JPH0778030B2 - Method for producing high-quality bisphenol A - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high-quality bisphenol A having high purity, excellent hue, and no coloring. Bisphenol A is a raw material for polycarbonate resins and epoxy resins, and in recent years, the demand for bisphenol A that is colorless and transparent and has high purity, which is particularly suitable for optical applications, has significantly increased.

[0002]

2. Description of the Related Art Bisphenol A [2,2]
It is known to react excess phenol with acetone in the presence of an acid catalyst to produce -bis (4-hydroxyphenyl) propane]. Further, in order to separate and recover high-purity bisphenol A from this reaction product, the reaction product was cooled to crystallize a crystal adduct of bisphenol A and phenol (hereinafter, also simply referred to as a crystal adduct). It is also known to remove phenol from adduct crystals. In such a method for producing bisphenol A, the purity of bisphenol A recovered as a product obviously depends largely on the removal rate of phenol from the crystal adduct,
It is also affected by impurities other than phenol contained in adduct crystals. A method of washing adduct crystals with liquid phenol in order to remove impurities other than phenol contained in crystal adducts is known (JP-A-1-
146839). This known method is characterized in that the phenol separated from the crystal adduct is used as the liquid phenol for washing, and thereby, the product bisphenol A having a hue better than that in the case of using the industrial phenol is obtained. In this case, the phenol is separated from the crystal adduct by evaporation, extraction, stripping with steam or the like. As a method for removing phenol from a crystal adduct by evaporation, specifically, Japanese Patent Publication No. 52-4
As disclosed in Japanese Patent No. 2790, after melting the crystal adduct, 0.1-3 at a temperature above 180 ° C. and under reduced pressure.
A method in which it is vaporized in 0 minutes and phenol is fractionally condensed to be separated from bisphenol A can be mentioned. However, as described above, the bisphenol A obtained by washing the crystal adduct with phenol and then evaporating it is
There is a problem in that the hue is still insufficient and the melt is easily colored.

In order to solve such a problem, a method of obtaining bisphenol A having an improved hue by adding oxalic acid or citric acid to a phenol / water / bisphenol A mixture and then subjecting it to a distillation treatment is proposed. (Japanese Patent Publication No. 40-19333). In addition, in order to improve the stability of bisphenol A, thioglycolic acid,
Method of adding glycolic acid or polyphosphoric acid (Japanese Patent Publication No.
7-43937), a method of adding lactic acid, malic acid or glyceric acid (JP-A-2-231444) and the like are also known. However, even with the above method, the effect of improving the hue of bisphenol A has not been sufficient.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing bisphenol A which is highly pure, has an excellent hue and is free from coloring of the melt.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a sufficient hue-improving effect is obtained in the method for improving the hue of bisphenol A by adding the additive. What is not achieved is that the trace amount of strong acid coexisting in the crystal adduct at the time of adding the additive deteriorates the hue of bisphenol A, and such strong acid is neutralized by strong alkali. Then, it was found that an excessive amount of strong alkali used for the neutralization or a strong alkali metal salt produced as a by-product deteriorates the hue of bisphenol A, and further, the additive is mixed with the crystalline adduct substantially in a neutral condition. Then 130 to 20
It was found that bisphenol A obtained by evaporating and removing phenol under reduced pressure at a temperature of 0 ° C. has an excellent hue and the hue of the melt is significantly suppressed from changing over time, and the present invention is completed. Came to. That is, according to the present invention, an aliphatic carboxylic acid is added to a crystal adduct consisting of bisphenol A and phenol under a substantially neutral condition or a melt thereof or a mixture of the crystal adduct and phenol or a melt thereof. Provided is a method for producing high-grade bisphenol, which comprises evaporating and removing phenol under reduced pressure at a temperature of 130 to 200 ° C. after mixing.

The crystal adduct of bisphenol A and phenol used in the present invention is produced by a conventionally known method. That is, excess phenol and acetone are reacted in the presence of an acid catalyst to obtain a reaction product containing bisphenol A, and the reaction product is crystallized to give a crystalline adduct of bisphenol A and phenol. Can be obtained.

In the reaction of phenol with acetone to obtain bisphenol A, hydrochloric acid as an acid catalyst,
Strongly acidic substances such as sulfuric acid and sulfonic acid type strong ion exchange resins are used. Such a strongly acidic substance not only acts as a catalyst in the reaction system of phenol and acetone, but also exhibits an action of promoting the generation of coloring substances and impurities under heating conditions. To reduce the hue and purity of. Therefore, it is proposed to remove or neutralize such a strongly acidic substance after the reaction so as not to flow out to the subsequent dephenoling step involving heating conditions. For example, in a reaction using hydrochloric acid as a catalyst, after the reaction, the product is heated to remove hydrochloric acid,
A method of neutralizing residual hydrochloric acid with an alkali to pH 5 to 6 has been proposed (Japanese Patent Publication No. 47-4393).
No. 7). Further, in the method using a strong acid type ion exchange resin, during the reaction, the organic sulfonic acid is desorbed by the decomposition of the ion exchange resin and is mixed into the product, so that the organic sulfonic acid is changed to a weakly basic ion exchange resin. A method of neutralizing using is proposed (US Pat. No. 4,19,184).
No. 3). On the other hand, the hue and purity of phenol and bisphenol A are lowered not only by the acid but also by the alkali, so it is necessary to neutralize the strongly acidic substance with the alkali not to exceed the neutralization point.

As described above, in the reaction in which phenol and acetone are reacted in the presence of a strongly acidic substance, is it necessary to neutralize the strongly acidic substance present in the reaction product after the reaction so that the neutralization point is not exceeded? , Needs to be removed from the reaction system,
Further, when the alkali used for neutralizing the strongly acidic substance remains, it is also necessary to remove this alkali. Further, the strongly acidic substance or alkali present in the reaction product can be removed by using a multi-step crystallization step in the subsequent crystallization step. The crystalline adduct under a substantially neutral condition used in the present invention means a crystalline adduct from which the influence of the strongly acidic substance or the alkaline substance is removed. Such a crystal adduct is added to and dissolved in an aqueous methanol solution whose acidity is adjusted to have a pH of 5.0, and a pH of 4.9 is obtained by a method for measuring pH under a substantially non-ionizing condition of phenol.
It shows 0 to 5.50, preferably pH 4.95 to 5.20. In this case, the pH measurement method under the substantially non-dissociation condition of phenol is as follows.
The crystal adduct sample was dissolved in a methanol solution containing 5% by weight of water adjusted to 5.0 to a concentration of 20% by weight, and
It is performed according to IS Z 8802. The pH of the crystal adduct shown in this specification is obtained by the above-mentioned measuring method. The pH of the crystal adduct described in this specification is obtained by the above-mentioned measuring method. In the present invention, as the crystal adduct, those which are under a substantially neutral condition are used as described above, but in this case, it is preferable to maintain the melt color APHA of the crystal adduct at 15 or less. A crystal adduct having a melt color APHA of 15 or less can be obtained by maintaining the crystal adduct under substantially neutral conditions as described above, but if necessary, increase the number of crystallization stages in the crystallization step. It can also be obtained by washing the crystal adduct with purified phenol.

When the crystalline adduct is subjected to a washing treatment with phenol, it is particularly effective to use a purified phenol treated by a special method. That is, the present inventors have conducted intensive studies on an industrial phenol purification method for obtaining a phenol suitable for cleaning a crystal adduct, and as a result, after contacting the industrial phenol with a strong acid type ion exchange resin, a distillation treatment is carried out. The purified phenol thus obtained does not contain the coloring-causing substance of the product bisphenol A. The product bisphenol A obtained by washing the crystal adduct with the purified phenol and removing the phenol from the washed crystal adduct has a hue It was found to be extremely excellent. As the industrial phenol, a commercially available product may be used, and generally, phenol having a purity of 99.5% by weight or more, preferably 99.93% by weight or more may be used.

The method for obtaining purified phenol suitable for washing the crystal adduct will be described in detail. First, industrial phenol is treated by contacting it with a strong acid ion exchange resin. As the strong acid type ion exchange resin, one having a sulfone group is used, and such a strong acid type ion exchange resin is conventionally well known. For example, gel-type ones such as Amberlite and Amberlyst available from Rohm and Haas, and Diaion etc. available from Mitsubishi Kasei can be preferably used. The treatment of phenol with this strong acid ion exchange resin is carried out by a method of circulating phenol in a packed column containing a strong acid ion exchange resin, a method of putting phenol in a stirring tank containing a strong acid ion exchange resin, and stirring it. It can be carried out. The treatment temperature is 45 to 150 ° C, preferably 50 to
It is 80 ° C. The contact time between the strong acid ion exchange resin and phenol is 5 to 200 minutes, preferably 15 to 60 minutes. When the phenol is treated using this strong acid type ion exchange resin, the water content in the phenol is 0.5% by weight or less, preferably 0.1% by weight or less. If the water content is larger than this, the effect of removing impurities by the strong acid ion exchange resin deteriorates. 0.5% by weight from phenol
The removal of water up to the following can be performed by adding a known azeotroping agent to phenol and azeotropically distilling it.

Phenol which has been subjected to the contact treatment with the strong acid type ion exchange resin contains high boiling point impurities, and the high boiling point impurities are separated as a distillation residue by distillation treatment. The operating conditions of the distillation column should be such that phenol and high-boiling impurities can be separated, but it is necessary to do so under conditions that high-boiling impurities are not mixed in the distillate phenol. Is. The operating pressure is arbitrarily set at a temperature of 185 ° C. or lower, but it is usually performed under a reduced pressure of 50 Torr to 600 Torr. If the operating temperature exceeds 185 ° C, decomposition of high-boiling impurities and the like will occur and the quality of the purified phenol will deteriorate, which is not preferable. The purified phenol obtained by the above treatment has an APHA standard hue of 10 or less, and even if it adheres to the product bisphenol, the hue is not particularly deteriorated.

The cleaning of the crystal adduct with the purified phenol may be any method which can sufficiently bring the contact between the crystal adduct and the purified phenol. This washing treatment is carried out, for example, by removing the mother liquor from the crystal adduct in a solid-liquid separator such as a filter or a centrifuge for separating the crystal adduct, and then introducing purified phenol into the solid-liquid separator. It is also possible to wash the crystal adduct to which a small amount of mother liquor discharged from the solid-liquid separator adheres in a separate stirring tank with purified phenol. The ratio of the purified phenol to the crystal adduct is 10
The amount is 30 to 1000 parts by weight, preferably 100 to 300 parts by weight, relative to 0 parts by weight. The purified phenol after being used for washing the crystal adduct is used as it is or after being used for washing the crude crystal adduct obtained in the crystallization step in the preceding stage, and then is circulated as a raw material phenol in the synthesis reaction step of bisphenol A.

To carry out the present invention in a preferred manner, the crystalline adduct or its melt or the mixture of its crystalline adduct and phenol or its melt under substantially neutral conditions in the presence of an aliphatic carboxylic acid. Melt and heat under reduced pressure to remove phenol by evaporation. The aliphatic carboxylic acid used in the present invention has an action of preventing the coloring of bisphenol A when the bisphenol A in a molten state is brought into contact with air for a long time or is kept at a high temperature. In the present invention, an aliphatic carboxylic acid is added to a crystalline adduct under a substantially neutral condition, and the phenol in the crystalline adduct is removed by evaporation to obtain bisphenol A having excellent hue and no coloring. be able to. Bisphenol A as the aliphatic carboxylic acid
Any material may be used as long as it has an anti-coloring effect, and conventionally known materials can be used. Examples of such substances include formic acid, oxalic acid, citric acid, tartaric acid, glycolic acid, lactic acid, malic acid and glyceric acid. These are 16 during the reaction.
It decomposes or isomerizes at a temperature of 0 ° C. or higher, and exhibits an excellent action as a coloring inhibitor for bisphenol A. In the present invention, it is necessary to use an aliphatic carboxylic acid as an anti-coloring agent, and even if an oxalic acid ester, ammonium sulphate, terephthalic acid, sodium hydrogen phosphate or the like is used, sufficient bisphenol A anti-coloring No effect is obtained, and in this case, when bisphenol A is kept in contact with air for a long time or kept at high temperature, bisphenol A is colored and its hue is significantly deteriorated. The addition amount of the aliphatic carboxylic acid is 1 to the crystal adduct.
It is 100 ppm by weight, preferably 5 to 50 ppm by weight. Further, in the present invention, when a crystal adduct or a mixture containing the same is heated and melted in the presence of oxalic acid or citric acid, the melting temperature is 115 to 180 ° C, preferably 120 to 150 ° C, and the melting pressure is 1-5 atm,
It is preferably 1.0 to 1.9 atm. The melting atmosphere is preferably an atmosphere having an oxygen concentration as low as possible, and usually has an oxygen concentration of 0.005 vol% or less, preferably 0.
It is advantageous to use an atmosphere of 001 vol% or less. Further, in the present invention, in order to melt the crystal adduct or the mixture containing the crystal adduct in a short time, the crystal adduct or the mixture containing the crystal adduct is used with almost no coloring phenol such as purified phenol as described above. It is also possible to employ a method of diluting and melting it and a method of dissolving it in a melted liquid of the crystal adduct or a mixture containing the crystal adduct.

In the present invention, the heat-melted material obtained as described above is subjected to evaporation treatment. In this case, the evaporation treatment is
It is carried out at 130 to 200 ° C. under reduced pressure. A preferred evaporation treatment is carried out such that the temperature of the entire melt is 185 ° C. or lower and at least part of the melt is heated to a temperature of 160 ° C. or higher. If the temperature of the evaporation treatment is too low, the effect of the aliphatic carboxylic acid added as a coloring preventing agent will not be sufficiently exerted, while if it is too high, color decomposition of the aliphatic carboxylic acid will occur. This evaporation treatment is carried out under reduced pressure and the pressure is 100 torr or less, preferably 5 to 40 torr. Further, the atmosphere for the evaporation treatment is preferably an atmosphere having the lowest oxygen concentration, and usually the oxygen concentration is 0.005 vo% or less, preferably 0.0
The use of an atmosphere of 01 vol% or less is advantageous.

[0015]

According to the present invention, it is possible to obtain a product bisphenol A which has a high purity, an excellent hue, and is prevented from being colored during melting. In addition, this product also has excellent storage stability.

[0016]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 Bisphenol A having a melt color of 50 APHA obtained by reacting phenol with acetone in the presence of an acid catalyst,
Crystallizing the mixture of phenol and impurities in two stages,
A crystal adduct was deposited. The slurry solution was filtered under reduced pressure to obtain a solid crystal adduct, and the purified phenol obtained by the method described below was washed at a ratio of 2.5 parts by weight to 1 part by weight of the adduct. The crystalline adduct thus obtained (hue: by the multi-step crystallization described above) is one in which the strongly acidic substance has been removed, and which is under substantially neutral conditions. To this crystal adduct, 20 ppm by weight of the additive shown in Table 1 was added, and the mixture was melted under the conditions of temperature: 150 ° C., oxygen concentration in atmosphere: 0.0010 vol%, and the obtained melt was then heated at a temperature of 175 ° C. , Pressure: 10 torr, and oxygen concentration in the atmosphere: 0.0010 vol% were subjected to an evaporation treatment to substantially completely remove phenol to obtain bisphenol A. In this case, the free phenol content was 30 wtppm or less. Next, this bisphenol A was subjected to a thermal stability test (test A) in which it was heated and maintained at 175 ° C. for 0 hours or 2 hours in an air atmosphere and an accelerated thermal stability test (test in which air was blown at 175 ° C. for 2.0 hours). B), and the hue at that time was evaluated. The results are shown in Table 1. In addition, the experiment No. 6 to 12 show comparative examples.

[0018]

[Table 1]

The purified phenol used above had a melting color of 6APHA, and was used for commercial industrial phenol (water concentration: 0.1 wt%, impurity concentration: 0.05 wt%).
Manufactured by Rohm and Haas Company, Amberlite IR-11
Contact treatment was performed using 8H + resin at a temperature of 80 ° C. and an adhesion time of 50 minutes, the distillation column bottom temperature was 175 ° C. and the column top pressure was 560 torr
It was obtained by distillation at r.

Comparative Example 1 In Example 1, separately prepared melt colors APHA5-1
The experiment was performed in the same manner except that a crystal adduct containing a strongly acidic substance having a pH of 4.85 and not under neutral conditions was used. The hue of bisphenol A obtained in this case was as follows. The free phenol content in bisphenol A was 50 wtppm.

[0021]

[Table 2]

Comparative Example 2 Bisphenol A was obtained in the same manner as in Example 1 except that the bottom temperature of the distillation column was 200 ° C. when the purified phenol was distilled, but this was obtained after Test A at 175 ° C. to 0 hr. The melt color of APHA30 was shown.

Front page continuation (72) Inventor Hiroaki Nishijima 2-12-1, Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa Chiyoda Kakoh Construction Co., Ltd. (56) Reference JP-A-55-151526 (JP, A) JP-A 1-146839 (JP, A) JP47-43937 (JP, B1) JP40-19333 (JP, B1)

Claims (3)

[Claims] 1. An aliphatic carboxylic acid is added and mixed to a crystalline adduct consisting of bisphenol A and phenol under a substantially neutral condition or a melt thereof or a mixture of the crystalline adduct and phenol or a melt thereof. A method for producing high-grade bisphenol, which comprises removing phenol by evaporation under reduced pressure at a temperature of 130 to 200 ° C. 2. The method according to claim 1, wherein the aliphatic carboxylic acid is at least one selected from formic acid, glycolic acid, oxalic acid, citric acid, lactic acid, malic acid, glyceric acid and tartaric acid. 3. The method according to claim 1 or 2, wherein the crystal adduct is one that has been redissolved and recrystallized in phenol at least once and then washed with purified phenol.