U.S. patent application number 09/779205 was filed with the patent office on 2001-09-27 for production process for hydroxyalkyl (meth)acrylate.
This patent application is currently assigned to Nippon Shokubai Co., Ltd. Invention is credited to Asami, Masakazu, Nakahara, Sei, Shingai, Yasuhiro, Ueoka, Masatoshi, Yoneda, Yukihiro.
Application Number | 20010025120 09/779205 |
Document ID | / |
Family ID | 18588398 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010025120 |
Kind Code |
A1 |
Shingai, Yasuhiro ; et
al. |
September 27, 2001 |
Production process for hydroxyalkyl (meth)acrylate
Abstract
The present invention provides a production process for a
hydroxyalkyl (meth)acrylate which process enables to maintain the
oxygen concentration of a gas phase portion of a reactor within a
specific low concentration range in any stage of before adding raw
materials, during the reaction, and after the reaction. The
production process comprises the step of carrying out a reaction
between (meth)acrylic acid and an alkylene oxide in the presence of
a catalyst in order to produce the hydroxyalkyl (meth)acrylate,
wherein an inert gas and/or a mixed gas of oxygen and an inert gas
with a beforehand adjusted oxygen concentration of 0.1 to 14 vol %
is used to maintain the oxygen concentration of a gas phase portion
of a reactor in the range of 0.1 to 14 vol % (1) before adding the
alkylene oxide or (2) during the above reaction or (3) between the
completion of the above reaction and the charge for the next
reaction. In addition, another production process comprises the
step of carrying out a reaction between (meth)acrylic acid and an
alkylene oxide in the presence of a catalyst in order to produce
the hydroxyalkyl (meth)acrylate, wherein the oxygen concentration
of a gas phase portion of a reactor is maintained in the range of
0.1 to 14 vol % throughout the production steps.
Inventors: |
Shingai, Yasuhiro;
(Himeji-shi, JP) ; Nakahara, Sei; (Himeji-shi,
JP) ; Yoneda, Yukihiro; (Himeji-shi, JP) ;
Asami, Masakazu; (Himeji-shi, JP) ; Ueoka,
Masatoshi; (Himeji-shi, JP) |
Correspondence
Address: |
Robert J. Jacobson, P.A.
650 Brimhall Street South
St. Paul
MN
55116-1511
US
|
Assignee: |
Nippon Shokubai Co., Ltd
|
Family ID: |
18588398 |
Appl. No.: |
09/779205 |
Filed: |
February 8, 2001 |
Current U.S.
Class: |
560/209 |
Current CPC
Class: |
C07C 67/26 20130101;
C07C 67/26 20130101; C07C 69/54 20130101 |
Class at
Publication: |
560/209 |
International
Class: |
C07C 067/26 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 13, 2000 |
JP |
2000-69541 |
Claims
What is claimed is:
1. A production process for a hydroxyalkyl (meth)acrylate, which
comprises the step of carrying out a reaction between (meth)acrylic
acid and an alkylene oxide in the presence of a catalyst in order
to produce said hydroxyalkyl (meth)acrylate, wherein an inert gas
and/or a mixed gas of oxygen and an inert gas with a beforehand
adjusted oxygen concentration of 0.1 to 14 vol % is used to
maintain the oxygen concentration of a gas phase portion of a
reactor in the range of 0.1 to 14 vol % before adding said alkylene
oxide.
2. A production process for a hydroxyalkyl (meth)acrylate, which
comprises the step of carrying out a reaction between (meth)acrylic
acid and an alkylene oxide in the presence of a catalyst in order
to produce said hydroxyalkyl (meth)acrylate, wherein an inert gas
and/or a mixed gas of oxygen and an inert gas with a beforehand
adjusted oxygen concentration of 0.1 to 14 vol % is used to
maintain the oxygen concentration of a gas phase portion of a
reactor in the range of 0.1 to 14 vol % during said reaction.
3. A production process for a hydroxyalkyl (meth)acrylate, which
comprises the step of carrying out a reaction between (meth)acrylic
acid and an alkylene oxide in the presence of a catalyst in order
to produce said hydroxyalkyl (meth)acrylate, wherein an inert gas
and/or a mixed gas of oxygen and an inert gas with a beforehand
adjusted oxygen concentration of 0.1 to 14 vol % is used to
maintain the oxygen concentration of a gas phase portion of a
reactor in the range of 0.1 to 14 vol % between completion of said
reaction and charge for the next reaction.
4. A production process according to claim 3, which further
comprises the step of, after said completion of the reaction,
discharging the resultant reaction liquid under pressure while said
maintenance of the oxygen concentration of the gas phase portion of
the reactor is carried out.
5. A production process for a hydroxyalkyl (meth)acrylate, which
comprises the step of carrying out a reaction between (meth)acrylic
acid and an alkylene oxide in the presence of a catalyst in order
to produce said hydroxyalkyl (meth)acrylate, wherein the oxygen
concentration of a gas phase portion of a reactor is maintained in
the range of 0.1 to 14 vol % throughout the production steps.
6. A production process according to claim 5, wherein the oxygen
concentration is maintained in the range of 0.1 to 14 vol % not
only in said gas phase portion of the reactor, but also in a gas
phase portion in the step of separating an unreacted residue of the
alkylene oxide from the resultant reaction product.
7. A production process according to claim 1, wherein the catalyst
is at least one member selected from the group consisting of iron
compounds, chromium compounds, and amine compounds.
8. A production process according to claim 2, wherein the catalyst
is at least one member selected from the group consisting of iron
compounds, chromium compounds, and amine compounds.
9. A production process according to claim 3, wherein the catalyst
is at least one member selected from the group consisting of iron
compounds, chromium compounds, and amine compounds.
10. A production process according to claim 4, wherein the catalyst
is at least one member selected from the group consisting of iron
compounds, chromium compounds, and amine compounds.
11. A production process according to claim 5, wherein the catalyst
is at least one member selected from the group consisting of iron
compounds, chromium compounds, and amine compounds.
12. A production process according to claim 6, wherein the catalyst
is at least one member selected from the group consisting of iron
compounds, chromium compounds, and amine compounds.
Description
BACKGROUND OF THE INVENTION
[0001] A. Technical Field
[0002] The present invention relates to a production process for a
hydroxyalkyl (meth)acrylate which comprises the step of carrying
out a reaction between (meth)acrylic acid and an alkylene
oxide.
[0003] B. Background Art
[0004] An alkylene oxide forms an explosive mixed gas under certain
conditions in the presence of oxygen. Therefore, when a
hydroxyalkyl (meth)acrylate is produced by carrying out a reaction
between (meth)acrylic acid and the alkylene oxide, it is desirable
that this production is carried out under an atmosphere in which
oxygen does not exist in consideration of safety. On the other
hand, however, raw materials or products polymerize under an
atmosphere in which oxygen does not exist at all. Therefore, it is
proposed to carry out the production under an atmosphere of a gas
which contains oxygen as a polymerization inhibitor.
[0005] However, when the production is carried out under an
atmosphere of a mixed gas which contains oxygen in a comparatively
high concentration such as air, there is a particularly high
possibility that an explosive mixed gas might be formed when adding
the alkylene oxide into a reactor, therefore such production is
very dangerous.
[0006] In addition, when the production is carried out under an
atmosphere of a mixed gas which contains oxygen in a comparatively
low concentration, an inert gas (e.g. nitrogen) (which is a sealing
gas (e.g. a pressured or replaced sealing gas for such as a raw
material storage tank)) or oxygen is dissolved in the raw materials
such as the (meth)acrylic acid and the alkylene oxide, therefore,
every time these raw materials are added, the oxygen concentration
of a gas phase portion of the reactor varies and, if the oxygen
concentration becomes high, there occurs a danger of explosion and,
if the oxygen concentration lowers near 0 vol %, there occurs a
possibility of polymerization. In addition, there is a case where
the oxygen concentration of the gas phase portion of the reactor
varies also in the progress of the reaction.
SUMMARY OF THE INVENTION
[0007] A. Object of the Invention
[0008] An object of the present invention is to provide a
production process for a hydroxyalkyl (meth)acrylate wherein, when
a reaction between (meth)acrylic acid and an alkylene oxide is
carried out to produce the hydroxyalkyl (meth)acrylate, the process
enables to maintain the oxygen concentration of a gas phase portion
of a reactor within a specific low concentration range in any stage
of before adding raw materials, during the reaction, and after the
reaction.
[0009] B. Disclosure of the Invention
[0010] The present inventors diligently studied to solve the
above-mentioned problems. As a result, the inventors have hit on an
idea that, if a mixed gas, having an oxygen concentration as
beforehand adjusted into a specific low concentration range, and/or
an inert gas is used to make a concentration adjustment to maintain
the oxygen concentration of a gas phase portion of a reactor within
a specific low concentration range before adding raw materials,
during the reaction, or after the reaction, then the
above-mentioned problems can be solved. The present invention has
been completed in this way.
[0011] That is to say, a production process for a hydroxyalkyl
(meth)acrylate, according to the present invention, comprises the
step of carrying out a reaction between (meth)acrylic acid and an
alkylene oxide in the presence of a catalyst in order to produce
the hydroxyalkyl (meth)acrylate, wherein an inert gas and/or a
mixed gas of oxygen and an inert gas with a beforehand adjusted
oxygen concentration of 0.1 to 14 vol % is used to maintain the
oxygen concentration of a gas phase portion of a reactor in the
range of 0.1 to 14 vol % before adding the alkylene oxide.
[0012] In addition, another production process for a hydroxyalkyl
(meth)acrylate, according to the present invention, comprises the
step of carrying out a reaction between (meth)acrylic acid and an
alkylene oxide in the presence of a catalyst in order to produce
the hydroxyalkyl (meth)acrylate, wherein an inert gas and/or a
mixed gas of oxygen and an inert gas with a beforehand adjusted
oxygen concentration of 0.1 to 14 vol % is used to maintain the
oxygen concentration of a gas phase portion of a reactor in the
range of 0.1 to 14 vol % during the above reaction.
[0013] In addition, yet another production process for a
hydroxyalkyl (meth)acrylate, according to the present invention,
comprises the step of carrying out a reaction between (meth)acrylic
acid and an alkylene oxide in the presence of a catalyst in order
to produce the hydroxyalkyl (meth)acrylate, wherein an inert gas
and/or a mixed gas of oxygen and an inert gas with a beforehand
adjusted oxygen concentration of 0.1 to 14 vol % is used to
maintain the oxygen concentration of a gas phase portion of a
reactor in the range of 0.1 to 14 vol % between completion of the
above reaction and charge for the next reaction.
[0014] In addition, yet another production process for a
hydroxyalkyl (meth)acrylate, according to the present invention,
comprises the step of carrying out a reaction between (meth)acrylic
acid and an alkylene oxide in the presence of a catalyst in order
to produce the hydroxyalkyl (meth)acrylate, wherein the oxygen
concentration of a gas phase portion of a reactor is maintained in
the range of 0.1 to 14 vol % throughout the production steps.
[0015] These and other objects and the advantages of the present
invention will be more fully apparent from the following detailed
disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0016] First, the production process for a hydroxyalkyl
(meth)acrylate to which the characteristic production process
according to the present invention is preferably applicable is
roughly explained as follows.
[0017] First, a reaction between (meth)acrylic acid and an alkylene
oxide is carried out in the presence of a catalyst. The conversion
in this reaction is often less than 100%, therefore generally such
as an unreacted residue of the (meth)acrylic acid or alkylene oxide
is present in the resultant reaction liquid at the end of the
reaction. Thus, the above resultant reaction liquid is led to the
step to remove such as these unreacted residues of the raw
materials from the reaction liquid, and then purified by such as
distillation as the subsequent final step, with the result that the
aimed hydroxyalkyl (meth)acrylate is obtained.
[0018] The production process according to the present invention
involves controlling the atmosphere of the gas phase portion of the
reactor in the above-mentioned series of production steps.
[0019] The alkylene oxide, usable in the present invention,
preferably has 2 to 6 carbon atoms, more preferably 2 to 4 carbon
atoms. Examples thereof include ethylene oxide, propylene oxide,
and butylene oxide. Among them, ethylene oxide or propylene oxide
is preferable. In addition, the (meth)acrylic acid, as used in the
present invention, means acrylic acid or methacrylic acid.
[0020] The catalyst, usable for the reaction in the present
invention, is not especially limited, but preferable examples
thereof include at least one member selected from the group
consisting of: chromium compounds such as chromium chloride,
chromium acetylacetonate, chromium formate, chromium acrylate,
chromium methacrylate, sodium dichromate, and chromium
dibutyldithiocarbamate; iron compounds such as iron powder, iron
chloride, iron formate, iron acrylate, and iron methacrylate; and
amine compounds such as trialkylamines, cyclic amines (e.g.
pyridine) and their quaternary salts, and resins having a basic
functional group (e.g. tertiary amino groups, quaternary ammonium
salts, and pyridinium groups).
[0021] The amount of the above catalyst is not especially limited,
but, in the case where the catalyst is a homogeneous catalyst, the
catalyst is usually used in the range of 0.05 to 10 weight %,
particularly preferably 0.1 to 3 weight %, of the raw (meth)acrylic
acid. In addition, in the case where the catalyst is a
heterogeneous catalyst, the catalyst is usually used in the range
of 5 to 50 weight %, particularly preferably 10 to 30 weight %, of
the raw (meth)acrylic acid.
[0022] In addition, polymerization inhibitors may be added to the
reaction liquid if necessary. Examples thereof include: phenol
compounds such as hydroquinone, methylhydroquinone,
tert-butylhydroquinone, 2,6-di-tertbutylhydroquinone,
2,5-di-tert-butylhydroquinone, 2,4-dimethyl-6-tertbutylphenol, and
hydroquinone monomethyl ether; paraphenylenediamines such as
N-isopropyl-N'-phenyl-para-phenylenediamine- ,
N-(1,3-dimethylbutyl)-N'-phenyl-para-phenylenediamine,
N-(1-methylheptyl)-N'-phenyl-para-phenylenediamine,
N,N'-diphenyl-para-phenylenediamine, and
N,N'-di-2-naphthyl-para-phenylen- ediamine; amine compounds such as
thiodiphenylamine and phenothiazine; copper dialkyldithiocarbamates
such as copper dibutyldithiocarbamate, copper
diethyldithiocarbamate, and copper dimethyldithiocarbamate; nitroso
compounds such as nitrosodiphenylamine, isoamyl nitrite,
N-nitrosocyclohexylhydroxylamine,
N-nitroso-N-phenyl-N-hydroxylamine, and their salts; and N-oxyl
compounds such as 2,2,4,4-tetramethylazetidine-1-- oxyl,
2,2-dimethyl-4,4-dipropylazetidine-1-oxyl,
2,2,5,5-tetramethylpyrrol- idine-1-oxyl,
2,2,5,5-tetramethyl-3-oxopyrrolidine-1-oxyl,
2,2,6,6-tetramethylpiperidine-1-oxyl,
4-hydroxy-2,2,6,6-tetramethylpiperi- dine-1-oxyl,
6-aza-7,7-dimethyl-spiro(4,5)decane-6-oxyl,
2,2,6,6-tetramethyl-4-acetoxypiperidine-1-oxyl, and
2,2,6,6-tetramethyl-4-benzoyloxypiperidine-1-oxyl.
[0023] When the present invention is carried out, the amount of raw
materials as charged for the above reaction between the
(meth)acrylic acid and the alkylene oxide is such that the alkylene
oxide is preferably in the range of 1.0 to 5.0 mols, more
preferably in the range of 1.0 to 3.0 mols, still more preferably
in the range of 1.0 to 2.0 mols, per 1 mol of the (meth)acrylic
acid. In the case where the amount of the alkylene oxide as charged
is smaller than 1.0 mol, there are disadvantages in that the
conversion is so low as to increase the by-products. In addition,
in the case where the amount of the alkylene oxide as charged is
larger than 5 mols, there are economical disadvantages.
[0024] In the present invention, the reaction between the
(meth)acrylic acid and the alkylene oxide in the presence of the
catalyst can be carried out by methods which are used
conventionally for this kind of reaction. For example, in the case
where the reaction is carried out in a batch manner, the reaction
is carried out by introducing the alkylene oxide into the
(meth)acrylic acid. The (meth)acrylic acid may be dissolved into a
solvent, and then the alkylene oxide may be introduced into the
resultant solution. In this batch manner, the alkylene oxide may be
added all at once, or continuously or intermittently. And in the
case where the alkylene oxide is added continuously or
intermittently, it is permissible that, as is often the case with
this kind of reaction, the reaction is continued still after the
end of the introduction of the alkylene oxide, in other words,
aging is carried out, thereby completing the reaction. In addition,
the (meth)acrylic acid does not need to be charged all at once in
the initial stage, either, but can be added after being divided
into some portions. In addition, in the case where the reaction is
carried out in a continuous manner, the reaction is carried out by
continuously adding the (meth)acrylic acid and the alkylene oxide
into a reactor such as tubular or tank reactor and continuously
extracting the resultant reaction liquid from the reactor. In this
continuous manner, the catalyst may continuously be supplied
together with raw materials and then continuously be extracted
together with the resultant reaction liquid and, in the case of a
reactor such as tubular reactor, a solid catalyst may be used in a
state filled in the reactor, in other words, in what is called a
fixed bed manner. In addition, in the case of the tank reactor, a
solid catalyst may be used in a state fluidized together with the
reaction liquid in the reactor, in other words, in what is called a
fluidized bed manner. In the cases of these continuous reactions, a
part of the reaction liquid may be circulated. The reaction
temperature is usually in the range of preferably 40 to 130.degree.
C., more preferably 50 to 100.degree. C. In the case where the
reaction temperature is lower than 40.degree. C., there are
disadvantages in that the reaction rate is so slow as to be apart
from a practical use level. On the other hand, in the case where
the reaction temperature is higher than 130.degree. C., there are
disadvantages in that a large amount of by-products are formed, or
in that, because the raw (meth)acrylic acid has an unsaturated
double bond, such as polymerization of this (meth)acrylic acid or
its product hydroxyalkyl (meth)acrylate occurs. In addition, the
reaction may be carried out in a solvent for the purpose of, for
example, mildly running the reaction. As to the solvent,
conventional ones such as toluene, xylene, heptane, and octane are
usable. The inside pressure of the reaction system during the
reaction depends on the kinds or mixing ratios of the raw
materials, but is generally higher than atmospheric pressure.
[0025] In the production process, according to the present
invention, an inert gas and/or a mixed gas of oxygen and an inert
gas with a beforehand adjusted oxygen concentration of 0.1 to 14
vol % is used to maintain the oxygen concentration of a gas phase
portion of a reactor in the range of 0.1 to 14 vol % (1) before
adding the alkylene oxide or (2) during the above reaction or (3)
between the completion of the above reaction and the charge for the
next reaction. Hereinafter, these characteristics are explained in
detail.
[0026] As is aforementioned, the alkylene oxide forms an explosive
mixed gas under certain conditions in the presence of oxygen. On
the other hand, however, raw materials or products polymerize under
an atmosphere in which oxygen does not exist at all. Therefore, it
is desirable to carry out the production under an atmosphere of a
gas which contains oxygen as a polymerization inhibitor.
[0027] However, when the production is carried out under an
atmosphere of a mixed gas which contains oxygen in a comparatively
high concentration such as air, there is a particularly high
possibility that an explosive mixed gas might be formed when adding
the alkylene oxide into a reactor, therefore such production is
very dangerous.
[0028] Thus, the present inventors studied what oxygen
concentration range enables to prevent the formation of the
explosive mixed gas and further the polymerization. As a result,
the inventors have found that, if the oxygen concentration of the
gas phase portion of the reactor can be maintained in the range of
0.1 to 14 vol %, then the above-mentioned object can be achieved.
The above oxygen concentration is preferably in the range of 0.3 to
12 vol %, more preferably 0.5 to 8 vol %.
[0029] On the other hand, an inert gas (e.g. nitrogen) (which is a
sealing gas (e.g. a pressured or replaced sealing gas for such as a
raw material storage tank)) or oxygen is dissolved in the raw
materials such as the (meth)acrylic acid and the alkylene oxide.
Therefore, every time these raw materials are added, the oxygen
concentration of a gas phase portion of the reactor varies and, if
the oxygen concentration becomes high, there occurs a danger of
explosion and, if the oxygen concentration lowers near 0 vol %,
there occurs a possibility of polymerization. In addition, there is
a case where the oxygen concentration of the gas phase portion of
the reactor varies also in the progress of the reaction.
[0030] Therefore, a method is necessary by which method the
preferable oxygen concentration range of 0.1 to 14 vol % can be
maintained even if the variation of the oxygen concentration is
caused by such as the above-mentioned factors. The present
inventors studied and, as a result, have found that the oxygen
concentration of the gas phase portion of the reactor can be
maintained in the range of 0.1 to 14 vol % by using the inert gas
and/or the mixed gas of oxygen and the inert gas with a beforehand
adjusted oxygen concentration of 0.1 to 14 vol % and adding these
gases correspondingly to the variation of the oxygen concentration
of the gas phase portion of the reactor in order to adjust this
oxygen concentration.
[0031] Namely, before the alkylene oxide is added, the raw
(meth)acrylic acid is beforehand charged into the reactor, but
there can occur a case where, even if the oxygen concentration of
the gas phase portion of the reactor is adjusted in the range of
0.1 to 14 vol % before the charge of the (meth)acrylic acid, the
oxygen concentration of the gas phase portion of the reactor varies
due to the charge of the (meth)acrylic acid, because the
aforementioned sealing gas is dissolved in the (meth)acrylic acid.
Thus, the inert gas and/or the mixed gas of oxygen and the inert
gas with a beforehand adjusted oxygen concentration of 0.1 to 14
vol % is added into the gas phase portion of the reactor
correspondingly to the variation of the oxygen concentration of the
gas phase portion of the reactor in order to adjust this oxygen
concentration. Specifically, for example, when the oxygen
concentration of the gas phase portion of the reactor increases,
the inert gas is added in order to decrease this oxygen
concentration, or otherwise, when the oxygen concentration of the
gas phase portion of the reactor decreases, the mixed gas of oxygen
and the inert gas with a beforehand adjusted oxygen concentration
of 0.1 to 14 vol % is added in order to increase this oxygen
concentration, thus maintaining the oxygen concentration of the gas
phase portion of the reactor in the range of 0.1 to 14 vol %.
Furthermore, for example, when the inert gas has excessively been
added for the oxygen concentration adjustment, there is also a case
where the oxygen concentration of the gas phase portion of the
reactor is adjusted in the range of 0.1 to 14 vol % again by adding
the mixed gas of oxygen and the inert gas with a beforehand
adjusted oxygen concentration of 0.1 to 14 vol %.
[0032] Furthermore, during the reaction after adding the alkylene
oxide, there can occur a case where, even if the oxygen
concentration of the gas phase portion of the reactor is adjusted
in the range of 0.1 to 14 vol % before the addition of the alkylene
oxide, the oxygen concentration of the gas phase portion of the
reactor varies due to the addition of the alkylene oxide, because
the aforementioned sealing gas is dissolved also in the added
alkylene oxide. Furthermore, in the case of using the iron powder
which is effective for the present reaction (JP-B-038534/1977), the
iron powder grows oxidized into divalent or trivalent iron ion
during the reaction, when oxygen in the reactor is consumed. Hence,
there can occur a case where the oxygen concentration of the gas
phase portion of the reactor varies due to such a factor as well.
Thus, the inert gas and/or the mixed gas of oxygen and the inert
gas with a beforehand adjusted oxygen concentration of 0.1 to 14
vol % is added into the gas phase portion of the reactor
correspondingly to the variation of the oxygen concentration of the
gas phase portion of the reactor in order to adjust this oxygen
concentration. Specifically, similarly to the aforementioned, for
example, when the oxygen concentration of the gas phase portion of
the reactor increases, the inert gas is added in order to decrease
this oxygen concentration, or otherwise, when the oxygen
concentration of the gas phase portion of the reactor decreases,
the mixed gas of oxygen and the inert gas with a beforehand
adjusted oxygen concentration of 0.1 to 14 vol % is added in order
to increase this oxygen concentration, thus maintaining the oxygen
concentration of the gas phase portion of the reactor in the range
of 0.1 to 14 vol %. Furthermore, for example, when the inert gas
has excessively been added for the oxygen concentration adjustment,
there is also a case where the oxygen concentration of the gas
phase portion of the reactor is adjusted in the range of 0.1 to 14
vol % again by adding the mixed gas of oxygen and the inert gas
with a beforehand adjusted oxygen concentration of 0.1 to 14 vol
%.
[0033] In addition, similarly also in the case where the reaction
is continuously carried out, the oxygen concentration of the gas
phase portion of the reactor varies due to factors such as
influence of the sealing gas which is dissolved in the alkylene
oxide and the (meth)acrylic acid that are continuously supplied
into the reactor. Therefore, the production process according to
the present invention is useful similarly to the above.
[0034] The reaction liquid is discharged from the reactor after the
end of the reaction, but the internal pressure of the reactor falls
then, so there can occur necessity to inject a gas from the outside
in order to prevent this internal pressure falling. In addition,
there is also a case where, when the reaction liquid is discharged
from the reactor, the reaction liquid is discharged by the gas
injection from the outside all along. In these operations, the
oxygen concentration of the gas phase portion of the reactor can
vary during the gas injection from the outside. In addition, if the
oxygen concentration of the gas which is injected from the outside
is high, there is a very great danger that an explosive gas might
be formed in the case where the alkylene oxide remains in the
reactor. Thus, the oxygen concentration of the gas phase portion of
the reactor is maintained in the range of 0.1 to 14 vol % using the
inert gas and/or the mixed gas of oxygen and the inert gas with a
beforehand adjusted oxygen concentration of 0.1 to 14 vol % as the
gas which is used when the above-mentioned operations are carried
out. Furthermore, if, also between the discharge of the reaction
liquid and the charge for the next reaction, the inert gas and/or
the mixed gas of oxygen and the inert gas with a beforehand
adjusted oxygen concentration of 0.1 to 14 vol % is used to carry
out the adjustment to maintain the oxygen concentration of the gas
phase portion of the reactor in the range of 0.1 to 14 vol %, then
there are advantages of enabling to retain the reactor in a safe
state where there is only a low possibility that the alkylene oxide
remaining in the reactor might mix with oxygen to form an explosive
mixed gas, and where there occurs no polymerization of the residual
reaction liquid (which exists in such as valve and nozzle portions)
in the reactor.
[0035] As to specific methods for controlling the oxygen
concentration of the gas phase portion of the reactor, the inert
gas and/or the mixed gas of oxygen and the inert gas may be added
either continuously or intermittently. In addition, these gases may
be added into the gas phase portion of the reactor, or may be added
into the reaction liquid. In either case, for example, a plate for
dispersion may be placed in order to improve the gas
dispersibility.
[0036] In addition, there is a case where the inside pressure of
the reactor rises due to the addition of these gases. In such a
case, the gases may intermittently be purged, or may continuously
be purged if the gases are continuously added.
[0037] The inside pressure of the reactor is preferably in the
range of 0.1 to 1 MPa, more preferably 0.1 to 0.7 MPa. In the case
where the inside pressure of the reactor is lower than 0.1 MPa, it
is difficult for the alkylene oxide to exist in a liquid state
under reaction temperature conditions, so the reaction rate is
slow. In addition, in the case where the inside pressure of the
reactor is higher than 1 MPa, there are economical disadvantages of
needing a high pressure-resistant reactor.
[0038] In addition, the alkylene oxide which is contained in gases
as purged from the reactor, including the above purged gases, may
be disposed of by being absorbed into such as water. However, there
are economical advantages if the alkylene oxide is recycled after
being recovered by: leading the alkylene oxide to alkylene oxide
recovery facilities and then condensing the alkylene oxide with a
condenser; or getting the alkylene oxide absorbed into a liquid
such as a polar solvent (e.g. water), the raw (meth)acrylic acid,
and the resultant hydroxyalkyl (meth)acrylate. Especially, it is
preferable that the alkylene oxide is recycled after being
recovered by getting the alkylene oxide absorbed into the raw
(meth)acrylic acid, the resultant hydroxyalkyl (meth)acrylate, or
their liquid mixture.
[0039] As is mentioned above, the production process according the
invention enables to maintain the oxygen concentration of the gas
phase portion of the reactor in the range of 0.1 to 14 vol % (1)
before adding the alkylene oxide or (2) during the reaction or (3)
between the completion of the reaction and the charge for the next
reaction. This production process may be applied according to the
production step that involves a large variation of the oxygen
concentration of the gas phase portion of the reactor. Namely, for
example, in the case where the variation of the oxygen
concentration of the gas phase portion of the reactor because of
the charge of the raw (meth)acrylic acid is large, a production
process according to the present invention may be applied in which
production process an inert gas and/or a mixed gas of oxygen and an
inert gas with a beforehand adjusted oxygen concentration of 0.1 to
14 vol % is used to maintain the oxygen concentration of a gas
phase portion of a reactor in the range of 0.1 to 14 vol % before
adding the alkylene oxide. In the case where the variation of the
oxygen concentration of the gas phase portion of the reactor
because of the addition of the alkylene oxide is large, another
production process according to the present invention may be
applied in which production process an inert gas and/or a mixed gas
of oxygen and an inert gas with a beforehand adjusted oxygen
concentration of 0.1 to 14 vol % is used to maintain the oxygen
concentration of a gas phase portion of a reactor in the range of
0.1 to 14 vol % during the reaction. In the case where the
variation of the oxygen concentration of the gas phase portion of
the reactor in the step of discharging the resultant reaction
product is large, another production process according to the
present invention may be applied in which production process an
inert gas and/or a mixed gas of oxygen and an inert gas with a
beforehand adjusted oxygen concentration of 0.1 to 14 vol % is used
to maintain the oxygen concentration of a gas phase portion of a
reactor in the range of 0.1 to 14 vol % between the completion of
the reaction and the charge for the next reaction.
[0040] Furthermore, as to the production process according to the
present invention for the hydroxyalkyl (meth)acrylate, it can be
said to be a preferred mode that the oxygen concentration of the
gas phase portion of the reactor is maintained in the range of 0.1
to 14 vol % throughout the production steps. The reason therefor is
that, if such a low oxygen concentration can be maintained
throughout the production steps, then safe and stable production
can be actualized.
[0041] In addition, the production process for the hydroxyalkyl
(meth)acrylate generally comprises a reaction step, a separation
step for an unreacted residue of the alkylene oxide, a separation
step for an unreacted residue of the (meth)acrylic acid, and a
distillation step for the reaction product, wherein the separation
step for an unreacted residue of the (meth)acrylic acid might be
omitted if the conversion of the (meth)acrylic acid in the reaction
is near 100%.
[0042] The above separation step for an unreacted residue of the
alkylene oxide, for example, means a step in which: the unreacted
residue of the alkylene oxide is separated and removed from the
resultant reaction liquid by utilizing such as an inert gas with a
packing column, and then the alkylene oxide included in the
resultant gas is absorbed into a solvent such as water, whereby the
unreacted residue of the alkylene oxide is disposed of or recovered
for recycling.
[0043] The above separation step for an unreacted residue of the
(meth)acrylic acid, for example, means a step in which: the
unreacted residue of the (meth)acrylic acid is separated and
removed from the resultant reaction liquid by distillation with an
apparatus, and then the resultant vapor of the (meth)acrylic acid
is condensed with such as a condenser or absorbed into a solvent
such as water, whereby the unreacted residue of the (meth)acrylic
acid is disposed of or recovered for recycling.
[0044] The above distillation step for the reaction product, for
example, means a step in which: the reaction product is distilled
by distillation with an apparatus and then condensed with such as a
condenser, whereby a product is obtained.
[0045] Then, as to the production process according to the present
invention for the hydroxyalkyl (meth)acrylate, it is a more
preferred mode that the oxygen concentration is maintained in the
range of 0.1 to 14 vol % not only in the gas phase portion of the
reactor, but also in a gas phase portion in the step of separating
an unreacted residue of the alkylene oxide from the resultant
reaction product, namely, as to the aforementioned example, as
follows: a gas phase portion in the packing column; a gas phase
portion such as a vapor line through which a gas led from the
packing column is passed till being absorbed into a solvent such as
water; and a gas phase portion of an intermediate tank such as a
feed tank which is appended to the packing column.
[0046] A still more preferred mode is that the oxygen concentration
is maintained in the range of 0.1 to 14 vol % also in a gas phase
portion in the step of separating an unreacted residue of the
(meth)acrylic acid from the resultant reaction product, namely, as
to the aforementioned example, as follows: a gas phase portion in
the apparatus; a gas phase portion such as a vapor line through
which a vapor led from the apparatus is passed till being condensed
with such as a condenser or absorbed into a solvent such as water;
and a gas phase portion of an intermediate tank such as a feed tank
and a distillate tank which are appended to the apparatus; and/or
in a gas phase portion in the distillation step for the reaction
product, namely, as to the aforementioned example, as follows: a
gas phase portion in the apparatus; a gas phase portion such as a
vapor line through which a vapor led from the apparatus is passed
till being condensed with such as a condenser; and a gas phase
portion of an intermediate tank such as a feed tank and a
distillate tank which are appended to the apparatus.
[0047] Herein, equipments which are used in the separation step for
the unreacted residue of the alkylene oxide or (meth)acrylic acid
and the distillation step for the reaction product are not
especially limited, but examples thereof include packing columns,
plate columns, bubble cap tray columns, and apparatuses.
[0048] If the oxygen concentration of the above gas phase portions
in the step of separating the unreacted residue of the alkylene
oxide from the resultant reaction product, other than the gas phase
portion of the reactor, is also maintained in the range of 0.1 to
14 vol %, then there is only a low possibility that a gas in such
gas phase portions might mix with the alkylene oxide to form an
explosive mixed gas, and further, no polymer forms in the
separation step for the unreacted residues of the raw materials and
the distillation step for the reaction product, therefore safely
the hydroxyalkyl (meth)acrylate can be produced.
[0049] Incidentally, in the case where a gas having a high oxygen
concentration (e.g. air) is used as an oxygen source instead of the
inert gas and/or the mixed gas of oxygen and the inert gas with a
beforehand adjusted oxygen concentration of 0.1 to 14 vol % which
are used in the present invention, there is a high possibility that
an explosive gas having a high oxygen concentration might be formed
locally, for example, near an air injection nozzle, even if the
oxygen concentration of the entirety of the gas phase portion of
the reactor is within the range of 0.1 to 14 vol % as defined in
the present invention.
[0050] (Effects and Advantages of the Invention):
[0051] When a reaction between (meth)acrylic acid and an alkylene
oxide is carried out to produce a hydroxyalkyl (meth)acrylate, the
process according to the present invention enables to maintain the
oxygen concentration of a gas phase portion of a reactor within a
specific low concentration range in any stage of before adding raw
materials, during the reaction, and after the reaction.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0052] Hereinafter, the present invention is more specifically
illustrated by the following examples of some preferred embodiments
in comparison with comparative examples not according to the
invention. However, the present invention is not limited to the
below-mentioned examples of some preferred embodiments.
Incidentally, hereinafter, unless otherwise noted, the unit "%" of
the oxygen and nitrogen concentrations is "vol %".
EXAMPLE 1
[0053] The inside gas of an autoclave of 2 liters in capacity, as
equipped with a thermometer, a heating and cooling unit, and a
stirrer, was replaced with a mixed gas which had been adjusted so
as to have an oxygen concentration of 3% and a nitrogen
concentration of 97%. Then, 844 g of acrylic acid was charged from
a vessel (containing raw acrylic acid and having been sealed in an
oxygen concentration of 7% and a nitrogen concentration of 93%)
through piping (as fitted to the autoclave) into the autoclave by
use of a feed pump, and then 2 g of phenothiazine, 5 g of
hydroquinone monomethyl ether (both as polymerization inhibitors),
and 5 g of chromium acetate (as a catalyst) were added into the
autoclave. At this time, the oxygen concentration of a gas phase
portion of the autoclave was 5% under the influence of oxygen as
dissolved in the raw acrylic acid. Next, the inside liquid
temperature of the autoclave was raised to 70.degree. C. which was
a reaction temperature. Thereafter, the oxygen concentration in the
autoclave was adjusted to 3.5% with nitrogen gas. In addition, the
inside pressure of the autoclave was adjusted to 0.03 MPa. Then,
620 g of ethylene oxide was supplied from a high pressure-resistant
vessel (containing the ethylene oxide and having been sealed at 0.5
MPa with a gas having a nitrogen concentration of 100%) through
piping (as fitted to the autoclave) into the inside liquid of the
autoclave at almost a constant rate by use of a feed pump over a
period of about 4 hours, while the reaction was carried out with
the temperature maintained at 70.degree. C. After the supply of the
ethylene oxide had ended, the oxygen concentration of the gas phase
portion of the autoclave lowered to 2.0% under the influence of
nitrogen as dissolved in the raw ethylene oxide and the influence
of an unreacted gas of the alkylene oxide. Thereafter, the reaction
was continued for 3 hours with the temperature maintained at
70.degree. C. At this time, the oxygen concentration of the gas
phase portion of the autoclave was 2.5% because the amount of the
unreacted gas of the alkylene oxide decreased in comparison with
what it had been after the supply end of the raw ethylene oxide.
Hereupon, the resultant reaction liquid was analyzed, so that the
acrylic acid concentration was 0.05 wt %. Therefore, the autoclave
was cooled at once, and then the reaction liquid was discharged by
utilizing the residual inside pressure of the autoclave. On its
way, a mixed gas which had been adjusted so as to have an oxygen
concentration of 3% and a nitrogen concentration of 97% was fitly
injected so that the residual inside pressure of the reactor might
not be 0.1 MPa or lower.
[0054] After the above discharge of the reaction liquid had ended,
the inside gas of the autoclave was purged to replace it with a
mixed gas which had been adjusted so as to have an oxygen
concentration of 3% and a nitrogen concentration of 97%.
Hereinafter, the same reaction operation as the above was repeated
30 times, while no polymer was observed in the discharged reaction
liquid. In addition, after these 30-time repeats of the reaction
operation had ended, the autoclave was opened to inspect the inside
of the autoclave. However, no polymer formation was observed.
EXAMPLE 2
[0055] The inside gas of an autoclave of 1 liter in capacity, as
equipped with a thermometer, a heating and cooling unit, and a
stirrer, was replaced with a mixed gas which had been adjusted so
as to have an oxygen concentration of 4.5% and a nitrogen
concentration of 95.5%. Then, a mixture of which the total amount
was 600 ml was prepared by charging this autoclave with 400 ml of a
water-humidified basic anion-exchange resin (DIAION PA316 produced
by Mitsubishi Chemical Corporation) (as a catalyst) and with
acrylic acid by supplying it from a vessel (containing raw acrylic
acid (in which phenothiazine and hydroquinone monomethyl ether were
dissolved in the ratios of 0.2 wt % and 0.5 wt % respectively as
polymerization inhibitors) and having been sealed in an oxygen
concentration of 7% and a nitrogen concentration of 93%) through
piping (as fitted to the autoclave) into the autoclave by use of a
feed pump. At this time, the oxygen concentration of a gas phase
portion of the autoclave was 6% under the influence of oxygen as
dissolved in the raw acrylic acid. Next, the inside liquid
temperature of the autoclave was raised to 70.degree. C. which was
a reaction temperature. Thereafter, the oxygen concentration in the
autoclave was adjusted to 4% with nitrogen gas. In addition, the
inside pressure of the autoclave was adjusted to 0.03 MPa. Then,
the above acrylic acid in which the polymerization inhibitors were
dissolved was continuously supplied into the autoclave at a rate of
109 g/h, and further, ethylene oxide was continuously supplied from
a high pressure-resistant vessel (containing the ethylene oxide and
having been sealed at 0.5 MPa with a gas having a nitrogen
concentration of 100%) through piping (as fitted to the autoclave)
into the inside liquid of the autoclave at a rate of 101 g/h by use
of a feed pump. The resultant reaction liquid was continuously
discharged such that the liquid level in the autoclave could be
fixed during the reaction. After 60 hours, the oxygen concentration
of the gas phase portion of the autoclave lowered to 1.3% under the
influence of nitrogen as dissolved in the raw ethylene oxide and
the influence of an unreacted gas of the alkylene oxide. Therefore,
the oxygen concentration of the gas phase portion of the autoclave
was changed to 3% with a mixed gas which had been adjusted so as to
have an oxygen concentration of 4.5% and a nitrogen concentration
of 95.5%. Still thereafter, the oxygen concentration of the gas
phase portion of the autoclave was monitored and adjusted with the
mixed gas (which had been adjusted so as to have an oxygen
concentration of 4.5% and a nitrogen concentration of 95.5%) in
order that the oxygen concentration might not be 0.1% or lower. On
the other hand, the inside gas of the autoclave was fitly purged so
that the inside pressure of the autoclave could be in the range of
0.1 to 1 MPa. The reaction was continuously carried out for 200
hours in this state, while no polymer was however observed in the
discharged reaction liquid. In addition, the reaction liquid was
cooled, and then the autoclave was opened to inspect the inside of
the autoclave. However, no polymer formation was observed.
[0056] In addition, the reaction liquid as obtained in a stationary
state was analyzed by gas chromatography, so that the conversion of
the acrylic acid was 86%.
COMPARATIVE EXAMPLE 1
[0057] The reaction was carried out in the same way as of Example 1
except that, before the supply of the ethylene oxide, the gas phase
portion of the autoclave was adjusted so as to have a nitrogen
concentration of 100% (oxygen concentration=0%) instead of being
adjusted so as to have an oxygen concentration of 3.5%. After the
supply of the ethylene oxide had been completed, the reaction
liquid was sampled, so that a fine polymer was observed in the
reaction liquid. Therefore, the reaction was discontinued, and then
the reaction liquid was cooled. Thereafter, the inside of the
autoclave was inspected, so that a filmy polymer was observed in
the gas phase portion of the autoclave, and that a small amount of
fine polymer particles were observed in the reaction liquid as
well.
COMPARATIVE EXAMPLE 2
[0058] The reaction was carried out in the same way as of Example 1
except that the inside gas of the autoclave was replaced with a gas
having a nitrogen concentration of 100% (oxygen concentration=0%)
after the discharge of the reaction liquid had ended. When the
20th-time reaction operation had ended, the inside of the autoclave
was inspected, so that a polymer was observed in gas phase portions
of the autoclave, particularly, thermometer protector tubes, nozzle
portions of such as pressure gauges.
COMPARATIVE EXAMPLE 3
[0059] An attempt was made to carry out the reaction in the same
way as of Example 1 except that the oxygen concentration of the gas
phase portion of the autoclave was adjusted by supplying nitrogen
and air separately from each other instead of using the mixed gas
which had been adjusted so as to have an oxygen concentration of 3%
and a nitrogen concentration of 97%. However, when air was supplied
following nitrogen, the oxygen concentration near a nozzle for
supplying this air was measured to show 16%, so there was a danger
of explosion. Thus, the reaction was discontinued.
COMPARATIVE EXAMPLE 4
[0060] The reaction was carried out in the same way as of Example 2
except that the oxygen concentration in the autoclave was changed
to 1% after heating the acrylic acid to 70.degree. C. After 150
hours from the end of the continuous addition of the acrylic acid
and the ethylene oxide, the oxygen concentration of the gas phase
portion of the autoclave was measured. The result showed a
concentration reduction to 0.05%, so the reaction was discontinued
at once. The reaction liquid was cooled, and then the autoclave was
opened to inspect the inside of the autoclave. As a result,
attachment of a polymer to the gas phase portion of the autoclave
was seen.
[0061] Various details of the invention may be changed without
departing from its spirit not its scope. Furthermore, the foregoing
description of the preferred embodiments according to the present
invention is provided for the purpose of illustration only, and not
for the purpose of limiting the invention as defined by the
appended claims and their equivalents.
* * * * *