KR20150080341A - Method of preparing cellulose ether and cellulose ether prepared thereby - Google Patents

Abstract

Disclosed is a method for preparing a cellulose ether. The disclosed method for preparing a cellulose ether comprises the steps of: (a) inputting a cellulose and a reaction medium in a reactor; (b) additionally inputting an alkalizing agent in the reactor and converting the cellulose to an alkaline cellulose; (c) additionally inputting an etherifying agent in the reactor and converting the alkaline cellulose to a cellulose ether; (d) additionally inputting acid in the reactor and lowering a pH level of the content obtained in the step (c); (e) filtering the content of the reactor and separating the cellulose ether obtained in the step (d); (f) contacting the cellulose ether separated in the step (e) with an oxidizing agent; and (g) decomposing the cellulose ether contacted with the oxidizing agent by increasing the temperature thereof, thereby providing a low-viscosity cellulose ether.

Description

[0001] The present invention relates to a method for producing cellulose ether and a cellulose ether prepared by the method,

A process for the preparation of cellulose ethers and cellulose ethers prepared by the process are disclosed. More particularly, the present invention relates to a process for producing cellulose ether, comprising the step of bringing a cellulose ether subjected to a filtration step into contact with an oxidizing agent, and a cellulose ether produced by the process.

Cellulose ether refers to a cellulose derivative obtained by etherifying a hydroxy group of cellulose, and is industrially very useful compound used in a wide range of fields such as pharmaceuticals, foods, cosmetics and building materials. Such cellulose ethers include alkylcelluloses, hydroxyalkylcelluloses, and hydroxyalkylalkylcelluloses.

Among them, low viscosity cellulose ethers are used for medicines and foods. Low-viscosity cellulose ethers can be prepared by alkalizing, etherizing and neutralizing low-molecular cellulose as a starting material, but low-viscosity cellulose ethers synthesized therefrom can be lost in a large amount in a subsequent step such as filtration . Another method is to alkalize and etherify the polymeric cellulose as a starting material and decompose the cellulose ether synthesized therefrom into low molecular weight cellulose ether by hydrogen peroxide and then neutralize and filter the cellulose ethers of low viscosity . However, since hydrogen peroxide is activated in an alkaline environment, it has to be introduced before the neutralization process, and thus there is a disadvantage that loss in the filtration process can not be prevented. In addition, when hydrogen peroxide is used to produce cellulose ether having an ultra-low viscosity as described above, a separate facility for introducing hydrogen peroxide is required.

One embodiment of the present invention provides a process for producing cellulose ether comprising contacting a filtered cellulose ether with an oxidizing agent.

Another embodiment of the present invention provides a cellulose ether produced by the method for producing the cellulose ether.

According to an aspect of the present invention,

(a) injecting the cellulose and the reaction medium into a reactor;

(b) further adding an alkalizing agent to the reactor to convert the cellulose into alkaline cellulose;

(c) further converting the alkalized cellulose into a cellulose ether by further adding an etherifying agent to the reactor;

(d) further adding an acid to the reactor to decrease the pH of the obtained reactor contents after completion of the step (c);

(e) filtering the contents of the reactor to separate the cellulose ether obtained in the step (d);

(f) contacting the cellulosic ether separated in step (e) with an oxidizing agent; And

(g) decomposing cellulose ether in contact with the oxidizing agent to raise the temperature of the cellulosic ether.

The step (f) may be performed by spraying an oxidizing agent solution containing the oxidizing agent to the cellulose ether.

The spray amount of the oxidant solution may be 3 to 10 parts by weight based on 100 parts by weight of the cellulose ether.

Wherein the oxidant solution is at least one acid selected from the group consisting of hydrohalogen acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid and hydrochloric acid; And at least one volatile substance of C1-C20 alcohols and C1-C20 ketones.

The oxidant solution may include hydrochloric acid and methanol.

The oxidizing agent solution may include 100 to 400 parts by weight of the volatile substance with respect to 100 parts by weight of the acid.

The step (g) may be performed at 50 to 90 ° C for 10 to 60 minutes.

According to another aspect of the present invention,

A cellulose ether having a viscosity of 10 to 700 cps in an aqueous solution having a concentration of 2% by weight is prepared by the method for producing the cellulose ether.

According to the method for producing cellulose ether according to one embodiment of the present invention, low viscosity cellulose ether can be obtained in high yield.

Hereinafter, a method for producing cellulose ether according to one embodiment of the present invention will be described in detail.

As used herein, the term " cellulose ether " means a compound in which the hydroxy group of the cellulose is partially or wholly etherified, such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, Hydroxybutyl methylcellulose, ethylhydroxyethylcellulose, carboxymethylcellulose, carboxymethylhydroxyethylcellulose, or a combination thereof.

A method of making a cellulose ether according to an embodiment of the present invention comprises the steps of:

First, the cellulose and the reaction medium are introduced into the reactor (step (a)).

The cellulose is finely pulverized raw pulp.

The reaction medium may comprise water, acetone, tertiary butyl alcohol, isopropyl alcohol or combinations thereof. For example, the amount of the reaction medium used may be 600 to 2000 parts by weight based on 100 parts by weight of the cellulose.

Next, an alkalizing agent is further added to the reactor to convert the cellulose into alkaline cellulose (step (b)). The step (b) is intended to facilitate the reaction of the etherification agent and the cellulose described below by weakening the crystal structure of the cellulose. That is, the alkalizing agent plays a role of promoting the reaction of the cellulose with the etherifying agent. The alkali-converted cellulose thus converted must be agitated at room temperature (20 to 30 ° C) for a certain period of time, so that its crystal structure can be uniformly weakened.

As the alkalizing agent, an alkali metal hydroxide may be used. For example, the alkalizing agent may include sodium hydroxide, potassium hydroxide, lithium hydroxide, or a combination thereof.

The amount of the alkalizing agent may be 5 to 600 parts by weight based on 100 parts by weight of the cellulose. If the amount of the alkalizing agent is within the above range, the etherifying agent is uniformly substituted in the entire cellulose, and the reactivity of the etherating agent is increased in the step (c) described later, so that the cellulose ether having the desired degree of substitution can be obtained.

Next, an etherifying agent is further added to the reactor to convert the alkalized cellulose into a cellulose ether (step (c)).

The etherifying agent may be an alkylene oxide compound comprising propylene oxide, ethylene oxide or a combination thereof; And an alkyl chloride compound including methyl chloride, ethyl chloride, propyl chloride, butyl chloride, or a combination thereof.

The amount of the etherifying agent may be 20-400 parts by weight based on 100 parts by weight of the cellulose. If the amount of the etherifying agent is within the above range, the risk of an abnormal reaction and formation of by-products are reduced in the process, and cellulose ether having a desired degree of substitution can be obtained.

In the step (c), the etherification agent may be added to the reactor at 10 to 30 ° C., and the temperature may be raised to 50 to 130 ° C., followed by 10 to 150 minutes. If the reaction temperature after the introduction of the etherification agent into the reactor in the step (c) is within the above range, the etherification agent may have a sufficient heat for reaction with the cellulose, and the increase in the production cost due to use of an excessive heat source, And the like can be reduced.

When the reaction time in the step (c) is within the above range, the reactivity of the etherification agent can be kept high and the productivity of the cellulose ether can be improved.

The step (c) may further include cooling the reactor contents obtained at the end of the step (c) to 50 to 70 ° C between the step (c) and the step (d) described below. This step is intended to prevent an adverse reaction and local neutralization reaction due to the neutralization heat generated during the acid addition in the step (d) described later.

Next, an acid is further added to the reactor to decrease the pH of the reactor contents obtained after the completion of the step (c) (step (d)).

The acid may include hydrohalogenic acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, hydrochloric acid or a combination thereof, which may be diluted with water to a concentration of 20 to 90% by weight.

The amount of the acid added may be equal to or greater than the amount of the alkalizing agent. If the amount of the acid added is within the above range, the reactor contents obtained after the completion of the step (c) are sufficiently acidified to increase the efficiency of the subsequent steps such as washing and drying, and the physical properties of the final product can be improved.

Next, the content of the reactor is filtered to separate the cellulose ether obtained in the step (d) (step (e)).

The contents of the reactor may be washed with water, acetone, isopropyl alcohol, or a combination thereof, and then filtered.

Next, the cellulose ether separated in the step (e) is contacted with an oxidizing agent (step (f)).

The step (f) may be performed by spraying an oxidizing agent solution containing the oxidizing agent to the cellulose ether.

The spray amount of the oxidizer solution may be 3 to 10 parts by weight based on 100 parts by weight of the cellulose ether.

When the spray amount of the oxidizing agent solution is within the above range, gelation of the cellulose ether can be prevented, and a cellulose ether having a low viscosity can be obtained.

Wherein the oxidant solution is at least one acid selected from the group consisting of hydrohalogen acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid and hydrochloric acid; And at least one volatile substance of C1-C20 alcohols and C1-C20 ketones.

The alcohols may include, for example, methanol, ethanol, propanol, butanol, benzyl alcohol or combinations thereof.

The ketones may include, for example, acetone, ethyl methyl ketone, methyl vinyl ketone, diethyl ketone, or combinations thereof.

By bringing the cellulose ether into contact with the oxidizing agent, decomposition of the cellulose ether can occur uniformly in the step (g) described later.

The acid may be diluted with water to a concentration of 20 to 90% by weight.

The acid is vaporized in step (g) to decompose the cellulose ether. In addition, the volatile substance plays a role of rapidly evaporating the reaction medium such as water in the step (g) to prevent the cellulose ether from being dissolved in the reaction medium and gelation.

The oxidant solution may include hydrochloric acid and methanol.

The oxidizing agent solution may include 100 to 400 parts by weight of the volatile substance with respect to 100 parts by weight of the acid.

When the content of the volatile substance is within the above range, the viscosity of the cellulose ether can be lowered while rapidly evaporating the reaction medium.

Next, the cellulose ether in contact with the oxidizing agent is heated to decompose (step (g)).

The step (g) is for rapidly decomposing the cellulose ether by vaporizing the oxidizing agent in contact with the cellulose ether.

For example, when a mixed solution of hydrochloric acid and methanol is used as the oxidizing agent solution containing the oxidizing agent, the hydrogen chloride gas formed by vaporizing the hydrochloric acid may decompose the cellulose ether, and the methanol may be dissolved in water The gelation phenomenon of the cellulose ether can be prevented.

The step (g) may be performed at 50 to 90 ° C for 10 to 60 minutes.

When the reaction temperature and the reaction time in the step (g) are within the above ranges, cellulose ether having a low viscosity can be obtained while preventing gelation of the cellulose ether.

The step (f) and the step (g) are carried out after the step of filtering the cellulose ether (that is, step (e)), so that the cellulose ether can be obtained in high yield. If the step (f) and the step (g) are performed before the filtering step of the cellulose ether (that is, the step (e)), the cellulose ether Is lost in the filtration step, resulting in a lower yield of cellulose ether.

The viscosity of the aqueous solution having a concentration of 2% by weight of the cellulose ether obtained in the step (g) may be 10 to 700 cps. If the viscosity of the aqueous solution having a concentration of 2% by weight of the cellulose ether is less than 10 cps, it is not preferable from the point of view that the amount of the cellulose is increased in the application of the cellulose ether as a raw material. If the viscosity exceeds 700 cps, It is not preferable in that the physical properties can not be obtained.

In addition, the cellulose ether prepared by the above-mentioned method may be dried, pulverized to a predetermined size using a pulverizer, and classified into a size of 10 to 1,000 탆 by using a classifier.

As described above, the cellulose ether subjected to the filtration process is brought into contact with the oxidizing agent, and the cellulose ether thus obtained is heated and decomposed to obtain cellulose ether having a low viscosity.

Example

Example  1 to 8: Preparation of cellulose ether

2,000 ml of a reaction medium in which 200 g of pulverized pulp (cellulose) (Rayonier, Ethenier-F) and tertiary butyl alcohol, isopropyl alcohol, and water were mixed in a weight ratio of 83: 6: 11, Was charged to a possible reactor and stirred at 30 rpm for 10 minutes. Subsequently, 120 g of an aqueous solution of sodium hydroxide having a concentration of 50% by weight was further added to the reactor, followed by stirring at 80 rpm for 60 minutes. Thereafter, 220 g of ethylene oxide was further added to the reactor, and then the temperature of the reactor was raised to 100 ° C at a rate of 2 ° C / min to carry out the reaction for 80 minutes. Then, the temperature of the reactor was cooled to 60 DEG C at a rate of 1.5 DEG C / min. Then, 65 g of a nitric acid aqueous solution having a concentration of 60 wt% was further added to the reactor and stirred at 80 rpm for 30 minutes. Then, the contents of the reactor were discharged, washed with acetone, and filtered using a glass funnel. As a result, a solid was obtained. The solid (315 g) was finely sliced on a flat bottom container, and a mixed solution of hydrochloric acid and methanol having a hydrochloric acid concentration of 35 wt% in the amount shown in Table 1 was sprayed using a fine atomizer. Thereafter, the sprayed solid matter in a zipper bag (20 cm x 20 cm) was put and sealed in an oven and reacted under the temperature and time conditions shown in Table 1. At this time, the sealed zipper bag was taken out every 5 minutes, shaken, and then put into the oven again. Thereafter, the contents were discharged from the zippered bag and dried, followed by pulverization using a pulverizer, and classified into a size of 500 mu m or less using a classifier. As a result, a cellulose ether was obtained. The amounts of hydrochloric acid and methanol used in the above examples and the reaction conditions in the oven were summarized in Table 1 below.

Comparative Example  1: Preparation of cellulose ether

2,000 ml of a reaction medium in which 200 g of pulverized pulp (cellulose) (Rayonier, Ethenier-F) and tertiary butyl alcohol, isopropyl alcohol, and water were mixed in a weight ratio of 83: 6: 11, Was charged to a possible reactor and stirred at 30 rpm for 10 minutes. Subsequently, 120 g of an aqueous solution of sodium hydroxide having a concentration of 50% by weight was further added to the reactor, followed by stirring at 80 rpm for 60 minutes. Thereafter, 220 g of ethylene oxide was further added to the reactor, and then the temperature of the reactor was raised to 100 ° C at a rate of 2 ° C / min to carry out the reaction for 80 minutes. Then, the temperature of the reactor was cooled to 60 DEG C at a rate of 1.5 DEG C / min. Then, 65 g of a nitric acid aqueous solution having a concentration of 60 wt% was further added to the reactor and stirred at 80 rpm for 30 minutes. Thereafter, the contents of the reactor were discharged, washed with acetone, and then pulverized using a pulverizer, and classified into a size of 500 탆 or less using a classifier. As a result, a cellulose ether was obtained.

Comparative Example  2 to 9: Preparation of cellulose ether

Except that the hydrochloric acid / methanol mixed solution in the amounts shown in the following Table 1 was used and the reaction was conducted under the reaction conditions in the oven shown in Table 1 below. To prepare a cellulose ether. The amount of hydrochloric acid and methanol used in each of the comparative examples and the reaction conditions in the oven were summarized in Table 1 below.

Comparative Example  10: Preparation of cellulose ether (decomposition by the addition of hydrogen peroxide)

2,000 ml of a reaction medium in which 200 g of pulverized pulp (cellulose) (Rayonier, Ethenier-F) and tertiary butyl alcohol, isopropyl alcohol, and water in a weight ratio of 83: 6: 11 were mixed, Lt; RTI ID = 0.0 > 30 rpm < / RTI > for 10 minutes. Subsequently, 120 g of an aqueous solution of sodium hydroxide having a concentration of 50% by weight was further added to the reactor, followed by stirring at 80 rpm for 60 minutes. Thereafter, 220 g of ethylene oxide was further added to the reactor, and then the temperature of the reactor was raised to 100 ° C at a rate of 2 ° C / min to carry out the reaction for 80 minutes. Thereafter, the temperature of the reactor was cooled to 60 ° C at a rate of 1.5 ° C / min, and then 20 ml of a hydrogen peroxide aqueous solution having a concentration of 10% by weight was introduced and the reaction was continued for 60 minutes. Then, 65 g of a nitric acid aqueous solution having a concentration of 60% by weight was further charged into the reactor and stirred at 80 rpm for 35 minutes. Thereafter, the contents of the reactor were discharged, washed with acetone, and then pulverized using a pulverizer, and classified into a size of 500 mu m or less using a classifier. As a result, a cellulose ether was obtained.

Hydrochloric acid / methanol mixture solution
(Parts by weight based on 100 parts by weight of cellulose ether) Temperature
(° C) time
(minute) Example 1 5 65 30 Example 2 3 65 30 Example 3 10 65 30 Example 4 5 50 30 Example 5 5 80 30 Example 6 5 90 30 Example 7 5 65 10 Example 8 5 65 60 Comparative Example 1 - - - Comparative Example 2 One 65 30 Comparative Example 3 2 65 30 Comparative Example 4 20 65 30 Comparative Example 5 15 65 30 Comparative Example 6 5 40 30 Comparative Example 7 5 100 30 Comparative Example 8 5 65 5 Comparative Example 9 5 65 90 Comparative Example 10 - - -

Evaluation example

<Viscosity Measurement>

The cellulose ether prepared in Examples 1 to 8 and Comparative Examples 1 to 10 was dissolved in water to prepare a cellulose ether solution having a concentration of 2% by weight. The viscosity of the cellulose ether solution was measured with a Brookfield viscometer at 20 ° C And 20 rpm, and the results are shown in Table 2 below. However, in the cellulose ether prepared in Comparative Example 7, gelation occurred and the viscosity could not be measured.

&Lt; Measurement of yield >

The yields of the cellulose ethers prepared in Examples 1 to 8 and Comparative Examples 1 to 10 were calculated according to the following formula 1, and the results are shown in Table 2 below.

[Equation 1]

Yield (%) = amount of cellulose ether obtained (g) / amount of cellulose introduced (g) * 100

Viscosity
(cps) yield
(%) Example 1 370 158 Example 2 655 158 Example 3 55 158 Example 4 605 154 Example 5 185 155 Example 6 71 155 Example 7 690 158 Example 8 35 157 Comparative Example 1 2,050 157 Comparative Example 2 1,150 156 Comparative Example 3 960 158 Comparative Example 4 5.5 157 Comparative Example 5 8.1 159 Comparative Example 6 940 154 Comparative Example 7 - 155 Comparative Example 8 1,120 153 Comparative Example 9 3.4 157 Comparative Example 10 355 132

Referring to Table 2 above, the cellulose ethers prepared in Examples 1 to 8 were found to have a lower viscosity than the cellulose ethers prepared in Comparative Examples 1, 2, 3, 6 and 8. On the other hand, in the case of Comparative Examples 4, 5 and 9, the viscosity of the cellulose ether is lower than that of Examples 1 to 8, but when the viscosity is less than 10 as in Comparative Examples 4, 5 and 9, the amount of the cellulose ether . In addition, the comparative example 10 exhibits a similar viscosity to that of the example 1, but has a disadvantage in that the yield is significantly lower than that of the examples 1 to 8.

From the above results, it can be confirmed that cellulose ether having a low viscosity and excellent yield can be obtained by the process for producing cellulose ether according to the present invention.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (8)

(a) injecting the cellulose and the reaction medium into a reactor;
(b) further adding an alkalizing agent to the reactor to convert the cellulose into alkaline cellulose;
(c) further converting the alkalized cellulose into a cellulose ether by further adding an etherifying agent to the reactor;
(d) further adding an acid to the reactor to decrease the pH of the obtained reactor contents after completion of the step (c);
(e) filtering the contents of the reactor to separate the cellulose ether obtained in the step (d);
(f) contacting the cellulosic ether separated in step (e) with an oxidizing agent; And
(g) decomposing the cellulose ether in contact with the oxidizing agent by heating to decompose the cellulosic ether. The method according to claim 1,
Wherein the step (f) is carried out by spraying an oxidizing agent solution containing the oxidizing agent to the cellulose ether. 3. The method of claim 2,
Wherein the spray amount of the oxidant solution is 3 to 10 parts by weight per 100 parts by weight of the cellulose ether. 3. The method of claim 2,
Wherein the oxidant solution is at least one acid selected from the group consisting of hydrohalogen acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid and hydrochloric acid; And at least one volatile substance selected from the group consisting of C1 to C20 alcohols and C1 to C20 ketones. 3. The method of claim 2,
Wherein the oxidant solution comprises hydrochloric acid and methanol. 5. The method of claim 4,
Wherein the oxidizing agent solution comprises 100 to 400 parts by weight of the volatile substance per 100 parts by weight of the acid. The method according to claim 1,
Wherein the step (g) is carried out at 50 to 90 DEG C for 10 to 60 minutes. A cellulose ether prepared by the process for producing a cellulose ether according to any one of claims 1 to 7, wherein the aqueous solution having a concentration of 2% by weight has a viscosity of 10 to 700 cps.