JPS5914013B2 - 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.

In recent years, regulations regarding the flame retardancy of plastics have been tightened in Japan and other countries, and research on various flame retardants has been actively conducted.

Decabromidiphenyl ether or brominated diphenyl ether containing it as the main component is a solid with a high bromine content and has a high thermal decomposition temperature, so it has extremely excellent performance as an additive flame retardant, especially for various plastics. It is already known that it is very useful as a flame retardant for polyolefins such as polyenalene, polypropylene, and polystyrene.

Method 5 for producing decabrominated diphenyl ether or brominated diphenyl ether containing it as the main component is as follows:
A method for brominating diphenyl ether in excess bromine,
Various production methods are known, such as a method in which diphenyl ether and bromine are reacted in fuming sulfuric acid, and a method in which diphenyl ether and bromine are reacted in an organic solvent such as dibromoethane, dichloroethane, or tetrachloroethane.

However, since decabromidiphenyl ether produced by these methods or brominated diphenyl ether containing decabrominated diphenyl ether as a main component includes bromine in its crystals during crystallization, its removal has been a problem. If bromine is included in crystal 15, when decabrominated diphenyl ether or brominated diphenyl ether containing it as the main component is added to various plastics and molded,
The encapsulated bromine is liberated, which pollutes the working environment and also causes corrosion of the molding machine and mold. The present inventors conducted various studies on methods for removing bromine included in the crystals, and as a result, it was found that bromine included in these crystals cannot be removed only by washing with an organic solvent, a reducing agent, or an aqueous solution of an inorganic base. First, it was found that it was necessary to dissolve, recrystallize, or pulverize the crystals.

Dissolving crystals and purifying them to remove bromine has been known as a recrystallization method using an organic solvent.

However, in this method, it is necessary to collect and purify the organic solvent used for recrystallization 30 times, some of the organic solvent used is brominated by bromine contained in the crystals, and This is not a preferred method because the bromine dissolved in the water causes corrosion of the equipment. When the crystals are crushed to remove the included bromine, it is necessary to finely crush the crystals by 35 mm. However, due to the limited crushing capacity, it is actually quite difficult to completely remove bromine by crushing alone, and countermeasures against equipment corrosion and exhaust gas caused by bromine liberated during crushing are required. The present inventors have conducted intensive studies to solve these problems, and as a result, the present inventors have discovered that bromine liberated during pulverization can be removed by performing wet pulverization in an aqueous solution of a reducing agent and/or an inorganic base when pulverizing crystals. The present invention was achieved by discovering that bromine can be immediately converted to bromide, and that bromine does not remain in the pulverized crystals when the pulverized particle size is reduced to a certain value or less without pulverization.

Therefore, the present invention involves wet grinding in an aqueous solution of a reducing agent and/or an inorganic base until the particle size becomes 100 microns or less when producing decaprom diphenyl ether or brominated diphenyl ether containing decaprom diphenyl ether as a main component. The present invention relates to a method for purifying brominated diphenyl ether characterized by the following. Decaprom diphenyl ether or brominated diphenyl ether containing it as the main component is added when molding various plastics to make them flame retardant, but from the viewpoint of the physical properties of the molded product, it is dispersed uniformly when mixed with plastics. , it is necessary to use finely divided decaprom diphenyl ether or brominated diphenyl ether containing it as a main component in order to dissolve it.

However, decaprom diphenyl ether produced by various production methods or obtained by recrystallization, or brominated diphenyl ether containing it as a main component, has a particle size of 200 microns or more, and is not practical as it is. However, it is necessary to further refine the particles, and pulverization is originally an essential operation. In addition, decaprom diphenyl ether produced by various production methods or brominated diphenyl ether containing this as the main component not only contains bromine in the crystal, but also has bromine attached to the crystal surface. ing. Conventionally, the bromine adhering to the surface of the crystal was removed by treating the wet crystal with an aqueous reducing agent solution, but in the present invention, this pretreatment can also be carried out at the same time as the crushing. Decaprom diphenyl ether produced by various production methods or brominated diphenyl ether containing it as a main component is separated from the reaction solution during production and then suspended in an aqueous solution of a reducing agent and/or an inorganic base. After that, it is wet milled until the particle size is less than 100 microns. After pulverization, solid-liquid separation is performed, followed by washing with water and drying to obtain a bromine-free product. As the reducing agent and inorganic base used in the present invention, all commonly known reducing agents and inorganic bases can be used, but as the reducing agent, sulfites and bisulfites such as sodium sulfite, potassium sulfite, and sodium hydrogen sulfite, thiosulfites, etc. As the thiosulfate such as sodium sulfate and the inorganic base, hydroxides of alkali and alkaline earth metals are particularly preferred. Bromine contained on the crystal surface and in the crystal is immediately rendered harmless by the following formulas (1) and (2), for example, when wet grinding is carried out in an aqueous sodium hydroxide solution. The detoxification of bromine during wet grinding in an aqueous solution containing sodium sulfite and sodium hydroxide is probably based on the following equations (3) and (4). Furthermore, since the reducing agent is often alkaline, it is thought that even when wet grinding is performed in an aqueous solution of the reducing agent, bromine is rendered harmless through reactions similar to equations (3) and (4). The amount of reducing agent and inorganic base to be used is 1 to 5 times the theoretical reaction amount, preferably 1.5 times the amount of bromine to be removed.
~3 times the amount.

If the amount is less than the stoichiometric amount, free bromine remains, so the effect of the present invention is not achieved, and if the amount is 5 times or more, it is not practical. Note that it is also possible to use the reducing agent and the inorganic base in an amount greater than the reaction equivalent, and to recycle the solution from which the crystals have been separated. The concentration of the reducing agent and inorganic base in the aqueous solution is 0.01-5%, preferably 0.0
It is 2-3%.

If the concentration of the reducing agent and inorganic base is less than 0.01%, the amount of liquid used will be large and the slurry concentration will be low, resulting in poor grinding efficiency, while if it is more than 5%, equipment corrosion and wastewater treatment problems may occur due to the chemicals used. , impractical. The slurry concentration during wet pulverization is 10 to 80%, preferably 20 to 60%.
It is.

If the concentration is less than 10%, the grinding efficiency is poor, and if it is more than 80%, the viscosity of the slurry liquid after grinding is high and the fluidity is low, which is not practical. In order to completely remove bromine included in the crystals according to the present invention, the particle size of the pulverized product must be 100 microns or less, preferably 50 microns or less.

If the particle size is 100 microns or more, there will still be 10p in the crushed crystal.
Bromine around pm is included. During the pulverization according to the present invention, it is also possible to use a dispersant such as a surfactant in order to increase the pulverization efficiency. After pulverization according to the present invention, decaprom diphenyl ether of 100 microns or less obtained by filtering, washing with water, and drying, or brominated diphenyl ether containing this as a main component, does not contain any bromine. Moreover, it is in no way inferior to products obtained by recrystallization using organic solvents.

As shown in Comparative Example 2, when simply wet-pulverizing in water, bromine still remains even if the particle size is reduced to 50 microns or less, and compared to this, the present invention You can understand the excellent effects of

This will be explained below using an example.

Example 1 100y of dry crystals of brominated diphenyl ether containing decaprom diphenyl ether as the main component containing 730ppm of bromine were placed in a mortar, and an aqueous solution 1007 containing 90m9 of sodium sulfite and 74η of sodium hydroxide dissolved therein was added. I put it in.

This mortar was placed in a box covered with a vinyl chloride sheet and thoroughly ground. Bromine in the air inside this box was measured during crushing, but no bromine was detected. Pour the obtained powder,
After washing with water and drying, a powder with a voltage of 99.5V was obtained.

This powder was sieved using a Tyler standard sieve to obtain a 325 mesh sieve size of 92.0y. ▲ No bromine was detected in the liquid or in the powder under the 325 mesh sieve. Comparative example
1 The same crystal 1007 used in Example 1 was crushed in a mortar in a box covered with a vinyl chloride sheet.

At this time, the bromine in the air inside the box was measured and found to be 10 ppm.
Bromine was detected at concentrations above. 3 of the powders obtained
100 ppm of bromine was detected under the 25 mesh sieve. Comparative Example 2 200 y of water was added to 100 y of the same crystals used in Example 1, placed in a mortar, and crushed in a box covered with a vinyl chloride sheet.

Almost no bromine was detected in the air inside the box during crushing. The obtained powder was filtered, washed with water and dried. 1 in the sap
30 ppm of bromine was detected, and 90 ppm of bromine was detected in the dry powder under the 325 mesh sieve. Example 2
~8 Wet crystals of brominated diphenyl ether containing 2760 ppm of bromine as a main component 1007 were treated with a reducing agent,
As a result of pulverization with different types and amounts of inorganic bases, the results shown in Table 1 were obtained.

In any case, no bromine was detected in the air inside the box or in the slough. In the case of Example 2, residual bromine was examined for 200 meshes.

Claims (1)

[Claims] 1. A method for purifying brominated diphenyl ether, which comprises wet-pulverizing decabrominated diphenyl ether or a brominated diphenyl ether containing it as a main component in an aqueous solution of a reducing agent and/or an inorganic base until the particle size becomes 100 microns or less.