WO2012088184A1

WO2012088184A1 - Integrated processes for the preparation of heterocyclic aromatic polymer precursors

Info

Publication number: WO2012088184A1
Application number: PCT/US2011/066303
Authority: WO
Inventors: Rajiv Dhawan; Joachim C. Ritter
Original assignee: E. I. Du Pont De Nemours And Company
Priority date: 2010-12-20
Filing date: 2011-12-20
Publication date: 2012-06-28

Abstract

An integrated process is provided for efficiently preparing 2, 4, 5-triaminothiophenol, starting; high purity salts thereof; and complexes of 2, 4, 5-triaminothiophenol with aromatic diacids, which are precursors for making polymer for high performance fibers. The process design eliminates several costly intermediate drying and recrystallization steps. The handling of solid materials with possible skin sensitizing properties and toxicity is avoided, thereby eliminating human and environmental exposure.

Description

TITLE

INTEGRATED PROCESSES FOR THE PREPARATION OF HETEROCYCLIC AROMATIC POLYMER PRECURSORS

FIELD OF DISCLOSURE

The disclosure relates to methods of making 2 , 4 , 5-triaminothiophenol and salts and complexes thereof, with are then used to make high-performance heterocyclic aromatic polymers.

BACKGROUND

Aromatic amines and phenols are useful monomers for high performance polymers such as aramid polymers and heterocyclic aromatic polymers (e.g., polybenzimidazoles ) . Monomer structure affects both finished article properties, such as fiber tenacity, and the rheological behavior of the polymer during processing such as spinning. Asymmetric monomers, as opposed to highly symmetric ones such as 1,2,4,5- tetraaminobenzene, are desired to increase the

solubility of the corresponding polymers for improved fiber spinning. The synthesis of the preferred

heterocyclic aromatic polymer for high performance fibers then requires the selective polymerization of an asymmetric monomer, such as 2 , 4 , 5-triaminothiophenol ("TATHIO") , with various substituted and unsubstituted aromatic diacids, such as 2 , 5-dihydroxyterephthalic acid ("DHTA") . However, no synthetic route has been identified for making TATHIO and related compounds. There remains a need for a process for the safe and efficient production of high-purity 2,4,5- triaminothiophenol (TATHIO) (Formula I)

and salts of 2 , 4 , 5-triaminothiophenol that can be converted to 2 , 4 , 5-triaminophenol , to make an aromatic diacid complex of 2 , 4 , 5-triaminothiophenol of high enough purity for use in making a high molecular weight polymer material for producing high-performance fibers. For reasons of cost and safety, it would be highly desirable to have a process where intermediates do not need to be isolated as dry materials.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example and not limitation in the accompanying figures

FIGURE 1 is a schematic representation of an embodiment of the process described herein for

preparing TATHIO and TATHIO hydrochloride salt.

FIGURE 2 is a schematic representation of an embodiment of the process described herein for

preparing TATHIO complex. DESCRIPTION

The following description is exemplary and explanatory only and is not restrictive of the

invention, as defined in the appended claims.

In one embodiment of this invention, an integrated process comprising the sequential steps under exclusion of oxygen:

(a) nitration of 1 , 3-dihalobenzene (Formula II)

wherein each Z is independently CI or Br, in a reaction mixture comprising oleum or SO₃, nitric acid, and H₂S0₄

wherein

(i) the concentration of nitric acid is about 2.0 to about 2.3 moles per mole of 1 , 3-dihalobenzene ;

(ii) the concentration of SO₃ is about 1 to about 3 moles per mole of 1 , 3-dihalobenzene ;

(iii) the concentration of 1 , 3-dihalobenzene in the reaction mixture is between about 12 and about 24 weight percent; and

wherein the temperature of the reaction mixture does not exceed 120°C;

thereby producing 1 , 3-dihalo-4 , 6-dinitrobenzene (Formula III) ;

(b) directly separating the 1 , 3-dihalo-4 , 6- dinitrobenzene from the reaction mixture by filtration, while recycling the sulfuric acid mother liquor;

(c) washing the 1 , 3-dihalo-4 , 6-dinitrobenzene with water or acid then water, then with aqueous ammonia, and then mixing it with solvent as a suspension;

(d) monoaminating the 1 , 3-dihalo-4 , 6- dinitrobenzene by heating the suspension formed in step (c) to a temperature in the range of about 60°C to about 140°C and contacting it with at least 2.0 equivalents N¾, thereby converting the

1 , 3-dihalo-4 , 6-dinitrobenzene to l-amino-3-halo- 4,6- dinitrobenzene (Formula IV);

(e) directly separating the l-amino-3-halo-4 , dinitrobenzene from the reaction mixture by filtration, washing with solvent, then washing with water;

(f) forming a slurry of the l-amino-3-halo-4 , dinitrobenzene with methanol and at least 1.0 equivalent of t-butylthiol (

, "tBuSH" ) in aqueous NaOH, thereby converting the l-amino-3- halo-4 , 6-dinitrobenzene to l-t-butylthio-3-amino- 4 , 6-dinitrobenzene (Formula V) ;

(g) directly separating the 1- (t-butylthio) -3- amino-4 , 6-dinitrobenzene formed in step (f) from the reaction mixture by filtration;

(h) forming a slurry of the 1- (t-butylthio) -3- amino-4 , 6-dinitrobenzene separated in step (g) with water and transferring the slurry to a hydrogenation reactor containing a hydrogenation catalyst to form a reaction mixture;

(i) hydrogenating the 1- (t-butylthio) -3-amino- 4 , 6-dinitrobenzene in water by contacting the reaction mixture formed in step (h) with hydrogen at a pressure in the range of about 10 to about 1000 psi (about 0.069 MPa to about 6.89 MPa) and temperature in the range of about 50 °C to about 100°C for sufficient time to hydrogenate the 1-t- butylthio-3-amino-4 , 6-dinitrobenzene, thereby producing a suspension comprising 5- (t-butylth 1 , 2 , 4-triaminobenzene (Formula VI);

(j) cooling the reaction mixture to a temperature in the range of about 30°C to about 40°C and contacting the reaction mixture with an aqueous solution comprising 1 to 2 equivalents of HC1 per mol of 5- (t-butylthio) -1 , 2 , 4-triaminobenzene optionally containing 0.005 -0.05 equivalents of a SnCl₂ and, optionally, heating the solution, thereby converting the 5- (t-butylthio) -1 , 2 , 4- triaminobenzene to 2 , 4 , 5-triaminothiophenol salt;

(k) filtering the reaction mixture, thereby removing the spent hydrogenation catalyst;

(1) optionally, passing the filtered reaction mixture through a carbon bed;

(m) adjusting the pH of the filtered reaction mixture to a value above about 7 by adding base and

(n) isolating the 2 , 4 , 5-triaminothiophenol free base by filtration.

In a second embodiment, an integrated process for preparing 2 , 4 , 5-triaminothiophenol salt comprises steps (a) through (n) and further comprises (o) washing the 2 , 4 , 5-triaminothiophenol free base with water to produce a water-wet free base that is about 40 to about 60% water by weight;

(p) combining the water-wet free base with about 5 to about 10 equivalents of aqueous and gaseous

HC1 solution, optionally saturated with gaseous HC1, so that the ratio of TATHIO free base to HC1 to water is about 15-25 to 25-35 to 45-55 parts by weight, thereby forming and precipitating 2,4,5- triaminothiophenol hydrochloride salt;

(q) filtering the 2 , 4 , 5-triaminothiophenol hydrochloride salt and washing it with

concentrated aqueous HC1;

(r) combining the wet 2 , 4 , 5-triaminothiophenol hydrochloride salt with 5-10 equivalents aqueous concentrated HC1 and heating to 70°C -100°C with an optional HC1 stream to remove t-butylchloride byproduct ;

(s) and filtering, washing, and drying the precipitated 2 , 4 , 5-triaminothiophenol salt.

In a third embodiment, an integrated process is provided for preparing a complex of 2,4,5- triaminothiophenol and an aromatic diacid HOOC-Q-COOH, wherein the complex is generally described by Formula VII,

wherein Q is a C6--C20 monocyclic or polycyclic aromatic nucleus, by the above described process for preparing the 2 , 4 , 5-triaminothiophenol salt, further comprising dissolving the washed product in water, and adding a weak base (for example, KHCO₃ or NaHCOs) and a diacid source to form the complex.

In a further embodiment, the complex is prepared by directly contacting the filtered, reaction mixture formed in step (1) with a weak base, such as aHC03 or KHCO3, and a diacid source, to form the complex. In yet another embodiment, the TATHIO free base precipitated in step (m) can then be dissolved in about 1-2 equivalents of acid (e.g., HC1) and the solution so produced contacted with a weak base (such as aHC03 or KHCO3) and a diacid source to form the complex .

A reducing agent such as tin powder (Sn) or SnCl₂ may be added to TATHIO, TATHIO salt, or TATHIO complex at various points in the process to prevent or reverse oxidation.

In the context of this disclosure, a number of terms shall be utilized.

As used herein, the term "TATHIO" or, equivalently, "TATHIO free base" denotes the compound 2 , 4 , 5-triaminothiophenol (Formula I)

As used herein, the term "TATHIO salt" or, equivalently, "2 , 4 , 5-triaminothiophenol salt," or

"TATHIO -nA" denotes a compound formed by reaction of 2, 4, 5-triaminothiophenol ("TATHIO") with "n"

equivalents of an acid ("A") such as HC1, acetic acid, H₂S0₄, or H₃PO₄. One example of a TATHIO salt is

TATHIO · 3HC1 (n=3, A=HC1). The salt may also be a hydrate; one such example is TATHIO · 3HC1 · x¾0. The acid name may also be incorporated into the name of the salt, so that, e.g., TATHIO-nHCl can be referred to as "2 , 4 , 5-triaminothiophenol hydrochloride salt" or

"TATHIO hydrochloride." Where n is known, it can be incorporated as well; for example, TATHIO- 3HC1 can also be referred to as "2 , 4 , 5-triaminothiophenol

trihydrochloride salt" or "TATHIO trihydrochloride . "

As used herein, the term "weak base" refers to a base having a base dissociation constant (also referred to as "ionization constant") K_b that is less than 1 at 25°C. Some examples are acetate ion 0¾000^~, ammonia, and bicarbonate ion, HC03^~

As used herein the term "diacid source" refers to the diacid HOOC-Q-COOH itself, a disodium salt of HOOC-Q-COOH, a dipotassium salt of HOOC-Q-COOH, or mixtures thereof.

As used herein, the term "XYTA" denotes 2-X- 5-Y-terephthalic acid, where X and Y each independently selected from the group consisting of H, OH, SH, SO₃H, methyl, ethyl, F, CI, and Br. One example is 2,5- dihydroxyterephthalic acid, in which X=Y=OH. The disodium or dipotassium salt of the diacid is

represented by the term "M₂XYTA" where M is Na or K. As used herein, the term "oleum" denotes fuming sulfuric acid, which is anhydrous and is formed by dissolving excess sulfur trioxide (SO₃) into

sulfuric acid.

As used herein, the term "fuming nitric acid" denotes concentrated nitric acid containing dissolved nitrogen dioxide.

As used herein, the term "net yield" of P denotes the actual, in-hand yield, i.e., the

theoretical maximum yield minus losses incurred in the course of activities such as isolating, handling, drying, and the like.

As used herein, the term "purity" denotes what percentage of an in-hand, isolated sample is actually the specified substance.

The processes are designed in such a way that solids handling is avoided. Filtered materials are transferred, without prior drying, in the form of suspension slurries in the solvent that is used for the respective reaction step. This process design thereby avoids costly drying processes. It also avoids the handling of solid materials with possible skin

sensitizing properties and toxicity, and eliminates human and environmental exposure to them.

An embodiment of the process described herein to make TATHIO free base or TATHIO salt is illustrated in Figure 1; possible minor modifications will be evident to one skilled in the art. With reference to the embodiment shown schematically in Figure 1, the process starts with the nitration 1 of 1,3- dihalobenzene (i.e., 1 , 3-dichlorobenzene, 1,3- dibromobenzene, or l-bromo-3-chlorobenzene; 1,3- dichlorobenzene is preferred) , in a reaction mixture prepared by combining the 1 , 3-dihalobenzene 2, oleum 3, and nitric acid 4. The concentration of nitric acid is about 2.0 to about 2.3 moles per mole of 1,5- dihalobenzene . Concentrated nitric acid (e.g.,

commonly used reagent grade, which is about 70% nitric acid in water) can be used, but fuming nitric acid is preferred. If concentrated nitric acid is used, since in the process described herein water must be kept at a level below one equivalent to get highly pure product, more SO₃ would be added to remove the water from the nitric acid (by reacting with it to form sulfuric acid) and still have sufficient SO₃ present in the reaction mixture for the nitration reaction. The concentration of SO₃ is about 1 to about 3 moles, preferably 1.5 to 2 moles, per mole of 1 , 3-dihalobenzene . The sulfuric acid is present in an amount such that the weight percent of 1 , 3-dihalobenzene in the reaction mixture (i.e., the weight of 1 , 3-dihalobenzene relative to the combined weight of 1 , 3-dihalobenzene plus the acid solution) is between 12 and 24 weight percent.

The nitration reaction is carried out at a temperature not to exceed about 120°C, typically in the range of about 5°C to about 100°C, preferably in the range of about 5°C to about 40°C, and more preferably in the range of about 5° to about 15°C. The 1,3- dihalo-4 , 6-dinitrobenzene thereby produced is separated directly by filtration 5 from the reaction mixture as a crude crystal cake without quench or recrystallization steps. The crude crystal cake is washed (6) with water. Aqueous waste is discarded. The sulfuric acid mother liquor is recycled 7, with a purge drawn to prevent excess sulfuric acid accumulation. The resulting wet cake of 1 , 3-dihalo-4 , 6-dinitrobenzene is then mixed with solvent 8 and introduced into the amination reactor 9 as a suspension. A solvent suitable for use includes an organic solvent inert to the reaction such as an aliphatic dihydric alcohol such as ethylene glycol ("glycol") .

The suspension is heated to a temperature in the range of about 60°C to about 140°C, preferably about 130°C, to dissolve the 1 , 3-dihalo-4 , 6- dinitrobenzene in the solvent. The resulting solution is contacted at that temperature with aqueous ammonia in solvent (e.g., glycol) 10 for approximately two to four hours close to ambient pressure; the ammonia solution is fed as it is consumed, as indicated by any convenient analytical technique (e.g., pH monitoring or gaseous ammonia flow rate) . At least 2, preferably about 2.03 to about 2.07, equivalents of ammonia are required. At reaction completion, the l-amino-3-halo- 4 , 6-dinitrobenzene ("AHDNB") thereby produced can be directly isolated from the reaction mixture since it is only sparingly soluble in aliphatic dihydric alcohol such as glycol at temperatures below 50°C; impurities remain in solution, and net yields of 85% have been found at greater than 98% purity for l-amino-3-chloro- 4 , 6-dinitrobenzene specifically. The AHDNB is filtered 11, typically at about 60°C, and washed with solvent or water 12. The mother liquor (filtrate) is collected 13, and the solvent is distilled and recycled; purges are drawn to prevent accumulation.

The wet cake of l-amino-3-halo-4 , 6- dinitrobenzene is slurried with methanol 14. A

solution of t-butylthiol in about one to about two equivalents of aqueous base (e.g., NaOH) is added 15. The 1- ( t-butylthio) -3-amino-4 , 6-dinitrobenzene thereby produced ("thiolation") as a water-wet cake 16 is isolated by filtration 17, washed with aqueous NaOH and water, slurried with water 18, and transferred to the hydrogenation reactor 19 as a suspension.

The hydrogenation reactor also contains a hydrogenation catalyst 20. Examples of suitable hydrogenation catalysts include without limitation Pd/C and Pt/C and mixtures thereof, optionally containing other metals from Groups VIII through X such as Fe . The groups are as described in the Periodic Table in Advanced Inorganic Chemistry by F. A. Cotton and G. Wilkinson, Interscience New York, 2nd Ed. (1966) . Of these, Pt/C, and Pd/C, e.g., 10% Pt/C and 10% Pd/C, are preferred. The catalyst is typically used in the amount of about 0.5 to about 5.0 wt% metal based on 1- ( t-butylthio) -3-amino-4, 6-dinitrobenzene.

The hydrogenation reactor is purged with nitrogen and then hydrogen. Deaerated water 21 is then added to the reactor. The aqueous suspension is contacted with hydrogen 22 to form a reaction mixture at a pressure in the range of about 10 to about 1000 psi (about 0.069 MPa to about 6.89 MPa) and a

temperature in the range of about 50°C to about 100°C for sufficient time to hydrogenate the 1- (t-butylthio) - 3-amino-4 , 6-dinitrobenzene, thereby producing a

suspension comprising 5- (t-butylthio) benzene-1 , 2 , 4- triamine (Formula VI) . The reaction is carried out at a temperature in the range of about 50 °C to about

100°C, and a hydrogen pressure in the range of about 10 to about 1000 psi (about 0.069 MPa to about 6.89 MPa). Reaction continues for a time sufficient to consume about 5.9 to 6.5 mol equivalents of hydrogen, thereby producing a suspension comprising 5- (t- butylthio) benzene-1 , 2 , 4-triamine (Formula VI). The time required depends on the details of the specific set up but is typically about 2 to 3 hours.

The reaction mixture is cooled to a temperature in the range of about 25°C to about 45°C. About 1 to about 2 equivalents of at least 20 wt% HC1 per mol of 5- (t- butylthio) -1 , 2 , 4-triaminobenzene, optionally containing a reducing agent such as 0.005 to 0.05 equivalents of SnCl₂, is added 23 to the reaction mixture. The reaction mixture is heated to a temperature between about 60 °C and about 120 °C, in one embodiment between about 80°C and about 120°C, for a time sufficient to convert the 5- (t-butylthio) -1 , 2 , 4-triaminobenzene to 2 , 4 , 5-triaminothiophenol hydrochloride. The resulting reaction mixture is filtered 24, typically at a

temperature in the range of about 60 °C to about 80 °C, to remove the spent hydrogenation catalyst preferably by passing through a carbon filter bed. The spent catalyst can then be recycled 25.

The TATHIO free base can then be formed from the reaction mixture remaining after filtration and

extraction, by addition of base 26 (e.g., NaOH or KOH) to adjust the pH to a value above about 7, thereby precipitating the TATHIO free base 27. The TATHIO free base can then be isolated by filtration, washed, and dried if so desired.

Alternatively, to make the TATHIO

hydrochloride salt, e.g., TATHIO-3HC1, as in the embodiment shown in Figure 1, the TATHIO free base is filtered 28, and combined with water 29 to produce a water-wet free base that is about 40 to about 60% water by weight. The water-wet free base is then combined with about 5 to about 10 equivalents of aqueous and gaseous HCl solution 30, optionally saturated with gaseous HCl. The acid is added at a temperature in the range of about 10°C to about 50°C. The ratio of TATHIO free base to HCl to water is about 15-25 to 25-35 to

45-55 parts by weight. In one embodiment, the ratio is 20 parts TATHIO to 30 parts HCl to 50 parts water. The 2 , 4 , 5-triaminothiophenol hydrochloride salt is thereby formed and precipitates 31.

The use of gaseous acid, such as gaseous HCl, might reduce the total volume of liquid needed since the additional introduction of water with aqueous acid in both addition steps increases the absolute

solubility of the TATHIO salt in the filtered reaction mixture. The addition of equivalent amounts of acid in the gas phase instead of as an aqueous solution (for example, HCl_gas instead of HCl_aq) may be also desirable since the liquid volumes are thereby reduced, and crystallization yields are expected to be higher as a consequence. More commonly, however, aqueous acid (for example, 30-38 wt% HCl) is used because it is easier to handle than the acid in the gas phase. Aqueous acid can be recovered, distilled, and recycled or used in the acid wash step 33 of the process. To facilitate the precipitation of the TATHIO salt (for example, as TATHIO- 3HC1) an aliphatic alcohol co-solvent may optionally be added. Examples of suitable alcohol co- solvents included without limitation: methanol,

ethanol, n-propanol, and isopropanol.

The reaction mixture containing the precipitated TATHIO hydrochloride salt 31 is then cooled to room

temperature, stirred, then filtered 32. The TATHIO salt is then washed 33. It can be washed with deaerated aqueous acid, such as cold (e.g., about 5°C) HC1 (33%), which can be recycled 34, and then

optionally with deaerated ethanol or methanol to produce a wet cake material. The optional ethanol or methanol wash can then be recycled, and a purge is drawn to prevent accumulation. Using an agitated filter unit during the wash procedures can allow for a reduction of the wash volumes. Under such

circumstances, using small amounts of cold (e.g., about 5°C) water instead of the aqueous acid would be

effective; cold water would be used because of lower solubility of the TATHIO salt in cold water versus, e.g., room temperature.

Whether aqueous acid or cold water is used as a wash, it may be possible to eliminate the ethanol or methanol wash and dry directly from aqueous wet cake or simply use the wet cake in subsequent processing.

It is likely that in a commercial process one would only wash with HCl_aq and, if desired, dry directly.

The resulting wet cake material (TATHIO salt) can be used in subsequent processing without drying or can be dried, as in Figure 1 35, for example at a pressure less than 400 Torr and a temperature of about 30 °C to about 50°C, under a stream of N₂. The dried product 36 is preferably kept under nitrogen.

The yield of TATHIO salt can be increased by recovered additional TATHIO salt from the filtrate remaining from the reaction mixture that contained the precipitated TATHIO salt (i.e., the "mother liquor") by, e.g., evaporation of water.

An embodiment of an integrated process to produce the TATHIO complex with HOOC-Q-COOH is illustrated in Figure 2. The diacid HOOC-Q-COOH is an aromatic diacid, wherein Q is a C₆~C₂₀ substituted or unsubstituted monocyclic or polycyclic aromatic nucleus. Examples of Q include without limitation:

and

One or more heteroatoms (such as N, O, S) may be present in the ring(s) of Q, for example, as shown below :

In one embodiment, Q is represented by the structure of Formula (VIII)

wherein X and Y are each independently selected from the group consisting of H, OH, SH, SO₃H, methyl, ethyl, F, CI, and Br. Preferably, X=Y=OH (i.e., the diacid is 2 , 5-dihydroxyterephthalic acid) or X=Y=H (i.e., the diacid is terephthalic acid) . When X=Y=H, the diacid is referred to as "XYTA" .

To achieve high productivity in the complex formation process, the TATHIO complex can be directly formed from the dissolved TATHIO with a disodium or dipotassium salt of the aromatic acid (for example, "M₂XYTA", wherein M is K or Na) in an aqueous reaction solution.

One embodiment of the process described here is illustrated in Figure 2; possible minor

modifications will be evident to one skilled in the art. In this embodiment, the steps from starting with nitration of 1 , 3-dihalobenzene through the

precipitation of the TATHIO free base are the same as shown in Figure 1; therefore, Figure 2 shows the process steps from the precipitation of the TATHIO free base (26, 27) onward.

With reference to an embodiment shown in

Figure 2, herein referred to as "Option A," the TATHIO salt is precipitated and washed as described previously (26 through 34) , then slurried with or dissolved water 37. Weak base (e.g., aHC03 or KHCO3) sufficient to neutralize the reaction mixture 38 and the diacid source 39 are then added to the slurry to form and precipitate the TATHIO complex 40 (Formula VI) .

Alternatively, the filtered reaction mixture can be combined directly with the base 38 and the diacid source 39 to form and precipitate the TATHIO complex 40, as indicated by the dashed line labeled "Option B" on Figure 2. The amount of weak base needed will depend on how much acid (23 in Figure 1) was added to dissolve TATHIO before filtering. In another alternative, indicated by the dotted line labeled

"Option C" on Figure 2, filtered TATHIO free base 28 can be dissolved in about 1-2 equivalents of acid

(e.g., HC1) 41 and the solution so produced contacted with weak base (e.g., aHC03 or KHCO3) and the diacid source to form the complex 40.

Various designs are possible for combining the

TATHIO moiety with the diacid source and base to produce the complex in addition to those shown in

Figure 2. The base 38 and diacid source 39 are most conveniently added as a single solution. In other embodiments, TATHIO salt in an acid solution could be introduced into a vessel containing a basic diacid source solution, or the diacid source stream could be fed into the vessel containing the TATHIO salt in an acid solution. Alternatively, the diacid source and TATHIO salt could be fed concurrently or consecutively into a buffer solution at the desired pH or into a basic solution. Which design is best for a specific situation will be evident to one of skill in the art.

The TATHIO complex is recovered from the reaction mixture by filtration 42 at a temperature in of the range of about 5°C to about 50°C, preferably about 10°C to about 15°C, and washed 43 with water and methanol, typically at a temperature in the range of about 15°C to about 40°C, and then dried 35. The methanol is recycled 44, and a purge is drawn to prevent

accumulation. The washed and dried TATHIO complex 45 is kept under nitrogen to protect it from oxygen. It is of high enough quality and purity to produce polybenzimidazole polymer of high enough molecular weight to make high performance fibers.

The Option A embodiment illustrated in Figure 2 can produce higher purity TATHIO complex than Options B or C. On the other hand, Options B and C have fewer steps, generate less waste and also require less acid (e.g., HC1) and base (e.g., NaHCOs) , thus lessening raw material and handling cost. All three embodiments produce polymer grade material suitable for the

manufacture of high-performance fibers.

Oxygen is excluded throughout all steps of the processes of making TATHIO, the TATHIO salt, and the complexes. Deaerated water and deaerated acid are used. A small amount of a reducing agent (e.g., about 0.5% tin powder) is optionally added to one or more of aqueous suspensions or aqueous solutions containing TATHIO, TATHIO salt, or TATHIO complex during the process to reduce impurities caused by oxidation and to prevent further impurity formation by that route.

The process described herein is an efficient and effective way to produce TATHIO; high purity TATHIO salts, such as TATHIO · 3HC1 ; and complexes of TATHIO with aromatic diacids, such as 2,5- dihydroxyterephthalic acid, which are precursors for making polybenzimidazole polymer for high performance fibers. This process design eliminates costly

intermediate drying and recrystallization steps. The recycling of spent catalyst, acids, glycol, and

methanol contributes economical and environmental advantages. And, importantly, handling of solid materials with possible skin sensitizing properties and toxicity is avoided, thereby eliminating human and environmental exposure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control .

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

Unless stated otherwise, all percentages, parts, ratios, etc., are by weight.

When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable values, this is to be understood as

specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

When the term "about" is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end- point referred to.

As used herein, the terms "comprises,"

"comprising," "includes," "including," "containing," "characterized by," "has," "having" or any other variation thereof, are intended to cover a non^¬ exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or

apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present) , A is false (or not present) and B is true (or present) , and both A and B are true (or present) .

Use of "a" or "an" are employed to describe elements and components of the invention. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

The materials, methods, and examples herein are illustrative only and, except as specifically stated, are not intended to be limiting.

EXAMPLES

The present invention is further defined in the following examples. It should be understood that these examples, while indicating preferred embodiments of the invention, are given by way of illustration only. From the above discussion and these examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and

modifications of the invention to adapt it to various uses and conditions.

All water used was deaerated and de-ionized water.

The Examples were carried out under exclusion of oxygen .

The meaning of abbreviations is as follows:

"ACDNB" means l-chloro-3-amino-4 , 6-dinitrobenzene, "DADNB" means 1 , 3-diamino-4 , 6-dinitrobenzene, "DCDNB" means 1 , 3-dichloro-4 , 6-dinitrobenzene, "DHTA" means 2 , 5-dihydroxyterephthalic acid, "equiv" means

equivalent ( s ) , "g" means gram(s), ^{λ 1}Η-ΝΜΡ' means proton nuclear magnetic resonance spectroscopy, "h" means hour(s), "K₂DHTA" means the dipotassium salt of 2,5- dihydroxyterephthalic acid, "M" means molar, "mL" means milliliter ( s ) , "min" means minutes, "mmol" means millimole ( s ) , "mol" means mole(s), "MPa" means

megapascals, "psi" means pounds per square inch, "t- BuSH" means t-butylthiol , and "wt" means weight.

DCDNB was prepared as described in U.S. Patent

Application Number 12/335,959.

t-butylthiol (99% purity) and Darco® G-60 activated carbon were obtained from Sigma-Aldrich (Milwaukee, Wisconsin, USA)

Example 1. Preparation of ACDNB from DCDNB

A degassed solution of wet 1 , 3-dichloro-4 , 6- dinitrobenzene (329 g, 24% water) in ethylene glycol under nitrogen (1 kg) was heated to 130°C. Ammonium hydroxide (28% aqueous N¾, 2.32 mol) was added over a period of approximately 2 h such that the desired product was exclusively formed. After addition was complete, the reaction was allowed to cool to room temperature and the precipitate was collected via suction filtration. The filter cake was washed

sparingly with water and was used as is for the next step. The final yield was 233 g, of which 6% was water leaving a dry weight of 219 g (95% yield) . The purity was >91% with the main impurity (8.6%) being DADNB . ¹R NMR (d6 DMSO) : 8.79 ppm (s, 1H) ; 8.27 ppm (b, 2H) ; 7.22 (s, 1H) .

Example 2. Preparation of 1- (t-butylthio) -3- amino-4 , 6-dinitrobenzene from ACDNB

To a solution of NaOH (35.48 g) in 300 g water was slowly added t-BuSH (80 g) . The resultant sodium salt was then added dropwise to a solution of ACDNB (200 g of which 6% is water) in 900 g ethanol under 2 over a period of 1.5 h. After stirring overnight, the

reaction mixture was then filtered and subsequently washed with water (200 mL) followed by displacement washing with 1% NaOH solution (200 mL) , water (200 mL) , and methanol (400 mL) to give a yellow solid. The final yield was 195 g, of which 1.6% was water leaving a dry weight of 192 g (84% yield) . The purity was >90% with the main impurity (9%) being DADNB. ^XH NMR (d6 DMSO): 8.73 ppm (s, 1H) ; 8.24 ppm (b, 2H) ; 7.27 (s, 1H) ; 1.48 (s, 9H) .

Example 3. Preparation of 5- (t-butylthio) -1 , 2 , 4- triaminobenzene from 1- (t-butylthio) -3-amino-4, 6- dinitrobenzene

A I L stirred Hastelloy autoclave was charged with 92 g of 1- (t-butylthio) -3-amino-4, 6-dinitrobenzene

(containing 1.6% water) and 5 g of 5% Pt/C (dry basis, 50% water) . The autoclave was purged 10 times with N₂ and 5 times with H₂ at 90 psi (0.62 MPa) .

Subsequently, 500 mL of deaerated water (purged with N₂ overnight) were added and the mixture was pressurized at 60°C to 300 psi (2.07 MPa) for 30 min, at which point the temperature was increased to 90°C. After another hour, the pressure was increased to 500 psi (3.45 MPa) and hydrogenation was continued for an additional two hours for an approximate uptake of 2.01 moles of ¾ (6 equiv) . The excess hydrogen was released and the autoclave was cooled to 40°C and purged twice with N₂, after which 80 g of deaerated HCl_aq (36.3%, by titration) and 0.5 g SnCl₂ were added. The mixture was stirred for five minutes at 40°C, then passed through a metal CUNO filter to remove catalyst. The autoclave was rinsed with 30 mL of deaerated water. The solution was directly charged into a purged 2 L vessel.

Darco® G-60 activated carbon powder (7 g) was then added to the reaction mixture, stirred overnight and then filtered through a bed of celite. Approximately 1 g Sn powder was added to the filtrate, stirred

overnight and filtered to remove the Sn. The mixture was then brought to pH 13 by slowly adding aqueous sodium hydroxide (40 wt %) . The free base was isolated by vacuum filtration, yielding 152.48 g of a yellow solid (of which 60% was water) to give an 87% recovery. The free base wet cake was then added slowly to 238 g cold HCl with stirring. After stirring for an

additional 2 h, the tri-hydrochloride salt was isolated by filtration and washed sparingly with cold HCl. The yield was 42.57 g (of which 14% was water) giving an isolated yield of 39% (the rest of the salt was kept in solution to be recycled in subsequent runs) and a purity of >98%.

Example 4. Preparation of TATHIO · 3HC1 from 5- (t- butylthio) -1,2, 4-triaminobenzene

To a 500 mL vessel containing 35 g (of which 14 ~6 was water) of 5- (t-butylthio) -1 , 2 , 4-triaminobenzene was added 10 equiv 34% HC1 (100 g) . The vented system was then heated to 80°C overnight, and another 5 equiv 34% HC1 was added the next day. Heating was continued for another 20 h and after cooling to room temperature the solution was filtered and washed sparingly with cold concentrated HC1. The off-white solid was collected as a wet cake and used as in further studies. The final yield was 19.77 g of which 12% was water, leaving a dry weight of 17.47 g (71% yield) with a purity of >98%. ^XH NMR (D₂0) : 7.45 ppm (s, 1H) ; 7.17 (s, 1H) .

Example 5. Preparation of TATHIO-DHTA from TATHIO- 3HC1 solution

6.06 g of K₂DHTA (22.08 mmol) along with 2.69 g of sodium bicarbonate (32.02 mmol) was added to a reaction vessel. This was followed by the addition of 75 g of deaerated water and heating to 75°C. About 33.75 g of 0.18 M TATHIO- 3HC1 salt solution (24.3 mmol) made as described in Example 4 was added to another reaction vessel. The hot solution of K₂DHTA was subsequently added dropwise into the TATHIO- 3HC1 salt solution at room temperature, with fast stirring, over a period of 10 minutes, which resulted in precipitation of a light brown solid. This mixture was then cooled to room temperature, with stirring, for 1.5 hours. The mixture was subsequently filtered and washed with ethanol (50 mL) . The solid beige product was allowed to dry for 18 hours under vacuum. ¹H-NMR analysis revealed the

TATHIO : DHTA ratio as being (1.00:1.01).

It is to be appreciated that certain features of the invention which are, for clarity, described above and below in the context of separate embodiments, may also be provided in combination in a single

embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further,

reference to values stated in ranges includes each and every value within that range.

Claims

CLAIMS What is claimed is:

1. An integrated process comprising the sequential eps under exclusion of oxygen:

a) nitration of 1 , 3-dihalobenzene (Formula II)

wherein each Z is independently CI or Br, in a reaction mixture comprising oleum or SO₃, nitric acid, and H₂SO₄ wherein

(i) the concentration of nitric acid is about 2.0 to about 2.3 moles per mole of 1,3- dihalobenzene ;

wherein the temperature of the reaction mixture does not exceed 120°C;

thereby producing 1 , 3-dihalo-4 , 6-dinitrobenzene

(Formula III) ;

b) directly separating the 1 , 3-dihalo-4 , 6- dinitrobenzene from the reaction mixture by filtration, while recycling the sulfuric acid mother liquor;

c) washing the 1 , 3-dihalo-4 , 6-dinitrobenzene with water or acid then water, then with aqueous ammonia, and then mixing it with solvent as a suspension;

d) monoaminating the 1 , 3-dihalo-4 , 6-dinitrobenzene by heating the suspension formed in step (c) to a temperature in the range of about 60 °C to about 140 °C and contacting it with at least 2.0 equivalents N¾, thereby converting the 1 , 3-dihalo-4 , 6-dinitrobenzene to l-amino-3-halo-4 , 6- dinitrobenzene (Formula IV);

) directly separating the l-amino-3-halo

dinitrobenzene from the reaction mixture by filtration, washing with solvent, then washing with water;

f) forming a slurry of the l-amino-3-halo-4 , 6- dinitrobenzene with methanol and at least 1.0

equivalent of t-butylthiol

tBuSH") in aqueous NaOH, thereby converting the l-amino-3-halo-

4 , 6-dinitrobenzene to l-t-butylthio-3-amino-4 , 6- dinitrobenzene (Formula V) ;

g) directly separating the l-t-butylthio-3-amino-

4 , 6-dinitrobenzene formed in step (f) from the reaction mixture by filtration;

h) forming a slurry of the l-t-butylthio-3-amino-

4 , 6-dinitrobenzene separated in step (g) with water and transferring the slurry to a hydrogenation reactor containing a hydrogenation catalyst to form a reaction mixture;

i) hydrogenating the l-t-butylthio-3-amino-4, 6- dinitrobenzene in water by contacting the reaction mixture formed in step (h) with hydrogen at a pressure in the range of about 10 to about 1000 psi (about 0.069 MPa to about 6.89 MPa) and a temperature in the range of about 50°C to about 100°C for sufficient time to hydrogenate the l-t-butylthio-3-amino-4, 6- dinitrobenzene, thereby producing a suspension

comprising 5- (t-butylthio) -1,2, 4-triaminobenzene

(Formula VI) ;

j) cooling the reaction mixture to a temperature in the range of about 30°C to about 40°C and contacting the reaction mixture with an aqueous solution

comprising 1 to 2 equivalents of HC1 per mol of 5- (t- butylthio) -1 , 2 , 4-triaminobenzene optionally containing 0.005 -0.05 equivalents of a SnCl₂ and, optionally, heating the solution, thereby converting the 5- (t- butylthio) -1 , 2 , 4-triaminobenzene to 2,4,5- triaminothiophenol salt;

k) filtering the reaction mixture, thereby

removing the spent hydrogenation catalyst;

1) optionally, passing the filtered reaction mixture through a carbon bed;

m) adjusting the pH of the filtered reaction mixture to a value above about 7 by adding base, thereby precipitating the 2 , 4 , 5-triaminothiophenol free base; and

n) isolating the 2 , 4 , 5-triaminothiophenol free base by filtration.

2. The process of claim 1 further comprising the steps

o) washing the 2 , 4 , 5-triaminothiophenol free base with water to produce a water-wet free base that is about 40 to about 60% water by weight;

p) combining the water-wet free base with about 5 to about 10 equivalents of aqueous and gaseous HC1 solution, optionally saturated with gaseous HC1, so that the ratio of TATHIO free base to HC1 to water is about 15-25 to 25-35 to 45-55 parts by weight, thereby forming and precipitating 2 , 4 , 5-triaminothiophenol hydrochloride salt;

q) filtering the 2 , 4 , 5-triaminothiophenol

hydrochloride salt and washing it with concentrated aqueous HC1;

r) combining the wet 2 , 4 , 5-triaminothiophenol hydrochloride salt with 5-10 equivalents aqueous concentrated HC1 and heating to 70°C -100°C with an optional HC1 stream to remove t-butylchloride

byproduct; and

s) filtering, washing, and drying the precipitated 2 , 4 , 5-triaminothiophenol hydrochloride salt.

3. The process of claim 1 wherein Z is CI.

4. The process of claim 2 wherein the ratio of TATHIO free base to HC1 to water is about 20 to 30 to 50 parts by weight

5. The process of claim 1 wherein the suspension is contacted with 2.03 to 2.07 equivalents N¾ in step (d) .

6. A process comprising steps a) through 1) as recited in claim 1, further comprising either:

i) combining the filtered reaction mixture produced in step (1) directly with a diacid source and a weak base;

or

ii) adjusting the pH of the filtered reaction mixture to a value above about 7 by adding base, thereby precipitating the 2 , 4 , 5-triaminothiophenol free base; dissolving the precipitated TATHIO free base in about 1-2 equivalents of HC1; and contacting the solution so produced with a weak base and a diacid source ;

thereby forming and precipitating the complex (Formula VII)

wherein the diacid source is HOOC-Q-COOH, a disodium salt of HOOC-Q-COOH, a dipotassium salt of HOOC-Q-COOH, or a mixture of at least two of these; and wherein Q is a C6~C2o monocyclic or polycyclic aromatic nucleus.

7. The process of claim 6 wherein the weak base is NaHC0₃ or KHC0₃.

8. The process of claim 6 wherein Q is selected from the group consisting of:

 and

9. The process of claim 6 wherein

Q is represented by the structure of Formula VIII

wherein X and Y are each independently selected from the group consisting of H, OH, SH, SO₃H, methyl, ethyl, F, CI, and Br.

10. The process of claim 9 wherein X=Y=OH or X=Y=H

11. The process of claim 1 further comprising adding a reducing agent to at least one aqueous suspension or aqueous solution containing 2 , 4 , 5-triaminothiophenol or 2 , 4 , 5-triaminothiophenol salt, or 2,4,5- triaminothiophenol complex.

12. The process of claim 11, wherein the reducing agent is tin powder or SnCl₂ ·

13. The process of claim 2 further comprising adding a reducing agent to at least one aqueous suspension or aqueous solution containing 2 , 4 , 5-triaminothiophenol or 2 , 4 , 5-triaminothiophenol salt.

14. The process of claim 13, wherein the reducing agent is tin powder or SnCl₂ ·

15. The process of claim 6 further comprising adding a reducing agent to at least one aqueous suspension or aqueous solution containing 2 , 4 , 5-triaminothiophenol , 2 , 4 , 5-triaminothiophenol salt, or 2,4,5- triaminothiophenol complex.

16. The process of claim 15, wherein the reducing agent is tin powder or SnCl₂ ·