JPS6210035A - Method of keeping imperfectly brominated product obtained assolution in form of perbrominated product - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the maintenance of incompletely brominated products, particularly brominated derivatives of diphenyl ether, in the form of perbrominated products.

"Perbrominated" and "underbrominated" products are used herein to refer to products that are fully or partially substituted with bromine, respectively, particularly in the case of diphenyl ether, while indicates decabromodiphenyl ether and, on the other hand, diphenyl ether containing up to 9 bromine atoms per molecule.

In general, processes for the preparation of perbrominated or underbrominated products involve not only the desired product in the above sense, but also the desired underbrominated or underbrominated product. Solutions containing either or mixtures thereof are also produced.

Simply removing these solutions represents a loss of 20% or more of the incompletely brominated product. Consequently, this loss can usually be limited by recycling this solution containing the incompletely brominated product into the reaction medium. However, these recirculation operations cannot be repeated many times, as they result in a deterioration of the quality, especially the color, of the fresh product.

The present invention provides a method for stabilizing underbrominated products in solution by converting the underbrominated products into perbrominated products starting from solution without prior isolation.

The method includes the following steps. a) stepwise addition of a brominating agent into a solution of an incompletely brominated product containing a brominating catalyst;

b) heating the medium to the reflux temperature of the solvent and maintaining this temperature until the perbromination reaction is complete.

C) Drying the obtained perbrominated product.

The method according to the invention is applicable to the treatment of large quantities of incompletely brominated solutions. The invention is also particularly suitable for the treatment of solutions of aromatic compounds, especially diphenyl, terphenylene/L/, benzene, toluene, xylene, naphthalene, phenol, polyphenyl, polyphenylene oxide and especially diphenyl ether or diphenyl oxide.

In solutions treated by the method of the invention, such compounds contain at least one bromine substituent. Particularly in the case of diaromatic ring compounds (especially diphenyl or diphenyl ether), the method is particularly applicable to solutions containing compounds containing 04 to 9 bromine atoms per molecule.

In the method according to the invention, the starting solution comprises the incompletely brominated compound described above and a solvent. It is generally advantageous to choose the solvent from halogenated hydrocarbons. Among the halogenated hydrocarbons, hydrocarbons containing one carbon atom substituted by bromine and/or chlorine are recommended, preferably methylene bromide. Naturally, it does not depart from the scope of the invention to apply the method to solutions containing other types of solvents. The concentration of the solution is such that a range of 3 to 10 moles of solvent is used per mole of partially brominated compound to be treated. Furthermore, this relationship is particularly recommended when processing partially brominated aromatic compound solutions. Therefore,
If the starting solutions do not exhibit the recommended concentrations above, they can be added by adding a solvent, preferably selected from the solvents above, provided they are miscible with the initial solution, or by adding partially brominated compounds, if appropriate unbrominated. It may be desirable to correct this concentration depending on the situation by adding a chemical compound.

The brominating agent can be chosen from the known products in this type of reaction. Advantageously, the brominating agent is bromine itself. The brominating agent is preferably used in molar excess (calculated on the basis of bromine relative to the stoichiometric amount in the perbromination reaction of the compound to be treated). This molar excess amounts to 10%, preferably in the range from 3 to 8%, relative to the stoichiometric amount of the compound to be perbrominated. The addition of the brominating agent may be carried out continuously or periodically. Generally, this operation lasts from 1 to 10 hours.

A variety of bromination catalysts are known and used in this process. This is particularly discussed in U.S. Pat. No. 4,287.3.
Reference may be made to No. 73.

Certain metals can be used in the catalyst, such as aluminum halides, especially aluminum chloride (AlCl2) and aluminum bromide (AlBr3).
Advantageously, it is selected from compounds selected from the group comprising.

The catalyst may be in the form of particles or blocks. Its size or particle size distribution is generally not critical.

Purely as a matter of knowledge, a size in the range 0.05 to 15 mm can be chosen. When using a nonmetallic catalyst, one with an amorphous or crystalline structure can be used. From about 2 to about 20 mole percent catalyst is used per mole of compound to be perbrominated.

Optionally, the catalyst is dispersed and dissolved in the solution of the underbrominated product.

After mixing the reactants and the catalyst (step a>I, the next step of the method is to raise the temperature of the medium to the reflux temperature of the solvent and maintain the medium at this temperature until the perbromination reaction is completed. Including.

The temperature obviously depends on the solvent used. In the case of methylene bromide, when operating at atmospheric pressure, this temperature is between 95 and 9
The value is in the range of 9°C. The reaction time, ie the achievement of complete reaction, depends on its nature and degree of bromination of the initial incompletely brominated product and other operating conditions (catalyst, brominating agent). Generally, the reaction is complete in 30 minutes to 2 hours. These values are presented as a guide only.

At the end of the reaction, the perbrominated product obtained after cooling to a temperature in the range from 20 to 50 DEG C. is dried.

The drying is generally carried out at temperatures ranging from 50 DEG to 250 DEG C., the exact value of which depends on the nature of the product and solvent produced and the drying conditions (air or partially evacuated ventilated oven, etc.). The drying operation is advantageously carried out by purification of the reaction medium and liquid/solid separation.

The purification operation essentially involves deactivation of the catalyst, for example by addition of water or by addition of acidified water.

If necessary, this operation is followed, for example, by decomposition of the residual brominating agent (in particular Br2) with +J um metabisulfite or hydrazine. It is then appropriate to separate and remove the supernatant aqueous phase containing the catalyst. By washing the organic phase, especially with water and dehydrating, the perbrominated compound can be recovered, which compound is then combined with a solvent and further dried as described above.

The process according to the invention is particularly advantageous over conventional bromination reactions which produce solutions containing significant amounts of incompletely brominated products. In fact, this method makes it possible to stabilize the products without their decomposition by converting underbrominated products into easily isolated perbrominated products. The process according to the invention is also particularly suitable for the maintenance of incompletely brominated diphenyl ethers obtained in particular during the preparation of octabromodiphenyl ether in the form of notecabromodiphenyl ether. In this process, a degree of conversion (weight percent of the initial incompletely brominated product subjected to the bromination reaction) of greater than 95% was obtained. That is, the molar yield of decabromodiphenyl ether relative to the initial incompletely brominated diphenyl ether is often greater than 93% or greater than 95%, even taking into account the product remaining in solution.

The invention will be explained in the following examples.

Example 1 The following materials are added to a stirring reactor at room temperature (25°C). That is, - incompletely brominated diphenyl ether (average degree of bromination 7.
1.250Kg of 24.5% by weight methylene bromide solution of 4)
.

・40.1Kg of diphenyl ether and ・20Kg
of aluminum chloride.

580 Kg of bromine is injected over a period of 2 hours at a temperature ranging from 20°C (start of addition) to 50°C (end of addition).

The reaction mixture is then heated to the boiling point of methylene bromide and maintained for 1 hour.

After cooling to 40°C, water is added to deactivate the catalyst.

Excess bromine is then destroyed using an aqueous hydrazine solution. After removing the supernatant aqueous phase, the organic solution containing decabromodiphenyl ether in a dispersed state is washed with water four or more times.

The aqueous phase is removed after each wash.

After filtration, washing and draining of the organic phase, the following materials are recovered: That is, perbrominated diphenyl ether A containing impregnating solvent and bromated methyleno solution B0 containing only 2.6% by weight of incompletely brominated diphenyl ether Impregnated solid A was dried to obtain 578 kg of perbrominated diphenyl ether.

Example 2 140 g of bromine is injected into a reactor containing the following materials over a period of 1 hour at room temperature with stirring. 480 g of a solution of 40% by weight of incompletely brominated diphenyl ether (average degree of bromination 6.93'') in methylene bromide and 10 g of aluminum chloride.

After heating the reaction medium to 98° C. and maintaining it at boiling temperature for 1 hour and 30 minutes, purification operations are carried out as in Example 1 (catalyst deactivation, removal of unreacted bromine, etc.).

After filtration, washing and dehydration the following material is obtained. Impregnated solid A1 yielding 239.3 g of perbrominated diphenyl ether after drying

Claims (14)

[Claims] (1) A method for stabilizing an incompletely brominated product in solution by converting it to a perbrominated product in solution without prior isolation of the incompletely brominated product, comprising: a) bromine; b) heating the medium to the reflux temperature of the solvent and maintaining it at that temperature until the perbromination reaction is complete; and c) drying the perbrominated product obtained. (2) A method according to claim 1, characterized in that the incompletely brominated product to be treated is an incompletely brominated aromatic compound. (3) The incompletely brominated product to be treated comprises a diphenyl ether having 4 to 9 bromine atoms per molecule. Method described. (4) The method according to any one of claims 1 to 3, wherein the brominating agent is bromine. (5) The method according to any one of claims 1 to 4, wherein the bromination catalyst is an aluminum halide selected from the group including aluminum chloride and aluminum bromide. (6) The method according to any one of claims 1 to 5, wherein the organic solvent is a halogenated hydrocarbon. (7) The method according to claim 6, wherein the solvent is methylene bromide. (8) Before drying the perbrominated product, the step ￥b
The method according to any one of claims 1 to 7, characterized in that the reaction medium obtained is purified at the end of the process. (9) The method according to claim 8, which includes separating and removing a supernatant water phase after the purification operation. (10) The method according to claim 9, characterized in that the organic phase obtained during the phase separation is washed and dried. (11) the brominating agent is calculated based on bromine, and
5. Process according to claim 1, characterized in that a molar excess of the stoichiometric amount required for perbromination of the incompletely brominated compound to be treated is used. (12) The excess molar amount is 10% or less, preferably 3 to
Claim 1 characterized in that the range is 8%.
The method described in Section 1. (13) The concentration of the solution to be treated is determined such that a range of 3 to 10 moles of solvent is used per mole of the incompletely brominated compound to be treated. , 6 and 7. (14) Compound 1 to be perbrominated using the bromination catalyst
6. Process according to claim 1, characterized in that it is used in a proportion ranging from 2 to 20 mol% per mole.