JPS5929174B2 - Purification method of prominated diphenyl ether - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying brominated diphenyl ether.

Recently, there has been a tendency for regulations regarding flame retardant plastics to be tightened in Japan and other countries, and research on various flame retardants has been actively conducted.

Decabromidiphenyl ether or prominated diphenyl ether containing it as the main component has a high content of bromine, which is effective as a flame retardant, is solid, and has a high thermal decomposition temperature, so it has extremely excellent performance as an additive flame retardant. , is already known to be very useful as a flame retardant for various plastics. In particular, it is an extremely effective flame retardant for making polyolefins such as polyethylene, polypropylene, and polystyrene flame retardant. Although various methods for producing decabromidiphenyl ether or brominated diphenyl ether containing decabrominated diphenyl ether as a main component are known, production using a brominated solvent is most advantageous since an organic solvent that requires recovery and purification is not used in the reaction.

However, this method requires purification because the reaction product crystals obtained are pale brown in color. Conventionally known purification methods include recrystallization using aromatic compounds such as toluene xylene, aliphatic halides such as dibromoethane and dichloroethane, or aromatic halides such as bromobenzene and chlorobenzene. However, this conventional method requires recovery of the organic solvent used for recrystallization,
Purification is required, and the advantage of the brominated solvent production method, which does not require an organic solvent during the reaction, is negated;
A part of the organic solvent used for recrystallization may be brominated by bromine contained in the reaction product.
Recovery and purification became more complicated, and this was not a preferred method. The present inventors investigated a method for purifying decabrominated diphenyl ether or brominated diphenyl ether containing decabrominated diphenyl ether as a main component using an aqueous solution. As a result, excess bromine was distilled by adding an inorganic acid aqueous solution to a bromine solution containing the reaction product. It has been found that colorless decabromidiphenyl ether or brominated diphenyl ether containing decabrominated diphenyl ether as a main component can be obtained by treating with an aqueous inorganic acid solution while removing the decabromidiphenyl ether.

However, with this method, the decolorization of the obtained decabrome, diphenyl ether, or brominated diphenyl ether containing these as the main component is still insufficient, and furthermore, product crystals that precipitate during the purification process adhere to the container wall, resulting in problems. Ta. As a result of further studies, the present inventors discovered that by washing the bromine solution containing the reaction product with an inorganic acid aqueous solution, it is possible to sufficiently decolorize the product and at the same time prevent crystals from adhering to the container wall. This invention has been achieved.

Therefore, the present invention provides a bromine solution containing a reaction product for producing decaprom diphenyl ether or a brominated diphenyl ether containing decaprom diphenyl ether as a main component by brominating diphenyl ether in the presence of a catalyst in bromine. Add an inorganic acid aqueous solution to the mixture, stir for a certain period of time under total reflux of bromine at a temperature between 30°C and the boiling point of bromine, and then treat with the inorganic acid aqueous solution while removing excess bromine by distillation. This is a characteristic method for purifying brominated diphenyl ether. Next, the present invention will be explained in detail.

First, decaprom diphenyl ether or a brominated diphenyl ether containing decaprom diphenyl ether as a main component is produced by a known method as follows. Diphenyl ether is added dropwise into bromine containing a catalyst over a period of 1 to 10 hours, preferably 2 to 5 hours, and bromination is carried out at a temperature below the boiling point of bromine, preferably 30 to 55°C, and then further maintained at the same temperature for 1 to 10 hours. , preferably 1
It is produced by aging for ~5 hours. As a catalyst, commonly known halogenation catalysts such as iodine, aluminum halide, iron halide, etc. are used alone or in a mixture of several kinds, and the amount used is 0.5 to 20% based on diphenyl ether. % by weight, preferably from 1 to 10% by weight.

Bromine is used in an amount of 2 to 10 times, preferably 3 to 5 times, the reaction equivalent. At the end of the ripening, the brominated diphenyl ether produced by the reaction is dissolved in excess bromine. In the purification method according to the present invention, an aqueous inorganic acid solution is added to a bromine solution of decaprom diphenyl ether or brominated diphenyl ether containing decaprom diphenyl ether as a main component, and the temperature is below the boiling point of bromine, preferably from 30°C to bromine. The bromine solution is stirred under total reflux for at least 0.5 hours, preferably 1 to 5 hours, at a temperature of the boiling point of The crystals of decaprom diphenyl ether or brominated diphenyl ether containing decaprom diphenyl ether as a main component are precipitated by distillation out of the system, and the resulting crystals are washed with water to obtain colorless decaprom diphenyl ether. Alternatively, a brominated diphenyl ether containing this as a main component is obtained.

By thoroughly washing the bromine solution with an aqueous inorganic acid solution as described above, it becomes possible to obtain colorless decaprom diphenyl ether or brominated diphenyl ether containing this as the main component, and at the same time distill excess bromine. It is possible to completely prevent the precipitated crystals from adhering to the walls of the container, which occurs when the crystals are removed and crystallized.

The inorganic acids used in the present invention are commonly known inorganic acids such as hydrochloric acid, sulfuric acid, and hydrobromic acid, and the concentration of the aqueous solution is 3 to 3.
40%, preferably 5 to 20%.

The amount of the inorganic acid aqueous solution to be used is 0.00% relative to the amount of crystal formation.
The amount is 5 to 10 times by weight, preferably 1 to 5 times by weight. If the acid concentration of the inorganic acid aqueous solution is less than 3%, the purification effect will be low;
The above is not practical. Further, if the amount of the inorganic acid aqueous solution used is less than 0.5 times the amount of crystals, stirring after the crystals have precipitated will be difficult, and if the amount is more than 10 times the amount, it is not practical. The inorganic acid aqueous solution from which the crystals have been over-separated can be azeotropically removed with water to recover the bromine, and then part or all of the bromine can be reused.

Decaprom diphenyl ether obtained by the purification process according to the present invention or brominated diphenyl ether containing it as a main component is a colorless crystal, which is more colored than the crystal obtained by recrystallization with an organic solvent. No inferiority was observed in terms of quality. This will be explained below using an example. Example 1 A flask was charged with 480f of bromine and 1y of aluminum chloride, and 17t of diphenyl ether was added dropwise over about 2 hours while stirring at a temperature of 50 to 55°C, and ripening was further carried out at that temperature for 2 hours.

Add 200y of 10% hydrochloric acid aqueous solution to the obtained reaction solution and mix for 50 minutes.
Stirring was carried out at ~55° C. for 2 hours, and the reaction solution was thoroughly brought into contact with an aqueous hydrochloric acid solution for washing. Heating was then gradually increased to distill off excess bromine. The produced crystals were filtered, washed with water, and dried to obtain 95.5y of white crystals. Melting point 298-30
The temperature was 7°C, the bromine content was 83.2%, and no crystals were observed to adhere to the container wall. Comparative Example 1 In Example 1, 200% water was used instead of the 10% aqueous hydrochloric acid solution.
Orange-yellow crystal 9 was obtained by carrying out the same operation as in Example 1 using f.
Obtained 5.7y.

The melting point was 272 DEG -302 DEG C., the bromine content was 84.1%, and 38.27 of the obtained crystals were firmly attached to the reactor wall. Comparative Example 2 In Example 1, after adding 20% aqueous hydrochloric acid solution 2007 to the reaction solution, heating was immediately increased to distill off bromine, and stirring was continued for an additional 3 hours at a temperature of 80°C.

▲Washing with water and drying gave slightly yellow crystals 95.3f. The melting point was 296-305°C, the bromine content was 83.0%, and 16.17 of the obtained crystals were firmly attached to the reactor wall. Examples 2 to 8 An inorganic acid aqueous solution having the type, concentration and liquid amount listed in Table-1 was added to the reaction solution obtained by carrying out the bromination reaction and aging according to the method described in Example 1. A washing treatment was carried out according to Example 1 under the temperature and time conditions described in Example 1, and then bromine was distilled off and post-treated in the same manner as in Example 1, and the results shown in Table O-1 were obtained.

Claims (1)

[Claims] 1. When producing decabrominated diphenyl ether or brominated diphenyl ether containing this as the main component by brominating diphenyl ether in the presence of a catalyst in bromine, an aqueous inorganic acid solution is added to the bromine solution containing the reaction product, and the mixture is heated at 30°C to A method for purifying brominated diphenyl ether, which comprises stirring at a temperature of the boiling point of bromine for at least 0.5 hours under total reflux of bromine, and then treating with an aqueous inorganic acid solution while removing bromine by distillation.