JPS648608B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing bisphenol A (hereinafter referred to as BPA), and more specifically, from a bisphenol A/phenol adduct (hereinafter referred to as BPA adduct) obtained by reacting phenol with acetone, BPA This relates to a method for recovering. BPA is useful as a raw material for polycarbonate resins, epoxy resins, etc. As a method for producing BPA, for example, a method is known in which phenol and acetone are reacted in the presence of a hydrochloric acid catalyst. In this reaction, BPA is obtained as an adduct with phenol, so usually, after neutralizing the hydrochloric acid in the reaction mixture, the solvent is removed, and then the BPA adduct is distilled to convert BPA and phenol. Each is disassembled and collected. However, in order to completely separate the BPA adduct into BPA and phenol, it is usually necessary to heat the BPA adduct to a temperature of 200°C or higher under reduced pressure when carried out on an industrial scale; For example, 200
When exposed to high temperatures above ℃, there is a tendency for coloring to occur. Therefore, in order to prevent BPA from coloring, a method of distilling the BPA adduct under high vacuum and at a temperature as low as possible below 200°C has been considered, but as a practical matter, the degree of vacuum is high for industrial use. , it is difficult to adopt this method. However, even if colored BPA is obtained by distilling the BPA adduct obtained using a hydrochloric acid catalyst at a temperature of 200°C or higher, this BPA can be removed by a method such as recrystallization in benzene (Japanese Patent Publication No. 43 - No. 218),
Or by purification methods such as recrystallization in chlorobenzene (Industrial Chemistry Magazine Vol. 70, No. 11, p. 248).
Coloring components can be easily removed. Therefore, in the case of the above hydrochloric acid catalyzed method, it is obtained by reaction. There was no need to keep the BPA adduct distillation temperature below 200°C. On the other hand, a method for producing BPA is also known in which phenol and acetone are reacted using a catalyst made of a strongly acidic cation exchange resin (hereinafter referred to as K-RIE). However, BPA obtained by this method
If BPA is colored by distilling the adduct, the colored components cannot be removed by applying the purification method described above. Based on the above findings, the present inventors believe that when K-RIE is used as a catalyst, BPA cannot be easily purified by post-treatment if it is colored during the distillation process. ,
We thought it was necessary to adopt a process that does not cause BPA coloration, and after various studies, we completed the present invention. That is, the gist of the present invention is to react a BPA adduct obtained by reacting phenol and acetone in the presence of a catalyst consisting of K-RIE at 160 to 185°C under reduced pressure.
Crude BPA containing 1 to 10% by weight of phenol is recovered by distillation at a temperature of It consists in a method for producing BPA, which is characterized by its recovery. The present invention will be explained in detail below. The method for producing BPA, which is the subject of the present invention, is a method in which phenol and acetone are reacted using K-RIE as a catalyst. As K-RIE, usually,
A commercially available gel type or porous type sulfonic acid type cation exchange resin or the resin is treated with a mercapto compound such as mercaptoalkylamine or mercaptoalkylpyridine to convert the sulfonic acid groups from 3 to 30%.
Examples include resins modified with 30 mol%. The reaction between phenol and acetone is usually carried out without substantially using a solvent as a third component, for example, using phenol in an excess of 6 to 12 moles relative to acetone, and at a reaction temperature of 0 to 120°C. The reaction is preferably carried out under conditions of 50 to 100° C. and a reaction pressure of normal pressure to 5 kg/cm ² . In the case of continuous piston flow reaction, the reaction time is usually determined by the space velocity (S, V)
is 0.1 to 20 hr ^-1 , preferably 1 to 15 hr ^-1 ,
In the case of batch reaction, the reaction time is 0.1 to 20 hours, preferably 0.3 to 5 hours. After the reaction is complete, the mixture contains BPA in phenol.
is dissolved, but normally when it is crystallized,
Since it precipitates as a crystal of an adduct of BPA and phenol, this crystal is collected. This crystallization can usually be carried out by cooling the reaction mixture to below 50°C. The crystals precipitated here are separated by filtration and, if necessary, washed with phenol and recovered. In the present invention, in order to recover BPA from the BPA adduct obtained as described above, it is essential to perform distillation under specific conditions and then recrystallize it in an aqueous medium. be. First, the BPA adduct is distilled, which in the present invention is usually carried out at a temperature of 160 to 185°C, preferably 165 to 180°C, under a reduced pressure of 10 to 100 mmHg. If this temperature is higher than the above range, you will get
There is a risk that BPA will cause coloration, and if it is lower than the above range, the degree of vacuum will be high, making the operation not only troublesome but also uneconomical when carried out industrially. In the present invention, crude BPA containing 1 to 10% by weight, preferably 1 to 5% by weight of phenol as a BPA phenol adduct is recovered by subjecting the BPA adduct to vacuum distillation under the above conditions. The distillation apparatus used for this distillation is usually a thin film evaporator, and an apparatus with as short a residence time as possible is preferable. The crude BPA recovered by distillation is then dissolved in an aqueous medium of 0.5 to 10 times, preferably 1 to 5 times the weight of BPA, and then recrystallized. If the amount of aqueous medium used is too small, the phenol in the crude BPA cannot be removed sufficiently, and if it is too large, heating and cooling operations of the medium for recrystallization will be industrially disadvantageous. The recrystallization operation is usually carried out by heating an aqueous medium to 95 to 100°C under normal pressure to dissolve substantially all of the crude BPA, and then cooling it to below 95°C, preferably below 90°C. Ru. Moreover, as this crystallization method, not only cooling crystallization but also evaporation concentration crystallization can be employed. In this recrystallization, most of the phenol contained in the crude BPA as a BPA phenol adduct becomes free phenol and is transferred to the aqueous phase and removed, so that highly pure BPA can be obtained.
Furthermore, in the present invention, since BPA is not colored during the distillation process, the crude BPA to be subjected to recrystallization does not originally contain coloring components. Therefore, recrystallization does not substantially improve the color tone of BPA. BPA crystals after recrystallization are collected by filtration according to a conventional method. As described above, according to the present invention, BPA can be recovered from a BPA adduct obtained when K-RIE is used as a catalyst by adopting a process that combines a specific distillation operation and a recrystallization operation. The BPA used in this process does not become colored, and it is an economical method even when carried out industrially. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Example: In a 500 ml reactor with a stirrer and temperature regulator,
300 g of phenol, 18.5 g of acetone, and 60 g of a catalyst obtained by modifying 16 mol% of the sulfonic acid group of a sulfonic acid type cation exchange resin (manufactured by Mitsubishi Chemical Industries, Ltd., trade name Diaion SK-104) with 4-mercaptoethylpyridine, The reaction was carried out for 0.5 hour at a temperature of 70° C. with stirring. After the reaction was completed, the reaction mixture was filtered to remove the catalyst, and the filtrate was cooled to a temperature of 42°C to precipitate BPA adduct crystals, which were collected by filtration. The crystals of the bisphenol A adduct thus obtained were heated to 130° C. to melt them, and then fed to a thin film evaporator under the conditions shown in Table 1 for distillation. In addition, when we measured the content and degree of coloration of BPA adducts in the crude BPA recovered by distillation, we found that
It was as shown in the table. Next, add 50g of this crude BPA using a temperature controller.
Pour BPA into a 200ml stirring vessel with water in the ratio shown in Table 1, heat it to 100°C, and mix
After completely dissolving the BPA crystals and holding for 30 minutes,
It was gradually cooled to a temperature of 90°C to precipitate BPA crystals. After separating the crystals by filtration, the content of BPA adducts and the degree of coloration in the recovered crystals were measured, and the results shown in Table 1 were obtained.

[Table] Reference example BPA crystal obtained in the above comparative experiment example (No. 6)
Based on a known purification method, 25 g was heated and dissolved in 150 ml of toluene or chlorobenzene, and then recrystallized by cooling to a temperature of 78°C. The degree of coloration of the obtained crystals was measured, and the results are shown in Table 2. It was as shown in.

[Table] From the results in Table 2, it can be seen that the BPA adduct obtained using K-RIE as a catalyst cannot be easily purified by known purification methods if coloring occurs during the BPA recovery process.

Claims (1)

[Claims] 1 Bisphenol A and phenol adduct obtained by reacting phenol and acetone in the presence of a catalyst made of a strongly acidic cation exchange resin are distilled under reduced pressure at a temperature of 160 to 185°C to convert phenol into
Collect crude bisphenol A containing 10% by weight,
Next, this was added to bisphenol A from 0.5 to
After dissolving it in an aqueous medium 10 times its weight, it is recrystallized,
A method for producing bisphenol A, which comprises collecting precipitated crystals of bisphenol A.