1
SPECIFICATION
PROCESS FOR PREPARING P-MERCAPTOCARBOXYLIC ACID
5 TECHNICAL FIELD
[000l]
The present inve~tion relates to a process for preparing
P-mercaptocarboxylic acid using unsaturated carboxylic acid.
BACKGROUND ART
10 [0002]
P-mercaptocarboxyllc acid is a compound whlch is useful as a
raw material for organic synthesis products including agricultural
chemicals, and pharmaceuticals, and is useful as a raw material for
a stabilizer of vinyl chloride, a cross-linking agent of an epoxy
15 resin and an acrylic acid ester polymer, and a plastic lens monomer.
Examples ofthe process for preparing P-mercaptocarboxylic acid
are as follows.
[00031
Patent Document 1 discloses a method in which acrylic acid and
20 thiosulfate are reacted in an aqueous medium, as a result to produce
Bunte salt as a precursor of P-mercaptopropionic acid, and then, the
Bunte salt is hydrolyzed in the presence of an acid.
[0004]
Patent Document 2 discloses a method in which an acrylic acid
25 alkali salt aqueous solution is addedto anaqueous solutionof alkali
hydrosulfide to react in the presence of an alkali hydroxide, the
r,esultant is neutralized with an acid, and a reduction treatment is
performed thereto with zinc.
[0005]
Patent Document 3 discloses a method in which, in a method in
which unsaturated carboxylic acid and a hydrogen sulfide compound
5 are reacted, the obtained reaction medium is acidified to produce
mercaptocarboxylic acid, hydrogen sulfide other than hydrogen
sulfide providedinthe neutralization ofthe unsaturated carboxylic
acid is supplied, 3nd the reaction is performed under the
pressurization of at least 8 bar. In addition, patent Document 3
10 disclosesthatahydrogensulfidecompoundisobtainedbythereaction
of H2S and sodium hydroxide.
[0006]
Patent Document 4 discloses a method in which @-unsaturated
carboxylic acid and hydrogen sulfide are reacted in an aqueous
15 solution in the presence of a basic compound to produce
p-mercaptocarboxylic acid, and the above-described reaction is
performed under pressure conditions of 3.5 MPaG to 20.0 MPaG.
[0007]
Patent Document 5 discloses a method in which when unsaturated
20 nitrile is added to an aqueous solution of alkali hydrosulfide to
react, the resultant is neutralized, and is hydrolyzed to prepare
mercaptocarboxylic acid, sulfur is used.
RELATED DOCUMENT
PATENT DOCUMENT
[Patent Document 11 JapaneseUnexamined Patent PublicationNo.
S59-29633
[PatentDocument21 JapaneseUnexaminedPatent PublicationNo.
2001-187778
[Patent Document 31 PCT Japanese Translation Patent
5 Publication No. 2000-501723
[Patent Document 41 Pamphlet of International Publication No.
W02010/095745
[PatentDocument5] JapaneseUnexaminedPatent PublicatlonNo.
H2-121962
10 DISCLOSURE OF THE INVENTION
[0009]
The techniques of the patent documents described above have the
following problems.
[ OOlO]
15 In the reaction in Patent document 2, it is necessary to use
alkali hydrosulfide as a raw material. However, since
dithiodicarboxylic acid is largely produced as a by-product, the
reaction yield was decreased. In addition, it is possible Po obtain
P-mercaptocarboxylic acid by reduction of the dithiodicarboxylic
20 acid. However, since the used amount of a reducing agent becomes
large, manufacturing cost is increased, and there was a problem in
that waste is increased after the reaction. Moreover, as described
in paragraph [00071, the method in the documents is characterized
in that hydrogen sulflde is not used.
25 [OOll]
In PatentDocument3 or4, since the reactionwasperformedunder
the pressurization, and it was necessary to maintain a pressurized
s t a t e , the manufacturing process was complicated. In addition, it
i s necessary t o separately provide manufacturing equipment for
pressurizatxon and pressure-resistant apparatus, and burden of
manufacturing cost is increased. Moreover, i n the comparative
5 examplelinPatentdocument4describesthatthereactionisperfomed
a t atmospheric pressure. However, there was room for improving the
r e a c t i o n y i e l d .
[0012]
The present inventionhasbeenmade t o solve the above-described
10 problems, and can be descrxbed as follows.
[I] A process for preparing /3-mercaptocarboxylic acld
representedbythefollowingGenera1 Formula (3) comprising: reacting
hydrogen sulfide, a l k a l i hydroxide represented by a formula: XOH (X
represents Na or K) , and unsaturated carboxylic acid represented by
15 the following General Formula (1) under atmospheric pressure t o
obtain a r e a c t i o n s o l u t i o n including a compound represented by the
following General Formula (2) , and n e u t r a l i z i n g t h e reaction
solution i n an acid, i n which the amount of the a l k a l i hydroxide is
equaltoorgreaterthanthetotalmoles oftheunsaturatedcarboxylic
20 acid and the hydrogen s u l f i d e .
(:n Formula (I), each of R' and R' independently represents hydrogen
or an alkyl group of C 1 t o C4, and may be the same as or d i f f e r e n t
from each o t h e r . )
5 [0016]
(In Formula ( 2 ) , R1 and R2 have the same d e f i n i t i o n as i n Formula (I),
X has the same definition as i n a l k a l l hydroxide represented by a
formula: XOH.)
[0017]
(In Formula ( 3 ) , R' and R2 have the same d e f i n i t i o n as i n Formula (1) .)
[0019]
[21 The process for preparing p-mercaptocarboxylic acid
15 describedin [ l l , inwhichthestepforobtainingthereactionsolution
1s performed i n the presence of s u l f u r .
[0020]
[31 The process for preparing p-mercaptocarboxylic acid
describedin [I] or [ 2 1 , inwhichthe s t e p o f n e u t r a l i z i n g t h e reaction
20 solution i n an acid lncludes a step i n which dithiodicarboxyllc acid
produced from p-mercaptocarboxylic acid is reduced by a metal.
[0021]
The "underatmosphericpressure"inc1udes a fine pressurization
! state generated at the time of blowing hydrogen sulfide, and is in ~ the range of about 0.09 MPa to 0.13 MPa.
5 roo221
i
According to the present invention, it is possible to obtain
i
mercaptocarboxylic acid with high yield under atmospheric pressure.
In addition, it is possible to suppress the production of
dithiodicarboxylic acid as a by-product at the time of neutralizing
10 the reaction solution using hydrogen sulfide as a raw material, and
it is possible to provide a simplified method industrially.
!
I
I DESCRIPTION OF EMBODIMENTS
i [0023]
15 Hereinafter, the invention will be described.
The process for preparing P-mercaptocarboxylic acid of the
present invention has the following Steps a and b.
Each step will be described in order.
[0024]
[Step a1
Hydrogen sulfide, alkali hydroxide represented by a formula:
XOH (XrepresentsNaorK) andunsaturatedcarboxylicacidrepresented
by the following General Formula (1) are reacted under atmospheric
pressure, whereby a reaction solution containing the compound
represented by the following General Formula (2) is obtained.
roo251
In Formula (I), each of R1 and R~ independently represents
hydrogen or an alkyl group of C1 t o C4, and may be the same as or
5 d i f f e r e n t from each other.
[0027]
[0028]
In Formula ( Z ) , R1 and R2 have the same d e f i n i t i o n as in Formula
10 ( l ) , X has the same d e f i n i t i o n as i n a l k a l i hydroxide represented
by a formula: XOH.
[0029]
In Step a, the amount of the a l k a l i hydroxide is equal t o or
greater than the t o t a l moles of the unsaturated carboxylic acid
15 represented by General Formula (1) and the hydrogen s u l f i d e . Thus,
it is a l s o p o s s i b l e t o obtainmercaptocarboxylic acidwithhigh yield
under atmospheric pressure.
Moreover,theamountofthealkalihydroxldeispreferablyequal
20 t o o r g r e a t e r than 1 tlme, more preferably equal t o o r g r e a t e r than
acid and the hydrogen sulfide. After the reaction is completed, i f
the amountofacidforneutralizingthe r e a c t i o n s o l u t l o n i s i n c r e a s e d ,
theupper l i m i t v a l u e a f f e c t s a n l n c r e a s e i n c o s t . Fromtheviewpolnt
of t h i s , the upper l i m i t value is equal t o or l e s s than 5 times,
5 preferably equal t o o r l e s s than 4 times, and more preferably equal
t o o r l e s s than 2.5 times. These upper l i m i t values and lower l i m i t
values can be a r b i t r a r i l y combined.
In the present invention, Step a can be performed by a method
described beiow.
10 [0031]
(1) Unsaturated carboxylic acid represented by General Formula
(1) is added t o an aqueous solution of a l k a l i hydroxide t o produce
a s a l t is formed. Next, hydrogen s u l f i d e is blown t o react with
unsaturated carboxylic acid s a l t .
15 (2) Hydrogen s u l f i d e is blowninto anaqueous solution of a l k a l i
hydroxide, and then, unsaturated carboxylic acid represented by
General Formula (1) i s added thereto, whereby reaction occurs.
[0032]
Moreover, i n the methods (1) and ( 2 ) , the example i n which
20 unsaturated carboxylic acld is added is described. However, a l k a l i
saltofunsaturatedcarboxylicacidwhichispreparedinadvanceusing
analkalihydroxidemaybeused. I n t h i s case, Stepacanbeperformed
by a method (3) described below.
LO0331
25 (3) Hydrogensulfide is blownintoanaqueous s o l u t i o n o f a l k a l i
hydroxide, and'then, aqueous solution containing a l k a l i s a l t of
unsaturated carboxylic acid which i s separately prepared by adding
unsaturated carboxylic acid t o the aqueous solution of a l k a l i
hydroxide i s added thereto, whereby reaction occurs.
Moreover, i n t h e case ofthemethod ( 3 ) , the amount o f t h e a l k a l i
hydroxide includes an amount o f t h e a l k a l i hydroxide u s e d t o produce
5 the a l k a l i s a l t of unsaturated carboxylic acid i n advance.
roo341
I n s t e p a, as theunsaturatedcarboxylic acidof General Formula
(1) i n which preferably, each of R1 and R2 independently represents
hydrogen or a methyl group, s p e c i f i c a l l y , a c r y l i c acid, methacrylic
10 acid and crotonic acid can be exemplified. In the case where
P-mercaptopropionic acid used i n a p l a s t i c lens monomer is prepared,
a c r y l i c acid can be used.
LO0351
Alkali hydroxide is representedby a formula: XOH (X represents
15 Na or K ) , and X is preferably sodium. Alkali hydroxide is used as
an aqueous s o l u t i o n a s described i n the above-described method.
Alkali hydroxide may be dissolved i n a mixed solvent of water and
alcohol, andalcohoJmaybe separatelyaddedthereto. Siriceasolvent
recovery step is not needed, the above method is advantageous from
20 the viewpoint of productivity improvement compared t o methods using
an organic solvent i n the r e l a t e d a r t .
As hydrogen sulfide, hydrogen s u l f i d e which is derived from
petroleum refining, and hydrogen s u l f i d e which is synthesized by
25 hydrogenation of s u l f u r can be exemplified. In Step a, i n the case
where hydrogen s u l f i d e i s supplied t o an aqueous solution of a l k a l i
hydroxide, hydrogensulfidegasisused. However, liquefiedhydrogen
10
sulf~deisusuallyuseds ince storage stabllitythereof is excellent.
The added amount of hydrogen sulfide is preferably equal to or
greater than 1.0 equivalent weight, and more preferably equal to or
5 greater than 1.5 equivalent with respect to the unsaturated
carboxylic acid. The upper limit value is equal to or less than 9.0
equivalent, preferably equal to or less than 5.0 equivalent, andmore
preferably equal tc or less than 3.0 equivalent. These upper limit
value and lower limit value can be arbitrarily combined.
10 [0038]
A hydrogen sulfide gas can be supplied to the aqueous solution
of alkali hydroxide while a temperature of the aqueous solution is
maintainedatthe range of O°Cto 50°C. Thus, solubilityofhydrogen
sulfide gas is improved, and the reaction rapidly proceeds. After
15 hydrogen sulfide gas is supplied, the reaction is usually performed
in the temperature range of 20°C to 150°C, preferably in the
temperature range of 50°C to 140°C, and more preferably in the
temperature range of 80°C to 130°C. The temperature*range is
preferable from the viewpoint of a reaction rate and of reducing the
20 production amount of by-products (dithiodicarboxylic acid and
thiodicarboxylic acid). The reaction time can be suitably selected
depending on the reaction temperature. The reaction time is usually
in the range of 0.5 hours to 20 hours, preferably in the range of
1 hour to 15 hours, more preferably in the range of 2 hours to 10
25 hours, and st111 more preferably in the range of 3 hours to 10 hours.
In addition, in Step a, the reaction can be performed in the
presence of sulfur in order to promote the reaction. Thus, the
reaction of mercaptocarboxylic acid can be completed in a shorter
time .
The added amount of sulfur is in the range of 0.01 mol% to 10
mol%, preferablyintherangeofO.lmol%t05mol%, andmorepreferably
in the range of 0.1 mol% to 3 mol% with respect to the unsaturated
carboxylic acid from the viewpoint of the above-described effect.
The addition method is not particularly limited, and at the time of
10 adding unsaturated carboxylic acid or alkali salt of unsaturated
carboxylic acid, these are preferably present in aqueous solution.
[00411
According to Step a, reaction solution including the compound
represented by General Formula (2) can be-obtained. The reaction
15 solutionincludesthiodicarboxylicacidinadditiontothis compound.
[00421
[Step bl
The reaction solution obtained in Step a is neutralized with
an acid to produce P-mercaptocarboxylic acid represented by the
20 following General Formula (3) from the compound represented by
General Formula (2).
LO0431
In Formula ( 3 ) , R' and R' have the same definition as in Formula
As an acid, mineral acids such as sulfuric acid, hydrochloric
5 acid, nitric acid and phosphoric acid, and lower carboxylic acids
such as formic acid, and acetic acid can be used.
The acid is us~di n an amount that the reaction system exhibits
acidity, andusually, the range of 0.8 equivalentsto1.2 equivalents
is suitable with respect to alkali hydroxide which is used in the
reaction. At the time of adding, it is preferably performed while
checking a pH of the reaction solution with a pH meter, and pH is
set to be in the range of 1 to 3.
LOO471
According to Step a, a reaction solution including
P-mercaptocarboxylic acid represented by General Formula (3) and
thiodicarboxylic acid can be obtained. In addition to these
compounds, the reaction solution contains dithiodicarboxylic acid
which is produced from P-mercaptocarboxylic acid and the like.
[0048]
[Reduction Step]
In the present invention, a step in which produced
dithiodicarboxylic acid is reduced by a metal is included from the
viewpoint of improving the yield of P-mercaptocarboxylic acid.
Moreover, the reduction step can be performed after Step b
(neutralizing step) or simultaneously with Step b.
[,00491
13
In the reducing step, p-mercaptocarboxylic acid which is a
t a r g e t substance is not immediately obtained from the reaction
mixture a f t e r n e u t r a l i z a t i o n . A reducing agent is added t o the
solution a f t e r the reaction is completed, or the r e a c t i o n s o l u t i o n
5 obtainedbythe neutralization, anda reductionreaction is performed
under acidic conditions. Thus, dithiodicarboxylic acid which is a
by-product can be converted t o p-mercaptocarboxylic acid, and the
improvement of t h e y i e l d can be achieved.
10 A metal which is a reducing agent includes zinc, iron and t i n
andthe l i k e . Amongthese, iron i s preferablyusedfromtheviewpoint
ofeconomicefficiencyandreductionoftheburdenonthe environment.
Moreover, these reducing agents may used s i n g l y o r i n a combination
I
I of two or more kinds thereof. The used amount of the reducing agent
15 is p r e f e r a b l y i n t h e range of 1.0moleto 5moles, andmore preferably
i n the range of 1.2 moles t o 3 moles with respect t o 1 mole of
dithiodicarboxylic acid which is obtained as a by-product fromthe
viewpoint of improving t h e y i e l d and economic efficiency.
[0051]
2 0 In the process for preparing of the present invention, the
production amount of dithiodicarboxylic acid is small compared t o
amethodinwhichthe NaSHis added, and therefore, t h e r e a c t i o n yield
of p-mercaptocarboxylic acid can be improved. In addition, since
the production amountofdithiodicarboxylic a c i d i s small, the amount
25 of waste derived from metals used i n the reduction can be reduced.
Since p-mercaptocarboxylicacidis dissolvedinanaqueouslayer
obtained after the neutralization, it is extracted from the aqueous
layer by an organic solvent. The organic solvent includes ethyl
acetate, butylacetate, chloroform, dichloromethane, diethylether,
isopropylether, methyl ethyl ketone andisobutylketone andthe like,
5 and it is preferably used ethyl acetate and butyl acetate.
[0053]
After the extraction, the organic solvents are removed by
concentration undez reduced pressure or atmospheric pressure, and
mercaptocarboxylic acid which is a target substance can be obtained
10 by performing a distillation refinement. Moreover, the aqueous
solution obtained after the extraction is an aqueous solution of
inorganic salts such as high concentration sodiumsulfate or sodium
chloride, and for example, an aqueous solution of high purity sodium
sulfate can be used. In addition, if crystals are precipitated from
15 high concentration sodium sulfate solution, the precipitated
crystals can be used as extremely high purity sodium sulfate.
Furthermore, since organic substance and nitrogen compounds are
rarely contained in the waste liquid, there is no the influence on
the environment, pollution treatment is also very simple and
20 economical.
[0054]
In the case of being purified by distillation, distillation
apparatus used for distillation is not particularly limited, and
known distillation apparatus such as a batch type distillation
25 apparatus, a continuous distillation apparatus and a tower type
distillation apparatus can be used. In the case where industrially
distilling a large amount, the continuous distillation apparatus
composed of a heater, a rectifier and a condenser is preferably used
from the viewpoint of stabilization of quality and productivity
improvement.
[00551
5 In addition, after distillation, thiodicarboxylic acid which
is aby-product isincludedinthe residue. The distillation residue
can be returnedto Step a again (recycling step). Thiodicarboxylic
acid which is included in the distillation residue can be used as
a raw material of P-mercaptocarboxylic acid. At this tlme, from the
10 vi-ewpolnt of fluidlty of the distillation residue, after the
temperature was increased to give fluidity thereto, or the
distillation residue was diluted with a solvent, the distillation
residue was returned to the reaction step, and it can be provided
to the reaction. In addition, in the distillation step, without
15 distilling off the total amount of the P-mercaptocarboxylic acid,
distillation ending at a state in which P-mercaptocarboxylic acid
was in the range of 5% to 50%, and preferably in the range of 10%
to 30% in the distillation residue, it was returned to the reaction
stepas a ~-mercaptocarboxylicacidsolutionofthiodicarboxylicacid,
20 and it can also be provided to the reaction.
By repeatedly performing the step, a final yield of
P-mercaptocarboxylic acid can be improved.
[00561
The present invention has been described above, and other
25 configuration can be also employed within a range not interfering
wlth the effect of the present invention.
[Examples]
LO0571
Hereinafter, the present invention will be further described
in more detail with Examples, and the scope of the present invention
is not limited to Examples.
5 [00581
(Example 1)
A 5-necked flask provided with a stlrring apparatus, a
thermometer, a coollng tube, a dropplng funnel and a blowing tube
was prepared, 36.3 g (0.88 moles) of 97% sodlum hydroxide and 43.3
10 g of water were introduced thereto, and the resultant was stlrred
until it became uniform. While maintaining the inner temperature
of the flask at the range of 45'C to 50°C by heating the flask in
an oil bath, 14.4 g (0.20 moles) of acrylic acid was added dropwise
from the dropping funnel over 0.5 hours.
15 Afterthedroppingended, 12.6g (0.37moles) ofhydrogensulfide
gas was blown into the reaction solution through the flow meter from
a liquefied hydrogen sulfide bombe (manufactured by Sumitomo Seika
Chemicals Co., ,Ltd.) at the same temperature over 88 minutes. After
the blowing ended, the temperature was raised to 100°C, and reaction
20 was performed at the same temperature over 8 hours. Moreover, when
quantitative analysis of the reaction solution was performed by a
HPLC after five hours of the reaction initiation, 76.1 mol% of
P-mercaptopropionic acid sodium salt, 23.1 mol% of thiodipropionic
acid sodium salt and 0.3 mol% of dithiodipropionic acid sodium salt
25 as a by-product were produced.
~fterth e reaction ended, as a result of quantitative analysis
qf the reaction solution, 86mol% of P-mercaptopropionic acid sodium
salt, and 13 mol% of thiodipropionic acid sodium salt and 0.4 mol%
of dithiodipropionic acid sodiumsalt as a by-product were produced.
While bubbling nitrogen gas into the reaction system, 129.5 g
(0.462 moles) of 35% aqueous sulfuric acid was added dropwise over
2.5 hours to neutralize the reaction solution. Hydrogen sulfide
generated at this time was discharged from the upper portion of the
cooling tube out of the system. In addition, in the reaction mass
composition after the neutralization, P-mercaptopropionic acid was
86 mol%, and thiodipropionic acid and dithiodipropionic acid which
are by-products were 13 mol% and 0.3 mol%, respectively.
Afterthedegassingended, 18.0 gofbutylacetatewasintroduced
thereto, and an extraction operation was performed. 18.0 g of butyl
acetate is further introduced to the aqueous layer obtained by a
separation, and the same extraction operation was performed three
times.
After the butyl acetate layers obtained by the extraction of
three times were combined into one, butyl acetate was removed under
reduced pressure using an evaporator. The obtained concentrated
liquid was introduced into a kettle of a distillation apparatus with
a single pipe, anddistillationwasperformedunderareducedpressure
of'1.2 KPa. Distillation ended when the kettle temperature is
increased up to 150°C. The residue in the kettle had fluidity even
at 100°C. As the main fraction, 17.5 g (0.165 moles) of
P-mercaptopropionic acidhaving apurity of 99.9% was obtained. The
yield with respect to acrylic acid was 82.5%.
/0059]
(Example 2)
A 5-necked flask provided with a stirring appa.catus, a
thermometer, a cooling tube, a dropping funnel and a blowing tube
was prepared, 36.3 g (0.88 moles) of 97% sodium hydroxide and 43.3
g of water were introduced thereto, and the resultant was stirred
5 until it became uniform. While maintaining the inner temperature
of the flask at the range of 45OC to 50°C by heating the flask in
an oil bath, 14.4 g (0.20 moles) of acrylic acid was added dropwise
from the dropping funnel over 0.5 hours.
Afterthedroppingended, 12.6 g (0.37moles) of hydrogensulfide
10 gas was blown into the reaction solution through the flow meter from
a liquefied hydrogen sulfide bombe (manufactured by Sumitomo Seika
Chemicals Co., Ltd. at the same temperature over 88 minutes. After
the blowing ended, the temperature was raised to 100°C, and reaction
was performed at the same temperature over 8 hours.
After the reaction ended, when quantitative analysis of the
reaction solution was performed by a HPLC, 86.1 mol% of
P-mercaptopropionic acid sodium salt, and 12.9 mol% of
thiodipropionic acid sodium salt and 0.4 mol% of dithiodipropionic
acid sodium salt as a by-product were produced.
2 0 After 0.04 g (0.0007 moles) of Fe powder was introduced into
the reaction system, while bubbling nitrogen gas thereinto, 129.5
g (0.462 moles) of 35% aqueous sulfuric acid was added dropwise over
2.5hourstoreduceandtoneutralizethe reactionsolution. Hydrogen
sulfide generated at this time was discharged from the upper portion
25 of the coollng tube out of the system. In the reaction mass
composition after the neutralization, P-mercaptopropionic acid was
8,6.5mol%,t h i o d l p r o p ~ o n ~ c a c i d w h l c haibsy -product was 12.9moles,
and dithlodlpropionic acld was not detected.
[0060]
(Example 3)
A 5-necked flask provlded wlth a s t l r r i n g apparatus, a
5 thermometer, a cooling tube, a dropplng funnel and a blowing tube
was prepared, 36.3 g (0.88 moles) of 97% sodlum hydroxide and 43.3
gofwaterand0.072 g (0.0022moles) ofsulfurwereintroducedthereto,
and the r e s u l t a n t !Jas s t i r r e d u n t i l it became uniform.
Whilemaintainingtheinnertemperature o f t h e f l a s k a t t h e range
10 of 45'C t o 50°C by heating the flask i n an o i l bath, 1 4 . 4 g (0.20
moles) of a c r y l i c acid was added dropwise fromthe dropping funnel
l
over about 0.5 hours.
Afterthedroppingended, 12.6 g (0.37moles) ofhydrogensulflde
gas was blown i n t o t h e r e a c t i o n s o l u t i o n through the flow meter from
15 a liquefied hydrogen s u l f i d e bornbe (manufactured by Sumitomo Seika
Chemicals Co., Ltd.) a t the same temperature over 88 minutes. After
the blowing ended, the temperature was raised t o 100°C, and reaction
was i n i t i a t e d . When the reaction wag conducted while performing a
lap analysis of the reaction mass, 84.0 mol% of p-mercaptopropionic
20 acid sodium s a l t , and 1 4 . 9 mol% of thiodipropionic acid sodium s a l t ,
0.5 mol% of dithiodipropionic acid sodium s a l t as a by-product were
produced a f t e r two hours of reaction i n i t i a t i o n .
When the r e a c t i o n e n d e d a f t e r fivehours of r e a c t i o n i n i t l a t l o n ,
8 7 . 4 mol% of p-mercaptoproplonlc acid sodium s a l t , and 1 1 . 8 mol% of
25 thlodlpropionic acid sodium s a l t and 0.8 mol% of dithlodiproplonic
acid sodlum s a l t as a by-product were produced.
[0061]
(Example 4)
A 5-necked flask provided with a stirring apparatus, a
thermometer, a cooling tube, a dropping funnel and a blowing tube
was prepared, 47.0 g (1.14 mo1.e~) of 97% sodium hydroxide, 54.5g of
5 water and 0.072 g (0.0022 moles) of sulfur were introduced thereto,
and the resultant was stirred untll it became uniform.
Whilemaintainingtheinnertemperature ofthe flaskatthe range
of 45'C to 50°C by heating the flask in an oil bath, 14.4 g (0.20
moles) of acrylic acid was added dropwise from the dropping funnel
10 over 0.5 hours.
Afterthedroppingended, 17.79 (0.52moles) of hydrogensulfide
gas was blown into the reaction solution through the flow meter from
a liquefied hydrogen sulfide bornbe (manufactured by Sum~tomo Seika
Chemicals Co., Ltd. ) at the same temperature over 90 minutes. After
15 the blowing ended, the temperature was raised to 100°C, and reaction
was perfoned at the same temperature over 8 hours.
After the reaction ended, when quantitative analysis of the
reaction soluLion was performed by a HPLC, 94.8 mol% of
P-mercaptopropionicacidsodiurnsalt, and4.6mol% ofthiodipropionic
acid sodium salt and 0.2 mol% of dithiodipropionic acid sodium salt
as a by-product were produced.
LO0621
(Example 5)
An operation was performed in the same manner as Example 1, and
17.5 g (0.165 moles) of P-mercaptopropionic acid having a purity of
99.9% as a main fraction, 2.8 g (15.7% by weight (0.004 moles) of
P,-mercaptopropionic acid, 81.5% by weight (0.012 moles) of
thiodipropionic acid, and 2.3% by weight (0.0003 moles) of
di~thiodipropionic acid) as a residue (distillation residue (A) ) of
di-stillation kettle were obtained (Reaction 1).
A 5-necked flask provided with a stirring apparatus, a
5 thermometer, a cooling tube, a dropping funnel and a blowing tube
was prepared, 36.3 g (0.88 moles) of 97% sodium hydroxide and 43.3
g of water were introduced thereto, and the resultant was stirred
until it became uniform. 2.8 g (composition ratio: 15.7% by weight
of P-mercaptopropionic acid, 81.5% by weight of thiodipr~~ioniacc id
10 and2.3%byweightofdithiodipropionicacid) of distillation residue
(A) in a state with fluidity was slowly added to the sodium hydroxide
aqueous solution while keeping the temperature at the range of 90°C
to 95OC. While maintaining the inner temperature at the range of
45'C to 50°C, 12.24 g (0.17 moles) of acrylic acid was added dropwise
15 from the dropping funnel over 0.5 hours.
Afterthedroppingended, 12.6 g (0.37moles) ofhydrogen sulfide
gas was blown into the reaction solution through the flow meter from
a liquefied hydrogen sulfide bombe (manufactured by Sumitorno Seika
Chemicals Co., Ltd. ) at the same temperature over 90 minutes. After
20 the blowing ended, the temperature was raised to 100°C, and reaction
was performed at the same temperature over 8 hours.
After the reaction ended, when quantitative analysis of the
reaction solution was performed by a HPLC, 0.172 mol% of P-mercapto
propionic acid sodium salt, and 0.013 mol% of thiodipropionic acid
25 sodium salt and 0.0006 mol% of dithiodipropionic acid sodium salt
as a by-product were produced.
Neutralization, extraction and distillation operation were
performed in the same manner as Example 1, and 17.5 g (0.165 moles)
of p-mercaptopropionic acid having a purity of 99.9% was obtained
as a main fraction (Reaction 2). The yield of p-mercaptopropionic
acid was 89.2% with respect to acrylic acid (14.4 g + 12.2 g ) used
5 in the first reaction and the first reaction of distillation residue
recycling.
In addition, 2.9 g (15.3% by weight (0.004 moles) of
p-mercaptopropionic acid, 79.3% by weight (0.013 moles) of
thiodipropionic acid, and 4.4% by weight (0.0006 moles) of
10 dithiodipropionic acid) as a residue (distillation residue ( B ) ) of
distillation kettle were obtained.
The raw materials supplied to a reaction in Example 5, and
compositions ofthe obtained reaction product are describedin Table
1.

[0064]
(Example 6)
Reactionwas performedinthe samemanner as Example 1 (Reaction
1). Then, using the distillation residue (A) obtained in Reaction
5 1, a reaction was performed under the same conditions as Example 4
and the amounts of raw materials supplied to a reaction were changed
as described in Table 2 (Reaction 2). In the same manner, using the
distillation residue obtained in the previous reaction, a reaction
was performed under the same conditions as Example 4 and the amounts
10 of raw materials supplied to a reaction was changed as described in
Table 2 at four times (Reactions 3 to 6).
In this manner, by using the obtained distillation residue in
anextreaction, arecyclingwasperformedatfivetimes. Asaresult,
the yield of P-mercaptopropionic acid (purity 99.9%) obtained as a
15 distillation main fraction was 94.4% with respect to acrylic acid
used for performing the first reaction (Reaction 1) and the first
to fifth recycling (Reactions 2 to 6)
The raw materials supplied to a reaction in Example 6, and
compositions ofthe obtained reaction product are describedinTable
20 2 .
coo651
Table 2
4 1 0.88 I 0.17 I 0.37 C / 0.165 193.0 1 0.0113 0.0012 1
5 10.88 / 0.17 10.37 1 D 1 0.165 1 93.8 lE 0.004 1 0.013 1 0.0015
6 10.88 0.17 1 0.37 / E / 0.165 1 94.4 1 F / 0.004 1 0.013 / 0.0018
*: (cumulative production amount (mol) of P-mercaptopropionic acid / cumulative used amount (mol) of
acrylic acid) x 100
[0066]
(Comparative Example 1)
A 5-necked flask provided with a stirring apparatus, a
thermometer, a cooling tube, a dropping funnel and a blowlng tube
was prepared, 21.0 g (0.51 moles) of 97% sodium hydroxide and 41.6
g of water were introduced thereto, 29.6 g (0.37 moles) of 70% sodium
hydrosulfide (manufactured by Wako Pure Chemical Industries, Ltd.)
was further introd~:ced thereto, and the resultant was stirred until
it became uniform.
10 Whilemaintalnlngthe Innertemperature ofthe flaskatthe range
of 45'C to 50°C by heating the flask in an oil bath, 14.4 g (0.20
moles) of acrylic acid was added dropwise fromthe dropping funnel
over about 0.5 hours. After the dropping ended, the temperature was
raised to 100°C, and reaction was performed at the same temperature
over 8 hours.
After the reaction ended, when analysis of the reaction mass
was performedbyaHPLC, 87.3mol% of P-mercaptopropionicacidsodium
salt, and 12.0 1~01%of thiodipropjonic acid sodium salt and 0.7 mol%
of dithiodipropionic acid sodiumsaltas a by-product were produced.
While bubbling nitrogen gas into the reaction system, 129.5 g
(0.462 moles) of 35% aqueous sulfuric acid was added dropwise over
2.5 hours to neutralize the reaction solution. Hydrogen sulfide
generated at this time was discharged from the upper portion of the
condenser out of the system. In addition, in the reaction mass
composition after the neutralization, P-mercaptopropionic acid was
79.3 mol% . As a by-product, thiodipropionic acid was 12.0 mol% and
dithiodipropionic acid was increased to 8.7 mol%.
After the degassing ended, the operations in the same manner
as Example 1 were performed in the same manner as Example 1, and 16.2
g (0.152 moles) of P-mercaptopropionic acid having a purity of 99.9%
was obtained as a main fraction. The yield with respect to acrylic
acid was 76.1%.
[0067]
(Comparative Example 2)
A 5-necked fl3sk provided with a stirring apparatus, a
thermometer, a cooling tube, a dropping funnel and a blowing tube
was prepared, 20.6 g (0.50 moles) of 97% sodium hydroxide and 43.3
g of water were introduced thereto, and the resultant was stirred
until it became uniform.
I Whilemaintainingtheinnertemperature ofthe flaskat the range
~l of 45°C to 50°C by heating the flask in an oil bath, 14.4 g (0.20
:I
1
i
! 15 moles) of acrylic acid was added dropwise fromthe dropping funnel
over about 0.5 hours.
Afterthe droppingended, 12.6 g (0.37moles) ofhydrogensulfide
gas was blown illto the reaction solution through the flow meter from
a liquefied hydrogen sulfide bombe (manufactured by Sumitorno Seika
20 Chemicals Co., Ltd.) at the same temperature over 88 minutes. After
the blowing ended, the temperature was raised to 100°C, and reaction
was performed at the same temperature over 8 hours.
After the reaction ended, when quantitative analysis of the
reaction mass was performed by a HPLC, 49.3 mol% of
25 P-mercaptopropionic acid sodium salt, and 48.8 mol% of
thiodipropionic acid sodium salt and 1.3 mol% of dithio
acid sodium salt as a by-product were produced.
The results of Examples 1 to 4 and Comparative Examples 1 and
2 are summarized and described in Table 3
I 5 AA: acrylic acid
Table 3
/ p-MPA: p-mercaptopropionic acid sodium salt
Moles of used compound
S: thiodipropionic acid sodium salt
SS: dithiodipropionic acid sodium salt
Addition reactlon
achievement
(mol%/AA)
10 AA: acrylic acid
Reactlon
achievement after
neutrailzatlon
p-MPA: p-mercaptopropionic acid sodium salt
S: thiodipropionic.acid sodium salt
SS: dithiodipropionic acid sodium salt
Appllcationno. 2011-253453, filedonNovember 21, 2011, the content
of which is incorporated herein by reference.
2 9
CLAIMS
1. A process for preparing P-mercaptocarboxylic acid
represented by the following General Formula ( 3 ) , comprising:
5 reacting hydrogen sulfide, alkali hydroxide represented by a
formula: XOH (X represents Na or K) , and unsaturated carboxylic acid
I
represented by the following General Formula (1) under atmospheric
pressure to obtain a reaction solution including a compound
represented by the following General Formula (2); and
10 neutralizing the reaction solution in an acid,
whereinan amount ofthe alkall hydroxide is equal to or greater
I than total moles of the unsaturated carboxylic acid and the hydrogen
sulfide,
wherein, in Formula (I), each of R' and R2 i~~dependently
represents hydrogen or an alkyl group of C1 to C4, and may be the
same as or different from each other,
wherein, in Formula ( 2 ) , R' and R2 have the same definition as
20 in Formula (I), X has the same definition as in alkali hydroxide
represented by a formula: XOH, and
1 whereln, in Formula ( 3 ) , R' and R2 have the same def lnltlon as
I
I ln Formula (1).
I
5 2. The process for preparj.ng P-mercaptocarboxylic acid
according to Claim 1,
wherein the step for obtaining the reaction solution is
performed in the presence of sulfur.
10 3. The process for preparing p-mercaptocarboxyllc acid
according to Claim 1 or 2,
wherein the step of neutralizing the reaction solution in an
acid includes a step in which dithiodicarboxylic acid produced from
P-mercaptocarboxylic acid is reduced by a metal.