JP3173733B2 - Method for producing high-grade 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-grade bisphenol A having high purity, excellent hue and no coloring. Bisphenol A is a raw material for polycarbonate resins and epoxy resins. In recent years, the demand for colorless, transparent and high-purity bisphenol A particularly suitable for optical applications has been remarkably increased.

[0002]

BACKGROUND OF THE INVENTION Bisphenol A [2.2
-Bis (4-hydroxyphenyl) propane] is known to react excess phenol with acetone in the presence of an acid catalyst. Further, in order to separate and recover high-purity bisphenol A from the 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 its crystalline adduct,
It is also affected by impurities other than phenol contained in the adduct crystals. In order to remove impurities other than phenol contained in the crystal adduct, a method of washing the adduct crystal with liquid phenol is known (Japanese Patent Laid-Open Publication No. Hei 1-1990).
No. 146839). This known method is characterized in that phenol separated from a crystalline adduct is used as a liquid phenol for washing, thereby obtaining a product bisphenol A having a better hue than using industrial phenol. In this case, the phenol is separated from the crystalline 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. Sho 52-4
As disclosed in JP 2790, the crystalline adduct is melted at a temperature above 180 ° C. and under reduced pressure for 0.1 to 30 minutes.
For example, a method in which phenol is separated from bisphenol A by separating and condensing phenol. However, as described above, bisphenol A obtained by washing the crystal adduct with phenol and then evaporating it is as follows:
There is still a problem that the color is still insufficient in terms of hue and the melt is easily colored.

In order to solve such a problem, there has been proposed 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 subjecting the mixture to distillation treatment. (Japanese Patent Publication No. 40-19333). In order to improve the stability of bisphenol A, thioglycolic acid,
Method of adding glycolic acid or polyphosphoric acid (Japanese Patent Publication No. Sho 4
No. 7-43937), a method of adding lactic acid, malic acid or glyceric acid (Japanese Patent Application Laid-Open No. 2-231444), and the like. However, even in the above method, the effect of improving the hue of bisphenol A has not been sufficient.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing bisphenol A which is high in purity, excellent in hue, and free from coloring of a melt.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the method for improving the hue of bisphenol A by adding the above-mentioned additives still has a sufficient hue improving effect. What is not achieved is that a trace amount of a strong acid coexisting in the crystal adduct at the time of adding the additive is found to deteriorate the hue of bisphenol A and neutralize such a strong acid with a strong alkali. Then, they found that the excess strong alkali used for the neutralization and the strong alkali metal salt by-produced deteriorated the hue of bisphenol A, and furthermore, the crystalline adduct containing such a trace amount of a strong acid contained an aliphatic carboxylic acid. Bisphenol A obtained by adding and mixing an acid salt and evaporating and removing phenol at a temperature of 130 to 200 ° C. under reduced pressure has excellent hue and is soluble. It found that those which are markedly inhibited the time course of the hue of the object, and have completed the present invention. That is, according to the present invention, bisphenol A and phenol are used, and a strong acidic substance is contained in an amount of 0.3 meq / l or less.
After adding and mixing an aliphatic carboxylate in an amount equivalent to neutralization of the strongly acidic substance in the crystal adduct to the crystal adduct under the weakly acidic condition containing the mixed amount , phenol is added at a temperature of 130 to 200 ° C. under reduced pressure. There is provided a method for producing high-grade bisphenol, which is characterized in that it is removed by evaporation.

The crystalline adduct of bisphenol A and phenol used in the present invention is produced by a conventionally known method. That is, an excess phenol and acetone are reacted in the presence of a strong acid catalyst to obtain a reaction product containing bisphenol A, and the reaction product is subjected to a crystallization treatment to obtain a crystal adduct of bisphenol A and phenol. Can be obtained. In this case, the purity of the crystal adduct can be improved by performing the crystallization step in multiple stages, or by washing the crystal adduct, etc., but in the crystal adduct, a reaction between phenol and acetone serves as a catalyst. A very small amount of the used strongly acidic substance is often mixed. This strongly acidic substance reacts with phenol or bisphenol A under heating conditions to promote the generation of coloring substances and impurities, and lowers the purity of the recovered bisphenol A and phenol. On the other hand, strongly acidic substances used as a catalyst in the reaction between phenol and acetone are generally removed by a neutralization treatment after the reaction,
Although it is also removed by a multi-step crystallization process, the removal is often not complete, and a small amount of a strongly acidic substance is usually mixed in the crystal adduct. The present invention uses a crystalline adduct containing such a trace amount of a strong acid as a raw material. The mixing amount of the strongly acidic substance in the crystal adduct used in the present invention is usually 0.3 meq / l or less. Such a crystal adduct is added to and dissolved in an aqueous methanol solution whose acidity has been adjusted so as to show a pH of 5.0, and the pH is measured in a pH measurement method under substantially non-ionization conditions of phenol.
H4.0-5.5, preferably pH 4.3-5.2. As used herein, “a crystalline adduct under weakly acidic conditions” means a crystalline adduct in such a pH range. The pH of the crystalline adduct shown in the present specification was obtained by the above-mentioned measuring method. In the present invention, as described above, a crystal adduct that is under a weakly acidic condition is used. In this case, it is preferable that the melt color APHA of the crystal adduct be maintained at 15 or less. A crystalline adduct with a melt color APHA of 15 or less can be obtained by increasing the number of crystallization stages in the crystallization step of crystallizing the crystalline adduct, and can be obtained by washing the crystalline adduct with purified phenol. .

When the crystal adduct is subjected to a washing treatment using 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 washing a crystal adduct. As a result, after contacting the industrial phenol with a strong acid-type ion exchange resin, a distillation treatment was performed. The purified phenol obtained does not contain the coloring agent of the product bisphenol A, and the purified bisphenol A obtained by washing the crystalline adduct with the purified phenol and removing the phenol from the washed crystalline adduct has a hue. Was found to be extremely excellent. As the industrial phenol, commercially available products can be used, and generally, phenol purity of 99.5% by weight or more, preferably 99.93% by weight or more may be used.

The method for obtaining a purified phenol suitable for washing a crystalline adduct will be described in detail. First, industrial phenol is treated by contacting it with a strong acid type ion exchange resin. As the strong acid type ion exchange resin, a resin having a sulfone group is used, and such a strong acid type ion exchange resin is well known in the art. For example, gel-type materials such as Amberlite and Amberlist available from Rohm and Haas Co., Ltd., and Diaion available from Mitsubishi Kasei Corporation can be preferably used. The treatment of phenol using this strong acid-type ion exchange resin is carried out by a method in which phenol is passed through a packed tower containing strong acid-type ion-exchange resin, a method in which phenol is put into a stirring tank containing strong acid-type ion-exchange resin, and stirred. Can be implemented. The processing temperature is 45 to 150 ° C, preferably 50 to 150 ° C.
80 ° C. The contact time between the strong acid type ion exchange resin and phenol is 5 to 200 minutes, preferably about 15 to 60 minutes. When phenol is treated using this strong acid-type ion exchange resin, the water content in the phenol is adjusted to 0.5% by weight or less, preferably 0.1% by weight or less. If the water content is higher than this, the effect of removing impurities by the strong acid-type ion-exchange resin deteriorates. 0.5% by weight in phenol
The removal of water up to the following can be carried out by adding a known azeotropic agent to phenol and causing azeotropic distillation.

The phenol that has been contacted with the strong acid-type ion exchange resin contains high-boiling impurities, and the high-boiling impurities are separated as distillation residues by distillation. The distillation column may be operated under conditions in which phenol and high-boiling impurities can be separated, but the distillation column must be operated under conditions in which high-boiling impurities are not mixed into the phenol distilled off. It is. If the temperature is 185 ° C. or lower, the operating pressure is arbitrarily set, but the operation 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 be deteriorated. The purified phenol obtained by the above treatment has an APHA standard hue of 10 or less, and does not particularly deteriorate the hue even if it adheres to the product bisphenol.

The washing of the crystal adduct with the purified phenol may be carried out by any method capable of sufficiently bringing the crystal adduct into contact with the purified phenol. In this washing treatment, for example, after removing the mother liquor from the crystal adduct in a solid-liquid separation device such as a filter or a centrifugal separator for separating the crystal adduct, purified phenol is introduced into the solid-liquid separation device. And a crystal adduct to which a small amount of mother liquor discharged from the solid-liquid separation device adheres can be washed with purified phenol in a separate stirred tank. The ratio of purified phenol to crystal adduct used was
The proportion is 30 to 1000 parts by weight, preferably 100 to 300 parts by weight, based on 0 parts by weight. The purified phenol used after washing the crystal adduct is used as it is or as a raw phenol in a bisphenol A synthesis reaction step after being used for washing a crude crystal adduct obtained in the preceding crystallization step.

In a preferred embodiment of the invention, the crystalline adduct under weakly acidic conditions is melted in the presence of an aliphatic carboxylate and heated under reduced pressure to evaporate off the phenol. The aliphatic carboxylate used in the present invention reacts with and neutralizes a trace amount of a strongly acidic substance mixed in the crystal adduct, and produces a free aliphatic carboxylic acid by-product by the neutralization reaction. Therefore, in the present invention, when a crystalline adduct is melted in the presence of an aliphatic carboxylate and subjected to an evaporation treatment, there is no strongly acidic substance that reacts with phenol or bisphenol A to generate a coloring substance and impurities. Bisphenol A having an excellent hue can be obtained, and the coloring of the melt is significantly suppressed in the obtained bisphenol A due to the effect of preventing the coloring of the free carboxylic acid produced as a by-product. As the aliphatic carboxylate, any one can be used as long as it can react with a strongly acidic substance, but generally, an alkali metal salt,
Ammonium salts and alkaline earth metal salts are used. As the aliphatic carboxylic acid component of the aliphatic carboxylate, those having an anti-coloring effect on bisphenol A are preferably used, and conventionally known ones, for example, formic acid, oxalic acid, citric acid, tartaric acid, glycol Acid, lactic acid, malic acid, glyceric acid and the like can be mentioned.
These aliphatic carboxylate salts are decomposed or isomerized at a temperature of 160 ° C. or more during the reaction, and exhibit an excellent action as a coloring inhibitor for bisphenol A. The amount of the aliphatic carboxylate added is an amount that substantially completely neutralizes the crystalline adduct, that is, an amount equivalent to neutralization of the strongly acidic substance. It is not preferable to add a carboxylate salt in an amount larger than the neutralization equivalent amount. If a large amount of the carboxylate salt remains, the hue of the product bisphenol A deteriorates. When a carboxylate is added, the amount of free carboxylic acid produced as a by-product is small,
When the coloring prevention effect of the free carboxylic acid is small, a free carboxylic acid can be added together with the carboxylate. The amount of the free carboxylic acid added is 0.1 to 50 wtpp with respect to the crystal adduct including the by-product free carboxylic acid.
m, preferably 1 to 30 wtppm. When the crystalline adduct is heated and melted in the presence of a carboxylate, its melting temperature is 115 to 180 ° C, preferably 120 to 150 ° C.
C. and a melting pressure of 1 to 5 atm, preferably 1.atm.
0 to 1.9 atm. The melting atmosphere is preferably an atmosphere having an oxygen concentration as low as possible.
It is advantageous to use an atmosphere of not more than 05 vol%, preferably not more than 0.001 vol%. Further, in the present invention, in order to melt the crystal adduct in a short time, a method of diluting the crystal adduct with a hot phenol having little coloration such as purified phenol as described above and melting the crystal adduct, It is also possible to adopt a method of melting the adduct in the already melted liquid.

In the present invention, the heated melt of the crystal adduct to which the aliphatic carboxylate is added is subjected to an evaporation treatment.
The evaporation treatment in this case is performed at 130 to 200 ° C. under reduced pressure. A preferred evaporative treatment is one where the temperature of the entire melt is 18
The heating is performed so that the temperature is 5 ° C. or lower and at least a part of the melt is heated at a temperature of 160 ° C. or higher. If the evaporating temperature is too low, the effect of preventing the coloring of the aliphatic carboxylic acid by-produced by the reaction between the strongly acidic substance and the aliphatic carboxylic acid salt is not sufficiently exhibited, while if the temperature is too high, the aliphatic carboxylic acid is not sufficiently produced. To cause color decomposition. This evaporation process is performed under reduced pressure, and the pressure is 100 Torr or less, preferably 5 to 40 Torr. The atmosphere for the evaporation treatment is preferably an atmosphere having an oxygen concentration as low as possible, and is usually 0.005 vo% or less, preferably 0.02
The use of an atmosphere of less than or equal to 01 vol% is advantageous.

[0015]

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

[0016]

Next, the present invention will be described in more detail with reference to examples.

Example 1 Bisphenol A having a melt color of 50 APHA, obtained by reacting phenol and acetone in the presence of an acid catalyst,
Crystallize the mixture of phenol and impurities in multiple stages,
Crystal adduct (hue: APHA 5-10, pH 4.85)
Below). The additives shown in Table 1 were added to this crystal adduct, and the temperature: 150 ° C., the oxygen concentration in the atmosphere: 0.00
The mixture was melted under a condition of 10 vol%, and then the obtained melt was evaporated under the conditions of a temperature of 175 ° C., a pressure of 10 Torr and an oxygen concentration in the atmosphere of 0.0010 vol%.
Bisphenol A by substantially completely removing phenol
I got In this case, the free phenol content is 30 wt.
ppm or less. Next, this bisphenol A is
Subjected to a thermal stability test (Test A) in which the sample is kept at 175 ° C for 0 hour and 175 ° C for 2 hours in an air atmosphere, and an accelerated thermal stability test (Test B) in which air is blown in at 175 ° C for 2.5 hours. The hue at that time was evaluated. Table 1 shows the results.
Note that the experiment No. 6 to 9 show comparative examples. In addition, in the additives shown in Table 1, the additives according to the present invention (Experiment N
o. The amount of addition of 1 to 5) is equivalent to neutralization of the strongly acidic substance in the crystalline adduct (about 1 ppm with respect to the crystalline adduct), and the amount of additive for comparison (Experiment Nos. 6 to 8) Is about 20 ppm relative to the crystalline adduct.

[0018]

[Table 1]

Example 2 The procedure of Example 1 was repeated except that the melt-colored APHA was 5 to 10, pH 4.
The experiment was performed in the same manner except that 22 crystal adducts were used. Table 2 shows the results. In addition, in the additives shown in Table 2, the addition amount of magnesium citrate and sodium malate according to the present invention was equivalent to the neutralization equivalent of the strongly acidic substance in the crystal adduct (about 4 ppm based on the crystal adduct).
And the amount of citric acid used for comparison is 20 ppm based on the crystal adduct.

[0020]

[Table 2]

──────────────────────────────────────────────────の Continuation of the front page (56) References JP-A-2-231444 (JP, A) JP-B-45-22539 (JP, B1) JP-B-52-42790 (JP, B2) UK Patent Application 1022583 (GB, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 39/16 C07C 37/74 C07C 37/86 C07C 37/88 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. An aliphatic carboxylate is added to a crystalline adduct composed of bisphenol A and phenol and containing a strongly acidic substance in an amount of 0.3 meq / l or less under a weak acidic condition, and an aliphatic carboxylate in the crystalline adduct. A method for producing high-grade bisphenol, characterized in that phenol is evaporated and removed at a temperature of 130 to 200 ° C. under reduced pressure after adding and mixing a substance in an amount equivalent to neutralization. 2. The fatty acid component in the aliphatic carboxylate,
At least one selected from formic acid, glycolic acid, oxalic acid, citric acid, lactic acid, malic acid, glyceric acid and tartaric acid, wherein the alkali component forming a salt is an alkali metal, an alkaline earth metal and an ammonium salt; 2. The method according to claim 1, which is at least one member selected from the group consisting of: 3. The method according to claim 1, wherein the crystal adduct is washed with purified phenol after one or more remelting and recrystallization in phenol.