JPH06199902A - Production of hydroxyethyl cellulose - Google Patents

Abstract

PURPOSE:To efficiently obtain the subject compound having high quality equivalent to the compound obtained by a conventional method, using a reactional solvent capable of readily reutilizing by using a sparingly water-soluble organic solvent as a reactional solvent in reacting an alkali cellulose with ethylene oxide. CONSTITUTION:Alkali cellulose obtained by reacting cellulose with an alkali is made to react with ethylene oxide, preferably at 40-60 deg.C using a sparingly water-soluble organic solvent (preferably methyl isobutyl ketone) to provide the objective compound. After the above-reaction is finished, the reaction liquid is usually neutralized with sulfuric acid, etc., to adjust pH to 5-7 and then, a mixed solvent obtained by adding methanol and water to the sparingly water- soluble organic solvent is preferably added to the reaction liquid to clean the resultant hydroxyethyl cellulose. Furthermore, as the alkali for preparing the alkali cellulose, sodium hydroxide is usually preferably used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing hydroxyethyl cellulose. Hydroxyethyl cellulose is a semi-synthetic polymer that is industrially produced from natural cellulose and is used for various purposes such as a thickener, a stabilizer for emulsion polymerization, a dispersant, a water retention agent and a protective colloid.

[0002]

2. Description of the Related Art Conventionally, a readily water-soluble organic solvent has been used as a reaction solvent in the production of hydroxyethyl cellulose. For example, secondary or tertiary aliphatic alcohols such as isopropyl alcohol, isobutyl alcohol, tert-butyl alcohol and isoamyl alcohol, ethers such as dioxane and 1,2-dimethoxyethane, or ketones such as acetone and methyl ethyl ketone. Is used as a solvent, and a method is known in which alkali cellulose obtained by treating cellulose with an alkali and ethylene oxide are mixed in the solvent to cause a reaction (JP-B-37-99, JP-A-1-165).
601 and JP-A-1-123801).

The above secondary or tertiary aliphatic alcohols, ethers and ketones are solvents which are easily soluble in water and also soluble in alkali. for that reason,
During the reaction, it facilitates contact between the alkali cellulose and ethylene oxide dissolved in the solvent, as a result, suitable for producing hydroxyethyl cellulose in which ethylene oxide is added throughout the anhydroglucose units constituting the cellulose chain. There is.

In order to isolate hydroxyethyl cellulose after reacting the alkali cellulose with ethylene oxide, after the reaction is completed, the alkali in the reaction solution is neutralized with an acid, and the product hydroxyethyl cellulose is obtained. However, since a large amount of alkali or a salt formed by the neutralization reaction exists in this hydroxyethyl cellulose, a purification step for removing these is necessary. In this purification step, a specific amount of water was added to the readily water-soluble organic solvent used as the reaction solvent in order to separate the alkali or a salt produced by neutralizing the alkali from hydroxyethyl cellulose which is easily dissolved in water. Wash with solution. At that time, it is important to select a specific water content, and it is generally considered preferable to add 5 to 20% by weight of water. However, a large amount of water is effective in removing alkalis or salts, but reduces the yield of hydroxyethyl cellulose. Further, if the amount of water is small, alkalis or salts are not sufficiently removed, and in order to obtain hydroxyethyl cellulose having a small amount of these, it is necessary to increase the number of times of washing, which is a long process and is not a good measure.

Further, as a cleaning liquid for removing alkalis or salts in the purification step, an easily water-soluble organic solvent solution containing the above-mentioned specific amount of water is used for the purpose of reducing swelling of the produced hydroxyethyl cellulose with water. There is a method using a mixed solvent to which methanol is added. Examples thereof include isopropyl alcohol / methanol / water, isobutyl alcohol / methanol / water, tert-butyl alcohol / methanol / water, isoamyl alcohol / methanol / water, or acetone / methanol / water, methyl ethyl ketone / methanol / water. To be

The reaction solvent and the mixed solvent used for washing in the purification step are recovered and reused in the next step. In the recovered solvent obtained here, the solvent is water. Due to its high solubility, inclusion of water or methanol is unavoidable. However, when such a recovery solvent is reused in the reaction between alkali cellulose and ethylene oxide, the contained methanol reacts with ethylene oxide to produce polyethylene glycol methyl ether, and the ethylene oxide is wastefully consumed. . In addition, polyethylene glycol methyl ether, which is a by-product, must be separated, which leads to an increase in the number of steps and is not economical. It is also known that the presence of water in the reaction solvent makes it difficult for the reaction between alkali cellulose and ethylene oxide to proceed. Therefore, the recovery solvent recovered by distillation or the like is difficult to use as a reaction solvent and can only be used as a cleaning solvent. Therefore, when an easily water-soluble organic solvent is used as a reaction solvent, it is always necessary to use a new solvent, which is not an industrially advantageous method.

[0007]

In view of the above situation, the present inventors have searched for a reaction solvent suitable for producing hydroxyethyl cellulose by reacting alkali cellulose with ethylene oxide. As a result, a certain poorly water-soluble organic solvent was used as a reaction solvent, and a solvent mixture for cleaning the salt formed by alkali or alkali neutralization was a mixed solvent prepared by adding methanol and water to the poorly water-soluble organic solvent. , It is possible to efficiently produce hydroxyethyl cellulose having the same quality as that obtained with a readily water-soluble organic solvent, and in this case, it is recovered by distillation from the reaction solvent and the mixed solvent used for washing. With regard to the solvent, the inventors have found that hydroxyethyl cellulose can be industrially advantageously produced because the early fraction can be reused for washing and the latter fraction can be reused as a reaction solvent after liquid separation, and thus the present invention was reached.

That is, the gist of the present invention is to use (1) a poorly water-soluble organic solvent as a reaction solvent in a method for producing hydroxyethyl cellulose in which alkali cellulose obtained by reacting cellulose with alkali is reacted with ethylene oxide. In the method for producing hydroxyethyl cellulose, and (2) the method for producing hydroxyethyl cellulose in which alkali cellulose obtained by reacting cellulose with alkali is reacted with ethylene oxide, a poorly water-soluble organic solvent is used as a reaction solvent. The present invention relates to a method for producing hydroxyethyl cellulose, characterized in that a mixed solvent of the poorly water-soluble organic solvent, methanol and water is used as a washing solution for hydroxyethyl cellulose.

The poorly water-soluble organic solvent used in the present invention has a solubility in water of about 0 to 3% and a carbon number of 6 to 1.
It is selected from among 0 aliphatic ketones. Aliphatic ketones having 5 or less carbon atoms have high solubility in water, making it difficult to separate them from water when recovering the solvent. Also, carbon number is 1
One or more aliphatic ketones have a poor affinity with methanol and water, and when used as a solvent for washing alkali or a salt formed by neutralization with alkali when mixed with methanol and water, a sufficient washing effect cannot be obtained.

Specific examples of the aliphatic ketone that can be used in the present invention include methyl isobutyl ketone and methyl-
Examples include n-amyl ketone, methyl-n-hexyl ketone, ethyl-n-butyl ketone, di-n-propyl ketone and diisobutyl ketone. Among them, methyl isobutyl ketone is preferably used because it has a relatively low boiling point and is easily recovered by distillation.

The present invention is a method for producing hydroxyethyl cellulose by reacting alkali cellulose obtained by reacting alkali with cellulose and ethylene oxide. The alkali cellulose used here is pulp finely ground as cellulose. It can be prepared by mixing and an aqueous alkaline solution. The alkali species is not particularly limited, and examples thereof include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, and sodium hydroxide is usually used.
The amount of sodium hydroxide used is such that the weight ratio of sodium hydroxide to cellulose is 0.2 to 0.
8, preferably in the range of 0.25 to 0.5. Both are dipped or mixed by a conventional method to obtain alkali cellulose.

The above-mentioned slightly water-soluble organic solvent such as methyl isobutyl ketone in which ethylene oxide is dissolved is added to the alkali cellulose obtained above and reacted. The amount of ethylene oxide used is determined by the number of moles of ethylene oxide to be added, but it is usually used in a weight ratio of 0.6 to 1.4 with respect to the cellulose used.

The amount of the slightly water-soluble organic solvent such as methyl isobutyl ketone used is in the range of 0.6 to 20 times by weight, preferably 0.6 to 15 times by weight of the weight of cellulose. If the amount of the poorly water-soluble organic solvent used is less than 0.6 times by weight, the addition of ethylene oxide to the cellulose chain is not evenly added to the anhydroglucose unit, resulting in non-uniformity. Is decreased, which is not preferable. The reaction temperature is usually in the range of 40 to 80 ° C, preferably 40 to 60 ° C.

After completion of the reaction, the alkali in the reaction solution is neutralized to adjust the pH of the reaction solution to 5-7. Normal acids such as sulfuric acid, nitric acid and acetic acid are used for neutralization. Then, in order to separate the alkali or the salt formed by the neutralization reaction from the target hydroxyethyl cellulose, in the method of the present invention, methanol and water are added to the poorly water-soluble organic solvent used in the reaction, such as methyl isobutyl ketone. The mixed solvent described above is added to the reaction solution after the reaction, the hydroxyethyl cellulose is washed, and filtered.

The mixed solvent used as the washing solution is a poorly water-soluble organic solvent: 30 to 50% by weight, methanol: 20 to 6
Those having a composition of 0% by weight and water: 10 to 30% by weight are preferably used. By adding the mixed solvent having the above composition to the reaction solution, washing and filtering the hydroxyethyl cellulose, hydroxyethyl cellulose having a low content of alkali or salt can be obtained.

Generally, the quality of hydroxyethyl cellulose is evaluated by the viscosity and the transparency of the aqueous solution thereof, but the viscosity and the transparency of the aqueous solution of hydroxyethyl cellulose obtained by the method of the present invention are different from those obtained by the conventional method. Not expensive.

The reaction solvent after separating the hydroxyethyl cellulose and the mixed solvent used for washing are separated and recovered by distillation. For example, when methyl isobutyl ketone is used as the poorly water-soluble organic solvent, a fraction containing methyl isobutyl ketone, methanol and water is obtained as the low boiling point fraction at 65 to 88 ° C, and a high boiling point fraction at 88 to 100 ° C is obtained. As the fraction, a fraction containing methyl isobutyl ketone and water is obtained. In particular, methyl isobutyl ketone and water have a boiling point of 88 ° C. and a weight ratio of methyl isobutyl ketone / water = 3/1.
A distillate is obtained with an azeotropic composition of and separated into two layers. If only the upper layer separated from these two layers is used as the reaction solvent for the next time,
Since the amount of water in the contained methyl isobutyl ketone is as small as about 2%, it can be reused without adversely affecting the reaction with ethylene oxide and good results can be obtained.

[0018]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Example 1 50 g of finely pulverized pulp and 100 g of 20% sodium hydroxide were mixed at 30 ° C. for 30 minutes to obtain 150 g of alkali cellulose. A 1-liter kneader was charged with 150 g of the above alkali cellulose, 50 g of ethylene oxide and 50 g of methyl isobutyl ketone, and heated at 50 ° C. for 3 hours. The pH of the reaction mixture was then adjusted to 6 by adding 30 g of acetic acid to the reaction mixture. A mixed solvent of 200 g of methyl isobutyl ketone, 200 g of methanol and 100 g of water was added to the obtained neutralized mixture to prepare a slurry liquid, and hydroxyethyl cellulose was separated by filtration from the slurry liquid. Filtration liquid 1 containing 250 g of wet hydroxyethyl cellulose, neutralized salt and the like by repeating washing with a mixed solvent having the above composition and filtration three times in total.
Obtained 530 g. The yield of dried hydroxyethyl cellulose was 82 g.

2% of the hydroxyethyl cellulose obtained
The viscosity of the aqueous solution at 20 ° C. is 1000 cps (BM type viscometer), and the transparency (JIS K0102) is 50 c.
It was m or more. The filtrate contained 585 g of methyl isobutyl ketone, 540 g of methanol, and 344 g of water. From this filtrate, by distillation, 65-88 ° C
1332 g of low-boiling fraction and 67 g of high-boiling fraction of 88 to 100 ° C were obtained. Each composition has a low boiling fraction of 535 g of methyl isobutyl ketone, 540 g of methanol and 257 g of water.
Then, the high boiling fraction was 50 g of methyl isobutyl ketone and 17 g of water. The high boiling fraction was separated into layers, and 50 g of upper layer methyl isobutyl ketone was recovered. The content of water in methyl isobutyl ketone was 1 g.

Example 2 The reaction was carried out under the same conditions as in Example 1 except that 50 g of methyl isobutyl ketone (water content: 2% by weight) recovered by distillation in Example 1 was used as a reaction solvent. As a washing liquid after the reaction, a low boiling point fraction composed of methyl isobutyl ketone / methanol / water recovered in Example 1 was used in combination, and a mixed solvent having the same composition as in Example 1 was used for washing and filtration. As a result, 80 g of hydroxyethyl cellulose was obtained. The viscosity and the transparency at 20 ° C. of the obtained 2% aqueous solution of hydroxyethyl cellulose were similar to those of the hydroxyethyl cellulose obtained in Example 1.

Example 3 50 g of pulp was dipped in 20% sodium hydroxide, squeezed and crushed to obtain 150 g of alkali cellulose. 150 g of the alkali cellulose obtained above and 50 g of ethylene oxide were dissolved in 750 g of methyl isobutyl ketone, and the reaction and purification were carried out under the same conditions as in Example 1 to obtain 80 g of hydroxyethyl cellulose. The viscosity and the transparency of the obtained 2% aqueous solution of hydroxyethyl cellulose at 20 ° C. were similar to those of the hydroxyethyl cellulose obtained in Example 1.

Example 4 The same reaction and purification as in Example 1 were carried out except that diisobutyl ketone was used instead of methyl isobutyl ketone in Example 1, to obtain 83 g of hydroxyethyl cellulose. The viscosity and the transparency at 20 ° C. of the obtained 2% aqueous solution of hydroxyethyl cellulose were similar to those of the hydroxyethyl cellulose obtained in Example 1.

Comparative Example 1 82 g of hydroxyethyl cellulose was obtained by carrying out the reaction, washing and filtration by replacing methyl isobutyl ketone with acetone in Example 1. The viscosity and the transparency at 20 ° C. of the obtained 2% aqueous solution of hydroxyethyl cellulose were similar to those of the hydroxyethyl cellulose obtained in Example 1. The filtrate contained 585 g of acetone, 540 g of methanol, and 344 g of water. An attempt was made to obtain an acetone fraction containing no methanol from this filtrate by distillation, but it could not be obtained.

Comparative Example 2 The reaction was carried out by replacing methyl isobutyl ketone of Example 1 with isopropyl alcohol. The reaction mixture is then brought to pH 6 by adding 30 g of acetic acid and to the resulting neutralized mixture 350 g of isopropyl alcohol and 1 part of water.
A mixed solvent having a composition of 50 g was added to prepare a slurry liquid. Hydroxyethyl cellulose was filtered off from this slurry liquid. Washing with a mixed solvent and filtration were repeated 3 times in total, and dried to obtain 82 g of hydroxyethyl cellulose.

2% of the hydroxyethyl cellulose obtained
The viscosity and the transparency at 20 ° C. of the aqueous solution were similar to those of the hydroxyethyl cellulose obtained in Example 1. Isopropyl alcohol 975 is used as the filtrate.
g, 494 g water. The composition of each of the fractions obtained by distillation from this filtrate was 97% isopropyl alcohol.
It was 5 g and 135 g of water (IPA / water azeotropic composition).
Since the fraction was a homogeneous solution, isopropyl alcohol alone could not be separated.

[0026]

INDUSTRIAL APPLICABILITY The present invention uses a poorly water-soluble organic solvent in place of the easily water-soluble organic solvent conventionally used as a reaction solvent in the method for producing hydroxyethyl cellulose by the reaction of alkali cellulose and ethylene oxide. Characterize. The poorly water-soluble organic solvent used in the present invention is easily separated from the reaction solution by distillation because it has good separability from water, and is reused as a reaction solvent in the next reaction of alkali cellulose and ethylene oxide. be able to. Therefore, hydroxyethyl cellulose can be industrially advantageously produced.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadaki Yano 1 No. 1 Irifune-cho, Shikima-ku, Himeji-shi, Hyogo Sumitomo Seika Chemical Co., Ltd. 2nd Research Center

Claims (5)

[Claims] 1. A method for producing hydroxyethyl cellulose, which comprises using a poorly water-soluble organic solvent as a reaction solvent in the method for producing hydroxyethyl cellulose in which alkali cellulose obtained by reacting cellulose with alkali is reacted with ethylene oxide. 2. A method for producing hydroxyethyl cellulose in which alkali cellulose obtained by reacting cellulose with alkali is reacted with ethylene oxide, wherein a poorly water-soluble organic solvent is used as a reaction solvent, and the resulting hydroxyethyl cellulose is washed as a washing solution. A method for producing hydroxyethyl cellulose, which comprises using a mixed solvent comprising a water-soluble organic solvent, methanol and water. 3. A mixed solvent used as a washing solution is a poorly water-soluble organic solvent: 30 to 50% by weight, methanol: 20 to
The production method according to claim 2, which has a composition of 60% by weight and water: 10 to 30% by weight. 4. The method according to claim 1, 2 or 3, wherein the poorly water-soluble organic solvent is an aliphatic ketone having 6 to 10 carbon atoms. 5. The method according to claim 4, wherein the aliphatic ketone is methyl isobutyl ketone.