CN114645478A - Preparation method of purified cotton and cellulose ether - Google Patents

Abstract

A preparation method of purified 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 by using 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. The invention dissolves impurities in the crushed plant fibers by using an organic solvent, and the organic solvent dissolves the impurities in the natural plant fibers and breaks 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 the wastewater containing alkali and salt.

Description

Preparation method of purified cotton and cellulose ether

Technical Field

A preparation method of purified cotton and cellulose ether, belonging to the technical field of plant fiber processing.

Background

The basic steps of a conventional cellulose ether preparation process are: cooking, bleaching, crushing, etherification and rinsing. Wherein the cooking process is to heat the fiber in alkali liquor to over 100 ℃ for reaction; the fiber material after cooking and bleaching is subjected to a crushing process. Wherein the boiled fiber needs to be subjected to multiple operations of temperature rise, rinsing, temperature reduction, liquid removal and the like to avoid the influence of alkali liquor on the bleaching process. In order to avoid the bleaching agent from corroding the crusher, the bleached fiber material is subjected to multiple operations of temperature rise, rinsing, temperature reduction, liquid removal and the like, so that the etherification reaction can be carried out after the fiber material is crushed. The operations of steaming, bleaching, rinsing, liquid removal and the like which are continuously repeated in the traditional preparation process of the cellulose ether not only greatly prolong the production process, but also can not greatly improve the preparation efficiency of the cellulose ether. Moreover, a large amount of alkali-containing sewage and salt-containing sewage are generated in the process; resulting in large dosage of alkali liquor, high energy consumption and high production and sewage treatment costs.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: overcomes the defects of the prior art and provides a preparation method of refined cotton and cellulose ether with short process, less sewage and low energy consumption.

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

The invention dissolves impurities in the crushed plant fibers by using an organic solvent, and the organic solvent dissolves the impurities in the natural plant fibers and breaks 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 the wastewater containing alkali and salt.

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

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

Preferably, the pulverization is wet pulverization by adding the plant fiber raw material and the organic solvent into a wet pulverizer at the same time. Mixing the organic solvent which is needed in the impurity removal process with the fiber raw material in advance, carrying out wet crushing to obtain fiber slurry, and directly supplementing the organic solvent in the fiber slurry to reduce the impurity removal concentration. After the wet crushing is adopted, overheating and dust cannot be generated in the crushing process, the noise is lower, the production is safer, no dust pollution exists, 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, stirred for 20-120 minutes at the temperature of 25-60 ℃, and then subjected to solid-liquid separation. The impurity removing process is firstly a process of dissolving impurities such as pectin, wax and the like by a solvent, the temperature required by the process is related to the mixture ratio and the particle size of the crushed fiber, but the energy consumption required by the impurity removing process is far lower than that of the traditional steaming process due to the obvious difference between the specific heat of a medium and the required conditions. And the organic solvent containing impurities separated after solid-liquid separation can be directly concentrated and condensed for recovery, and the impurities are remained in a concentration tank to be separated from the solvent without sewage treatment. The fiber after impurity removal can also be evaporated to recover the solvent to obtain a dry semi-finished product, so that the subsequent treatment and transportation are facilitated.

Preferably, the organic solvent is acetone, petroleum ether or solvent oil six. The preferred organic solvents not only can dissolve and remove impurities in the plant fibers more easily, but also are convenient for concentration and recovery.

Preferably, the decolorization is adsorption of impurities and pigments by using activated carbon. The invention uses active carbon to remove pigment to replace the oxidant for bleaching. The operation is more convenient, and no pungent smell is generated in the reaction process of the oxidant. Preferably, the activated carbon is directly placed in the organic solvent in the impurity removal step by using the activated carbon decolorization process, and decolorization is carried out while impurity removal is carried out. In addition, the plant fiber can be soaked in water or other solvents after the plant fiber is subjected to impurity removal, and then activated carbon is added to adsorb and decolor.

Preferably, the decolorization step is carried out at 20 ℃ to 90 ℃. The efficiency of activated carbon for decolorization varies among solvents, and decolorization can be accomplished in a shorter time and at a lower temperature in the preferred organic solvent (acetone, petroleum ether, or solvent oil six). In other solvents such as water, the decolorization needs to be accomplished under heating conditions close to 90 ℃.

Preferably, the activated carbon is activated carbon briquettes or activated carbon bales. The activated carbon is in contact with the plant fiber powder in a solvent in the form of activated carbon briquettes or activated carbon packets, and can be easily separated after decolorization is finished.

Preferably, the activated carbon is placed in a washing 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 of any one of claims 1 to 9 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 after the etherification reaction is finished, carrying out solid-liquid separation to obtain solid and liquid, and rinsing the solid obtained by the solid-liquid separation.

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

Compared with the prior art, the preparation method of the purified cotton and the cellulose ether has the beneficial effects that: the preparation method of the invention replaces the traditional cooking and rinsing, and meanwhile, the efficiency of each step is improved, and the energy consumption is reduced, so the integral production efficiency is greatly improved. The invention dissolves impurities in the crushed plant fibers by using an organic solvent, and the organic solvent dissolves the impurities in the natural plant fibers and breaks 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 the wastewater containing alkali and salt. Compared with the traditional preparation method, the time required by the method is shortened by 20-30% under the condition of the same yield. In addition, in the preparation method, because the reaction conditions of the steps can be carried out under milder conditions, the energy consumption required by a batch of cellulose ether with the same yield is only 50-60% of the energy consumption required by the traditional preparation method.

Detailed Description

The present invention will be further described with reference to specific examples, wherein carboxymethyl cellulose is prepared for comparison between examples and comparative examples, since the present invention is not adjusted for the step of etherification, and the reaction raw materials and reaction conditions for etherification can still follow the conditions of conventional preparation methods. With example 1 being the best practice.

Example 1

1) Crushing: adding short cotton linter and petroleum ether into a wet grinder simultaneously, grinding the fiber material to a particle size of 500 meshes to obtain fiber slurry, wherein the ratio of the short cotton linter to the petroleum ether is 1: 1;

2) removing impurities and decoloring: supplementing petroleum ether until the mass ratio of the petroleum ether to the short linter in the step 1) is 10: 1, simultaneously adding an activated carbon briquette with the mass of 10 percent of short linters into a washing drum; stirring at 25 ℃ for 20 minutes; removing impurities and simultaneously decoloring; taking out the activated carbon block after impurity removal and decoloration are completed; carrying out solid-liquid separation on the residual materials, concentrating the separated liquid, condensing the concentrated steam to recover petroleum ether, further drying the concentrated slag to recover the petroleum ether, and intensively burning the dried slag as boiler fuel;

3) steaming and removing: the separated solid is evaporated and recovered with an evaporator to obtain refined cotton;

4) etherification: adding the refined cotton obtained in the step 3) into an alkali liquor with the mass concentration of 60%, and adding a solvent and an etherifying agent sodium monochloroacetate with the mass of 1.2 times that of the fiber micro powder at 23 ℃ to carry out etherification reaction;

5) rinsing: and after the etherification reaction is finished, carrying out solid-liquid separation, rinsing solid obtained by the solid-liquid separation to obtain carboxymethyl cellulose, directly cooling the water phase obtained by the solid-liquid separation to 0 ℃ after the water phase obtained by the solid-liquid separation is subjected to desolventization, carrying out solid-liquid separation to obtain NaOH and a mixed solution with the purity of 98%, and concentrating and crystallizing the mixed solution to realize desalination. In the embodiment, the steam consumption of each ton of carboxymethyl cellulose is 2.2 tons, the electricity consumption is 866 degrees, the cellulose yield is 1.24 percent (calculated by gossypol), and the viscosity of the 2 percent aqueous solution of the obtained carboxymethyl cellulose is 3765 mPas by sampling and measuring, and the ash content is 0.94 percent.

Example 2

1) Crushing: adding short linter and petroleum ether into a wet grinder simultaneously, grinding the fiber material to a particle size of 300 meshes to obtain fiber slurry, wherein the ratio of the short linter to the petroleum ether is 1: 0.5;

2) removing impurities and decoloring: supplementing petroleum ether to the mass ratio of the petroleum ether to the short linter in the step 1) is 8: 1, simultaneously adding an activated carbon briquette with the mass of 12 percent of short linters into a washing drum; stirring at 25 ℃ for 22 minutes; removing impurities and simultaneously decoloring; taking out the activated carbon block after impurity removal and decoloration are completed; carrying out solid-liquid separation on the residual materials, concentrating the separated liquid, condensing the concentrated steam to recover petroleum ether, further drying the concentrated slag to recover the petroleum ether, and intensively burning the dried slag as boiler fuel;

3) steaming and removing: the separated solid is evaporated and recovered with an evaporator to obtain refined cotton;

4) etherification: adding the refined cotton obtained in the step 3) into an alkali liquor with the mass concentration of 55%, and adding a solvent and an etherifying agent sodium monochloroacetate with the mass of 0.8 time that of the fiber micro powder at 25 ℃ to carry out etherification reaction;

5) rinsing: and after the etherification reaction is finished, carrying out solid-liquid separation, rinsing solid obtained by the solid-liquid separation to obtain carboxymethyl cellulose, directly cooling the water phase obtained by the solid-liquid separation to 0 ℃ to obtain NaOH and a mixed solution with the purity of 98% by the solid-liquid separation, and concentrating and crystallizing the mixed solution to realize desalination. In the embodiment, the steam consumption of each ton of carboxymethyl cellulose is 2.3 tons, the electricity consumption is 912 degrees, the cellulose yield is 1.17 percent (calculated by gossypol), and the viscosity of the 2 percent aqueous solution of the obtained carboxymethyl cellulose is 3463 mPas by sampling and measuring, and the ash content is 0.97 percent.

Example 3

1) Crushing: adding short linter and No. 6 solvent oil into a wet grinder simultaneously, grinding fiber materials to the particle size of 100 meshes to obtain fiber slurry, wherein the ratio of the short linter to the No. 6 solvent oil is 1: 0.8;

2) removing impurities and decoloring: supplementing No. 6 solvent oil until the mass ratio of No. 6 solvent oil to the short linter in the step 1) is 9: 1, simultaneously adding an activated carbon bag with the mass of 9 percent of short linter into a washing drum; stirring for 20 minutes at 30 ℃; removing impurities and simultaneously decoloring; taking out the activated carbon bag after impurity removal and decoloration are completed; carrying out solid-liquid separation on the residual 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 burning the dried slag serving as boiler fuel in a centralized manner;

3) steaming and removing: the separated solid is evaporated and removed by a desolventizer-toaster to recover No. 6 solvent oil, and then refined cotton is obtained;

4) etherification: adding the refined cotton obtained in the step 3) into an alkali liquor with the mass concentration of 45%, and adding a solvent and an etherifying agent sodium monochloroacetate with the mass of 1.1 times that of the fiber micro powder at 30 ℃ to carry out etherification reaction;

5) rinsing: and after the etherification reaction is finished, carrying out solid-liquid separation, rinsing solid obtained by the solid-liquid separation to obtain carboxymethyl cellulose, directly cooling the water phase obtained by the solid-liquid separation to 0 ℃ after the water phase obtained by the solid-liquid separation is subjected to desolventization, carrying out solid-liquid separation to obtain NaOH and a mixed solution with the purity of 98%, and concentrating and crystallizing the mixed solution to realize desalination. In the present example, the steam consumption for each ton of carboxymethyl cellulose production is 2.2 tons, the electricity consumption is 902 degrees, the cellulose yield is 1.34% (calculated by gossypol), and the viscosity of the 2% aqueous solution of the carboxymethyl cellulose is 3196 mPas and the ash content is 0.99% by sampling and measuring.

Example 4

1) Crushing: adding short cotton linters and acetone into a wet grinder simultaneously, and grinding fiber materials to obtain fiber slurry with the particle size of 200 meshes, wherein the ratio of the short cotton linters to the acetone is 1: 0.4;

2) removing impurities and decoloring: supplementing acetone until the mass ratio of the acetone to the short cotton linter in the step 1) is 5: 1, simultaneously adding an active carbon bag with the mass of 13 percent of short linters; stirring at 25 ℃ for 20 minutes; removing impurities and simultaneously decoloring; filtering out the activated carbon bag by using a filter screen after impurity removal and decoloration are finished; carrying out solid-liquid separation on the residual 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 evaporated by a desolventizer-toaster to recover 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 of which the mass is 1.5 times that of the fiber micro powder at 40 ℃, and carrying out etherification reaction;

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

Example 5

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

2) removing impurities: mixing methanol and the fiber powder obtained in the step 1) according to a mass ratio of 2: 1, stirring for 120 minutes at 60 ℃; performing 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 the petroleum ether, and burning the dried slag serving as boiler fuel in a centralized manner;

3) steaming and removing: the solid separated in the solid-liquid separation is evaporated and removed by a desolventizer-toaster to recover petroleum ether;

4) and (3) decoloring: adding water and activated carbon briquettes with the mass of 10% of short linters into the washing drum; stirring for 120 minutes at 90 ℃ for decolorization; taking out the activated carbon block after the decoloration is finished; carrying out solid-liquid separation on the residual materials, and drying the separated solids 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 which is 1.2 times of the mass of the fiber micro powder at 23 ℃, and carrying out etherification reaction;

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

The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.

Claims (10)

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

2. The method for producing purified cotton according to claim 1, wherein: the crushing is to crush the plant fiber raw material into plant fiber powder of 50-500 meshes.

3. The method for producing purified cotton according to claim 1, wherein: the crushing is to add the plant fiber raw material and the organic solvent into a wet crusher for wet crushing.

4. The method for producing purified cotton according to claim 1, wherein: the plant fiber powder is washed by an organic solvent to remove impurities, the plant fiber powder and the organic solvent are mixed according to the mass ratio of 1: 2-10, stirred for 20-120 minutes at the temperature of 25-60 ℃, and then solid-liquid separation is carried out.

5. The method of producing purified cotton according to claim 1 or 3, wherein: the organic solvent is acetone, petroleum ether or No. six solvent oil.

6. The method for producing purified cotton according to claim 1, wherein: the decolorization is to use activated carbon to adsorb impurities and pigments.

7. The method for producing purified cotton according to claim 6, wherein: the decolorization is completed at 20-90 ℃.

8. The method for producing refined cotton according to claim 6, wherein: the active carbon is active carbon pressed block or active carbon bag.

9. The method for producing purified cotton according to claim 6, wherein: the activated carbon is placed in the drum washer.

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

1) adding alkali into the refined cotton obtained by the preparation method of any one of claims 1 to 9 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 after the etherification reaction is finished, carrying out solid-liquid separation to obtain solid and liquid, and rinsing the solid obtained by the solid-liquid separation.