KR100461564B1 - A method for preparing cellulose ether - Google Patents

Abstract

The present invention relates to a method for producing cellulose ether, and more particularly, to soften finely ground substrate pulp to soften cellulose, to etherify, and then spray hot water and steam in a rotating filter to continuously wash and filter the salt. By improving the process to perform the grinding and drying at the same time after removal of the cellulose, it can save energy and shorten the time required for the process, improve the efficiency of salt removal, and reduce the amount of waste water generated. It relates to a manufacturing method of.

Description

Method for preparing cellulose ether {A method for preparing cellulose ether}

The present invention relates to a method for producing cellulose ether, and more particularly, to soften finely ground substrate pulp to soften cellulose, to etherify, and then spray hot water and steam in a rotating filter to continuously wash and filter the salt. By improving the process to perform the grinding and drying at the same time after removal of the cellulose, it can save energy and shorten the time required for the process, improve the efficiency of salt removal, and reduce the amount of waste water generated. It relates to a manufacturing method of.

Cellulose ether refers to alkyl cellulose, hydroxyalkyl cellulose, hydroxyalkyl alkyl cellulose, and the like, and is an industrially very useful compound used as a thickener, binder, repair agent, and the like in medicine, construction, and paint.

In the process of preparing cellulose ether, in order to react the cellulose with the etherification agent, it is necessary to weaken the crystalline structure of the hard cellulose, so that an alkali in a solid or aqueous solution may be used. The alkali is an alkali metal hydroxide (caustic soda). ) Are generally used, and specifically, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like can be used. The caustic soda not only acts as a catalyst in the reaction between the etherification agent and cellulose, but also serves to help various chemicals bind or react by binding with cellulose to expand the crystal structure.

However, since the cellulose ether slurry after the etherification reaction contains a large amount of by-product salts, a process for removing the salts was required.

That is, a large amount of hot water is added to the pressure filter to remove salts, the salts contained in the cellulose ether slurry are washed, and the generated wastewater is filtered. The conventional filtration method is about 15 times higher than the weight of the synthetic product. Washing and filtering the cellulose ether slurry with water was repeated once to twice.

However, the method is pointed out as a problem in the performance of the process because the time required to remove the water is excessively consumed, there is a problem that the removal efficiency and productivity of the salt is low compared to the amount of hot water and time consumed.

Conventionally known methods for producing cellulose ethers include the following methods.

According to U.S. Patent No. 4,477,657, 50 wt% caustic soda is treated in finely pulverized linter pulp, propylene oxide is continuously injected and then reacted, and methyl chloride is slowly infused for 2 hours, or 50 minutes in finely pulverized cotton linter After treating by weight% caustic soda, propylene oxide was injected and reacted for 30 minutes, then 50% by weight aqueous solution of caustic soda was injected, methyl chloride was reacted for 30 minutes, filtered and pulverized with a grinder to remove residual water. In order to do this, cellulose ether is obtained by drying.

However, the method is disadvantageous economically because it takes a lot of time, such as filtration, pulverization, drying after synthesis and a large amount of energy consumption per process.

In addition, according to US Pat. No. 4,661,589, 50% by weight of caustic soda solution was treated in a finely ground cotton printer, and then maintained for 15 minutes, and propylene oxide was continuously continuously injected slowly in a small amount in a vaporized state. Dilute the dimethyl ether slowly for 30 minutes, react for 30 minutes, add 50% by weight aqueous solution of caustic soda, inject a small amount of methyl chloride, react, filter, and grind with a grinder to remove residual water. Cellulose ether is obtained by drying.

However, the above method has a critical disadvantage that it is difficult to use commercially because the productivity is low due to the addition of a continuous injection process of the reactants, and the synthesis and grinding and drying processes require not only excessive synthesis time but also energy use.

In other words, the prior art uses a method of continuous injection of reactants very slowly, and because the production time is too long by going through the pulverization and drying process after synthesis, the energy is excessively consumed, and thus it is very economical, productive and commercial. Inefficient and decisive problems.

Therefore, the manufacturing process consists of several steps, excessive production time is consumed and energy consumption can be solved the conventional problems, which can increase productivity efficiently and develop cellulose ether manufacturing method excellent in salt removal efficiency. It was a situation.

Accordingly, the inventors of the present invention have made efforts to solve the above problems, and as a result, the cylindrical filter and the amount of hot water and steam, which can rotate the simple pressure filtration and washing processes used in the washing and filtration processes after cellulose ether synthesis, It has been found that the use of a pressure-controlled injector can be improved efficiently. In addition, it was found that the conventional pulverization and drying process can be carried out simultaneously using the hot air to perform the pulverization and drying separately, to complete the present invention.

Therefore, the present invention is introduced in the process of washing and filtration at the same time in the manufacture of cellulose ether and by shortening the manufacturing process by introducing a process for realizing the pulverization and drying at the same time to increase the productivity and at the same time improve the efficiency of salt removal and waste water It is an object of the present invention to provide a method for producing cellulose ether which is economically and environmentally advantageous by reducing the amount of generation.

The present invention provides a method for producing a cellulose ether which softens cellulose ether and then etherified cellulose ether slurry by hot water to remove salts, and then pulverizes and dryes the cellulose ether slurry. The cellulose ether slurry was repeatedly washed and filtered while the filtration cell was passed through hot water and steam injectors by rotating the cylindrical filter by inserting a plurality of rotating cylindrical filters and rotating the cylindrical filter to give the washed and filtered wet cellulose ether. The axis of rotation is 8,000 to 10,000 RPM, and the pulverization and drying are simultaneously carried out by transferring with hot air to a pulverizer rotating horizontally under conditions of a rotating speed of 1,500 to 3,500 RPM of a classifier. The process in which ether is transferred to the grinder The method of manufacturing the cellulose ether is carried out continuously in its features.

Referring to the present invention in more detail as follows.

In the present invention, the finely ground substrate pulp (cellulose) is alkali treated to soften cellulose, and then the etherified cellulose ether slurry is added to a rotatable filter, and the hot water and steam are repeatedly used by using a disperser. The present invention relates to a method for preparing cellulose ether, in which a salt is washed and the wastewater is filtered at the same time, and the resultant from which the salt is removed can be pulverized and dried simultaneously using hot air.

Referring to the manufacturing method of the cellulose ether according to the present invention step by step.

The first step is to soften the substrate cellulose.

Alkaline treatment is first performed to crush the cellulose used as the substrate finely and then weaken the crystalline structure of the cellulose so that the cellulose can be easily reacted with the etherifying agent to which the cellulose is added. Alkali metal hydroxide (caustic soda) in solid or aqueous solution, in particular in 50% aqueous solution, is preferably used for alkali treatment. Specifically, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like are used. . It is important to spray the caustic so that it is evenly dispersed in the cellulose, the alkali-treated activated alkali cellulose should be stirred at room temperature for a certain time to uniformly weaken the crystalline structure.

The second step is to prepare a cellulose ether slurry by adding an esterifying agent to the softened activated alkali cellulose.

Dilution gas is added to the active alkali cellulose and mixed evenly. Diluent gas used here includes dimethyl ether, dimethoxyethane, alkanol, alkanediol, or alkoxyalkanol.

Alkaline treated cellulose at the room temperature is in a state that can be easily combined with the reactants, and when the etherification agent is added to the ether and cellulose are efficiently bonded.

Alkylene oxides and alkyl halides are used as etherification agents, and alkylene oxides and alkyl halides are added and reacted at 50 to 60 DEG C, then heated to 80 to 90 DEG C, and reacted for 10 to 60 minutes. It is possible to prepare hydroxyalkylalkylcellulose, which is bound cellulose.

At this time, there is a difference in the treatment method of the alkali metal hydroxide that is performed to prepare a compound having a desired degree of substitution.

In the present invention, it is intended to develop the method so that the alkoxy substitution degree is 15 to 30% and the hydroxyalkoxy substitution degree is 5 to 25%. If the alkoxy substitution degree is less than 15%, there is almost no commercial utility. If more than%, there is a problem that the unique physical properties are not expressed or greatly improved, and if the degree of hydroxyalkoxy substitution is less than 5%, there is no meaning because commercial use is extremely thin and there is no advantageous property, and if it exceeds 25%, similar properties Since there is a problem that does not need to be increased to manufacture any more.

Hot water is added to the slurry produced by the reaction, stirred for about 10 minutes, and then transferred to a filter in order to undergo a washing and filtration process.

The third step is to remove the salt by washing the resulting slurry and to filter the filtered water (waste water).

In this step, the conventional batch filtration method is characterized by a continuous improvement, a cylindrical filter having a plurality of filter cells equipped with a filter network on the central rotation axis is used. After a certain amount of slurry is filled in the filtration cells, the amount of hot water is controlled, and after passing through the nozzle to be sprayed, the salt is washed while continuously passing through the nozzle to which steam is sprayed, and at the same time, the waste water is discharged.

The filter cell mounted in the cylindrical filter is rotating at 5 ~ 10 RPM, the slurry is contained by a certain amount. Boiling water is injected at a pressure of 2 kg / cm 2 from the primary nozzle, and steam is sprayed from the secondary nozzle to remove the salt. The nozzle is repeated several times and the filtered product exits the outlet at the first rotational completion point.

The fourth step is to grind and dry the filtered product.

The filtered product exited from the outlet in step 3 is transferred to the grinder via a transfer line, and then pulverized into a particle diameter range of several μm and moved from the inlet to the outlet according to the air flow. That is, the filtered product is introduced together with the hot air through a conveying line such as a conveyor. The rotation conditions of the grinder are 8,000 to 10,000 RPM of the main rotation axis, and the rotational speed of the classifier may be 1,500 to 3,500 RPM.

At this time, the hot air is introduced to induce the product to the outlet to be dried at the same time as grinding, and the product can be pulverized and dried at the same time without going through a separate drying process. Temperature control is important. The final product is subjected to the above grinding and drying process, and according to the present process, an additional effect of preventing the deterioration of the product that may occur during the grinding can be obtained.

The product washed and filtered in this way has a salt content of 1.0% or less relative to the dry product weight, and shows a superior effect compared to the conventional batch filtration method, which was unable to remove the salt content to 1% or less. By integrating washing and filtration, grinding and drying processes, the time required for the process can be significantly reduced.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by Examples.

Examples 1-4

8 kg of finely ground cellulose was added to a 100 L high-pressure reactor, and 10 kg of 50% caustic soda solution was sprayed to be uniformly dispersed in cellulose, and 8 kg of dimethyl ether was added as a diluent gas and mixed evenly.

1 kg of alkylene oxide and 8 kg of alkyl halide were added to the mixture to react at 50 to 60 ° C. for 30 minutes, and then heated to 80 to 90 ° C. for 60 minutes to prepare a hydroxyalkylalkylcellulose slurry. It was.

60 L of hot water was added to the slurry, stirred for 10 minutes, transferred to a filter cell in a cylindrical stirrer, and boiled water was sprayed twice at a pressure of 2 kg / ㎠ at the first nozzle and steam was sprayed at the second nozzle twice. After the salt was removed, the filtered product was transferred to the outlet at the first turn.

Hot air at 60 to 80 ° C flows through the conveyor, the main rotation axis is 8,000 to 10,000 RPM, and is transferred to a grinder with a rotating speed of 1,500 to 3,500 RPM. .

Cellulose ethers were prepared by varying the amount of slurry applied in the washing and filtration processes, and the time taken for filtration and the content of residual salts are shown in Table 1 below. Shown in

Comparative Example 1

Cellulose ether was prepared in the same manner as in Example, but a conventional batch filter was used in the filtration process.

The time taken for filtration and the content of residual salts are shown in Table 1 below.

As shown in Table 1, when Example 1 and Comparative Example 1 were compared, the time required for washing and filtering the same amount of slurry at 60 kg was 30 minutes for Example 1 of the present invention and 120 minutes for the Comparative Example. It became.

In addition, even when washed and filtered by varying the slurry content, the removed salt content is 0.08 to 0.13% by weight of the dry product, so that the salt can be removed at an efficiency of 2 to 4 times higher than that of 3% of the conventional comparative example. It can be seen.

As shown in Table 2 above, according to the method of the present invention, the throughput of the washed slurry per unit time was 400 to 600 kg / hr, and the wastewater generated was 1: 5 to 10 weight ratio compared to the synthetic product. According to the filtration method, the throughput of the washed slurry per unit time was 150 to 250 kg / hr, and the amount of wastewater generated was 1: 15-25 by weight compared to the synthetic product.

That is, it can be seen that the amount of wastewater generated can be reduced 2.5 to 5 times.

As described above, according to the method of the present invention, in the preparation of cellulose ether, the time required for filtration can be reduced by about four times by repeating washing and filtration continuously by improving the conventional batch filtration method. Simultaneous drying and drying can shorten the process, improve the salt removal efficiency by 2 to 4 times, and use less filtered water, which can reduce the amount of wastewater and can produce cellulose ether in a preferred way in terms of environmental conservation. .

Claims (5)

In the method of producing cellulose ether which softens cellulose and then etherified cellulose ether slurry is washed with hot water to remove salts and then pulverized and dried, The cellulose ether slurry is introduced into a rotating cylindrical filter equipped with a plurality of filter cells attached to the filter net individually, and the cellulose ether slurry is repeatedly washed while the filter cell passes through the hot water and the steam sprayer by the rotation of the cylindrical filter. And filtered, The washed and filtered wet cellulose ether is the main axis of rotation of 8,000 ~ 10,000 RPM, transfer to a grinder rotating horizontally at the condition of the rotation speed of the classifier 1,500 ~ 3,500 RPM with the hot air to be pulverized and dried at the same time, The method of producing a cellulose ether, characterized in that the process of introducing the cellulose ether slurry into the filter and the wet cellulose ether is transferred to the mill. The method for producing cellulose ether according to claim 1, wherein the alkoxy substitution degree of the prepared cellulose ether is 15 to 30%. The method for producing cellulose ethers according to claim 1, wherein the hydroxyl alkoxy substitution degree of the prepared cellulose ether is 5 to 25%. The method of claim 1, wherein the filtration process is characterized in that the cellulose ether slurry is repeatedly washed two or more times alternately by hot water and steam and at the same time the waste water is filtered. delete