Note: Descriptions are shown in the official language in which they were submitted.
W0 92/02493 P~/US91/04437
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PREPARAT~ON OP RELATIVELY PURE P,P--B~SPHENOL S
Technical Field
This invention relates to the manufacture
of ~ dihydroxydiphenyl sulfone) known also as
4,4'-Bisphenol S (hereafter sometimes " 4,4'-BPS"),
and particularly to a method of efficiently and/or
continuously separating 4,4'-BPS from a product
mixture containing significant quantities of
2,4'-BPS, which is typically produced along with the
4,4'-BPS. The basic principle of reacting sulfuric
acid with an excess of phenol is known.
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~ackground of the Invention
It is known to react sulfuric acid with an
excess of phenol to obtain Bisphenol S. In Ogata et
j al U.S. Pate~t 4,820,831 a process is described
(col. 4) wherein the phenol/sulfuric acid
. (dehydration) reaction is conducted in the presence
; of a solvent which is distilled off along with the
excess phenol to promote the production of 4,4'-BPS.
In U. S . Patent 4,820,831, Ogata et al also adds an
aromatic sulfuric acid to promote isomerization o4
2,4'-BPS to 4,4'-BPS. However, there are
disadvantages to this procedure, namely that the
color of the reaction product deteriorates as the
solvent and phenol are removed from the mixture and
the colored materials formed as well as any
catalysts added must be removed in subsequent
purification steps.
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W092/0~93 ~ 2 ~ ~ 6 1 ~ 8 PCT/U~91/~37
In U.S. Patent 4,3~2,147, Kitamura et al
cool the original dehydration reaction produc~: (or,
apparently, any mixture of BPS isomers) to separate
out the 4,4'-BPS. No particular solvent is used;
the 4,4'-BPS is separated as an adduct with phenol.
Summary of the Invention
I have found that the reaction of sulfuric
acid and phenol to make ~PS can be conducted quite
ef~iciently by (a) forcing the dehydration reaction
to completion (or near completion) by gradually
distilling a mixture of water and phenol from the
reaction mixture, (b) selectively precipitating
4,4~-BPS from the reaction mixture by adding a
solvent such as toluene, (c) removing the 4,4'-BPS
from the mixture by a separation step, i.e.
filtration or centrifugation, and td) the
unrecovered material from the separation step is
recycled to the dehydration reaction step. The
purity of the product 4,4'-BPS is maintained at a
high level by following this process, particularly
in the detail described below; the color is
excellent.
Solvents which may be used other than
toluene are benzene, chlorobenzene, xylene,
o-dichlorobenzene, anisole, cumene, and the like.
Detailed Description of the Invention
My invention comprises
(a) reacting sulfuric acid and phenol in a
ratio of about 1:2 to about 1:10, preferably about
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1:2.5 to about 1:5, at temperatures beginning at
about 40 to about 100C, preferably about 60 to
about 70C, and increasing during the reaction to
about 190 to about 205C, preferably about 1~5 to
about 200C under an inert atmosphere such as
nitrogen or argon, preferably at atmospheric
pressure although a vacuum may be used.
(b) during the reaction, removing the
water formed by distilling off the water as a
mixture with phenol until the reaction is complete,
or nearly complete.
(c) adding about 0.1 to about 5.0
equivalent volumes, preferably about 0.5 to about
1.5 volumes (based on the volume of phenol used for
the reaction as one equivalent volume), of a solvent
for 3isphenol S, preferably benzene, toluene,
chlorobenzene, xylene, o-dichlorobenzene, anisole,
or cumene, most preferably toluene, over a period of
about 10 to about 200 minutes, preferably about 30
to about 60 minutes. During the addition the
mixture should be cooled or allowed to cool to the
boiling point of the solvent, then the mixture
allowed to cool further to about room temperature to
about 120C, preferably about 55 to about 75C to
form crystals of 4,4'-BPS.
(d) separating the crystals of 4,4'-BPS
from the reaction mixture preferably by filtration
or centrifugation.
(e) isolating the ~PS isomers from the
filtrate from step (d) by removal of the solvent and
phenol and crystallizing the BPS isomers, and
~ f) recycling the isolated BPS isomers
from step (e) by adding the mixture to reaction
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W092/02493 PCT/US91/04437
2Q6~7 g
step (a) to b~ing about isomerization of the
2,4'-~PS contained in the filtrate to 4,4'-BP'.
during the reaction cycle.
(g) further purifying the crude 4,4'-~PS
isolated from separation step (d) above by
recrystallizing the compound from water or mixtures
of water and solvents such as methanol, ethanol and
acetone, preferably methanol. The water or
water/solvent mixture should contain about 0.0005 to
about 0.05 molar eguivalents, preferably about 0.002
to 0.01 molar equivalents (based on the amount of
BPS being recrystallized) of a reducing agent such
as a thiosulfate, sulfite, bisulfite or borohydride
salt, preferably sodium bisulfite, to reduce the
amount of color in the final product.
A preferred process ("best mode") is as
~ollows:
(1) Molten phenol (purified, 4.75-5.0
molar equiv.) is placed in the reactor and the
syste~ is flushed with an inert atmosphere
(nitrogen).
(2) Concentrated sulfuric acid (1.0 molar
equiv.) is added ta the phenol and the mixture is
heated to reflux (155UC) over a period of 30
minutes.
(3) A mixture of water and phenol is
slowly distilled off until the reaction temperature
reaches 195C and the distillation head temperature
reaches 170C. This usually takes 2-2.5 hours.
(4) The reaction mixture is then refluxed
for an additional 1-1.5 hours, collecting distillate
only when the still head temperature falls below
170C.
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W092/02493 2a66~ 7~ PCT/US9l/04437
(5) Toluene (a volume equivalent to the
volume of phenol used in the reaction) is slowly
added to the reaction mixture. This cools th~
reaction mixture to the boiling point of toluene
(110C) and reduces the solubility of 3PS in the
solution. When the reaction mixture temperature
reaches about 130C and the solvent is approximately
25-30~ toluene, the 4,4'-isomer of BPS begins to
precipitate from the solution as a fine pink powder.
The remainder of the toluene is added while the
precipitation continues.
(6) After all the toluene has been added,
the mixture is cooled to 65C and then filtered.
~ 7) The solid is rinsed with toluene to
remove some orange colored material and then dried
to yield a light pink powder.
(8) The toluene and most of the phenol are
distilled under vacuum from the filtrate fro~ step
(6).
(9) Toluene is added to the distillation
residue from step (8) to precipitate the 2,4'-BPS
isomer and the remainder of the 4,4'-isomer.
(10) The precipitate from the distillation
pot residue in step (9) is filtered from the slurry
and is then recycled by adding it to a subsequent
reaction batch of PPS between steps (2) and (3),
above.
(11) An additional one hour reflux period
is added to the beginning of step (3) above, before
any distillate is collected, for batches of BPS
which contain recycled materials to help insure
complete equilibration of the BPS isomers during the
reaction cycle.
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~ 12) The ~PS from step (7) is dissolved in
an equivalent weight of boiling methanol and kreated
with 0.005 molar eqyivalents of sodium sulfite as a
1.0 molar solution in water. The methanolic
solution is then diluted with water (9 times the
weight of the methanol used) keeping the mixture at
~; its boiling point. After all of the water has been
;l added the mixture is allowed to cool to room
temperature. The solid is removed from the mixture
by filtration and rinsed with water and dried to
remove the excess solvent.
My process has been used successully as
is illustrated in the following examples of
experiments performed:
Example l
Sulfuric acid (22.62 g, 94.6%) was added
to molten phenol (100.41 g) at 70C with rapid
stirring into a reaction flask equipped with a
simple distillation apparatus. The mixture was
heated to 130C for one hour and then heated further
to reflux temperature (155C) and a mixture of water
and phenol was gradually distilled from the reaction
flask until the solution temperature reached 195C
and the distillation head temperature had reached
170C. The distillate collection was stopped and
the mixture was refluxed until the vapor temperature
fell to below 160C. The distillate was collected
again until the distillation head temperature again
rose to 170C. The cycle of distillate collection
and refluxing was continued until 2.5 hours had
elapsed since the first distillate was collected.
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W092/02493 PCT/US9l/04~37
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Toluene (100 ml) was added over a period
of 40 minutes while maintaining rapid stirrin~.
After the addition was complete, the mixture was
allowed to cool to 60C. The product was removed
from the suspension by vacuum filtration and rinsed
with two portions of tolusne ~50 ml) and then dried
to remove the residual toluene to yield 33.41 g of
4,4'-BPS with a purity of 97.5~.
The crude product was dissolved in boiling
methanol (25 ml) and hot water (225 ml) which
contained sodium thiosulfate (0.10 g) was added
while keeping the mixture boiling. The solution was
cooled to 25C and allowed to crystallize over a
period of 3 hours at that temperature. The product
was collected by vacuum filtration and the water
removed from the crystals to yield 31.72 g of
4,4'-BPS with a purity >99.5% and an APHA color o
<20 for a 30~ solution in methanol.
Example 2
Sulfuric acid (35.45 g, 93.5~) was added
to molten phenol (150.38 g) at 70C in a reaction
flask equipped with a distillation head and the
apparatus was evacuated to 350 mm ~g. The mixture
was heated to reflux and the distillate was
collected any time the distillation head temperature
was below 140C and the distillate collection was
stopped any time the vapor temperature rose ~o
150C. The reaction mixture was heated in this
manner for five hours.
Toluene (150 ml) was added to the reaction
mixture over a period of one hour and the mixture
was allowed to cool to 65C before the product was
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filtered from the mixture to produce 44.10 g of
light pink material which was purified by the means
described in Example 1 to give a final product wlth
the >99.5% purity and APHA color of <20 for a 30%
methanolic solution.
Example 3
Sulfuric acid (~5.20 g, 96.0%) was added
to molten phenol (153.30 g) at 70C in a reaction
flask equipped with a Dean-Starke trap and the
mixture was heated to 130C. Cumene (90 ml) was
added to the reaction mixture and the solution was
heated to reflux, collecting the water of the
reaction in the trap and continuously returning the
cumene to the reaction vessel. The reaction mixture
was refluxed for 7.5 hours at which point the cumene
in the Dean-Starke trap was separated from the water
and added to the reaction mixture along with an
additional 60 ml cumene over a period of 15 minutes.
The mixture was gradually cooled to 70C allowing
the product to slowly crystalize. The solid was
collected by vacuum filtration, rinsed with two
50 ml portions of cumene and dried to remove the
remainder of the solvent to yield 4,4'-BPS (60.1 g,
98.1~). After purification by the method descrihed
in Example 1, a product was obtained with a purity
>99.S% and an APHA color of ~20 for a 30% solution
in methanol.
Example 4
Phenol (151.40 g) and sulfuric acid
(35.94 g, 96.0%) were reacted in the manner
described in Example 1. After the addition of
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WO92/02qg3 PCT/U~91/04437
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toluene (150 ml) and cooling o the reaction mixture
to 70C, 4,4'-BPs (52.1 g, 97.7~) was separat,ed from
the excess phenol and toluene by vacuum filtration.
The iltrate was distilled under vacuum to
remove the toluene and most of the phenol (78 g).
The toluene was added to the distillation pot
residue, causing the precipitation of a mixture of
2,4'-BPS and 4,4'-~PS (28.1 g).
Phenol (182.2 g) and sulfuric acid
(35.2 g) were mixed and heated to 130C for one
hour. The mixture of ~PS isomers from above was
added to the mixture which was then heated to reflux
~155C) for one hour. The reaction was then carried
out as in Example 1 with the mixture of water and
phenol distilled off whenever the vapor temperature
fell below 160C. Toluene ~180 ml) was added to the
mixture and the product was collected after the
mixture had cooled to 65C. The crude 4,4'-BPS
~74.2g) was recrystallized as described in Example 1
to produce a material with purity >99.5% and APHA
color of 30 for a 30% methanolic solution.
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