JPH07126214A - Production of 4-hydroxybutyl acrylate - Google Patents

Abstract

PURPOSE:To produce 4-hydroxybutyl acrylate industrially and advantageously by selectively extracting and separating a diester compound in a high yield from an esterification mixture of acrylic acid and 1,4-butane diol and lowering a solution volume to be treated in a process. CONSTITUTION:Acrylic acid is reacted with 1-2 molar 1,4-butane diol based on acrylic acid in the presence of a catalyst and a hydrocarbon solvent under refluxing of the hydrocarbon solvent while removing generated water by distillation. To the obtained reaction mixture, 0.4-2.5wt. times water extracting agent based on the wt. of the reaction mixture except the hydrocarbon solvent and 2-20wt. times hydrocarbon extracting agent (including the one in the reaction mixture) are added to form two liquid phases consisting of an extracting liquid phase mainly containing diester component and a water extracting liquid phase mainly containing monoester component and unreacted diol, and then 4- hydroxybutyl acrylate is recovered from the residual water extracting liquid phase.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing 4-hydroxybutyl acrylate. More specifically, it relates to an improvement in a method for producing 4-hydroxybutyl acrylate by subjecting acrylic acid and 1,4-butanediol to an esterification reaction.

[0002]

2. Description of the Related Art 4-Hydroxybutyl acrylate is
Since it has a double bond and a hydroxyl group in the molecule, it can be copolymerized with other vinyl monomers, and because it can undergo a cross-linking reaction using a hydroxyl group and a reaction to introduce another functional group, it is more thermosetting than before. It is used in a wide range of applications as a water-based paint, adhesive, or modifier for various resins.

As a method for producing 4-hydroxybutyl acrylate, an esterification reaction of acrylic acid and 1,4-butanediol or a transesterification reaction of a lower alkyl acrylate and 1,4-butanediol is carried out. Although a method is known, the former method is generally used because it is easy to separate and remove water generated by the reaction. However, in the above esterification reaction method, when acrylic acid and 1,4-butanediol (hereinafter, also simply referred to as “diol”) are reacted in the presence of an acidic catalyst, the chemical formula (I 4-hydroxybutyl acrylate (hereinafter also referred to as "monoester body") represented by the formula (1) is produced, but at the same time, 1,4-butanediol diacrylate represented by the chemical formula (II) (hereinafter also referred to as "diester body"). It is a by-product.

[0004]

[Chemical 1]

[0005]

[Chemical 2]

The by-product of the diester in the esterification reaction can be considerably suppressed by increasing the charged amount (molar ratio) of 1,4-butanediol to acrylic acid, but the by-product of the diester is obtained. You cannot avoid life itself. Further, in this case, a large amount of unreacted diol is present in the reaction mixture after the completion of the reaction, resulting in low production efficiency, separation of by-product diester from the reaction mixture, and separation and recovery of unreacted diol. A new problem arises in that the reuse requires a complicated process and a large cost.

As described above, in the method for producing 4-hydroxybutyl acrylate by esterifying acrylic acid and 1,4-butanediol, the diester and the diol are separated from the reaction mixture after the esterification reaction. These separation methods, because it is essential to
In particular, there has been a long-felt demand for the development of a method for separating diesters which is industrially advantageous.

As a method for separating the monoester form and the diester form, distillation separation, extraction separation, and the like can be considered. However, both the monoester form and the diester form have a relatively high boiling point, and since they are highly polymerizable, they are separated by distillation. The method according to (1) is not practical, and as described in West German Patent No. 1518572, the method based on extraction and separation is general. The method described in this German patent publication adds a large amount of water to the reaction mixture after the esterification reaction, which is 5 times as much as that of the reaction mixture, and then cyclohexane is used as an extractant to extract and separate the diester form into this extract liquid phase. This is a method of extracting the target monoester (and diol) as an aqueous phase. This method not only requires a large amount of treatment liquid in the extraction step, but also in the step of recovering the monoester from the aqueous phase. Since a large amount of water must be handled, the device becomes large and its operation requires a great deal of cost, it is industrially extremely disadvantageous.

[0009]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned conventional technical problems, in a reaction mixture obtained by esterifying acrylic acid and 1,4-butanediol. It is intended to provide an industrially advantageous method for producing 4-hydroxybutyl acrylate, which can selectively extract and separate the diester form (by-product) of (3) and has a small amount of liquid to be treated in the process. It is what

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that when a diester is extracted from a reaction mixture obtained by the esterification reaction, The above object can be easily achieved by adjusting the amount of the water extractant and the amount of the hydrocarbon extractant to be mixed to the respective specific ranges, particularly, the amount of the water extractant to be small in the range which has not been considered at all. The inventors have found this and completed the present invention.

However, the gist of the present invention is as follows.
Acrylic acid and 1-2 mole times of acrylic acid
In the presence of an acidic catalyst and a hydrocarbon solvent, butanediol is distilled off the water formed by the esterification reaction, and the reaction is carried out under the reflux of the hydrocarbon solvent to obtain a reaction mixture. The reaction mixture obtained in the first step is mixed with a water extractant and a hydrocarbon extractant, and a hydrocarbon extract liquid phase mainly containing 1,4-butanediol diacrylate and mainly 4-hydroxybutyl acrylate and unextracted. The second step of forming two liquid phases of a water raffinate liquid phase containing the reaction 1,4-butanediol and extracting and separating 1,4-butanediol diacrylate to obtain a water raffinate liquid, and In the method for producing 4-hydroxybutyl acrylate, which comprises each step of recovering 4-hydroxybutyl acrylate from the water extraction residual liquid obtained in the second step, the second step The reaction mixture an amount of water extractant and a hydrocarbon extractant to be mixed with the material, consists in the production method of the 4-hydroxybutyl acrylate, characterized in that the respective following range in. Water extraction agent: 0.4 to 2.5 times by weight based on the weight of the reaction mixture excluding the hydrocarbon solvent Hydrocarbon extraction agent: 2 to 20 times by weight based on the acrylic acid equivalent weight of the acryloyl group present in the reaction mixture ( However, the hydrocarbon solvent present in the reaction mixture is regarded as the mixed hydrocarbon solvent.)

The present invention will be described in detail below. The method for producing 4-hydroxybutyl acrylate (monoester body) according to the present invention is, as described above, the first step in which the esterification reaction is carried out, by-products are extracted and separated from the reaction mixture, and the target product is extracted. It is composed of a second step of obtaining a liquid and a third step of recovering the target substance from the raffinate, and the second step is particularly characterized.

In the above-mentioned first step, acrylic acid and 1 to 2 mol times, preferably 1 to 1.5 mol times, of acrylic acid and 1,4-butanediol are added in the presence of an acidic catalyst and a hydrocarbon solvent. Below, the water produced by the esterification reaction (hereinafter referred to as "reaction product water") is distilled off.
The reaction mixture is obtained by reacting under reflux of a hydrocarbon solvent until generation of water of reaction product disappears.

When the amount of diol to acrylic acid is less than 1 mol times in the first step, the production rate of the diester is increased, which not only makes it difficult to extract and separate the diester in the second step described later. The amount of the water extractant must be increased in order to widen the 3 liquid phase forming region and form the 2 liquid phase, and the object of the present invention cannot be achieved. The formation of two liquid phases in the second step means that a hydrocarbon extraction liquid phase mainly containing a diester body and a water extraction residual liquid phase mainly containing a monoester body and an unreacted diol are formed. Good, 3 in the second step
Liquid phase formation means that, in addition to the above two liquid phases, three kinds of liquid phases are formed in which a new oil phase containing a diester body and a monoester body as a main component is added. Further, when the amount of diol with respect to acrylic acid exceeds 2 mole times, the amount of unreacted diol in the reaction mixture increases, which not only lowers the production efficiency of the reaction step, but also increases the amount of treatment liquid in the second step described below. Also, the amount of diol recovered increases and the cost increases. From this point, the amount of diol to acrylic acid is 1.5.
It is preferable to stop it at a molar ratio or less.

As the acidic catalyst used in the first step, those conventionally used can be used, and specific examples thereof include sulfonic acids, sulfuric acid and acidic ion exchange resins. The amount used is 0.0 with respect to the starting acrylic acid.
It is in the range of 2 to 10 mol%, preferably 0.1 to 5 mol%.

The hydrocarbon solvent used in the first step is
Usually, an azeotropic composition is prepared with water, and when the azeotropic composition is cooled and condensed, it is separated into water and two liquid phases. Specific examples of suitable hydrocarbon solvents include aliphatic hydrocarbons such as pentane, hexane, or heptane; alicyclic hydrocarbons such as cyclohexane; and aromatic hydrocarbons such as benzene or toluene. Also,
The amount used is usually 0.1 to 2 times the weight of the reaction raw materials (acrylic acid and diol).

In the first step, it is necessary to distill off the water produced by the reaction and carry out the reaction under the reflux of the hydrocarbon solvent. When the hydrocarbon solvent forms an azeotropic composition with water, the reaction product water is distilled off as an azeotropic mixture with the hydrocarbon solvent, the resulting mixture is cooled and condensed, and then the hydrocarbon solvent separated into two liquid phases is By refluxing the reaction system and removing water out of the system, the reaction conversion rate of acrylic acid can be increased, which is preferable. In this way, the reaction proceeds, and when the generation of the water produced by the reaction is stopped, the esterification reaction is complete. Therefore, this can be confirmed and the reaction mixture can be withdrawn. Then, the extracted reaction mixture is transferred to the subsequent second step.

The reaction time in the first step depends on the reaction temperature,
Although it varies depending on the type and amount of the catalyst, it is usually in the range of 2 to 20 hours. Although the reaction temperature is determined by the reflux temperature of the hydrocarbon solvent used, it is usually preferably in the range of 50 to 140 ° C. If the reaction temperature is lower than 50 ° C., the reaction rate becomes slow, and if it is higher than 140 ° C., side reactions such as a polymerization reaction easily occur, which are not preferable. A polymerization inhibitor can be added to the reaction system of the first step as a kind of side reaction inhibitor. Examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, phenothiazine, p-phenylenediamine and the like. The addition amount is usually 0.01 to 2 with respect to the raw material acrylic acid.
It is preferable to set it in the range of wt%, and at the same time, it is preferable to introduce a gas body containing molecular oxygen such as air. The reaction in this step is usually carried out under normal pressure, but it may be carried out under reduced pressure or under increased pressure, and may be carried out in either a batch system or a continuous system.

Next, the second step will be described. In the second step, the reaction mixture obtained in the first step is mixed with a water extractant and a hydrocarbon extractant, and a hydrocarbon extract liquid phase mainly containing a diester and a monoester and an unextracted liquid phase. Two liquid phases, a water raffinate liquid phase containing a reaction diol, are formed, and a by-product diester body is extracted and separated as a hydrocarbon extract to obtain a water raffinate liquid containing substantially no diester body. This is a step of transferring this water extraction residual liquid to the subsequent third step. Hexane, heptane, octane, cyclohexane, etc. are mentioned as a typical example of the hydrocarbon extractant which can be conveniently used in the second step. In the second step, the reaction mixture obtained in the first step can be used as it is, but it is also possible to use it after neutralizing, removing or washing the acidic catalyst, if necessary. Furthermore, when the hydrocarbon extractant used in the second step and the hydrocarbon solvent used in the first step are different, the hydrocarbon solvent in the reaction mixture obtained in the first step is previously removed by distillation or the like. It is preferable to keep it.

The method of the present invention has a great feature in the extraction conditions in the second step, and the amount of the water extractant to be mixed with the reaction mixture depends on the amount of the reaction mixture (excluding the weight of the hydrocarbon solvent when it is contained). The amount of the hydrocarbon extractant to be mixed in the reaction mixture is 0.4 to 2.5 times the weight, and the amount of the hydrocarbon extractant to be mixed in the reaction mixture is 2 to 20 times the weight of the acryloyl group present in the reaction mixture in terms of acrylic acid. (However, the hydrocarbon solvent present in the reaction mixture is regarded as a mixed hydrocarbon extractant.) Is an essential requirement.

The amount of water extraction agent mixed with the reaction mixture is 0.4
If it is less than 1 times by weight, the extraction rate of the diester compound will decrease,
Preferable extraction cannot be performed unless the number of extraction stages during the extraction operation is significantly increased. Further, when the amount of the water extractant is more than 2.5 times by weight, for example, about 3 times by weight, during the extraction operation, the hydrocarbon extraction liquid phase mainly containing the diester body, mainly the monoester body, and the unreacted diol are extracted. It is not possible to form a two liquid phase with a water extraction residual liquid phase containing
A three-liquid phase is formed by adding an oil phase mainly composed of a diester and a monoester to the two liquid phases. Under such conditions, not only the extraction rate of the diester into the hydrocarbon extraction liquid phase is extremely lowered, but also complicated treatment under the formation of three liquid phases is required, which is not practical. It should be noted that if the amount of the water extractant is further increased to 5 times by weight, a predetermined two liquid phases are formed, but the amount of the processing liquid in the subsequent third step increases, which is industrially extremely disadvantageous. . The amount of the water extractant to be mixed with the reaction mixture can be arbitrarily selected from the above range, but the extraction rate, the number of extraction stages and the amount of treatment liquid when performing the extraction operation, and further the treatment amount in the subsequent third step, etc. Considering comprehensively, the range of 0.5 to 2 times by weight is preferable.

When the amount of the above-mentioned hydrocarbon extractant mixed with the reaction mixture is less than 2 times the weight of the acryloyl group present in the reaction mixture in terms of acrylic acid, the diester body is extracted into the liquid phase of the hydrocarbon extract. This is not preferable because the rate is lowered and it is necessary to increase the number of extraction stages when performing the extraction operation. Further, even if the amount of the hydrocarbon extractant is more than 20 times by weight, the extraction rate of the diester body is almost the same as when it is about 20 times by weight, and since the amount of the treatment liquid only increases, it should be kept at 20 times by weight or less. Is good. The amount of the hydrocarbon extractant to be mixed with the reaction mixture can be arbitrarily selected from the above range, but when comprehensively considering the extraction rate, the number of extraction stages when performing the extraction operation, the amount of treatment liquid in the second step, and the like, It is preferably in the range of 3 to 12 times by weight.

The extraction temperature in the second step is usually from room temperature to 9
The range of 0 ° C is preferred. The upper limit of the extraction temperature depends on the type of the hydrocarbon extractant used, but if the extraction temperature is too high, the hydrocarbons are vaporized in the extractor and the extraction efficiency is reduced, which is not preferable. The extraction operation in the second step is generally performed in multiple stages, and may be either a batch system or a continuous system, but in the case of a continuous system, it is a tower type such as a rotary disk type continuous extraction tower. Preference is given to using an extractor.

Next, the third step will be described. In the third step, the water extraction residual liquid obtained in the second step is used as it is. This water extraction residual liquid mainly contains monoester and unreacted diol. In this step, both are separated by a conventionally known method,
The desired monoester (4-hydroxybutyl acrylate) may be isolated. Specifically, for example, dichloromethane, acetic acid n
-A mixture of organic solvents such as butyl, ethyl acetate or methyl isobutyl ketone as an extractant, leaving unreacted diol in the aqueous phase, extracting the desired monoester into the organic solvent extraction liquid phase, and then extracting this organic solvent A method of distilling the organic solvent in the liquid by a distillation operation and recovering a monoester body as a distillation residue is common, but of course, a method other than this may be used.

[0025]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the description of the following Examples unless it exceeds the gist.

Example 1 <First Step> In a reactor having a capacity of 15 l equipped with a reflux condenser, a thermometer and a stirrer, 2880 g (40 mol) of acrylic acid, 4690 g (52 mol) of 1,4-butanediol, 1500 ml of n-heptane (hydrocarbon solvent), 15 ml of concentrated sulfuric acid (esterification catalyst), and 15.9 g of phenothiazine (polymerization inhibitor) were charged, and an oxygen / nitrogen mixed gas with an oxygen concentration of 4% was blown at 25 l / hr. "The temperature was raised while stirring. In this case, the charged molar ratio of raw materials (1,4-butanediol / acrylic acid) was 1.3.
Is.

When the temperature of the contents of the reactor reaches 90 to 97 ° C., the water produced by the reaction is azeotropically distilled off with n-heptane and the n-heptane is refluxed, and the reaction is continued until no water is produced. After that, a reaction mixture was obtained. The obtained reaction mixture was analyzed by gas chromatography, and as a result, the composition of this reaction mixture was found to be 43.3% by weight of monoester, 18.9% by weight of diester, 18.8% by weight of diol,
It was 15.0% by weight of n-heptane.

<Second Step> Prior to the extraction operation, the reaction mixture was added with the weight of 1. excluding the n-heptane content.
0 weight times (equal amount) of water was mixed and neutralized to a pH range of 6.5 to 7.0 using a sodium hydroxide aqueous solution having a concentration of 24 weight%. Next, a rotating disk type continuous extraction tower with a jacket having a diameter of 50 mm and an apparatus number of 60 was used as an extraction apparatus, and the reaction mixture after the neutralization was carried out at a rate of 2050 g / Hr. Also, from the 60th stage (light liquid supply port), 2030, n-heptane (extractant) was added.
By continuously supplying each at a rate of g / Hr., the n-heptane extract stably flows out from the uppermost part (light liquid outlet) of the extraction tower, and from the lowermost part (heavy liquid outlet). The water extraction residual liquid steadily flowed out, and an n-heptane extract and a water extraction residual liquid were obtained by this extraction operation. During this period, hot water of 50 ° C was passed through the jacket of the extraction tower to increase the extraction temperature to 5
It was set to 0 ° C. The components in the n-heptane extract obtained from the uppermost part of the extraction column were analyzed by gas chromatography to calculate the extraction rates of diester and monoester. The results are shown in Table 1 together with the amount of water extractant added and the amount of n-hepta in the extraction step.

<Third Step> Dichloromethane was added to the water extraction residue obtained from the bottom of the extraction column to recover the monoester as a dichloromethane extract, and this extract was subjected to thin film distillation under reduced pressure. The desired monoester (4-hydroxybutyl acrylate) was obtained.

Example 2: In the example described in Example 1,
The amount of water mixed in the reaction mixture was changed to 0.5 times (half) the weight of the reaction mixture excluding the n-heptane content,
In addition, the reaction mixture after neutralization supplied to the extraction tower was 1680.
2240 g / Hr. of n-heptane supplied to the extraction column
n-heptane extract and water extraction residue were obtained from the extraction column in the same manner as in the same example except that g / Hr.
The components in the obtained n-heptane extract were analyzed to calculate the extraction rate of diester and monoester. The results are shown in Table 1.

Example 3: In the example described in Example 1,
The amount of water mixed in the reaction mixture was changed to 2.0 times the weight of the reaction mixture excluding the n-heptane content, and the reaction mixture after neutralization supplied to the extraction column was 2330 g / hr.
, 1660 g / Hr. Of n-heptane supplied to the extraction tower.
In the same manner as in the same example except that the n-heptane extract and the water extraction residue were obtained from the extraction column, the components in the obtained n-heptane extract were analyzed, and the diester and The extraction rate of the monoester was calculated. The results are shown in Table 1.

Comparative Example 1: In the example described in Example 1,
The amount of water mixed in the reaction mixture was changed to 5.0 times the weight of the reaction mixture excluding the n-heptane content, and the reaction mixture after neutralization supplied to the extraction column was 3010 g / hr.
In the same manner as in the same example except that the amount of n-heptane supplied to the extraction tower was changed to 990 g / Hr.
-The components in the heptane extract were analyzed to calculate the extraction rate of diester and monoester. The results are shown in Table 1.

Comparative Example 2: In the example described in Example 1,
The amount of water mixed in the reaction mixture was changed to 3.0 times the weight of the reaction mixture excluding the n-heptane content, and the reaction mixture after neutralization supplied to the extraction column was 2680 g / hr.
, 1320 g / Hr. Of n-heptane supplied to the extraction tower.
Extraction was attempted in the same manner as in the same example except that the extraction tower was not operated. Examination by batch extraction revealed that three liquid phases were formed under these conditions. The results are also shown in Table 1 below.

Comparative Example 3: In the example described in Example 1,
The amount of water mixed in the reaction mixture was changed to 0.25 times the weight of the reaction mixture excluding the n-heptane content, and
1520 g / H of the reaction mixture after neutralization supplied to the extraction tower
At r., 2410 g / H of n-heptane supplied to the extraction tower
In the same manner as in the same example except that each was changed to r., an n-heptane extract and a water raffinate were obtained from the extraction column, and the components in the obtained n-heptane extract were analyzed to obtain the diester. Body and monoester form extraction rates were calculated. The results are shown in Table 1.

[0035]

[Table 1]

The following is clear from Table 1. (1) When the amounts of the water extractant and the hydrocarbon extractant to be mixed with the reaction mixture in the second step are within the specific ranges specified in the present invention, the diester body can be selectively extracted and separated at a high extraction rate ( Examples 1 to 3). (2) When the amount of the water extractant to be mixed with the reaction mixture in the second step is much larger than the specified range, the extraction rate and selectivity of the diester are good, but the load of the second step and the third step Is large (Comparative Example 1). (3) When the amount of the water extractant mixed in the reaction mixture in the second step exceeds the specified range, three liquid phases are formed during the extraction operation, and the extraction column cannot operate normally (Comparative Example 2). (4) When the amount of the water extractant to be mixed with the reaction mixture in the second step is less than the specified range, the extraction rate of diester and the selectivity are lowered (Comparative Example 3).

[0037]

EFFECTS OF THE INVENTION According to the production method of the present invention, the diester body which is a reaction by-product can be selectively and stably extracted and separated at a high extraction rate from the reaction mixture obtained by the esterification reaction, and Since the amount of the treatment liquid in the step and the third step is small, 4-hydroxybutyl acrylate can be industrially produced advantageously.

Claims (1)

[Claims] 1. Acrylic acid and 1,2-butanediol in an amount of 1 to 2 times the amount of acrylic acid are distilled off in the presence of an acidic catalyst and a hydrocarbon solvent to remove water produced by the esterification reaction. That is, the first step of reacting under reflux of a hydrocarbon solvent to obtain a reaction mixture, and the reaction mixture obtained in the first step is mixed with a water extractant and a hydrocarbon extractant. Forming two liquid phases, a hydrocarbon extraction liquid phase containing butanediol diacrylate and a water extraction residual liquid phase mainly containing 4-hydroxybutyl acrylate and unreacted 1,4-butanediol, From each step of a second step of obtaining a water raffinate by extracting and separating butanediol diacrylate, and a third step of recovering 4-hydroxybutyl acrylate from the water raffinate obtained in the second step Become In the method for producing 4-hydroxybutyl acrylate, the amounts of the water extractant and the hydrocarbon extractant to be mixed with the reaction mixture in the second step are in the following ranges, respectively. Method. Water extraction agent: 0.4 to 2.5 times by weight based on the weight of the reaction mixture excluding the hydrocarbon solvent Hydrocarbon extraction agent: 2 to 20 times by weight based on the acrylic acid equivalent weight of the acryloyl group present in the reaction mixture ( However, the hydrocarbon solvent present in the reaction mixture is regarded as the mixed hydrocarbon solvent.)