JP3312806B2 - Method for producing tetrahydrobenzyl (meth) acrylate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION (Meth) acrylic acid esters are widely used as raw materials for paints, lenses, fibers, etc., and also as adhesives, because they are easily polymerized by heat, ultraviolet rays, radiation, radicals and the like. . Since tetrahydrobenzyl (meth) acrylate has two double bonds having different reactivities in its molecule, it is a useful compound that can be used as a resin modifier, a crosslinking agent, a coating material, and the like.

[0002]

2. Description of the Related Art Generally, (meth) acrylic acid esters are directly esterified from the corresponding alcohol and (meth) acrylic acid, or the corresponding alcohol and methyl (meth) acrylate are obtained. It is produced by a transesterification reaction with a (meth) acrylic acid ester which is easy to perform. GB 2253208 discloses a method of directly esterifying the corresponding alcohol and (meth) acrylic acid at 80 ° C. in the presence of a sulfuric acid catalyst.

[0003]

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, according to page 147 of the Monomer Synthesis Method of Polymer Experiment Course 9 (edited by The Society of Polymer Science, Kyoritsu Shuppan), there is a problem that this method often causes polymerization of (meth) acrylic acid and lowers the yield. is there. Further, according to the study of the present inventors, it has been found that paratoluenesulfonic acid, which is a general transesterification catalyst, does not show much activity as a tetrahydrobenzyl (meth) acrylate synthesis catalyst.

It is generally known that (meth) acrylic acid ester is easily polymerized by heating.
And the higher the temperature, the more likely the polymerization will occur.
Therefore, when producing the target (meth) acrylic acid ester by transesterification or direct esterification, it is preferable to lower the reaction temperature as much as possible from the viewpoint of preventing polymerization.

[0005] The present inventor has repeatedly studied to overcome these problems and arrived at the present invention.

[0006]

That is, according to the present invention, an alkali metal alkoxide and / or an alkaline earth metal alkoxide exhibit excellent activity as a catalyst when producing tetrahydrobenzyl (meth) acrylate by a transesterification reaction. It was found that the transesterification proceeds at a sufficient reaction rate even at lower temperatures.

The catalyst which can be used in the present invention is an alkali metal alkoxide and / or an alkaline earth metal alkoxide, represented by the following general formulas (1) and (2).

MOR (M: Li, Na, K, R
b, Cs, Fr) ··· Formula 1 M (OR) ₂ (M: Be, Mg, Ca, Sr, Ba,
Ra) Formula 2 OR is an alkoxy group having 10 or less carbon atoms.

Of these, alkoxides of sodium or potassium having 4 or less carbon atoms are preferably used as catalysts because of their availability.

Specifically, sodium methoxide, sodium ethoxide, potassium tert-butoxide,
Sodium tanshaliboxide, potassium methoxide, potassium ethoxide, sodium n-propoxide, sodium isopropoxide, potassium n-propoxide and potassium isopropoxide, and the like,
Among them, sodium methoxide, sodium ethoxide,
Potassium tert-butoxide is preferred. The reason is that it is easily available and the price is relatively low.

The concentration of the catalyst used in the present invention is one of the starting materials, tetrahydrobenzyl alcohol-
At a concentration of 0.01 to 5 mol%, preferably 0.5 to 2 mol%, based on the

When the reaction is carried out at a lower concentration than this, there arise problems that the reaction rate becomes slower, the catalyst is deactivated in the course of the reaction, and the reaction does not proceed in the middle. Since the catalyst used in the present invention loses its catalytic activity due to water, it is preferable that the raw materials used in the reaction be dehydrated in advance, but it is not particularly necessary to dehydrate the catalyst at the concentration of the present invention.

The ratio of tetrahydrobenzyl alcohol and (meth) acrylate used as starting materials for producing tetrahydrobenzyl (meth) acrylate is in the range of 1: 1 to 1:20 (molar ratio). The reaction is preferably performed in the range of 1: 1 to 1: 5. The reaction proceeds even if the ratio of (meth) acrylate is lower than 1: 1, but it is necessary to separate the unreacted raw material tetrahydrobenzyl alcohol and tetrahydrobenzyl (meth) acrylate. However, it is very difficult to separate the two, so that the ratio of the (meth) acrylic acid ester should be reduced.

Conversely, the reaction proceeds even if the ratio of the (meth) acrylate is higher than 1:20, but it is necessary to collect or discard the unreacted and remaining raw material (meth) acrylate. Occurs.

The (meth) acrylate used as a raw material is an alcohol (meth) acrylate having 4 or less carbon atoms, specifically, methyl (meth) acrylate,
It is preferable to use ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate.

Alcohol (meth) acrylates having a larger number of carbon atoms can also be used, but the reaction temperature may be increased or alcohol produced as a by-product and tetrahydrobenzyl alcohol as a raw material may be used. It is preferable to use an alcohol (meth) acrylate having 4 or less carbon atoms since problems such as separation become difficult. Among these, methyl methacrylate is preferably used from the viewpoint of easy availability and easy removal of alcohol generated by transesterification. The reaction can be performed at a reaction temperature in the range of around room temperature to 100 ° C, and particularly preferably in the range of 40 to 70 ° C.

If the reaction temperature is too low, a sufficient reaction rate cannot be obtained, and if the reaction temperature is too high, the yield tends to decrease due to polymerization.

The reaction system is usually operated at 100 to 760 Torr, preferably about 200 to 600 Torr, in order to remove the alcohol generated by the transesterification reaction. Alcohol generated in the decompression system
Unless the ester is removed, the transesterification reaches an equilibrium state and does not proceed any further.

In the transesterification reaction, it is possible to use a reaction solvent inert to the reaction. Specifically, chain or cyclic aliphatic hydrocarbons such as pentane, hexane, heptane, cyclohexane and methylcyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, anisole, diethyl ether, tetrahydrofuran, dioxane Can be used alone or in combination. It is preferable to use a reaction solvent having a boiling point higher than that of the alcohol desorbed by the transesterification reaction.

At the time of the reaction, a known polymerization inhibitor is added to the reaction solution to prevent polymerization of the (meth) acryl group.

Alternatively, it is preferable to carry out the reaction while charging a mixed gas containing oxygen such as air. Specific examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, phenothiazine, 3,5-di-tert-butyl-4-hydroxytoluene, and the like. The amount of the polymerization inhibitor used is 10 to 5000 ppm, preferably
It is about 100 to 1000 ppm.

[0022]

The present invention is configured as described above.
By using an alkali metal alkoxide and / or an alkaline earth metal alkoxide as a catalyst when producing tetrahydrobenzyl (meth) acrylate by a transesterification reaction, the reaction rate of (meth) It has become possible to produce tetrahydrobenzyl acrylate.

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 1 168.3 g of tetrahydrobenzyl alcohol and 751 methyl methacrylate were placed in a 2 liter flask equipped with a 10-stage Oldershaw tower.
g, 1.62 g of sodium methoxide [2 mol% based on tetrahydrobenzyl alcohol], 3,5-dita-
Charg-butyl-4-hydroxytoluene (1 g) and hexane (190 g) as a reaction solvent were charged, and 50 to 6
The reaction was carried out at 0 ° C. while removing methanol from the top of the tower. During the reaction, dry air was continuously charged into the reaction solution from the capillary. Distillation of methanol from the top was stopped in 2.5 hours. Gas chromatography of the reaction solution
When analyzed by tetrahydrobenzyl alcohol-
The conversion was 98.6%, and the yield of tetrahydrobenzyl methacrylate was 74.2% (based on tetrahydrobenzyl alcohol).

Example 2 A reaction was carried out by changing 751 g of methyl methacrylate of Example 1 to 645.8 g of methyl acrylate. The reaction was completed in 3 hours, and the reaction mixture was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 94.2% and the yield of tetrahydrobenzyl acrylate was 73.4% (based on tetrahydrobenzyl alcohol). there were.

Comparative Example 1 The reaction was carried out under the same reaction conditions as in Example 1 except that the catalyst was changed to 5.7 g of paratoluenesulfonic acid, and the reaction temperature was changed to 80 ° C. After performing the reaction for 6 hours, the reaction solution was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 39.5.
%, Tetrahydrobenzyl methacrylate yield 14.2%
(Based on tetrahydrobenzyl alcohol).

Example 3 The reaction was carried out under the same conditions as in Example 1 except that 1.62 g of sodium methoxide was changed to 2.04 g of sodium ethoxide.

The reaction was completed in 3 hours, and the reaction mixture was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 97% and the yield of tetrahydrobenzyl acrylate was 73% (tetrahydrobenzyl alcohol).
Standards).

Example 4 A reaction was carried out under the reaction conditions of Example 1 except that 1.62 g of sodium methoxide was changed to 5.85 g of potassium tert-butoxide.

The reaction was completed in 3 hours, and the reaction mixture was analyzed by gas chromatography to find that the conversion of tetrahydrobenzyl alcohol was 96.5% and the yield of tetrahydrobenzyl acrylate was 73% (based on tetrahydrobenzyl alcohol). Met.

(Hereinafter referred to as margin)

Claims (3)

(57) [Claims] (1) tetrahydrobenzyl alcohol and (meth)
Ta) By transesterification with acrylic acid ester,
When producing tetrahydrobenzyl (meth) acrylate
And tetrahydrobenzyl alcohol: (meth) acrylic acid
The ester (mol ratio) is in the range of 1: 1 to 1: 5, and an alkali metal alkoxide and / or an alkaline earth metal alkoxide is used as a catalyst in tetrahydrobenzyl alcohol.
0.01 to 5 mol% based on the weight of the mixture, and do not charge a mixed gas containing air or oxygen as necessary.
However, at a reaction temperature of 40 to 70 ° C., the reaction is completed within 3 hours.
T) A method for producing tetrahydrobenzyl acrylate . 2. The method for producing tetrahydrobenzyl (meth) acrylate according to claim 1, wherein the metal alkoxide is an alkali metal alkoxide and / or an alkaline earth metal alkoxide having an alkyl group having 4 or less carbon atoms. 3. The method according to claim 1, wherein the alkali metal alkoxide and / or the alkaline earth metal alkoxide is sodium methoxide,
3. The method for producing tetrahydrobenzyl (meth) acrylate according to claim 2, which is at least one selected from sodium ethoxide and potassium tertiary butoxide.