WO2008027777A1

WO2008027777A1 - Preparation of high assay decabromodiphenyl oxide

Info

Publication number: WO2008027777A1
Application number: PCT/US2007/076602
Authority: WO
Inventors: Saadat Hussain
Original assignee: Albemarle Corporation
Priority date: 2006-08-29
Filing date: 2007-08-23
Publication date: 2008-03-06
Also published as: TW200815331A

Abstract

A process for producing reaction-derived decabromodiphenyl oxide product of high purity is described. Diphenyl oxide and/or lightly brominated diphenyl oxide is brominated in excess refluxing bromine and, optionally, a catalytic quantity of Lewis acid bromination catalyst to form a first reaction mixture of bromine, and an intermediate brominated diphenyl oxide product having an average of about 2-8 bromine atoms per molecule. This intermediate is recovered as a solid and used as feed in a second bromination conducted in excess refluxing bromine and in the presence of a catalytic amount of a Lewis acid bromination catalyst, e.g., AlCl3 or AlBr3. In this second bromination, hydrogen bromide coproduct is removed from the reaction zone in a sufficient amount to form a reaction-derived decabromodiphenyl oxide product of high purity.

Description

PREPARATION OF HIGH ASSAY DECABROMODIPHENYL OXIDE

TECHNICAL FIELD

[0001] This invention relates to the preparation of high assay decabromodiphenyl oxide products.

BACKGROUND [0002] Decabromodiphenyl oxide (DBDPO) is a time-proven flame retardant for use in many flammable macromolecular materials, e.g. thermoplastics, thermosets, cellulosic materials and back coating applications.

[0003] DBDPO is presently sold as a powder derived from the bromination of diphenyl oxide (DPO) or a partially brominated DPO containing an average of about 0.7 bromine atom per molecule of DPO. Such bromination is conducted in excess bromine and in the presence of a bromination catalyst, usually AlCl₃. The operation is typically conducted at 177 ° F (ca. 80.5 °C) with a 2-3 hour feed time. The powdered products are not 100% DBDPO, but rather are mixtures that contain up to about 98% DBDPO and about 1.5%, or a little more, of nonabromodiphenyl oxide co-product. As a partially brominated product, this amount of nonabromodiphenyl oxide is considered problematic by some environmental entities.

[0004] It would therefore be desirable to provide process technology enabling preparation of DBDPO products of higher purity, such as products comprising (A) at least 99% of DBDPO and (B) nonabromodiphenyl oxide in an amount not exceeding 0.5%, preferably not exceeding 0.3%, and still more preferably, not exceeding about 0.1%. It would be especially desirable if such technology could produce DPDPO products comprising (A) at least 99.5% of DBDPO and (B) nonabromodiphenyl oxide in an amount not exceeding 0.5%, preferably not exceeding 0.3%, and still more preferably, not exceeding about 0.1%. [0005] On the basis of studies conducted in our laboratories, one of the prime difficulties in producing high purity DBDPO is the existence of an equilibrium between nonabromodiphenyl oxide and decabromodiphenyl oxide. This equilibrium can be depicted as follows:

Br₉-DPO + Br₂ ^ Br₁₀-DPO + HBr

As more fully described in commonly-owned copending U.S. Application No. 60/823,811, filed on August 29, 2006, and entitled "Preparation of High-Assay Decabromodiphenyl Oxide", prolonged feed of DPO and/or partially brominated DPO to refluxing bromine while substantially concurrently reducing hydrogen bromide content in the reactor enables a shift to the right in this equilibrium so that the amount of nonabromodiphenyl oxide is diminished and more of the desired decabromodiphenyl oxide forms and precipitates with less nonabromodiphenyl oxide being coprecipitated within the decabromodiphenyl oxide particles. It is also believed that if the DPO and/or partially brominated DPO is fed too rapidly, the precipitation of at least one Br₉-DPO isomer occurs so rapidly that the above equilibrium is not totally reached. Pursuant to this invention, the processing described herein is deemed to avoid these difficulties.

BRIEF SUMMARY OF THE INVENTION

[0006] Pursuant to this invention, high purity decabromodiphenyl oxide products are directly produced without recourse to recrystallization or chromatographic purification steps or any other subsequent procedure to remove or that removes nonabromodiphenyl oxide from decabromodiphenyl oxide.

[0007] Among the embodiments of this invention is a process for producing a reaction- derived decabromodiphenyl oxide product of high purity, which process comprises: a) brominating diphenyl oxide and/or lightly brominated diphenyl oxide in a reaction mixture containing an excess of refluxing bromine and, optionally, a catalytic quantity of Lewis acid bromination catalyst to form a first reaction mixture which comprises bromine, and an intermediate brominated diphenyl oxide product having an average in the range of about 2 to about 8 bromine atoms per molecule; b) recovering intermediate brominated diphenyl oxide product formed in a); and c) feeding intermediate brominated diphenyl oxide product recovered in b) into a reaction zone containing a refluxing second reaction mixture comprising (i) an excess of bromine and (ii) a catalytic quantity of Lewis acid bromination catalyst, and concurrently removing hydrogen bromide coproduct from the reaction zone in a sufficient amount to form a reaction-derived decabromodiphenyl oxide product of high purity. The reaction mixture in a) can contain Lewis acid bromination catalyst or it can be devoid of

Lewis acid bromination catalyst. If the reaction mixture in a) contains a Lewis acid bromination catalyst the catalytic quantity used will typically be less than the catalytic quantity used in c).

[0008] It will of course be understood and appreciated that the terms "first" and "second" as applied to the above reaction mixtures is merely to distinguish one from the other. In an actual plant operation for the practice of this invention, there may be several reaction mixtures being produced in the operation, the first of which, for example, could be a reaction in which diphenyl oxide or bromine is produced. Thus, the terms "first" and "second" do not constitute a sequential arrangement of reaction mixtures in an operation in a plant facility conducting a process of this invention. [0009] For convenience, in the following description the term "intermediate product" is substituted for the term "intermediate brominated diphenyl oxide product". [0010] Typically, after completing the bromination in a), the first reaction mixture comprises a liquid phase containing solid particles. In other words, at least a portion of the intermediate product in a) is in the form of solids . In a preferred embodiment of this invention such solids are recovered in b) in the form of solids. Typical solids/liquid separation procedures such as filtration, centrifugation or decantation are used for effecting such recovery. Since the solids recovered in this manner are free or essentially free of hydrogen bromide coproduct, such solids are then used in c) as feed to a second reaction mixture in order to produce reaction-derived decabromodiphenyl oxide product of high purity. Only a fraction of the total hydrogen bromide formed on proceeding from diphenyl oxide and/or lightly brominated diphenyl oxide to decabromodiphenyl oxide is liberated in c) and thus the effect of the equilibrium referred to above is greatly minimized. Consequently, reaction- derived decabromodiphenyl oxide product of high purity can be formed more readily. [0011] Although the solids recovered in b) can be fed as solids in conducting c), in another preferred embodiment solids recovered in b) are fed in c) as a solution or slurry in fresh bromine. Alternatively, solids recovered in b) can be fed as a solution in an appropriate organic solvent such as dibromomethane whereby the bromination in c) is conducted in the presence of such solvent. [0012] Still another preferred embodiment is a process as described above wherein at least a portion of intermediate product in a) is in the form of solids and wherein in b) such solids are recovered from such intermediate product by centrifugation, filtration or decantation and such solids are fed in c) as a solution or slurry in fresh bromine, and wherein at least a portion of the liquid phase from the centrifugation, filtration or decantation is recycled to the bromination in a). The liquid phase from the centrifugation, filtration or decantation comprises liquid bromine which may contain some dissolved lower brominated diphenyl oxide species.

[0013] As can be seen from the above, in addition to enabling formation of reaction-derived decabromodiphenyl oxide product of high purity, the processes of this invention form an intermediate product, typically in solid form, which product is free or at least essentially free from coproduct hydrogen bromide which avoids problems associated with the existence of the chemical equilibrium referred to above, an equilibrium which greatly influences the purity of the decabromodiphenyl oxide product formed. In addition, the process technology of this invention makes it possible to avoid use of water in the product work-up and recovery stages. This in turn (1) permits the intermediate product in the form of solids to be used as feed in c) without need for drying the product, and (2) permits the liquid phase from the separation in b), viz. , liquid bromine which may contain some dissolved lower brominated diphenyl oxide species, to be recycled for use in the bromination in a) without need for drying such liquid phase before recycle.

[0014] 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

[0015] It can be seen from the above that in the processes of this invention diphenyl oxide and/or lightly brominated diphenyl oxide is brominated in a reaction mixture containing an excess of refluxing bromine and, optionally, Lewis acid bromination catalyst, to form an intermediate product having an average in the range of about 2 to about 8 bromine atoms per molecule. Intermediate product is recovered and fed into a reaction zone containing a reaction mixture comprising an excess of refluxing bromine and Lewis acid bromination catalyst while removing hydrogen bromide coproduct from the reaction zone to form reaction-derived decabromodiphenyl oxide product of high purity. The amount of excess bromine in the reaction zone is preferably in the range of about 50 to about 150 mole percent more than the amount theoretically required to perbrominate the feed of intermediate product.

[0016] As used herein including the claims:

1) The term "lightly brominated" means monobrominated diphenyl oxide or a mixture of brominated diphenyl oxides having an average of less than two bromine atoms per molecule. 2) The term "reaction-derived" means that the composition of the product is reaction determined and not the result of use of downstream purification techniques, such as recrystallization or chromatography, or like procedures that can affect the chemical composition of the product. Adding water or an aqueous base such as sodium hydroxide to the reaction mixture to inactivate the catalyst, and washing away of non-chemically bound impurities by use of aqueous washes such as with water or dilute aqueous bases are not excluded by the term "reaction-derived". In other words, the products are directly produced in the synthesis process without use of any subsequent procedure to remove or that removes nonabromodiphenyl oxide from decabromodiphenyl oxide. 3) The term "high purity" means that the reaction-derived DBDPO product comprises more than 99% of DBDPO and nonabromodiphenyl oxide in an amount of less than 1 % with, if any, a trace of octabromodiphenyl oxide. Preferably the process forms a reaction-derived product which comprises (i) at least 99.5% of DBDPO and (ii) nonabromodiphenyl oxide in an amount not exceeding 0.5%, preferably not exceeding 0.3%, and still more preferably, not exceeding about 0.1%. 4) The term "concurrently" means that hydrogen bromide is removed at about the same time the feeding of diphenyl oxide and/or lightly brominated diphenyl oxide is taking place. However, the feeding and the removal need not start at precisely the same moment in time, nor must they cease at the same moment in time. For example, the feeding and the removal of hydrogen bromide need not start at the same moment in time as there can be a time lag between the commencement of the feed and the evolution of enough hydrogen bromide to initiate the removal thereof from the reactor. Likewise, if and when the feeding is terminated, there can be a period of time thereafter during which the amount of hydrogen bromide in the reactor can be removed. In addition, it should be understood that the term "concurrently removing" includes one or more interruptions in the removal of hydrogen bromide as long as such interruptions are of short enough duration as not to affect in any significant way the end result of producing a reaction-derived product of high purity.

[0017] For the purposes of this invention, unless otherwise indicated, the % values given for DBDPO and nonabromodiphenyl oxide are to be understood as being the area % values that are derived from gas chromatography analysis. A procedure for conducting such analyses is presented hereinafter.

Bromination in a)

[0018] The bromination process in a) can be conducted either as a batch process or as a continuous process. In general, the duration of the feeding period in a batch process is inversely related to the temperature at which the refluxing is occurring. In other words, the higher the temperature, the shorter can be the feed time. When operating as a continuous process, the duration of the average residence time in the reactor is inversely related to the temperature at which the refluxing is occurring. Also, desirably, in a continuous process the rate of feed to the reactor and the rate of removal of the first reaction mixture from the reactor in a continuous process should be maintained such that the quantity of reaction mixture within the reactor remains substantially constant. [0019] The bromination reaction in a) can be conducted in the presence or absence of a catalyst. If a catalyst is used in a) it is important that the reaction proceeds to form an intermediate product having a number or an average number in the range of about 2 to about 8, preferably in the range of about 4 to about 6, and more preferably in the range of about 5 to about 6 bromine atoms per molecule. When conducting the reaction of a) in the absence of a catalyst and at reflux temperatures in the range of about 57 to about 60° C, an intermediate product having an average of about 4 bromine atoms is typically formed. [0020] It will be understood that depending upon the extent of bromination, the intermediate product formed in a) can contain some unbrominated DPO and/or some brominated DPO having one bromine atom in the molecule. It will also be understood that the intermediate product formed in a) can be composed entirely or substantially entirely of reaction product having the same number of bromine atoms per molecule in the range of about 2 to about 8, preferably in the range of about 4 to about 6, and more preferably in the range of about 5 to about 6 bromine atoms per molecule. Typically, however, the intermediate product formed in a) will contain a mixture of brominated DPO species (possibly including DPO itself) having an average number of bromine atoms per molecule in one of the ranges just described. [0021] The composition of the intermediate product formed in a) can be affected by catalyst strength (if used), catalyst concentration (if catalyst is used), reaction temperature, the pressure under which the reaction is conducted, and the duration of the bromination (in a batch operation) or the average residence time in the reactor (in a continuous operation). [0022] As noted above, a) can be conducted in the absence of any added catalyst, or a suitable Lewis acid bromination catalyst can be used. Such catalysts include strong Lewis acid catalysts, notably aluminum chloride, aluminum bromide, ferric chloride, ferric bromide, gallium chloride, gallium bromide, aluminum foil or powder or iron powder when using reaction conditions that enable formation of intermediate product having a number or an average number of bromine atoms in one of the ranges described above. Alternatively, other less strong Lewis acid catalysts such as zinc chloride, zinc bromide, titanium tetrachloride, titanium tetrachloride, zirconium tetrachloride, zirconium tetrabromide, antimony chloride, antimony bromide, or other such Lewis acid catalyst can be used.

[0023] When a catalyst is used, it should be used in a catalytic quantity sufficient to produce under the reaction conditions being used, an intermediate product having a number or average number of bromine atoms per molecule in the ranges described above. Generally speaking, such amount will typically fall within the range of about 2 to about 6 wt % based on the weight of the DPO used.

[0024] In the absence of a catalyst, the reaction temperature used in a) is generally in the range of about 20 to about 60 ° C. When a catalyst is used the temperature should be somewhat less than used in the absence of a catalyst, e.g., in the range of about 15 to about

55 °C.

[0025] Increased reaction pressure tends to increase the extent of bromination. Nevertheless, pursuant to this invention, it is possible to operate in a) at atmospheric, subatmospheric and/or superatmo spheric pressures in the range of about 1 to about 50 psig (ca. 1.08xl0⁵ to 4.46xO⁵ Pa). However, the pressure in a) is preferably no more than autogenous pressure in a closed reaction system.

[0026] The reaction period or average residence time used in conducting a) above can vary. Generally speaking, the longer the reaction period or average residence time in a), the greater will be the extent of bromination. Thus, the reaction period or average residence time should be selected as to produce an intermediate product having a number or average number of bromine atoms per molecule in one of the ranges described above. Generally speaking, as long as the desired intermediate product is formed, the shorter the reaction period or residence time, the better. Accordingly, the reaction period or average residence times in a) are typically in the range of about 15 to about 90 minutes and preferably in the range of about 30 to about 45 minutes.

[0027] If desired, a co- solvent can be used in the bromination in a). Such co- solvent is preferably methylene dibromide, but other suitable brominated solvents can be employed.

[0028] The bromination in a) can be conducted in various ways. Thus, the DPO and/or lightly brominated DPO can be fed to bromine already present in the reactor, or the bromine can be fed to the DPO and/or lightly brominated DPO already present in the reactor. Alternatively, (i) the DPO and/or lightly brominated DPO and (ii) the bromine can be fed substantially concurrently into the reactor. Combinations of such feed techniques can be used.

If a catalyst is used it can be fed in admixture with the bromine or in admixture with the DPO or the catalyst can be fed separately as a concurrent feed. Combinations of such procedures can also be used. In short, any suitable way of bringing the components together in order to form an intermediate product having a number or average number of bromine atoms in one of the ranges described above can be used.

[0029] It will be noted that by forming an intermediate product having a number or an average number of bromine atoms per molecule in one of the ranges described above, about 20 to about 80% or about 40 to about 60% or about 50 to about 60% of the total HBr load in going from DPO to DBDPO is removed. When lightly brominated diphenyl oxide is present in the feed, the total HBr load removed is reduced from these respective values in an amount essentially equal to the content of bromine in the lightly brominated diphenyl oxide.

Recovery of Intermediate Product in b)

[0030] As noted above, at least a portion of the intermediate product formed in a) is typically in the form of solid particles. These can be readily recovered from the intermediate product by use of centrifugation, filtration, decantation or like solids/liquid physical separation procedures. In any case where the intermediate product formed in a) is entirely in solution in the reaction mixture, the intermediate product can be recovered from the reaction mixture by simply boiling off the bromine and any other co- solvent present. In such case the distillate should be condensed so as to recover the bromine or fractionated so as to recover the bromine and the solvent as separate entities.

Bromination in c)

[0031] Among the principal features of c) is the intermediate product recovered in b) is used as the feed to be brominated in c). Because the intermediate product contains little, if any, hydrogen bromide, it can be directly used as such feed in c) . Because the intermediate product is used as feed in c) the total load of hydrogen bromide formed in c) is significantly reduced. Indeed, when feeding intermediate product containing an average in the range of about 5 to about 6 bromine atoms per molecule, only 40 to 50% of the total bromine load in going from DPO to DBDPO will be formed as a coproduct in c). Also, the reaction period or average residence time in c) can be much shorter than if a one- stage bromination from DPO to DBDPO were used.

[0032] In the practice of this invention the processing disclosed in commonly owned copending U.S. Application No. 60/823,811, filed on August 29, 2006, and entitled "Preparation of High-Assay Decabromodiphenyl Oxide" is adapted for use in c) in order to achieve preparation of reaction-derived DBDPO product of high purity. [0033] The length of the feeding period in c) is temperature dependent. Thus, when the feeding time is taking place at a refluxing temperature in the range of about 57 ° C to about 60 ° C, the reaction time will typically be longer than when the bromination is occurring at a higher temperature. Thus, in carrying out a process of this invention, if the temperature- dependent period has not already been determined for the particular operation, a few laboratory experiments should be conducted for optimization purposes. It is to be noted that at any given temperature use of a higher concentration of catalyst may enable the reaction time to be shortened to some extent, provided that the hydrogen bromide concentration in the liquid phase of the reaction mixture is kept to a minimum or at least low enough as not to prevent preparation of reaction-derived DBDPO product of high purity. [0034] Generally speaking, from the viewpoint of productivity and plant throughput, the shorter the feed period used in c), the better. But pursuant to this invention the feed period in c) used should be sufficiently long at the reaction temperature being used to enable the desired equilibrium state to be reached whereby the reaction-derived product is a high purity product. [0035] In practicing c) in a process of this invention it is important to reduce the content of hydrogen bromide present in the reactor. Among various ways of achieving such reduction in the amount of hydrogen bromide present in the reactor are the following:

> A combination of vigorous refluxing of the bromine in the reactor, withdrawal of the hydrogen bromide vapor phase from the reactor, and efficient condensation of bromine vapors being withdrawn with the hydrogen bromide is desirable and is preferably utilized.

> Use of a fractionation column to effectively separate as much HBr from the bromine in the column as feasible. In this way the bromine returning to the reactor carries less, if any, HBr back into the reactor. The fractionation column can be a packed column or it can be free of packing, and should be designed to effect an efficient separation of HBr from bromine. > An inert gas purge of the reactor (e.g., with argon, neon, or preferably nitrogen) to carry away HBr is useful.

> Use of bromine in the vapor state as a stripping gas. Besides carrying away HBr, the use of bromine vapors is a way of introducing more heat into the reactor and thereby contributing to more vigorous refluxing within the system.

> Operation at atmospheric, subatmospheric or superatmo spheric pressures to enable a refluxing condition of the reaction mixture at the selected process temperature. > Since the bromination is conducted in excess refluxing bromine, the reactor is of course equipped with a reflux condenser and preferably a reflux fractionation column. This should be designed to return to the reaction as little HBr in the condensed bromine as is technically and economically feasible under the circumstances. [0036] In all cases, the hydrogen bromide leaving the reaction system in c) is preferably recovered for use or sale. Recovery can be achieved by use of a suitable scrubbing system using one or more aqueous liquid scrubbers such as water, or dilute NaOH solution. [0037] The relationship between bromination reaction temperature and pressure under which the bromination in c) is being operated is worthy of comment. Ideally it is desirable to operate at as high a temperature as possible and as low a pressure as possible to adequately reduce the HBr concentration in the bromine, because in this way more HBr is removed from the reactor. Sampling a refluxing bromination reaction mixture of this type in order to assay the percentage of HBr dissolved in the Br₂ at any given time is not deemed feasible when using ordinary laboratory or plant equipment. Such sampling requires special equipment such as built-in stationary probes to periodically remove representative samples of the reaction mixture from the reactor. Thus when using ordinary plant equipment, operation at maximum temperature and minimum pressure is desirable as a way of reducing the HBr concentration in the bromine. However, maintaining a high reaction temperature in such a reaction system is not as easy as it might appear. For one thing, considerable heat input is required to the reaction mixture, and this can impose limitations in existing plant equipment. Consequently, in most cases it is desirable when operating on a commercial scale to conduct the reaction at a mildly elevated pressure (e.g., in the range of about 5 to about 20 psig (ca. 1.35xlO⁵ to 2.39x 10⁵ Pa)), and to have the temperature high enough to effect vigorous refluxing to thereby keep the HBr concentration in the bromine low as more HBr is removed from the reactor. [0038] This invention is deemed to enable the preparation of highly pure DBDPO products that are derived from the bromination of diphenyl oxide and/or lightly brominated diphenyl oxide. Such products can be said to be "reaction-derived" since they are reaction determined and not the result of use of downstream purification techniques, such as recrystallization, chromatography, or like procedures. In other words, the products of high purity are directly produced in the synthesis process apart from use of subsequent purification procedures that remove nonabromodiphenyl oxide from the decabromodiphenyl oxide product.

[0039] The DPO and/or lightly brominated DPO can be fed as solids , but preferably the feed is in molten form or as a solution in a solvent such as methylene bromide or bromoform. To prevent freeze up in the feed conduit, DPO is desirably fed at a temperature of in the range at least of 28 to 35 °C. Higher temperatures can be used if desired.

[0040] Excess bromine is used in the Lewis acid catalyzed bromination reaction. Typically, the reaction mixture will contain in the range of at least about 14 moles of bromine per mole of DPO to be fed thereto, and preferably, the reaction mixture contains in the range of about

16 to about 25 moles of bromine per mole of DPO to be fed thereto. It is possible to use more than 25 moles bromine per mole of DPO but this offers no advantage. When the feed is lightly brominated DPO, enough bromine should be present to provide in the range of about 4 to about 12 moles of excess bromine over the amount required to perbrominate the lightly brominated DPO. When the feed is a mixture of DPO and lightly brominated DPO, the amount of excess bromine should be enough to provide a corresponding excess over the amounts sufficient to perbrominate the DPO and the lightly brominated DPO. [0041] Typically the refluxing temperature of bromine at atmospheric or slightly elevated pressures is in the range of about 57 to about 59 ° C but when operating in c) at higher elevated pressures somewhat higher temperatures are used in order to maintain a refluxing condition.

[0042] If desired, a suitable solvent can be included in the reaction mixture of c). This can be advantageous in that one can have a higher reaction temperature and possibly a lower HBr concentration in the bromine thereby giving higher purity DBDPO. Among such solvents are methylene bromide and bromoform. [0043] In conducting c),various iron and/or aluminum Lewis acids can be added to the bromine to serve as the bromination catalyst. These include the metals themselves such as iron powder, aluminum foil, or aluminum powder, or mixtures thereof. Preferably use is made of such catalyst materials as, for example, ferric chloride, ferric bromide, aluminum chloride, aluminum bromide, or mixtures of two or more such materials. More preferred are aluminum chloride and aluminum bromide with addition of aluminum chloride being more preferred from an economic standpoint. It is possible that the makeup of the catalyst may change when contained in a liquid phase of refluxing bromine. For example, one or more of the chlorine atoms of the aluminum chloride may possibly be replaced by bromine atoms. Other chemical changes are also possible. The Lewis acid should be employed in an amount sufficient to effect a catalytic effect upon the bromination reaction being conducted.

Typically, the amount of Lewis acid used will be in the range of about 0.06 to about 2 wt%, and preferably in the range of about 0.2 to about 0.7 wt% based on the weight of the bromine being used. [0044] After all DPO and/or lightly brominated DPO is added, the reaction mixture can be kept at reflux for a suitable period of time to ensure completion of the perbromination to

DBDPO. A period of up to about one hour can be used. [0045] Termination of the bromination reaction is typically effected by deactivating the catalyst with water and/or an aqueous base such as a solution of sodium hydroxide or potassium hydroxide.

Gas Chromatographic Procedure

[0046] The gas chromatography is on a Hewlett-Packard 5890, series II, with Hewlett- Packard model 3396 series II integrator, the software of which is that installed with the integrator by the manufacturer. The gas chromatograph column used is an aluminum clad fused silica column, Code 12 AQ5 HT5 (Serial number A132903) obtained from SGE

Scientific, with film thickness of 0.15 micron. The program conditions are: initial start temperature 250⁰C, ramped up to 300 °C at a rate of 5 °C/min. The column head pressure is 10 psig (ca. 1.7OxIO⁵ Pa). The carrier gas is helium. The injection port temperature is 275 ° C and the flame ionization temperature is 325 °C. Samples are prepared by dissolving ca. 0.1 g in 8-10 mL of dibromomethane. The injection size is 2.0 microliters.

DBDPO Products and Flame Retardant Usage

[0047] The DBDPO products formed in processes of this invention are white or slightly off- white in color. White color is advantageous as it simplifies the end-user's task of insuring consistency of color in the articles that are flame retarded with the DBDPO products. [0048] The DBDPO products formed in the processes of this invention may be used as flame retardants in formulations with virtually any flammable material. The material may be macromolecular, for example, a cellulosic material or a polymer. Illustrative polymers are: olefin polymers, cross-linked and otherwise, for example homopolymers of ethylene, propylene, and butylene; copolymers of two or more of such alkene monomers and copolymers of one or more of such alkene monomers and other copolymerizable monomers, for example, ethylene/propylene copolymers, ethylene/ethyl acrylate copolymers and ethylene/propylene copolymers, ethylene/acrylate copolymers and ethylene/vinyl acetate copolymers; polymers of olefinically unsaturated monomers, for example, polystyrene, e.g. high impact polystyrene, and styrene copolymers, polyurethanes; polyamides; polyimides; polycarbonates; polyethers; acrylic resins; polyesters, especially poly(ethyleneterephthalate) and poly(butyleneterephthalate); polyvinyl chloride; thermosets, for example, epoxy resins; elastomers, for example, butadiene/styrene copolymers and butadiene/acrylonitrile copolymers; terpolymers of acrylonitrile, butadiene and styrene; natural rubber; butyl rubber and polysiloxanes. The polymer may be, where appropriate, cross-linked by chemical means or by irradiation. The DBDPO products of this invention can be used in textile applications, such as in latex -based back coatings. [0049] The amount of a DBDPO product of this invention used in a formulation will be that quantity needed to obtain the flame retardancy sought. It will be apparent to those skilled in the art that for all cases no single precise value for the proportion of the product in the formulation can be given, since this proportion will vary with the particular flammable material, the presence of other additives and the degree of flame retardancy sought in any given application. Further, the proportion necessary to achieve a given flame retardancy in a particular formulation will depend upon the shape of the article into which the formulation is to be made, for example, electrical insulation, tubing, electronic cabinets and film will each behave differently. In general, however, the formulation, and resultant product, may contain from about 1 to about 30 wt%, preferably from about 5 to about 25 wt% DBDPO product of this invention. Masterbatches of polymer containing DBDPO, which are blended with additional amounts of substrate polymer, typically contain even higher concentrations of

DBDPO, e.g., up to 50 wt% or more.

[0050] It is advantageous to use the DBDPO products of this invention in combination with antimony-based synergists, e.g., Sb₂O₃. Such use is conventionally practiced in all DBDPO applications. Generally, the DBDPO products of this invention will be used with the antimony based synergists in a weight ratio ranging from about 1:1 to 7 : 1 , and preferably of from about 2: 1 to about 4: 1.

[0051] Any of several conventional additives used in thermoplastic formulations may be used, in their respective conventional amounts, with the DBDPO products of this invention, e.g., plasticizers, antioxidants, fillers, pigments, UV stabilizers, etc. [0052] Thermoplastic articles formed from formulations containing a thermoplastic polymer and DBDPO product of this invention can be produced conventionally, e.g., by injection molding, extrusion molding, compression molding, and the like. Blow molding may also be appropriate in certain cases. [0053] 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.

[0054] 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. [0055] 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.

Claims

1. A process for forming reaction-derived decabromodiphenyl oxide product of high purity, which process comprises: a) brominating diphenyl oxide and/or lightly brominated diphenyl oxide in a reaction mixture containing an excess of refluxing bromine and, optionally, a catalytic quantity of Lewis acid bromination catalyst to form a first reaction mixture which comprises bromine, and an intermediate brominated diphenyl oxide product having an average in the range of about 2 to about 8 bromine atoms per molecule; b) recovering intermediate brominated diphenyl oxide product formed in a); and c) feeding intermediate brominated diphenyl oxide product recovered in b) into a reaction zone containing a refluxing second reaction mixture comprising (i) an excess of bromine and (ii) a catalytic quantity of Lewis acid bromination catalyst, and concurrently removing hydrogen bromide coproduct from the reaction zone in a sufficient amount to form a reaction-derived decabromodiphenyl oxide product of high purity.

2. A process as in Claim 1 wherein the reaction mixture in a) contains a catalytic quantity of Lewis acid bromination catalyst.

3. A process as in Claim 1 wherein the reaction mixture in a) is devoid of a catalytic quantity of Lewis acid bromination catalyst.

4. A process as in Claim 1 wherein at least a portion of said intermediate brominated diphenyl oxide product in a) is in the form of solids and wherein in b) said solids are recovered in the form of solids from the first reaction mixture.

5. A process as in Claim 4 wherein solids recovered in b) are fed in c) as a solution or slurry in fresh bromine or an appropriate solvent, or in both.

6. A process as in Claim 1 wherein at least a portion of said intermediate brominated diphenyl oxide product in a) is in the form of solids and wherein in b) said solids are recovered from said intermediate brominated diphenyl oxide product by centrifugation, filtration or decantation and said solids are fed in c) as a solution or slurry in fresh bromine, and wherein at least a portion of the liquid phase from said centrifugation, filtration or decantation is recycled to the bromination in a).

7. A process as in any of Claims 1-6 wherein said intermediate brominated diphenyl oxide product has an average in the range of about 4 to about 6 bromine atoms per molecule.

8. A process as in any of Claims 1-6 wherein said intermediate brominated diphenyl oxide product has an average in the range of about 5 to about 6 bromine atoms per molecule.