JPH0441451A - Method for purifying aromatic bisphenols - Google Patents

Abstract

PURPOSE:To obtain the subject colorless or scarcely colored compound by mixing and dissolving colored subject compound in an aliphatic ketone, separating insoluble components from the solution and recrystallizing the subject compound using a mixed solvent comprising a lower aliphatic alcohol and an aromatic hydrocarbon. CONSTITUTION:A colored bisphenol such as 9,9,9'-bis(4-hydroxyphenyl)-fluorene is mixed and dissolved in an aliphatic ketone such as acetone, methyl ethyl ketone and diisopropyl ketone and the insoluble components are separated and removed. The obtained bisphenol is recrystallized with a mixed solvent comprising a lower aliphatic alcohol (e.g. methanol, ethanol and propanol) and an aromatic hydrocarbon (e.g. toluene, xylene and ethylbenzene) to purify the colored compound in high efficiency and obtain a colorless or scarcely colored aromatic bisphenol usable even as a raw material for polyesters, epoxy resins, etc., for optical use.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for purifying aromatic bisphenols.

Bisphenols such as 9.9'-bis(4-hydroxyphenyl)fluorene are useful as raw materials for producing polyesters, epoxy resins, and the like.

Conventional technology Aromatic bisphenols are obtained by reacting aromatic ketones such as fluorenone, 1-indanone, 2-tetralone, and benzophenone with phenols such as phenol and cresol in the presence of a catalyst such as hydrochloric acid ( (Japanese Patent Application Laid-Open No. 62-230741).

Although crystals of aromatic bisphenols, which are originally colorless, do not appear to be colored on the surface, they are often found to be colored when dissolved in a solvent and the hue is measured.

The cause of this coloring is not only that impurities are mixed in during the manufacturing process, but also that phenols themselves are easily oxidized, and coloration occurs due to air oxidation during storage.

Aromatic bisphenols colored in this way cannot be sufficiently decolorized using activated carbon, etc., which are commonly used for purification. If colored aromatic bisphenols are used as raw materials to produce optical polyesters, epoxy resins for IC sealants, etc., the products will be colored and cannot be used. For supplies used in such applications, it is necessary that the Hazen color number be 50 or less.

Problem to be Solved by the Invention The present invention solves the problem of aromatic bisphenols containing coloring components.
The purpose is to efficiently remove these and obtain highly pure aromatic bisphenols with no (or little) coloring.

Means for Solving the Problems The present inventors conducted research to solve the above problems, and created a solution obtained by mixing colored bisphenols with aliphatic ketones, dissolving them, and separating the undissolved components. We have completed the present invention by discovering that colored components can be significantly reduced by recrystallizing bisphenols using a mixed solvent of lower aliphatic alcohol and aromatic hydrocarbon.

Aromatic bisphenols are room temperature white or colorless crystalline compounds having a structure in which two phenolic compounds are bonded to an aromatic compound, but are preferably compounds obtained by reacting aromatic ketones with phenols, More preferred is 9,9'-bis(4-hydroxyphenyl)fluorene or an alkyl substituted product thereof. Below, 9.9'-
The present invention will be explained using bis(4-hydroxyphenyl)fluorene as a representative example.

9.9'-Bis(4-hydroxyphenyl)fluorene can be produced by, for example, reacting fluorenone and phenol in the presence of β-mercaptopropionic acid and hydrochloric acid, and then
Excess phenol is expelled, diethyl ether is added to form and separate a 9,9'-bis(4-hydroxyphenyl)fluorene complex, which is then recrystallized from toluene, which is then dissolved in methyl ethyl ketone. When measuring the hue, the Hazen color number is 5.
00 or more. Furthermore, even if this product is recrystallized with toluene or methyl ethyl ketone, the hue hardly decreases.

However, if a mixed solvent of aliphatic alcohol and aromatic hydrocarbon is used as the recrystallization solvent, the colored components can be removed. However, in this case, it has been found that if ketone insoluble substances are contained in the colored aromatic bisphenols, the purified product is rapidly oxidized and colored. Therefore, in such a case, it is necessary to remove this in advance and then recrystallize it. According to the research conducted by the present inventors, this ketone insoluble material was found to be a metal compound such as iron or nickel, which was thought to promote the oxidation of phenols. It is thought that these metal compounds may be mixed in from the reaction container or the like.

As the ketone used to remove the ketone insoluble matter, lower aliphatic ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, diethyl ketone, dipropyl ketone, dibutyl ketone, etc. are used.

Preferred are acetone, methyl ethyl ketone, and diisopropyl ketone. In solvents other than lower aliphatic ketones, for example, alcohol solvents such as methanol and isopropanol, and hydrocarbon solvents such as benzene and toluene, such metals or metal compounds are separated as insoluble substances. It is not possible. The amount of lower aliphatic ketone used may be at least the amount necessary to dissolve aromatic bisphenols, but even if it is slightly insufficient, there is no problem in terms of purification, so dissolution can be performed and filtration can be performed after dissolution. If so, it is best to keep it as small as possible. Normally,
It is preferable to use 0.5 to 30 parts by weight, preferably 1 to 10 parts by weight, per 1 part by weight of the aromatic phenol. Although the dissolution may be carried out at room temperature, it is preferable to heat it to near the boiling point of the lower aliphatic ketone. After dissolution is completed, undissolved substances are separated by filtration, centrifugation, etc.

Since the liquid after separating the insoluble matter is a lower aliphatic ketone solution of aromatic bisphenols, the lower aliphatic ketone is removed, but it is not necessary to completely remove the lower aliphatic ketone. Note that lower aliphatic ketones can be easily separated by distillation and can be reused.

The aromatic bisphenols from which the ketone insoluble matter has been separated are recrystallized using a mixed solvent of aliphatic alcohol and aromatic hydrocarbon. As the aliphatic alcohol, lower aliphatic alcohols such as methanol, ethanol, propatool, butanol can be used, and preferably methanol, ethanol, n-proptoolzene, l
5O-Flobanol. Further, as the aromatic hydrocarbon, lower aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene can be used, and preferably toluene, xylene, and ethylbenzene are used. Note that it is advantageous that the lower alcohol and the lower aromatic hydrocarbon have a lower boiling point.

The aliphatic alcohol and aromatic hydrocarbon may be mixed in advance, but if the aromatic bisphenols are first dissolved in the aliphatic alcohol by heating and then the aromatic hydrocarbon is added, the solubility will be improved. Excellent. The amount of these solvents to be used is 0.2 to 10 parts by weight of aliphatic alcohol, preferably 1 to 5 parts by weight, and 1 to 10 parts by weight of aromatic hydrocarbon per 1 part by weight of aromatic bisphenol. . here,
Aliphatic alcohol increases the solubility of aromatic bisphenols in a mixed solvent, but if it is too large, precipitation of crystals will be inhibited upon cooling, resulting in a decrease in recovery rate.

Although the aromatic bisphenols may be dissolved at room temperature, it is preferably carried out by heating to 50 to 60°C. Thereafter, it is cooled to precipitate crystals, but at this time, if a large amount of aliphatic alcohol is present, crystal precipitation will be inhibited and the recovery rate will decrease as mentioned above, so it is desirable to distill off excess aliphatic alcohol. . When the aliphatic alcohol is present in an amount of 5 times or more by weight relative to the aromatic bisphenols, it is preferable to distill off the aliphatic alcohol so that the amount is about 0.5 to 5 times the weight of the aromatic bisphenols. For this reason, an aliphatic alcohol with a lower boiling point than aromatic hydrocarbons is used, and once the aromatic bisphenols have completely dissolved, the aliphatic alcohol starts to be expelled, and as it initially undergoes azeotropy, the temperature is lower than that of the aromatic hydrocarbons. Distillation starts at this point, but it is preferable to continue distilling until the temperature reaches near the boiling point of the aromatic hydrocarbon.

Precipitation of crystals is preferably carried out by gradually lowering the temperature to -5°C or lower.

Next, the precipitated crystals are separated by filtration or centrifugation, and the crystals are washed and dried to obtain purified aromatic bisphenols.

A lower aromatic hydrocarbon is suitable as a washing solvent, and drying under reduced pressure at 130° C. or lower is suitable. These series of operations are preferably performed under an atmosphere of an inert gas such as nitrogen in order to prevent oxidation.

Examples Example 1 9,9'-bis(4-hydroxyphenyl)fluorene obtained by reacting fluorenone and phenol in a four-bottle flask equipped with a stirrer, thermometer, nitrogen introduction tube, and ball condenser. Add 1 part by weight (Hazen color number 500 or more, iron ions 120 ppm, nickel ions 72 ppm), add 2.5 parts by weight of methyl ethyl ketone,
Stir at 50°C to dissolve. Thereafter, it was cooled to room temperature and filtered under reduced pressure using a filter paper provided with a layer of perlite.

When this filtrate was analyzed by atomic absorption spectroscopy, iron ions were found to be 5 ppm.
, 0.4 ppm of nickel ions. This filtrate is
The mixture was placed in a cold flask, and most of the methyl ethyl ketone was expelled to precipitate crystals, after which 2 parts by weight of methanol was added, heated to 50°C, stirred, and dissolved again. Next, 5 parts by weight of toluene was added and stirring was continued to form a homogeneous solution, and then the temperature was gradually lowered to -5°C to precipitate crystals.

Next, this was suction-filtered using a Nutsche filter lined with filter paper, the crystals were washed with toluene, and heated at 130°C in a vacuum dryer.
After drying for 10 hours, purified 9.9'bis(4-hydroxyphenyl)fluorene was obtained. Yield 85.6% by weight, GC
Purity 99.9%.

This 9,9'-bis(4-hydroxyphenyl)fluorene was dissolved in twice the amount of methyl ethyl ketone, and the hue was measured with a Hazen colorimeter, and the color number was 30.

Example 2 Except for using 2-propatool instead of methanol in Example 1,
When the same purification process was performed, the yield was 89% by weight, and GC
A purity of 100% and a Hazen color number of 20 were obtained.

Effects of the Invention According to the purification method of the present invention, colored aromatic bisanilines can be efficiently purified to produce aromatic bisanilines with no or little coloration, which can be used even as raw materials for resins used in optical applications. can be obtained.

Claims (1)

[Claims] (1) Recrystallizing the bisphenols obtained by mixing and dissolving aliphatic ketones in colored bisphenols and separating the insoluble components using a mixed solvent of lower aliphatic alcohol and aromatic hydrocarbon. A method for purifying aromatic bisphenols, characterized by: