JP2022066806A - Production method of 1,4-dihydroxybenzene dimer - Google Patents

Abstract

To provide a production method in which a tar component being a cause of coloration is efficiently removed, and 4,4'-dihydroxydiphenyl ether being a target substance can be obtained at high yield.SOLUTION: A production method of 4,4'-dihydroxydiphenyl ether includes a process of adding a crude product containing 1,4-dihydroxybenzene, 4,4'-dihydroxydiphenyl ether being a dimer of 1,4-dihydroxybenzene, and a tar component of trimer and tetramer or more to mixed solvent of water and one or several kinds of organic solvent selected from the group consisting of methanol, acetone, isopropanol, butanol and methyl ethyl ketone to sediment the tar component.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a 1,4-dihydroxybenzene dimer with a high degree of purification.

The following formula (1):

で示される4,4'-ジヒドロキシジフェニルエーテル（DHDE）は、エポキシ樹脂、ポリカーボネート、ポリイミドなどの原料として、液晶材料としても非常に有用な化合物である。DHDEは、下式（２）：

The 4,4'-dihydroxydiphenyl ether (DHDE) represented by (1) is a very useful compound as a raw material for epoxy resins, polycarbonates, polyimides and the like, and also as a liquid crystal material. DHDE is the following formula (2):

で示される1,4-ジヒドロキシベンゼン（DHB；「ハイドロキノン（HQ）」とも呼称される。）を高温で脱水することによって得られる二量体である（例えば、特許文献１、２）。

It is a dimer obtained by dehydrating 1,4-dihydroxybenzene (DHB; also referred to as "hydroquinone (HQ)") represented by (for example, Patent Documents 1 and 2).

The crude product of DHDE obtained by the conventional production method contains unreacted DHB, a trimer of DHB, and a tar content in addition to the target substance DHDE.
DHB is water soluble and trimers and tars are oil soluble. On the other hand, the target substance, DHDE, has an intermediate dissolution property between water-soluble and oil-soluble. Therefore, when purifying DHDE, first, water is added to the crude product to remove DHB, then the trimer is removed from the precipitate with an organic solvent (toluene, xylene, etc.), and then activated carbon or the like is used. The tar content is removed using an adsorbent to obtain the desired dimer.
The purity of DHDE in the obtained purified product is 95 to 98%, but it is colored brown because tar content remains. Colored DHDE is particularly unsuitable as a liquid crystal material, and purification with an adsorbent must be repeated multiple times in order to keep it below the allowable coloring value, and the final DHDE yield is 10% or less. It will be quite low.

Japanese Patent Application Laid-Open No. 62-67040 Special Publication No. 60-043052

The present inventors have made it an object to provide a production method capable of efficiently removing the tar component that causes coloring and obtaining DHDE as a target substance in a high yield.

The target substance, DHDE, can be produced, for example, by the method disclosed in Patent Document 1 or 2. The present invention uses the crude product of DHDE thus obtained as a mixed solvent of water and one or several organic solvents selected from the group consisting of methanol, acetone, isopropanol, butanol and methyl ethyl ketone. Addition to precipitate tar and purify 4,4'-dihydroxydiphenyl ether.

According to the method of the present invention, tar content can be highly removed from the crude product of 4,4'-dihydroxydiphenyl ether by a single precipitation operation, so that 4,4'-dihydroxydiphenyl ether having a good hue can be obtained. Can be obtained.

The graph which shows the comparison of the DHDE content in the purified product in each purification step.

[Manufacturing process of 4,4'-dihydroxydiphenyl ether (DHDE)]
<Reaction process>
Using the following conventional method, the following equation (2):

で示される1,4-ジヒドロキシベンゼン（DHB）を高温で脱水して、下式（１）：

1,4-Dihydroxybenzene (DHB) represented by is dehydrated at a high temperature, and the following formula (1):

で示される、DHBの二量体4,4'-ジヒドロキシジフェニルエーテル（DHDE）を含む粗生成物を得る。このような粗生成物は、目的物質であるDHDE以外に、未反応のDHB、DHBの三量体、タール分を含有する。

Obtains a crude product containing 4,4'-dihydroxydiphenyl ether (DHDE), a dimer of DHB, as shown in. Such a crude product contains unreacted DHB, a trimer of DHB, and a tar content in addition to the target substance DHDE.

<Refining process>
Conventional purification methods add crude DHDE products to water to dissolve water-soluble DHB and precipitate other components. Next, the precipitate is added to water or an organic solvent (methanol, acetone, isopropanol, butanol, methyl ethyl ketone, etc.) or a mixed solvent thereof, and further adsorbed and purified with activated carbon. However, the DHDE obtained by this purification method is colored brown with residual tar.
On the other hand, the method for purifying DHDE according to the present invention is not focused on improving the recovery rate of DHDE, but is configured by a policy of maximizing the amount of tar removed by sedimentation separation. As a result, this policy constitutes a policy of maximizing the removal of residual tar for decolorization of purified DHDE and, as a result, reducing the decolorization operation of coloring due to tar.
Surprisingly, in the proper proportions of organic solvents that are considered good solvents for DHDE, for example, one or several organic solvents selected from the group consisting of methanol, acetone, isopropanol, butanol and methyl ethyl ketone, and water. By using the mixed solvent contained in it, purified DHDE without coloring due to tar content could be obtained in high yield. In the present invention, the mass ratio of the organic solvent added to the mass of water is 0.1 to 50 w / w%, preferably 10 to 25 w / w%.

More specifically, the method for producing DHDE according to the present invention comprises DHB, a DHB dimer (DHDE), a DHB trimer, a crude product containing a tar content, water, methanol, acetone, isopropanol, butanol. And is added to a mixed solvent with one or several organic solvents selected from the group consisting of methyl ethyl ketone and heated to 85-90 ° C. to dissolve, and then in the heat-dissolved state, the trimer of DHB and It is characterized by including a step of precipitating a tar component. More preferred organic solvents are methanol, acetone and isopropanol, most preferably methanol.
The supernatant obtained in the above tar precipitation step contains unreacted DHB in addition to the target substance DHDE. The supernatant is then cooled to 5-10 ° C. to give the purified DHDE as a precipitate.

According to the present invention, a method for producing 4,4'-dihydroxydiphenyl ether (DHDE) from 1,4-dihydroxybenzene (DHB) is described.
Reaction process to dimerize DHB to obtain crude DHDE;
Purification step 1 to remove colored components (tar) and impurities (unreacted raw materials) from crude DHDE by tar separation and crystallization; and impurities not removed by crystallization in the aqueous solution system of purification step 1 are organic solvent-based. Purification step 2 to remove by crystallization in
including.

Survey 1
[Comparative manufacturing example]
By the conventional method, the following formula (1):

で示される4,4'-ジヒドロキシジフェニルエーテル（DHDE）を含む粗生成物を得た。

A crude product containing 4,4'-dihydroxydiphenyl ether (DHDE) indicated by.

<Reaction process>
1200 kg (10.9 kmol) of 1,4-dihydroxybenzene (DHB) and 30 kg (1.16 kmol) of p-toluenesulfonic acid monohydrate were suspended in 1,2,4-trimethylbenzene 913L. The hydroquinone dimerization reaction was carried out while removing the water produced by the reaction by azeotropic boiling. After completion of the reaction, the mixture was neutralized with a 5% aqueous sodium carbonate solution, diluted with 1668 L of water, and then the organic layer was removed. After adsorption and purification with activated carbon, the aqueous layer was gradually cooled to precipitate crystals. The precipitate was filtered and the separated precipitate was washed with 800 L of water. The same washing operation was repeated twice to obtain wet crystals of crude DHDE. The hue of the crude DHDE wet crystals was brown to black.
The purity of the crude DHDE wet crystals was HQ: 1.6%, DHDE: 94.3%, and trimer: 3.8% (GCarea%).

<Purification process 1>
Next, 597 kg of crude DHDE wet crystals, 2200 kg of water and 814 kg of methanol were charged and dissolved by heating at 85 ° C. After adsorption and purification with activated carbon, it was gradually cooled to precipitate crystals. After filtering the precipitate, the separated precipitate was washed with 300 L of water to obtain wet crystals of DHDE. The hue of the wet crystals of DHDE without removing the tar component was brown.
The purity of the obtained DHDE wet crystals was HQ: 0.8%, DHDE: 96.5%, and trimer: 2.5% (GCarea%).

<Purification process 2>
416 kg of DHDE wet crystals obtained in the purification step 1 was heated and dissolved in a mixed solvent of IPA / xylene, and then gradually cooled to precipitate crystals. After filtering the precipitate, the separated precipitate was washed with 114L of xylene. The precipitate was dried under reduced pressure to obtain 114 kg of purified DHDE.
The hue of the purified DHDE obtained in the purification step 2 was brown.
The purity of the purified DHDE without removing tar was HQ: 0.5%, DHDE: 98.4%, and trimer: 1.0% (GCarea%).

[Manufacturing Example 1]
<Reaction process>
As in the comparative production example, crude DHDE wet crystals containing 4,4'-dihydroxydiphenyl ether (DHDE) were obtained by the conventional method.

<Purification process 1>
Next, 505 kg of crude DHDE wet crystals, 2200 kg of water and 220 kg of methanol were charged and dissolved by heating at 85 ° C., and then the solution was allowed to stand to settle the tar content. The settled tar content was 100 kg. After adding 751 L of methanol to the solution after removing the tar, the mixture was adsorbed and purified with activated carbon, and then gradually cooled to precipitate crystals. After filtering the precipitate, the separated precipitate was washed with 300 L of water to obtain wet crystals of DHDE. The hue of the wet crystals of DHDE from which the tar component was removed was reddish white.
The purity of the DHDE wet crystals after tar removal was HQ: 0.2%, DHDE: 98.3%, and trimer: 1.5% (GCarea%).

<Purification process 2>
259 kg of DHDE wet crystals obtained in the purification step 1 was heated and dissolved in a mixed solvent of IPA / xylene, and then gradually cooled to precipitate crystals. After filtering the precipitate, the separated precipitate was washed with 114 L of xylene. The precipitate was dried under reduced pressure to obtain 119 kg of purified DHDE.
The hue of the purified DHDE obtained in the purification step 2 was white.
The purity of the purified DHDE was HQ: ND, DHDE: 99.9%, trimer: 0.1% (GCarea%).

[Manufacturing Example 2]
<Reaction process>
As in the comparative production example, crude DHDE wet crystals containing 4,4'-dihydroxydiphenyl ether (DHDE) were obtained by the conventional method.

<Purification process 1>
554 kg of crude DHDE wet crystals, 2200 kg of water and 550 kg of methanol were charged and dissolved by heating at 75 ° C., and then the solution was allowed to stand to settle the tar content. The settled tar content was 27 kg. After adding 334 L of methanol to the solution after removing tar, activated carbon was charged and adsorbed and purified, and then gradually cooled to precipitate crystals. After filtering the precipitate, the separated precipitate was washed with 300 L of water to obtain wet crystals of DHDE.
The hue of the wet crystals of DHDE from which the tar component was not sufficiently removed was brown.
The purity of the DHDE wet crystals without tar removal was HQ: 0.4%, DHDE: 96.0%, and trimer: 3.5% (GCarea%).

<Purification process 2>
265 kg of DHDE wet crystals obtained in the purification step 1 was heated and dissolved in a mixed solvent of IPA / xylene, and then gradually cooled to precipitate crystals. After filtering the precipitate, the separated precipitate was washed with 114L of xylene. The precipitate was dried under reduced pressure to obtain 119 kg of purified DHDE.
The hue of the purified DHDE obtained in the purification step 2 was brown.
The purity of purified DHDE with insufficient tar removal was HQ: 0.4%, DHDE: 98.5%, and trimer: 1.0% (GCarea%).

Table 1 summarizes the unreacted DHB in the crystal mixture obtained in each step, the content of the target dimer DHDE, the trimer, and other components including tar, and the hue of the crystal mixture. In addition, a graph comparing the DHDE content in the crystal mixture obtained in each step is shown in FIG.

In the comparative production example using water / MeOH (MeOH 37 w / w%) as the solvent in the purification step 1, the tar content could not be sufficiently removed, and even after the purification step 2, the final purified product was colored brown, which was the purpose. The purity of DHDE of the substance was also 98.4%.
In Production Example 1 using water / MeOH (MeOH 10 w / w%) as a solvent in the purification step 1, the tar content can be removed, and the final purified product after the purification step 2 is white and the target substance is DHDE. The purity of the product was improved to 99.9%.
In Production Example 2 using water / MeOH (MeOH 25 w / w%) as a solvent in the purification step 1, the tar content could not be sufficiently removed again, and even after the purification step 2, the final purified product was colored brown. The purity of DHDE as the target substance was also 98.5%.
From the above results, it was found that when a mixed solvent obtained by adding about 10 w / w% of MeOH to water as a solvent was used in the purification step 1, DHDE crystals having a good hue could be obtained in a high yield.

Survey 2
In Investigation 1, it was confirmed that there is an appropriate ratio of water and methanol for the mixed solvent of water / methanol that produces white DHDE crystals in high yield. Further investigation was conducted to determine the range of appropriate ratios.
4.4 g, 6.6 g, 8.8 g and 11 g of methanol were mixed with 44 g of water to prepare a water / methanol mixed solvent having a methanol ratio of 10 to 25 w / w%.
Crystals of DHDE were obtained in the same manner as in Example 1 using the mixed solvent of each ratio.
The hue of the obtained crystals was visually confirmed, and the yield was calculated. Table 2 shows the results of preparing a 10% methanol solution of each crystal and confirming the solution color in order to eliminate the influence of the color difference due to the crystal size.

When the methanol ratio was 10 to 15 w / w%, a large amount of tar was precipitated, the hue of the crystals was white to pale yellow, and the solution color was good.

Survey 3
In the purification step 1, an organic solvent species that can be mixed with water and used was examined. In this study, the ratio of all organic solvent species to water was 10 w / w%. Table 3 summarizes the results of the same study as in Survey 2.

All of the organic solvents used in this study (methanol, acetone, isopropanol, butanol or methyl ethyl ketone) produced white DHDE crystals. The yields of butanol and methyl ethyl ketone were low.
As can be seen from Table 3, in particular, methanol was found to give good solution color, i.e. produce DHDE crystals with good hue in high yield.

[Solution color]
In the above survey, the criteria for determining the solution color are specified below.
◯: When the color of the 10% MeOH solution of the target crystal is colorless to pale yellow.
Δ: When the color of the 10% MeOH solution of the target crystal is yellow to light brown.
X: When the color of the 10% MeOH solution of the target crystal is brown to dark brown.

According to the production method of the present invention, 4,4'-dihydroxydiphenyl ether (DHDE), which is a very useful compound as a liquid crystal material as a raw material for epoxy resins, polycarbonates, polyimides, etc., is produced in a high yield and has an excellent hue. Can be obtained at.

Claims (2)

Equation (2):

The crude product containing 1,4-dihydroxybenzene, 1,4-dihydroxybenzene dimer, trimer and tetramer or more tar content indicated by water, and methanol, acetone, isopropanol, butanol. And the following formula (1) comprising the step of precipitating the trimer of 1,4-dihydroxybenzene and the tar content by adding to a mixed solvent with one or several organic solvents selected from the group consisting of methyl ethyl ketone. ):

A method for producing 4,4'-dihydroxydiphenyl ether, which is indicated by. The production method according to claim 1, wherein the organic solvent is methanol, and the ratio of methanol to water in the mixed solvent is 10 to 25 w / w%.

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