JP2003055304A - Method for hydroxyalkyl (meth)acrylate production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for hydroxyalkyl (meth)acrylate production, with which productivity can be increased and generation of impurities such as a diester, a dimmer, etc., as by-products having adverse effects on qualities of product can be controlled while avoiding danger of explosion. SOLUTION: When a time from the starting time of reaction to the completion time of supply of the total amount of an alkylene oxide is T (time), >=50% the whole amount of the alkylene oxide is supplied within the lapse of T/2 (time) from the starting time of the reaction. When the whole amount of the alkylene oxide supplied is W (mol) and the time from the starting time of the reaction to the completion time of supply of the total amount of the alkylene oxide is T (time), the supply of the alkylene oxide is started at a supply velocity V0 (mol/time) higher than an average supply velocity V(=W/T) (mol/time) and thereafter at least once, the supply velocity of the alkylene oxide is reduced and the supply of the whole amount of the alkylene oxide is completed in T (time) after the starting time of the reaction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a hydroxyalkyl (meth) acrylate by reacting (meth) acrylic acid with an alkylene oxide.

[0002]

2. Description of the Related Art In a process for producing a hydroxyalkyl (meth) acrylate by reacting (meth) acrylic acid with an alkylene oxide, generally,
A mode in which (meth) acrylic acid, alkylene oxide and catalyst are charged in a batch in a reaction kettle (collective charging), or a form in which (meth) acrylic acid and catalyst are charged in a reaction kettle in advance and alkylene oxide is charged in a reaction kettle (Sequential input) is adopted.

When a hydroxyalkyl (meth) acrylate is produced by reacting (meth) acrylic acid with an alkylene oxide, a diester (specifically, alkylene glycol di (meth) acrylate) or a by-product is produced. However, since impurities such as dimers (specifically, dialkylene glycol mono (meth) acrylate) are generated, there arises a problem that the reaction selectivity of hydroxyalkyl (meth) acrylate decreases.

The batchwise injection is a preferable mode in that the production of the above impurities is suppressed, so that the reaction selectivity of hydroxyalkyl (meth) acrylate can be increased. However, since alkylene oxide becomes an explosive gas (mixed gas) when certain conditions are satisfied in the coexistence with oxygen, the alkylene oxide concentration in the gas phase in the reaction system at the time of charging the raw material alkylene oxide and at the start of the reaction. However, there is a problem in that there is a high risk of explosion in the case of batch injection in which the temperature becomes high.

[0005] The sequential feeding reduces the above problems and enables the safe production of hydroxyalkyl (meth) acrylate, and at the same time, the formation of the above impurities can be prevented by selecting and controlling an appropriate reaction temperature. This is a preferable form because it can be suppressed.

In the sequential feeding, it has been customary to feed the alkylene oxide at a constant rate. This is because it has been considered that it is easy to control an appropriate reaction temperature for suppressing the by-product of the above impurities, and that the supply at a constant rate is preferable in consideration of the difficulty of handling the alkylene oxide. Is.

In order to increase the productivity in the sequential feeding, it is necessary to increase the alkylene oxide supply rate and shorten the alkylene oxide supply time. It is also desired to shorten the supply time of alkylene oxide in order to suppress the by-product of impurities such as the diester and dimer, which adversely affects the product quality. However,
In the conventional method in which the supply rate is simply increased by a fixed amount and the supply is performed, the residual alkylene oxide concentration becomes high at the end of the supply, which causes a problem of explosion risk.

[0008]

Therefore, the problem to be solved by the present invention is to improve the productivity while avoiding the danger of explosion, and further to diesters and dimers which adversely affect the product quality. Another object of the present invention is to provide a method for producing a hydroxyalkyl (meth) acrylate capable of suppressing by-production of impurities such as.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems. As a result, they have found that the above problem can be solved by changing the supply rate of alkylene oxide so as to meet a specific condition during the supply period.

That is, the method for producing a hydroxyalkyl (meth) acrylate according to the present invention is a method for producing a hydroxyalkyl (meth) acrylate by reacting (meth) acrylic acid with an alkylene oxide in the presence of a catalyst. When the time from the start of the reaction to the end of the supply of the total amount of alkylene oxide is T (hour), from the start of the reaction to the time T / 2 (hour) has elapsed,
It is characterized in that alkylene oxide is supplied in an amount exceeding 50% of the total amount of alkylene oxide.

Another method for producing a hydroxyalkyl (meth) acrylate according to the present invention is a method for producing a hydroxyalkyl (meth) acrylate by reacting (meth) acrylic acid with an alkylene oxide in the presence of a catalyst. In the above, when the total supply amount of alkylene oxide is W (mol) and the time from the start of the reaction to the end of supply of the total amount of alkylene oxide is T (hour),
The alkylene oxide feed is started at a feed rate V0 (mol / hour) higher than the average feed rate V (= W / T) (mol / hour), and then the alkylene oxide feed rate is decreased at least once, The method is characterized in that the supply of the total amount of alkylene oxide is completed within T (hours) from the start of the reaction.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION First, an outline of a process for producing a hydroxyalkyl (meth) acrylate to which the method for producing a hydroxyalkyl (meth) acrylate according to the present invention can be preferably applied will be described.

First, (meth) acrylic acid and alkylene oxide are reacted in the presence of a catalyst. In this reaction, the reaction rate is often less than 100%, and it is common that unreacted (meth) acrylic acid, alkylene oxide, etc. remain in the reaction solution at the end of the reaction. Therefore, the above reaction liquid is guided to a step for removing these unreacted raw materials and the like from the reaction liquid. Then, as the subsequent final step, purification by distillation or the like is performed to obtain the desired hydroxyalkyl (meth) acrylate.

The reaction step of (meth) acrylic acid and alkylene oxide in the presence of a catalyst, which is a feature of the production method according to the present invention, will be described below.

The alkylene oxide which can be used in the present invention is preferably an alkylene oxide having 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms, and examples thereof include ethylene oxide, propylene oxide and butylene oxide. Are ethylene oxide and propylene oxide. The (meth) acrylic acid used in the present invention means acrylic acid or methacrylic acid.

The reaction of (meth) acrylic acid and alkylene oxide in the present invention in the presence of a catalyst can be carried out according to a method generally used for this type of reaction.

For example, when the reaction is carried out in a batch system, the alkylene oxide is fed into the place where the raw material (meth) acrylic acid is charged. At this time, the alkylene oxide is
Turn on sequentially. That is, the (meth) acrylic acid is continuously and / or intermittently charged (hereinafter, may be referred to as “continuous charging” and “intermittent charging”, respectively). Then, as is often done in this type of reaction, the reaction can be completed by so-called aging by continuing the reaction even after the completion of the addition of all the alkylene oxides.

Further, it is not always necessary to charge (meth) acrylic acid all at once in the initial stage, and it is also possible to charge it in several portions.

The above-mentioned sequential charging is a so-called batch charging ((meth) acrylic acid, alkylene oxide,
It means that the catalyst is not charged all at once). "Continuous charging" refers to sequential charging in which the charging is continuously performed little by little, and "intermittent charging" is intermittent charging, for example, charging in two or three times, and the total charging amount is arbitrary. Sequential charging, which is divided into several times.

Further, in the present invention, as the above-mentioned sequential charging, the reaction is started by preliminarily charging a part of the alkylene oxide as an initial charging amount, and then continuously charging the rest with a continuous and / or intermittent charging. The method of doing it can also be mentioned. In this case, the initial amount of the alkylene oxide added is preferably 0.1 to 30% by weight, more preferably 0.5 to 20% by weight, and even more preferably 1 to 10% by weight, based on the total amount of the added alkylene oxide. is there.

In the case where the above-mentioned continuous feeding is carried out, even if the feeding speed is kept constant, the feeding is completed, or even if the feeding is changed at least once in the middle of the feeding, the speed itself is continuously and arbitrarily changed. It is possible to proceed while changing it, and the form of continuous charging is not particularly limited, but among them, the form in which the speed is changed once in the middle and the speed is decreased from before change to after change is more preferable. preferable.

The raw material (meth) acrylic acid and the raw material alkylene oxide may be charged into the reactor through separate charging lines. Before charging into the reactor, a pipe or a line mixer may be used. It may be mixed in advance in a mixing tank or the like and then added. Further, the raw materials may be charged at room temperature or may be heated after reaching a desired reaction temperature in advance. Further, when the reactor outlet liquid is circulated to the reactor inlet, or when unreacted (meth) acrylic acid or unreacted alkylene oxide is recovered and reused, these liquids are used as raw material (meth) acrylic acid, It may be added to the reactor after being mixed with the raw material alkylene oxide. However, when (meth) acrylic acid and alkylene oxide are charged into the reaction solution from separate charging lines,
Since the molar ratio in the reaction solution becomes excess of (meth) acrylic acid in the vicinity of the addition of (meth) acrylic acid, it is preferable to mix the respective raw materials in advance with a pipe or the like before adding to the reactor. Good to do.

The reaction catalyst which can be used in the present invention is not particularly limited, but chromium chloride, acetylacetone chromium, formate, chromium acetate, chromium acrylate, chromium methacrylate, sodium dichromate, chromium dibutyldithiocarbamate. Chromium compounds such as iron compounds; iron compounds such as iron powder, iron chloride, iron formate, iron acetate, iron acrylate, iron methacrylate; trialkylamines, cyclic amines such as pyridine and their quaternary salts, and tertiary amino Group, a quaternary ammonium salt, an amine compound such as a resin having a basic functional group such as a pyridinium group; and the like, and are preferably one or more compounds selected from the group.

The amount of the above catalyst is not particularly limited, but in the case of a homogeneous catalyst, it is 0.0 with respect to the raw material (meth) acrylic acid.
It is preferably used in the range of 5 to 10% by weight, more preferably 0.1 to 3% by weight. Further, in the case of a homogeneous catalyst, it is generally charged in a reaction vessel in advance, but there is no particular limitation, and the reaction is carried out after the raw material (meth) acrylic acid is dissolved in a dissolution tank separate from the reaction vessel. It can also be placed in a kettle. On the other hand, in the case of batch reaction with a heterogeneous catalyst, it is preferably used in the range of 5 to 80% by weight, more preferably 10% by weight, based on the raw material (meth) acrylic acid.
Used in the range of up to 70% by weight.

If desired, a polymerization inhibitor may be added to the reaction solution. The polymerization inhibitor is not particularly limited, and any one generally used in industry can be used. Specifically, for example, hydroquinone, methylhydroquinone, tert-butylhydroquinone, 2,
Phenol compounds such as 6-di-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2,4-dimethyl-6-tert-butylphenol and hydroquinone monomethyl ether; 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, N, N'-
Para-phenylenediamines such as di-2-naphthyl-para-phenylenediamine; amine compounds such as thiodiphenylamine and phenothiazine; copper dialkyldithiocarbamate salts such as copper dibutyldithiocarbamate, copper diethyldithiocarbamate, copper dimethyldithiocarbamate; 2,4,4-tetramethylazetidine-1-oxyl, 2,2-dimethyl-4,4-dipropylazetidine-1-oxyl, 2,2,5,5-tetramethylpyrrolidine-1-oxyl, 2,2,5,5-tetramethyl-3-oxopyrrolidine-1-oxyl, 2,2
6,6-Tetramethylpiperidine-1-oxyl, 4-
Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 6-aza-7,7-dimethyl-spiro (4,5) decane-6-oxyl, 2,2,6,6-tetramethyl Examples thereof include N-oxyl compounds such as -4-acetoxypiperidine-1-oxyl and 2,2,6,6-tetramethyl-4-benzoyloxypiperidine-1-oxyl. These polymerization inhibitors may be used alone or in combination of two or more.

The amount of the above-mentioned polymerization inhibitor added depends on the raw material (meta).
The amount is preferably 0.0001 to 1% by weight, more preferably 0.001 to 0.5% by weight, based on acrylic acid.

Hydroxyalkyl (meth) according to the present invention
In the method for producing an acrylate, alkylene oxide is sequentially charged, that is, continuously charged and / or intermittently charged to react with (meth) acrylic acid.

Supply amount of alkylene oxide (total supply amount)
Is in the range of preferably 1.0 to 10 moles of alkylene oxide, more preferably 1.0 to 5.0 moles, still more preferably 1.0 to 1 mole of (meth) acrylic acid. 3.0 mol, even more preferably 1.
It is 0 to 2.0 mol. When the amount of alkylene oxide supplied is less than the equimolar amount with respect to (meth) acrylic acid, the reaction does not proceed and the characteristic method of the present invention cannot be carried out, which is not preferable. . Also,
When the supply amount of alkylene oxide exceeds 10 mol, a recovery step is required and it is economically disadvantageous.

The production method according to the present invention is characterized in that the supply rate of the alkylene oxide is varied during the supply period so as to meet a specific condition.

One of the above specific conditions is that the time from the start of the reaction to the end of the supply of the total amount of alkylene oxide is T
T / 2 (hour) from the start of the reaction
By the time elapsed, the amount of alkylene oxide is more than 50% of the total amount of alkylene oxide.

It is preferable to supply alkylene oxide in an amount of more than 50% and not more than 95% of the total amount of alkylene oxide from the start of the reaction to the elapse of T / 2 (hours), and more preferably 60 to. It is 90%, even more preferably 65 to 85%, and particularly preferably 70 to 80%.

The time T (hour) from the start of the reaction to the end of the supply of the total amount of the alkylene oxide varies depending on various reaction conditions, but is preferably 3 to 6 hours.

By supplying the alkylene oxide so as to satisfy this specific condition, a larger amount of the alkylene oxide is supplied in the first half of the reaction than in the latter half. By this supply form, the alkylene oxide supply time can be shortened and productivity is improved as compared with the conventional case where the alkylene oxide is supplied at a constant rate. Furthermore, by-products such as diesters and dimers that adversely affect product quality can be suppressed. In addition, the reaction rate becomes higher than that in the case where the conventional alkylene oxide is supplied at a constant rate, and the residual alkylene oxide concentration at the end of the supply can be suppressed low, so that the problem of explosion risk can be avoided.

Another one of the above specific conditions is the average when the total amount of alkylene oxide supplied is W (mol) and the time from the start of the reaction to the end of the total amount of alkylene oxide is T (hour). The feed of alkylene oxide is started at a feed rate V0 (mole / hour) higher than the feed rate V (= W / T) (mole / hour), and then at least 1
That is, the supply rate of the alkylene oxide is reduced to complete the supply of the total amount of the alkylene oxide at T (time) from the start of the reaction.

The time T (hour) from the start of the reaction to the end of the supply of the total amount of the alkylene oxide varies depending on various reaction conditions, but is preferably 3 to 6 hours.

Feeding rate V of the above alkylene oxide
0 (mol / hour) means the above average supply rate V (= W / T)
It is preferably 1.1 times or more of (mol / hour),
It is more preferably 1.3 times or more, even more preferably 1.7 times or more, and particularly preferably 2.0 times or more.

Under the above specific conditions, the alkylene oxide supply rate is reduced at least once after the start of the alkylene oxide supply so that the T
The supply of the total amount of alkylene oxide is completed in (time). The operation of decreasing the supply rate may be any number of times as long as it is once or more, and may be decreased stepwise, steplessly (continuously), or a combination thereof. It is sufficient that the supply of the total amount of alkylene oxide can be completed within T (hours) from the start of the reaction.

By supplying alkylene oxide so as to satisfy this specific condition, a larger amount of alkylene oxide is supplied in the first half of the reaction than in the latter half. By this supply form, the alkylene oxide supply time can be shortened and productivity is improved as compared with the conventional case where the alkylene oxide is supplied at a constant rate. Furthermore, by-products such as diesters and dimers that adversely affect product quality can be suppressed. In addition, the reaction rate becomes higher than that in the case where the conventional alkylene oxide is supplied at a constant rate, and the residual alkylene oxide concentration at the end of the supply can be suppressed low, so that the problem of explosion risk can be avoided.

The means for evaluating the risk of explosion is not particularly limited, but for example, a method of evaluating from the composition of the gas phase in the reaction system at the end of the alkylene oxide supply, more specifically, the alkylene oxide concentration and oxygen concentration There is a method to evaluate from. The risk of explosion, which is usually evaluated from the alkylene oxide concentration and the oxygen concentration, depends on environmental conditions such as the temperature, pressure and space volume inside the reaction system. For example, when the reaction is performed under general environmental conditions, if the oxygen concentration is 3 to 4% by volume, the alkylene oxide concentration is less than 25% by volume, preferably less than 20% by volume, more preferably 15% by volume. If it is less than%, the risk of explosion can be avoided.

Hydroxyalkyl (meth) according to the present invention
In the method for producing acrylate, the reaction temperature of (meth) acrylic acid and alkylene oxide is 40 to 100 ° C.
Is more preferable, the range of 45-90 ° C is more preferable, the range of 45-80 ° C is even more preferable, and 50-
The range of 80 ° C. is particularly preferred.

When the temperature range is lower than 40 ° C., the reaction rate is remarkably reduced, the gas concentration of unreacted alkylene oxide in the gas phase becomes high, and there is a risk of explosion, so that safety is ensured. First, it is necessary to dilute the gas phase portion with an inert gas to reduce the gas concentration of alkylene oxide in the gas phase. In that case, it is necessary to increase the design pressure of the reactor, which is not economically preferable. There is also a method of slowing the rate of introducing alkylene oxide to reduce the concentration of unreacted alkylene oxide, but the reaction time becomes long and the productivity decreases.

If the temperature range exceeds 100 ° C., it is difficult to suppress the formation of diester or dialkylene glycol mono (meth) acrylate, which is not preferable.

In the present invention, the formation of the diester, which is a substance that promotes the polymerization of the target product, hydroxyalkyl (meth) acrylate, is suppressed more than usual, so that the polymerization of hydroxyalkyl (meth) acrylate during the reaction is suppressed. It can be suppressed, and the blockage due to polymerization in the reaction vessel and the pipe can be eliminated, and the productivity can be further improved.

In the production method of the present invention, the diester production inhibitor may be added in two or more portions in the reaction and distillation, or in the production steps including the reaction, aging and distillation. As the generation inhibitor, oxalic acid, oxalic anhydride, malonic acid, succinic acid, succinic anhydride, fumaric acid, maleic acid, maleic anhydride, salicylic acid, octanoic acid, adipic acid, sepacic acid, tetradecanedicarboxylic acid, 1, 2,4-butanetricarboxylic acid, 1,3,6
-Hexanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-pentanetetracarboxylic acid, 1,6,7,12-dodecanetetracarboxylic acid, benzoic acid, orthotoluic acid, Metatoluic acid, paratoluic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid,
Pyromellitic acid, pyromellitic anhydride, trimellitic acid, trimellitic anhydride, 1,2,4-benzenetricarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 1,3,5,7-naphthalene Carboxylic acids such as tetracarboxylic acid and polyacrylic acid and anhydrides thereof; glycerin, diethylene glycol, trimethylolpropane, cresol, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, 2,
3,4,5-tetrahydroxyhexane, xylitol, mannitol, catechol, resorcin, 2,6-
Dihydroxytoluene, tert-butylcatechol,
Pyrogallol, 2,4-bis (hydroxymethyl) phenol, 1,2,4-trihydroxybenzene, 1,
Polyhydric alcohols such as 3,5-trihydroxybenzene, 2,4,6-tris (hydroxymethyl) phenol, 1,2,4,5-tetrahydroxybenzene; ethylenediaminetetraacetic acid, ethylenediaminetetrapropionic acid, nitrilotriacetic acid , Iminodiacetic acid, 1,2-diaminocyclohexanetetraacetic acid, acetylacetone, cuperone, oxine, benzidine, metal chelating agents such as diethyldithiocarbamic acid; and the like, which may be one or more compounds selected from the group preferable.

In the production method of the present invention, the reaction may be carried out in a solvent for the purpose of allowing the reaction to proceed mildly. As the solvent, toluene, xylene,
Common ones such as heptane and octane can be used.

In the production method according to the present invention, the pressure in the system at the time of reaction is generally under pressure, although it depends on the kind and mixing ratio of the raw materials used.

[0047]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to the following examples.

-Example 1-658 g of acrylic acid, chromium acetate 2.62 as a catalyst
g, and 1.44 g of hydroquinone monomethyl ether as a polymerization inhibitor were charged into a SUS-316 autoclave equipped with a stirrer and having a capacity of 1.5 liter, and the internal temperature was raised to 50 ° C. Was replaced with oxygen, and the oxygen concentration was 4% by volume and the internal pressure was 0.1 MPa.

Then, after feeding 287 g of ethylene oxide into the above autoclave over 60 minutes, the feeding rate was changed and 143 g was fed over 120 minutes. During this time, the reaction temperature was maintained at 50 ° C.

The composition of the reaction solution at the end of the ethylene oxide supply was 19.5% by weight of acrylic acid and 1 part of ethylene oxide.
It was 2.3% by weight, the ethylene oxide concentration in the gas phase part of the autoclave at that time was 23% by volume, and the oxygen concentration was 3.5% by volume.

After the completion of the ethylene oxide supply, the temperature was raised to 70 ° C. and the reaction was continued until the unreacted acrylic acid became 0.1% by weight or less. By continuing the reaction for 3 hours, unreacted acrylic acid became 0.09% by weight, so the reaction solution was cooled. The hydroxyethyl acrylate concentration in the obtained reaction liquid was 91.4 wt%, the diester concentration was 0.18 wt%, and the diethylene glycol monoacrylate concentration was 7.4 wt%.

Comparative Example 1 The same operation as in Example 1 was carried out except that 430 g of ethylene oxide was fed at a constant rate over 240 minutes.

The composition of the reaction solution at the end of the ethylene oxide supply was 20.3% by weight of acrylic acid and 1 part of ethylene oxide.
3.9% by weight, the concentration of ethylene oxide in the gas phase of the autoclave at that time was 25% by volume, and the concentration of oxygen was 3.
It was 5% by volume, which was outside the explosion range as in Example 1.

After the ethylene oxide supply was completed, the temperature was raised to 70 ° C. to continue the reaction, and the reaction was continued for 3.5 hours. As a result, unreacted acrylic acid became 0.09% by weight.
The reaction solution was cooled. In the obtained reaction solution, the concentration of hydroxyethyl acrylate was 90.2% by weight, the concentration of diester was 0.24% by weight, and the concentration of diethylene glycol monoacrylate was 8.2% by weight. The ethylene oxide concentration in the gas phase of the autoclave at the end was almost the same as in Example 1, and there was no danger of explosion. However, compared with Example 1, the production amount of by-products such as diester and diethylene glycol monoacrylate was increased, and the reaction time was increased by 1.5 hours, resulting in a decrease in productivity.

Comparative Example 2 The same operation as in Example 1 was carried out except that 430 g of ethylene oxide was fed at a constant rate over 180 minutes.

The composition of the reaction solution at the end of the ethylene oxide supply was 25.3% by weight of acrylic acid and 1 part of ethylene oxide.
The content was 6.5% by weight, the concentration of ethylene oxide in the gas phase of the autoclave was 30% by volume, and the concentration of oxygen was 3.
It was 5% by volume, and with this gas composition, it entered the explosion range, and there was a risk of explosion. Therefore, the reaction was continued after confirming that the ignition source was not near.

After the supply of ethylene oxide was completed, the temperature was raised to 70 ° C. to continue the reaction, and by continuing the reaction for 3 hours,
Since the unreacted acrylic acid became 0.08% by weight, the reaction solution was cooled. The hydroxyethyl acrylate concentration in the obtained reaction liquid was 91.2% by weight, the diester concentration was 0.20% by weight, and the diethylene glycol monoacrylate concentration was 7.5% by weight.

In Comparative Example 2, the production amount of the by-product diester or diethylene glycol monoacrylate was almost the same as that in Example 1, but the ethylene oxide concentration in the gas phase of the autoclave at the end of the ethylene oxide supply was higher than that in Example 1. Higher and increased risk of explosion.

Example 2 746 g of methacrylic acid and chromium acetate 2.62 as a catalyst
and phenothiazine as a polymerization inhibitor 2.24
g, SUS-316 with a stirrer having a capacity of 1.5 liters
After charging into an autoclave manufactured by the company and raising the internal temperature to 60 ° C, the inside was replaced with nitrogen gas and the oxygen concentration was adjusted to 4
The volume% and the internal pressure were 0.1 MPa.

Then, 272 g of ethylene oxide was fed into the autoclave over 90 minutes, and then the feed rate was changed, and 117 g of ethylene oxide was fed over 60 minutes. During this time, the reaction temperature was maintained at 60 ° C.

The composition of the reaction solution at the end of the ethylene oxide supply was 26.8% by weight of methacrylic acid and 1 part of ethylene oxide.
2.8% by weight, the concentration of ethylene oxide in the gas phase of the autoclave at that time was 24% by volume, and the concentration of oxygen was 3.
It was 8% by volume.

After the supply of ethylene oxide was completed, the temperature was raised to 75 ° C. and the reaction was continued until the unreacted methacrylic acid became 0.1% by weight or less. By continuing the reaction for 3 hours,
Since the unreacted methacrylic acid became 0.09% by weight, the reaction liquid was cooled. In the obtained reaction liquid, the hydroxyethyl methacrylate concentration was 95.7% by weight, the diester concentration was 0.06% by weight, and the diethylene glycol monomethacrylate concentration was 3.5% by weight.

Comparative Example 3 The same operation as in Example 2 was performed, except that 58 g of ethylene oxide was supplied over 38 minutes, the supply rate was changed, and 331 g was supplied over 112 minutes.

The composition of the reaction solution at the end of the ethylene oxide supply was 32.2% by weight of methacrylic acid and 1 part of ethylene oxide.
The content was 5.1% by weight, the ethylene oxide concentration in the gas phase of the autoclave was 28% by volume, and the oxygen concentration was 3.
It was 8% by volume, and with this gas composition, it entered the explosion range, and there was a danger of explosion. Therefore, the reaction was continued after confirming that the ignition source was not near.

After the supply of ethylene oxide was completed, the temperature was raised to 75 ° C. to continue the reaction, and by continuing the reaction for 3.5 hours, unreacted methacrylic acid became 0.08% by weight. Cooled. The concentration of hydroxyethyl methacrylate in the obtained reaction solution was 94.6% by weight,
The diester concentration was 0.15% by weight and the diethylene glycol monomethacrylate concentration was 4.0% by weight, and the amount of by-products produced was larger than in Example 2.

In Comparative Example 3, the ethylene oxide concentration in the gas phase of the autoclave at the end of the ethylene oxide supply was higher than that in Example 2, and the risk of explosion increased. Moreover,
Compared with Example 2, the amount of by-products such as diester and diethylene glycol monomethacrylate increased, and the aging time after the end of the ethylene oxide supply increased by 0.5 hours, resulting in a decrease in productivity.

Example 3 663 g of acrylic acid and chromium acetate 3.32 as a catalyst
g, and 1.03 g of hydroquinone monomethyl ether as a polymerization inhibitor were charged into an autoclave made of SUS-316 with a stirrer having a capacity of 1.5 liter, and 55 g of propylene oxide was placed in the autoclave using a plunger pump. I put it in. Then, the internal temperature is raised to 55 ° C., and the inside is replaced with nitrogen gas during the heating period, the oxygen concentration is 3.5% by volume, and the internal pressure is 0.1 MPa.
a.

When the reaction temperature reached 55 ° C., propylene oxide was started to be charged, and after 330 g was supplied over 90 minutes, the supply rate was changed and 202 g was supplied over 150 minutes. During this time, the reaction temperature was maintained at 55 ° C.

The composition of the reaction liquid at the end of the propylene oxide supply was 20.2% by weight of acrylic acid and 15.4% by weight of propylene oxide. At that time, the concentration of propylene oxide in the gas phase of the autoclave was 15% by volume, and the oxygen concentration was Was 3.2% by volume.

After the supply of propylene oxide was completed, the reaction temperature was raised to 70 ° C. and the reaction was continued until the unreacted acrylic acid became 0.1% by weight or less. By continuing the reaction for 2.5 hours, unreacted acrylic acid became 0.09% by weight, so the reaction solution was cooled. The obtained reaction solution had a hydroxypropyl acrylate concentration of 94.3% by weight, a diester concentration of 0.15% by weight, and a dipropylene glycol monoacrylate concentration of 4.2% by weight.

-Comparative Example 4-As Example 3 except that propylene oxide was charged after the reaction temperature reached 55 ° C and not after the reaction temperature reached 55 ° C, and was maintained for another hour. The same operation was performed.

The composition of the reaction solution at the end of the propylene oxide supply was 18.5% by weight of acrylic acid and 13.7% by weight of propylene oxide. At that time, the propylene oxide concentration in the gas phase of the autoclave was 14% by volume and the oxygen concentration was Was 3.3% by volume.

After the supply of propylene oxide was completed, the reaction temperature was raised to 70 ° C. and the reaction was continued for 3 hours,
Since the unreacted acrylic acid became 0.09% by weight, the reaction liquid was cooled. The obtained reaction liquid had a hydroxypropyl acrylate concentration of 91.6% by weight, a diester concentration of 0.27% by weight, and a dipropylene glycol monoacrylate concentration of 7.6% by weight.

In Comparative Example 4, the propylene oxide concentration in the gas phase of the autoclave at the end of the propylene oxide supply was almost the same as in Example 3, and there was no danger of explosion. However, compared with Example 3, the production amount of by-products such as diester and dipropylene glycol monoacrylate increased, and the reaction time became longer as the reaction was allowed to proceed, resulting in lower productivity.

[0075]

According to the present invention, the alkylene oxide supply time can be shortened and the productivity is improved. Furthermore, by-products such as diesters and dimers that adversely affect product quality can be suppressed. In addition, the residual alkylene oxide concentration at the end of the supply can be suppressed to a low level as compared with the conventional case where the alkylene oxide is supplied at a constant rate, and the problem of explosion risk can be avoided.

Continued front page    (72) Inventor Yukihiro Yoneda             Hyogo prefecture Himeji city             1 Within Nippon Shokubai Co., Ltd. F-term (reference) 4H006 AA02 AC48 BA14 BA19 BA37                       BA51 BD21 BN10 KA19                 4H039 CA66 CF90

Claims (2)

[Claims] 1. A method for producing a hydroxyalkyl (meth) acrylate by reacting (meth) acrylic acid with an alkylene oxide in the presence of a catalyst, wherein the time from the start of the reaction to the end of the supply of the total amount of the alkylene oxide is If T (time) is set, T
A method for producing a hydroxyalkyl (meth) acrylate, which comprises supplying alkylene oxide in an amount exceeding 50% of the total amount of alkylene oxide by the time // 2 (hours) has elapsed. 2. A method for producing a hydroxyalkyl (meth) acrylate by reacting (meth) acrylic acid with an alkylene oxide in the presence of a catalyst, wherein the total amount of alkylene oxide supplied is W (mol), at the start of the reaction. When the time from the end of the supply of the total amount of alkylene oxide to T is defined as T (hour), the average supply rate V (= W /
T) (mol / hour) V0 (mol / hour)
Time)), the alkylene oxide supply is started at least once, and then the supply rate of the alkylene oxide is reduced at least once, and the supply of the total amount of alkylene oxide is ended at T (time) from the start of the reaction. Method for producing hydroxyalkyl (meth) acrylate.