JPH06116231A - Purification of 4,4'-dichlorodiphenylsulfone - Google Patents

Abstract

PURPOSE:To provide the purification method capable of efficiently separating unreacted chlorobenzene sulfonic acid and of obtaining highly pure 4,4'- dichlorodiphenylsulfone. CONSTITUTION:A reaction product mixture produced by bringing chlorobenzene into contact with 4-ehlorobenzene sulfonic acid is mixed with water in such a volume as to give a chlorobenzene:4-chlorobenzene sulfonic acid molar ratio of 1:0.8 to 1:2.0, and the deposited chlorobenzene sulfonic acid hydrate is separated. Crude dichlorodiphenylsulfone separated from the remaining solution is recrystallized with alcohol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing highly pure 4,4'-dichlorodiphenylsulfone which is useful as a raw material monomer for heat-resistant resins such as synthetic intermediates for medical and agricultural chemicals and dyes and polysulfone.

[0002]

BACKGROUND OF THE INVENTION It is known to produce dichlorodiphenyl sulfone by condensing chlorobenzene and 4-chlorobenzenesulfonic acid at high temperature. However, it is difficult to make the conversion rate and selectivity 100% in this reaction, and in addition to 4,4'-dichlorodiphenylsulfone, which is usually the objective, a considerable amount of 4-chlorobenzenesulfonic acid remains, and further, By-products such as 2,4'-dichlorodiphenyl sulfone and 3,4'-dichlorodiphenyl sulfone are mixed, and the reaction solution is markedly colored from brown to black.

Conventionally, in order to obtain dichlorodiphenyl sulfone from this reaction product, a large amount of water has been added to wash and remove 4-chlorobenzenesulfonic acid. It was industrially disadvantageous to remove a large amount of water in order to recover and reuse 4-chlorobenzenesulfonic acid from this washing aqueous solution.

As a method for improving this problem, a special table
In 1-500672, a small amount of water is added to the reaction product,
Form a heavier aqueous phase containing 4-chlorobenzenesulfonic acid and an organic phase containing dichlorodiphenylsulfone, separate the aqueous phase from the lighter organic phase and dehydrate the aqueous phase.
A method for recovering and reusing 4-chlorobenzenesulfonic acid is disclosed. According to this method, 4-chlorobenzenesulfonic acid recovered compared to the conventional method contains only a small amount of water, and therefore dehydration is said to be easy, but the essence is extraction and liquid separation operations, and the separation efficiency is not always required. Not good.

On the other hand, Japanese Patent Publication No. 55-44743 discloses a method for producing dichlorodiphenyl sulfone by bringing chlorobenzene and 4-chlorobenzenesulfonic acid into contact with each other at a high temperature as described above. It is generally impossible to make the selectivity of 4,4'-dichlorodiphenyl sulfone 100% by this method, and the selectivity of 4,4'-form is usually around 90%. And 3,4'-bodies are produced as by-products in the range of several to ten and several percent. The 4,4'-form is not only useful as a synthetic intermediate for medicines and agricultural chemicals and dyes, but also in recent years, the demand as a polysulfone raw material monomer is increasing. It is well known to those skilled in the art that when used as a monomer, a 4,4′-form having a higher degree of purity and a lower degree of coloration is desirable in view of requirements such as polymerization degree, physical properties and color stability of the polymer.

As a method for separating and recovering 4,4'-dichlorodiphenylsulfone from a chlorobenzene solution containing dichlorodiphenylsulfone, a method of completely or partially distilling chlorobenzene is known. However, the solubility of 4,4'-dichlorodiphenyl sulfone in chlorobenzene is relatively large, and if one tries to increase the purity,
There is a dilemma that yield is decreasing. The method of lowering the deposition temperature with a cooler or the like reduces the industrial appeal. Further, 4,4'-dichlorodiphenyl sulfone precipitated from chlorobenzene is inferior in color tone as a polymer polymerization grade and is not satisfactory.

[0007]

The object of the present invention is to recover unreacted 4-chlorobenzenesulfonic acid with high efficiency from a reaction mixture obtained by reacting chlorobenzene and 4-chlorobenzenesulfonic acid, and to obtain 4-chlorobenzenesulfonic acid. 4, which has a higher purity than the chlorobenzene solution after separation of
A method for separating 4'-dichlorodiphenyl sulfone with high yield is provided.

[0008]

The present invention provides a method for producing dichlorodiphenyl sulfone by catalytically reacting chlorobenzene and 4-chlorobenzenesulfonic acid, wherein the reaction product mixture has a molar ratio of 4-chlorobenzenesulfonic acid and water. The amount of water is 1: 0.8-1: 2.0, the chlorobenzenesulfonic acid hydrate is precipitated and separated, and the crude dichlorodiphenylsulfone separated from the solution is recrystallized with alcohol. The present invention relates to a method for purifying '-dichlorodiphenyl sulfone.

The raw material 4-chlorobenzenesulfonic acid used in the present invention is produced by the reaction of conventionally well-known chlorobenzene with a sulfonating agent such as fuming sulfuric acid, anhydrous sulfuric acid, concentrated sulfuric acid, or chlorosulfonic acid. be able to.

The method for producing dichlorodiphenyl sulfone by contacting chlorobenzene and 4-chlorobenzenesulfonic acid of the present invention is a method of reacting chlorobenzene with 4-chlorobenzenesulfonic acid using a known condensing agent, catalyst or the like. Alternatively, there is a method of contacting chlorobenzene and 4-chlorobenzenesulfonic acid at high temperature under normal pressure or pressure without using a condensing agent, a catalyst, etc., and dichlorodiphenylsulfone which is a reaction product and unreacted 4-chlorobenzenesulfonic acid. A reaction product mixture containing and can be obtained.

In the present invention, a part of the reaction product mixture is sampled to determine the contents of unreacted 4-chlorobenzenesulfonic acid and the reaction product dichlorodiphenylsulfone. The analysis method is not particularly limited, for example, by adding an appropriate amount of water to the sample, extracting and separating, the amount of 4-chlorobenzenesulfonic acid can be determined by acid-base titration of the aqueous phase, and the organic phase can be concentrated. Thus, the amount of dichlorodiphenyl sulfone and the amount of chlorobenzene can be conveniently determined. Sulfuric acid is generally present in this reaction system in small amounts and can be ignored.

In the present invention, the amount of chlorobenzene is adjusted in consideration of the solubility of dichlorodiphenyl sulfone in chlorobenzene. That is, if the unreacted chlorobenzene remaining in the reaction product mixture is insufficient to dissolve the total amount of dichlorodiphenyl sulfone produced, chlorobenzene is added, and if it remains in excess, it is distilled off.
The amount of chlorobenzene is preferably the minimum amount necessary to dissolve the produced dichlorodiphenyl sulfone,
The amount is not limited to this, and an arbitrary amount may be increased. However, it is not preferable to add too much, because the separation efficiency will decrease.

Water was added to the reaction mixture product to react the unreacted product.
4-Chlorobenzenesulfonic acid is precipitated as a hydrate. The amount of water added is 0.8 to 2.0 molar equivalents with respect to 1 mol of unreacted 4-chlorobenzenesulfonic acid, preferably
It is 0.9 to 1.2 molar equivalents. If it is less than this range, the precipitation of 4-chlorobenzenesulfonic acid hydrate is not sufficient, and if it is more than this range, the precipitate deliquesces or becomes an aqueous solution, resulting in poor filtration efficiency.

Since the melting point of 4-chlorobenzenesulfonic acid is 101 ° C., the separation of the hydrate can be carried out at a temperature lower than each temperature.
35 ° C is preferred. The 4-chlorobenzenesulfonic acid hydrate crystallized and separated by the above method has a high purity, is dehydrated by an appropriate method, and is reused in the condensation reaction with chlorobenzene.

On the other hand, the chlorobenzene solution after separation of 4-chlorobenzenesulfonic acid hydrate contains a trace amount of 4-chlorobenzenesulfonic acid and sulfuric acid. These are desirably removed before the separation operation of 4,4'-dichlorodiphenyl sulfone. This removal is easily accomplished by washing with water or neutralization with alkali. The alkali neutralization is achieved by, for example, but not limited to, adding sodium carbonate powder to the chlorobenzene solution, stirring vigorously, and filtering off the salt formed and the excess sodium carbonate.

Dichlorodiphenyl sulfone is precipitated from the chlorobenzene solution containing dichlorodiphenyl sulfone thus obtained. At this time, the weight ratio of dichlorodiphenyl sulfone and chlorobenzene was 1: 2 to 1:
It is preferably concentrated to 0.5. If the amount of chlorobenzene is greater than this range, the amount of dichlorodiphenyl sulfone deposited will decrease, and the recovery rate will decrease. On the other hand, if the amount is less than this range, the fluidity of the produced slurry is poor, the workability is lowered, and the process is disadvantageous.

The temperature and pressure for concentrating chlorobenzene are not particularly limited as long as chlorobenzene is distilled off. The concentrated slurry or solution is preferably cooled in order to sufficiently precipitate dichlorodiphenyl sulfone. During this period, it is desirable that the slurry is agitated in order to maintain the fluidity of the resulting slurry. The cooling temperature is 0 to 50 ° C, preferably 5 to 35 ° C. When it is higher than this range, the precipitation of dichlorodiphenyl sulfone is not sufficient, and when it is low, the cost of cooling becomes high.

The obtained slurry is solid-liquid separated by a suitable method such as centrifugation or filtration. At this time, washing the obtained solid with an arbitrary amount of chlorobenzene is effective in improving the purity and decoloring of the obtained dichlorodiphenyl sulfone, but if the amount of chlorobenzene used for washing is excessively increased, dichlorodiphenyl dissolved in the washing liquid is dissolved. It is not preferable because the sulfone increases. The resulting solid (crude dichlorodiphenyl sulfone) is dried by a suitable method. On the other hand, the cleaning solution can be reused,
For example, it can be mixed at the next concentration operation,
The reuse method is not limited to this.

The crude dichlorodiphenyl sulfone obtained by the above operation is recrystallized using an alcohol solvent and purified. Examples of alcohols include methanol, ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, t-butanol, ethylene glycol and monoalkylene ethers thereof, and preferably ethanol and isopropanol. These may be used alone or as a mixture, but considering recovery and reuse, it is advantageous to use them alone.

The operating temperature of recrystallization is reasonable between 0 ° C. and the boiling point of the alcohol used. Specifically, the temperature at which the crude dichlorodiphenyl sulfone is dissolved is 60 ° C. and the boiling point of the alcohol used, and the precipitation temperature is 5 ° C. ~ 35 ° C is preferred. The amount of alcohol used is not particularly limited and may be arbitrarily increased, but if added excessively, the recovery efficiency of the purified 4,4′-dichlorodiphenyl sulfone obtained is unfavorable. The minimum amount required to completely dissolve the crude dichlorodiphenyl sulfone at the temperature at which it is dissolved is preferred.

When recrystallizing from alcohol, activated carbon may be used for the purpose of purification and decolorization. That is,
When crude dichlorodiphenyl sulfone was dissolved in alcohol, an arbitrary amount of activated carbon was added, and after adsorption operation, this was filtered off and the solution was cooled to precipitate 4,4'-dichlorodiphenyl sulfone. it can. Deposited 4,
4'-Dichlorodiphenyl sulfone is separated by a suitable method such as centrifugation or filtration. At this time, it is free to wash the obtained solid with an arbitrary amount of alcohol, but it is not preferable to use an excessive amount because the recovery efficiency decreases. The resulting 4,4'-dichlorodiphenyl sulfone is dried by a suitable method to give a product. This is satisfactory for polymerization of purity and color. On the other hand, the mother liquor can be reused as a solvent for the next recrystallization as long as the purity of 4,4′-dichlorodiphenyl sulfone obtained satisfies the allowable value.

[0022]

Industrial Applicability According to the present invention, unreacted chlorobenzenesulfonic acid can be efficiently separated from a reaction product mixture produced by contacting chlorobenzene and chlorobenzenesulfonic acid to produce dichlorodiphenylsulfone. It is possible to obtain high-purity 4,4′-dichlorodiphenyl sulfone useful as a raw material monomer of a heat-resistant resin such as a body and polysulfone.

[0023]

EXAMPLES Examples of the present invention will be described below. Example 1 Chlorobenzene (505.9 g), 4-chlorobenzenesulfonic acid
(547.8g), dichlorodiphenyl sulfone (19.5g), sulfuric acid
(1.7 g) and water (0.2 g) are continuously fed at a rate of 200 g / hr to a glass bead-filled reactor (24 Φ × 1200 mm) heated to 250 ° C to react, and the reaction is performed from the bottom of the reactor. Product 10
64.5g was extracted. The composition of this reaction mixture was as follows. Chlorobenzene: 464.3g 4-Chlorobenzenesulfonic acid: 473.4g Dichlorodiphenylsulfone: 115.7g Water: 4.7g Sulfuric acid: 6.4g The isomer ratio in dichlorodiphenylsulfone is:
4,4'-body was 89.34%, 2,4'-body was 6.67%, and 3,4'-body was 4.00%.

432.4 g of this reaction mixture was taken, 453 g of chlorobenzene was added thereto, and 15.9 g of water was added dropwise with good stirring. 4-Chlorobenzenesulfonic acid hydrate precipitates with heat generation. After cooling to room temperature with stirring, the mixture is filtered. By this operation, 191.7 g of unreacted 4-chlorobenzenesulfonic acid was separated. It contained 0.04 g of dichlorodiphenyl sulfone.

On the other hand, the filtrate contained 47.02 g of dichlorodiphenyl sulfone and 0.5 g of 4-chlorobenzenesulfonic acid. This chlorobenzene solution was washed twice with 250 ml of water, and when the organic layer was separated, the weight of the organic phase was 540 g. From this organic phase, 493 g of chlorobenzene was distilled off, and the residue was cooled to 25 ° C. The residual slurry was separated by suction filtration into crude dichlorodiphenyl sulfone and chlorobenzene filtrate (filtrate). At this time, it was washed with 12 g of chlorobenzene. Vacuum drying yielded 33.29 g of crude 4,4'-dichlorodiphenyl sulfone.

The above crude dichlorodiphenyl sulfone was added to 233 g of ethanol, heated and dissolved, and then cooled to 25 ° C. The 4,4'-dichlorodiphenyl sulfone deposited by suction filtration was separated and washed with 70 g of ethanol. The filtrate was recovered (filtrate). 27.77g purified by vacuum drying
4,4'-dichlorodiphenyl sulfone was obtained. The purity of 4,4'-form was 99.99% by gas chromatography.
(2,4'-body 0.01%, 3,4'-body trace)

Example 2 432.4 g of the reaction mixture of Example 1 was taken and unreacted 4-chlorobenzenesulfonic acid hydrate was separated by the same operation, while the chlorobenzene solution was washed with water. When the filtrate of Example 1 was added to this chlorobenzene solution, the weight was 585 g.
Met. From this solution, 525 g of chlorobenzene was distilled off. The distillation residue was cooled to 25 ° C. and the resulting slurry was suction filtered to separate crude dichlorodiphenyl sulfone and washed with 12 g of chlorobenzene. Vacuum drying yielded 37.60 g of crude dichlorodiphenyl sulfone.

This crude dichlorodiphenyl sulfone was added to the filtrate of Example 1, dissolved by heating, and then cooled to 25 ° C. The deposited 4,4'-dichlorodiphenyl sulfone was separated by suction filtration and washed with 70 g of ethanol. By vacuum drying, 34.80 g of purified 4,4'-dichlorodiphenyl sulfone was obtained. The purity of 4,4'-form was 99.90% by gas chromatography. (2,4'- body 0.03%, 3,4'- body
0.07%)

Claims (1)

[Claims] 1. A method for producing dichlorodiphenyl sulfone by catalytically reacting chlorobenzene and 4-chlorobenzenesulfonic acid, wherein the reaction product mixture has a molar ratio of 4-chlorobenzenesulfonic acid to water of 1: 0.8 to 1: 2.0. Chlorobenzenesulfonic acid hydrate is precipitated by adding water in an amount such that the crude dichlorodiphenylsulfone separated from the solution part is recrystallized with alcohol.
A method for purifying 4,4'-dichlorodiphenyl sulfone.