WO2009035836A1

WO2009035836A1 - A method for making n-2,3-dibromopropyl-4-5-dibromohexahydrophthalimide

Info

Publication number: WO2009035836A1
Application number: PCT/US2008/073793
Authority: WO
Inventors: Kimberly Ann Maxwell; Steven G. Karseboom; Jeffrey Todd Aplin; Ronny W. Lin; Arthur G. Mack; Jorge Morice; Saadat Hussain; Steven Alan Anderson; Christopher Chad Jameson; Neal James Colonius
Original assignee: Albemarle Corporation
Priority date: 2007-09-07
Filing date: 2008-08-21
Publication date: 2009-03-19
Also published as: TW200932724A

Abstract

The present invention relates to process technology suitable for producing, on a commercial scale, N-2,3-dibromopropyl-4,5-dibromohexahydrophthalimide.

Description

A METHOD FOR MAKING N-2,3-DLBROMOPROPYL-4,5-DLBROMOHEXAHYDROPHTHALIMIDE

FILED OF THE INVENTION

[0001] The present invention relates to process technology suitable for producing, on a commercial scale, N-2,3-dibromopropyl-4,5-dibromohexahydrophthalimide. BACKGROUND OF THE INVENTION

[0002] Over the years a number of brominated flame retardants have been developed for use in the polymer industry. These materials are blended into polymers that are used in a number of consumer goods such as the plastic cases of computers, insulation, television consoles, etc. Generally, however, even with the availability of a wide range of flame retardants, the polymer industry has increasingly demanded more and better flame retardants. Thus, there is continually a need in the art for flame retardant compositions and methods of making them. [0003] This invention provides process technology that is suitable for producing N-2,3- dibromopropyl-4,5-dibromohexahydrophthalimide ("tetraBr-THPAI") on a commercial scale with good performance characteristics. The process technology of this invention not only makes possible the production of tetraBr-THPAI in good yields under practical reaction conditions, but can also minimize, or in some embodiments avoid, the co-production of reactive impurities in the final product. The minimization, or in some embodiments elimination, of reactive impurities in the final tetraBr-THPAI product is one desirable feature of the present invention because these reactive impurities can adversely impact the performance of the tetraBr-THPAI product. For example, these impurities can release hydrogen bromide ("HBr") at lower temperatures than the tetraBr-THPAI product, which can lead to polymer degradation during the processing of the polymer and flame retardant. SUMMARY OF THE INVENTION [0004] In a first embodiment, the present invention relates to a process comprising:

A) bringing together cis-l,2,3,6-tetrahydrophthalic anhydride ("THPA"), allylamine, and optionally an organic solvent thereby forming a reaction mixture; and

B) maintaining the temperature of said reaction mixture at one or more temperatures in the range of from about 4O⁰C to about 100⁰C thereby forming a first reaction mass containing at least N-allyl-cis-1, 2,3, 6-tetrahydrophthalimide ("THPAI") and water;

C) removing at least a portion of the water from said first reaction mass thereby forming a second reaction mass;

D) continuously brominating at least a portion, preferably substantially all, of the THPAI in the second reaction mass at one or more temperatures in the range of from about - 4O⁰C to about 11O⁰C thereby forming a first product reaction mass containing tetraBr- THPAI and one or more brominated byproducts;

E) during D), continuously removing at least a portion, preferably substantially all, of any residual free bromine from the first product reaction mass thereby forming a second product reaction mass;

F) optionally, continuously treating the second product reaction mass to selectively convert at least a portion, preferably substantially all, of any reactive brominated byproducts into less reactive species thereby forming a third product reaction mass;

G) continuously isolating at least a portion, preferably substantially all, of the tetraBr- THPAI product in the third product reaction mass through i) crystallization, ii) precipitation, iii) solvent evaporation, in some embodiments through the use a devolatization extruder, or any combination of i)-iii); and optionally

H) continuously washing and drying the isolated tetraBr-THPAI product if it was isolated through crystallization or precipitation.

[0005] In preferred embodiments, especially when the tetraBr-THPAI product in the third product reaction mass is isolated through i) crystallization, and/or ii) precipitation in step F), optional step G) is also used. [0006] In a second embodiment, the present invention relates to a process comprising:

A) bringing together in a reactor a mixture containing THPA, allylamine an organic solvent, preferably monochlorobenzene ("MCB"), thereby forming a reaction mixture while maintaining the temperature of said reaction mixture at one or more temperatures in the range of from about 4O⁰C to about 100⁰C and the pressure at one or more pressures up to the pressure rating of the reactor thereby forming a first reaction mass containing at least N-allyl-cis-l,2,3,6-tetrahydrophthalimide ("THPAI") and water;

B) removing at least a portion of the water from said first reaction mass thereby forming a second reaction mass comprising at least THPAI;

C) continuously brominating at least a portion, preferably substantially all, of the THPAI in the second reaction mass at one or more temperatures in the range of from about - 4O⁰C to about HO⁰C thereby forming a first product reaction mass containing tetraBr- THPAI and one or more brominated byproducts while continuously removing at least a portion, preferably substantially all, of any residual free bromine from the first product reaction mass, preferably by contacting the first product reaction mass with aqueous sodium sulfite, sodium bisulfite, or sulfurous acid, thereby forming a second product reaction mass, in preferred embodiments comprising residual bromine, aqueous sodium sulfite, sodium bisulfite, and/or sulfurous acid while continuously treating the second product reaction mass with aqueous sodium carbonate at one or more temperatures in the range of from about 1O⁰C to 12O⁰C to selectively convert at least a portion, preferably substantially all, of any reactive brominated byproducts into less reactive species thereby forming a third product reaction mass;

D) continuously isolating at least a portion, preferably substantially all, of the tetraBr- THPAI product in the third product reaction mass through i) crystallization, ii) precipitation, iii) solvent evaporation such as through the use a devolatization extruder, or any combination of i)-iii); and optionally,

E) continuously washing and drying the isolated tetraBr-THPAI product if it was isolated through crystallization or precipitation.

(0007J In some embodiments, when removing at least a portion of the water from the first reaction mass, step C) in the first embodiment and B) in the second embodiment, of the present invention, described above, it is preferable to: 1) remove at least a portion, preferably substantially all, of any water that is produced in A), and/or B) and/or C) in the first embodiment, and/or 2) to remove at least a portion of, preferably substantial all, of any excess allylamine from the first reaction mass prior to brominating the second reaction mass; and/or optionally 3) to remove at least a portion, preferably substantially all, of any "heavies" from the second reaction mass prior to brominating the second reaction mass. By heavies, it is meant reaction by-products having a boiling point higher than the TI IPAl, [0008] It should be noted that water can, and is typically, generated while the first product reaction mass is heated to remove at least a portion of the water from the first product reaction mass. While not wishing to be bound by theory, the inventors hereof believe that this additional water generation is produced as the first reaction mass is heated and water is removed because heating and removal of water helps drive ring-closure and production of additional water, i.e. water other than that from A) and/or B). For what is meant by ring closure, please see the stepwise depiction of the alkylation reaction below where the "open ring" of the intermediate is closed to produce TI IPAI.

[0009] In some embodiments, when conducting A), only a portion of the allylamine is fed with the other reactants, and, once the reactor contents reach the desired temperature, in some embodiments one or more temperatures in the range of from about 4O⁰C to about 100⁰C, the remaining portion of the allylamine is fed in over time, preferably at a constant rate. It should be noted that the reaction(s) occurring in A) may be exothermic, and thus the heat removal capabilities of the reactor/vessel to which the allylamine is being fed should be taken into account when feeding the allylamine. For example, in some embodiments, feeding the allylamine at a rapid rate may not be feasible due to limited heat removal capabilities of the reactor/vessel to which the allylamine is being fed. In these embodiments, the rate at which the allylamine is fed can be adjusted to assist with maintaining the temperature at one or more temperatures within the range discussed above.

100 K)J In some embodiments, the at least a portion of any water removed from the first reaction mass is removed by Hashing or distillation, with or without a portion of the organic solvent,

[001 1 ] In some embodiments, the at least a portion of heavies are removed by distilling or flashing at least a portion, preferably substantially all, of the organic solvent, TIIPAI, and water overhead.

[0012J In some embodiments, when the organic solvent is monochlorobenzene ("MCB"), at least a portion of heavies removed can be separated by distilling or Hashing substantially all of the MCB, TI IPAI, and any remaining allylamine overhead, and at least a portion, preferably substantially all, of the allylamine, if any is present, can then be removed from the overhead via flashing or distillation.

[0013] In some embodiments, when treating the second product reaction mass to selectively convert at least a portion, preferably substantially all, of any reactive brominated byproducts, the pH is kept at one or more pϊTs in the range of from about 3 to about 11 so that a portion of any byproducts react at an appreciable rate but the tetraBr-THPAI decomposition rate is small.

[0014] In another embodiment, the present invention relates to a process for forming a tetraBr-THPAI product from THPA, MCB, and allylamine comprising:

A) introducing into a reactor THPA, MCB, and a portion of the allylamine;

B) maintaining the reactor contents at one or more temperatures in the range of from about 4O⁰C to about 100⁰C;

C) introducing into the reactor the remainder of the allylamine, preferably over time, thereby forming a first reaction mass;

D) removing at least a portion, preferably substantially all, of any water from the reaction mass via flashing or distillation, thereby forming a second reaction mass comprising at least THPAI;

E) brominating at least a portion, preferably substantially all, of the THPAI in the second reaction mass at one or more temperatures in the range of from about -4O⁰C to about HO⁰C thereby forming a first product reaction mass containing tetraBr-THPAI and one or more brominated byproducts;

F) removing at least a portion, preferably substantially all, of any residual free bromine from the first product reaction mass by contacting the first product reaction mass with aqueous sodium sulfite thereby forming a second product reaction mass containing residual bromine and aqueous sodium sulfite, sodium bisulfite, and/or sulfurous acid;

G) treating the second product reaction mass with aqueous sodium carbonate at one or more temperatures in the range of from about 3O⁰C to 100⁰C while maintaining the pH of the second product reaction mass at pH in the range of from about 4 to about 10.5, preferably in the range of from about 7 and about 9, thereby forming a third product reaction mass;

H) isolating at least a portion, preferably substantially all, of the tetraBr-THPAI product in the third reaction mass via precipitation using one or more aliphatic hydrocarbons; I) recovering at least a portion, preferably substantially all, of tetraBr-THPAI product via, for example, filtration; and J) washing and drying the isolated tetraBr-THPAI product, wherein A)-F) are conducted in a continuous or batchwise manner and G)-L) are conducted in a continuous manner.

[0015] In some embodiments of the present invention, the second reaction mass can be washed one or more times with water, preferably water having a pH in the basic range, prior to bromination. In these embodiments, the organic phase can be recovered, optionally washed one or more times, and brominated as described herein with reference to brominating the second reaction mass.

[0016] In some embodiments, at least a portion of any allylamine can be removed from the first reaction mass also. This is readily accomplished via flashing and distillation, and in some embodiments occurs as at least a portion of the water is removed from the first reaction mass. In other embodiments, any remaining allylamine is readily removed in the optional washing of the second reaction mass.

[0017] In some embodiments, the contents of the reactor are maintained at one or more pressures above atmospheric pressure.

[0018] In some embodiments, at least a portion of the THPA is introduced into the reactor, followed by addition of a portion of allylamine, and then the remainder of the THPA and allylamine are introduced into the reactor, preferably over time. If the processes of the present invention are operated in this manner, care should be taken such that there is not a substantial molar excess of allylamine relative to THPA in the reactor. The amount of precipitate formed should be kept to a minimum.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The inventors hereof believe, while not wishing to be bound by theory, that the production of tetraBr-THPAI products in the present invention can be described by the following reaction scheme:

Alkylation Reaction

Solvent,

cis-1 ,2,3,6-tetrahydrophthalic anhydride "THPA"

Heat

Bromination

Solvent

tetraBr-THPAI

Alkylation Reaction

[0020] In the practice of the present invention, a reaction mass containing N-allyl-cis-1,2,3,6- tetrahydrophthalimide ("THPAI") is formed by introducing into a reactor or bringing together cis-1 , 2,3,6-tetrahydrophthalic anhydride ("THPA"), allylamine, and optionally an organic solvent while the contents of the reactor are maintained at one or more temperatures in the range of from about 40⁰C to about 100⁰C. This reaction can be conducted in either a continuous or batchwise manner. The reaction mass containing N-allyl-cis- 1,2,3,6- tetrahydrophthalimide ("THPAI") is principally formed by alkylation of the starting THPA with allylamine.

[0021] After the addition of the components to the reactor, both optional and otherwise, at least a portion, preferably substantially all, of any water generated during the alkylation reaction is removed from the reaction mass. Allylamine

[0022] The amount of allylamine used in the practice of the present invention is generally in the range of from about 0.80 equivalents to about 6.00 equivalents of allylamine per equivalent of THPA, preferably in the range of from about 1.02 to about 1.50, and more preferably in the range of from about 1.10 to about 1.25, all on the same basis. [0023] If the allylamine is metered into the reactor, i.e. introduced into the reactor over time, at least a portion can be introduced at a temperature above about 3O⁰C and then to introduce the remainder of the allylamine once the reactor contents have reached the desired temperature. Further, the introduction of the allylamine can be used to control the reactor temperature. For example, because the alkylation reaction is exothermic, the allylamine can be introduced into the reactor at such a rate that the temperature of the reactor contents is maintained within the ranges described herein. Organic Solvent

[0024] The amount of organic solvent used in the practice of the present invention is generally in the range of from about 0.1 to about 20 volumes of organic solvent per volume of THPA charged, preferably in the range of from about 0.8 to about 10.0, more preferably in the range of from about 1.0 to about 2.5, on the same basis. More generally, when determining the amount of solvent to use consideration should be given to a) how thick the reaction slurry is and b) to overall reactor sizing. In the former, if the reaction mass is too thick to be stirred effectively, additional solvent should be added. In the latter, too much solvent leads to larger reactors and thus to greater capital requirements. If the THPA is soluble in the reaction solvent, generally less solvent will be required. If the THPA is added as a melt when at temperature even less solvent may be required. Likewise, if the temperature of the reactor contents is such that the contents are less viscous, then less solvent can be used.

[0025] The choice of which solvent(s) to use in the conversion of THPA to THPAI is largely guided by simplification of the process so long as the solvent(s) can easily be recycled. Non- limiting examples of suitable organic solvents include chlorobenzene, bromobenzene, toluene, xylenes, o-xylene, m-xylene, p-xylene, ethers such as methyl t-butyl ether, and esters such as ethyl acetate. Chlorobenzene has been found to be a good solvent because its use leads to few byproducts during the THPI to THPAI reaction and because it is relatively unreactive towards bromine for the conversion of THPAI to tetraBr-THP AI. This allows for a "one pot" process with no need to change the solvent used between the two chemical steps. Reaction Conditions

[0026] It is desirable to maintain reaction temperature during the alkylation reaction, i.e. step A) and/or B), at one or more temperatures in the range of from about 4O⁰C to about 100⁰C, preferably at one or more temperatures in the range of from about 5O⁰C to about 9O⁰C, preferably at one or more temperatures in the range of from about 6O⁰C to about 90⁰C. [0027] It is also desirable to maintain the pressure of the reactor such that the reaction mass is at or below its boiling point but certainly not more than the pressure rating of the reactor. However, when C) is conducted, it is desirable to maintain the pressure such that the at least a portion of any water sought to be removed is at or above the boiling point of water. Removal of Water From First Reaction Mass and Treatment of Second Reaction Mass [0028] After the alkylation reaction, at least a portion, preferably substantially all, of any water generated during the alkylation reaction is removed from the first reaction mass thereby forming a second reaction mass. At least a portion of any water can be removed by any technique known in the art, and the method selected is not critical to the instant invention. However, in preferred embodiments, at least a portion of any water is removed by heating the reactor contents to one or more temperatures above the boiling point of the water. In some embodiments, the reactor contents are heated to one or more temperatures in the range of up to about 150⁰C, preferably in the range of from about 100⁰C to about 15O⁰C when the reactor contents are maintained at atmospheric pressures. Thus, the water is removed via flashing or distillation; in some embodiments by heating the reactor contents to one or more temperatures such that the water turns into a gaseous phase that can be removed from the reactor, e.g. via an overhead stream. In some embodiments, the reactor contents of the first reaction mass are maintained under pressures greater than atmospheric pressures, and in these embodiments, at least a portion of the water can be removed by release of pressure and subsequently heating the reactor contents to one or more temperatures above the boiling point of water at that temperature.

[0029] The second reaction mass can optionally be washed with water one or more times prior to bromination. For example, the second reaction mass can be washed with water and the organic phase from this water washing step can be recovered via phase separation. This water washing of the organic phase can be conducted one or more times in the practice of the present invention until the desired amount of impurities are removed from the organic phase. It should be noted that it is within the scope of the present invention that the aqueous phase recovered via the phase separation during the washing of the organic phase and/or quenching of the reaction mass can be recovered and used as wash water and or quenching agents in further purification steps or production runs. The water used in these embodiments of the present invention preferably has a pH within the basic range.

[0030] Also, it is optional but desirable to remove at least a portion, preferably substantially all, of any remaining allylamine from the first reaction mass. If allyl-containing species are allowed to proceed through the process, bromine utilizations will suffer, e.g. the allylamine can react with bromine just like the THPAI will. Final product purity/performance may also suffer if excessive amounts of allylamine remain because of additional impurities that can be generated. The method used to separate the allylamine is dependent upon the specific reactants/reagents being used, but typically the allylamine can be readily removed via flashing or distillation techniques, preferably flashing, and thus this is typically achieved during the removal of at least a portion of the water from the second reaction mass. However, if any allylamine is present in the second reaction mass, the second reaction mass can be subjected to further flashing or distillation to remove at least a portion, preferably substantially all, of any allylamine remaining. For example, when MCB is used, at least a portion of the allylamine can be readily removed via a flash operation since the normal boiling point of allylamine is about 53⁰C while the normal boiling point of MCB is about 132⁰C. While a flash operation is desirable to remove the allylamine, the removal may also be accomplished via distillation. Distillation offers the possibility of reducing the total volume of recycle involved but may result in higher initial capital outlays. To improve utilizations, the material that is flashed or distilled overhead can be recycled into the next alkylation reaction. If the material is recycled, care should be taken to minimize the amount of free phase water and allylamine that are put back into the alkylation step. [0031] For example, at least a portion of the allylamine can be removed prior to or in conjunction with the water removal and prior to the optional washing of the second reaction mass and optional further purification of the recovered organic phase. However, if done in this manner, experiments should be conducted to confirm that any residual water carried forward into the process, i.e. the bromination of the THPAI reaction mass, does not adversely affect THPAI product performance and/or yield. [0032] Also, the second product reaction mass can be subjected to treatments to separate the THPAI in the second reaction mass and any remaining solvent from process "heavies". Non- limiting examples of suitable techniques for achieving this are flashing, distillation, and the like while the method chosen is dependent upon the specific system, For example, if MCB is used, MCB and THPAI may easily be separated from process heavies via a flash operation or distillation operation. It should be noted that it may be possible to separate the allylamine, MCB, and THPAI from process heavies via flash or distillation prior to the optional quench and wash steps described above, and this is within the scope of the present invention, although not recommended. The concern with conducting the process in this order is that the bottoms removed will be so thick due to the solids present that processing at commercial scale will be difficult, These problems could be alleviated to some extent by adding a very low volatility "chaser solvent" to the reaction mass prior to flashing/distilling, Further, similar derivations of the particularly preferred embodiment, such as distilling or flashing off allylamine, MCB, and THPAI from process heavies followed by flashing or distilling off allylamine from the resultant mixture, may be contemplated, and are within the scope of the present invention, although not recommended for commercial scale operations. [0033] It should also be noted that the distillation and/or flashing conducted on the second reaction mass can be conducted such that at least a portion of the allylamine is first removed and then at least a portion of water, solvent, heavies, etc. are removed from the second reaction mass. For example, the temperature can be increased over time such that the boiling point fractions can be recovered separately. For example, at least a portion, preferably substantially all, of the allylamine can removed since its boiling point is about 57⁰C, the allylamine-containing "stream" recovered, and the temperature increased to above the boiling point of water and the optional solvent and this stream recovered, etc. Bromination of THPAI Reaction Mass

[0034] Once the second reaction mass, containing THPAI, has been obtained, at least a portion, preferably substantially all, of the THPAI present in the second reaction mass is continuously brominated, usually with a slight excess, e.g. greater than about 2.0 molar equivalents bromine, to convert at least a portion, preferably substantially all, of the THPAI present in the second THPAI reaction mass to tetraBr-THPAI. It should be noted that even higher bromine levels of greater than about 2.16 bromine equivalents can be used. These higher bromine levels are preferred when MCB is used as a solvent because it is oftentimes difficult to induce crystallization of the tetraBr-THPAI in this embodiment even when the reaction mass is supersaturated with tetraBr-THPAI, and the addition of a larger excess of bromine increases the likelihood of crystallization.

[0035] It should be noted that the bromination reaction is exothermic, and it is desirable to meter in the bromine to match heat generation with heat removal capabilities. The bromine may be added in a number of ways including, but not limited to, as a neat liquid above the surface of the THPAI solution, as a neat liquid below the surface of the THPAI solution, as a solution in an unreactive solvent, such as chlorobenzene, either above or below the surface of the THPAI solution, as a neat vapor preferably below the surface of the THPAI solution, and as a component of a gaseous mixture preferably below the surface of the THPAI solution. For the latter, the components of the gaseous mixture should be selected such that they do not react with the bromine. One example of such a mixture would be bromine vapor in a nitrogen carrier gas. The addition of bromine is ideally done so that it is dispersed rapidly into the THPAI solution, for example atomized or as finely divided mist. This minimizes the potential to form locally high concentrations of bromine and/or hot spots, both of which may negatively impact product yields and purity/performance.

[0036] The temperature at which the bromination of the purified THPAI reaction mass is conducted is generally at one or more temperatures in the range of from about -4O⁰C to about 110⁰C, preferably at one or more temperatures in the range of from about 5O⁰C to about 8O⁰C. Brief excursions outside of this temperature range are possible and within the scope of the present invention, however, should there be a desire to operate outside of this range and especially on the higher side of these ranges, experiments should be conducted to determine the extent to which yields and final tetraBr-THPAI product purity/performance are affected. [0037] It should also be noted that it is preferred to add a free radical inhibitor such as, for example, butylated hydroxytoluene, to the purified THPAI reaction mass prior to bromination to suppress byproduct formation, which in turn will affect yields and may affect product purity and performance. Pyridine has been found to have some utility in this application. Workup of tetraBr-THP AI-Containing Product Mass

[0038] Following bromination of THPAI to tetraBr-THPAI, it is advantageous to remove at least a portion of any excess bromine from the reaction mass to reduce, preferably substantially eliminate, additional byproduct formation. It is preferred that this be done in a continuous manner also. Non-limiting examples of agents suitable for achieving the removal of at least a portion of excess bromine include reducing agents such as sodium sulfite, sodium formate, and hydrazine. Sodium sulfite reacts quickly with bromine and is relatively inexpensive so it is preferred in this invention. Due to ease of handling and increased reaction rate, it is further preferred to use an aqueous solution of sodium sulfite. [0039] The removal of the at least a portion of excess bromine can be conducted at wide range of temperature, but it is typically conducted at one or more temperatures in the range of up to about 80⁰C. If MCB is used as a solvent, it is often desirable to add the sodium sulfite solution at a temperature in the range of from about 3O⁰C to about 5O⁰C. [0040] It should be noted that in some circumstances the tetraBr-THPAI-containing product mass is typically a supersaturated solution of tetraBr-THPAI in MCB or as a thin slurry of tetraBr- THPAI in MCB even though solubility considerations alone dictate that more solids should be present. The addition of water (either neat or as a solution of sodium sulfite) can induce precipitation or additional precipitation depending upon the circumstances. If the sulfite solution is added below about 3O⁰C, the resultant slurry may be very thick which causes difficulty when stirring in commercial equipment; the increased solubility of tetraBr- THPAI above about 3O⁰C helps to keep the slurry reasonably thin. If it is desired to conduct the removal of the at least a portion of excess bromine at temperatures higher than about 8O⁰C, further experiments should be conducted to ensure that additional byproducts are not formed that deleteriously affect either yield or performance of the final tetraBr-THPAI product.

[0041] After at least a portion of any excess bromine has been removed, it is optional, but typically desirable and advantageous, to convert at least a portion, preferably substantially all, of any thermally unstable brominated by-product to a more stable species by the addition of a base. As with the bromination and removal of any excess bromine, it is preferred that this be done in a continuous manner. Non- limiting examples of suitable bases include sodium bicarbonate and potassium bicarbonate, preferably an aqueous solution of the base is used. In some embodiments the base is sodium carbonate, preferably aqueous sodium carbonate. The conversion of these brominated byproducts is desirable because some of these byproducts release hydrogen bromide at lower temperatures than tetraBr-THPAI. Since tetraBr-THPAI is typically processed with polymer at elevated temperatures, some of these impurities, if incorporated into the final tetraBr-THPAI product, may release HBr during that processing. The HBr may attack the polymer and reduce its molecular weight thereby adversely affecting the blended tetraBr-THPAI / polymer mix. If an aqueous base is used, it should be noted that phase separation can, and typically does occur, and the tetraBr-THPAI-containing organic phase can be recovered via ordinary phase separation techniques if so desired. In these embodiments, it is preferred to maintain the pH of the aqueous phase at one or more pH's in the range of from about 3 and to about 11 , preferably in the range of from about 7 and to about 10. It should be noted that at lower pH levels, the reactive brominated byproducts do not decompose as quickly as when higher pH's are used, but higher pH levels can cause the tetraBr-THPAI product to be attacked. The latter is especially a concern at elevated temperatures.

[0042] The removal of at least a portion of any brominated by-products is typically conducted at one or more temperatures chosen to consume the reactive byproducts but leave the tetraBr-THPAI largely unreacted. Generally, these temperatures are in the range of from about 10⁰C to 12O⁰C and preferably at one or more temperatures in the range of from about 4O⁰C to 75⁰C.

[0043] It should be noted that up until this point of the process the tetraBr-THPAI product remains largely, and sometimes completely, in solution depending upon the solvent system chosen and the concentration of the tetraBr-THPAI in that solution. Thus, after at least a portion of any excess bromine and at least a portion of any brominated by-products have been removed, at least a portion, preferably substantially all, of the tetraBr-THPAI product can be isolated, preferably continuously, from the tetraBr-THPAI product-containing-reaction mass by i) crystallization, ii) precipitation, iii) solvent evaporation, or any combination of i)-iii). [0044] In some embodiments, at least a portion of the tetraBr-THPAI product is recovered via crystallization and/or precipitation. In these embodiments, after at least a portion of any brominated by-products has been converted, one or more, typically one, antisolvent, i.e. a solvent that would facilitate the crystallization and/or precipitation of the tetraBr-THPAI product from solution, may be added to increase the yield of product. Non-limiting examples of antisolvents include aliphatic hydrocarbons such as petroleum ethers, cyclohexane, pentane, and heptane. Heptane or heptane-containing mixtures of hydrocarbons are preferred because 1) they are easy to separate from the MCB when solvent recycling is planned, 2) are not so volatile as to create special handling concerns, and 3) are and can increase the tetraBr- THPAI product yield by about 15% over a process that uses no antisolvent. It should be noted that if the solvent and antisolvent are to be recovered by distillation at the end of the process, it is advantageous if there is a large boiling point difference between the solvent and the antisolvent. Furthermore, the antisolvent chosen should not substantially react with the tetraBr-THPAI product.

[0045] The removal of at least a portion of excess bromine, optional conversion of at least a portion of any thermally unstable brominated by-products, and recovery of at least a portion of the tetraBr-THPAI product can be conducted either batch wise or continuously, independent of the bromination described above, i.e. if the bromination is conducted in a continuous manner, then these operations can still be conducted in a continuous or batchwise manner or vice versa. Further, each of these operations can itself be independently conducted in a batchwise or continuous manner from the others.

[0046] It should be noted that although the embodiment(s) described above depict the removal of at least a portion of any excess bromine followed by the removal of at least a portion of any brominated by-products, optionally followed by the addition of one or more antisolvent(s), the order of these can be changed depending upon the specific reagents being used if it benefits product quality, yield, and/or ease of operation. Furthermore, two or more of these steps may be combined into one if it is found to be advantageous. For example, if MCB is used as a solvent, aqueous sodium sulfite as the reducing agent, sodium carbonate as the base, and heptane as the antisolvent, it is advantageous to add a portion of the heptane after the sodium sulfite to aid in the precipitation of the product; the longer the product stays in a mix of chlorobenzene/heptane, the more likely it is to come out of solution as a powder. Although it would be advantageous, and within the scope of the present invention, to add the heptane even sooner, for example before at least portion of any excess bromine is removed or even before bromine is added to the THPAI solution, to realize these benefits, it is not advantageous because heptane may react with bromine, which would affect bromine utilizations and may affect product performance due to the introduction of new impurities. [0047] In some embodiments, the recovery of the at least a portion of the tetraBr-THPAI product is accompanied by the addition of tetraBr-THPAI product seed crystals to the tetraBr-THPAI product mass, if it benefits product quality, yield, and/or ease of operation. Ideally the seed crystals should be added at a point where the reaction mass is slightly saturated although adding them at other times may be contemplated.

[0048] After the tetraBr-THPAI product is precipitated and/or crystallized from the tetraBr- THPAI product mass, the tetraBr-THPAI product mass can be filtered to recover the tetraBr- THPAI product, which can be washed and dried. For washes in the MCB/heptanes solvent/antisolvent system, it is advantageous to wash with both water and heptanes. Water helps to reduce the levels of ionics (bromide, carbonate, bicarbonate, etc.) in the final product while heptanes help to increased final product purity by removing at least a portion of any remaining brominated byproducts.

[0049] In a particularly preferred embodiment, it is also advantageous to add water to the tetraBr-THPAI product containing reaction mass prior to filtration to further aid in reducing the level of ionics in the final tetraBr-THPAI product. This water may be added at any one of several different spots in the process including before addition of sodium sulfite, after addition of sodium sulfite, after addition of sodium carbonate, after addition of heptane antisolvent, etc.

[0050] Once filtered and washed, the tetraBr-THPAI product may be dried using one of several standard drying systems that exist commercially. Attention should be paid to the temperature at which the material is being dried especially when it is wet with water. If the temperature is too high, the water has the potential to react with the tetraBr-THPAI product or with impurities in the tetraBr-THPAI product to generate HBr. Such decomposition has the potential to adversely impact product performance. Generally the drying is conducted at one or more temperatures in the range of from about 1O⁰C to about 7O⁰C, preferably at one or more temperatures in the range of from about 3O⁰C to about 50⁰C. Other Methods of Isolating tetraBr-THPAI Product

[0051] Although it is preferred that the tetraBr-THPAI product be recovered via crystallization/precipitation, additional methods of isolation may be contemplated including, but not limited to, solvent evaporation. The tetraBr-THPAI product may be recovered via solvent evaporation, through the stripping of the solvent overhead or more preferably through a devolitization extruder where overall retention times will be minimized. The latter is important because the removal process will likely need to be carried out at temperatures where tetraBr-THPAI may decompose; short retention times will minimize any decomposition.

[0052] It should be noted that the recovery of the tetraBr-THPAI product via solvent evaporation provides for higher overall yields on a mass basis, the purities of the tetraBr- THPAI product will generally be lower when compared to tetraBr-THPAI products recovered via crystallization/precipitation.

[0053] If the tetraBr-THPAI product is recovered from the tetraBr-THPAI product containing reaction mass via solvent evaporation, it is still desirable to practice the conversion of brominated byproducts mentioned above to improve the performance of the final product. In this embodiment, following conversion of the brominated byproducts, it is advantageous to phase separate any aqueous layer away from the organic layer to limit the incorporation of ionics into the final tetraBr-THPAI product. Furthermore if MCB is used as the solvent, it is advantageous to add a hydrocarbon such as heptane to the MCB-containing organic phase. Depending upon conditions, two organic phases may develop, one rich in hydrocarbon and brominated byproducts and one rich in MCB and tetraBr-THPAI. Phase separating away the hydrocarbon/byproducts-rich phase prior to evaporation of solvent helps to purify the final tetraBr-THP AI product. An additional benefit of this separation is that the form that the final product takes is oftentimes more of a solid than a highly viscous liquid; the byproducts that are removed in the heptane-rich phase seem to hinder the product from fully solidifying. [0054] The above description is directed to several embodiments of the present invention. Those skilled in the art will recognize that other means, which are equally effective, could be devised for carrying out the spirit of this invention. It should also be noted that preferred embodiments of the present invention contemplate that all ranges discussed herein include ranges from any lower amount to any higher amount.

[0055] The following example will illustrate the present invention, but are not meant to be limiting in any manner.

EXAMPLES EXAMPLE 1 The Alkylation

[0056] A 4-neck 500 mL jacketed flask fitted with nitrogen flow and a water-cooled reflux condenser was charged with 50 g chlorobenzene and 50 g (0.329 mol) of tetrahydrophthalic anhydride (THPA, 95-96%). The mixture was heated to 50 ⁰C and stirred (200 rpm) for 20 min to dissolve THPA. A circulating bath set to 30 ⁰C was applied to the reactor jacket. To the stirred (300 rpm) solution, allylamine (20.6 g, 0.361 mol, 1.1 eq) was added over 12 min drop-wise via an addition funnel. The reaction was exothermic, and the temperature rose from 48 °C to 64 ⁰C.

[0057] The circulating bath fluid temperature was increased to 150 ⁰C, and distillation commenced after 15 min when the reaction temperature reached 124-125 ⁰C. After 30 min, the circulating bath fluid was increased to 160 ⁰C, and the reaction temperature rose to 139 ⁰C over 25 min. After another 15 minutes of stirring, the distillation rate slowed, and the reaction temperature continued to rise to 142 ⁰C over 25 min. After 10 min, vacuum was applied for 10 min to assist distillation, and the reaction temperature rose to 151 ⁰C over 30 min. The last GC sample, 93.5 area% xjjp/j was analyzed. The circulating bath fluid temperature was then increased to 165 ⁰C, and vacuum was applied again. Chlorobenzene (21 g) was added to replace loss of solvent during distillation. EXAMPLE 2

[0058] A 4-neck 5 L jacketed flask fitted with nitrogen flow and a water-cooled reflux condenser was heated to 50 ⁰C using fluid circulating bath. The flask was charged with 1.36 kg xylenes and 1.36 kg (8.94 mol) of tetrahydrophthalic anhydride (THPA, 95-96%). A circulating bath set to 30 ⁰C was applied to the reactor jacket. To the stirred (300 rpm) solution, allylamine (561 g, 9.83 mol, 1.1 eq) was added over 1 hour drop-wise via an addition funnel. The reaction was exothermic, and the temperature rose to 57.3 ⁰C after 28 min. The circulating bath fluid temperature was increased to 80 ⁰C. After the allylamine addition was complete (1 hour), the bath temperature was increased to 150 ⁰C, and allylamine/water/xylenes were removed by distillation. After 1.3 hours, the circulating bath fluid temperature was increased to 160 ⁰C, and solvent was removed using a vacuum aspirator. After 25 minutes, the reaction temperature rose to 144 ⁰C. After 2.5 h, the reaction was cooled to 50 ⁰C. Cyclohexane (1.2 kg) was added, and the organic phase was washed twice with aqueous sodium carbonate (715 g water, 55 g sodium carbonate) and once with water (715 g). The organic phase was separated and cyclohexane removed by vacuum distillation. The final product contained 99.5 GC area% THPAI.

Claims

WHAT IS CLAIMED

I) A process comprising:

A) bringing together cis-l ,2,3,6-tetrahydrophthalic anhydride ("THPA"), allylamine, and optionally an organic solvent thereby forming a reaction mixture; and

B) maintaining the temperature of said reaction mixture at one or more temperatures in the range of from about 4O⁰C to about 100⁰C thereby forming a first reaction mass containing at least N-allyl-cis-1, 2,3,6- tetrahydrophthalimide ("THPAI") and water;

D) continuously brominating at least a portion, preferably substantially all, of the THPAI in the second reaction mass at one or more temperatures in the range of from about -4O⁰C to about 11O⁰C thereby forming a first product reaction mass containing tetraBr-THPAI and one or more brominated byproducts;

G) continuously isolating at least a portion, preferably substantially all, of the tetraBr-THPAI product in the third product reaction mass through i) crystallization, ii) precipitation, iii) solvent evaporation, in some embodiments through the use a devolatization extruder, or any combination of i)-iϋ); and optionally

2) The process according to claim 1 wherein said process includes F); H); or F) and H).

3) The process according to claim 1 wherein the at least a portion of water removed in C) is removed via any one of a) flashing, b) distillation, or c) heating the reactor contents to one or more temperatures above the boiling point of the water at the pressure of the reactor.

4) The process according to claim 3 wherein C) is conducted at atmospheric pressures and the at least a portion of water is removed by heating the reactor contents to one or more temperatures of a) up to about 150⁰C or b) in the range of from about 100⁰C to about 150⁰C, wherein when the reactor contents are maintained at atmospheric pressures.

5) The process according to claim 1 wherein the tetraBr-THPAI product in the third product reaction mass is isolated through i) crystallization, and/or ii) precipitation.

6) The process according to claim 1 wherein said at least a portion of any residual free bromine is removed from the first product reaction mass by contacting the first product reaction mass with aqueous sodium sulfite, sodium bisulfite, or sulfurous acid.

7) The process according to claim 1 wherein when conducting C), i) at least a portion of any water that is produced in A) and/or B) and/or C) is removed, and/or ii) at least a portion of any excess allylamine from the first reaction mass is removed prior to D); and/or optionally iii) at least a portion of any reaction by-products having a boiling point higher than the THPAI are removed from the second reaction mass prior to step D).

8) The process according to claim 1 wherein when conducting A), only a portion of the allylamine is brought together with the other reactants, and, once the reactor contents reach the desired temperature, the remaining portion of the allylamine is fed in over time; or at least a portion of the THPA is brought together with at least a portion of allylamine, and then the remainder of the THPA and allylamine are introduced over time.

9) The process according to claim 8 wherein said desired temperature is one or more temperatures in the range of from about 4O⁰C to about 100⁰C, and said remaining portion of allylamine is introduced at a constant rate.

10) The process according to claim 3 wherein at least a portion of any organic solvent is removed with the at least a portion of water.

1 1) The process according to claim 7, wherein said process includes iii), and said at least a portion of said at least a portion of any reaction by-products having a boiling point higher than the THPAI are removed by distilling or flashing at least a portion of any organic solvent, THPAI, and water overhead. 12) The process according to claim 2 wherein said organic solvent is monochlorobenzene ("MCB") and said at least a portion of heavies removed are removed by distilling or flashing substantially all of the MCB, THPAI, and any remaining allylamine overhead.

13) The process according to claim 12 wherein at least a portion of the allylamine is removed from the overhead via flashing or distillation and/or wherein at least a portion of any excess allyamine is removed from the first reaction mass via flashing or distillation.

14) The process according to claim 1 wherein when treating the second product reaction mass to selectively convert at least a portion of any reactive brominated byproducts, the pH of the second product reaction mass is maintained at one or more pH's in the range of from about 3 to about 1 1.

15) The process according to claim 1 wherein the amount of organic solvent used is i) in the range of from about 0.1 to about 20 volumes of organic solvent per volume of THPA; H) in the range of from about 0.8 to about 10 volumes of organic solvent per volume of THPA; or Ui) i) in the range of from about 1 to about 2.5 volumes of organic solvent per volume of THP A.

16) The process according to claim 1 wherein: ia) the THPA is a melt; ib) the amount of bromine used in D) is 2 or more equivalents of bromine per equivalent of THPAI; ic) A) is conducted at one or more pressures above atmospheric pressure; id) any combination of one or more of ia), ib) and ic).

17) The process according to claim 1 wherein the removal of at least a portion of any brominated by-products is accomplished by the addition of a base or an aqueous base, and then recovering the tetraBr-THPAI product containing organic phase.

18) The process according to claim 17 wherein a) the pH of the aqueous phase is maintained at one or more pH's in the range of from about 3 and to about 1 1; b) the removal of at least a portion of any brominated by-products is conducted at one or more temperatures in the range of from about 1O⁰C to 12O⁰C; or c) combinations of a) and b).

19) The process according to claim 1 wherein a free radical inhibitor is added to the second reaction mass prior to D).

20) The process according to claim 19 wherein said free radical inhibitor is butylated hydroxytoluene.

21) The process according to claim 1 wherein the second reaction mass is washed one or more times with water prior to D), the solution thus formed allowed to phase separate, the organic phase recovered and optionally washed one or more times with water, and then brominated in D). 22) The process according to claim 21 wherein said water has a pH in the basic range.

23) The process according to claim 8 wherein the THPA and allylamine are brought together in such as manner that there is not a substantial molar excess of allylamine relative to THPA.

24) A process comprising:

A) bringing together in a reactor a mixture containing THPA, allylamine, and an organic solvent, thereby forming a reaction mixture while maintaining the temperature of said reaction mixture at one or more temperatures in the range of from about 4O⁰C to about 100⁰C and the pressure at one or more pressures up to the pressure rating of the reactor thereby forming a first reaction mass containing at least N-allyl-cis- 1,2,3,6-tetrahydrophthalimide ("THPAI") and water;

B) removing at least a portion of the water from said first reaction mass by heating the first reaction mass to one or more temperatures above the boiling point of the water at the pressure of the reactor thereby forming a second reaction mass comprising at least THPAI;

C) continuously brominating at least a portion of the THPAI in the second reaction mass at one or more temperatures in the range of from about -4O⁰C to about 110⁰C thereby forming a first product reaction mass containing tetraBr-THPAI and one or more brominated byproducts while continuously removing at least a portion of any residual free bromine from the first product reaction mass thereby forming a second product reaction mass while continuously treating the second product reaction mass with aqueous sodium carbonate at one or more temperatures in the range of from about 1 O⁰C to 12O⁰C to selectively convert at least a portion of any reactive brominated byproducts into less reactive species thereby forming a third product reaction mass;

D) continuously isolating at least a portion, preferably substantially all, of the tetraBr- THPAI product in the third product reaction mass through i) crystallization, ii) precipitation, iii) solvent evaporation such as through the use a devolatization extruder, or any combination of i)-iϋ); and optionally,

E) continuously washing and drying the isolated tetraBr-THPAI product from D).

25) The process according to claim 24 wherein the organic solvent is monochlorobenzene ("MCB") and/or wherein said process includes E).

26) A process for forming a tetraBr-THPAI product from THPA, MCB, and allylamine comprising: A) introducing into a reactor THPA, MCB₅ and a portion of the allylamine;

E) brominating at least a portion, preferably substantially all, of the THPAI in the second reaction mass at one or more temperatures in the range of from about -4O⁰C to about 110⁰C thereby forming a first product reaction mass containing tetraBr-THPAI and one or more brominated byproducts;

H) isolating at least a portion, preferably substantially all, of the tetraBr-THPAI product in the third reaction mass via precipitation using one or more aliphatic hydrocarbons;

I) recovering at least a portion, preferably substantially all, of tetraBr-THPAI product via, for example, filtration; and

J) washing and drying the isolated tetraBr-THPAI product, wherein A)-F) are conducted in a continuous or batchwise manner and G)-L) are conducted in a continuous manner and the second reaction mass is optionally washed one or more times with water prior to E).

27) The process according to claim 26 wherein i) A)-F) and G)-L) are conducted in a continuous manner; ii) a free radical inhibitor is added to the second reaction mass prior to E); iii) combinations of i) and ii).

28) The process according to claim 27 wherein said free radical inhibitor is butylated hydroxytoluene.