JP4562888B2 - Method for producing 4,4'-bisphenolsulfone - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing 4,4′-bisphenolsulfone (or 4,4′-dihydroxydiphenylsulfone, hereinafter referred to as 4,4′-BPS) by reacting phenol and sulfuric acid.
[0002]
[Prior art]
4,4′-BPS is a useful compound such as used as a raw material for engineering plastics such as polysulfone (PSF) and polyethersulfone (PES). A method of reacting phenol and sulfuric acid to produce this 4,4′-BPS has been well studied, but the technical problem is mainly how to efficiently remove water. The point was how to reduce the by-product isomer 2,4′-BPS to increase the yield of 4,4′-BPS.
In Japanese Patent Laid-Open No. 3-101656, mesitylene is used as a reaction solvent, phenol and a sulfonating agent are reacted while removing water under reflux, and the reaction proceeds while suspending the produced 4,4′-BPS. A method for producing 4,4′-BPS is disclosed. Mesitylene has the advantage that it does not react with sulfonic acid or the like and dissolves phenol or the like well. However, since mesitylene dissolves 2,4′-BPS, which is a by-product in this reaction, this by-product is present in a significant amount of about 20%, and the yield of 4,4′-BPS is reduced. It is not easy to raise the rate.
In JP-A-51-98239 and JP-A-3-206073, when the reaction of phenol and sulfuric acid is carried out in a solvent such as o-dichlorobenzene or mesitylene, all of the solvent is finally distilled off. Thus, a method for producing 4,4′-BPS is described. In this method, by distilling off the solvent from the reaction system, the isomerization reaction of 2,4′-BPS dissolved in the solvent to 4,4′-BPS can proceed. However, there are problems in that the reaction product obtained after evaporation of the solvent becomes a solid mass that is difficult to handle industrially, and that the reaction conditions must be controlled to adjust the solvent removal rate and the isomerization rate. Become.
[0003]
In addition to these methods, there are methods using an aliphatic hydrocarbon solvent (Japanese Patent Laid-Open No. 64-9970, US Pat. No. 4,996,367, etc.).
When an aliphatic hydrocarbon solvent is used, both 4,4′-BPS and 2,4′-BPS are hardly dissolved in this solvent. The rearrangement to 4′-BPS proceeds, and there is an advantage that a slurry-like product which is industrially easy to handle can be obtained.
For example, US Pat. No. 4,996,367 uses low-boiling hydrocarbons having a boiling point of 70 to 140 ° C. and high-boiling hydrocarbons having a boiling point of 160 to 220 ° C. as solvents, and low-boiling hydrocarbons as azeotropic agents. Disclosed is a method of returning a phenol layer to a reaction system among at least two liquid layers obtained by distillation and condensation. Since this phenol layer is the heaviest and lower layer, it is said that reflux is easy. A preferred solvent is a combination of Isopar (registered trademark of Exxon Chemical Co., Ltd.) E and Isopar H. When refluxing in a reaction system using this solvent, the condensate is usually separated into three layers of phenol / water / aliphatic hydrocarbon, so the phenol and aliphatic hydrocarbon solvent are removed from the reaction layer while removing the aqueous layer. The problem is that it is not easy to return to.
[0004]
[Problems to be solved by the invention]
The present invention relates to a method for producing 4,4′-BPS, in which phenol and sulfuric acid are reacted under reflux in an aliphatic saturated hydrocarbon solvent, and the high yield of 4,4′-BPS in the reaction step and the subsequent steps. It is an object of the present invention to provide a production method capable of efficiently removing by-produced water and improving the yield of 4,4′-BPS by using an appropriate mixed solvent that brings about the above.
[0005]
[Means for Solving the Problems]
In the present invention, phenol and sulfuric acid are reacted under reflux while removing water in a mixed solvent composed of a solvent having a boiling point of 175 ° C. or higher and an aliphatic saturated hydrocarbon and phenol having a boiling point of 170 ° C. or lower, This is a method for producing 4,4′-bisphenolsulfone, in which the phenol is dissolved and the solvent having a boiling point of 170 ° C. or less is distilled off from the reaction system. After completion of the reaction, it is preferable to dissolve phenol and distill off the solvent having a boiling point of 170 ° C. or less from the reaction system.
The solvent used in the present invention is a mixed solvent composed of one or more aliphatic saturated hydrocarbons having a boiling point of 175 ° C. or higher and mesitylene.
When the aliphatic saturated hydrocarbon is a mixed solvent, the distillation temperature of the mixed solvent is 175 ° C. or higher. Examples of the solvent include Isopar (registered trademark of Exxon Chemical Co., Ltd.) H, Isopar L, and Isopar M. Of these, Isopar H is preferred.
[0006]
Examples of the solvent in which the phenol of the present invention is dissolved and has a boiling point of 170 ° C. or lower include mesitylene and chlorobenzene, and mesitylene is preferable. By using such a solvent that dissolves phenol, water, phenol, and solvent distilled during dehydration become two layers, and handling and removal of water become extremely easy.
Although there is no restriction | limiting in particular in the ratio of the aliphatic saturated hydrocarbon and mesitylene in this mixed solvent, 0.1-10 weight part of mesitylene is preferable with respect to 1 weight part of aliphatic saturated hydrocarbon, Preferably it is 0.5-1.2. It can be used in parts by weight.
[0007]
In particular, it is well known that mesitylene is effective for removing water as an azeotropic agent when 4,4′-BPS is produced by reacting phenol and sulfuric acid. When mesitylene is used as a solvent, phenol and the like are dissolved well. Therefore, when water is removed by distillation, which is essential in this dehydration reaction, the distilled phenol and mesitylene are in one layer and the specific gravity is lighter than water. It is very easy to return the phenol and mesitylene, which are lightly upper layers, to the reaction system while removing the aqueous layer.
However, when only mesitylene is used as a reaction solvent, there arises a problem that the rearrangement reaction to 4,4′-BPS does not proceed and the yield decreases due to the property that mesitylene dissolves 2,4′-BPS.
[0008]
On the other hand, since the aliphatic saturated hydrocarbon solvent hardly dissolves the 2,4′-isomer, the transition from the 2,4′-isomer to the 4,4′-isomer is promoted. Many isomers can be obtained.
When the dehydration reaction is performed under reflux, if only the low-boiling point aliphatic hydrocarbon solvent is used, the condensate is separated into three layers in the order of phenol / water / hydrocarbon from the bottom. However, when the solvent of the present invention is used, the condensate is separated into two layers of water / phenol and mesitylene from the bottom, so that water can be efficiently removed in the dehydration reaction. As a result, 4,4′-BPS can be produced efficiently. Further, after the dehydration reaction, mesitylene is distilled off from the reaction system to promote the rearrangement reaction, and high-purity 4,4′-BPS suspended in an aliphatic saturated hydrocarbon can be obtained.
[0009]
According to the present invention, in the first half of the dehydration reaction, the presence of a relatively low boiling point solvent such as mesitylene in one of the mixed solvents facilitates the removal of water and simplifies the reflux operation. In the rearrangement reaction, this low boiling point solvent is distilled off to make a solvent composed of aliphatic saturated hydrocarbons, thereby promoting the rearrangement reaction to 4,4′-BPS and increasing the yield of 4,4′-BPS. Can do. By using the mixed solvent of the present invention, problems with conventional solvents can be solved and many advantages can be achieved at once.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The relationship between the transition from the 2,4′-isomer to the 4,4′-isomer and the temperature is shown in FIG.
Here, a mixture of (4,4′-BPS), 2,4′-BPS and phenolsulfonic acid in a weight ratio of 20: 1 is suspended in an isopar solvent, and the production ratio of the 4,4′-isomer is determined at each temperature.・ Measured by high performance liquid chromatography (HPLC) every hour. As can be seen from this figure, the transition rate differs greatly between 150 ° C. and 160 ° C., and the production of 4,4′-isomer increases. That is, the yield of the 4,4′-isomer can be increased by proceeding the reaction at a temperature higher than this temperature.
From these facts, the boiling point of the aliphatic saturated hydrocarbon solvent is higher than this temperature, preferably significantly higher than the boiling point of mesitylene (about 162 ° C.), and particularly preferably about 175 ° C. or higher. .
[0011]
In this invention, the 4,4′-BPS production reaction is generally carried out as follows.
A mixed solvent composed of a solvent having a boiling point of 170 ° C. or lower is prepared by dissolving a phenol such as an aliphatic saturated hydrocarbon and mesitylene in a reaction vessel. Phenol and sulfuric acid are gradually added to this, but these may be added simultaneously, or sulfuric acid may be gradually added after the required amount of phenol is added. The amount of phenol is finally such that the molar ratio of phenol and sulfuric acid is in the range of 2-3: 1, preferably approximately 2: 1. On the other hand, the ratio of the solvent in the reaction solution is set to be 1 to 3 times the weight of sulfuric acid, particularly about 2 times.
The reaction is carried out in the temperature range of about 145 to about 175 ° C.
[0012]
In this reaction, the first half is a dehydration reaction, and water produced at the above reaction temperature is azeotropically distilled with mesitylene to dissolve phenol such as water and mesitylene and distill the solvent and phenol having a boiling point of 170 ° C. or less. When this is condensed, it is separated into two layers, an aqueous layer and a phenol-dissolved layer. When mesitylene is used, since this phenol-dissolved layer is light, the water layer becomes the lower layer, and water can be easily removed from the lower part. The distilled phenol can be continuously returned to the reaction system as a solution with a solvent.
This reflux is carried out until it is confirmed that the dehydration reaction has been completed due to the distillation of the theoretical amount of water, and then the reflux is stopped and a low boiling point (170 ° C. or lower) solvent such as mesitylene is distilled from the reaction system. Leave. A solvent having a boiling point in this range can be easily distilled off.
At this time, approximately the same amount of an aliphatic saturated hydrocarbon solvent as mesitylene to be distilled off may be further added.
[0013]
As described above, since the low boiling point solvent such as mesitylene is removed from the solvent in the latter half of the reaction, the solvent is almost an aliphatic saturated hydrocarbon. In this solvent, the transfer reaction from 2,4′-BPS to 4,4′-BPS is promoted, and the yield of 4,4′-BPS is finally improved.
By the above operation, a slurry in which the crystallized product is suspended in a hydrocarbon solvent is obtained. Any known method may be used to recrystallize 4,4′-BPS from this solvent layer.
For example, it is possible to extract the product with methanol using the fact that the solvent is a hydrocarbon.
[0014]
Specifically, approximately the same amount of methanol is added to the solvent layer and dissolved at about 65 ° C. for about 1 hour. This methanol may be a pure product or an aqueous solution. In the case of a pure product, the same amount of water may be further added. A mixture of the product 4,4′-BPS and the 2,4′-isomer is dissolved in methanol. In addition, since the solvent of the present invention is poorly compatible with methanol, both are separated into two transparent layers after the addition of methanol. The separated solvent layer is easily separated and contains no products or impurities, so that it can be easily reused. Activated carbon, caustic soda, or the like may be added to the methanol layer to remove impurities or adjust pH.
Thereafter, water is added to the methanol layer and cooled to near room temperature, and 4,4′-BPS can be recrystallized and dried to obtain 4,4′-BPS. Since the 2,4′-isomer is more soluble in methanol than 4,4′-BPS, the proportion of the 4,4′-isomer in the crystal can be increased to 99% or more.
[0015]
【Example】
Example 1
A 500 ml four-necked flask equipped with a stirrer, a thermometer, and a water separation tube was charged with 98.7 g (1.05 mol) of phenol, 75 ml of Isopar H, and 50 ml of mesitylene, and 51.6 g of 95% sulfuric acid was added to the mixture with stirring. 0.50 mol) was added dropwise at 50 ° C. and the temperature was raised.
Distillation of the reaction liquid started from around 148 ° C., the distillate was condensed and separated into two layers by a water separation tube, and the upper organic layer was continuously returned to the reaction system. In about 4 hours from the temperature increase, the temperature of the reaction system became 170 ° C., the generation of water was stopped, and the amount of water separated by the water separation tube was 20.5 g. Thereafter, 50 ml of Isopar H was added, and mesitylene was distilled off over 3 hours until the temperature of the reaction system reached 175 ° C. The composition of this reaction product was analyzed by high performance liquid chromatography (HPLC). As a result, the relative area ratio (measurement wavelength: 231 nm) was 4,4′-BPS 94.7%, 2,4′-BPS 2.8%. Phenol sulfonic acid 1.2%.
[0016]
Comparative Example 1
A 500 ml four-necked flask equipped with a stirrer, thermometer and water separation tube was charged with 98.7 g (1.05 mol) of phenol and 100 ml of Isopar G, and 51.6 g (0.50) of 95% sulfuric acid was added to the mixture with stirring. Mol) was added dropwise at 50 ° C. and the temperature was raised. Distillation of the reaction liquid starts from around 144 ° C., and this distillate is condensed and separated into three layers of a water separation tube, an upper layer is a solvent layer, an intermediate layer is an aqueous layer, and a lower layer is a phenol layer. The upper solvent layer was continuously returned to the reaction system, and the lower phenol layer was withdrawn every 15 minutes and returned to the reaction system. About 7 hours after the temperature rise, the temperature of the reaction system reached 167 ° C., the generation of water stopped, the amount of water separated by the water separation tube was 21.2 g, and the total amount of phenol returned to the reaction system was 68.0 g. there were. As a result of analyzing the composition of this reaction product by high performance liquid chromatography (HPLC), it was found that the relative area ratio (measurement wavelength: 231 nm) was 4,4′-BPS 94.0%, 2,4′-BPS 3.1%. The phenol sulfonic acid was 1.6%.
[0017]
【The invention's effect】
As described above, the production method of the present invention comprises a mixed solvent composed of a solvent having a boiling point of 170 ° C. or less by dissolving one or more aliphatic saturated hydrocarbons having a boiling point of 175 ° C. or more and phenol such as mesitylene. It is characterized by using a mixed solvent, and low-boiling solvents such as mesitylene function as an azeotropic agent. Furthermore, since this solvent dissolves phenol, there are two layers to distill when dehydrating, so dehydration reaction The water removal is performed very efficiently, so that the reflux operation is facilitated. Since the low boiling point solvent such as mesitylene is distilled off after completion of the dehydration reaction, the yield of 4,4′-BPS can be increased by promoting the rearrangement reaction in the aliphatic saturated hydrocarbon solvent. In the present invention, such many advantages can be easily achieved at once by using one kind of mixed solvent.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the transition from 2,4′-isomer to 4,4′-isomer and temperature.

Claims (4)

Phenol and sulfuric acid are dissolved in an aliphatic saturated hydrocarbon having a boiling point of 175 ° C or higher and a mixed solvent composed of a solvent having a boiling point of 170 ° C or lower and reacted under reflux while removing water to dissolve the phenol. A process for producing 4,4′-bisphenolsulfone, wherein a solvent having a boiling point of 170 ° C. or less is distilled off from the reaction system. The production method according to claim 1, wherein after the reaction is completed, the phenol is dissolved and a solvent having a boiling point of 170 ° C or lower is distilled off from the reaction system. The production method according to claim 1 or 2, wherein the solvent in which the phenol is dissolved and the boiling point is 170 ° C or lower is mesitylene. The manufacturing method according to any one of claims 1 to 3, wherein the aliphatic saturated hydrocarbon is Isopar (registered trademark of Exxon Chemical Co., Ltd.) H.

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