JP2002097207A - Method for producing vinylidene chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a vinylidene chloride safely and efficiently which suppress the formation of byproduct. SOLUTION: The vinylidene chloride is produced by reacting 1,1,2- trichlorethane and an alkali hydroxide with maintaining the concentration of chloride ion in an aqueous phase to 3.2-4.2 mol/L.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for safely and efficiently producing vinylidene chloride by suppressing the generation of by-products, and relates to a chemical production technology.

[0002]

BACKGROUND OF THE INVENTION Vinylidene chloride is a substance used as an organic solvent or as a raw material for methyl chloroform, vinylidene chloride resin and other chemical products.
Due to its excellent gas impermeability, heat resistance and chemical properties, it is a widely used resin in films and other shapes.

This vinylidene chloride is mainly composed of 1,1
It is produced by a dehydrochlorination reaction of 1,2-trichloroethane with an alkali, and calcium hydroxide (slaked lime) or sodium hydroxide (caustic soda) is used as the alkali.

On the other hand, a method using calcium hydroxide is as follows.
Although it is an efficient and safe method, the desorbed hydrogen chloride reacts with calcium hydroxide to form solid calcium chloride, which not only causes loss of chlorine, but also causes problems such as pipe clogging and environmental hygiene. This is a method that has inherent problems.

[0005] On the other hand, the method using sodium hydroxide is a homogeneous reaction and the apparatus design and the like are easy. However, monochloroacetylene (hereinafter referred to as “MCA”) is used as a by-product.
That. ). Since MCA is a pyrophoric compound, it can be said that this method has a problem in terms of disaster prevention and safety.

In this method using sodium hydroxide, a method for suppressing the generation of MCA has already been proposed.
Japanese Patent Publication No. 04826 proposes a method in which sodium chloride (salt) is added to a reaction solution at a saturation solubility or in the vicinity thereof.

In Japanese Patent Application Laid-Open No. 10-316599, the ratio of the aqueous phase to the liquid phase in the reaction solution and the ratio of trichloroethane to hydroxide ions introduced into the reaction vessel are improved to solve the problems of the MCA. A method has been proposed in which the concentration of hydroxide ions in a reaction solution and the reaction temperature are set to a specific relationship.

In this publication, the amount of spontaneously combustible MCA is determined to be 8 to 1 in the recovered vinylidene chloride.
5 ppm (Examples 1 to 5) was observed, but for this purpose, the volume ratio of the oil phase and the aqueous phase in the liquid in the reaction tank had to be 1/20 (0.05) or more. However, the ratio of the aqueous phase in which vinylidene chloride was generated was low, so that the reaction efficiency was not good.

[0009]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 10-31 is disclosed.
As described in Japanese Patent No. 6599, the reaction between trichloroethane and alkali is carried out in the aqueous phase in the reaction solution. Therefore, in order to increase the productivity, it is desirable to increase the volume ratio of the aqueous phase in the reaction solution. .

Therefore, the present inventors have found that the oil phase which plays a role in extracting the generated vinylidene chloride and the like becomes smaller,
In view of the contradictory reaction characteristics of a rapid increase in CA, a method for maximizing the generation of MCA and increasing the reaction productivity of vinylidene chloride was studied.

As a result, the present inventors, when limiting the concentration of chloride ions in the aqueous phase in the reaction solution to a specific range,
The volume ratio of the oil phase and the aqueous phase in the liquid in the reaction tank was 1/25 (0.
04) or less, and it has been found that even if the reaction efficiency is increased and the productivity is improved, the generation of MCA is not more than an allowable amount, and the present invention has been completed.

[0012]

The process for producing vinylidene chloride according to the present invention comprises the steps of: 1,1,2-trichloroethane and alkali hydroxide;
It is characterized in that the reaction is performed while maintaining the range of 2 to 4.2 mol / L.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION 1,1,2-Trichloroethane The 1,1,2-trichloroethane used in the present invention may be manufactured industrially and may contain some impurities such as dichloroethane and tetrachloroethane. May be used, and once used as a raw material,
Those containing vinylidene chloride recovered after the reaction can be reused.

Alkali hydroxide Examples of the alkali hydroxide used in the present invention include sodium hydroxide and potassium hydroxide, and are used as an aqueous solution containing chloride ions by adding sodium chloride.

In the present invention, the concentration of chloride ions in the aqueous phase of the reaction solution must be maintained in the range of 3.2 to 4.2 mol / L, and the pH of the aqueous phase is 10 to 12. Is desirable, the alkali hydroxide concentration is 5 to 15% by mass,
An aqueous alkali hydroxide solution having a sodium chloride concentration of 5 to 15% by mass is used.

If the pH of the aqueous phase is high, the dehydrochlorination of vinylidene chloride is promoted, and the amount of MCA generated increases. If the pH is low, the reaction efficiency decreases, so it is desirable to avoid it.

As the sodium chloride to be added to the aqueous alkali hydroxide solution, it is possible to use a by-product produced by the production method of the present invention, which is a preferable method for resource saving.

The concentration of chlorine ions in the aqueous phase of the reaction solution is 3.2
If it is less than mol / L, MCA by-product cannot be suppressed and M
CA is generated in excess of the allowable amount, and its concentration is 4.2 mol / L.
If it exceeds, the reaction of the alkali hydroxide itself may be suppressed, and the yield of vinylidene chloride may be reduced, and it is preferably from 3.5 to 3.9 mol / L.

By maintaining the concentration of chloride ions in the aqueous phase of the reaction solution in the range of 3.2 to 4.2 mol / L, the volume ratio of the oil phase to the aqueous phase in the liquid in the reaction tank is reduced. , 1/25
(0.04) or less.

Reaction conditions The reaction between 1,1,2-trichloroethane and alkali hydroxide is preferably carried out at a temperature in the range of 50 to 100 ° C.
When the reaction is carried out at a temperature higher than 100 ° C., by-products of impurities such as MCA may be increased. When the temperature is lower than 50 ° C., the reaction rate is slow and impractical.

This reaction is carried out in a mixed type continuous flow reactor, and the heating is carried out by heating with an external jacket or direct heating by blowing steam.

In addition, since the reaction is carried out in a heterogeneous system of an oil phase and an aqueous phase, and the uneven distribution of alkali hydroxide causes MCA, stirring of the reaction solution is important, and sufficient stirring is performed. Therefore, it is necessary to perform stirring with high stirring efficiency, and it is desirable that the shapes of the baffles and the blades be examined so that effective stirring can be performed.

Further, when introducing the alkali hydroxide into the reaction system, it is desirable to introduce the alkali hydroxide into the circulation system using a static mixer or the like so as not to be locally added.

The method of discharging the reaction solution is an overflow type, the surface of the reaction solution is always kept constant,
It is desirable to continuously measure the pH and the like to control the reaction to proceed steadily.

The produced crude vinylidene chloride distilled from the product recovery reaction system is liquefied in a condenser, and for example, 5-2000 pp of paramethoxyphenol, diethylamine or the like is used as a polymerization inhibitor.
m and stored.

The obtained crude vinylidene chloride can be purified to a purified vinylidene chloride having a purity of 99.9% by mass or more and an MCA content of 1 ppm or less by distillation.

[0027]

The method for producing vinylidene chloride according to the present invention comprises:
When 1,2-trichloroethane is reacted with alkali hydroxide to produce vinylidene chloride, the concentration of chloride ions in the aqueous phase in the liquid in the reaction tank is in the range of 3.2 to 4.2 mol / L. , The volume ratio of the oil phase and the aqueous phase in the liquid in the reaction tank is reduced to 1/25 (0.04) or less.
Even if the reactivity is improved, the effect of suppressing the generation of spontaneously combustible and highly dangerous MCA which is usually produced as a by-product is recognized.

[0028]

EXAMPLE 1 A continuous flow reactor equipped with a stirrer having a capacity of 2500 cc and equipped with a packed tower and a condenser in an overflow tube and a gas system was charged with 6.1 g / l of 1,1,2-trichloroethane.
min, 9.7% caustic soda with a NaCl concentration of 8.1% is introduced at 18.4 g / min. Number of rotation stirring is 1000
The reaction temperature was heated to 67 ° C. by external heating, and hot water at a temperature of about 50 ° C. was flowed into the condenser. The vinylidene chloride gas distilled from the top of the condenser was liquefied in a condenser and collected in an externally cooled tank to which diethylamine was added in advance as a polymerization inhibitor. Nitrogen was supplied at a rate of 360 ml / min into the system. Table 1 below shows the aqueous phase pH, Cl concentration, caustic concentration, alkali conversion, liquid phase / aqueous phase volume ratio, and MCA generation amount in the steady state. The Cl concentration was analyzed by the Horhard method (back titration with silver nitrate), the caustic concentration was analyzed by titration with hydrochloric acid, and the alkali conversion was calculated from the supplied caustic concentration and the caustic concentration in the aqueous phase, and 1,1,2-trichloroethane was used. The (liquid phase) / water phase volume ratio was determined by measuring the overflow liquid.

Comparative Examples 1-2 The results of producing vinylidene chloride under the conditions shown in Table 1 using the continuous flow reactor equipped with a stirrer used in Example 1 are shown in Table 1.

Under the conditions of Comparative Example 1, a large amount of MCA was generated, and under the conditions of Comparative Example 2, the reaction rate was poor.

[0031]

[Table 1]

[0032]

According to the method for producing vinylidene chloride of the present invention, in producing vinylidene chloride from 1,1,2-trichloroethane, 1,1,2-trichloroethane and alkali hydroxide are mixed with chlorine in an aqueous phase. Ion concentration
By keeping the reaction within the range of 3.2 to 4.2 mol / L, monochloroacetylene (MCA), a pyrophoric dangerous substance, can be safely generated without any risk, and compared with the conventional production method. As a result, it can be manufactured several steps efficiently.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) The inventor Manabu Kurita 2-3-1 Fushiki, Takaoka-shi, Toyama F-term in the Takaoka Plant of Toagosei Co., Ltd. 4J011 AB01 JA05 JB01 JB09 JB27

Claims (2)

[Claims] 1. A method according to claim 1, wherein 1,1,2-trichloroethane and an alkali hydroxide are combined with each other to form a chloride ion concentration of 3.2 to 4.2 mol / L in an aqueous phase.
The method for producing vinylidene chloride, characterized in that the reaction is carried out while maintaining the temperature within the range. 2. The method for producing vinylidene chloride according to claim 1, wherein the volume ratio of the oil phase and the aqueous phase in the liquid in the reaction tank is 1:25 to 50.