JP7624898B2 - Method for producing β-methallyl acetate - Google Patents

Description

The present invention relates to a method for producing β-methallyl acetate.

β-Methallyl acetate (hereinafter also referred to as "MAAc") is one of the raw materials for 2-methylene-1,3-propanediol diacetate (hereinafter also referred to as "MPDAc"). MPDAc is used, for example, as a modifier (comonomer) for ethylene-vinyl alcohol copolymer (hereinafter also referred to as "EVOH"). MPDAc-modified EVOH obtained by saponifying a copolymer of ethylene, vinyl ester, and MPDAc has the characteristics of having improved stretchability and shrinkability while maintaining good barrier properties compared to unmodified EVOH.

As a method for synthesizing MAAc, which is one of the raw materials for MPDAc, the following method is known.
(1) A method of reacting methallyl chloride with a metal acetate in a solvent (see Patent Document 1)
(2) A method using isobutene, acetic acid and mercury (II) acetate (see Patent Document 2)
(3) A method of reacting isobutene with acetic acid in an oxygen-containing atmosphere using a composite catalyst of palladium, gold and silica (Patent Document 3)
(4) A method of reacting β-methallyl alcohol with acetic anhydride in a dichloromethane solvent (Non-Patent Document 1)

Patent Document 4 also describes a method for synthesizing an unsaturated ester by transesterification of an unsaturated alcohol, in which 2-isopropenyl-5-methyl-4-hexen-1-ol and an alkyl senecioate are used as raw materials, and a transesterification reaction is carried out while removing the by-product alcohol to synthesize 2-isopropenyl-5-methyl-4-hexen-1-yl-3-methyl-2-butenoate.

JP 2009-107949 A Japanese Patent Application Publication No. 47-42601 International Publication No. 2020-022365 JP 2016-108334 A

Thomas P. Blaisdell et al., “Hydroxyl-Directed Stereoselective Diboration of Alkenes,” Journal of the American Chemical Society, 2014, 136(26), p9264-9267

In the case of the method using methallyl chloride in the above Patent Document 1, the obtained MAAc usually contains about 1 to 1,000 ppm of chlorine compounds. Therefore, when the obtained MAAc is used to synthesize MPDAc or the like by a metal catalyzed reaction, the life of the metal catalyst is shortened. The method in the above Patent Document 2 uses organic mercury, which is not preferable as an industrial production method because it generates waste materials containing mercury. In the case of the method in the above Patent Document 3 in which isobutene and acetic acid are reacted in an oxygen-containing atmosphere, excessive oxidation reactions also proceed, making it difficult to selectively synthesize only MAAc in a high yield. In the case of the method in the above Non-Patent Document 1 in which acetic anhydride is used, a neutralization process of the by-product acetic acid is required, so the yield of the obtained MAAc is not sufficient and the amount of raw material required is large (see Comparative Examples 7 and 8).

In addition, when the method using the transesterification reaction described in Patent Document 4 is applied to the synthesis of MAAc as it is, that is, when β-methallyl alcohol (hereinafter also referred to as "MALY") and alkyl acetate are used as raw materials and transesterification reaction is performed while removing the by-product alkyl alcohol, the following problems arise. First, due to the low boiling point of alkyl acetate, which is one of the raw materials, the reaction temperature cannot be increased, and the reaction rate is slow. In addition, since the alkyl acetate forms an azeotropic mixture with the by-product alkyl alcohol and is distilled out of the system, high-purity MAAc cannot be obtained efficiently and in high yield (see Comparative Example 9). In addition, if the amount of MALY remaining in the obtained MAAc is large, it becomes a factor that greatly shortens the catalyst life when applied to an oxidation reaction using a solid catalyst. In other words, unsaturated aldehydes are generated by the oxidation reaction of the remaining MALY, and the unsaturated aldehydes polymerize and cover the surface of the solid catalyst, causing a decrease in the life of the solid catalyst. On the other hand, when using alkyl acetate esters with high boiling points, the boiling point of the by-product alkyl alcohol approaches or exceeds the boiling point of MALY, making it difficult to synthesize MAAc by transesterification (see Comparative Example 5).

The present invention was made based on these circumstances, and its purpose is to provide a method for producing β-methallyl acetate that can efficiently obtain β-methallyl acetate with high purity and high yield.

The above objectives are:
[1] A method for producing β-methallyl acetate, comprising a step of carrying out an ester exchange reaction between β-methallyl alcohol (X) and an alkyl acetate (Y) in the presence of a neutral catalyst while adding an alkyl acetate (Y) to the reaction system and removing an alkyl alcohol (W) produced therewith to the outside of the system so that the molar ratio (Y/(X+Z)) of the alkyl acetate (Y) to the total amount of β-methallyl alcohol (X) and the product β-methallyl acetate (Z) in the reaction system is maintained in the range of 0.005 to 0.5, wherein the alkyl acetate (Y) is at least one selected from the group consisting of methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, and tert-butyl acetate, and the reaction temperature in the step is 10° C. or higher and 150° C. or lower than the lower of the boiling point of the alkyl acetate (Y) and the boiling point of the alkyl alcohol (W) under the atmospheric pressure of the reaction environment;
[2] The method for producing β-methallyl acetate according to [1], wherein the alkyl acetate (Y) is methyl acetate;
[3] The method for producing β-methallyl acetate according to [1], wherein the acetate alkyl ester (Y) is ethyl acetate;
[4] The method for producing β-methallyl acetate according to any one of [1] to [3], wherein at least a part of the alkyl acetate ester (Y) removed from the system together with the alkyl alcohol (W) in the above step is reused for the transesterification reaction in the above step;
[5] The method for producing β-methallyl acetate according to any one of [1] to [4], wherein the above steps are carried out until the yield of β-methallyl acetate (Z) becomes 95% or more;
This is achieved by providing

The present invention provides a method for producing β-methallyl acetate that can efficiently produce β-methallyl acetate with high purity and high yield.

FIG. 1 is a graph showing the relationship between the MALY concentration and the boiling point (reflux temperature) in a mixture of MALY and methyl acetate or methanol. FIG. 2 is a graph showing the relationship between the MALY concentration and the boiling point (reflux temperature) in a mixture of MALY and ethyl acetate or ethanol.

The method for producing β-methallyl acetate (MAAc; 2-methyl-2-propenyl acetate) of the present invention comprises a step of carrying out an ester exchange reaction between β-methallyl alcohol (MALY:X) and an alkyl acetate (Y) in the presence of a neutral catalyst while adding an alkyl acetate (Y) to the reaction system and removing the alkyl alcohol (W) produced therewith to the outside of the system so that the molar ratio (Y/(X+Z)) of the alkyl acetate (Y) to the total amount of MALY (X) and the product MAAc (Z) in the reaction system is maintained in the range of 0.005 to 0.5, in which the alkyl acetate (Y) is at least one selected from the group consisting of methyl acetate, ethyl acetate, normal propyl acetate, isopropyl acetate, and tert-butyl acetate, and the reaction temperature in the step is at least 10°C higher than the lower of the boiling point of the alkyl acetate (Y) and the boiling point of the alkyl alcohol (W) under the atmospheric pressure of the reaction environment and at most 150°C. The reaction scheme for the transesterification reaction in this production method is as follows:

In the above scheme, Ac is an acetyl group (CH ₃ —CO—), and R is a methyl group, an ethyl group, a normal propyl group, an isopropyl group, or a tertiary butyl group.

In this production method, a neutral catalyst is used as the catalyst, so that decomposition of the raw material MALY (X) is unlikely to occur. On the other hand, when an acid catalyst such as sulfuric acid or paratoluenesulfonic acid is used as the catalyst, it is difficult to obtain MAAc (Z) in high yield due to partial decomposition of MALY (X). In addition, in this production method, an alkyl acetate ester (Y) is used as the acetic acid source, so unlike when acetic anhydride is used, acetic acid is not by-produced and neutralization treatment is not required. In other words, since there is no need to perform neutralization treatment in this production method, MAAc (Z) can be obtained efficiently with high purity and high yield.

Next, with regard to the reaction temperature and the selection of the alkyl acetate (Y) in the production method, the boiling points of the raw material compounds and the resulting compounds at 1 atmospheric pressure are shown below.
MALY(X): 113℃
MAAc(Z): 115℃
Methyl acetate: 57°C Methanol: 65°C
Ethyl acetate: 77°C Ethanol: 78°C
n-Propyl acetate: 97°C n-Propanol: 97°C
i-Propyl acetate: 89°C i-Propanol: 83°C
t-Butyl acetate: 96°C t-Butanol: 82°C
(reference)
i-Butyl acetate: 118°C i-Butanol: 108°C
n-Butyl acetate: 126°C n-Butanol: 118°C

In this production method, since an alkyl acetate (Y) having a relatively low boiling point is used, the distillation of MALY (X) and MAAc (Z) together with the alkyl alcohol (W) is suppressed when the transesterification reaction is carried out at a predetermined temperature, and high-purity MAAc (Z) can be obtained by distillation or the like. Here, if a large amount of an alkyl acetate (Y) having a low boiling point is charged from the beginning, the reaction temperature cannot be increased. In contrast, in this production method, the content of the alkyl acetate (Y) in the reaction system (reaction liquid) is maintained within a small range while the transesterification reaction is carried out, so the reaction temperature can be relatively increased. As a result, this production method makes it possible to efficiently obtain MAAc with high purity and high yield.

Furthermore, this manufacturing method has the advantage that the resulting MAAc contains substantially no chlorine compounds because compounds that do not contain chlorine are used as raw materials.

The method for producing MAAc of the present invention will be described in detail below. The method includes a step of obtaining MAAc (Z) by transesterification of MALY (X) and alkyl acetate (Y) (transesterification step). This transesterification is carried out while removing the by-product alkyl alcohol (W) from the reaction system, i.e., from the reaction liquid containing MALY (X), alkyl acetate (Y), etc. Usually, this transesterification is carried out in a boiling (azeotropic) state of the reaction liquid, and the alkyl alcohol (W) is removed from the system by fractional distillation. During this fractional distillation, usually, a part of the alkyl acetate (Y), which has a boiling point close to that of the alkyl alcohol (W), is also distilled. In addition, MALY (X) and MAAc (Z), which have high boiling points, basically remain in the reaction system (reaction liquid). This transesterification is preferably carried out while refluxing at least a part of the alkyl acetate (Y), and at this time, a part of the alkyl alcohol (W) may also be refluxed. The transesterification reaction can be suitably carried out under an inert gas atmosphere such as a nitrogen atmosphere.

(Neutral catalyst)
The catalyst used in the transesterification reaction is not particularly limited as long as it is a neutral catalyst that catalyzes the transesterification reaction between MALY (X) and the alkyl acetate (Y). The neutral catalyst refers to a catalyst other than an acid catalyst or a base catalyst.

Neutral catalysts include:
aluminum-based catalysts (catalysts containing aluminum atoms) such as aluminum trichloride, triethoxyaluminum, and triisopropoxyaluminum;
Zinc-based catalysts (catalysts containing zinc atoms) such as zinc chloride and zinc bromide;
boron-based catalysts (catalysts containing boron atoms) such as boron trifluoride, boron trichloride, and boron tribromide;
Tin-based catalysts (catalysts containing tin atoms) such as tin tetrachloride, dibutyltin dichloride, tetrabutoxytin, dibutyldimethoxytin, dibutyltin oxide, monobutyltin oxide, and dibutyltin dichloride;
titanium-based catalysts (catalysts containing titanium atoms) such as titanium tetrachloride, titanium tetrabromide, tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium, and titanium (IV) oxide;
Zirconium catalysts (catalysts containing zirconium atoms) such as tetrapropoxyzirconium and tetrabutoxyzirconium
etc.

Among these, titanium-based catalysts and aluminum-based catalysts are preferred, and titanium-based catalysts are more preferred. The neutral catalyst is also preferably a metal alkoxide. The metal alkoxide is preferably an alkoxide with a trivalent or tetravalent metal ion. Examples of the metal alkoxide include aluminum alkoxides (such as the above-mentioned triethoxyaluminum and triisopropoxyaluminum), tin alkoxides (such as the above-mentioned tetrabutoxytin and dibutyldimethoxytin), titanium alkoxides (such as the above-mentioned tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium, and tetrabutoxytitanium), and zirconium alkoxides (such as the above-mentioned tetrapropoxyzirconium and tetrabutoxyzirconium). Among these, aluminum alkoxides and titanium alkoxides are preferred, and titanium alkoxides are more preferred. One or more types of neutral catalysts can be used.

The amount of the neutral catalyst used in the transesterification reaction is preferably 0.001 mol or more and 0.5 mol or less, and more preferably 0.003 mol or more and 0.1 mol or less, per 1.0 mol of MALY(X).

(Acetic acid alkyl ester (Y))
The alkyl acetate (Y) is at least one selected from the group consisting of methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate and tert-butyl acetate.

Among the alkyl acetates (Y), methyl acetate and ethyl acetate are preferred. In addition to being relatively inexpensive, the use of these esters with small molecular weights reduces the amount of raw material used to produce the same amount of MAAc (Z), and also reduces the energy consumed when heating to perform the transesterification reaction. In addition, since these alkyl acetates (Y) and the alkyl alcohols (W) produced from them have particularly low boiling points, when the transesterification reaction is performed at a specified temperature, the distillation of MALY (X) and MAAc (Z) together with the alkyl alcohol (W) is more suppressed, and the yield tends to be higher.

An example of suitable conditions when methyl acetate is used as the alkyl acetate (Y) is described below. FIG. 1 is a graph showing the boiling points (reflux temperatures) of a mixture of MALY and methyl acetate and a mixture of MALY and methanol. It can be seen that the higher the concentration of MALY, in other words, the lower the concentration of methyl acetate, etc., the higher the reflux temperature (reaction temperature) at which the reaction can be carried out. Furthermore, in the range where the concentration of MALY is high (about 70 mol% to 99 mol%), the mixture of MALY and methyl acetate has a higher reflux temperature, in other words, methanol is easier to distill than methyl acetate. Therefore, when methyl acetate is used as the alkyl acetate (Y) and the transesterification reaction is carried out while refluxing while maintaining the concentration of methyl acetate in a low range, methanol can be distilled relatively efficiently by utilizing the difference in boiling points. To effectively utilize this boiling point difference, it is preferable to carry out the transesterification reaction so that the molar ratio (Y/(X+Z)) of methyl acetate (Y) to the total amount of MALY (X) and methyl acetate (Y) is maintained in the range of 0.01 to 0.4. However, even if the boiling point of the alkyl acetate (Y) is higher than that of the alkyl alcohol (W), the reaction is carried out while adding the alkyl acetate (Y), so that MAAc can be obtained efficiently with high purity and high yield.

Figure 2 is a graph showing the boiling points (reflux temperatures) of a mixture of MALY and ethyl acetate, and a mixture of MALY and ethanol. As in Figure 1, it can be seen that the higher the concentration of MALY, in other words, the lower the concentration of ethyl acetate, etc., the higher the reflux temperature (reaction temperature) at which the reaction can be carried out. In addition, when ethyl acetate is used, since ethyl acetate has a higher boiling point than methyl acetate, the transesterification reaction can be carried out at a higher reaction temperature (reflux temperature) than when methyl acetate is used. Therefore, when ethyl acetate is used, the efficiency tends to be higher than when methyl acetate is used. In addition, when ethyl acetate is used as the acetate, the respective upper explosion limits of ethyl acetate (upper explosion limit value: 11.5 vol%) and ethanol (upper explosion limit value: 19.0 vol%) present in the reaction system are lower than the respective upper explosion limits of methyl acetate (upper explosion limit value: 16 vol%) and methanol (upper explosion limit value: 36.5 vol%) present in the reaction system when methyl acetate is used. Therefore, when ethyl acetate is used as the acetate ester, it is preferable because the reaction can be carried out more safely even if some oxygen is mixed into the reactive distillation column filled with acetate ester and alcohol vapors due to a production problem.

(Reaction conditions, etc.)
The transesterification reaction between MALY (X) and alkyl acetate (Y) is carried out while adding alkyl acetate (Y) to the reaction system so that the molar ratio (Y/(X+Z)) of alkyl acetate (Y) to the total amount of MALY (X) and MAAc (Z) in the reaction system is maintained in the range of 0.005 to 0.5. This transesterification reaction is carried out while removing by-produced alkyl alcohol (W) from the reaction system. The content of each component in the reaction system may be the content of each component in the reaction liquid.

When the raw materials are charged, a reaction liquid is prepared by mixing MALY (X) and an alkyl acetate (Y) so that the molar ratio (Y/X) of the alkyl acetate (Y) to MALY (X) is 0.005 to 0.5. Then, as the transesterification reaction proceeds, the alkyl acetate (Y) is consumed, and some of the alkyl acetate (Y) is distilled together with the alkyl alcohol (W), so that the amount of the alkyl acetate (Y) in the reaction system (reaction liquid) decreases. Therefore, the transesterification reaction is carried out while adding the alkyl acetate (Y) to the reaction system, i.e., while adding it to the reaction liquid, so that the molar ratio (Y/(X+Z)) in the reaction system (reaction liquid) does not deviate from the range of 0.005 to 0.5. The addition of the alkyl acetate (Y) may be carried out sequentially or continuously. The alkyl acetate (Y) may be added while constantly monitoring the content of each component in the reaction system (reaction liquid), or the alkyl acetate (Y) may be added at an appropriate timing and in an appropriate amount based on data on the content of each component once obtained. The molar ratio (Y/(X+Z)) can be estimated from the temperature of the refluxing reaction liquid, the charge amount, the distillate amount, and the distillate composition. Therefore, the alkyl acetate (Y) may be added appropriately while monitoring the temperature change of the reaction liquid.

The lower limit of the molar ratio (Y/(X+Z)) during the transesterification reaction is 0.005, preferably 0.01, and more preferably 0.02. If the molar ratio (Y/(X+Z)) during the transesterification reaction is below the lower limit, the raw material MALY (X) and the product (target product) MAAc (Z) are more likely to be distilled together with the alkyl alcohol (W), etc., resulting in a decrease in yield. The upper limit of the molar ratio (Y/(X+Z)) during the transesterification reaction is 0.5, preferably 0.4, and more preferably 0.3. If the molar ratio (Y/(X+Z)) during the transesterification reaction exceeds the upper limit, it becomes difficult to raise the reaction temperature sufficiently, and high-purity MAAc cannot be obtained efficiently. Note that the molar ratio (Y/(X+Z)) does not have to be constant during the transesterification reaction, and it is sufficient to maintain it within a specified range.

The reaction temperature during the transesterification reaction is 10°C or more higher than the lower of the boiling point of the alkyl acetate (Y) and the boiling point of the alkyl alcohol (W) under the atmospheric pressure of the reaction environment, and 150°C or less. The reaction temperature is preferably 15°C or more higher than the lower of the boiling point of the alkyl acetate (Y) and the boiling point of the alkyl alcohol (W) under the atmospheric pressure of the reaction environment, more preferably 20°C or more higher, and even more preferably 25°C or more, 30°C or more, or 35°C or more higher. By setting the reaction temperature to be 10°C or more higher than the lower of the boiling point of the alkyl acetate (Y) and the boiling point of the alkyl alcohol (W) under the atmospheric pressure of the reaction environment, MAAc can be obtained efficiently in a short period of time with high purity and high yield. The specific lower limit of this reaction temperature varies depending on the type of alkyl acetate (Y) used and the atmospheric pressure of the reaction environment, but may be, for example, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or 105°C.

On the other hand, the upper limit of the reaction temperature is 150°C, preferably 140°C, more preferably 130°C, and sometimes even more preferably 120°C or 110°C. By setting the reaction temperature at or below the upper limit, distillation and polymerization of MALY(X) and MAAc(Z) can be suppressed, and the yield can be increased. The reaction temperature may be constant, or it does not have to be constant; for example, the temperature may be gradually increased.

The reaction temperature in the transesterification reaction is the temperature of the reaction liquid. When multiple types of alkyl acetate esters (Y) are used, the "boiling point of the alkyl acetate ester (Y)" is the lowest boiling point among the boiling points of the alkyl acetate esters (Y). Similarly, when multiple types of alkyl acetate esters (Y) are used to produce multiple types of alkyl alcohols, the "boiling point of the alkyl alcohol (W)" is the lowest boiling point among the boiling points of the alkyl alcohols (W).

The lower limit of the reaction time for the transesterification reaction is preferably 12 hours, more preferably 20 hours, from the viewpoint of increasing the yield. The upper limit of the reaction time is preferably 60 hours, more preferably 48 hours or 40 hours, from the viewpoint of efficiency, productivity, etc.

The transesterification reaction can be carried out without using a solvent, or may be carried out using a solvent. However, from the viewpoints of adjusting the reaction temperature and achieving high purity of the resulting MAAc, it is preferable to carry out the reaction without a solvent.

The transesterification reaction may be carried out under atmospheric pressure, or under pressure or reduced pressure. However, from the viewpoint of sufficiently increasing the reaction temperature, it is preferable to carry out the reaction under atmospheric pressure or pressure, and more preferably under pressure. The upper limit of the pressure (gauge pressure) when pressurizing is preferably 5 kPaG, and more preferably 3 kPG. The lower limit of the pressure (gauge pressure) when pressurizing can be, for example, 0.1 kPaG.

In the transesterification step, it is preferable to reuse at least a portion of the alkyl acetate (Y) removed from the system together with the alkyl alcohol (W) for the transesterification reaction in this step. When the alkyl alcohol (W) is removed by fractional distillation, a portion of the alkyl acetate (Y) having a boiling point close to that of the alkyl alcohol (W) is usually removed at the same time. Therefore, by reusing the distilled alkyl acetate (Y) as a raw material, the raw material can be used efficiently and waste can be reduced. When reusing the alkyl acetate (Y), a portion of the alkyl alcohol (W) distilled together with the alkyl acetate (Y) may be added again to the reaction system. However, from the viewpoint of reaction efficiency, it is preferable to add (reuse) the alkyl acetate (Y) to the reaction solution while excluding as much of the alkyl alcohol (W) as possible. The alkyl acetate (Y) used as a raw material may be a combination of the recycled one and other alkyl acetates.

The transesterification reaction process can be terminated by stopping the addition of the alkyl acetate (Y). It is preferable to continue to heat the product liquid (a solution containing the produced MAAc (Z), etc.) obtained through the reaction at a predetermined temperature to sufficiently distill off the alkyl alcohol (W) and alkyl acetate (Y). In this case, heating may be performed under reduced pressure. In this way, the alkyl alcohol (W) and alkyl acetate (Y) in the resulting product liquid can be sufficiently reduced, and high-purity MAAc can be obtained. After stopping the addition of the alkyl acetate (Y), in other words, after the process is completed, the molar ratio (Y/(X+Z)) may be less than 0.005.

The transesterification step is preferably carried out until the yield of MAAc(Z) is 95% or more, and even 96% or 97% or more. This production method allows the production of MAAc with such a high yield. The upper limit of this yield may be 100%, or from the viewpoint of production efficiency, it may be 99.9% or 99%.

It is also preferable to carry out the transesterification reaction until the molar ratio (Z/(X+Z)) of MAAc(Z) to the total amount of MALY(X) and MAAc(Z) in the reaction system (reaction liquid) is 0.95 or more, or even 0.96 or 0.97 or more. This also makes it possible to produce MAAc with a high yield. The upper limit of this molar ratio (Z/(X+Z)) may be 1, or from the viewpoint of production efficiency, etc., it may be 0.999 or 0.99.

(Other processes, etc.)
In the production method, it is preferable to include a step of purifying the product liquid obtained after the transesterification reaction step (purification step). By performing the purification, the purity of the obtained MAAc can be further increased. The purification of the product liquid (MAAc) can be effectively performed by distillation, particularly vacuum distillation.

The lower limit of the yield of MAAc in this production method is preferably 95%, and more preferably 96% or 97%. The upper limit of this yield may be 100%, or from the standpoint of production efficiency, etc., it may be 99.9% or 99%.

The lower limit of the purity of the obtained MAAc is preferably 90% by mass, more preferably 95%, 97% by mass, or 99% by mass. The upper limit of this purity may be 100% by mass or 99.9% by mass.

The content of chlorine compounds in the obtained MAAc is preferably 100 ppm or less, more preferably 10 ppm or less, and even more preferably 1 ppm or 0.1 ppm or less, calculated as chlorine atoms. The manufacturing method of the present invention does not use a compound containing chlorine element as a raw material, so that MAAc with an extremely low content of chlorine compounds can be obtained, which is industrially useful.

(Use, etc.)
The MAAc obtained by this production method can be used for various conventionally known applications. For example, 2-methylene-1,3-propanediol diacetate (MPDAc) can be obtained by reacting the obtained MAAc with acetic acid in the presence of a metal catalyst (platinum catalyst, gold catalyst, etc.) and in an oxygen atmosphere. MPDAc can be suitably used as a comonomer in the production of modified ethylene-vinyl ester copolymer (modified EVOH).

The method for producing modified EVOH preferably includes a step of obtaining MAAc by the above-mentioned method for producing MAAc, a step of obtaining MPDAc by using the above-mentioned MAAc as a raw material through a reaction using a metal catalyst, a step of copolymerizing ethylene, a vinyl ester, and the above-mentioned MPDAc, and a step of saponifying the obtained copolymer.

Such MPDAc-modified EVOH has the characteristic of having improved stretchability and shrinkability while maintaining good barrier properties compared to unmodified EVOH. Furthermore, according to the method for producing MPDAc and the method for producing modified EVOH using MAAc obtained by the method for producing MAAc of the present invention, the purity of the MAAc used is high, so that the metal catalyst is less likely to deteriorate during the synthesis of MPDAc, and the metal catalyst can be used for a long period of time.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

The compositions of the product liquid and distillate were analyzed by ¹ H-NMR (400 MHz, manufactured by JEOL Ltd.) and gas chromatography (GC).
The measurement conditions for ¹ H-NMR are as follows.
Measurement solvent: deuterated dimethyl sulfoxide Reference material: tetramethylsilane Measurement temperature: 25°C
The assignment of each compound is as follows:
β-Methallyl alcohol: 4.9 ppm (s, 1H), 4.8 ppm (t, 1H), 4.7 ppm (s, 1H), 3.8 ppm (d, 2H), 1.6 ppm (s, 3H),
β-Methallyl acetate: 4.9 ppm (d, 2H), 4.4 ppm (s, 2H), 2.1 (s, 3H), 1.7 (s, 3H),
Titanium tetrabutoxide: 3.4 ppm (t, 8H), 1.4 ppm (q, 8H), 1.3 ppm (q, 8H), 0.9 ppm (t, 12H),
Methyl acetate: 3.6 ppm (3H), 2.0 ppm (s, 3H),
Methanol: 3.2 ppm (d, 3H), 4.1 ppm (q, 1H),
Ethyl acetate: 4.0 ppm (q, 2H), 2.0 ppm (s, 3H), 1.2 ppm (t, 3H),
Ethanol: 4.4 ppm (t, 1H), 3.4 ppm (q, 2H), 1.1 ppm (t, 3H),
Dimethyl sulfoxide: 3.3 ppm (s, 6H),
Water: 2.5ppm (s, 2H),
Isopropyl acetate: 5.0 ppm (sep, 1H), 2.0 ppm (s, 3H), 1.2 ppm (d, 6H),
Isopropanol: 4.4 ppm (br, 1H), 3.8 ppm (sep, 1H), 1.0 ppm (d, 2H)
n-Propyl acetate: 4.0 ppm (t, 2H), 2.0 ppm (s, 3H), 1.7 ppm (sext, 2H), 1.0 ppm (t, 3H)
n-Propanol: 4.4 (t, 1H), 3.3 (q, 2H), 1.4 (quin, 2H), 0.8 (t, 3H)
Tertiary butyl acetate: 2.0 ppm (s, 3H), 1.4 ppm (s, 9H)
Tertiary butanol: 4.2 ppm (s, 1H), 1.1 ppm (s, 9H)
Normal butyl acetate: 4.0ppm (t, 2H), 2.0ppm (s, 3H), 1.5ppm (quin, 2H), 1.3ppm (sex, 2H), 0.9ppm (t, 3H)
Normal butanol: 4.3 ppm (t, 1H), 3.4 ppm (m, 2H), 1.5-1.2 ppm (m, 4H), 0.9 ppm (t, 3H)
Acetic anhydride: 2.2 ppm (s, 6H)
Acetic acid: 2.0 ppm (s, 3H)
The other peaks detected were classified as other unknown substances. For the other unknown substances, the total integral value detected in the range of 0 to 6 ppm other than the above assignments was calculated as the number of moles of compounds having a hydrogen atom of 6H.

[Example 1]
In a nitrogen atmosphere, 100 parts by mass (1.00 molar equivalent) of MALY, 20.5 parts by mass (0.20 molar equivalent) of methyl acetate, and 4.72 parts by mass (0.010 molar equivalent) of tetrabutoxytitanium were added to a reactive distillation apparatus equipped with a heat medium jacket and a stirrer, and the mixture was stirred. The reaction temperature (reaction liquid temperature) was heated to 97 ° C. by heating the heat medium jacket, and the transesterification reaction was carried out under atmospheric pressure and at a temperature of 40 to 65 ° C. at the top of the tower. From 1 hour after the start of the reaction, additional 5.1 parts by mass (0.05 molar equivalent) of methyl acetate was added every hour, and the reaction was carried out for a total of 32 hours. Methanol generated during the reaction was recovered as a distillate in a condenser cooled to 10 ° C. at the top of the tower. The composition of the product liquid obtained after 32 hours of reaction was as shown in Table 2. In addition, the maximum and minimum values of the molar ratio (Y / (X + Z)) in the reaction liquid during the reaction were as shown in Table 1. The maximum and minimum values were calculated from the compositions of the reaction solution at the time of charging and the product solution after the reaction, and from ^1H -NMR spectra measured by sampling very small amounts of the reaction solution every hour during the reaction (similar calculations were also performed in other Examples and Comparative Examples).
Thereafter, the addition of methyl acetate was stopped, and the mixture was stirred for another 3 hours under conditions of a reaction liquid temperature of 65-75°C and reduced pressure to 600 Torr using a steam ejector, and distillation was continued until no more methyl acetate or methanol distillate was produced. After removing the distillate from the receiving tank, the reaction tank was reduced in pressure to 200 Torr, and MAAc was extracted by distillation under reduced pressure. The yield of the distilled MAAc-containing liquid, the purity (GC) of MAAc, and the yield (yield after reduced pressure distillation x purity) were as shown in Table 2.
The total amount of methyl acetate (alkyl acetate ester (Y)) used, the total content of MALY (X) and MAAc (Z) in the distillate during the reaction, and the total mass of the raw materials used to produce 1 mole of MAAc (Z) are shown in Table 2.

[Example 2]
Except for extending the reaction time to 35 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 3]
Except for extending the reaction time to 38 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 4]
Except for changing the reaction liquid temperature to 101° C. under a pressure of 0.5 kPaG and the reaction time to a total of 30 hours, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 5]
Except for changing the reaction liquid temperature to 106° C. under a pressure of 1.8 kPaG and the reaction time to a total of 30 hours, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 6]
Except for changing the amount of tetrabutoxytitanium to 7.07 parts by mass (0.015 molar equivalent) and changing the reaction time to 28 hours in total, MAAc was synthesized in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 7]
Except for changing the reaction temperature (reaction solution temperature) to 90° C. and the reaction time to 38 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 8]
Except for changing the reaction temperature (reaction solution temperature) to 86° C. and the reaction time to 46 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Comparative Example 1]
Except for changing the reaction temperature (reaction solution temperature) to 65° C. and the reaction time to 60 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.
When the reaction temperature was low, the transesterification reaction rate was very slow, and it was not possible to efficiently obtain the target product with high purity and high yield.

[Example 9]
Except for changing the amount of methyl acetate charged to 44.1 parts by mass (0.43 molar equivalents), the reaction temperature (reaction liquid temperature) to 86° C., and the reaction time to 44 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Comparative Example 2]
Except for changing the amount of methyl acetate charged to 102.7 parts by mass (1.00 molar equivalent), the reaction temperature (reaction liquid temperature) to 75° C., and the reaction time to 60 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.
When the amount of methyl acetate charged and the amount of methyl acetate in the reaction solution during the reaction are large, the temperature of the reaction solution in the reflux state becomes low, and therefore the reaction temperature cannot be sufficiently increased under normal pressure, and the target product cannot be efficiently obtained with high purity and high yield.

[Example 10]
Except for changing the amount of methyl acetate charged to 15.4 parts by mass (0.15 molar equivalents), the reaction temperature (reaction liquid temperature) to 100° C., and the reaction time to 31 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 11]
Except for changing the amount of methyl acetate to 10.3 parts by mass (0.10 molar equivalent), the reaction temperature (reaction liquid temperature) to 104° C., and the reaction time to 29 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 12]
Except for changing the amount of methyl acetate charged to 5.14 parts by mass (0.05 molar equivalent), the reaction temperature (reaction liquid temperature) to 107° C., and the reaction time to 28 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 13]
Except for changing the amount of methyl acetate charged to 1.03 parts by mass (0.01 molar equivalent), the reaction temperature (reaction liquid temperature) to 108° C., and the reaction time to 25 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.

[Comparative Example 3]
Except for changing the amount of methyl acetate to 0.31 parts by mass (0.003 molar equivalent), the reaction temperature (reaction liquid temperature) to 108° C., and the reaction time to 25 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 1. The results of analysis, etc. are shown in Tables 1 and 2.
When the amount of methyl acetate charged and the amount of methyl acetate in the reaction solution during the reaction were small, some of the MALY (X: raw material) and MAAc (Z: product) in the distillate were easily distilled out together with methyl acetate and methanol, resulting in a decrease in yield.

[Example 14]
Under a nitrogen atmosphere, 100 parts by mass (1.00 molar equivalent) of MALY, 24.4 parts by mass (0.20 molar equivalent) of ethyl acetate, and 4.72 parts by mass (0.010 molar equivalent) of tetrabutoxytitanium were added to a reactive distillation apparatus equipped with a heat medium jacket and a stirrer, and the mixture was stirred. The reaction temperature (reaction liquid temperature) was heated to 100 ° C. by heating the heat medium jacket, and the transesterification reaction was carried out under atmospheric pressure and conditions where the temperature at the top of the tower was 40 to 75 ° C. Additional ethyl acetate was added at 6.1 parts by mass (0.05 molar equivalent) every hour from 1 hour after the start of the reaction, and the reaction was carried out for a total of 33 hours. Ethanol generated during the reaction was collected as a distillate in a condenser cooled to 10 ° C. at the top of the tower. The composition of the product liquid obtained after 33 hours of reaction was as shown in Table 1. In addition, the maximum and minimum values of the molar ratio (Y / (X + Z)) in the reaction liquid during the reaction were as shown in Table 1.
Thereafter, the addition of ethyl acetate was stopped, and the mixture was stirred for another 3 hours under conditions of a reaction liquid temperature of 75-85°C and reduced pressure to 600 Torr by a steam ejector, and distillation was continued until no more ethyl acetate or ethanol was distilled out. After removing the distillate from the receiving tank, the reaction tank was reduced in pressure to 200 Torr, and MAAc was extracted by distillation under reduced pressure. The yield of the distilled MAAc-containing liquid, the purity (GC) of MAAc, and the yield (yield after reduced pressure distillation x purity) were as shown in Table 2.
The total amount of ethyl acetate (acetic acid alkyl ester (Y)) used, the total content of MALY (X) and MAAc (Z) in the distillate during the reaction, and the total mass of the raw materials used to produce 1 mole of MAAc (Z) were as shown in Table 2.

[Example 15]
The synthesis of MAAc was carried out in the same manner as in Example 14, except that the amount of ethyl acetate charged was changed to 12.2 parts by mass (0.10 molar equivalent), the reaction temperature (reaction liquid temperature) was changed to 105° C., and the reaction time was changed to 35 hours in total. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 16]
Except for changing the amount of ethyl acetate to 6.1 parts by mass (0.05 molar equivalent), the reaction temperature (reaction solution temperature) to 108° C., and the reaction time to 25 hours in total, the synthesis of MAAc was carried out in the same manner as in Example 14. The results of analysis and the like are shown in Tables 1 and 2.

[Example 17]
The synthesis of MAAc was carried out in the same manner as in Example 14, except that the amount of ethyl acetate charged was changed to 52.5 parts by mass (0.43 molar equivalents), the reaction temperature (reaction liquid temperature) was changed to 95° C., and the reaction time was changed to a total of 37 hours. The results of analysis, etc. are shown in Tables 1 and 2.

[Comparative Example 4]
The synthesis of MAAc was carried out in the same manner as in Example 14, except that the amount of ethyl acetate charged was changed to 122.2 parts by mass (1.00 molar equivalent), the reaction temperature (reaction liquid temperature) was changed to 86° C., and the reaction time was changed to 50 hours in total. The results of analysis, etc. are shown in Tables 1 and 2.
When the amount of ethyl acetate charged and the amount of ethyl acetate in the reaction solution during the reaction were large, the reaction temperature (reaction solution temperature) in the reflux state became low, and the target compound could not be obtained efficiently.

[Example 18]
MAAc was synthesized in the same manner as in Example 14, except that the reaction liquid temperature was 104° C. under a pressure of 0.5 kPaG and the reaction time was changed to 28 hours in total. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 19]
MAAc was synthesized in the same manner as in Example 14, except that the reaction liquid temperature was 109° C. under a pressure of 1.5 kPaG and the reaction time was changed to 21 hours in total. The results of analysis, etc. are shown in Tables 1 and 2.

[Example 20]
Under a nitrogen atmosphere, 100 parts by mass (1.00 molar equivalent) of MALY, 28.3 parts by mass (0.20 molar equivalent) of isopropyl acetate, and 4.72 parts by mass (0.010 molar equivalent) of tetrabutoxytitanium were added to a reactive distillation apparatus equipped with a heat medium jacket and agitated. The reaction temperature (reaction liquid temperature) was heated to 105 ° C. by heating the heat medium jacket, and the transesterification reaction was carried out under conditions where the temperature at the top of the tower was 50 to 83 ° C. under atmospheric pressure. After 1 hour from the start of the reaction, additional isopropyl acetate was added at 7.1 parts by mass (0.05 molar equivalent) every hour, and the reaction was carried out for a total of 30 hours. Isopropanol generated during the reaction was recovered as a distillate in a condenser at the top of the tower, which was water-cooled to 10 ° C. The composition of the product liquid obtained after 30 hours of reaction was as shown in Table 2. The maximum and minimum values of the molar ratio (Y/(X+Z)) in the reaction solution during the reaction were as shown in Table 1.
Thereafter, the addition of isopropyl acetate was stopped, and stirring was continued for another 3 hours under conditions of a reaction liquid temperature of 75-85°C and reduced pressure to 600 Torr by a steam ejector, and distillation was continued until no more isopropyl acetate or isopropanol was distilled. After removing the distillate from the receiving tank, the reaction tank was reduced in pressure to 200 Torr, and MAAc was extracted by distillation under reduced pressure. The yield of the distilled MAAc-containing liquid, the purity (GC) of MAAc, and the yield (yield after reduced pressure distillation x purity) were as shown in Table 2.
The total amount of isopropyl acetate (alkyl acetate ester (Y)) used, the total content of MALY (X) and MAAc (Z) in the distillate during the reaction, and the total mass of the raw materials used to produce 1 mole of MAAc (Z) were as shown in Table 2.

[Example 21]
Under a nitrogen atmosphere, 100 parts by mass (1.00 molar equivalent) of MALY, 28.3 parts by mass (0.20 molar equivalent) of normal propyl acetate, and 4.72 parts by mass (0.010 molar equivalent) of tetrabutoxytitanium were added to a reactive distillation apparatus equipped with a heat medium jacket equipped with a stirrer, and stirred. The reaction temperature (reaction liquid temperature) was heated to 107 ° C. by heating the heat medium jacket, and the transesterification reaction was carried out under conditions where the temperature at the top of the tower was 60 to 97 ° C. under atmospheric pressure. After 1 hour from the start of the reaction, additional isopropyl acetate was added at 7.1 parts by mass (0.05 molar equivalent) every hour, and the reaction was carried out for a total of 32 hours. The normal propanol generated during the reaction was recovered as a distillate in a condenser cooled to 10 ° C. at the top of the tower. The composition of the product liquid obtained after 32 hours of reaction was as shown in Table 2. The maximum and minimum values of the molar ratio (Y/(X+Z)) in the reaction solution during the reaction were as shown in Table 1.
Thereafter, the addition of normal propyl acetate was stopped, and stirring was continued for another 3 hours under conditions of a reaction liquid temperature of 85 to 95°C and reduced pressure to 600 Torr by a steam ejector, and distillation was continued until no distillate of normal propyl acetate or normal propanol was produced. After removing the distillate from the receiving tank, the reaction tank was reduced in pressure to 200 Torr, and MAAc was taken out by distillation under reduced pressure. The yield of the distilled MAAc-containing liquid, the purity (GC) of MAAc, and the yield (yield after reduced pressure distillation x purity) were as shown in Table 2.
The total amount of n-propyl acetate (alkyl acetate (Y)) used, the total content of MALY (X) and MAAc (Z) in the distillate during the reaction, and the total mass of the raw materials used to produce 1 mole of MAAc (Z) were as shown in Table 2.

[Example 22]
In a nitrogen atmosphere, 100 parts by mass (1.00 molar equivalent) of MALY, 32.2 parts by mass (0.20 molar equivalent) of tertiary butyl acetate, and 4.72 parts by mass (0.010 molar equivalent) of tetrabutoxytitanium were added to a reactive distillation apparatus equipped with a heat medium jacket and agitated. The reaction temperature (reaction liquid temperature) was heated to 105 ° C. by heating the heat medium jacket, and the transesterification reaction was carried out under atmospheric pressure and conditions where the temperature at the top of the tower was 60 to 97 ° C. Additional tertiary butyl acetate was added at 8.1 parts by mass (0.05 molar equivalent) every hour from 1 hour after the start of the reaction, and the reaction was carried out for a total of 30 hours. Tertiary butanol generated during the reaction was recovered as a distillate in a condenser at the top of the tower, which was water-cooled to 10 ° C. The composition of the product liquid obtained after 30 hours of reaction was as shown in Table 2. The maximum and minimum values of the molar ratio (Y/(X+Z)) in the reaction solution during the reaction were as shown in Table 1.
Thereafter, the addition of tertiary butyl acetate was stopped, and stirring was continued for another 3 hours under conditions of a reaction liquid temperature of 85-95°C and reduced pressure to 600 Torr using a steam ejector, and distillation was continued until no more distillate of tertiary butyl acetate and tertiary butanol was produced. After removing the distillate from the receiving tank, the pressure in the reaction tank was reduced to 200 Torr, and MAAc was extracted by distillation under reduced pressure. The yield of the distilled MAAc-containing liquid, the purity (GC) of MAAc, and the yield (yield after reduced pressure distillation x purity) were as shown in Table 2.
The total amount of tert-butyl acetate (alkyl acetate ester (Y)) used, the contents of MALY (X) and MAAc (Z) in the distillate during the reaction, and the total mass of the raw materials used to produce 1 mole of MAAc (Z) are shown in Table 2.

[Comparative Example 5]
Under a nitrogen atmosphere, 100 parts by mass (1.00 molar equivalent) of MALY, 32.2 parts by mass (0.20 molar equivalent) of normal butyl acetate, and 4.72 parts by mass (0.010 molar equivalent) of tetrabutoxytitanium were added to a reactive distillation apparatus equipped with a heat medium jacket and a stirrer, and the mixture was stirred. The reaction temperature (reaction liquid temperature) was heated to 105 ° C. by heating the heat medium jacket, and a transesterification reaction was performed. After 1 hour from the start of the reaction, additional butyl acetate was added at 8.05 parts by mass (0.05 molar equivalent) every hour, and the reaction was performed for a total of 33 hours.
However, although the temperature at the top of the column was examined to be between 80 and 110°C in order to distill off the produced normal butanol, the raw material MALY was preferentially distilled off in the distillate over normal butanol, and therefore MAAc could not be sufficiently synthesized.

[Comparative Example 6]
Except for using 2.64 parts by mass (0.010 molar equivalent) of paratoluenesulfonic acid monohydrate as a catalyst instead of 4.72 parts by mass of tetrabutoxytitanium, MAAc was synthesized by transesterification in the same manner as in Example 1. The results of analysis, etc. are as shown in Tables 1 and 2.
When paratoluenesulfonic acid monohydrate was used as a catalyst, MAAc could not be obtained in high purity and high yield.

[Comparative Example 7]
Under a nitrogen atmosphere, 100 parts by mass (1.00 molar equivalent) of MALY and 141.6 parts by mass (1.00 molar equivalent) of acetic anhydride were added to a reactive distillation apparatus equipped with a stirrer and a cooling jacket, and the reaction solution was stirred and cooled to a reaction solution temperature of 0°C. Here, 1.69 parts by mass (0.010 molar equivalent) of N,N-dimethylaminopyridine was added and stirred. Subsequently, 140.3 parts by mass (1.00 molar equivalent) of triethylamine was added, and the reaction solution was stirred at a temperature of 0°C for 1 hour, after which the jacket temperature was raised to 25°C over 2 hours to carry out an esterification reaction.
100 parts by mass of 2N hydrochloric acid was added to the reaction solution obtained, and the mixture was stirred and allowed to stand, whereby the mixture was separated into an upper organic phase containing the target substance and a lower aqueous phase. After the aqueous phase was removed, the organic phase was washed with 100 parts by mass of a saturated aqueous sodium carbonate solution, and the aqueous phase was removed. The organic phase was then circulated through a dryer filled with molecular sieves, whereby the organic phase was dried to a moisture content of 10 ppm or less.
The yield of the obtained MAAc was 147.5 parts by mass, the purity (GC) was 97.0%, and the yield was 90.4%. Although the target product was obtained with high purity, the yield was low because the β-methallyl acetate was partially dissolved in the aqueous phase.

[Comparative Example 8]
Under a nitrogen atmosphere, 100 parts by mass (1.00 molar equivalent) of MALY and 141.6 parts by mass (1.00 molar equivalent) of acetic anhydride were added to a reactive distillation apparatus equipped with a stirrer and a cooling jacket, and the reaction solution was stirred and cooled to a reaction solution temperature of 0°C. Here, 1.69 parts by mass (0.010 molar equivalent) of N,N-dimethylaminopyridine was added and stirred. Subsequently, 140.3 parts by mass (1.00 molar equivalent) of triethylamine was added, and the reaction solution was stirred at a temperature of 0°C for 1 hour, after which the jacket temperature was raised to 25°C over 2 hours to carry out an esterification reaction.
The reaction liquid obtained was heated to a temperature of 75 to 85° C. using a heat medium jacket, the pressure in the reaction vessel was reduced to 200 Torr, and MAAc was extracted by vacuum distillation. The yield of the distilled MAAc-containing liquid, the purity (GC) of MAAc, and the yield (yield after vacuum distillation × purity) were as shown in Table 2.
The target product was obtained with a relatively high purity, but it contained 1.0 mass% triethylamine, and the yield was low. In addition, there was a problem of an unpleasant odor (obtained from triethylamine) different from that of MAAc obtained by ester exchange with acetate.

[Comparative Example 9]
The reaction was carried out under the same conditions as in Example 1, except that the amount of ethyl acetate charged was 244 parts by mass (2.00 molar equivalents) and ethyl acetate was not added thereafter. The reaction temperature (reaction liquid temperature) did not rise above 80°C at the beginning of the reaction, and after the start of distillation of ethanol, the reaction temperature rose as the amount of distillate increased, and 5 hours after the start of the reaction, the reaction liquid temperature reached 105°C. The yield of the solution containing MAAc taken out by reduced pressure distillation was 128.7 parts by mass. The purity of MAAc was 65.0% by mass. Compounds contained other than MAAc were 34.9% by mass of MALY and 0.1% by mass of ethyl acetate.
When ethyl acetate was added all at once at the start of the reaction, the reaction temperature could not be increased, so the reaction rate was slow, and furthermore, ethanol and ethyl acetate formed an azeotropic mixture and were distilled out of the system, so the transesterification reaction could not proceed sufficiently.

In addition, in Tables 1 and 2 above, "-" indicates that there is no corresponding data or that the data has not been obtained.

As shown in Tables 1 and 2, in each of the production methods of Examples 1 to 22, MAAc could be efficiently obtained with high purity and high yield. Table 2 also shows the results of evaluation of the total mass of raw materials used in the production of 1 mole of MAAc(Z) based on the following criteria. In the cases of Comparative Examples 7 and 8, in which acetic anhydride was used as the acetic acid source, the total mass of raw materials used in the production of 1 mole of MAAc(Z) would be 277 g if the yield was 100%.
A: Less than 250 g B: 250 g or more and less than 277 g C: 277 g or more In each of the production methods of Examples 1 to 22, the total mass of the raw materials can be reduced, and it can be said that it is excellent in terms of productivity, environmental load, etc.

Claims (5)

the step of carrying out an ester exchange reaction between β-methallyl alcohol (X) and an alkyl acetate (Y) in the presence of a neutral catalyst while adding the alkyl acetate (Y) to the reaction system and removing the alkyl alcohol (W) produced therefrom to the outside of the system so that the molar ratio (Y/(X+Z)) of the alkyl acetate (Y) to the total amount of β-methallyl alcohol (X) and the product β-methallyl acetate (Z) in the reaction system is maintained within a range of 0.005 to 0.5;
the alkyl acetate (Y) is at least one selected from the group consisting of methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, and tert-butyl acetate;
The reaction temperature in the above step is at least 10°C higher than the lower of the boiling point of the alkyl acetate (Y) and the boiling point of the alkyl alcohol (W) at the atmospheric pressure of the reaction environment and is not higher than 150°C. The method for producing β-methallyl acetate according to claim 1, wherein the alkyl acetate ester (Y) is methyl acetate. The method for producing β-methallyl acetate according to claim 1, wherein the alkyl acetate ester (Y) is ethyl acetate. The method for producing β-methallyl acetate according to any one of claims 1 to 3, wherein at least a portion of the alkyl acetate ester (Y) removed from the system together with the alkyl alcohol (W) in the above step is reused for the transesterification reaction in the above step. The method for producing β-methallyl acetate according to any one of claims 1 to 4, wherein the above steps are carried out until the yield of β-methallyl acetate (Z) is 95% or more.

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