Process for recovering quaternary chlorobromination catalysts

Abstract

The quaternary ammonium tribromide and quaternary phosphonium tribromide are recovered from the organic solvent by washing with an aqueous hydrazine solution. The hydrazine reacts to form nitrogen, hydrobromic acid, and a quaternary ammonium or quaternary phosphonium monobromide. The hydrobromic acid and the quaternary ammonium or quaternary phosphonium transfer to the aqueous phase, thereby achieving removal of the tribromide from the organic solvent. The hydrobromic acid can be neutralized with a quaternary ammonium or quaternary phosphonium hydroxide to produce a quaternary ammonium or quaternary phosphonium monobromide. The produced monobromide can be reacted with elemental bromine to regenerate the tribromide brominating agent.

Description

[Technical field]

[0001] The present invention relates to a process for the recovery of quaternary chlorobromination catalysts from organic solvents. [Background technology]

[0002] Quaternary ammonium tribromide salts and quaternary phosphonium tribromide salts are useful brominating agents for brominating polymers containing aliphatic carbon-carbon double and triple bonds, such as butadiene polymers. See, for example, WO 2008 / 021417, WO 2008 / 021418, and WO 2010 / 021906. The process is carried out with a starting polymer dissolved in an organic solvent. The tribromide salts are converted to the corresponding monobromides when the polymer is brominated. The monobromides are water-soluble and can be removed from the organic phase by aqueous extraction. The monobromides can be combined with elemental bromine to regenerate the tribromides, and therefore it is economically important to recover the monobromides and recycle them by the process. Highly selective bromination of aliphatic carbon-carbon unsaturation is achieved, leaving any aromatic rings that may be present essentially unaffected. Brominated butadiene polymers so produced tend to have good thermal properties and can be used as flame retardant additives for thermoplastic polymers such as polystyrene.

[0003] It is beneficial to operate the process with a small excess of tribromide brominating agent because doing so increases the rate of bromination and the extent to which the aliphatic carbon-carbon unsaturation of the starting polymer is brominated. Unreacted tribromide brominating agent is soluble in organic solvents but not in the aqueous phase, and therefore it tends to remain in the organic phase and the brominated polymer when it is recovered. This is undesirable from several standpoints.

[0004] Therefore, the residual brominating agent remaining in the organic phase is usually quenched to convert it to a water-soluble species that can be removed from the organic phase by aqueous extraction. The quenching agent chosen was sodium bisulfite, which upon reaction with the tribromide produces a mixture of sodium sulfite, hydrobromic acid, and quaternary ammonium or quaternary phosphonium monobromide, all of which are water-soluble and easily extracted. Unfortunately, it is difficult to separate the monobromide from other by-products, and therefore this mixture is usually sent to the waste stream, resulting in the loss of valuable quaternary ammonium or quaternary phosphonium monobromide. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, a better method of removing residual quaternary ammonium or quaternary phosphonium tribromides from organic solvents is desired. Such a method would allow the quaternary ammonium or quaternary phosphonium values ​​to be recovered in a form that allows them to be reused in the bromination process. In addition, such a process would preferably allow for the recovery of bromine, which can then also be reused in the bromination process. [Means for solving the problem]

[0006] The present invention relates to a process for removing a quaternary ammonium or quaternary phosphonium tribromide from an organic solvent, comprising the steps of: a) washing an organic solvent containing a quaternary ammonium or phosphonium tribromide with an aqueous hydrazine solution in an amount sufficient to provide at least 0.25 moles of hydrazine per mole of quaternary ammonium or phosphonium tribromide in the organic solvent to produce an aqueous phase containing hydrobromic acid and a quaternary ammonium or phosphonium monobromide corresponding to the quaternary ammonium or phosphonium tribromide; and then b) separating the aqueous phase from the organic solvent; The present invention relates to a process comprising: DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] In one aspect, the present invention provides a process for removing a quaternary ammonium or quaternary phosphonium tribromide from an organic solvent, comprising the steps of: a) washing an organic solvent containing a quaternary ammonium or phosphonium tribromide with an aqueous hydrazine solution in an amount sufficient to provide at least 0.25 moles of hydrazine per mole of quaternary ammonium or phosphonium tribromide in the organic solvent to produce an aqueous phase containing hydrobromic acid and a quaternary ammonium or phosphonium monobromide corresponding to the quaternary ammonium or phosphonium tribromide; and then b) separating the aqueous phase from the organic solvent; The process includes:

[0008] This process is an economical and efficient method for removing tribromide from organic solvents. The reaction products are nitrogen, which can be separated from the aqueous phase using any convenient gas / liquid separation method; monobromide, which can be recovered and rebrominated for reuse as a brominating agent; and hydrobromic acid, which can be neutralized, if necessary, to recover bromine values ​​that can also be reused in the bromination process. All of the reaction products are water soluble and partition almost exclusively into the aqueous phase, resulting in excellent separation of the tribromide from the organic solvent.

[0009] In a preferred embodiment, the organic solvent contains a brominated polymer and the process further comprises, after step a), a step c) of recovering the brominated polymer from the organic solvent.

[0010] The process may also include, after step a), a step d) of neutralizing the hydrobromic acid in the aqueous phase with a quaternary ammonium or quaternary phosphonium hydroxide to produce the corresponding quaternary ammonium or quaternary phosphonium monobromide. In such an embodiment, bromine is recovered in the form of a quaternary ammonium or quaternary phosphonium monobromide. The monobromide is contacted with additional bromine to regenerate the corresponding tribromide, which in turn can be used in a subsequent bromination reaction.

[0011] In yet another preferred embodiment, the process further comprises the step of e) combining the quaternary ammonium or quaternary phosphonium monobromide obtained in step a) and / or step d) with elemental bromine to regenerate the quaternary ammonium or quaternary phosphonium tribromide.

[0012] The process further comprises a further step f) of brominating an organic polymer having aliphatic carbon-carbon double and / or triple bonds by contacting said organic polymer with the regenerated quaternary ammonium or quaternary phosphonium tribromide obtained in step e).

[0013] Processes for brominating organic polymers containing aliphatic carbon-carbon double and / or triple bonds using quaternary ammonium or quaternary phosphonium tribromides are generally described, for example, in U.S. Patent No. 7,851,558, WO 2008 / 021417, WO 2008 / 021418, WO 2009 / 126531 and WO 2010 / 021906. In such processes, a starting polymer containing aliphatic carbon-carbon unsaturation (i.e., moieties where adjacent carbon atoms are double or triple bonded to each other and where the double or triple bonds do not form part of a conjugated system or aromatic ring structure) is contacted with a quaternary ammonium tribromide and / or a quaternary phosphonium tribromide brominating agent to brominate some or all of the aliphatic carbon-carbon unsaturation. Usually, it is advantageous to use 0.5 to 5 moles of tribromide brominating agent per mole of aliphatic carbon-carbon unsaturation to be brominated; a more preferred amount is from about 0.9 to about 2.5 moles / mole, and an even more preferred amount is from 1 to 1.5 moles / mole.

[0014] The reaction is preferably carried out with the starting polymer dissolved and / or dispersed in an organic solvent that is water-immiscible. "Water-immiscible" means that the material is soluble in water to the extent of 5 grams or less, preferably 2 grams or less, per liter of water at 25°C. The bromination temperature can range from -20 to 100°C, preferably 0 to 85°C, in particular 10 to 40°C. The reaction produces quaternary ammonium and / or quaternary phosphonium monobromides corresponding to the tribromide brominating agent after removal of two bromine atoms.

[0015] The starting organic polymer has at least one site of aliphatic carbon-carbon unsaturation, and can have any higher number.

[0016] Polymers and copolymers of conjugated diene monomers, especially homopolymers and copolymers of butadiene, are a preferred class of substrates. Copolymers of conjugated dienes should contain at least 10% by weight of polymerized conjugated diene. The copolymers may be of the random, block or graft type and will contain repeat units formed by polymerizing another monomer. Such other monomers include vinyl aromatic monomers, olefins such as ethylene and propylene, and acrylate or acrylic monomers such as methyl methacrylate, methyl acrylate, acrylic acid, etc., as described in more detail below. These monomers may be randomly polymerized with the conjugated diene, polymerized to form blocks, or grafted onto the conjugated polymer.

[0017] The starting polymer has a weight average molecular weight (M) in the range of 1,000 to 400,000, preferably 5,000 to 300,000, more preferably 10,000 to 200,000, and even more preferably 50,000 to 175,000. w For purposes of this invention, molecular weight is the apparent molecular weight as measured by gel permeation chromatography (GPC) against polystyrene standards. GPC molecular weight measurements can be performed using an Agilent 1100 series liquid chromatograph equipped with two Polymer Laboratories PLgel 5 micrometer Mixed-C columns connected in series and an Agilent G1362A refractive index detector or equivalent device, using tetrahydrofuran (THF) as the eluent flowing at a rate of 1 mL / min and heated to a temperature of 35° C.

[0018] Particularly interesting starting polymers are random, block or graft copolymers of butadiene and at least one vinyl aromatic monomer. A "vinyl aromatic" monomer is an aromatic compound having a polymerizable ethylenically unsaturated group attached directly to a carbon atom of the aromatic ring. Vinyl aromatic monomers include unsubstituted materials such as styrene and vinyl naphthalene as well as compounds substituted on the ethylenically unsaturated group (e.g., alpha-methylstyrene) and / or ring-substituted. Ring-substituted vinyl aromatic monomers include those having halogen, alkoxyl, nitro or unsubstituted or substituted alkyl groups attached directly to a carbon atom of the aromatic ring. Examples of such ring-substituted vinyl aromatic monomers include 2- or 4-bromostyrene, 2- or 4-chlorostyrene, 2- or 4-methoxystyrene, 2- or 4-nitrostyrene, 2- or 4-methylstyrene and 2,4-dimethylstyrene. Preferred vinyl aromatic monomers are styrene, alpha-methylstyrene, para-methylstyrene and mixtures thereof.

[0019] "Vinyl aromatic units" refers to the repeat units in the starting material that are formed when vinyl aromatic monomers are polymerized. Suitable starting butadiene / vinyl aromatic copolymers contain from 5 to 90 weight percent polymerized vinyl aromatic monomer units.

[0020] Butadiene / vinyl aromatic copolymers can be random, block (including multiblock, such as diblock or triblock types) or graft type copolymers. Styrene / butadiene block copolymers are widely available in commercial quantities. Those available from Dexco Polymers under the trade name VECTOR™ are suitable. Styrene / butadiene random copolymers can be prepared, for example, according to the process described by AF Halasa in Polymer, Volume 46, page 4166 (2005). Styrene / butadiene graft copolymers can be prepared according to the method described by AF Halasa in Journal of Polymer Science (Polymer Chemistry Edition), Volume 14, page 497 (1976). Styrene / butadiene random and graft copolymers can also be prepared according to the method described by Hsieh and Quirk in chapter 9 of Anionic Polymerization Principles and Practical Applications, Marcel Dekker, Inc., New York, 1996.

[0021] Butadiene / vinyl aromatic polymers may also contain repeat units formed by polymerizing monomers other than butadiene with vinyl aromatic monomers. The most preferred type of butadiene / vinyl aromatic copolymer is a block copolymer containing one or more polystyrene blocks and one or more polybutadiene blocks. Of these, diblock copolymers and triblock copolymers having a central polybutadiene and terminal polystyrene blocks are especially preferred.

[0022] The brominating agent is a quaternary ammonium tribromide, a quaternary phosphonium tribromide, or a mixture of two or more thereof. Quaternary ammonium tribromides have the formula R +The quaternary ammonium tribromide may be a tetraalkylammonium tribromide, where each of the R groups is an alkyl. All four R groups may be the same. Alternatively, two, three or even four different R groups may be attached to the nitrogen atom. Each R group is preferably an alkyl group having 1 to 20 carbon atoms. More preferably, the R group is an alkyl group having 1 to 8 carbon atoms. Specific examples of quaternary ammonium tribromide include tetramethylammonium tribromide, tetraethylammonium tribromide, tetra(n-propyl)ammonium tribromide, tetra(n-butyl)ammonium tribromide, tetrahexylammonium tribromide, tetraoctylammonium tribromide, tri(hexyl)tetradecylammonium tribromide, and the like, or mixtures thereof. Tetraethylammonium tribromide is a particularly preferred brominating agent.

[0023] Quaternary phosphonium tribromides have the formula R4P + The quaternary phosphonium group can be represented by the formula: where each R is as described above for the quaternary ammonium tribromide. As already mentioned, the R groups can all be the same, or there can be two, three or even four different R groups attached to the phosphorus atom. Examples of specific quaternary phosphonium tribromides include tetramethylphosphonium tribromide, tetraethylphosphonium tribromide, tetra(n-propyl)phosphonium tribromide, tetra(n-butyl)phosphonium tribromide, tetrahexylphosphonium tribromide, tetraoctylphosphonium tribromide, tri(hexyl)tetradecylphosphonium tribromide, and the like, or mixtures thereof.

[0024] The tribromide brominating agents can be formed in situ, i.e. in the presence of the substrate, by separately adding elemental bromine and the corresponding quaternary ammonium or quaternary phosphonium monobromide to the organic polymer or to a solution / dispersion of the organic polymer in an organic solvent, as described in WO 2010 / 021906.

[0025] The organic solvent should be a solvent for the starting polymer and preferably the quaternary phosphonium tribromide as well. The brominated product may or may not be soluble in the organic solvent. The solvent is preferably substantially immiscible in water. The density of the solvent is different from that of water, preferably higher than that of water, so that the solvent will easily separate from water to form a separate phase under some static conditions. The solvent density is preferably at least 1.05, more preferably at least 1.10 g / cc. In addition, the solvent should not react with the starting butadiene polymer, the brominated butadiene polymer or the quaternary ammonium monobromide and tribromide or the quaternary phosphonium monobromide or tribromide, as the case may be. The quaternary ammonium or quaternary phosphonium monobromide generated during the reaction is preferably relatively insoluble in the organic solvent compared to its solubility in water. The equilibrium distribution coefficient K for the extraction of the monobromide from the solvent into water is D is the ratio of the concentration of the quaternary ammonium monobromide salt in the aqueous phase divided by its concentration in the solvent phase. The coefficient K D may be at least 5 or at least 10, and may be any larger value.

[0026] Preferred solvents have a boiling temperature (at atmospheric pressure) of less than 100° C. (especially less than 80° C.), are immiscible in water, are aprotic, contain no aliphatic carbon-carbon unsaturation, and contain no hydrogen attached to a tertiary carbon atom. Suitable solvents include ethers such as tetrahydrofuran; various carboxylic acid esters, halogenated alkanes such as carbon tetrachloride, chloroform, dichloromethane, bromochloromethane, dibromomethane, 1,2-dibromoethane, and 1,2-dichloroethane; hydrocarbons such as heptane, octane, decane, cyclohexane, cyclopentane, cyclooctane, and toluene, and halogenated aromatics such as bromobenzene, chlorobenzene, and dichlorobenzene. Three particularly preferred solvents are dichloroethane, dichloromethane, and cyclohexane.

[0027] Unreacted and / or excess quaternary ammonium or quaternary phosphonium tribromide remains in the organic solvent at the end of bromination.In the present invention, the organic solvent containing quaternary ammonium or quaternary phosphonium tribromide is washed with an amount of hydrazine aqueous solution sufficient to provide at least 0.25 moles of hydrazine per mole of quaternary ammonium or quaternary phosphonium tribromide in the organic solvent.In the bromination process described above, it is unnecessary and even less preferred to separate the organic phase from any aqueous phase present during the bromination step before contacting the organic phase with the aqueous hydrazine solution, although it can be done if necessary.

[0028] The washing step is carried out by combining an organic solvent containing a quaternary ammonium tribromide or a quaternary phosphonium tribromide with an aqueous hydrazine solution. The combined material is preferably stirred to promote good contact between the phases, and in particular to facilitate contact between the tribromide and the hydrazine. The washing step can be carried out, for example, in a stirred vessel; by passing the combined material through a static or active mixing device, such as a static mixer or a rotary evaporator, by ultrasonic mixing or other convenient techniques.

[0029] Sufficient aqueous hydrazine solution is combined with the organic phase to provide at least 0.25 moles of hydrazine per mole of quaternary ammonium or quaternary phosphonium tribromide in the organic phase. The preferred amount is at least 0.4 moles, at least 0.475 moles, or at least 10.5 moles on the same basis. Excess hydrazine can be provided, but a large excess, such as more than 0.75 moles per mole of tribromide, is generally unnecessary. In addition, the aqueous hydrazine solution preferably contains sufficient water to dissolve the quaternary ammonium and / or quaternary phosphonium monobromide formed in this step, either by itself or in combination with one or more other aqueous phases that may be present (such as the aqueous phase from the bromination reaction).

[0030] The concentration of hydrazine in the aqueous solution can be, for example, at least 1% by weight, at least 5% by weight, at least 10% by weight, at least 20% by weight, or at least 30% by weight, and up to the saturation limit, preferably up to 50% by weight, based on the combined weight of water and hydrazine.

[0031] The temperature during this step may vary widely, such as from 0° C. to 100° C. The lower temperature may be at least 10° C. or at least 15° C., and the upper temperature may be up to 60° C., up to 50° C. or up to 40° C. This step may be carried out at atmospheric, subatmospheric or superatmospheric pressure, the pressure and temperature being preferably selected together such that the water and organic solvent remain in a liquid state. The duration of the reaction may vary from 5 seconds to 5 hours or more, with preferred durations being up to 1 hour or up to 30 minutes. The reaction is preferably carried out under non-oxidizing conditions, for example under an inert atmosphere such as a nitrogen, argon or helium atmosphere. The reaction mixture and / or its components may be sparged, such as with an inert gas, to remove dissolved oxygen.

[0032] The hydrazine and the remaining and / or excess quaternary ammonium or phosphonium tribromide react to produce nitrogen, hydrobromic acid, and the quaternary ammonium or phosphonium monobromide corresponding to the quaternary ammonium or phosphonium tribromide. By "corresponding" it is meant that the quaternary ammonium or phosphonium group is the same between the monobromide and the tribromide, i.e. the R group is the same in each case. The consumption of the tribromide is accompanied by a change in color in the organic phase, from orange or red to clear (white). The progress of the reaction can therefore be followed visually or by colorimetry. The pH of the aqueous phase typically drops to less than 1 as hydrobromic acid is produced, and therefore pH measurements can be used to follow the reaction. Spectroscopic methods such as Raman spectroscopy can be used, and therefore the evolution of nitrogen gas can also be used to follow the progress of the reaction.

[0033] The aforementioned reaction products are either strongly partitioned into the aqueous phase or evolved as a gas (as in the case of nitrogen). In step b) of the process, the aqueous phase containing hydrobromic acid and quaternary ammonium or quaternary phosphonium monobromide is separated from the organic phase, which may contain dissolved brominated polymer in the bromination process described above. Since the phases are typically immiscible, separation can be achieved by allowing the phases to separate, such as by exposing them to quiescent conditions, and then removing one phase from the other using any convenient technique for separating immiscible liquid phases. The aqueous phase is usually lighter and forms the upper layer upon phase separation.

[0034] The brominated polymer is optionally recovered from the organic phase. Various methods are useful for achieving this. The brominated polymer can be isolated from the mixture by precipitating it from the solution using various solvent stripping methods, extraction methods, or antisolvents. Examples of such antisolvents include lower alcohols such as methanol, ethanol, and 1-propanol, 2-propanol, n-butanol, and t-butanol. In one suitable recovery method, the solution is formed into fine droplets. The solvent is thermally stripped from the droplets to form particles of the brominated product. Before or after the thermal stripping step, the droplets or particles are washed in water. In another suitable recovery method, the solution is formed into droplets and sprayed onto a heated, mechanically agitated bed of seed particles. The droplets contact the seed particles where the solvent is driven off and the precipitated brominated product forms a shell around the individual seed particles, thereby increasing their diameter. The isolated brominated polymer may be purified to remove remaining bromine, brominating agent, solvent and by-products as desired or needed for a particular application.

[0035] The hydrobromic acid in the aqueous phase can be neutralized with a quaternary ammonium hydroxide or a quaternary phosphonium hydroxide to produce the corresponding quaternary ammonium monobromide or quaternary phosphonium monobromide. By neutralizing the hydrobromic acid in this manner, bromine is recovered in the form of a quaternary ammonium monobromide or a quaternary phosphonium monobromide.

[0036] Alternatively, the hydrobromic acid can be neutralized or otherwise consumed as desired by combining the aqueous phase with one or more different bases or other substances such as epoxides and lactones that react with hydrobromic acid.

[0037] Preferably, the quaternary ammonium or quaternary phosphonium hydroxide used in the neutralization step has the same ammonium or phosphonium ion structure as the quaternary ammonium or quaternary ammonium monobromide in the aqueous phase, i.e., in each case, R + or R4P + The R groups of the ions are the same. Thus, for example, if the quaternary ammonium bromide in the aqueous phase is tetraethylammonium monobromide, it is preferred to use tetraethylammonium hydroxide to neutralize hydrobromic acid. This has the advantage that instead of forming a mixture, it rather produces the same quaternary ammonium or quaternary phosphonium monobromide. This in turn makes it easier to recycle the monobromide back into the bromination process. The monobromide so produced can be contacted with additional bromine to regenerate the corresponding tribromide, which in turn can be used in a subsequent bromination reaction.

[0038] Suitable conditions for the neutralization reaction are generally as described for step a), i.e., the washing step. The quaternary ammonium or quaternary phosphonium hydroxide is conveniently provided in the form of an aqueous solution that can contain the hydroxide compound at any concentration up to its saturation limit in water; such an aqueous solution can contain, for example, at least 1% by weight, at least 5% by weight, at least 10% by weight, at least 20% by weight of the hydroxide compound. It is preferred to provide an aqueous solution sufficient to provide at least 0.5 moles, at least 0.75 moles, at least 0.9 moles, or at least 1 mole of quaternary ammonium or quaternary phosphonium hydroxide per mole of hydrobromic acid. An excess of hydroxide can be used, in which case it is preferred to use a molar excess of no more than 10% or no more than 5%.

[0039] In yet another preferred embodiment, the process further comprises a step e) of combining the quaternary ammonium or quaternary phosphonium monobromide obtained in step a) and / or step d) with elemental bromine to regenerate the quaternary ammonium or quaternary phosphonium tribromide. The process further comprises a step f) of brominating an organic polymer having aliphatic carbon-carbon double and / or triple bonds by contacting the organic polymer with the regenerated quaternary ammonium or quaternary phosphonium tribromide obtained in step e). Suitable conditions for carrying out these steps are described above and for example in US Pat. No. 7,851,558, WO 2008 / 021417, WO 2008 / 021418, WO 2009 / 126531 and WO 2010 / 021906. EXAMPLES

[0040] The following examples are offered to illustrate the invention but not to limit its scope. All parts and percentages are by weight unless otherwise specified.

[0041] Example 1 A jacketed 2 L reactor equipped with a circulator to control the reactor temperature, an overhead stirrer, a nitrogen inlet, and a condenser with fluid chilled by the circulator is charged with 476 mL of a 50 wt% aqueous solution of tetraethylammonium monobromide (TEAB) (1.27 moles of TEAB) and equilibrated at 10 °C. A solution of 22.18 g (0.139 moles) bromine in 500 mL of dichloromethane (DCM) is pumped into the reactor at a rate of 15-25 mL / min. The pump lines are rinsed into the reactor with an additional 500 ml of DCM. The circulator is stopped and the reaction mixture is stirred at room temperature for 1 h to produce a biphasic mixture with a yellow top aqueous layer and a red / orange bottom organic layer. The coloration indicates tetraethylammonium tribromide (TEATB) formation.

[0042] The biphasic mixture was transferred to a jacketed 5 L reactor equipped with a circulator to control the reactor temperature, an overhead stirrer, a nitrogen inlet, and a condenser with fluid chilled by the circulator and equilibrated at 20° C. Hydrazine solution (35 wt %, 6.35 g, 0.070 mol hydrazine) was added to the reactor over 5 minutes with stirring. The mixture turned from red / orange to colorless within 12 minutes after the addition was complete and nitrogen gas was evolved. On standing, the mixture again separated into an upper aqueous layer and a bottom organic layer, which were separated.

[0043] No TEATB in the bottom organic layer was detectable by Raman spectroscopy, indicating that hydrazine completely quenched TEATB from the organic phase. The color of the organic phase (red-orange or colorless) can be used as a general indicator of the quench reaction.

[0044] The aqueous layer contains TEAB and HBr as reaction products. It has a pH of less than 1. 10 mL of the aqueous layer containing 0.0049 mmol of theoretical amount of HBr is placed in a glass vial at room temperature. 2.1 mL of 35 wt % aqueous solution of tetraethylammonium hydroxide (TEAPH) (0.0051 mmol TEAOH, pH 6-6.4) is added to the vial. After stirring for 5 minutes at room temperature, an aliquot of the reaction mixture is removed. The pH is measured as about 4.5 using pH paper, indicating that the HBr has been neutralized by the TEAOH to form TEAB plus water. The pH rises to 13.5 after an additional 0.1 mL of TEAOH solution is added to the reaction mixture.

[0045] Example 2 536.6 g of a 50 wt % aqueous solution of TEAB (1.27 moles TEAB) is cooled to 0° C. in a 2 L jacketed mixing vessel. A solution of 179.0 g (1.12 moles) of bromine in 300 mL of DCM is pumped into the stirred reactor over 14 minutes. An additional 100 mL of DCM is used to rinse the pump and lines and is added to the reaction vessel. The reactor contents are stirred for 43 minutes to produce TEATB, which transfers to the organic phase. Agitation is stopped and the phases are allowed to separate to produce a red bottom organic layer and a yellow upper aqueous layer.

[0046] 80.1 g of styrene-butadiene-styrene triblock copolymer (80.5% vinyl) is dissolved in 1 liter of dichloromethane in a 5 L jacketed reactor equipped with a circulator and condenser cooling unit. The temperature is set to 0° C. and the red bottom TEATB-containing organic layer is pumped into the 5 L reactor over 3 minutes with stirring. The pump is rinsed with another 100 mL of DCM, which is also transferred to the 5 L reactor. The resulting reaction mixture is heated at reflux (40° C.) for 2.5 hours. The aqueous phase from the 2 L reactor is then pumped into the 5 L reactor, followed by a rinse of 50 mL fresh DCM. The resulting two-phase mixture is heated at 40° C. with stirring for an additional 2.5 hours, then cooled to 20° C.

[0047] A 35 wt% solution of hydrazine in water (22.9 g, 0.25 moles of hydrazine) is then added to the stirred reaction mixture. The red color dissipates to nearly colorless. Stirring is stopped and the phases are allowed to separate into an organic phase and an aqueous quench phase. The aqueous quench phase contains 50 wt% TEAB (90.5% of theory) and 0.5% residual hydrazine by proton NMR.

[0048] 416 g of the aqueous quench phase is combined with 187.5 g of a 35% solution of tetraethylammonium hydroxide in water, which neutralizes the HBr to form a neutralized aqueous quench phase containing 51 wt % TEAB and having a pH of 7.0.

[0049] The organic phase is washed twice with about 450 mL of deionized water. The washes are separated from the organic phase and kept separate. The first wash has a pH of 1.0 and contains 4.8 wt. % TEAB and negligible hydrazine; the second has a pH of 3.7 and contains no TEAB or hydrazine.

[0050] The brominated polymer is precipitated from the washed organic phase by addition of 2-propanol. The precipitated polymer is dried to remove residual solvent. 98.8% of the butadiene units are brominated as determined by proton NMR. Its 5% weight loss temperature is 257°C. Its isothermal weight loss temperature at 186°C is 0.22 wt%.

[0051] Example 3 537.6 g of the neutralized aqueous quench phase from Example 2 is cooled to 0° C. in a 2 L jacketed mixing vessel. A solution of 179.4 g (1.12 moles) of bromine in 300 ml of DC is pumped into the stirred reaction vessel over 14 minutes. An additional 100 mL of DCM is used to rinse the pump and lines and is added to the reaction vessel. The reactor contents are stirred for 60 minutes to produce TEATB, which transfers to the organic phase. Agitation is stopped and the phases are allowed to separate to produce a red bottom TEATB-containing organic layer and a yellow upper aqueous layer.

[0052] 80.1 g of styrene-butadiene-styrene triblock copolymer (80.5% vinyl) is dissolved in 1 liter of dichloromethane in a 5 L jacketed reactor equipped with a circulator and condenser cooling unit. The temperature is set to 0° C. and the red bottom TEATB-containing organic layer is pumped into the 5 L reactor over 2 minutes with stirring. The pump is rinsed with another 100 mL of DCM, which is also transferred to the 5 L reactor. The resulting reaction mixture is heated at reflux (40° C.) for 2.5 hours. The aqueous phase from the 2 L reactor is then pumped into the 5 L reactor, followed by a rinse of 50 mL fresh DCM. The resulting two-phase mixture is heated at 40° C. with stirring for an additional 2.5 hours, then cooled to 20° C.

[0053] A 35 wt% solution of hydrazine in water (1.7 g, 0.018 moles of hydrazine) is then added to the stirred reaction mixture. The red color dissipates to nearly colorless. Stirring is stopped and the phases are allowed to separate into an organic phase and an aqueous quench phase. The aqueous quench phase contains 29.5 wt% TEAB (96% of theory) and 0.004% residual hydrazine by proton NMR. The pH is 0.23.

[0054] The organic phase is washed twice with about 400 mL of deionized water. The washes are separated from the organic phase and kept separate. The first wash has a pH of 2.0; it contains 0.78 wt. % TEAB by proton NMR and no measurable hydrazine. The second wash has a pH of 3.5 and contains no TEAB or hydrazine by proton NMR. The brominated polymer is precipitated from the washed organic phase by the addition of 2-propanol. The precipitated polymer is dried to remove residual solvent. 98.8% of the butadiene units are brominated as determined by proton NMR.

[0055] The above experiment is repeated and the recovered brominated polymer from each experiment is combined for analysis. The 5% weight loss temperature of the combined material is 257° C.; its isothermal weight loss temperature at 186° C. is 0.22 wt.%. 95.8% of the butadiene units are brominated.

Claims

1. 1. A process for removing a quaternary ammonium or quaternary phosphonium tribromide from an organic solvent, comprising: a) washing an organic solvent containing said quaternary ammonium or quaternary phosphonium tribromide with an aqueous hydrazine solution in an amount sufficient to provide at least 0.25 moles of hydrazine per mole of quaternary ammonium or phosphonium tribromide in said organic solvent to produce an aqueous phase containing hydrobromic acid and a quaternary ammonium or phosphonium monobromide corresponding to said quaternary ammonium or phosphonium tribromide; and then b) separating the aqueous phase from the organic solvent; A process including.

2. 10. The process of claim 1, wherein the organic solvent contains a dissolved brominated polymer and the process further comprises, after step a), a step c) of recovering the brominated polymer from the organic solvent.

3. 2. The process of claim 1, further comprising the step of combining the quaternary ammonium or quaternary phosphonium monobromide obtained in step a) with elemental bromine to regenerate a quaternary ammonium or quaternary phosphonium tribromide.

4. 4. The process of claim 3, further comprising a step f) of brominating an organic polymer having aliphatic carbon-carbon double and / or triple bonds by contacting said organic polymer with said regenerated quaternary ammonium or quaternary phosphonium tribromide obtained by combining the quaternary ammonium or quaternary phosphonium monobromide obtained in step a) with elemental bromine.

5. 2. The process of claim 1, further comprising, after step a), a step d) of neutralizing the hydrobromic acid in the aqueous phase with a quaternary ammonium hydroxide or a quaternary phosphonium hydroxide to produce the corresponding quaternary ammonium monobromide or a quaternary phosphonium monobromide.

6. 6. The process of claim 5, further comprising the step of: e) combining the quaternary ammonium or quaternary phosphonium monobromide obtained in step d) with elemental bromine to regenerate a quaternary ammonium or quaternary phosphonium tribromide.

7. 7. The process of claim 6, further comprising the step of brominating an organic polymer having aliphatic carbon-carbon double and / or triple bonds by contacting said organic polymer with a regenerated quaternary ammonium or quaternary phosphonium tribromide obtained by combining the quaternary ammonium or quaternary phosphonium monobromide obtained in step d) with elemental bromine.

8. The organic solvent is carbon tetrachloride, chloroform, dichloromethane, bromochloromethane (CH ２ BrCl), dibromomethane, 1,2-dichloroethane, cyclohexane, toluene, bromobenzene, chlorobenzene and dichlorobenzene.

9. 2. The process of claim 1, wherein the quaternary ammonium tribromide or quaternary phosphonium tribromide is at least one of phenyltrimethylammonium tribromide, benzyltrimethylammonium tribromide, tetramethylammonium tribromide, tetraethylammonium tribromide, tetrapropylammonium tribromide, and tetra-n-butylammonium tribromide.

10. 3. The process of claim 2, wherein the dissolved brominated polymer is a bromobutadiene homopolymer or a brominated random, block or graft copolymer of butadiene and at least one vinyl aromatic monomer.

11. 11. The process of claim 10, wherein the dissolved brominated polymer is a block copolymer of butadiene and styrene.

12. 2. The process of claim 1, wherein in step a), the organic solvent containing the quaternary ammonium or quaternary phosphonium tribromide is washed with an amount of the aqueous hydrazine solution sufficient to provide at least 0.5 moles of hydrazine per mole of quaternary ammonium or quaternary phosphonium tribromide in the organic solvent.