WO2008071214A1

WO2008071214A1 - Production of tris (2,4,6-tribromophenoxy-1,3,5-triazine)

Info

Publication number: WO2008071214A1
Application number: PCT/EP2006/012052
Authority: WO
Inventors: Vincent Luc Mutterer; Patrice Luc Andres; Jennifer Klein
Original assignee: Albemarle Corp
Current assignee: Albemarle Corp
Priority date: 2006-12-14
Filing date: 2006-12-14
Publication date: 2008-06-19
Anticipated expiration: 2009-06-14

Abstract

Tris(2,4,6-tribromophenoxy)-1,3,5-triazine , an effective flame retardant, is prepared by an efficient, low cost process. The process comprises (A) forming a mixture from 2,4,6- tribromophenol, alkali metal carbonate, and acetone as the solvent, refluxing the mixture to form a first reaction product mixture, (B) feeding cyanuric chloride portionwise to first reaction product mixture and refluxing the resultant mixture to form a solids-containing second reaction product mixture; C) recovering solids from second reaction product mixture, washing the solids with acetone and then with hot water, and thereafter drying the washed product.

Description

PRODUCTION OF TRIS (2,4,6-TRIBROMOPHENOXY-I₅S₅S-TRIAZINE)

BACKGROUND

[0001] The compound, tris(2,4,6-tribromophenoxy)- 1 ,3,5-triazine, was reported in French Patent 1,566,675, in 1969. The compound is useful as a flame retardant. In fact, it is commercially available from Albemarle Corporation as SAYTEX 246 flame retardant. [0002] In U.S. Pat. Nos. 3,843,650 and 3,950,306 a process for the production of tris(2,4,6- tribromophenoxy)- 1 ,3,5-triazine is described. In addition, two recommended processes utilize the reaction of cyanuric chloride and 2,4,6-tribromophenol in the presence of either sodium carbonate and methyl ethyl ketone or aqueous sodium hydroxide and acetone. The product has poor solubility in ketone solvents and is readily removed by filtration. When sodium hydroxide is used as the base, water is formed as a by-product; sodium bicarbonate or carbon dioxide is formed when sodium carbonate is used. While workable, the foregoing processes are not as efficient as desired.

[0003] U.S. Pat. No. 5,965,731 describes a process in which tris(2,4,6-tribromophenoxy)- 1 ,3,5-triazine is prepared by brominating phenol with bromine in a aqueous reaction medium forming an aqueous hydrobromic acid phase and an organic phase consisting essentially of molten 2,4,6-tribromophenol. The aqueous hydrobromic acid phase and the molten 2,4,6- tribromophenol are separated from each other, and optionally the molten 2,4,6-tribromophenol is washed with an aqueous decolorizing solution. An alkali metal base and water are mixed with the 2,4,6-tribromophenol to form an alkali metal salt of tribromophenol. Then, in a mixture consisting essentially of water and at least one liquid ketone, cyanuric chloride is reacted with at least a portion of the alkali metal 2,4,6-tribromophenolate such that tris(2,4,6- tribromophenoxy)-l,3,5-triazine is produced.

[0004] It would be of advantage to the art if a way could be found for producing tris(2,4,6- tribromophenoxy)-l,3,5-triazine more efficiently and at lower cost.

BRIEF SUMMARY OF THE INVENTION

[0005] This invention is deemed to provide an efficient low cost way of producing tris(2,4,6-tribromophenoxy)-l,3,5-triazine.

[0006] A process for the production of tris(2,4,6-tribromophenoxy)-l,3,5-triazine, which process comprises: A) forming a mixture by bringing together 2,4,6-tribromophenol, alkali metal carbonate, and acetone as the solvent, refluxing the mixture to form a first reaction product mixture, and cooling first reaction product mixture and/or allowing first reaction product mixture to cool, to a temperature below about 25⁰C;

B) feeding cyanuric chloride portionwise to first reaction product mixture, which has been cooled or has been allowed to cool, and refluxing the resultant mixture to form a solids-containing second reaction product mixture;

C) recovering solids from second reaction product mixture, washing recovered solids with acetone and then with hot water, and thereafter drying the washed product.

The acetone used in step A) should be substantially anhydrous, i.e., it should contain less than 2000 ppm of water. The use of such "dry" acetone enables recovery and recycle of "dry" acetone in the process, requiring only a simple evaporation or distillation of the acetone from the second reaction product mixture prior to the hot water wash. It will also be noted that the work-up procedure is very simple and efficient, especially since only a single organic solvent is used in the process. [0007] When the process was conducted on a laboratory scale, the suitably dried product in the form of a white powder was shown to assay 99.5% (area %) purity by HPLC, and to have a melting point of 229.8°C by DSC.

[0008] Another advantage of the present invention is that the process can be conducted as a "one pot" process. Thus, a preferred embodiment of this invention is a process as above wherein A) and B) are conducted in the same reaction vessel without removal of the first reaction product mixture from that vessel.

[0009] The above and other embodiments and features of this invention will be still further apparent from the ensuing description and appended claims.

FURTHER DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Step A)

[0010] The reactants in A) above can be brought together in any sequence in a suitable reactor. A sufficient amount of acetone should be present to form a liquid phase which enables the reaction mixture to be refluxed. For best results, the 2,4,6-tribromophenol used should assay greater than 99% purity and the alkali metal carbonate should be of anhydrous grade. The amount of alkali metal carbonate should be in excess relative to the amount of

2,4,6-tribromophenol fed to the reaction mixture. In this reaction only one mole of alkali metal of the alkali metal carbonate participates in the reaction despite the fact that one mole of alkali metal carbonate contains two moles of alkali metal. Thus, the mole ratio of alkali metal carbonate:tribromophenol is typically in the range of about 1.01:1 to about 1.05:1. While any alkali metal can be used, use of high purity sodium carbonate is preferred and use of high purity potassium carbonate is even more preferred because of its efficiency in the reaction and relatively low cost. The duration of the refluxing in Step A can be varied and is dependent, to some extent, upon the scale of operation. On a laboratory scale, a period in the range of about 1 to about 2 hours is usually sufficient to achieve substantially complete reaction. Longer or shorter periods can be used if deemed necessary or desirable and are within the scope of this invention. After refluxing the reaction mixture can be cooled to below about 25 ° C and typically to about room temperature by standard means such as use of coolant in a jacketed reactor, etc. Alternatively, the reaction mixture can be allowed to stand for a sufficient period to reach a temperature below about 25⁰C or room temperature, as desired. [0011] Preferably, in addition to using anhydrous alkali metal carbonate, the water content of the acetone solution of 2,4,6-tribromophenol should be below 4000 ppm, with the lower the amount of water present, the better. In other words, it is preferred that the total water content of the reaction mixture in A) is 4000 ppm or less. Such low levels of water minimize the extent to which cyanuric chloride is hydrolyzed in Step B) and this in turn enables formation of high purity tris(2,4,6-tribromophenoxy)-l,3,5-triazine.

Step B)

[0012] Cyanuric chloride is brought into contact with reaction product mixture from A) when such product mixture is at a temperature below about 25⁰C and typically at about room temperature (or below, if desired). Preferably, the cyanuric chloride is simply added portionwise to the reaction product mixture in A), as this enables the reaction to be carried out as a "one pot" process. However, the addition can take place in a different reactor if desired. The addition should be portionwise, i.e., slow enough as not to result in excessive local heat evolution with splattering or the like. The rate and duration of the portionwise feed of cyanuric chloride will vary, depending for example upon the scale of operation. Thus, in any case where a feed rate has not been previously established, a few trial experiments can be utilized in order to develop a suitable rate of feed of the cyanuric chloride to the reaction product mixture of A). The Example given herein will serve as a useful guide on this matter of feed rate and time. Upon completion of the feed, the reaction mixture is refluxed for a sufficient period to achieve a desirable yield of the tris(2,4,6-tribromophenoxy)- 1 ,3,5-triazine. During the refluxing, solids will form in the acetone medium and this tends to serve as an indication of the extent of reaction that is occuring. Typically, a reflux period in the range of about 2 to about 4 hours will suffice. However, departures from this range can be utilized whenever deemed necessary or appropriate and thus are within the scope of this invention.

Step C [0013] This step involves recovering solids from the second product reaction mixture which is formed in B). Any suitable solids/liquid physical separation procedure can be used. Preferably, the reaction product mixture is subjected to centrifugation or filtration. The resultant cake formed by such procedure is then washed with fresh high purity, substantially anhydrous acetone (e.g., less than 2000 ppm of water). The acetone used in the wash should be recovered for recycle after purification, if necessary. After acetone washing the cake is then washed with hot water, e.g., in the range of about 40 to about 90⁰C and preferably in the range of about 40 to about 60⁰C. Temperatures of 45°C ± 3°C are more preferred. The product is then dried, preferably under vacuum at an elevated temperature in the range of about 40 to about 100⁰C. [0014] The following example illustrates the practice and advantages of this invention. It is not intended that this invention be limited to only the specific details given in the example.

EXAMPLE

[0015] To a reactor is charged 2,4,6-tribromophenol (75 g; 0.2267 mol; 1 eq.) preferably with an assay of > 99%. To this is added acetone (100 g) preferably of analytical quantity (< 2000 ppm water). Anhydrous potassium carbonate is then added (32 g; 0.2315 mol; 1.02 eq).

The resultant mixture is heated to reflux and kept under reflux for 1.5 hours. The reaction mixture is then cooled down to 25°C. Cyanuric chloride is then added (13.5 g; 0.0732 mol; 0.32 eq). The cyanuric chloride preferably has a purity > 99.5%. The addition is effected by adding the cyanuric chloride in ten portions over a period of 15 minutes. The resultant mixture is heated to reflux and kept under reflux for 3 hours. After cooling down to 35⁰C, the reaction product mixture is filtered. The wet cake from the filtration is washed with acetone (72 g) preferably of analytical quality (< 2000 ppm water) at room temperature. Then, the wet cake is washed with hot water at 45⁰C (72 g). The product was then dried under vacuum at 90⁰C. In a laboratory run conducted as above, the final product, tris(2,4,6- tribromophenoxy)-l,3,5-triazine, is isolated as a white powder (66 g; 0.0618 mol) in a yield of 82%. The assay by HPLC is 99.5 area % and the melting point is 229.8°C by DSC. [0016] A further advantage of the invention is that 2,4,6-tribromophenol starting material of high purity can be prepared readily and economically. For example, 2,4,6-tribromophenol with an assay of > 99.9 area % by GC was readily prepared from phenol and 1.06 eq. of bromine in water. The resultant high purity product can be used as formed after a simple phase cut to recover the product from the water and after drying the recovered product in any suitable manner.

[0017] Components referred to by chemical name or formula anywhere in the specification or claims hereof, whether referred to in the singular or plural, are identified as they exist prior to coming into contact with another substance referred to by chemical name or chemical type

(e.g., another component, a solvent, or etc.). It matters not what chemical changes, transformations and/or reactions, if any, take place in the resulting mixture or solution as such changes, transformations, and/or reactions are the natural result of bringing the specified components together under the conditions called for pursuant to this disclosure. Thus the components are identified as ingredients to be brought together in connection with performing a desired operation or in forming a desired composition. Also, even though the claims hereinafter may refer to substances, components and/or ingredients in the present tense ("comprises", "is", etc.), the reference is to the substance, component or ingredient as it existed at the time just before it was first contacted, blended or mixed with one or more other substances, components and/or ingredients in accordance with the present disclosure. The fact that a substance, component or ingredient may have lost its original identity through a chemical reaction or transformation during the course of contacting, blending or mixing operations, if conducted in accordance with this disclosure and with ordinary skill of a chemist, is thus of no practical concern. [0018] Except as may be expressly otherwise indicated, the article "a" or "an" if and as used herein is not intended to limit, and should not be construed as limiting, a claim to a single element to which the article refers. Rather, the article "a" or "an" if and as used herein is intended to cover one or more such elements, unless the text expressly indicates otherwise. [0019] Each and every patent or publication referred to in any portion of this specification is incorporated in toto into this disclosure by reference, as if fully set forth herein. [0020] This invention is susceptible to considerable variation in its practice. Therefore the foregoing description is not intended to limit, and should not be construed as limiting, the invention to the particular exemplifications presented hereinabove.

Claims

CLAIMS:

1. A process for the production of tris(2,4,6-tribromophenoxy)-l,3_>5-triazine, which process comprises:

A) forming a mixture by bringing together 2,4,6-tribromophenol, alkali metal carbonate, and acetone as the solvent, refluxing the mixture to form a first reaction product mixture, and cooling first reaction product mixture and/or allowing first reaction product mixture to cool, to a temperature below about 25° C;

B) feeding cyanuric chloride portion wise to first product reaction mixture which has been cooled or has been allowed to cool, to form a solids-containing second reaction product mixture;

2. A process as in Claim 1 wherein A) and B) are conducted in the same reaction vessel without removal of the first reaction product mixture from said vessel.

3. A process as in Claim 1 wherein the alkali metal carbonate used in A) is anhydrous and the water content of the acetone solution of 2,4,6-tribromophenol is below 4000 ppm.

4. A process as in Claim 1 wherein the acetone used in the process has a water content below 2000 ppm wt/wt.

5. A process as in Claim 1 further comprising cooling solids-containing second reaction product mixture of B) and/or allowing solids-containing second reaction product mixture of B) to cool, to a temperature below about 35° C before conducting C).

6. A process as in Claim 1 wherein in C), the solids are recovered by filtration or centrifugation to form a wet cake, which is then washed with acetone and then with hot water.

7. A process as in Claim 1 wherein the acetone used in the process has a water content below 2000 ppm wt/wt, wherein A) and B) are conducted in the same reaction vessel without removal of the first reaction product mixture from said vessel, and wherein in C), the solids are recovered by filtration or centrifugation to form a wet cake, which is then washed with acetone and then with hot water.

8. A process as in any of Claims 1-7 wherein the alkali metal carbonate used is anhydrous potassium carbonate.