JPH0676349B2 - Method for purifying 4,4'-dihydroxydiphenyl ether - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for purifying 4,4′-dihydroxydiphenyl ether, and more particularly to 4,4′-dihydroxydiphenyl ether using a specific solvent under specific crystallization conditions. The present invention relates to a method for highly efficient purification of lactic acid.

Technical background of the invention and its problems 4,4'-dihydroxydiphenyl ether (hereinafter sometimes abbreviated as DHPE) is expected to be used as a raw material for polymers or organic chemicals. This DHPE condenses hydroquinone (another name for 1,4-dihydroxybenzene, sometimes abbreviated as HQ below) as a raw material in the presence of a solid acid catalyst such as synthetic mica, activated clay, montmorillonite, and an ion exchange resin. It is known that it can be manufactured by In this condensation reaction, a non-aqueous solvent such as xylene or toluene is generally used. For reference, the synthetic reaction of DHPE can be shown by the formula as follows.

When DHPE is synthesized by the method as described above, the reaction mixture obtained after the reaction contains DHPE, HQ, a solid acid catalyst, and a non-aqueous solvent such as an aromatic hydrocarbon. Various methods have been conventionally proposed to separate DHPE, which is the target compound, from this reaction mixture.However, DHPE can be obtained as crude crystals together with various reaction by-products by any of these methods. It needs to be purified to increase its purity.

As a conventionally proposed method for purifying DHPE, Japanese Patent Laid-Open No.
-55635 discloses a method of recrystallizing crude crystals of DHPE using xylene as a crystallization solvent, but the publication discloses that recrystallization can be performed in about 2-3 times the amount of solvent. It is only shown, but not at what temperature the crystallization is carried out. Further, regarding the purification method of DHPE shown in the publication, the raw material DHPE used for recrystallization is one whose purity has been increased up to 99% by preliminary vacuum distillation. Is used as a raw material for recrystallization in
There is a problem that even if this method is used for a substance such as DHPE having a purity of DHPE of usually less than 90%, the purity of DHPE cannot be increased to a high degree of purity for efficient purification.

Further, U.S. Pat.No. 4,306,094 describes a method in which a crude product of DHPE containing unreacted HQ and triphenyl ether is washed with warm water to remove HQ, and then recrystallized from a solvent. There is no specific indication in the specification of what this recrystallization solvent is and the resulting DHPE
The purity of is unknown.

The present inventors acknowledged the problems associated with the conventional techniques as described above, and in obtaining high-purity DHPE, not only simply increasing the purity of DHPE but also establishing an economical industrial DHPE separation process. Therefore, a method for separating and purifying DHPE that enables efficient recovery of DHPE with a high yield under conditions where the use ratio of the recrystallization solvent to the crude DHPE as a raw material can be minimized was examined. As a result, they have found that the crystallization operation may be performed under a specific condition using a specific solvent system, and have completed the present invention.

OBJECT OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, and provides a high recovery rate and high purity of DHPE from low-purity DHPE crude crystals obtained by the reaction of hydroquinone. Therefore, it is an object of the present invention to provide a method for separating and purifying DHPE that can be efficiently recovered.

SUMMARY OF THE INVENTION The method for purifying 4,4′-dihydroxydiphenyl ether (DHPE) according to the present invention is a low-purity DHPE crude crystal obtained by a reaction of hydroquinone, using halogen-substituted benzene, toluene or xylene as a crystallization solvent. , 70 ~ 90
It is characterized by being crystallized in a temperature range of ° C.

DETAILED DESCRIPTION OF THE INVENTION The method for purifying DHPE according to the present invention will be specifically described below.

The crude crystals of DHPE purified by the present invention are obtained by dehydration dimerization of hydroquinone. The crude hydroquinone crystals contain, as impurities, high-boiling-point by-products such as hydroquinone trimer, hydroquinone multimer, and unreacted hydroquinone.

When hydroquinone is dehydrated and dimerized to produce DHPE, solid acid catalysts such as synthetic mica, activated clay, montmorillonite and ion exchange resins, or liquid acid catalysts such as protonic acids are used. In order to obtain crude crystals of DHPE from the reaction mixture obtained after the reaction, conventionally known methods can be widely adopted, and the method found by the present inventors can also be used. That is, dehydration dimerization reaction of hydroquinone is carried out using a water-immiscible solvent, after removing the solid acid catalyst from the resulting liquid reaction mixture containing unreacted hydroquinone, the reaction mixture is preferably 55 ℃ or more, more preferably Hydroquinone and DHPE are transferred to an aqueous phase by contacting with water at a temperature of 70 to 90 ° C., the aqueous phase is separated, and then the aqueous phase is preferably cooled to 50 ° C. or lower to obtain DHPE crude crystals. Alternatively, the dehydration dimerization reaction of hydroquinone is carried out using a water-immiscible solvent, water is added to the resulting liquid reaction mixture containing unreacted hydroquinone, and this is then preferably carried out.
A DHPE crude crystal can also be obtained by precipitating a DHPE crude crystal while maintaining the temperature at 70 ° C. In some cases, the dehydration dimerization reaction of hydroquinone is carried out using a water-immiscible solvent, and the resulting liquid reaction mixture containing unreacted hydroquinone is cooled as it is.
It is also possible to obtain PE crude crystals.

The DHPE crude crystal thus obtained is, as described above,
Since it contains a large amount of unreacted hydroquinone, hydroquinone trimer and hydroquinone multimer, it is purified by the purification method according to the present invention.

According to the method of the present invention, the DHPE purity of the raw DHPE crude crystals used in the method for purifying DHPE is 90% by weight or less, even if DHPE crude crystals are used, the purity is usually 95% by weight or more. It can be easily increased.

In the present invention, crude DHPE crystals are purified using halogen-substituted benzene, toluene or xylene as a crystallization solvent. Specific examples of halogen-substituted benzenes are chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, o-
Examples include chlorotoluene and p-chlorotoluene.

When cumene or mesitylene, for example, is used as the crystallization solvent, high-purity DHPE cannot be recovered with a high recovery rate even if the temperature during crystallization and the use ratio of the crystallization solvent are variously changed. . Even if xylene is selected as the crystallization solvent, high-purity DHPE can be recovered with a high recovery rate when the crystallization operation is carried out at the temperature used for normal crystallization operation, for example, 20 to 60 ° C. You cannot do it.

In the present invention, DHPE crude crystals are 70 to 90 ° C using the crystallization solvent.
DHPE is usually purified by crystallization in the temperature range of
It can be obtained with 95% by weight or more and a recovery rate of 90% or more. To further explain this point, when the temperature during the crystallization operation is less than 70 ° C, the purity of DHPE is usually 95% by weight.
In order to achieve the above, the target value of the purity can be achieved by increasing the ratio (B / A) of the weight A of crude DHPE crystals to the weight B of the crystallization solvent used, but the amount B of the crystallization solvent is increased. The recovery of DHPE and DHPE generally decreases, and even when the crystallization solvent of the present invention is used, high-purity DHPE is usually 90
It cannot be recovered at a weight percentage or more.

On the other hand, when the crystallization temperature is increased, the DHPE purity tends to increase and the DHPE recovery rate tends to decrease even if the crystallization solvent is used in the same proportion. And as can be estimated from the data of the present invention which was investigated about how the use ratio of the crystallization temperature and the crystallization solvent affects the purity and recovery of DHPE, when the crystallization temperature is increased, It is possible that the purity and recovery rate of DHPE can be made to the high purity and high recovery rate that are the targets of the present invention even if the proportion of crystallization solvent used is reduced, but it is possible to separate DHPE on an industrial scale. In the case of carrying out, it is usually difficult to raise the temperature of equipment used for industrial separation operations such as a centrifuge above 90 ° C., and therefore the crystallization temperature is also set in the present invention. 90 ° C
Will be done below.

In the present invention, the use ratio (B / A) of the crystallization solvent (B) to the DHPE crude crystal (A) is usually expressed as a weight ratio of 3
Crystallization is performed under the conditions of ~ 15. If the crystallization temperature is increased within the above range, the use ratio of the crystallization solvent can be reduced.
The purity and recovery of DHPE can be achieved with the high purity and high recovery of the present invention.

In the present invention, the crystallization operation described above may be carried out twice or more, if necessary.

EFFECTS OF THE INVENTION According to the method for purifying DHPE of the present invention, DHPE can be purified with high purity and high recovery rate, and therefore the method is significant in purifying DHPE on an industrial scale.

Examples The present invention will be described below with reference to Examples and Reference Examples, but the present invention is not limited to these Examples and Reference Examples.

First, the present invention will be described with reference to a method for producing crude DHPE crystals, and then a method for purifying the crude DHPE crystals obtained according to the reference example.

Reference Example 1 (1) 1000 g of a 10 wt% aqueous suspension of sodium tetrasilicic mica, which is a synthetic mica manufactured by Topy Industries, Ltd., was suspended in 10 liters of water, and 5 ml of 5% -Al (NO ₃ ) ₃ aqueous solution was stirred while stirring well.
Was added, and the mixture was further stirred for 25 minutes to perform ion exchange with an aluminum mold. The synthetic mica ion-exchanged into the aluminum mold was recovered by centrifugation, washed well with water, and dried (40 ° C, 50 mmHg, 10 hours).

A solid acid catalyst thus prepared, aluminum-exchanged synthetic mica (ion exchange rate: 45%) 80 g, hydroquinone (HQ) 400 g, and mesitylene 2500 ml were charged into a 5-liter four-necked flask, and Dean-Stark water was collected. A hydroquinone dimerization reaction was performed by heating and stirring under reflux of mesitylene for 2 hours while removing water generated during the reaction by attaching an trap to the outside of the system by azeotropic distillation with mesitylene.

(2) After completion of the reaction, the reaction mixture was filtered at 150 ° C. to separate the solid acid catalyst and the reaction solution. 2420 g of this separated reaction solution
172 g of unreacted HQ, 172 g of the target 4,4'-dihydroxydiphenyl ether, 27 g of HQ trimer and other multimers, and mesitylene (1,2) as a reaction solvent.
3,5-trimethylbenzene) was included.

(3) Charge 748g of water into the separated reaction solution, and adjust the temperature.
Both layers were vigorously stirred while maintaining the temperature at 90 ° C., and then an oil layer and an aqueous layer were separated.

The separated aqueous layer is cooled to 50 ° C with stirring and heated to 50 ° C.
Crystals precipitated from this aqueous layer were separated using a basket type centrifuge kept at ℃.

The separated crystals were dried and DHPE8 containing no HQ.
Crude consisting of 9.0%, HQ trimer and other multimers 11.0%
146 g of 4,4'-dihydroxydiphenyl ether was obtained.

Example 1 125 g of p-xylene was used for 10 g of the dried crystals of crude DHPE obtained in Reference Example 1 and heated to the reflux temperature to completely dissolve the crystals, followed by cooling to 70 ° C. and precipitation. 70 ° C crystals
Separation using a basket-type centrifuge that was kept warm gave DHPE with a purity of 96.6% with a recovery rate of 92.1%.

Example 2 When DHPE was purified in the same manner as in Example 1 except that the crystallization temperature was changed to 80 ° C., the purity was 99.2.
% DHPE was obtained with a recovery of 88.0%.

Comparative Examples 1-2 In Example 1, the crystallization temperature was 20 ° C. (Comparative Example 1) and
Same as Example 1 except 40 ° C. (Comparative Example 2)
DHPE was purified.

The results are shown in Table 1.

Examples 3 to 5 The amount of p-xylene used was 100 g (Example 3), 150 g (Example 4), and 175 g (Example 5) per 10 g of the dried crystals of crude DHPE obtained in Reference Example 1. DHPE was purified in the same manner as in Example 1 except for the above. The results are shown in Table 2.

Examples 6 to 8 With respect to 10 g of dried crystals of crude DHPE obtained in Reference Example 1, the amount of p-xylene used was 60 g (Example 6), 80 g (Example 7),
Same as Example 2 except 100 g (Example 8)
DHPE was purified. The results are shown in Table 2.

Examples 9 to 11 With respect to 10 g of dried crystals of crude DHPE obtained in Reference Example 1, the amount of p-xylene used was 60 g (Example 9), 80 g (Example 10),
As 100 g (Example 11), the crystals were completely dissolved by heating to reflux temperature and then cooled to 90 ° C.
Table 2 shows the results of separation using a basket type centrifuge kept at a temperature of ° C.

Example 12 To 10 g of the dried crystals of crude DHPE obtained in Reference Example 1, 125 g of toluene was used, and the crystals were completely dissolved by heating to the reflux temperature and then cooled to 70 ° C. Separation using a basket-type centrifuge kept at 70 ° C yielded DHPE with a purity of 98.0% with a recovery rate of 90.0%.

The results are shown in Table 3.

Example 13 DHPE was purified in the same manner as in Example 12 except that the crystallization temperature was changed to 80 ° C.

The results are shown in Table 3.

Comparative Examples 3 to 4 In Example 12, the crystallization temperature was 20 ° C. (Comparative Example 3) and
Example 12 was repeated except that the temperature was changed to 40 ° C (Comparative Example 4).
DHPE was purified.

The results are shown in Table 3.

Examples 14 to 16 In Example 12, with respect to 10 g of dried crystals of crude DHPE, the amount of toluene used was 100 g (Example 14), 150 g (Example 15),
Same as Example 12 except 175 g (Example 16)
DHPE was purified.

The results are shown in Table 4.

Examples 17 to 19 With respect to 10 g of the dried crystals of crude DHPE obtained in Reference Example 1, the amounts of toluene used were 60 g (Example 17), 80 g (Example 18) and 100 g (Example 19), respectively, and 80 ° C. Was crystallized.

The results are shown in Table 4.

Examples 20 to 21 With respect to 10 g of the dried crystals of the crude DHPE obtained in Reference Example 1, the amounts of toluene used were 30 g (Example 20) and 50 g (Example 21), respectively, and crystallization was performed at 90 ° C.

The results are shown in Table 4.

Example 22 When 10 g of dried crystals of crude DHPE obtained in Reference Example 1 were used and 125 g of chlorobenzene was used to purify DHPE in the same manner as in Example 1, DHPE having a purity of 97.0% was recovered at 92.0%.
Obtained in.

Comparative Example 5 To 10 g of the dried crystals of crude DHPE obtained in Reference Example 1, 125 g of cumene was used and heated to the reflux temperature to completely dissolve the crystals, and then the crystallization temperatures were 20 ° C. and 40 ° C. 50 ° C, 60 ° C, 70
DHPE was purified at temperatures of 80 ° C, 80 ° C, and 90 ° C.

The results are shown in Table 5.

Comparative Example 6 To 10 g of the dried crystals of crude DHPE obtained in Reference Example 1, 125 g of mesitylene was used and heated to the reflux temperature to completely dissolve the crystals, and then the crystallization temperatures were 20 ° C. and 40 ° C. 50 ℃, 60 ℃,
DHPE was purified at 70 ° C, 80 ° C, and 90 ° C.

The results are shown in Table 5.

Comparative Example 7 When the solubility of DHPE in benzene was examined, the solubility of benzene was only about 1.5 g / 100 g benzene even at the boiling point of benzene (80 ° C.). Therefore, the purity can be increased with 100 g of benzene with respect to 10 g of dried crystals of crude DHPE. could not.

From the above results, the crystallization temperature and DHPE when using each solvent
The relationship with the purity is shown in FIG.

In the figure, x indicates toluene, Δ indicates p-xylene, □ indicates cumene, and ● indicates mesitylene.

From FIG. 1, when crystallizing DHPE crude crystals, toluene or xylene was used as a crystallization solvent, and the crystallization temperature was 70%.
It can be seen that a high-purity DHPE can be obtained by setting the temperature to 90 ° C.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the crystallization temperature when DHPE crude crystals are crystallized using various crystallization solvents and the purity of DHPE obtained. × …… Toluene, △ …… p-xylene, □ …… Cumen, ● …… Mesitylene.

Claims (1)

[Claims] 1. Low-purity crude 4,4'-dihydroxydiphenyl ether crystals obtained by the reaction of hydroquinone,
A method for purifying 4,4'-dihydroxydiphenyl ether, which comprises crystallizing a halogen-substituted benzene, toluene or xylene as a crystallization solvent in a temperature range of 70 to 90 ° C.