JPS5941644B2 - Method for etherifying carboxymethyl cellulose - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing carboxymethylethyl cellulose (hereinafter abbreviated as CMEC), and particularly to a method for reducing the amount of etherification agent used.

Treatment of celluloses (i.e., cellulose or cellulose ethers having unsubstituted hydroxyl groups in which a portion of the hydroxyl groups in the glucose units are substituted by one or more ether groups) with caustic alkali. A method for obtaining cellulose ethers by reacting alkali cellulose with an etherifying agent such as an alkyl halide is known.

By the way, etherification agents such as alkyl halides not only react with cellulose, but also cause side reactions (
(hydrolysis reaction). Therefore, lowering the side reaction rate of the etherification agent and increasing the effective utilization rate of the etherification agent has important significance in producing cellulose ethers at low cost, and conventionally, it has been used as a means to increase the effective utilization rate of the etherification agent. Various types have been proposed, but the main points are:
In both cases, a highly concentrated caustic alkaline aqueous solution is used when preparing the alkali cellulose used for etherification, in other words, the conditions are such that the amount of water in the reaction system, which is a factor in the hydrolysis reaction of the etherification agent, is reduced as much as possible. is common. Although such a method has logical validity, on the other hand, because a highly concentrated caustic alkali aqueous solution is used, the uniform dispersibility of the alkali into cellulose is reduced, so the reaction of the alkali cellulose is This method has disadvantages in that side reactions of the etherifying agent tend to increase due to decreased activity, and cellulose esters with non-uniform distribution of ether groups tend to be produced. The present inventors have previously proposed a method for physically and chemically activating cellulosic raw materials as a method for producing high-grade cellulose ether, based on the prior art as described above.

That is, the method for producing uniformly mercerized alkali cellulose in the form of a soft powder in which the etherifying agent is physically uniformly dispersed and easily permeated, as disclosed in Japanese Patent Application No. 54-16100, and the chemical method as disclosed in Japanese Patent Application No. 106,312-1980. These methods use quaternary salts as phase transfer catalysts to specifically activate the etherification reaction of cellulose, and these methods advantageously produce high-grade cellulose ethers. The present invention further develops the method for producing cellulose ethers previously proposed by the present inventors as described above, and produces industrially advantageous high-grade cellulose ethers with good solubility and film-forming properties suitable for coating agents, etc. The present invention provides a method for manufacturing. That is, the gist of the present invention is to prepare carboxymethyl cellulose (hereinafter abbreviated as CMC) in the presence of a relatively low concentration caustic aqueous solution with an organic solvent that does not substantially dissolve water but dissolves the etherification agent and is stable for the reaction. This is a method for producing high-grade CMEC, which is characterized in that the required amount of ethyl halide to be used is reduced by combining the following reaction conditions when reacting with ethyl halide in the coexistence of an organic solvent.

(1) Caustic aqueous solution concentration during CMC mercerization 40% or more and less than 50% by weight (2) Caustic alkali aqueous solution liquid ratio during CMC mercerization 2 to 4 times that of CMC (weight ratio) (3) Etherification reaction Reaction temperature and reaction time 1st stage: 130°C to 15°C (0.5 to 6 hours) 2nd stage
50°C to 120°C (1 to 6 hours) To explain the method of the present invention in more detail, first, CMC is mercerized with caustic alkali.
As mentioned above, by using it as an aqueous solution of less than 50% by weight, the uniform dispersibility of alkali in CMC can be improved, and by setting the liquid ratio in the range of 2 to 4 times (to CMC weight ratio), it can be used during the etherification reaction. This suppresses undesirable solidification of the reactants and provides uniform dispersion of the ethyl halide in the mercerized CMC.

The above is the first main point of the present invention. Although there are no particular restrictions on CMC used in the present invention, from the gist of the present invention, it is desirable that it be dissolved in an aqueous caustic alkali solution of the above concentration, and from this point of view, the degree of substitution of the carboxymethyl group is 0.05 or more, preferably 0.05. Two or more are suitable. Furthermore, the mercerization method can be carried out more advantageously by employing the method previously proposed (Japanese Patent Application No. 16100/1982). Next, by adjusting the reaction temperature and reaction time during the etherification reaction to the above-mentioned two-step combination, it is possible to suppress as much as possible an undesirable side reaction during the etherification reaction, that is, the hydrolysis reaction of ethyl halide. That is, by first adjusting the etherification reaction temperature to the first stage reaction temperature range (130 to 15 C), it becomes possible to carry out the reaction as a homogeneous slurry, which is impossible to achieve under conventionally known reaction conditions. , mercerized CMC
Since the activity of ethyl halide is increased and the effective utilization rate of ethyl halide, which is an etherification agent, is increased, it is possible to reduce the amount of etherification agent added at the start of the etherification reaction. As mentioned above, by setting the reaction temperature to a high temperature of 130 to 150°C, the etherification reaction activity can be increased and the required amount of etherification agent added can be reduced. Unfavorable side reactions such as decomposition of the main chain or side chains are likely to occur;
This often causes a decrease in the yield of the desired CMEC.

Therefore, the high temperature reaction time of the first stage is the minimum reaction time required for CMC to be uniformly slurried in the organic solvent used for the reaction and for the etherification reaction to be sufficiently activated, that is, 0.5 to 6 It is important to take the time.

After that, the etherification reaction is completed under conditions that suppress inconvenient side reactions such as cleavage of the cellulose main chain or side chain, i.e., the etherification reaction is maintained in the second stage reaction temperature range (50 to 120°C) for 1 to 6 hours. to prevent a decrease in the yield of the target CMEC.

The above is the second main point of the present invention. Note that if the reaction time is sufficient to obtain the desired degree of etherification in the first step, it is possible to omit the second step, and as long as the reaction time in the first step does not exceed the above range, basically the main This is not contrary to the spirit of the invention.

It is also possible to add a catalytic amount of a quaternary salt as a phase transfer catalyst during the etherification reaction as in the invention of Japanese Patent Application No. 106312/1982, which does not contradict the gist of the present invention. As mentioned above, the reaction solvent is an organic solvent that does not substantially dissolve water, but that dissolves the etherification agent and is stable for the reaction, such as aliphatic hydrocarbons, aromatic hydrocarbons, or Ditarolmethane,
It is preferable to add a halogenated hydrocarbon stable under the reaction conditions, such as tritalolethane, in an amount of 2 to 6 times (weight ratio) to CMC. One of the advantages achieved by the method of the present invention is that the consumption of etherifying agent can be reduced to a greater extent than in the prior art. Conventionally, in the etherification of cellulose, for example, when ethyl chloride was used as an etherification agent, the conventional method had a low effective utilization rate of the etherification agent. /obtained purified CMEC weight) was difficult to reduce to 2 or less, but as is clear from the examples described later, by implementing the present invention, it is possible to easily reduce the basic unit to 2 or less. It became possible. Furthermore, in the present invention, uniform etherification is performed even though the ratio of the etherification agent used is reduced, and the resulting CMEC provides a coating with excellent transparency, smoothness, and strength, and is suitable for applications such as coating of tablets. It is suitable for

By carrying out the present invention based on the above, CMC
When etherifying with ethyl halide, the effective utilization rate of ethyl halide, which is an etherification agent, is increased,
Not only can the necessary amount of addition be reduced, but also it is possible to suppress inconvenient side reactions such as decomposition of cellulose chains during the etherification reaction, and the desired CMEC can be produced at low cost.

Next, the method of the present invention will be explained with examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Note that parts in the examples mean parts by weight, and the test methods used in the examples are as follows.

1) Solubility The behavior when each sample 19 was dissolved in the solvent 199 at room temperature was observed with the naked eye.

2) Film-forming property The solution of 1) was applied onto a glass plate and dried at 70° C. for 30 minutes to form a film with a thickness of about 50 μm, and the state was observed.

Example 1 Substitution degree of carboxymethyl group (hereinafter abbreviated as DS) 0.5
0, CMC 84.79 with water content 5.6% and 49% sodium hydroxide aqueous solution 2049 (2.
55 times the weight) into a grinding type seconder and heat at 30 to 40℃.
The mixture was stirred for 45 minutes to mercerize the CMC.

This mercerized CMCl toluene 3209, tetramethylammonium chloride 3.49, and ethyl chloride 1
59 g (2.5 times the molar amount per hydroxyl group possessed by CMC) was charged into an autoclave and heated to 140 g with vigorous stirring.
The reaction was carried out at 110°C for 2 hours, followed by 1 hour at 110°C.

After cooling, most of the solvent was distilled and recovered, pure water 2409 was added, and the mixture was stirred at room temperature for 2 hours.

Next, the pH of the system was adjusted to about 2 with 12N sulfuric acid to obtain granular carboxymethylethylcellulose. This was thoroughly washed with warm water at 50 to 60°C, and then dried in a hot air dryer at 70°C until it reached a constant weight to obtain purified product 849. The DS of the carboxymethyl group of this product is 0.50, the DS of the ethoxyl group is 2.05, and the DS of the carboxymethyl group is 2.05.
0:20 weight ratio), toluene-ethanol (80:20
) and methylene chloride-ethanol (50:50), forming a homogeneous solution with no insoluble matter observed.

The dried films obtained from these solutions were clear, colorless, smooth and strong. Note that the basic unit of ethyl chloride in this example was 1.89.

Example 2 No addition of tetramethylammonium chloride 1
Example 1 except that the reaction time at 40°C was 4 hours.
Purified carboxymethylethylcellulose 83.29 was obtained in exactly the same manner as above.

The DS of the carboxymethyl group of this product was 0.50, the DS of the ethoxyl group was 2.00, and the solubility and film-forming properties were as good as in Example 1. The basic unit of ethyl chloride in this example was 1.91.

Example 3 DSO of carboxymethyl group. 42, CMC85.39 with water content 6.2%, 30 (Ff) hydrogen peroxide solution 29 and 48% sodium hydroxide aqueous solution 2169 (liquid ratio 2.7)
was charged into a grinding type kneader and stirred at 30 to 48°C for 45 minutes to mercerize CMC.

This mercerized CMC, 320 g of toluene, and 132.3 g of ethyl chloride (twice the molar amount per hydroxyl group possessed by CMC) were charged into an autoclave and kept at 130°C for 6 hours with vigorous stirring, and then at 105-110°C.
The mixture was allowed to react for 2 hours. After cooling, the mixture was treated in the same manner as in Example 1 to obtain 84.8 g of purified carboxymethylethyl cellulose.

The DS of the carboxymethyl group in this product was 0.42, and the DS of the ethoxyl group was 2.10, and the solubility and film-forming properties were as good as in Example 1. The basic unit of ethyl chloride in this example was 1.65.

Comparative Example 1 The 49% aqueous sodium hydroxide solution during mercerization of CMC was set to 3609 (liquid ratio 4.5), and the ethylation reaction conditions were set to 1.
The treatment was carried out in the same manner as in Example 2 except that the temperature was 40°C for 8 hours, but when the obtained carboxymethylethylcellulose was washed with hot water of 50 to 60°C, there was a significant amount of hot water soluble matter, and it was difficult to filtrate it. The cleaning operation was extremely difficult.

Further, the purified product obtained was only 609. The DS of the carboxymethyl group of this product is 0.48, the DS of the ethoxyl group is 1.80, and the DS of the carboxymethyl group is 1.80.
), toluene-ethanol (80:20), and methylene chloride-ethanol (50:50) contained a significant amount of insoluble matter.The dried films obtained from these solutions were completely continuous films. It was an intermittent film with scales or cracks. The basic unit of ethyl chloride in this example was 2.65, which was significantly higher than in Examples 1 to 3. Comparative Example 2 The process was carried out in the same manner as in Example 2 except that the reaction temperature was 110°C and the reaction was carried out for 16 hours, but Comparative Example 1
Similarly, the hot water washing operation was extremely difficult and only purified carboxymethylethylcellulose 629 was obtained.

The basic unit of re-chill chloride in this example was 2.56, which was significantly higher than in Examples 1-3.

Claims (1)

[Claims] 1. When reacting carboxymethyl cellulose with ethyl halide in the presence of caustic soda to produce carboxymethyl ethyl cellulose, a caustic soda aqueous solution having a concentration of 40% by weight or more and less than 50% by weight is added in advance in an amount of 2 to 4 times the amount of carboxymethyl cellulose (weight ratio). After mercerization using a mercerizer, the first step is mercerization at 130-150°C with 0.
for 5-6 hours, then as a second step at 50-120°C for 1
A method for etherifying carboxymethylcellulose, which comprises reacting for ~6 hours.