SPECIFICATION
PROCESS FOR PREPARING O-MERCAPTOCARBOXYLIC ACID
5 TECHNICAL FIELD
The present invention relates to a process for preparing
P-mercaptocarboxylic acid.
BACKGROUND ART
10 [00021
6-mercaptocarboxylic acid is a compound which 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 forpreparlng P-mercaptocarboxyl~cacid
are as follows.
100031 ,
Patent Document 1 discloses a method in which acrylic acld and
20 thiosulfate are reacted in an aqueous medium, as a result to produce
Bunte salt as a precursor of P-mercaptopropionic acld, and then, the
Bunte salt is hydrolyzed in the presence of an acid.
[00041
Patent Document 2 discloses a method in which an acryllc acid
25 alkali salt aqueous solution is addedto anaqueous solutionof alkali
hydrosulfide to react in the presence of an alkali hydroxide, the
resultant 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 of the unsaturated carboxylic
acid is supplied, and the reaction is performed under the
pressurization of at least 8 bar. In addition, Patent Document 3
10 disclosesthatahydrogensulfide compoundis obtainedbythe reaction
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.
[00081
Patent Document 6 discloses a method in which after alkali
25 hydroxide is added to thiodipropionic acid to make an alkali salt,
the resultant is mixed with an aqueous alkali sulfide solution, and
acidification is performed to prepare p-mercaptopropionic acid.
RELATED DOCUMENT
PATENT DOCUMENT
[0009]
[Patent Document11 JapaneseUnexaminedPatent PublicationNo.
[PatentDocument2] Japanese UnexaminedPatent PublicationNo.
2001-187778
[Patent Document 31 PCT Japanese Translation Patent
Publication No. 2000-501723
10 [Patent Document 41 Pamphlet of International Publication No.
W02010/095745
[PatentDocument5] Japanese UnexaminedPatent PublicationNo.
H2-121962
[Patent Document 61 JapaneseUnexaminedPatent PublicationNo.
15 H4-009363
DISCLOSURE OF THE INVENTION
[OOlO]
The techniques o f t h e patent documents describedabove have the
20 following problems
[0011]
In the reaction i n Patent document 2, an a l k a l i hydrosulfide
is used as a raw material. However, since thiodicarboxylic acid i s
,I,
largely produced as a by-product, the reaction yield was decreased.
25 In addition, it is possible t o obtain P-mercaptocarboxylic acid by
reduction of the d i t h i o d i c a r b ~ x ~ lai ci d. 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. On the other hand, the production amount of
thi~dicarbox~liacc id which is a by-product is decreased by
increasing the amount of alkali hydroxide. However, the amount of
5 acid used in neutralization becomes large, manufacturing cost is
increased, and there was a problem in that waste is increased after
the reaction. Moreover, as describedinparagraph [0007],themethod
in the documents is characterized in that hydrosulfide i.s not used.
[00121
10 In the patent document 3 or 4, the reaction is performed under
the pressurization, dithiodicarboxylic acid is largely produced as
a by-product in these methods also, and the yield is decreased in
the reaction.
[00131
15 In this manner, in the methods disclosed in the related
documents, thiodicarboxylic acid is produced as a by-product, yield
of 6-mercaptocarboxylic acid which is a target compound is low, a
method for further increasingthe yield is complex, andniailufacturing
cost is increased.
20 [00141
The present inventionhas beenmade to solve the above-described
problems, and can be described as follows.
[l] A process for preparing P-mercaptocarboxylic acid
comprising:
25 Step a for reacting a compound represented by a formula: xlzS
(XI represents hydrogen, Na or K) or a compound represented by a
formula: X'SH (xZ represents Na or K), alkali hydroxide represented
by a formula: X~OH (x3 represents Na or K) , and unsaturated carboxylic
acid represented by the following General Formula (1) to obtain a
reaction solution including a compound represented by the following
General Formula (2) and a compound represented by the following
5 General Formula ( 3 ) ,
Step b for neutralizing the reaction solution obtained in Step
a with an acid to obtain a reaction solution including
p-mercaptocarboxy1i.c acid represented by the following General
Formula (4) and a compound represented by the following General
10 Formula (5),
Stepc fordistillation-refiningthe reactionsolutionobtained
in Step b to obtain the P-mercaptocarboxylic acid represented by
General Formula ( 4 ) , and
Step d for returning a distillation residue including the
15 compound represented by General Formula (5) in Step c to Step a.
[00161
(In Formula (I), each of R1 and R2 represents hydrogen or a C1 to C4
20 alkyl group, and may be the same as or different from each other.)
[00171
(In Formula (2) , R1 and R2 have the same definition as in Formula (I),
x4 represents Na or K. x4 of which two are present may be the same
as or different from each other.)
[0020]
(In Formula (3), R1 and R2 have the same definition as in Formula (I),
x4 represents Na or K. R1, R2 or x4 of which two are present
respectively may be the same as or different from each other.)
10 [0021]
[0022]
(In Formula ( 4 ) , R1 and R2 have the same definition as in Formula (1) .)
[0023]
(In Formula (51, R1 and R2 have the same definition as in Formula (1).
R1 and R2 of which two are present respectively may be the same as
or different from each other.)
LOO251
[2] The process for preparing p-mercaptocarboxylic acid
1 described in [I], in which Steps a to d are repeatedly performed.
5 (31 The process for preparing p-mercaptocarboxylic acid
I
I described in [I] or [2], in wh~ch the compound represented by the
formula: X~SH is NaSH.
< [0026]
[4] The process for preparing p-mercaptocarboxyllc acid
10 described in [I] or [21, in which the compound represented by the
formula: ~'2.5 is HzS.
[00271
[5] The process for preparing p-mercaptocarboxylic acid
described in any one of [I] to [4], in which Step a is performed in
15 the presence of sulfur.
According to the present invention, it is possible to obtain
P-mercaptocarboxylic acid with high yield. In other words, the
present invention can provide a simple method in which
20 p-mercaptocarboxyllc acld can be obtained with high yield.
DESCRIPTION OF EMBODIMENTS
[00291
Hereinafter, the invent~on will be described.
The process for preparing p-mercaptocarboxylic acld of the
25 present invention has the following Steps a to d. Each step wlll
be described in order.
[Step a1
A reactlon solutlon including a compound represented by the
following General Formula (2) and a compound represented by the
following General Formula (3) is obtained by reaction of a compound
5 represented by a formula: X'ZS (XI represents hydrogen, Na or K) or
I
I a compound represented by a formula: X'SH (x' represents Na or K),
alkali hydroxide represented by a formula: X~OH (x3 represents Na or
K), and unsaturated carboxylic acid represented by the following
General Formula (1).
In Formula (I), each of R1 and R' represents hydrogen or a C1
to C4 alkylgroup, andmaybethe same as or different fromeach other.
15 lo0331
In Formula (2), R' and R2 have the same definition as in Formula
(I), x4 represents Na or K. x4 of which two are present may be the
20 same as or different from each other.
i I In Formula ( 3 ) , R1 and R' have the same d e f i n i t i o n as i n Formula
(11, x4 represents Na or K. R', R' or x4 of which two are present
5 respectively may be the same as or d i f f e r e n t from each other.
Moreover, i n the compound represented by General E'ormulas ( 2 )
or ( 3 ) , x4 is derived from XI, X' or x3.
[00371
As the compounds represented by the formula: ~ ' $ 5 , HzS, NazS and
10 K2S canbe exemplified. As the compounds representedbythe formula:
X'SH, NaSH and KSH can be exemplified.
[00381
I n S t e p a , a s t h e u n s a t u r a t e d c a r b o x y l l c acidof General Formula
(1) In which preferably, each of R' and R2 independently represents
15 hydrogen or a meLhyl group, s p e c i f i c a l l y , a c r y l i c acid, methacrylic
acid and c r o t o n i c a c i d can be exemplified. In the case where
p-mercaptocarboxyl~ca c ~ d u s e d i n a p l a s t i c l e n s m o n o m e r ipsr epared,
a c r y l i c acid can be used.
[00391
20 Alkali hydroxide is represented by a formula: X~OH (x3 represents
Na or K), and x3 is preferably sodium. Alkali hydroxide is used as
an aqueous solution as described i n the above-described method.
Alkall hydroxide may be dissolved i n a mixed solvent of water and
alcohol, andalcoholmaybe separatelyaddedthereto. Slncea solvent
recovery step is not needed, the above method is advantageous from
the viewpoint of productivity improvement compared t o methods uslng
an organic solvent i n the r e l a t e d a r t .
[0040]
5 In the casewhereH2Sis used, Stepacanbeperformedas follows.
[0041]
(1) Unsaturated carboxylic acid represented by General Formula
(1) is added t o an aqueous solution of a l k a l i hydroxid? t o produce
a s a l t is formed. Next, hydrogen s u l f l d e is blown t o react with
10 unsaturated carboxylic acid s a l t .
( 2 ) Hydrogen s u l f i d e is blownintoan aqueous 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.
[0042]
15 Moreover, i n the methods (1) and ( 2 ) , the example i n which
unsaturated carboxylic acid is added is described. However, a l k a l i
saltofunsaturatedcarboxylicacidwhichispreparedinadvance using
analkalihydroxidemaybeused. In t h i s case, Stepa canbe performed
by a method (3) described below.
20 [0043]
(3) Hydrogen s u l f i d e is blownintoan aqueous 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 is separately prepared by adding
unsaturated carboxylic acid t o the aqueous solution of a l k a l i
25 hydroxide is added thereto, whereby reaction occurs.
Moreover, themethodsdescribedinthe ( 1 ) t o (3) maybeperformed
under atmospheric pressure, or under the pressurization.
roo441
As hydrogen sulfide, hydrogen sulfide which is derived from
petroleum refining, and hydrogen sulfide which is synthesized by
hydrogenation of sulfur can be exemplified. In Step a, in the case
5 where hydrogen sulfide is supplied to an aqueous solution of alkali
hydroxide, hydrogensulfidegasisused. However, liquefiedhydrogen
sulfide is usuallyused since storage stabilitythereof is excellent.
[0045]
The added amount of hydrogen sulfide is preferably equal to or
10 greater than 1.0 equivalent, and more preferably equal to or greater
than 1.5 equivalent with respect tothe unsaturated carboxylic acid.
The upper limit value is equal to or less than 9.0 equivalent,
1 preferably equal to or less than 5.0 equivalent, and more preferably
I
equal to or less than 3.0 equivalent. These upper limit value and
15 lower limit value can be arbitrarily combined.
A hydrogen sulfide gas can be supplied to the aqueous solution
of alkali hydroxide while ,a temperature of the aqueous solution is
maintained at the range of O°Cto 50°C. Thus, solubilityofhydrogen
20 sulfide gas is improved, and the reaction rapidly proceeds. After
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 330°C. The temperature range is
25 preferable from the viewpoint of a reaction rate and of reducing the
production amount of by-products (dithiodicarboxylic acid and
thiodicarboxylic acid). The reaction time can be suitably selected
depending on the reaction temperature. The reactiontlme is usually
i n the range of 0.5 hours t o 20 hours, preferably i n the range of
1 hour t o 15 hours, more preferably i n the range of 2 hours t o 10
hours, and s t i l l more preferably i n the range of 3 hours t o 10 hours.
5 [0047]
On the other hand, i n Step a, i n the case where NazS, KzS, NaSH
or KSH are used, an addition order is not p a r t i c u l a r l y limited, and
a t l e a s t one compo~lnd selected from these compounds, NaOH, and
unsaturated carboxylic acid are mixed t o react, the reaction can be
10 also performed under the pressurization.
[0048]
In Step a, i n the case where NazS, K2S, NaSH or KSH are used,
the used amount of these is preferably equal t o or greater than 1 . 0
equivalent, and more preferably equal t o or greater than 1.5
15 equivalent with respect t o the unsaturated carboxylic acid. The
upper l i m i t value is equal t o or l e s s than 9.0 equivalent, preferably
equal t o o r l e s s than 5.0 equivalent, and more preferably equal t o
or l e s s than 3.0 equivalent. These upper l i m i t values ancilower,limit
values can be a r b i t r a r i l y combined.
20 [0049]
The used amount of a l k a l i hydroxide is i n the range of 1
equivalent t o 10 equivalents, and preferably i n the range of 2
equivalent t o 5 equivalentwithrespect t o t h e unsaturatedcarboxylic
acid
25 [0050]
An addition order of a t l e a s t one compound selected from NazS,
K2S, NaSH or KSH, a l k a l i hydroxide and unsaturated carboxylic acid
is not particularly limited. A temperature range in the addition
is preferably in the range of O°C to 50°C.
[00511
After the addition, usually, the reaction is performed in the
5 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 preferab1.e from the
viewpoint of a reaction rate and of reducing the production amount
of by-products (dithiodicarboxylic acid and thiodicarboxylic acid) .
10 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 hours, and still more
preferably in the range of 3 hours to 10 hours.
15 [0052]
As the compound represented by a formula: ~'2.5, H2S is preferable
from the viewpoint of suppressing the production amount of
dithiodicarboxylic acid, and as the compound represented by a
formula: X'SH, NaSH is preferable from the viewpoint of the difficulty
20 in handling ability of H2S gas.
[00531
In addition, in Step a, the reaction can be performed in the
presence of sulfur in order to promote the reaction. Thus, it is
possible to obtain P-mercaptocarboxylic acid with higher yield.
The added amount of sulfur is in the range of 0.01 mol% to 10
mol%, preferablyintherangeof O.lmol%to5mol%, 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
I
I
I
adding unsaturated carboxylic acid or alkali salt of unsaturated
1 I
5 carboxylic acid, these are preferably present in aqueous solution.
I
I By Step a, a reaction solution which includes the compound
represented by General Formula (2) and the compound represented by
General Formu1.a ( 3 ) is obtained.
10 [Step bl
The reaction solution obtained in Step a is neutralized with
3
an acid to obtain a reaction solution including P-mercaptocarboxylic
acid represented by the following General Formula (4) and a compound
represented by the following General Formula ( 5 ) .
15 LO0561
2 0 In Formulas (4) and ( 5 ) , R1 and R2 have the same definition as
In Formula (1). In Formula (51, R1 and R2 of which two are present
respectively may be the same as or different from each other.
[00591
As the acids, inorganic acids such as sulfuric acid,
hydrochloric acid, nitric acid and phosphoric acid, and lower
carboxylic acids such as formic acid, and acetic acid can be used.
The acid is used in an amount that the reaction system exhj-bits
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.
By Step b, a reaction solution including P-mercaptocarboxplic
acid represented by General Formula (3) and thiodicarboxylic acid
canbe obtained. In addition to these compounds, dithiodicarboxylic
acid which is produced from p-mercaptocarboxylic acid is included
in the reaction solution.
[00611
[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.
LO0621
In the reducing step, 0-mercaptocarboxylic acid which is a
target substance is not immediately obtained from the reaction
mixture after neutralization. A reducing agent is added to the
solution after the reaction is completed, or the reaction solution
I
1 obtainedbythe neutralization, anda reduction reaction is performed
I under acidic conditions. Thus, dithiodicarboxylic acid which is a
I
I by-product can be converted to p-mercaptocarboxylic acid, and the
I :
I
5 improvement of the yield can be achieved.
A metal which is a reducing agent includes zinc, iron and tin
andthe like. Amonsthese, ironis preferablyused fromtlheviewpoint
ofeconomicefficiencyandreductionoftheburdenonthe environment.
10 Moreover, these reducing agents may used singly or in a combination
of two or more kinds thereof. The used amount of the reducing agent
is preferablyinthe range of 0.4moleto 5moles, andmore preferably
in the range of 0.5 moles to 3 moles with respect to 1 mole of
dithiodicarboxylic acid which is obtained as a by-product from the
15 viewpoint of improving the yield and economic efficiency.
LO0641
[Step cl
In Step c, the reaction solution obtained in Step b is purified
by distillation, and P-mercaptocarboxylic acid represented by
20 General Formula (4) is obtained.
LO0651
Since mercaptocarboxylic acid is dissolved inan aqueous layer
obtained after neutralization of the reaction solution obtained in
Step b, it is extracted from the aqueous layer by an organic solvent.
25 As the organic solvents, ethyl acetate, butyl acetate, chloroform,
dichloromethane, diethylether, isopropylether, methylethyl ketone
and isobutyl ketone can be used, and ethyl acetate and butyl acetate
are preferably used.
100661
After the extraction, the organic solvents are removed by
concentration under reduced pressure or atmospheric pressure, and
5 mercaptocarboxylic acid which is a target substance can be obtained
by performing a distillation refinement. Moreover, the aqueous
solution obtained after the extraction is an aqueous solution of
inorganic salts such as high concentration sodium sulfate or sodium
chloride, and for example, an aqueous solution of high purity sodium
10 sulfate can be used. In addition, if crystals are precipitated from
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
15 the environment, pollution treatment is also very simple and
economical.
LOO671
In the case of being purified by distillation, d~stlllation
apparatus used for distillation is not particularly limited, and
20 known distillation apparatus such as a batch type distillation
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
25 from the viewpoint of stabilization of quality and productivity
improvement.
[Step dl
A distillation residue including a compound (thiodicarboxylic
acid) represented by General Formula (5) in Step c is returned to
Step a.
5 [0069]
Thiodicarboxylic acid which is included in the distillation
residue can be used as a raw material of P-mercaptocarboxylic acid.
At this time, from the viewpoint of liquid-transfer of the
distillation residue, after the temperature was increased to give
10 fluidity thereto, or the distillation residue was diluted with a
solvent, the distillation residue was returnedtothe reaction step,
and it can be provided to the reaction. In addition, in the
distillation step, without distilling off the total amount of the
P-mercaptocarboxylic acid, distillation ending at a state in which
15 P-mercaptocarboxylicacidwasintherangeof5%to50%, andpreferably
inthe range oflO%to 30% inthe distillationresidue, itwas returned
to the reaction step as P-mercaptocarboxylic acid solution of
thiodicarboxylic acid,. and it can also be provided to Lhe reaction.
[0070]
20 In the present embodiment, Steps a to d can be repeatedly
performed.
Moreover, since the compound representedbyGenera1 Formula (5)
is s e p a r a t e l y s u p p l i e d i n S t e p a inwhichanextreactionis performed
afterstepd (recyclingstep),itisnecessarytoappropriatelychange
25 the amount of the raw material depending on the supply amount.
[0071]
In the case where the distillation residue is returned to Step
a, andthenextreactionisperformed, it ispreferablethat the amount
I of the raw material be appropriately changed fromthe viewpoint of
constantly maintaining a yield per each batch.
From the above-described viewpoint, specifically, it is
5 possible to adjust the amount of unsaturated carboxylic acid used
in Step a, and the amount of the compound represented by a formula:
X'~S (XI represent hydrogen, Na or K), the amount of the compound
represented by a formula: X'SH (x2 represent Na or K), or the amount
of alkali hydroxide represented by a formula: X~OH (x3 represent Na
10 or K) which are other raw materials used in Step a based on the amount
of P-mercaptocarboxylic acid andthiodicarboxylic acid contained in
the distillation residue.
[0072]
By repeatedly performing the step, a final yield of
15 P-mercaptocarboxylic acid can be improved.
The present invention has been described above, and other
configuration can be also employed within a range not interfering
with the effect of the present invention.
Example
20 [0073]
Hereinafter, the present invention will be further described
in more detall with the examples, and the scope of the present
invention is not llmited to the examples.
[0074]
25 [Example 11
In Example 1, Reactions 1 to 6 are sequentially performed.
Hereinafter, the reactions will be sequentially described.
(Reaction 1)
A 5-necked flask provlded with a stlrrlng apparatus, a
thermometer, a coollng tube, a dropping funnel and a blowing tube
was prepared, 36.3 g (0.88 mol) of 97% sodlurn hydroxide and 43.3 g
5 of water were introducedthereto, and the resultant was stirreduntil
it. became uniform. While maintaming the inner temperature of the
flask at the range of 45°C to 50°C by heating the flask in an 011
bath, 14.4 g (0.20 nol) of acrylic acld was added dropwise fromthe
dropplng funnel over 0.5 hours.
10 After the dropping ended, 12.6 g (0.37 mol) of hydrosulfide gas
I was blown into the reaction solution through the flow meter from a
liquefied hydrosulfide 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
15 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 mol% of
p-mercaptopropionic acid sodiumsalt, and 13 mol% ofthiodipropionic
acid sodium salt and 0.4 mol% of dithiodipropionic acid sodium salt
20 as a by-product were produced.
After 0.04 g (0.0007 mol) of Fe powder was introduced into the
reaction system, while b l o w i n g n i t r o g e n g a s t h e r e ~ n t o , 129.5 g (0.462
mol) of 35% aqueous sulfuric acid was added dropwise over 2.5 hours
toneutralize the reaction solution. Hydrosulfide generatedatthis
25 time was discharged from the upper portion of the cooling tube out
of the system. In 'the composition of reaction mass after
neutralization, P-mercaptopropionic acid was 86.2 mol%,
thiodipropionlc acid which is a by-product was 13 mol%, and I dlthiodlpropionic acid was not detected.
1
1 Afterthedegassingended, 18.0gofbutylacetatewasintroduced
I
thereto, and an extraction operation was performed. 18.0 g of butyl
5 acetate was further introduced to the aqueous layer obtained by a
I
separating, 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 using
10 an evaporator. The obtained concentratedliquidwas introducedinto
a kettle of a distillation apparatus with a single pipe, and
distillation was performed under vacuum of 1.2 KPa. Distillation
ended when the kettle temperature was increased up to 150°C. As the
main fraction, 17.5 g (0.165 mol) of P-mercaptopropionic acid having
15 a purity of 99.9% was obtained. The yield was 82.5% with respect
to acrylic acid.
The distillation residue (A) of 2.9 g had fluidity even at 90°C,
and in the composition, P-mercaptopropionic acid was 15.5% by weight
(0.004 mol%), and thiodlpropionic acid was 80.0% by weight (0.013
mol%) .
[0075]
(Reaction 2)
An aqueous solution in which 36.3 g (0.88 mol) of 97% sodium
hydroxide and 43.3 g of water were uniformly dissolved was prepared
ina5-neckedflaskprovidedwithastirringapparatus, athermometer,
a cooling tube, a dropplng funnel and a blowing tube, and the
distillation resldue (A) obtalned in Reaction 1 in a state with
fluidity while keeping the temperature at the range of 90°C to 95OC
was slowlyaddedtotheaqueous solution. Whilemaintainingtheinner
temperature at the range of 45'C to 50°C, 12.2 g (0.17 mol) of acrylic
acid was added dropwise from the dropping funnel over 0.5 hours.
After the dropping ended, 12.6 g (0.37 mol) of hydrosulfide gas
was blown into the reaction solution at the same temperature over
gominutes through the flowmeter fromaliquefiedhydrosulfide bornbe
(manufactured by S!lmitomo Seika Chemicals Co., Ltd.). 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, 0.172 rnol of
p-mercaptopropionic acid sodium salt, and 0.013 rnol of
thiodipropionic acid sodiumsalt and 0.0004molof dithiodipropionic
acid sodium salt as a by-product were produced.
Neutralization, extraction and distillation operation were
performed in the same operation as Reaction 1, and 17.5 g (0.165 mol)
of 6-mercaptopropionic acid having a purity of 99.9% was obtained
as a main fraction. A cumulative yield of p-mercaptopropionic acid
(0.165 rnol + 0.165 mol) obtained in Reactions 1 and 2 was 89.2% with
respect to acrylic acid (0.20 rnol + 0.17 mol) used in Reactions 1
and 2 (one recycling).
The distillation residue (B) of 3.0 g had fluidity even at 90°C,
and in the composition, P-mercaptopropionic acid was 14.9% by weight
(0.004mol), andthiodipropionicacidwas 79.3%byweight (0.013mol).
LOO761
(Reactions 3 to 6)
Hereinafter, in the same manner as Reaction 2, the distillation
residue obtained by distillation is returned to reactlon step of the
next reaction to perform a reactlon, and reactions 3 to 6 (four
recycling) were performed.
5 In the above manner, recycling was performed a total of five
times. The used amount of the raw materials in Reactions 1 to 6 and
the cumulat~ve yield of P-mercaptoproplonic acid are shown in Table
1.

LO0781
[Example 21
In Example 2, Reactions 1 to 6 are sequentially performed.
Hereinafter, the reactions will be sequentially described.
(Reaction 1)
A 5-necked flask provided with a stirring apparatus, a
thermometer, a cooling tube, a dropping funnel and a blowing tube
was prepared, 36.3 g (0.88 mol) of 97% sodium hydroxide and 43.3 g
of water and 0.072 g (0.0022 mol) of sulfur were introduced thereto,
and the resultant was stirred 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 mol) of
acrylic acid was added dropwise from the dropping funnel over 0.5
hours.
After the dropping ended, 12.6 g (0.37 mol) of hydrosulfide gas
was blown into the reaction solution at the same temperature over
88 minutes through the flowmeter froma liquefiedhydrosulfide bombe
(manufactured by Sumitomo Seika Chemicals Co., Ltd.). After the
blowing ended, the temperature was raised to 10O0C, and reaction was
initiated. When the reaction was conducted while performing a lap
analysis ofthe reactionmass, 84.0 mol% of @-mercaptopropionic acid
sodium salt, and 14.9 mol% of thiodipropionic acid sodium salt, and
0.5 mol% of dithiodipropionic acid sodium salt as a by-product were
produced 2 hours after the reaction was initiated.
Whenthe reactionended5hours after the reactionwasinitiated,
86.9 mol% of P-mercaptopropionic acid sodium salt; and 11.8 mol% of
thiodipropionic acid sodium salt and 0.8 mol% of dithiodipropionic
acid sodium s a l t as a by-product were produced.
After 0.08 g (0.0014 mol) of Fe powder was introduced i n t o the
reactionsystem, w h l l e b l o w i n g n ~ t r o g e n g a s t h e r e i n t o ,1 29.5g ( 0 . 4 6 2
mol) of 35% aqueous s u l f u r i c acid was added dropwlse over 2.5 hours
5 t o n e u t r a l i z e the r e a c t i o n s o l u t i o n . Hydrosulfide generated a t t h i s
I I time was discharged from the upper portion of the coollng tube out
of the system. In the composition of reaction mass a f t e r
n e u t r a l i z a t i o n , P-mercaptopropionic acid was 87.7 mol%,
thiodipropionic acid which is a by-product was 11.8 mol%, and
10 dithiodipropionic acid was not detected.
Afterthedegassingended, 18.0 gofbutylacetatewasintroduced
thereto, and an extraction operation was performed. 18.0 g of butyl
acetate was f u r t h e r introduced t o the aqueous layer obtained by a
separating, and the same extraction operation was performed three
15 times.
After the butyl a c e t a t e l a y e r s obtained by t h e e x t r a c t i o n of
three times were combined into one, butyl acetate was removed using
anevaporator. The obtainedconcentratedliquidwas ii?Lroducedinto
a k e t t l e of a distillation apparatus with a slngle pipe, and
20 distillation was performed under vacuum of 1 . 2 KPa. D i s t i l l a t i o n
ended when the k e t t l e temperature was increased up t o 150°C. As the
main fraction, 17.8 g (0.168 mol) of P-mercaptoproplonic acldhaving
a purity of 99.9% was obtained. The yield was 83.8% wlth respect
t o a c r y l i c acid.
25 The d i s t i l l a t i o n resldue (A) of 2.7 g had f l u i d i t y even a t 90°C,
and i n the composition, P-mercaptopropionic acid was 16.9% by weight
(0.004 mol), and thiodipropionic acid was 78.9% by weight (0.012
[0079]
(Reaction 2)
An aqueous solution in which 36.3 g (0.88 mol) of 97% sodlum
5 hydroxide and 43.3 g of water, and 0.072 g (0.0022 mol) of sulfur
were uniformly dissolved was prepared in a 5-necked flask provided
with a stirring apparatus, a thermometer, a coollng tube, a dropping
funnel and a blowi~g tube. The distillation residue (A) obtained
in Reaction 1 in a state with fluidity while keeping the temperature
10 at the range of 90°C to 95OC was slowly addedto the aqueous solution.
Whilemaintainingthe inner temperature at the range of 45'Cto 50°C,
12.4 g (0.172mol) ofacrylicacidwas addeddropwise fromthedropping
funnel over 0.5 hours.
After the dropping ended, 12.6 g (0.37 mol) of hydrosulflde gas
15 was blown into the reactlon solution at the same temperature over
90minutes throughthe flowmeter f r o m a l i q u e f ~ e d h y d r o s u l f l d ebo rnbe
(manufactured by Sumitomo Selka Chemicals Co., Ltd.). After the
blowing ended, the temperature was raised to 100°C, and reaction was
performed at the same temperature over 5 hours.
2 0 After the reaction ended, when quantitative analysis of the
reaction solution was performed by a HPLC, 0.174 mol of
P-mercaptopropionic acid sodium salt, and 0.012 mol of
thiodipropionic acid sodium salt and 0.0016molof dithiodipropionic
acid sodium salt as a by-product were produced.
25 Neutralization, extraction and distillation operation were
performed in the same manner as Reaction 1, and 17.8 g (0.168 mol)
of P-mercaptopropionic acid having a purity of 99.9% was obtained
as a main fraction. A cumulative yield of P-mercaptopropionic acid
(0.165 mol + 0.165 mol) obtained in Reactions 1 and 2 was 90.3% with
respect to acrylic acid (14.4 g + 12.4 g) used in Reactions 1 and
2 (one recycling).
5 The distillation residue (B) of 2.8 g had fluidity even at 90°C,
and in the composition, P-mercaptopropionic acid was 16.2% by weight
(0.004mol), andthiodipropionicacidwas 75.8%byweight (0.012mol).
[00801
(Reactions 3 to 6)
10 Hereinafter, in the same manner as Reaction 2, the distillation
residue obtained by distillation is returned to reaction step of the
next reaction to perform a reaction, and Reactions 3 to 6 (four
recycling) were performed.
In the above manner, recycling was performed a total of five
15 times. The used amount of the rawmaterials in Reactions 1 to 6 and
the cumulative yield of P-mercaptopropionic acid are shown in Table
[Table 21
Reactlon Reactlon I Reaction product
No. N~OH ( ~ccryllc ( H,S ( Drst~llatlon( p-mercaptopraplonlc / Corry?asrtlon of 1 dlstlllatlon resrdue mo" 1 1 lmo" residue No. acid I
Production Cumulative No p-mercaptopropionic Thiodipropionic Dithiodipropionic
amount yield * acid acid (mol) acid (mol)
*: (Cumulative production amount (mol) of P-mercaptopropionic acid / cumulative used amount (mol) of
acrylic acid) x 100
[Example 31
In Example 3, Reactions 1 t o 6 are sequentially performed.
Hereinafter, the reactions w i l l be sequentially described.
(Reaction 1)
A 5-necked f l a s k provided with a s t i r r i n g apparatus, a
thermometer, a cooling tube, a dropping funnel and a blowing tube
was prepared, 2 1 . 0 g (0.51 mol) of 97% sodium hydroxide and 41.6 g
of water were introduced thereto, 2 9 . 6 g (0.37 mol) of 70% sodium
10 hydrosulfide (manufactured by Wako Pure Chemical Industries, Ltd.)
was introducedthereto, and t h e r e s u l t a n t was 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
of 45°C t o 50°C by heating the flask i n an o i l bath, 1 4 . 4 g (0.20
15 mol) of a c r y l i c acid was addeddropwise fromthe dropping funnel over
about0.5hours. Afterthedroppingended, thetemperaturewas raised
t o 100°C, and reaction was performed a t the same temperature over
8 hours.
After the reaction ended, when analysis of the reaction mass
20 was performedbyaHPLC, 87.3mol% of P-mercaptopropionic acidsodium
s a l t , 12.0 mol% of thiodipropionic acid sodium s a l t and 0.7 mol% of
dithiodipropionic acid sodium s a l t as a by-product were produced.
After 0.83 g (0.015 mol) of Fe powder was introduced i n t o the
reaction system, whileblowingnitrogen gas thereinto, 129.5 g ( 0 . 4 6 2
25 mol) of 35% aqueous s u l f u r i c acid was added dropwise over 2.5 hours
t o n e u t r a l l z e t h e r e a c t i o n s o l u t i o n . Hydrosulfide g e n e r a t e d a t t h i s
time was discharged from the upper portion of the cooling tube out
o f t h e system. Inaddition, i n t h e compositionof reactionmass a f t e r
neutralization, P-mercaptopropionic acid was 87.6 mol%, and
thiodipropionic acid and dithiodipropionic a c i d which are
by-products were 12.0 mol% and 0.4 mol%, respectively.
5 Afterthedegassingended, 18.0 gofbutylacetatewasintroduced ~ thereto, and an extraction operation was performed. 18.0 g of butyl
acetate was f u r t h e r introduced t o the aqueous layer obtained by a
separating, and the same extraction operation was performed three
times.
10 After the butyl a c e t a t e l a y e r s obtained by the e x t r a c t ~ o no f
i three times were combined into one, butyl acetate was removed using
i
i
i an evaporator. The obtained concentratedliquidwas introducedinto
1 a k e t t l e of a d i s t i l l a t i o n apparatus with a single pipe, and
d i s t i l l a t i o n was performed under vacuum of 1.2 KPa. D i s t i l l a t i o n
15 ended when the k e t t l e temperature was increased up t o 150°C. The
r e s i d u e i n t h e k e t t l e h a d f l u i d i t y e v e n a t 9 0 ° C . As themain f r a c t i o n ,
17.8 g (0.167 mol) of P-mercaptopropionic acid having a purity of
The d i s t i l l a t i o n residue (A) was 2.7, and i n the composition,
20 P-mercaptopropionic acid was 16.2% by weight ( 0 . 0 0 4 mol),
thiodipropionic acid was 80.5% by weight ( 0 . 0 1 2 mol), and
dithiodipropionic acid was 3.0% by weight (0.0004 mol) .
(Reaction 2 )
2 5 After 2 1 . 0 g (0.51 mol) of 97% sodium hydroxide and 4 1 . 6 g of
water were introduced i n a 5-necked flask provided w i ~ ha s t i r r i n g
apparatus, a thermometer, a coollng tube, a dropplng funnel and a
blowing tube, 29.6 g (0.37 mol) of 70% sodium hydrosulfide
(manufacturedbywako Pure Chemical Industries, Ltd.) was introduced
thereto, and the resultant was stirred until it became uniform,
thereby preparing a uniformly dissolved aqueous solution. The
5 distillation residue (A) obtained in Reaction 1 in a state with
fluidlty while keeping the temperature at the range of 90°C to 95OC
was slowlyaddedtothe aqueous solution. W h ~ l e m a i n t a l n i n g t h e i n n e r
t e m p e r a t ~ r e a t t h e r a n g e o f 4 5 ~ C t o 5 O ~1C2.,4 g (0.172mol) of acrylic
acid was added dropwise from the dropping funnel over 0.5 hours.
10 After the dropping ended, 12.6 g (0.37 mol) of hydrosulfide gas
was blown into the reaction solution through the flow meter from a
liquefied hydrosulfide bombe (manufactured by Sumitomo Seika
Chemicals Co., Ltd. ) at the same temperature over 90 minutes. After
the blowing ended, the temperature was raised to 100°C, and reaction
15 was performed at the same temperature over 5 hours.
After the reaction ended, when quantitative analysis of the
reaction solution was performed by a HPLC, 0.175 rnol of
P-mercaptopropionic acid sodium salt, and 0.012 rnol of
thiodipropionic acid sodiumsaltand 0.0011 molof dithiodipropionic
20 acid sodium salt as a by-product were produced.
Neutralization, extraction and distillation operation were
performed in the same manner as Reaction 1, and 17.8 g (0.168 mol)
of P-mercaptopropionic acid having a purity of 99.9% was obtained
as a main fraction. A cumulative yield of P-mercaptopropionic acid
25 (0.167 rnol + 0.168 mol) obtained in Reactions 1 and 2 was 90.1% with
respect to acrylic acid (0.200 rnol + 0.172 mol) used in Reactions
1 and 2 (one recycling).
The distillation residue (B) of 2 .I g had fluidity even at 90°C,
arid in the composition, P-mercaptopropionic acid was 16.2% by welght
(0.004 rnol), thiodlpropionic acid was 80.5% by weight (0.012 mol),
and dithiodipropionic acid was 3.0% by welght (0.0004 rnol),
(Reactions 3 to 6)
Hereinafter, in the same manner as Reaction 2, the distillation
residue obtained by distillation is returned to reaction step of the
next reaction to perform a reaction, and Reactions 3 to 6 (four
recycling) were performed.
In the above manner, recycling was performed a total of five
times. The used amount of the raw materials in Reactions :L to 6 and
the cumulative yield of P-mercaptopropionic acid are shown in Table
3.
[Table 31
*: (Cumulative production amount (mol) of P-mercaptopropionic acid / cumulative used amount (mol) of
, .
acrylic acid) x 100

3 6
neutralization, P-mercaptopropionic acid was 86.2 mol%,
thiodipropionic acid which is a by-product was 13 mol%, and
dithiodipropionic acid was not detected.
Afterthedegassingended, 18.0 gofbutylacetatewasintroduced
thereto, and an extraction operation was performed. 18.0 g of butyl
acetate was further introduced t o the aqueous layer obtained by a
separating, and the same extraction operation was performed three
times.
After the butyl a c e t a t e l a y e r s obtained by the extraction of
three times were combined into one, butyl acetate was removed using
an evaporator. The obtainedconcentratedliquidwas introducedinto
a k e t t l e of a d i s t i l l a t i o n apparatus with a single pipe, and
d i s t i l l a t i o n was performed under vacuum of 1 . 2 KPa. D i s t i l l a t i o n
ended when the k e t t l e temperature was increased up t o 150°C. As the
main f r a c t i o n , 17.6 g ( 0 .I65 mol) af p-mercaptopropionic acid having
a purity of 99.9% was obtained. The yield was 82.5% with respect
t o a c r y l i c acid.
[0087]
[Comparative example 21
A 5-necked f l a s k provided with a s t i r r i n g apparatus, a
thermometer, a cooling tube, a dropping funnel and a blowing tube
was prepared, 21.0 g (0.51 mol) of 97% sodium hydroxide and 4 1 . 6 g
of water were introduced thereto, 29.6 g (0.37 mol) of 70% sodium
hydrosulfide (manufactured by Wako Pure Chemical I n d u s t r i e s , L t d . )
was f u r t h e r introducedthereto, and the r e s u l t a n t was 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
I I of 45°C t o 50°C by heating the flask i n an o i l bath, 1 4 . 4 g (0.20
mol) of a c r y l i c acidwas addeddropwise fromthe dropping funnel over
about0.5hours. Afterthedroppingended, the temperaturewas raised
t o 100°C, and reaction was performed a t the same temperature over
5 8 hours.
After the reaction ended, when analysis of the reaction mass
was performedbyaHPLC, 87.3mol% of P-mercaptopropionicacid sodium
s a l t , 12.0 mol% of thiodipropionic acid sodium s a l t and 0.7 mol% of
dithiodipropionic acid sodium s a l t as a by-product 'were produced.
10 After 0.83 g (0.015 mol) of Fe powder was introduced i n t o the
reactionsystem, whileblowingnitrogengasthereinto, 129.5 g ( 0 . 4 6 2
mol) of 35% aqueous s u l f u r i c acid was added dropwise over 2.5 hours
t o n e u t r a l i z e the r e a c t i o n s o l u t i o n . Hydrosulfide g e n e r a t e d a t t h i s
time was discharged from the upper portion of the cooling tube out
15 of the system. In addition, i n the composition of reaction mass
a f t e r n e u t r a l i z a t i o n , P-mercaptopropionic acid was 87.6 mol%, and
thiodipropionic acid and dithiodipropionic acid which are
by-products were 1 2 . 0 pol% and 0.4 mol%, respectively.
Afterthedegassingended, 18.0 gofbutylacetatewasintroduced
20 thereto, andan extraction operation was performed. 1 8 . 0 g o f b u t y l
acetate was f u r t h e r introduced t o the aqueous layer obtained by a
separating, and the same extraction operation was performed three
times.
After the butyl a c e t a t e l a y e r s obtained by t h e e x t r a c t i o n of
25 three times were comblned i n t o one, butyl acetate was removed using
I
an evaporator. The obtainedconcentratedl~quidwas lntroducedinto
a k e t t l e of a d i s t i l l a t i o n apparatus with a single pipe, and
distillation was performed under vacuum of 1.2 KPa. Distillation
ended when the kettle temperature was increased up to 150°C. The
residue in the kettle had fluidity even at 100°C. As the main
fraction, 17.8 g (0.167 mol) of P-mercaptopropionic acid having a
purity of 99.9% was obtained. The yield was 83.7% with respect to
acrylic acid.
ThepresentapplicationclaimsprioritybasedonJapanese Patent
Applicationno. 2011-253455, filedonNovember 21, 2011, the content
of which is incorporated herein by reference.
CLAIMS
1. A process for preparing p-mercaptocarboxylic acid comprising:
Step a for reacting a compound represented by a formula: X'~S
5 (XI represents hydrogen, Na or K) or a compound represented by a
formula: X'SH (x2 represents Na or K), alkali hydroxide represented
by a formula: X~OH (x3 represents Na or K) , and unsaturated carboxylic
acid represented by the followiny General Formula (1) to obtain a
reaction solution including a compound represented by the following
10 General Formula ( 2 ) and a compound represented by the following
General Formula (3) ;
I
I Step b for neutralizing the reaction solution obtained in Step
a with an acid to obtain a reaction solution including
P-mercaptocarboxylic acid represented by the following General
15 Formula (4) and a compound represented by the following General
Formula (5);
Step c fordistillation-refiningthe reaction solution obtained
in Step b,to obLain the p-mercaptocarboxylic acid represented by
General Formula (4) ; and
20 Step d for returning a distillation residue including the
compound represented by General Formula (5) in Step c to Step a.
or a C1 to C4 alkyl group, and may be the same as or different from
each other,
wherein, i n Formula ( 2 ) , R1 and R2 have the same d e f i n i t i o n as
i n Formula ( I ) , x4 represents Na or K, x4 of which two are present
5 may be the same as or d i f f e r e n t from each other,
1
1 wherein, i n Formula ( 3 ) , R' and R2 have the same d e f i n l t l o n as ~ i n Formula ( I ) , x4 represents Na or K, R', R2 or x4 of which two are
presentrespectivelymaybethe same as o r d l f f e r e n t fromeach other,
wherein, i n Formula ( 4 ) , R1 and R2 have the same d e f i n i t i o n as
In Formula ( I ) , and
wherein, in Formula ( 5 ) , R1 and R2 have the same d e f i n i t i o n as
' 15 i n Formula (I), R' and R2 of which two are present respectively may
be the same as or d i f f e r e n t from each other.
I 2. The process for preparing P-mercaptocarboxylic acld according
I
I to Claim 1,
whereln Steps a to d are repeatedly performed.
I 5
[
j 3. The process for preparing P-mercaptocarboxylic acid according
to Claim 1 or 2,
wherein the compound represented by the formula: X'SH is NaSH.
10 4. The process for preparing P-mercaptocarboxyl~c acid according
to Claim 1 or 2,
wherein the compound represented by the formula: X'ZS is HzS.
5. The process for preparmg P-mercaptocarboxyllc acid according
15 to any one of Claims 1 to 4,
wherein Step a is performed in the presence of sulfur.