JPH05294874A - Production of bisphenol a - Google Patents

Abstract

(57) [Summary] [Purpose] From the adduct of bisphenol A and phenol,
Operate the centrifugal thin film evaporator to remove phenol by evaporation stably for a long period of time. In a method for producing bisphenol A by removing phenol from bisphenol A and a phenol adduct, the adduct is charged into a centrifugal thin film evaporator kept at a pressure of 45 Torr or more. The phenol is removed by evaporation. [Effect] It is possible to stably dephenolize for a long period of time and to obtain high-purity bisphenol A.

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 bisphenol A. For details, see Bisphenol A and phenol.
The present invention relates to a method for producing high-purity bisphenol A by removing phenol from an adduct with a phenol.

[0002]

2. Description of the Related Art Bisphenol A, that is, 2,2-bis (4-hydroxyphenyl) propane, is a compound which is solid at room temperature. Acetone and excess phenol are acidified with hydrochloric acid, acidic cation exchange resin or the like. It is obtained by reacting in the presence of a catalyst. One of the methods for recovering bisphenol A from this reaction mixture is to remove water and / or catalyst from the reaction mixture and then cool it to precipitate an adduct of bisphenol A and phenol, The crystals are separated from the mother liquor,
Then, it is a method of recovering bisphenol A by dephenol treatment. As a dephenol treatment method performed here, a method using a centrifugal thin film evaporator is generally used, as disclosed in JP-A-3-95135. Since this method is not exposed to high temperature for a long time, it is an advantageous method in that the decomposition and coloring of bisphenol A can be suppressed to a minimum, but crystals are precipitated during operation and stable operation is possible. You may not be able to

[0004]

DISCLOSURE OF THE INVENTION The present invention uses a centrifugal thin-film evaporator to evaporate and remove phenol from an adduct of bisphenol A and phenol for a long period of time, and to remove bisphenol. The purpose is to produce A.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have examined the cause of malfunction of a centrifugal thin film evaporator, which is caused by the precipitation of bisphenol A crystals in the centrifugal thin film evaporator. The present invention has been completed by finding out that it is necessary to keep the pressure of the centrifugal thin film evaporator at a certain level or more in order to find out the above and prevent it.

That is, the present invention provides a method for producing bisphenol A by removing phenol from the adduct of bisphenol A and phenol, and adding the adduct to 45 To
A method for producing bisphenol A, which comprises charging a centrifugal thin film evaporator held at a pressure of rr or higher to remove the phenol by evaporation.

The adduct of bisphenol A and phenol is obtained by precipitating crystals of the reaction mixture of acetone and phenol by cooling the reaction mixture after removing low-boiling substances, removing the catalyst, etc., if necessary. You can If necessary, most of the impurities can be removed by recrystallizing this crystal with phenol or washing it. The adduct targeted by the present invention is obtained in this manner, and an adduct of high purity is preferable.

To remove the phenol from this adduct, it is charged to a centrifugal thin film evaporator. Conventionally, the operating conditions of centrifugal thin film evaporators have been mainly focused on the reduction of residual phenols, and therefore, they are operated at a high vacuum of 30 Torr or less. However, since this adduct contains at least 30 wt% or more of phenol, when it is suddenly charged into a high-vacuum centrifugal thin-film evaporator, a large amount of the phenol evaporates in a short time, and as a result, the latent heat of vaporization causes the liquid to disappear. It was confirmed that the temperature was lowered and crystals of bisphenol A were precipitated. Evaporation is suppressed by lowering the charging temperature of the additive to the centrifugal thin film evaporator, and bisphenol A is dissolved in the residual phenol to prevent the precipitation of crystals in the charging part. When the phenol evaporates in the evaporation part of
Crystals are deposited due to the relationship between the residual phenol and the liquid temperature. When crystals are deposited in the charging part, the crystals adhere to the rotating part of the centrifugal thin film evaporator, the rotation becomes unbalanced, and the centrifugal thin film evaporator itself vibrates or centrifugally acts to make stable operation impossible. Further, when crystals are deposited in the evaporation part, the crystals are caught between the rotary blade and the body of the centrifugal thin film evaporator, and an abnormal force is applied to the motor to make stable operation impossible.

An example of a centrifugal thin film evaporator used in the present invention is shown in FIG. In the figure, 1 is a body, 2 is a raw material charging line, 3
Is a vapor outlet line, and 4 is a liquid outlet line. Inside the body 1, rotary blades are provided so as to rotate close to the inner wall of the body. And the steam outlet line is in communication with the vacuum system. If necessary, a plurality of centrifugal thin film evaporators can be continuously provided. Then, the centrifugal thin film evaporator is operated while being kept at a pressure of 45 Torr or more, preferably 50 Torr or more. Although there is no upper limit of the pressure, a lower pressure is preferable for the purpose of efficiently performing dephenoling in a short time, and therefore a reduced pressure of 100 Torr or less is preferable. The centrifugal thin film evaporator is heated by a jacket or the like and kept at a predetermined temperature, but at about 170 to 220 ° C. to prevent thermal decomposition of bisphenol A.
It is recommended to keep

A raw material line 2 is used for such a centrifugal thin film evaporator.
The bisphenol A and the phenol adduct charged from the reactor were heated, the phenol was evaporated, the phenol was discharged from the vapor outlet line, and the bisphenol A or the subsequent centrifugal thin film was discharged from the liquid outlet line. When the evaporator or the like continues, the mixed solution of bisphenol A and phenol is discharged. At this time, since the pressure of the centrifugal thin film evaporator is set to 50 Torr or more, instability due to crystal precipitation in the centrifugal thin film evaporator does not occur.

[0011]

FIG. 2 shows the centrifugal thin film evaporator having the above structure,
The relationship between pressure, temperature, and bisphenol A concentration (BPA concentration) in the liquid phase was investigated. If the temperature is above the crystal precipitation limit at the BPA concentration, no crystals will be precipitated and no problem will occur, but in reality, even if some crystals are precipitated, there is no problem in operation, and 20 wt% shown in FIG. It was confirmed that no problem occurred if the crystal concentration was below. Therefore, it can be seen that if it is 50 Torr or more, the crystal concentration does not exceed 20 wt% at most of the BPA concentration, and no problem occurs. Also, the shape of the centrifugal thin film evaporator,
Depending on the wall temperature or the charging speed of additional materials, temperature, etc.,
Although the appropriate pressure may fluctuate to some extent, there is an upper limit of the temperature as described above, and for the purpose of efficiently performing dephenoling in the shortest possible time, it is not possible to maintain the condition of 50 Torr or more. It is effective, and more preferably, it is performed under the condition that the crystal concentration of FIG. 2 does not exceed 20 wt%. The crystal concentration of 20 wt% in the present invention means a calculated value.

[0012]

【Example】

Example 1 An adduct consisting of 70 wt% of bisphenol A and 30 wt% of phenol was preheated to 150 ° C. and charged into a centrifugal thin film evaporator as shown in FIG. The centrifugal thin film evaporator was heated by steam at 200 ° C. in the jacket and kept at 50 Torr. At this time, the concentration of phenol in the liquid extracted from the liquid outlet line 4 was 4 wt%. Further, the centrifugal thin film evaporator operated under these conditions was able to continue stable operation without abnormal phenomena such as vibration, generation of centrifugal force, and overload of the motor for 30 days. Furthermore, the phenol concentration in the liquid was 4.3 wt% when carried out in the same manner as above except that the adduct was preheated to 130 ° C. and charged into the centrifugal thin film evaporator. In the same case, stable operation could be continued.

Comparative Example 1 The procedure of Example 1 was repeated, except that the adduct was preheated to 150 ° C. and charged into a centrifugal thin film evaporator maintained at 40 Torr. At this time, the concentration of phenol in the liquid is 2.7 wt.
%, The centrifugal thin-film evaporator vibrated on the 8th day and a centrifugal force was generated, which made stable operation impossible. However, when the decompression degree of the centrifugal thin film evaporator was lowered to 600 Torr and the temperature of the liquid was raised to 190 ° C., this was solved. Furthermore, the same procedure as in Example 1 was carried out except that the adduct was preheated to 130 ° C. and charged into a centrifugal thin film evaporator kept at 40 Torr. At this time, the concentration of phenol in the liquid was 2.7 wt%, but the centrifugal thin film evaporator was unable to operate due to overload of the motor on the second day.

[0014]

Industrial Applicability According to the production method of the present invention, the phenol is stably evaporated from the adduct of bisphenol A and phenol by a centrifugal thin film evaporator for a long period of time to obtain a high concentration. It is possible to obtain pure bisphenol A.

[Brief description of drawings]

1 is a schematic diagram of a centrifugal thin film evaporator.

FIG. 2 is a graph showing the relationship between bisphenol A concentration in the liquid phase and temperature.

[Explanation of symbols]

 1 Body 2 Raw material charging line 3 Steam outlet line 4 Liquid outlet line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Tani 5-2-12 Wakakidai, Fukuma-cho, Munakata-gun, Fukuoka Prefecture (72) Inventor Shinji Yoshizuka 3485-79 (72) Nakamura, Kurate-cho, Kurate-gun, Fukuoka Prefecture Nakamura 1007 Oho, Munakata City, Fukuoka Prefecture

Claims (2)

[Claims] 1. A method of producing bisphenol A by removing phenol from an adduct of bisphenol A and phenol, wherein the adduct is kept at a pressure of 45 Torr or more. A method for producing bisphenol A, which comprises charging the mixture into a reactor to evaporate and remove the phenol. 2. A method for producing bisphenol A by removing phenol from the adduct of bisphenol A and phenol, wherein the adduct is kept at a pressure of 45 Torr or more. A method for producing bisphenol A, characterized in that the phenol is vaporized and removed under conditions that the concentration of crystals in the liquid phase does not exceed 20 wt%.