block; carrying out solid-liquid separation on the rest materials, concentrating the separated liquid, condensing the concentrated steam to recover petroleum ether, further drying the concentrated slag to recover petroleum ether, and intensively burning the dried slag as boiler fuel;

3) Steaming and removing: the solid separated during the solid-liquid separation is distilled off by a distilled off machine to recycle petroleum ether to obtain refined cotton;

4) Etherification: adding the refined cotton obtained in the step 3) into alkali liquor with the mass concentration of 60%, adding solvent and sodium acetate chloride serving as an etherifying agent which is 1.2 times of the mass of the fiber micro powder at the temperature of 23 ℃ for etherification reaction;

5) Rinsing: and (3) after the etherification reaction is finished, carrying out solid-liquid separation, rinsing the solid subjected to the solid-liquid separation to obtain carboxymethyl cellulose, directly cooling the water phase of the liquid subjected to the solid-liquid separation after desolventizing to 0 ℃, carrying out solid-liquid separation to obtain NaOH with the purity of 98% and a mixed solution, and concentrating and crystallizing the mixed solution to realize desalination. In this example, the steam consumption per ton of carboxymethyl cellulose produced was 2.2 tons, the electricity consumption was 866 degrees, the cellulose yield was 1.24% (calculated as gossypol), the viscosity of the 2% aqueous solution of the carboxymethyl cellulose obtained was 3765 mPa.s, and the ash content was 0.94%.

Example 2

1) Crushing: adding short cotton linters and petroleum ether into a wet pulverizer at the same time, and pulverizing the fiber material to a particle size of 300 meshes to obtain fiber slurry, wherein the ratio of the short cotton linters to the petroleum ether is 1:0.5;

2) Removing impurities and decoloring: the mass ratio of petroleum ether to petroleum ether and short cotton linters in step 1) is 8:1, simultaneously adding an activated carbon briquette accounting for 12% of the mass of short cotton linters into a washing drum; stirring at 25℃for 22 min; removing impurities and decoloring at the same time; removing impurities and decoloring, and taking out the activated carbon block; carrying out solid-liquid separation on the rest materials, concentrating the separated liquid, condensing the concentrated steam to recover petroleum ether, further drying the concentrated slag to recover petroleum ether, and intensively burning the dried slag as boiler fuel;

3) Steaming and removing: the solid separated during the solid-liquid separation is distilled off by a distilled off machine to recycle petroleum ether to obtain refined cotton;

4) Etherification: adding the refined cotton obtained in the step 3) into alkali liquor with the mass concentration of 55%, adding a solvent and sodium monochloroacetate serving as an etherifying agent which is 0.8 times of the mass of the fiber micropowder at 25 ℃ for etherification reaction;

5) Rinsing: and (3) after the etherification reaction is finished, carrying out solid-liquid separation, rinsing the solid subjected to the solid-liquid separation to obtain carboxymethyl cellulose, directly cooling the water phase of the liquid subjected to the solid-liquid separation after desolventizing to 0 ℃, carrying out solid-liquid separation to obtain NaOH with the purity of 98% and a mixed solution, and concentrating and crystallizing the mixed solution to realize desalination. In this example, the steam consumption per ton of carboxymethyl cellulose produced was 2.3 tons, the electricity consumption was 912 degrees, the cellulose yield was 1.17% (calculated as gossypol), the viscosity of the 2% aqueous solution of the carboxymethyl cellulose obtained by sampling measurement was 3463 mPa.s, and the ash content was 0.97%.

Example 3

1) Crushing: adding short cotton linters and No. 6 solvent oil into a wet pulverizer at the same time, and pulverizing the fiber material to a particle size of 100 meshes to obtain fiber slurry, wherein the ratio of the short cotton linters to the No. 6 solvent oil is 1:0.8;

2) Removing impurities and decoloring: supplementing No. 6 solvent oil to the mass ratio of No. 6 solvent oil to the short cotton linters in step 1) is 9:1, simultaneously adding an activated carbon bag with the mass of 9% of that of short cotton linters into a washing drum; stirring at 30℃for 20 min; removing impurities and decoloring at the same time; taking out the activated carbon bag after removing impurities and decoloring; carrying out solid-liquid separation on the rest materials, concentrating the separated liquid, condensing the concentrated steam to recover No. 6 solvent oil, further drying the concentrated slag to recover No. 6 solvent oil, and intensively burning the dried slag as boiler fuel;

3) Steaming and removing: the solid separated during the solid-liquid separation is distilled off by a distilled off machine to recover No. 6 solvent oil, and refined cotton is obtained;

4) Etherification: adding the refined cotton obtained in the step 3) into alkali liquor with the mass concentration of 45%, adding a solvent and sodium monochloroacetate serving as an etherifying agent which is 1.1 times of the mass of the fiber micropowder at the temperature of 30 ℃ for etherification reaction;

5) Rinsing: and (3) after the etherification reaction is finished, carrying out solid-liquid separation, rinsing the solid subjected to the solid-liquid separation to obtain carboxymethyl cellulose, directly cooling the water phase of the liquid subjected to the solid-liquid separation after desolventizing to 0 ℃, carrying out solid-liquid separation to obtain NaOH with the purity of 98% and a mixed solution, and concentrating and crystallizing the mixed solution to realize desalination. In this example, the steam consumption per ton of carboxymethyl cellulose produced was 2.2 tons, the electricity consumption was 902 degrees, the cellulose yield was 1.34% (calculated as gossypol), the viscosity of the 2% aqueous solution of the carboxymethyl cellulose obtained by sampling measurement was 3196 mPa.s, and the ash content was 0.99%.

Example 4

1) Crushing: adding short cotton velvet and acetone into a wet pulverizer at the same time, and pulverizing the fiber material to a particle size of 200 meshes to obtain fiber slurry, wherein the ratio of the short cotton velvet to the acetone is 1:0.4;

2) Removing impurities and decoloring: the mass ratio of the acetone supplement to the short cotton linters in step 1) was 5:1, adding an active carbon bag with 13% of short cotton velvet mass at the same time; stirring at 25℃for 20 min; removing impurities and decoloring at the same time; filtering out the activated carbon bag by using a filter screen after removing impurities and decoloring; carrying out solid-liquid separation on the rest materials, concentrating the separated liquid, condensing the concentrated steam to recover acetone, further drying the concentrated slag to recover petroleum ether, and intensively burning the dried slag as boiler fuel;

3) Steaming and removing: the solid separated during the solid-liquid separation is distilled off by a distilled off machine to recycle acetone to obtain refined cotton;

4) Etherification: adding the refined cotton obtained in the step 3) into alkali liquor with the mass concentration of 70%, adding a solvent and sodium monochloroacetate serving as an etherifying agent which is 1.5 times of the mass of the fiber micropowder at the temperature of 40 ℃ for etherification reaction;

5) Rinsing: and (3) after the etherification reaction is finished, carrying out solid-liquid separation, rinsing the solid subjected to the solid-liquid separation to obtain carboxymethyl cellulose, directly cooling the water phase of the liquid subjected to the solid-liquid separation after desolventizing to 0 ℃, carrying out solid-liquid separation to obtain NaOH with the purity of 98% and a mixed solution, and concentrating and crystallizing the mixed solution to realize desalination. In this example, the steam consumption per ton of carboxymethyl cellulose produced was 2.7 tons, the electricity consumption was 976 degrees, the cellulose yield was 1.28% (calculated as gossypol), the viscosity of the 2% aqueous solution of the carboxymethyl cellulose obtained was 3234 mPa.s, and the ash content was 0.96%.

Example 5

1) Crushing: crushing short cotton linters to a particle size of 50 meshes to obtain fiber powder;

2) Removing impurities: mixing methanol with the fiber powder in the step 1) according to the mass ratio of 2:1, stirring at 60 ℃ for 120 minutes; carrying out solid-liquid separation on the materials, concentrating the separated liquid, condensing the concentrated steam to recover petroleum ether, further drying the concentrated slag to recover petroleum ether, and intensively burning the dried slag as boiler fuel;

3) Steaming and removing: the solid separated during the solid-liquid separation is distilled off by a distilled off machine to recycle petroleum ether;

4) Decoloring: adding water and activated carbon briquettes accounting for 10% of the mass of the short cotton linters into a washing drum; stirring at 90 ℃ for 120 minutes to decolorize; taking out the activated carbon block after the decoloring is finished; solid-liquid separation is carried out on the residual materials, and the separated solids are dried to obtain refined cotton;

5) Etherification: adding the refined cotton obtained in the step 4) into alkali liquor with the mass concentration of 70%, adding a solvent and sodium monochloroacetate serving as an etherifying agent which is 1.2 times of the mass of the fiber micropowder at the temperature of 23 ℃ for etherification reaction;

6) Rinsing: and (3) after the etherification reaction is finished, carrying out solid-liquid separation, rinsing the solid subjected to the solid-liquid separation to obtain carboxymethyl cellulose, directly cooling the water phase of the liquid subjected to the solid-liquid separation after desolventizing to 0 ℃, carrying out solid-liquid separation to obtain NaOH with the purity of 98% and a mixed solution, and concentrating and crystallizing the mixed solution to realize desalination. In this example, the steam consumption per ton of carboxymethyl cellulose produced was 6.7 tons, the electricity consumption was 1368 degrees, the cellulose yield was 1.21% (calculated as gossypol), the viscosity of the 2% aqueous solution of the carboxymethyl cellulose obtained by sampling measurement was 2964 mPa.s, and the ash content was 1.05%.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the invention in any way, and any person skilled in the art may make modifications or alterations to the disclosed technical content to the equivalent embodiments. However, any simple modification, equivalent variation and variation of the above embodiments according to the technical substance of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims (4)

1. The preparation method of the purified cotton is characterized by comprising the following steps: crushing, removing impurities, decoloring and steaming; the impurity removal is to wash the plant fiber powder with an organic solvent to remove impurities;

the method comprises the steps of washing plant fiber powder with an organic solvent to remove impurities, mixing the plant fiber powder with the organic solvent according to a mass ratio of 1:2-10, stirring for 20-120 minutes at 25-60 ℃, and then carrying out solid-liquid separation;

the organic solvent is acetone, petroleum ether or No. six solvent naphtha;

the decolorization is to adsorb impurities and pigment by using active carbon;

the decolorization is completed at 20-90 ℃;

the activated carbon is an activated carbon briquette or an activated carbon bag;

the activated carbon is arranged in the washing drum.

2. A process for producing purified cotton as defined in claim 1, wherein: the crushing is to crush the plant fiber raw material into plant fiber powder with the particle size of 50-500 meshes.

3. A process for producing purified cotton as defined in claim 1, wherein: the crushing is to add the plant fiber raw material and the organic solvent into a wet crusher simultaneously for wet crushing.

4. A method for preparing cellulose ether, comprising the steps of:

1) Adding alkali into refined cotton obtained by the preparation method of any one of claims 1-3 to enable the mass concentration of alkali liquor in a system to be 45% -70%, and adding a solvent and an etherifying agent to carry out etherification reaction;

2) Rinsing: and (3) after the etherification reaction is finished, carrying out solid-liquid separation to obtain solid and liquid, and rinsing the solid separated from the solid-liquid.