TECHNICAL FIELD
[0001] This invention relates to a method of preparing 2,2'-dithiodianiline by reacting
an alkali metal salt of o-aminothiodianiline with hydrogen peroxide.
[0002] The 2,2'-dithiodianiline is particularly useful for curing, crosslinking or extending
isocyanate-terminated polyurethane prepolymers. It can be prepared by oxidizing the
sodium salt of o-aminothiophenol. However, the 2,2'-dithiodianiline must be obtained
in high purity form, without the attendant typical oxidation byproducts, for satisfactory
use in the preparation of most cured polyurethanes.
BACKGROUND ART
[0003] Heretofore, 2,2'-dithiodianiline could be prepared by the steps of (A) oxidizing
an aqueous solution of the sodium salt of o-aminothiophenol through the slow addition
of hydrogen peroxide to form a water slurry of the water insoluble 2,2'-dithiodianiline,
and solution of water soluble byproducts and (B) mixing toluene with the slurry to
extract the 2,2'-dithiodianiline in the hydrocarbon phase.
[0004] Additional background information might be found in British patent No. B-558,887.
[0005] However, such a method has particular disadvantages since the solid 2,2'-dithiodianiline
product is directly subject to degradation by (A) rising to the top of the aqueous
slurry during the reaction and being scorched, or oxidised, by contact with the hydrogen
peroxide slowly being added, and (B) by being in direct contact with sodium hydroxide
product in the aqueous phase. The 2,2'-dithiodianiline is simply subject to degradation
by being in contact with both one of the reactants and by one of the products.
[0006] Therefore, it is an object of this invention to provide a method of preparing 2,2'-dithiodianiline
through the oxidation of a salt of o-aminothiophenol and recovering the 2,2'-dithiodianiline
in a relatively high purity form.
DISCLOSURE AND PRACTICE OF THE INVENTION
[0007] In accordance with this invention, a method of preparing 2,2'-dithiodianiline through
the oxidation of a salt of o-aminothiophenol and recovering the 2,2'-dithiodianiline
in a relatively high purity form is provided.
[0008] In accordance with this invention, a method of preparing 2,2'-dithiodianiiine by
reacting an alkali metal salt or o-aminothiophenol with hydrogen peroxide is characterized
by (A) agitating a mixture of a water solution of the sodium or potassium salt of
o-aminothiophenol and an unstable dispersion therein of a liquid hydrocarbon selected
from at least one of toluene, benzene, or xylene, (B) oxidizing said salt of o-aminothiophenol
by slowly adding a water soluble peroxide to said agitated mixture, (C) discontinuing
the agitation of the dispersion to allow the mixture to substantially immediately
separate into a lower aqueous phase and upper hydrocarbon phase having a continuous,
sharply defined innerface therebetween, (D) drawing off said lower aqueous phase and
(E) distilling the remaining hydrocarbon phase to remove said hydrocarbon therefrom
and recovering said 2,2'-dithiodianitine as a distilland.
[0009] It is important to appreciate that, in the oxidizing step (B) products are formed
which comprise inorganic salts and sodium or potassium hydride as well as the defined
2,2'-dithiodianiline.
[0010] In the preferred practice of this invention, the method of preparing the 2,2'-dithiodianiline
is characterized by (A) forming an agitated, unstable mixture comprised of (1) 100
parts by weight of an aqueous solution comprising 10 to 50 weight percent sodium or
potasssium salt of o-aminothiophenol, and correspondingly, 90 to 50 weight percent
water and (2) a dispersion therein of 10 to 50 parts by weight hydrocarbon selected
from at least one of toluene, benzene or xylene, (B) oxidizing said salt of o-aminothiophenol
by adding a water soluble peroxide to said agitated dispersion sufficiently slowly
so that only a trace, if any, residual peroxide concentration is maintained in the
dispersion, at a temperature in the range of 5°C. to 50°C., preferably 10°C. to 40°C.,
(C) discontinuing said agitation to essentially immediately yield a sharply defined
lower aqueous phase and an upper hydrocarbon phase containing said 2,2'-dithiodianiline
essentially exclusive of the remainder of said products contained in said aqueous
phase, (D) drawing off said sharply defined aqueous phase and (E) distilling the remaining
hydrocarbon phase to a pot temperature in the range of 130°C. to 150°C. under a reduced
pressure in the range of 6666 Pa (50 mm Hg) to 26664 Pa (200 mm HG) to
' remove said hydrocarbon solvent as a distillate and recover said 2,2'-dithiodianiline
as a distilland.
[0011] It is important to appreciate that it has been discovered that the practice of this
invention especially enhances the stability and recovery of a relatively high purity
2,2'-dithiodianiline product by minimizing its contact with its degrading environment.
The practice of this invention further enables larger batches to be produced in the
same equipment utilized for the prior slurry process and, therefore, enables a general
improvement in the overall process.
[0012] Indeed, the utilization of the unstable hydro- carbon/water solution dispers on effects
both an effective insulation and clean separation of the 2,2'-dithiodianiline product
in a relatively high purity form from the presence of degraded reactants and byproducts
right at the point of reaction itself. As the reaction proceeds, the product is immediately
both withdrawn from its reaction medium and insulated therefrom.
[0013] Generally, the 2,2'-dithiodianiline is uniquely of sufficiently high purity, without
additional purification steps, to be satisfactorily used as a curative for some isocyanate-terminated
polyurethane prepolymers although at least one water wash of the product is preferably
for optimum results. It should readily be appreciated by those having skill in the
polyurethane art that purity of reactants is of high priority in such polyurethane
reaction systems.
[0014] For optimum purity of the 2,2'-dithiodianiline for use as a polyurethane curative,
it is desired to water wash the hydrocarbon phase containing the 2,2--dithiodianiline
(before the distillation step) with at least one, generally from 1 to 5, preferably
2 to 4, water washes. The primary purpose is to remove traces of sodium or potassium
hydroxide which can typically adhere to surfaces of the physical reactor system itself
and bleed into the product or hydrocarbon phase contained in the reactor.
[0015] In the conduct of the reaction, it is necessary to provide an agitated, unstable
aqueous solution/hydrocarbon dispersion. The liquid hydrocarbon is chosen so that
it is naturally immiscible with the aqueous solution. Therefore, the mixture requires
agitation, preferably a very rapid or high degree of agitation, to provide and maintain
the dispersion. When the agitation stops, the dispersion disappears within a few minutes,
typically in a minute or less, yielding sharply defined aqueous and hydrocarbon phases.
Such agitation can be provided by conventional means.
[0016] In the further conduct of this invention, it is desired to minimize the potential
of excess of the peroxide reactant. On this basis, (1) the peroxide is only added
slowly for this purpose and to keep the reaction exotherm down and (2) a test is made
to determine if the reaction is essentially complete so that further peroxide addition
is not necessary. For this test, the agitation is stopped, the phases automatically
separated, and a sample of the aqueous phase withdrawn and tested for peroxide content.
If the sample does not contain peroxide, the agitation and dispersion are re-established
and peroxide addition resumed. If the sample contains peroxide, the reaction is considered
complete.
[0017] For the practice of this invention, the o-aminothiophenol can conveniently be obtained
from the reaction of benzothiazole with sodium hydroxide. Such a reaction is generally
exothermic and can be conducted at a temperature in the range of about 130°C. to about
170°C. The product of such a reaction is upgraded to remove impurities by first steam
stripping to remove volatiles, aniline and benzothiazole, following which water and
hydrocarbon are added to adjust the concentration of the sodium salt of o-aminothiophenol
in the water to about 3 to about 30 weight percent. The mixture can be, if desired,
treated with activated carbon to remove trace impurities and filtered. The o-aminothiophenol
salt, as an aqueous solution in the presence of the hydrocarbon is now ready for oxidation.
[0018] The practice of this invention is further illustrated by reference to the following
example which is intended to be representative rather than restrictive of the scope
of the invention. Unless otherwise indicated, all parts and percentages are by weight.
Example
[0019] To a suitable reactor was charged 1.2 parts of a 24 weight percent aqueous solution
of the sodium salt of o-aminothiophenol and 1.5 parts toluene. The temperature of
the mixture was adjusted to about 20°C. and rapidly agitated to form a dispersion
which would be unstable if it were not for the agitation. To the rapidly stirred mixture
and dispersion was then slowly added about 0.16 part by weight hydrogen peroxide as
a 13.5 percent aqueous solution over a period of about 20 to 30 minutes. This amounted
to about a 16 percent excess peroxide to insure complete oxidation. With stirring,
the reaction system was maintained at a temperature in the range of about 20°C. to
about 50°C., which was about a maximum allowable temperature, while the 2,2'-dithiodianiline
product formed in the aqueous phase and immediately and exclusively withdrew and dissolved
into the dispersed toluene phase.
[0020] The final oxidation product contained 2,2'-dithiodianiline in high purity form in
the dispersed toluene phase while the water phase selectively contained reaction byproducts
which included inorganic salt, sodium hydroxide as well as the original water.
[0021] Agitation was stopped and the mixture automatically and quickly separated into a
sharply defined upper toluene phase and a lower aqueous phase in a few seconds to
a few minutes. The lower aqueous phase was simply drawn off and separated from the
toluene phase. The organic toluene phase was washed three times with about 8.3 parts
by weight of water, with the water phase being drawn off after each wash. The parts
by weight was based on one part by weight final 2,2'-dithiodianiline.
[0022] It is important to appreciate that the 2,2'-dithiodianiline product can be degraded
by the sodium hydroxide. Therefore, the immediate extraction of the 2,2'-dithiodianiline
product into the toluene phase during the actual reaction step has a very special
value.
[0023] The toluene from the toluene phase was simply removed by flash distillation from
the top of the reactor through a condenser into a receiver at a reduced pressure of
about 1333 Pa (100 mm Hg) and a pot temperature of about 150°C. The remaining molten
distilland product was removed from the reactor by pressurizing with about 34474 Pa
(5 psig) from the reactor at about 130°C. and packaged in containers in which it solidified
when cooled below about 90°C. The overall yield was above 90 percent of 2,2'-dithiodianiline
of a total amine content (purity of about 98.1 percent).
[0024] The 2,2'-dithiodianiline product was then successfully used as a curative for an
isocyanate-terminated polyisocyanate/polymeric polyol polyurethane prepolymer of toluene
diisocyanate and polytetremethylene ether glycol.
1. A method of preparing 2,2'-dithiodianiline by reacting an alkali metal salt of
o-aminothiophenol with hydrogen peroxide characterized by (A) agitating a mixture
of a water solution of the sodium or potassium salt of o-aminothiophenol and an unstable
dispersion therein of a liquid hydrocarbon selected from at least one of toluene,
benzene, or xylene, (B) oxidizing said salt of o-aminothiophenol by slowly adding
a water soluble peroxide to said agitated mixture, (C) discontinuing the agitation
of the dispersion to allow the mixture to substantially immediately separate into
a lower aqueous phase and upper hydrocarbon phase having a continuous, sharply defined
innerface therebetween, (D) drawing off said lower aqueous phase and (E) distilling
the remaining hydrocarbon phase to remove said hydrocarbon therefrom and recovering
said 2,2'-dithiodianiline as a distilland.
2. The method of claim 1 characterized by (A) forming an agitated, unstable mixture
comprised of (1) 100 parts by weight of an aqueous solution comprising 10 to 50 weight
percent sodium or potassium salt of o-aminothiophenol, and correspondingly, 90 to
50 weight percent water and (2) a dispersion therein of 10 to 50 parts by weight hydrocarbon
selected from at least one of toluene, benzene or xylene, (B) oxidizing said salt
of o-aminothiophenol by adding a water soluble peroxide to said agitated dispersion
sufficiently slowly so that only a trace, if any, residual peroxide concentration
is maintained in the dispersion, at a temperature in the range of 5°C. to 50°C., (C)
discontinuing said agitation to essentially immediately yield a sharply defined lower
aqueous phase and an upper hydrocarbon phase containing said 2,2'-dithiodianiline
essentially exclusively of the remainder of said products contained in said aqueous
phase, (D) drawing off said sharply defined aqueous phase and (E) distilling the remaining
hydrocarbon phase to a pot temperature in the range of 130°C. to 150°C. under a reduced
pressure in the range of 6666 Pa (50 mm Hg) to 26664 Pa (200 mm Hg) to remove said
hydrocarbon solvent as a distillate and recover said 2,2'-dithiodianiline as a distilland.
3. The method of claim 2 characterized by (A) forming an agitated mixture of (1) 100
parts by weight of an aqueous solution comprised of 15 to 30 weight percent sodium
salt of o-aminothiophenol and, correspondingly, 85 to 70 weight percent water and
(2) a dispersion therein of 15 to 25 parts by weight toluene, at a temperature in
the range of 10°C. to 40°C., (B) oxidizing said sodium salt by slow addition of hydrogen
peroxide to said agitated mixture, (C) discontinuing the agitation to form the sharply
defined lower aqueous phase and upper hydrocarbon phase, (D) drawing off said aqueous
phase, (E) distilling the hydrocarbon phase to recover 2,2'-dithiodianiline as a distilland.
1. Un procédé pour préparer de la 2,2'-dithiodianiline qui consiste à faire réagir
un sel d'un métal alcalin du o-aminothiophénol avec de l'eau oxygénée charactérisé
(A) en ce qu'on agite un mélange d'une solution aqueuse d'un sel de sodium ou de potassium
du o-aminothiophénol et d'une dispersion instable de toluène, de benzène, de xylène,
ou d'au moins un de ces trois hydrocarbures liquides,
(B) en ce qu'on fait oxyder ce sel du o-amino-. thiophénol en ajoutant lentement au
mélange agité un peroxyde soluble dans l'eau
(C) en ce qu'on termine l'agitation de la dispersion pour permettre au mélange de
se séparer pratiquement immédiatement dans une phase inférieure aqueuse et dans une
phase supérieure d'hydrocarbure ayant entre elles une interface continue bien définie
(D) en ce qu'on soutire cette phase inférieure aqueuse et
(E) en ce qu'on distille la phase restante d'hydrocarbure pour en éliminer l'hydrocarbure
et obtenir la 2,2'-dithiodianiline comme résidu de distillation.
2. Le procédé selon la revendication 1 charactérisé
(A) en ce qu'on forme un mélange agité instable, comprenant (1) 100 parts en poids
d'une solution aqueuse composée de 10 à 50% (en poids) d'un sel. de sodium et de potassium de l'o-aminothiophénol et respectivement de 90 à 50% (en
poids) d'eau et (2) en ce qu'on forme dans ce mélange une dispersion qui comprend
10 à 50 parts en poids de toluène, de benzène, de xylène, ou au moins 10 à 50 parts
d'un de ces trois hydrocarbures
(B) en ce qu'on fait oxyder le sel de l'o-aminothiophénol en ajoutant suffisamment
lentement un peroxyde soluble dans l'eau à cette dispersion agitée, de façon à ce
que seulement une trace de concentration de peroxyde résiduel, si trace il y a, est
retenue dans la dispersion, la température étant comprise entre 5°C et 50°C.
(C) en ce qu'on termine l'agitation pour avoir pratiquement immédiatement une phase
inférieure bien définie et une phase supérieure d'hydrocarbure contenant la 2,2'-dithiodianiline,
le reste des produits contenus dans la phase aqueuse étant pratiquement absent de
cette phase.
(D) en ce qu'on soutire la phase aqueuse bien définie et
(E) en ce qu'on distille la phase restante d'hydrocarbure à une température de récipient
comprise entre 130°C et 150°C, à une pression réduite comprise entre 6666 Pa (50 mm
Hg) et 26664 Pa (200 mm Hg) pour éliminer le solvant d'hydrocarbure comme distillat
et de récupérer la 2,2'-dithiodianiline comme résidu de distillation.
3. Le procédé selon la revendication 2 charactérisé
(A) en ce qu'on forme un mélange agité de (1) 100 parts en poids d'une solution aqueuse
comprenant 15 à 30% en poids de sel de sodium du o-aminothiophénol et repective- ment
85 à 70% en poids d'eau et (2) en ce qu'on forme une dispersion de 15 à 25 parts (en
poids) de toluène, à une température comprise entre 100C et 40°C,
(B) en ce qu'on fait oxyder le sel de sodium en ajoutant lentement de l'eau oxygénée
au mélange,
(C) en ce qu'on termine l'agitation pour former la phase inférieure aqueuse bien définie
et la phase supérieure d'hydrocarbure,
(D) en ce qu'on soutire la phase aqueuse et
(E) en ce qu'on distille la phase d'hydrocarbure pour obtenir la 2,2'-dithiodianiline
comme résidu de distillation.
1. Ein Verfahren zur Herstellung von 2,2'-Dithiodianilin indem man ein Alkalimetallsalz
von o-Aminothiophenol mit Wasserstoffperoxyd reagieren lässt, dadurch gekennzeichnet,
(A) dass man die Mischung einer wässerigen Lösung von Natrium- oder Kaliumsalz von
o-Aminothiophenol und einer unstabilen Dispersion von Toluol, Benzol oder Xylol, wenigstens
aber einem der drei vorhergenannten flüssigen Kohlenwasserstoffen rührt,
(B) dass man das o-Aminothiophenolsalz oxydiert, indem langsam ein wasserlösliches
Peroxyd zur gerührten Mischung zugegeben wird,
(C) dass man die Rührung der Dispersion beendet um der Mischung zu erlauben sich praktisch
sofort in eine untere wässerige Phase und eine obere Kohlenwasserstoffphase aufzuteilen,
wobei eine kotinuierliche scharfe Phasengrenzfläche auftritt,
(D) dass man die untere wässerige Phase abzieht und
(E) dass man die restliche Kohlenwasserstoffphase destilliert, um den Kohlenwasserstoff
davon zu entfernen und das 2,2'-Dithiodianalin als Destillationsrückstand zu erhalten.
2. Das Verfahren nach Anspruch 1, dadurch gekennzeichnet,
(A) dass man eine aufgerührte, unstabile Mischung bildet, die aus (1) 100 Gewichtsteilen
einer wässerigen Lösung besteht, wobei die wässerige Lösung 10 bis 50 Gewichtsprozente
Natrium- oder Kaliumsalz von o-Aminothiophenol, und in entsprechendem Masse 90 bis
50 Gewichtsprozente Wasser enthält, und (2) dass man eine Dispersion in jener aufgerührten
unstabilen Mischung bildet, die aus 10 bis 50 Gewichtsteilen Toluol, Benzol, Xylol
oder aus 10 bis 50 Gewichtsteilen wenigstens einer der drei vorher genannten Kohlenwasserstoffe
besteht,
(B) dass man jenes o-Aminothiophenolsalz oxydiert indem man ein wasserlösliches Peroxyd
zur aufgerührten Dispersion genügend langsam hinzugibt, so dass bei einem Temperaturbereich
von 5°C bis 50°C nur eine Spur, wenn überhaupt der restlichen Peroxyd-konzentration
in der Dispersion zurückbleibt,
(C) dass man die Rührung beendet um praktisch sofort eine scharf abgegrenzte untere
wässerige Phase und eine obere Kohlenwasserstoffphase zu erhalten, die das 2,2'-Dithiodianalin
im wesentlichen ausschliesslich der restlichen Produkte der wässerigen Phase enthält,
(D) dass man jene scharf abgegrenzte wässerige Phase abzieht,
(E) dass man die restliche Kohlenwasserstoffphase bei einer Gefässtemperatur im Bereich
von 130°C bis 150°C und einem reduzierten Druck im Bereich von 6666 Pa (50 mm Hg)
bis 26664 Pa (200 mm Hg) destilliert um das Kohlenwasserstofflösungsmittel als Destillat
zu entfernen und das 2,2'-Dithiodianalin als Destillationsrückstand zu erhalten.
3. Das Verfahren nach Anspruch 2 dadurch gekennzeichnet,
(A) dass man eine aufgerührte Mischung von (1) 100 Gewichtsteilen einer wässerigen
Lösung bildet die 15 bis 30 Gewichtsteile Natriumsalz von o-Aminothiophenol und, in
entsprechendem Masse, 85. bis 70 Gewichtsprozente Wasser enthält, und (2) dass man
eine Dispersion in: der aufgerührten Mischung bildet, die 15 bis 25 Gewichtstejle
Toluol bei einem Temperaturbereich von 10°C bis 40°C bildet,
(B) dass man das Natriumsalz oxydiert indem man zu jener aufgerührten Dispersion langsam
Wasserstoffperoxyd hinzufügt,
(C) dass man die Rührung beendet um die scharf abgegrenzte untere wässerige Phase
und die obere Kohlenwasserstoffphase zu erhalten,
(D) dass man die wässerige Phase abzieht und
(E) dass man die Kohlenwasserstoffphase destilliert um 2,2'-Dithiodianilin als Destillationsrückstand
zu erhalten.