JPH0570617B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a method for purifying tetrabromobisphenol A with high purity and high yield. "Prior Art" Tetrabromobisphenol A has recently attracted attention as a flame retardant for epoxy resins, ABS resins, etc. Usually, tetrabromobisphenol A is produced by dissolving or dispersing bisphenol A in a halogenated hydrocarbon and water, and adding bromine thereto. Tetrabromobisphenol A obtained by the above method contains by-product hydrogen bromide and bisphenol A di- and tribrominated products and penta- to octasubstituted products, and often has a slight yellow color. There is. Therefore, purification is usually performed to remove these impurities from tetrabromo bisphenol A. A known method for purifying tetrabromobisphenol A is to dissolve tetrabromobisphenol A in a lower alcohol such as methanol or an aromatic hydrocarbon such as benzene, and crystallize tetrabromobisphenol A from the solution. It is. When a lower alcohol is used as a solvent, it is necessary to add a large amount of water during crystallization because tetrabromobisphenol A has very good solubility. Therefore, when lower alcohols are reused, a separation operation from water is required, which is not suitable for industrial use.
Furthermore, it is difficult to obtain the high-quality tetrabromobisphenol A desired in the present invention. On the other hand, when only aromatic hydrocarbons are used as a solvent, they have poor solubility for impurities.
Many impurities remain in the tetrabromobisphenol after crystallization, and in order to obtain the high-quality tetrabromobisphenol A desired in the present invention, it is necessary to repeat purification several times, and further crystallization is required. In addition to impurities, a relatively large amount of tetrabromobisphenol A is dissolved in the subsequent aromatic hydrocarbon layer, resulting in a decrease in product yield. "Problems to be Solved by the Invention" The present invention aims to improve the product yield, which was not satisfied by the conventional methods described above, and to develop a method for industrially producing tetrabromobisphenol A with high purity and good color. It's something I'm trying to release. "Means for Solving the Problems" The present inventors have discovered that tetrabromobisphenol A
As a result of our earnest efforts to industrially produce TBA (hereinafter referred to as TBA) with high purity and high yield, we found that crude TBA after the bromination reaction contained aromatic hydrocarbons in an amount of 0.3 to 3 times the weight of the TBA. A mixed solvent consisting of a halogenated hydrocarbon and water in an amount of 0.4 to 1 times the weight of the mixed solvent are added and dissolved by heating, and after separation of the water layer, a part of the mixed solvent is recovered by evaporation or not. 10 to 30
TBA characterized by crystallization at a temperature of ℃
We have discovered a method for purifying this. The main aim of the present invention is to improve the quality of TBA by using a mixed solvent consisting of aromatic hydrocarbons and halogenated hydrocarbons, and to reduce the amount of TBA dissolved in the solvent layer after crystallization. The aim is to improve the rate. That is, by heating and dissolving the crude TBA after the bromination reaction in the mixed solvent and water, the hydrogen bromide contained in the crude TBA is removed to the water layer side, and a part of the mixed solvent is recovered by evaporation or evaporative recovery. TBA is crystallized by cooling without cooling and remains in the solvent layer after crystallization.
This method reduces the amount of TBA and removes impurities such as di- and tri-bromine substituted products and penta- to eight-bromine substituted products of bisphenol A. Aromatic hydrocarbons have good solubility in TBA;
Halogenated hydrocarbons have the property of being highly soluble in TBA impurities. By using these two types of solvents, it became possible to achieve high purity of TBA, which could not be achieved using aromatic hydrocarbons alone. Furthermore, an unexpected result was obtained in that the hue of TBA after crystallization was better than that obtained by known methods. Furthermore, by using the mixed solvent according to the present invention, the amount of TBA dissolved in the solvent layer after crystallization is reduced compared to the case of aromatic hydrocarbon alone, and as a result, the yield of the product is improved. become. After dissolving crude TBA in a mixed solvent and water and separating the aqueous layer,
If a part of the mixed solvent is not evaporated and recovered, it is preferable to dissolve it under pressure to reduce the amount of the mixed solvent used, and this is an effective method for further improving the product yield. On the other hand, when dissolving crude TBA in a mixed solvent and water and separating the aqueous layer, a part of the mixed solvent is evaporated and recovered.
The amount of mixed solvent is 1 to 3 times the weight of TBA, and after dissolving at a temperature of 70 to 90 degrees Celsius with stirring, the aqueous layer is separated and removed at the same temperature, and the amount is 30 to 80 times the weight of crude TBA.
It is advisable to leave the mixed solvent in an amount of 40-60% by weight, preferably 40-60% by weight. The residual amount of mixed solvent is 30
If it is less than 80% by weight, the amount of impurities in the product will increase, and if it is more than 80% by weight, it will dissolve in the mixed solvent.
The amount of TBA is large and the product yield will be reduced. Further, during evaporation and recovery of the mixed solvent, it is preferable to keep the temperature as low as possible in order to prevent coloring of the product, and it is preferable to carry out the process under reduced pressure of 10 to 300 mmHg, preferably 30 to 100 mmHg. The mixed solvent used in the present invention may be any combination of aromatic hydrocarbons and halogenated hydrocarbons, but the difference in boiling point is small;
From the viewpoint of appropriate solubility for TBA and impurities, a combination of benzene-carbon tetrachloride or toluene-perchloroethylene is preferred. The ratio of the mixed solvent in the present invention is aromatic hydrocarbon: halogenated hydrocarbon = 3 to 3 by weight.
20:1, preferably 5 to 10:1. If aromatic hydrocarbon/halogenated hydrocarbon = 3 or less, a relatively high temperature is required to dissolve the crude TBA, resulting in a poor color of the product; if it is 20 or more, it is less effective than known methods. However, it is not preferable for obtaining the desired product quality in the present invention. In addition, the amount of mixed solvent used is 1 to 1 to the weight of crude TBA when the pressure at the time of dissolving crude TBA is normal pressure.
The amount is 3 times, preferably 1.5 to 2 times, and when carried out under pressure, the amount is 0.3 to 1 times, preferably 0.6 to 0.8 times the weight of crude TBA. The dissolution temperature of TBA in the present invention varies depending on the proportion of the mixed solvent, the amount used, and the pressure, and may be any temperature as long as it dissolves, but it should be as low as possible for the purpose of improving the color of the product. It is preferable to carry out the process at a temperature of 70 to 90°C when the process is carried out at normal pressure, and at a temperature of 90 to 120°C when the process is carried out under pressure. In addition, when dissolving crude TBA under pressure, the pressure is 0.5 to 3 kg/cm ² in gauge pressure, preferably 1 to 2 kg/cm 2 .
A range of Kg/cm ² is good. If it is less than 0.5Kg/cm ² , there is almost no effect in reducing the amount of mixed solvent, and if it is more than 3Kg/cm ² , it is effective to reduce the amount of mixed solvent and improve product yield, but inevitably crude TBA The temperature during melting becomes high, which is undesirable as it leads to deterioration of the quality of the product, especially the hue. The amount of water used in the present invention is 0.4 to 1 times the weight of the mixed solvent used, preferably 0.5 to 1 times the weight of the mixed solvent used.
0.8 times the amount is better. The crystallization temperature in the present invention is 10 to 30°C, preferably 15 to 25°C. If the crystallization temperature is below 10°C, the content of impurities in the product will increase, and if it is above 30°C, the yield of the product will decrease, which is not preferable. "Operation" In the method for refining TBA, by using a mixed solvent consisting of an aromatic hydrocarbon and a halogenated hydrocarbon, it becomes possible to produce highly purified TBA at a high yield. This is because aromatic hydrocarbons
This is based on the fact that it is a good solvent for TBA and that halogenated hydrocarbons are good solvents for impurities consisting of bisphenol A substituted with di-, tri-bromine and penta-octabromine. In addition, two types of solvents are miscible. The synergistic effect of the above items is thought to be due to this. In addition, dissolving crude TBA under pressure
This makes it possible to reduce the amount of mixed solvent used and reduces the amount of TBA dissolved in the mixed solvent layer after crystallization, which has the effect of further improving product yield. In addition, reducing the amount of solvent present during crystallization by evaporating and recovering the solvent before crystallization is an effective way to reduce the amount of solvent present during crystallization.
This is an effective method to reduce TBA amount and improve product yield. Furthermore, by using a mixed solvent and performing the recovery operation of the mixed solvent under reduced pressure before crystallization, the unexpected effect of improving the hue of the product compared to conventional methods can be obtained. Generally, high purity and high yield of TBA are contradictory, and it is difficult to satisfy both as long as a single solvent is used. By using the mixed solvent according to the present invention, it is possible to prevent product purity from deteriorating even when the amount of solvent during crystallization is reduced. In addition, it is extremely difficult to separate and recover TBA dissolved in the solvent layer after crystallization, which leads to substantial loss of TBA, which is an important item when producing TBA industrially. It is something. The TBA purified by the present invention has a purity of 98.5% or more as determined by liquid chromatography analysis, and has a purity of 98.5% or more as determined by liquid chromatography analysis.
Yield over 94.5% based on weight of TBA, 30% of TBA
Hue 30APHA when made into a wt% methanol solution
It is as follows. This is TBA purified by a known method with a purity of 97~
98%, yield 90-92.1, hue 30-60, which is superior compared to APHA. The present invention will be specifically explained below using examples, but the present invention is not limited only to these examples. "Examples and Comparative Examples" Examples 1, 3, 4 and Comparative Examples 1, 3 Capacity 1 with thermometer, stirring blade and heating device
In a separable flask, 150 g of crude TBA (purity 95.5
%, TBA) was taken, and to this were added the type and amount of solvent and demineralized water shown in Table 1. While stirring, the temperature was raised to the temperature shown in Table 1 to dissolve the crude TBA, and then the mixture was allowed to stand and the separated aqueous layer was separated and removed. Thereafter, the mixture was cooled to the crystallization temperature shown in Table 1, and the resulting crystals were filtered and dried at a temperature of 100° C. under a nitrogen stream to obtain purified TBA. The weight of the purified TBA obtained was measured, divided by the weight of TBA in the crude TBA (143.3 g), expressed as a percentage, and shown in Table 1 as the yield. Further, Table 1 shows the purity of purified TBA as determined by liquid chromatography analysis, the hue when it was made into a 30% by weight methanol solution, and the bromide ion concentration as determined by potentiometric titration with silver nitrate. In Comparative Example 3 using methanol as a solvent, after dissolving crude TBA in methanol, the amount of demineralized water shown in Table 1 was slowly added dropwise while stirring, and crystallization was performed after the addition was completed. Examples 2, 5 and Comparative Example 2 Capacity 1 with thermometer, stirring blade and heating device
In a stainless steel autoclave, 2.4% by weight of di- and tri-brominated products and penta- to octa-brominated products were added as impurities.
Take 150 g of crude TBA after the bromination reaction (purity 95.5%, 143.3 g as TBA) containing 1.6% by weight, 850ppm of bromide ions, and 0.4% by weight of water. Brine was added. While stirring, the crude TBA was dissolved at the pressure and temperature shown in Table 1. Thereafter, the mixture was cooled to the crystallization temperature shown in Table 1, and the resulting crystals were filtered and dried at a temperature of 100° C. under a nitrogen stream to obtain purified TBA. The weight of the purified TBA obtained was measured, divided by the weight of TBA in the crude TBA (143.3 g), expressed as a percentage, and shown in Table 1 as the yield. Further, Table 1 shows the purity of purified TBA as determined by liquid chromatography analysis, the hue when it was made into a 30% by weight methanol solution, and the bromide ion concentration as determined by potentiometric titration with silver nitrate. Examples 6 to 10 and Comparative Examples 4 to 6 Two or three impurities were added to a separable flask with a capacity of 1 equipped with a recovery device with a cooling tube connected to a thermometer, stirring blade, and a pressure reduction device for recovering the evaporated solvent. 150 g of crude TBA (purity 95.9%,
143.8 g of TBA) was taken, and to this were added the type and amount of solvent and demineralized water shown in Table 2. While stirring, the temperature was raised to the temperature shown in Table 2 to dissolve the crude TBA, and the mixture was allowed to stand still to remove the separated aqueous layer. Thereafter, in Examples 6 to 10 and Comparative Example 5, the pressure in the system was gradually reduced, and the amount of solvent shown in Table 2 was recovered while maintaining the degree of vacuum and liquid temperature shown in Table 2. After returning the pressure in the system to normal pressure, it was cooled to the crystallization temperature shown in Table 2. The generated crystals were filtered and dried at a temperature of 100°C under a nitrogen stream to obtain purified TBA. The weight of the purified TBA obtained was measured, divided by the weight of TBA in the crude TBA, 143.3 g, and expressed as a percentage, which is shown in Table 2 as the yield. Further, Table 2 shows the purity of purified TBA as determined by liquid chromatography analysis, the hue when it was made into a 30% by weight methanol solution, and the bromide ion concentration as determined by potentiometric titration with silver nitrate.

【table】

[Table] "Effects of the Invention" The purification method of the present invention involves heating and dissolving crude TBA in a mixed solvent consisting of a predetermined amount of an aromatic hydrocarbon and a halogenated hydrocarbon and water, separating the aqueous layer, and dissolving the crude TBA as needed. By evaporating a portion of the mixed solvent and then cooling it to a predetermined temperature to crystallize TBA, it is possible to obtain high-purity TBA at a high yield, which was not possible with conventional methods. . Furthermore, it also shows the unexpected effect that TBA with very little coloring can be obtained.

Claims (1)

[Scope of Claims] 1. A mixed solvent consisting of crude tetrabromobisphenol A and an aromatic hydrocarbon and a halogenated hydrocarbon in an amount of 0.3 to 3 times the weight of tetrabromobisphenol A, and the weight of the mixed solvent. 0.4~
Add one volume of water and dissolve by heating. After separating the aqueous layer, a part of the mixed solvent was collected by evaporation or without evaporation.
A method for purifying tetrabromobisphenol A, which comprises crystallizing at a temperature of ~30°C. 2 Mixed solvent is aromatic hydrocarbon in weight ratio:
The method for purifying tetrabromobisphenol A according to claim 1, wherein the halogenated hydrocarbon ratio is 3 to 20:1. 3. The method for purifying tetrabromo bisphenol A according to claim 1 or 2, wherein the mixed solvent is a combination of benzene and carbon tetrachloride. 4. The method for purifying tetrabromo bisphenol A according to claim 1 or 2, wherein the mixed solvent is a combination of toluene-perchloroethylene. 5. A method for purifying tetrabromobisphenol A according to any one of claims 1 to 4, wherein the heating is heating under pressure and after separation of the aqueous layer, a part of the mixed solvent is cooled without being evaporated and recovered. . 6 A patent in which the dissolution temperature is 70 to 90°C, and after separation of the aqueous layer, a part of the mixed solvent is evaporated and recovered under reduced pressure, leaving 30 to 80% by weight of the mixed solvent based on the weight of tetrabromobisphenol A. A method for purifying tetrabromobisphenol A according to any one of claims 1 to 4.