JPH07238058A - Production of (meth)acrylic acid tetrahydrobenzyl ester - Google Patents

Abstract

PURPOSE:To obtain a (meth)acrylic acid tetrahydrobenzyl ester useful as e.g. a raw material for a paint, a lens, etc., in high efficiency and yield by ester interchange reaction of tetrahydrobenzyl alcohol with methyl (meth)acrylate in the presence of a specific entrainer. CONSTITUTION:The (meth)acrylic acid tetrahydrobenzyl ester is obtained by ester interchange reaction of tetrahydrobenzyl alcohol with methyl (meth)acrylate by using a catalyst, e.g. tetrabutyl titanate and in the presence of an entrainer azeotropic with methanol having an azeotropic temperature T1 which satisfies the equation T1<T2, where T1 is an azeotropic temperature of methanol with the entrainer and T2 is an azeotropic temperature of methanol with methyl (meth)acrylate (e.g. n-hexane or cyclohexane). Further, the usage of the entrainer is preferably in the range of 10-30wt.% based on the total charging amount.

Description

Detailed Description of the Invention

[0001]

[Industrial field] (Meth) acrylic acid ester is easily polymerized by heat, ultraviolet rays, radiation, radicals, etc., so it is widely used as a raw material for paints, lenses, fibers, and adhesives. . Tetrahydrobenzyl (meth) acrylate is a useful compound that can be used as a resin modifier, a cross-linking agent, a coating material, etc., because it has two double bonds with different reactivity in its molecule.

[0002]

2. Description of the Related Art Generally, a (meth) acrylic acid ester is directly esterified from the corresponding alcohol and (meth) acrylic acid, or the corresponding alcohol and methyl (meth) acrylate are available. It is produced by a transesterification reaction with a (meth) acrylic acid ester, which is easy to do.

Corresponding to GB2253208
There is disclosed a method of directly esterifying styrene and (meth) acrylic acid at 80 ° C. in the presence of a sulfuric acid catalyst.

[0004]

According to this method, since sulfuric acid is used as a catalyst, there is a problem that inexpensive materials such as iron cannot be used in the reactor. Also,
Polymer experiment course 9 Monomer synthesis method (edited by the Polymer Society of Japan,
According to Kyoritsu Shuppan), page 147, this method has a problem that polymerization of (meth) acrylic acid often occurs and the yield is lowered. In the case of producing by a transesterification reaction, methyl ester is often used as a raw material in terms of availability, price, and the like. When methylhydrochloride is used as a raw material and tetrahydrobenzyl (meth) acrylate is produced by a transesterification reaction, methyl alcohol is produced as a by-product alcohol.

Methyl alcohol azeotropes with methyl acrylate at 62.5 ° C. under normal pressure, and its azeotropic composition is 46% by weight of methyl acrylate. The same applies to the case of methyl methacrylate, which is known to form an azeotropic composition with methyl alcohol. Since the transesterification reaction is an equilibrium reaction, the yield of the target compound, tetrahydrobenzyl (meth) acrylate, does not increase unless the by-product alcohol is distilled out of the reaction system. Therefore, normally, the alcohol produced as a by-product is distilled out of the reaction system in order to increase the conversion rate.
When the acrylic ester forms an azeotropic mixture, a part of the raw material (meth) acrylic ester is distilled out of the reaction system. ) Acrylic ester is consumed more than when it does not form an azeotrope.

The present inventor has conducted extensive studies to overcome these problems and has arrived at the present invention.

[0007]

Means for Solving the Problems That is, according to the present invention, when tetrahydrobenzyl (meth) acrylate is produced by a transesterification reaction, the azeotropic point of the azeotropic agent and the methanol are T1 and methanol ( Presence of an azeotropic agent with a methanol having an azeotropic point T1, which satisfies the following relational expression (I) T1 <T2 ... (I) when the azeotropic point of methyl (meth) acrylate is T2. By carrying out the reaction below, it became possible to produce tetrahydrobenzyl (meth) acrylate in which the amount of methyl (meth) acrylate used was small.

Specific examples of the azeotropic agent with methanol having an azeotropic point T1 satisfying the above relational expression include n-hexane,
Cyclohexane, 1,1,1-trichloroethane, 1,
1-dichloroethane, 1,2-dichloroethane, 1,2
-Dichloro-1-propene, acetone, 1-bromopropane, 2-bromopropane, 1-chloropropane, 2-
Chloropropane, 2-methylfuran, cyclopentane,
Examples include pentene, pentane, benzene, cyclohexene, hexene, isopropyl ether, heptane, isooctane, and among them, n-hexane and cyclohexane are preferable. The reason for this is that they are inexpensive, readily available, and easily separated from methanol by cooling.

Incidentally, the azeotropic point at 760 Torr is the following temperature. Methanol / methyl acrylate 62.5
C., methanol / methyl methacrylate 64.2 ° C., methanol / n-hexane 50 ° C., methanol / cyclohexane 55 ° C.

The amount of the azeotropic agent used may be in the range of 5 to 50% by weight based on the total charged amount, preferably 10 to 3
Used in the range of 0% by weight. If the concentration of the azeotropic agent is lower than this, a part of the raw material methyl (meth) acrylate will be distilled out of the reaction system, and the amount of methyl (meth) acrylate used will increase. Further, even if the concentration of the azeotropic agent is higher than this, there is no problem in the reaction results and the like, but there is a problem that the substrate concentration decreases and the space-time yield of tetrahydrobenzyl (meth) acrylate decreases. Therefore, it is not so preferable.

The reaction system is usually 100 to 760 Torr, preferably about 200 to 600 Torr. The reason why the reaction is carried out under normal pressure to reduced pressure is that the reaction temperature can be lowered and it is preferable from the viewpoint of preventing polymerization.

Further, the methanol by-produced by the reaction needs to be removed from the reaction system. This is because if the methanol is not removed from the reaction system, the inside of the system will reach an equilibrium state and the reaction will not proceed any further. Further, depending on the catalyst used, when the concentration of methanol in the reaction solution becomes high, there is a problem that the methanol is added to the C = C bond of the (meth) acryl group, so that the by-produced methanol is generated. Need to be removed from the reaction system.

There is no particular problem with any catalyst that can be used in the present invention. Specific examples include sodium methoxide, potassium tert-butoxide, metal alkoxides such as sodium ethoxide, tetrabutyl titanate, titanate esters such as tetraisopropyl titanate, tin compounds and the like, but other than these esters Any catalyst can be used without any problem as long as the exchange reaction proceeds.

Although the concentration of the catalyst used in the reaction varies depending on the catalyst, it is generally used in the range of 0.01 to 5 mol% with respect to the starting material tetrahydrobenzyl alcohol, preferably 0.1. Used in the range of ˜2 mol%. The reaction proceeds even at a concentration lower than this concentration, but it may be difficult to obtain a sufficient reaction rate, so it is better to avoid it. Further, even if the concentration is higher than this, the reaction proceeds sufficiently, but the amount of the catalyst used per production increases, which is not preferable from the economical aspect.

The solvent used in the reaction is represented by the above-mentioned relational expression.
Any substance that satisfies (I) and is substantially inactive under the reaction conditions can be used. Specific examples thereof include n-hexane and cyclohexane. The amount of these solvents to be used can be in the range of 5 to 50% by weight, preferably 10 to 30% by weight, based on the total amount of the solvent. If the solvent concentration becomes lower than this,
Part of the methyl acrylate is distilled out of the reaction system, which causes a problem that the amount used increases. Further, even if the solvent concentration is made higher than this, there is no problem in the reaction results and the like, but there is a problem that the production amount of tetrahydrobenzyl (meth) acrylate per unit volume of the reactor becomes small.

The ratio of tetrahydrobenzyl alcohol to methyl (meth) acrylate used is 1: 1 to 1:20.
It can be used in the range of (mol: mol), and preferably the reaction can be carried out in the range of 1: 1 to 1: 5. The reaction proceeds even if the ratio of methyl (meth) acrylate is lower than this, but it is necessary to separate the unreacted remaining raw material tetrahydrobenzyl alcohol and tetrahydrobenzyl (meth) acrylate. However, since it is very difficult to separate them, it is necessary to avoid lowering the ratio of methyl (meth) acrylate than this. On the contrary, the reaction proceeds even if the ratio of methyl (meth) acrylate is higher than this, but it is necessary to recover or discard the unreacted and large amount of the remaining methyl (meth) acrylate as a raw material.

The reaction temperature can be in the range of about room temperature to 130 ° C., particularly preferably in the range of 40 to 100 ° C. If the reaction temperature is too low, a sufficient reaction rate cannot be obtained, and conversely, if the reaction temperature is too high, the yield tends to decrease due to polymerization, which is not preferable.

At the time of the reaction, it is preferable to add a known polymerization inhibitor to the reaction solution in order to prevent the polymerization, or to carry out the reaction while charging a mixed gas containing oxygen such as air. Examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, phenothiazine, and 3,5-ditertiary-butyl-4-hydroxytoluene.

[0019]

The present invention is configured as described above,
It has become possible to produce tetrahydrobenzyl (meth) acrylate in which the amount of methyl (meth) acrylate used is small.

Hereinafter, the effects of the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 2 equipped with a 10-stage Older Shaw tower and a decanter with an internal volume of 100 ml
In a liter flask, tetrahydrobenzyl alcohol 168.3 g, methyl methacrylate 750 g, dibutyltin oxide 7.5 g, 3,5-di-tert-butyl-4-
Charge 1 g of hydroxytoluene and 190 g of hexane,
The reaction was carried out at 80 ° C. under reduced pressure. In the reaction, the liquid distilled from the top of the distillation column was separated with a decanter, only the upper layer was refluxed, and the lower layer liquid was distilled out of the reaction system to carry out the reaction. During the reaction, dry air was continuously charged into the reaction solution from the capillary.

After reacting for 6 hours, the reaction solution was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 98.5% and the yield of tetrahydrobenzyl methacrylate was 96.4% (based on tetrahydrobenzyl alcohol). )Met.

Further, 49.2 g of the lower layer liquid was distilled. When the lower layer liquid was analyzed by gas chromatography, it was found to be 83.8% by weight of methanol, 8.8% by weight of hexane, and 7.4% by weight of methyl methacrylate.

Example 2 The reaction was carried out under the reaction conditions of Example 1 except that the catalyst was changed to 10.8 g of dioctyltin oxide. After reacting for 6 hours, the reaction solution was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 99.9% and the yield of tetrahydrobenzyl methacrylate was 97.3% (tetrahydrobenzyl alcohol).
It was a standard). Further, 54.8 g of the lower layer liquid was distilled. When the lower layer liquid was analyzed by gas chromatography, it was found that methanol was 76.8% by weight, hexane was 15.8% by weight, and methyl methacrylate was 7.4% by weight.

[Example 3] Under the reaction conditions of Example 2, 750 g of methyl methacrylate was added to 645 of methyl acrylate.
The reaction was performed by changing to g. After reacting for 6 hours, the reaction liquid was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 98.6% and the yield of tetrahydrobenzyl acrylate was 97.5% (based on tetrahydrobenzyl alcohol). It was Further, 52.2 g of the lower layer liquid was distilled. Gas chromatography of the lower layer liquid
As a result of analysis by (7), it was 73.8% by weight of methanol, 18.0% by weight of hexane, and 8.2% by weight of methyl acrylate.

Example 4 Using the reactor of Example 1, the charged amount of tetrahydrobenzyl alcohol 280.
4 g, 626 g of methyl methacrylate, 18 g of dioctyl tin oxide, 1 g of 3,5-di-tertiary-butyl-4-hydroxytoluene, and 200 g of hexane were used for the reaction. After reacting for 6 hours, the reaction solution was analyzed by gas chromatography to find that the conversion rate of tetrahydrobenzyl alcohol was 98.5% and the yield of tetrahydrobenzyl methacrylate was 97.6% (based on tetrahydrobenzyl alcohol). It was Further, 99.2 g of the lower layer liquid was distilled. When the lower layer liquid was analyzed by gas chromatography, it was found to be 74.1% by weight of methanol, 17.5% by weight of hexane and 8.4% by weight of methyl methacrylate.

Example 5 Under the reaction conditions of Example 4, the amount of catalyst was changed to 9 g to carry out the reaction. After reacting for 6 hours, the reaction solution was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 98.2.
%, Tetrahydrobenzyl methacrylate yield 96.7%
(Based on tetrahydrobenzyl alcohol). Also, 98.2 g of the lower layer liquid was distilled. When the lower layer liquid was analyzed by gas chromatography, it was found to be 75.0% by weight of methanol, 18.4% by weight of hexane and 6.6% by weight of methyl methacrylate.

Example 6 Under the reaction conditions of Example 5, 626 g of methyl methacrylate was added to 53% of methyl acrylate.
The reaction was performed by changing the weight to 8.3 g. After reacting for 6 hours, the reaction mixture was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 95.3.
%, Tetrahydrobenzyl acrylate yield 94.3%
(Based on tetrahydrobenzyl alcohol). In addition, 89.8 g of the lower layer liquid was distilled. When the lower layer liquid was analyzed by gas chromatography, it was found that 74.1% by weight of methanol, 19.2% by weight of hexane, and 6.
It was 7% by weight.

Example 7 Under the reaction conditions of Example 5, the amount of catalyst was changed to 4.5 g and the reaction temperature was changed to 90 ° C. to carry out the reaction. The reaction was completed in 5 hours. When the reaction solution was analyzed by gas chromatography, the conversion rate of tetrahydrobenzyl alcohol was 99% and the yield of tetrahydrobenzyl methacrylate was 99% (based on tetrahydrobenzyl alcohol). Further, 113 g of the lower layer liquid was distilled. When the lower layer liquid was analyzed by gas chromatography, it was found to be 68.9% by weight of methanol, 23.0% by weight of hexane and 8.1% by weight of methyl methacrylate.

[Example 8] Using the reactor of Example 1, the charged amount and the catalyst were tetrahydrobenzyl alcohol.
168.3 g, methyl methacrylate 751 g, sodium methoxide 1.62 g, 3,5-di-tertiary-butyl-4-hydroxytoluene 1 g, hexane 190 g
The reaction was carried out at 50-60 ° C under reduced pressure. 2.
The reaction was completed in 5 hours. The reaction solution was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 98.6% and the yield of tetrahydrobenzyl methacrylate was 74.2% (tetrahydrobenzyl alcohol).
It was a standard). Further, 58 g of the lower layer liquid was distilled. When the lower layer liquid was analyzed by gas chromatography, it was found to be 72.8% by weight of methanol, 16.8% by weight of hexane, and 10.4% by weight of methyl methacrylate.

Example 9 Under the reaction conditions of Example 1, hexane was changed to 250 g of cyclohexane to carry out the reaction. After reacting for 6 hours, the reaction liquid was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 98.7% and the yield of tetrahydrobenzyl methacrylate was 97.3% (tetrahydrobenzyl alcohol).
It was a standard). Further, 80.5 g of the lower layer liquid was distilled. When the lower layer liquid was analyzed by gas chromatography, it was found that methanol 52.3% by weight and cyclohexane 32.
It was 1% by weight and 15.6% by weight of methyl methacrylate.

Comparative Example 1 Under the reaction conditions of Example 1, hexane was not charged and the amount of methyl methacrylate charged was changed to 950 g to carry out the reaction. After reacting for 6 hours, the reaction mixture was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 99.0.
%, Tetrahydrobenzyl methacrylate yield 97.6%
(Based on tetrahydrobenzyl alcohol). Also, 185.8 g of distillate was distilled. When the lower layer liquid was analyzed by gas chromatography, methanol 25.6 was obtained.
% By weight, and 74.4% by weight of methyl methacrylate.
(Below margin)

Claims (2)

[Claims] 1. When producing tetrahydrobenzyl (meth) acrylate by transesterification of tetrahydrobenzyl alcohol and methyl (meth) acrylate,
When the azeotropic point of the azeotropic agent and methanol is T1, and the azeotropic point of the methanol and methyl (meth) acrylate is T2, the following relational expression (I) T1 <T2 ... (I) A process for producing tetrahydrobenzyl (meth) acrylate, characterized in that the reaction is carried out in the presence of an azeotroping agent with a satisfactory azeotrope-containing methanol. 2. The method according to claim 1, wherein the azeotropic agent is n-hexane and / or cyclohexane.