Method for producing (METH)acrylate

Abstract

To provide a method for producing (meth)acrylate that can produce (meth)acrylate in high yield without using raw ester in large excess.SOLUTION: A method for producing (meth)acrylate includes causing a transesterification to occur, in the presence of a zinc catalyst, between a compound represented by general formula (1) and an alcohol to produce (meth)acrylate. While removing the by-product alcohol from the transesterification through adsorption onto an adsorbent, the target (meth)acrylate is produced. CH2=CR1-COOR2 (1) (In general formula (1), R1 is a hydrogen atom or a methyl group, and R2 is a methyl group or an ethyl group.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a (meth)acrylic acid ester. [Background technology]

[0002] (Meth)acrylic acid esters, consisting of a (meth)acrylic acid moiety with a carbon-carbon double bond and an alcohol moiety that imparts functionality to the (meth)acrylic acid ester, are used in a wide range of applications. The (meth)acrylic acid moiety polymerizes with heat, light, peroxide, etc. to form a polymer backbone. By using a functional alcohol, the polymerized polymer can be endowed with properties such as water resistance, flexibility, heat resistance, weather resistance, low shrinkage, high refractive index, water solubility, curability, adhesion, low surface tension, water and oil repellency, and high hardness. Therefore, methods for bonding (meth)acrylic acid moieties and alcohol moieties, i.e., for producing (meth)acrylic acid esters, are extremely important.

[0003] A known method for producing a (meth)acrylic acid ester involves transesterifying methyl acrylate with an alcohol corresponding to the target (meth)acrylic acid ester (hereinafter also referred to as "raw material alcohol") in the presence of a catalyst such as an organometallic compound, and then removing the by-product methanol (see, for example, Non-Patent Document 1). The transesterification reaction is an equilibrium reaction, and by distilling off the by-product alcohol (hereinafter also referred to as "by-product alcohol") from the reaction system, the reaction is biased toward the product system, thereby increasing the yield. Therefore, the temperature of the transesterification reaction is set according to the boiling point of the by-product alcohol, and the transesterification reaction is carried out while vaporizing and removing the by-product alcohol. For example, when methanol is produced as a by-product, the transesterification reaction can be carried out at a temperature of about 80°C. The lower the temperature of the transesterification reaction, the better the color tone of the target (meth)acrylic acid ester tends to be. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Xue Zhao and 4 others, “Chemical Science”, 2023, Volume 14, p.566-572 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the transesterification reaction, in order to bias the reaction toward the product system, in addition to distilling off the by-product alcohol, a (meth)acrylic acid ester such as methyl acrylate (hereinafter also referred to as "raw material ester") used as a raw material is used in a large excess amount greater than the required amount, and therefore, the production efficiency is not necessarily high. Furthermore, when methyl acrylate is used as the raw material ester, the boiling points of the by-product methanol and methyl acrylate are close to each other and are highly compatible with each other. Therefore, if methyl acrylate is used in large excess, it becomes difficult to separate the methanol, making it impossible to sufficiently remove the methanol. As a result, the transesterification reaction is unlikely to be biased toward the product system, and a sufficient yield is not necessarily obtained. Furthermore, if the raw material ester is used in large excess, a large amount of unreacted raw material ester will remain, and it will be troublesome to remove the unreacted raw material ester.

[0006] The present invention provides a method for producing a (meth)acrylic acid ester, which can produce a (meth)acrylic acid ester in high yield without using a large excess of the raw material ester. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A method for producing a (meth)acrylic acid ester by transesterification of a compound represented by the following general formula (1) with an alcohol in the presence of a zinc catalyst, The method for producing a (meth)acrylic acid ester includes producing a target (meth)acrylic acid ester while removing the alcohol by-produced in the transesterification reaction by adsorption onto an adsorbent. CH2=CR1 -COOR 2 ···(1) (In general formula (1), R 1 is a hydrogen atom or a methyl group, and R 2 is a methyl group or an ethyl group. [2] The method for producing a (meth)acrylic acid ester according to [1] above, wherein the adsorbent is a synthetic zeolite. [3] The method for producing a (meth)acrylic acid ester according to [1] or [2] above, wherein the transesterification reaction is carried out in the presence of hexane. [4] The method for producing a (meth)acrylic acid ester according to any one of [1] to [3] above, wherein the transesterification reaction is carried out in the presence of a polymerization inhibitor. [5] The method for producing a (meth)acrylic acid ester according to [4] above, wherein the polymerization inhibitor is 2,2,6,6-tetramethylpiperidine-1-oxyl. [6] The method for producing a (meth)acrylic acid ester according to [5] above, wherein the amount of the 2,2,6,6-tetramethylpiperidine-1-oxyl used is 0.05 to 0.5 moles per mole of the alcohol. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for producing a (meth)acrylic acid ester, which can produce a (meth)acrylic acid ester in high yield without using a large excess of the raw material ester. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a (meth)acrylic acid ester production apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes in detail the forms for implementing the present invention, but the present invention is not limited to the embodiments described below, and various modifications are possible without departing from the gist of the present invention. In the present invention, "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. In the present invention, a numerical range expressed by "to" means a numerical range that includes the numerical values ​​before and after "to" as the lower and upper limits. For example, A to B is synonymous with A or more and B or less. In addition, the drawings used in the following explanation may show characteristic parts enlarged for convenience in order to make the features easier to understand, and the dimensional ratios of each component may differ from the actual ones.

[0011] A method for producing a (meth)acrylic acid ester according to one embodiment of the present invention is a method for producing a (meth)acrylic acid ester as a target product (reaction product) by subjecting a raw material ester and a raw material alcohol shown below to a transesterification reaction in the presence of a zinc catalyst. In this embodiment, it is preferable to carry out the transesterification reaction in the presence of at least one of an azeotropic solvent that forms an azeotropic composition with the alcohol by-produced by the transesterification reaction (hereinafter also referred to as "by-produced alcohol") and a polymerization inhibitor. That is, it is preferable to carry out the transesterification reaction in a state where at least one of an azeotropic solvent and a polymerization inhibitor is present in the reaction system in addition to the zinc catalyst, raw material ester, and raw material alcohol, and it is more preferable to carry out the transesterification reaction in the presence of both the azeotropic solvent and the polymerization inhibitor. The transesterification reaction may also be carried out in the presence of a catalyst activator. Here, the term "reaction system" refers to a set of chemical substances (components) involved in the transesterification reaction.

[0012] <Zinc catalyst> The zinc catalyst is not particularly limited as long as it is a compound containing zinc and having catalytic function, and examples thereof include the zinc compound represented by the following general formula (2) (hereinafter simply referred to as "compound (2)"). Zn p (OCOR 3 ) q M r ···(2) (In general formula (2), R 3is an alkyl group, an alkenyl group, an aryl group, or a cycloalkyl group, M is an oxygen atom, a sulfur atom, or a selenium atom, p is the number 1 or 4, q is the number 2 or 6, and r is the number 0 or 1, provided that when p is 1, q is 2 and r is 0, and when p is 4, q is 6 and r is 1.

[0013] R 3 The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 6 carbon atoms. R 3 The alkenyl group in the formula (I) preferably has 2 to 20 carbon atoms, more preferably 2 to 10 carbon atoms, and even more preferably 1 to 6 carbon atoms. R 3 The aryl group in the formula (I) preferably has 6 to 24 carbon atoms, and more preferably 6 to 12 carbon atoms. R 3 The cycloalkyl group preferably has 5 to 20 carbon atoms, more preferably 5 to 16 carbon atoms, and even more preferably 5 to 12 carbon atoms. R 3 The alkyl group and alkenyl group in each of the above may be linear or branched. R 3 In the alkyl group, alkenyl group, aryl group, and cycloalkyl group, one or more hydrogen atoms bonded to the carbon atom may be substituted with a halogen atom. Examples of halogen atoms include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a fluorine atom is preferred. R 3 As the alkyl group, an alkyl group or an aryl group is preferred, and an alkyl group is more preferred. Examples of the alkyl group include unsubstituted alkyl groups such as a methyl group, an ethyl group, and a propyl group; and perfluoroalkyl groups such as a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, and a heptafluoroisopropyl group. Among these, a trifluoromethyl group is particularly preferred. If q is 2, then two R 3 may be the same or different. If q is 6, then 6 R 3may be the same or different.

[0014] Specific examples of compound (2) include zinc bis(alkylate) zinc such as zinc acetate, zinc acetate dihydrate, and zinc propionate; zinc bis(perfluoroalkyl acid) zinc such as zinc trifluoroacetate, zinc trifluoroacetate hydrate, zinc bis(pentafluoropropionate), zinc bis(heptafluorobutanate), and zinc bis(heptafluoroisobutyrate); tetranuclear zinc oxo(hexa(alkyl acid)) such as tetrazinc oxo(hexa(acetate)) and tetrazinc oxo(hexa(propionate)); tetranuclear zinc oxo(hexa(perfluoroalkyl acid)) such as tetrazinc oxo(hexa(trifluoroacetate)), tetrazinc oxo(hexa(pentafluoropropionate)), tetrazinc oxo(hexa(heptafluorobutanate)), and tetrazinc oxo(hexa(heptafluoroisobutyrate)). Among these, zinc bis(perfluoroalkyl acid)s such as zinc trifluoroacetate, zinc bis(pentafluoropropionate), and zinc bis(heptafluorobutanate); tetranuclear zinc oxo(hexa(alkyl acid))s such as tetrazinc oxo(hexa(acetate)) and tetrazinc oxo(hexa(propionate)); and tetranuclear zinc oxo(hexa(perfluoroalkyl acid))s such as tetrazinc oxo(hexa(trifluoroacetate)) and tetrazinc oxo(hexa(pentafluoropropionate)). The zinc catalyst may be used alone or in combination of two or more kinds.

[0015] <Raw material ester> The raw material ester is a (meth)acrylic acid ester that serves as a raw material for the target (meth)acrylic acid ester. In this embodiment, a compound represented by the following general formula (1) (hereinafter also referred to as "compound (1)") is used as the raw material ester. CH2=CR 1 -COOR 2 ···(1) (In general formula (1), R 1 is a hydrogen atom or a methyl group, and R 2is a methyl group or an ethyl group.

[0016] Compound (1) is methyl (meth)acrylate or ethyl (meth)acrylate, with methyl (meth)acrylate being preferred and methyl acrylate being more preferred.

[0017] <Raw alcohol> The raw material alcohol is an alcohol that serves as a raw material for the target (meth)acrylic acid ester. The raw material alcohol is not particularly limited as long as it is an alcohol corresponding to the target (meth)acrylic acid ester, and examples thereof include alcohols having 3 to 20 carbon atoms. From the viewpoint of activity of the transesterification reaction, the number of carbon atoms of the alcohol is preferably 3 to 16, and more preferably 3 to 12. The raw material alcohol may be any of monohydric alcohol, dihydric alcohol, and trihydric or higher alcohol, but from the viewpoint of activity in the transesterification reaction, monohydric alcohol is preferred. The raw material alcohol may be any of primary alcohol, secondary alcohol, and tertiary alcohol, but from the viewpoint of activity in the transesterification reaction, primary alcohol is preferred. The raw material alcohol may have an ether bond in the molecule.

[0018] Specific examples of the raw material alcohol include n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, 2-ethylhexanol, lauryl alcohol, stearyl alcohol, tridecanol, N,N-dimethylaminoethanol, N,N-diethylaminoethanol, cyclohexanol, 3,3,5-trimethylcyclohexanol, 4-t-butylcyclohexanol, benzyl alcohol, 1-phenylethyl alcohol, 2-phenylethyl alcohol, phenoxyethanol, methoxyethanol, ethoxyethanol, butoxyethanol, allyl alcohol, methallyl alcohol, and 2,5,8,11-tetraoxatridecan-13-ol. The raw material alcohol may be used alone or in combination of two or more kinds.

[0019] <Azeotropic solvent> An azeotropic solvent is a solvent that forms an azeotropic composition with the by-produced alcohol. By carrying out the transesterification reaction in the presence of an azeotropic solvent, the by-produced alcohol can be vaporized at a temperature lower than its boiling point, and the transesterification reaction temperature can be set lower than when an azeotropic solvent is not used in combination. The azeotropic solvent is not particularly limited as long as it can form an azeotropic composition with the by-produced alcohol, and examples thereof include organic solvents having a boiling point of 40 to 120° C. The boiling point of the azeotropic solvent is more preferably 40 to 100° C., further preferably 40 to 90° C., and particularly preferably 45 to 80° C. These boiling points are values ​​under atmospheric pressure (1013 hPa).

[0020] Specific examples of the azeotropic solvent include hydrocarbon solvents such as hexane, heptane, octane, cyclohexane, benzene, toluene, etc. Among these, hexane, heptane, and cyclohexane are preferred, and hexane is more preferred, from the viewpoint of having a low boiling point and being able to set the temperature of the transesterification reaction lower. The azeotropic solvent may be used alone or in combination of two or more kinds.

[0021] <Polymerization inhibitor> By carrying out the transesterification reaction in the presence of a polymerization inhibitor, it is possible to inhibit the polymerization of the raw material ester and the target (meth)acrylic acid ester. Examples of the polymerization inhibitor include 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), hydroquinone, hydroquinone monomethyl ether, dibutylhydroxytoluene (BHT), etc. Among these, TEMPO is preferred because it can more effectively inhibit polymerization even when the concentration of the raw material ester is high. The polymerization inhibitor may be used alone or in combination of two or more kinds.

[0022] <Catalyst activator> Conducting the transesterification reaction in the presence of a catalyst activator increases the activity of the zinc catalyst. Examples of catalyst activators include 4-dimethylaminopyridine, N-methylimidazole, 1,3-bis(imidazol-1-yl)methyl)-5-(pentoxy)benzene, etc. Among these, 4-dimethylaminopyridine is preferred. The catalyst activators may be used alone or in combination of two or more.

[0023] <Transesterification reaction> The transesterification reaction is carried out by reacting the compound (1) as a raw material ester with a raw material alcohol in the presence of a zinc catalyst. The ratio of compound (1) to the starting alcohol in the transesterification reaction is not particularly limited, but for example, the amount of compound (1) is preferably 1 to 5 moles, more preferably 1.1 to 4 moles, and even more preferably 1.2 to 3 moles, per mole of starting alcohol. When the ratio of compound (1) is equal to or greater than the above-mentioned lower limit, the transesterification reaction proceeds sufficiently. When the ratio of compound (1) is equal to or less than the above-mentioned upper limit, compound (1) is unlikely to be in excessive excess, resulting in high production efficiency. In addition, the amount of unreacted compound (1) can be reduced.

[0024] The amount of zinc catalyst used in the transesterification reaction is not particularly limited, but is preferably 0.001 to 0.5 moles, more preferably 0.005 to 0.2 moles, and even more preferably 0.01 to 0.1 moles, calculated as zinc per mole of compound (1). When the amount of zinc catalyst used is equal to or greater than the lower limit, the transesterification reaction proceeds sufficiently. When the amount of zinc catalyst used is equal to or less than the upper limit, the catalyst can be easily separated and is also economically advantageous.

[0025] When an azeotropic solvent is present in the reaction system, the volume ratio of compound (1) to azeotropic solvent in the reaction system is preferably 0.1 to 5.0, more preferably 0.3 to 3.0, even more preferably 0.5 to 2.0, even more preferably 0.7 to 1.5, particularly preferably 0.8 to 1.2, and most preferably 1.0. If the volume ratio is equal to or greater than the lower limit, the azeotropic solvent and the starting alcohol are less likely to separate, the reaction system is less likely to become a two-phase system, and the transesterification reaction is more likely to proceed. If the volume ratio is equal to or less than the upper limit, a decrease in the azeotropic efficiency with the by-product alcohol can be suppressed, allowing the target (meth)acrylic acid ester to be produced in a higher yield. In addition, the progress of polymerization of compound (1) can be suppressed.

[0026] When TEMPO is present in the reaction system, the amount of TEMPO used is preferably 0.05 to 0.5 mol, more preferably 0.07 to 0.4 mol, and even more preferably 0.09 to 0.3 mol per mol of the raw material alcohol. When the amount of TEMPO used is equal to or greater than the above-mentioned lower limit, polymerization of the raw material ester and the target (meth)acrylic acid ester can be sufficiently suppressed. When the amount of TEMPO used is equal to or less than the above-mentioned upper limit, the reaction is not inhibited and it is economically advantageous.

[0027] When a catalytic activator is present in the reaction system, the amount of the catalytic activator used is preferably 1.5 to 2.5 moles, more preferably 1.7 to 2.3 moles, and even more preferably 1.8 to 2.2 moles, per mole of zinc of the zinc catalyst. When the amount of the catalytic activator used is equal to or greater than the lower limit, the zinc catalyst can be sufficiently activated. When the amount of the catalytic activator used is equal to or less than the upper limit, the reaction is not inhibited and it is economically advantageous.

[0028] The transesterification reaction between the raw material ester and the raw material alcohol produces the desired (meth)acrylic acid ester, and also produces alcohol as a by-product. The alcohol produced as a by-product in the transesterification reaction (by-product alcohol) is methanol when methyl (meth)acrylate is used as the raw material ester, and is ethanol when ethyl (meth)acrylate is used. The reaction temperature in the transesterification reaction may be determined depending on the reaction selectivity, the polymerization stability of the raw material ester and the target (meth)acrylic acid ester, the boiling point of the by-produced alcohol, etc., and is, for example, preferably 60 to 95°C, more preferably 65 to 90°C. The reaction time for the transesterification reaction is not particularly limited, but is preferably 0.1 to 15 hours, more preferably 0.2 to 10 hours, for example. The reaction pressure in the transesterification reaction may be any of reduced pressure, normal pressure, and increased pressure. The reaction method for the transesterification reaction is not particularly limited, and for example, a batch method, a semi-batch method, a continuous method, etc. can be used.

[0029] In this embodiment, the transesterification reaction is carried out while the by-produced alcohol is adsorbed onto an adsorbent and removed from the reaction system, thereby producing the target (meth)acrylic acid ester. The adsorbent is not particularly limited as long as it adsorbs the by-produced alcohol and does not easily adsorb the raw material ester, raw material alcohol, and azeotropic solvent, and examples thereof include synthetic zeolite, natural zeolite, artificial zeolite, metal-organic framework (MOF), porous coordination polymer (PCP), activated carbon, silica, etc. Among these, synthetic zeolite is preferred. The adsorbent may be used alone or in combination of two or more kinds.

[0030] As the synthetic zeolite, synthetic zeolite 3A, synthetic zeolite 4A, and synthetic zeolite 5A are preferred, synthetic zeolite 3A and synthetic zeolite 4A are more preferred, and synthetic zeolite 4A is even more preferred. In this specification, synthetic zeolite 3A refers to a synthetic zeolite with pores having a diameter of 0.30 nm, which allows molecules with an effective diameter of up to 0.3 nm to pass through. In this specification, synthetic zeolite 4A refers to a synthetic zeolite with pores having a diameter of 0.40 nm, which allows molecules with an effective diameter of up to 0.4 nm to pass through. In this specification, synthetic zeolite 5A is a synthetic zeolite with pores having a diameter of 0.50 nm, while synthetic zeolite 4A allows molecules with an effective diameter of up to 0.5 nm to pass through. Examples of synthetic zeolites include A-type synthetic zeolites designated as 3A, 4A, or 5A. Commercially available products include Molecular Sieve 3A, Molecular Sieve 4A, and Molecular Sieve 5A (all trade names manufactured by Nacalai Tesque, Inc.).

[0031] The method for adsorbing the by-product alcohol onto the adsorbent is not particularly limited, and the by-product alcohol may be adsorbed onto the adsorbent in the reaction system, or the by-product alcohol may be adsorbed onto the adsorbent outside the reaction system. However, from the viewpoint of adsorption efficiency and the like, it is preferable to adsorb the by-product alcohol onto the adsorbent outside the reaction system. As a method for adsorbing the by-product alcohol onto an adsorbent outside the reaction system, a method in which the by-product alcohol released from the reaction system by vaporization is cooled and then adsorbed onto an adsorbent can be exemplified. Specifically, a method in which the vaporized by-product alcohol is cooled using a Dean-Stark apparatus and the liquefied by-product alcohol is adsorbed onto an adsorbent can be exemplified. Here, one embodiment of a method for adsorbing a by-produced alcohol onto an adsorbent will be described with reference to FIG.

[0032] FIG. 1 is a schematic diagram showing an example of a (meth)acrylic acid ester production apparatus. The (meth)acrylic acid ester production apparatus 1 shown in FIG. 1 includes a reactor 10, a Dean-Stark apparatus 20, a cooling pipe 30, and a thermometer 40.

[0033] A known apparatus can be used as the Dean-Stark apparatus 20. The Dean-Stark apparatus 20 in this example is H-shaped and includes a fractionating column 21, a straight pipe 22 serving as a liquid reservoir, and a cock 23 attached to the straight pipe 22. The fractionating column 21 and the straight column 22 are connected by a connecting column 24. The connecting column 24 is inclined so that the straight column 22 side is higher than the fractionating column 21 side. The reactor 10 is attached to the bottom of the fractionating column 21, and the thermometer 40 is attached to the top. A cooling pipe 30 is attached to the upper part of the straight pipe 22 . The straight pipe 22 is filled with adsorbent A. The amount of adsorbent A filled is not particularly limited, but it is preferable to fill the straight pipe 22 with adsorbent A up to the part where the straight pipe 22 joins with the connecting pipe 24 and so that the adsorbent A does not flow out into the connecting pipe 24. Alternatively, the adsorbent A may be filled in an amount that is, for example, about 10 times the theoretical production amount (by-product amount) of the by-product alcohol.

[0034] In a method for producing a (meth)acrylic acid ester using the (meth)acrylic acid ester production apparatus 1, a zinc catalyst is introduced into the reactor 10, and with the stopcock 23 of the straight pipe 22 of the Dean-Stark apparatus 20 closed, the straight pipe 22 is filled with an adsorbent A. If necessary, the atmosphere inside the apparatus is purged with an inert gas such as argon gas, and then the raw material ester and raw material alcohol, and if necessary, at least one of an azeotropic solvent, a polymerization inhibitor, and a catalyst activator, are introduced into the reactor 10. It is also preferable to fill the portion of the straight pipe 22 filled with adsorbent A with an azeotropic solvent. The azeotropic solvent introduced into the reactor 10 and the azeotropic solvent introduced into the straight pipe 22 may be the same or different types, but they are preferably the same type, and more preferably hexane.

[0035] Next, the reactor 10 is heated to initiate the transesterification reaction. When the transesterification reaction starts, the target (meth)acrylic acid ester and by-product alcohol are produced. The by-product alcohol is vaporized by heating and passes through the fractionating column 21, the connecting tube 24, and the straight tube 22 to reach the cooling tube 30. The gaseous by-product alcohol that has reached the cooling tube 30 is cooled and condensed in the cooling tube 30, becoming a liquid that falls into the straight tube 22. At this time, if the boiling point of the raw material ester is lower than the reaction temperature, part of the unreacted raw material ester also vaporizes, is cooled in the cooling pipe 30 and condenses, and falls into the straight pipe 22 as a liquid. Furthermore, if the boiling point of the raw material alcohol is lower than the reaction temperature, part of the unreacted raw material alcohol also vaporizes, is cooled in the cooling pipe 30 and condenses, and falls into the straight pipe 22 as a liquid. Furthermore, when the transesterification reaction is carried out in the presence of an azeotropic solvent, part of the azeotropic solvent also vaporizes, is cooled in the cooling pipe 30 and condenses, and falls into the straight pipe 22 as a liquid.

[0036] The liquid by-product alcohol that falls into the straight pipe 22 is adsorbed by the adsorbent A filled in the straight pipe 22 . On the other hand, the raw material ester, raw material alcohol and azeotropic solvent are hardly adsorbed by the adsorbent A even if they fall into the straight pipe 22, and are returned to the reactor 10 through the connecting pipe 24. In this way, the by-produced alcohol can be efficiently removed from the reaction system.

[0037] When the by-produced alcohol is adsorbed onto an adsorbent in the reaction system, the adsorbent may be placed in the reactor 10 in advance, and the transesterification reaction may be carried out in the presence of the adsorbent.

[0038] <Action and effect> According to the method for producing a (meth)acrylic acid ester of the present invention described above, the by-product alcohol is removed from the reaction system by adsorbing it onto an adsorbent, making it easy to remove the by-product alcohol. Furthermore, the transesterification reaction tends to proceed biasedly toward the product system even without a large excess of the raw material ester. Therefore, there is no need to use a large excess of the raw material ester, resulting in excellent production efficiency. Furthermore, the (meth)acrylic acid ester can be produced in high yield and in a short time. In other words, the method for producing a (meth)acrylic acid ester of the present invention can be said to be a highly active method for producing a (meth)acrylic acid ester. Furthermore, since there is no need to use a large excess of the raw material ester, it is easy to remove the unreacted raw material ester. [Example]

[0039] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the examples described below, and various modifications are possible without departing from the gist of the present invention.

[0040] [raw materials] Synthetic zeolite 4A: Manufactured by Nakarai Tesque, Inc., product name "Molecular Sieve 4A." Methyl acrylate: Manufactured by Tokyo Chemical Industry Co., Ltd. 4-Dimethylaminopyridine: manufactured by Angene International. 2,5,8,11-tetraoxatridecan-13-ol: manufactured by Angene International. Hexane: Manufactured by Kanto Chemical Co., Ltd. · TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl): manufactured by Oakwood Chemical Company. Zinc oxide: Manufactured by Nacalai Tesque, Inc. Trifluoroacetic acid: manufactured by Oakwood Chemical Company. Nonadecane: Manufactured by Tokyo Chemical Industry Co., Ltd. ZnTAC24 (registered trademark) (oxo(hexa(trifluoroacetato))tetrazinc and its trifluoroacetic acid adduct (containing ≦7% by mass of toluene)): manufactured by Takasago International Corporation.

[0041] [Synthesis example] <Synthesis of zinc trifluoroacetate> A stir bar and 9.12 g (4 equivalents) of trifluoroacetic acid were placed in a 50 mL recovery flask. The flask was cooled in an ice-water bath, and 1.63 g (20 mmol) of zinc oxide was added little by little with stirring. After the addition was complete, the ice bath was removed, and the mixture was gradually heated to 25°C and stirred at 25°C for 8 hours. The reaction mixture was dried in vacuo to obtain 5.80 g of zinc trifluoroacetate (yield 99.7%).

[0042] [Example 1] Using the (meth)acrylic acid ester production apparatus 1 shown in FIG. 1, a (meth)acrylic acid ester was produced as follows. A 50 mL flask was used as the reactor 10, and 255 mg of zinc trifluoroacetate (5 mol % in terms of zinc) was placed therein as a zinc catalyst. Furthermore, with the cock 23 of the straight pipe 22 of the Dean-Stark apparatus 20, to which a cooling pipe 30 and a thermometer 40 were attached, closed, 8.7 g of synthetic zeolite 4A as adsorbent A was packed into the straight pipe 22 up to the point where the straight pipe 22 merged with the connecting pipe 24, so that the adsorbent A did not flow out into the connecting pipe 24. After reducing the pressure inside the (meth)acrylic acid ester production apparatus 1 with a vacuum pump, the reactor 10 was heated for about 2 minutes with a heat gun in order to thoroughly dry the zinc catalyst. Next, reactor 10 was cooled, and the atmosphere inside (meth)acrylic acid ester production apparatus 1 was replaced with argon gas. Then, 428 mg (20 mol%) of 4-dimethylaminopyridine, 5.47 mg (0.2 mol%) of TEMPO as a polymerization inhibitor, 3.01 g (35 mmol) of methyl acrylate as a raw material ester, 3.64 g (17.5 mmol) of 2,5,8,11-tetraoxatridecan-13-ol as a raw material alcohol, and 3.2 mL of hexane as an azeotropic solvent (corresponding to a volume ratio of methyl acrylate / azeotropic solvent = 1.0) were charged into reactor 10. In addition, the portion of straight tube 22 packed with adsorbent A was filled with hexane. Next, the reactor 10 was heated using an oil bath at 80° C. while stirring for 6 hours to carry out an ester exchange reaction, thereby obtaining the target product, an acrylic acid ester of 2,5,8,11-tetraoxatridecan-13-ol. Methanol, which was a by-product alcohol produced by the transesterification reaction, hexane, and a portion of the unreacted methyl acrylate vaporized, were cooled and condensed in the cooling pipe 30, and turned into a liquid, which fell into the straight pipe 22. The methanol that fell into the straight pipe 22 was adsorbed by the adsorbent A packed in the straight pipe 22. On the other hand, the methyl acrylate and hexane that fell into the straight pipe 22 passed through the connecting pipe 24 and were returned to the reactor 10.

[0043] The target product was analyzed using a 500MHz Avance III analyzer manufactured by Bruker. 1The yield was calculated by the area ratio of 1H-NMR and gas chromatography (GC) measurement (internal standard method using nonadecane as an internal standard substance) under the following conditions, and the yield was 94%.

[0044] <GC measurement conditions> · Gas chromatograph: manufactured by Shimadzu Corporation, model "GC-2014". · Column: manufactured by Agilent J&W, product name "GC Column DB-5" (30.0 m, inner diameter 0.25 mm ID). · Column oven temperature: held at 60 °C for 3 minutes, then heated to 250 °C at a rate of 20 °C / min and held at 250 °C for 2 minutes. Injection temperature (270 °C), detector temperature (270 °C). · Column flow rate: helium (1.99 mL / min). · Analysis time: 14.5 minutes. · Detection: FID detector. · Sample injection volume: 1 μL.

[0045] [Example 2] Using the (meth)acrylic acid ester production apparatus 1 shown in Fig. 1, the (meth)acrylic acid ester was produced as follows. Into a 50 mL flask as the reactor 1, 344 mg of ZnTAC24 (registered trademark) (5 mol% in terms of zinc) was charged. Also, with the cock 23 of the straight tube 22 of the Dean-Stark apparatus 20 equipped with a cooling tube 30 and a thermometer 40 closed, 8.7 g of synthetic zeolite 4A as adsorbent A was filled into the straight tube 22 up to the part where it merges with the connecting tube 24 of the straight tube 22 and so that the adsorbent A does not flow out into the connecting tube 24. After evacuating the inside of the (meth)acrylic acid ester production apparatus 1 with a vacuum pump, it was heated for about 2 minutes using a heat gun to thoroughly dry the zinc catalyst. Next, reactor 10 was cooled, and the atmosphere inside (meth)acrylic acid ester production apparatus 1 was replaced with argon gas. Then, 611 mg (20 mol%) of 4-dimethylaminopyridine, 7.8 mg (0.2 mol%) of TEMPO as a polymerization inhibitor, 4.30 g (50 mmol) of methyl acrylate as a raw material ester, 5.21 g (25.0 mmol) of 2,5,8,11-tetraoxatridecan-13-ol as a raw material alcohol, and 4.5 mL of hexane as an azeotropic solvent (corresponding to a volume ratio of methyl acrylate / azeotropic solvent = 1.0) were charged into reactor 10. In addition, the portion of straight tube 22 packed with adsorbent A was filled with hexane. Next, the reactor 10 was heated using an oil bath at 80° C. while stirring for 3 hours to carry out an ester exchange reaction, thereby obtaining the target product, an acrylic acid ester of 2,5,8,11-tetraoxatridecan-13-ol. Methanol, which was a by-product alcohol produced by the transesterification reaction, hexane, and a portion of the unreacted methyl acrylate vaporized, were cooled and condensed in the cooling pipe 30, and turned into a liquid, which fell into the straight pipe 22. The methanol that fell into the straight pipe 22 was adsorbed by the adsorbent A packed in the straight pipe 22. On the other hand, the methyl acrylate and hexane that fell into the straight pipe 22 passed through the connecting pipe 24 and were returned to the reactor 10.

[0046] The yield of the target product was measured in the same manner as in Example 1, and was found to be 96%.

[0047] [Comparative Example 1] The straight pipe 22 was not filled with adsorbent A, and the straight pipe 22 was filled with hexane up to the point where the straight pipe 22 joins with the connecting pipe 24, so that hexane would not flow into the connecting pipe 24. Except for this, a transesterification reaction was carried out in the same manner as in Example 1, and the target product was obtained. The yield of the target product was measured in the same manner as in Example 1, and was found to be 71%.

[0048] These results demonstrate that by carrying out the transesterification reaction while adsorbing the by-product alcohol, methanol, onto an adsorbent and removing it from the reaction system, the target product, (meth)acrylic acid ester, could be produced in high yield, even without using a large excess of the raw material ester, methyl acrylate.

[0049] On the other hand, when the transesterification reaction was carried out without adsorbing methanol to the adsorbent, the yield of the target product was low. The reason for this low yield is thought to be as follows. Since methanol, a by-product alcohol, and hexane, an azeotropic solvent, are easily separated, if only methanol and hexane form an azeotrope, the straight pipe 22 can be filled with hexane without filling the straight pipe 22 with adsorbent A. As a result, the methanol and hexane can be separated into two layers in the straight pipe 22, and only the lighter hexane can be returned to the reactor 10. However, if methyl acrylate also vaporizes, the methanol, hexane, and methyl acrylate cooled in the cooling pipe 30 tend to mix in the straight pipe 22, making it difficult to separate the methanol. As a result, a portion of the methanol is also returned to the reactor 10, which is thought to make it difficult for the transesterification reaction to be biased toward the product system and reduce the yield of the target product. [Explanation of symbols]

[0050] 1. (Meth)acrylic acid ester manufacturing equipment 10. Reactor 20 Dean-Stark Apparatus 21 Fractionating tube 22 straight pipe 23 Cook 24 Connecting pipe 30 Cooling pipe 40 thermometer A. Adsorbent

Claims

1. A method for producing a (meth)acrylic acid ester by subjecting a compound represented by the following general formula (1) to an ester exchange reaction with an alcohol in the presence of a zinc catalyst, The method for producing a (meth)acrylic ester comprises producing a target (meth)acrylic ester while removing an alcohol by-produced in the transesterification reaction by adsorption with an adsorbent. CH ２ =CR １ -COOR ２ ・・・(1) (In general formula (1), R １ is a hydrogen atom or a methyl group, R ２ is a methyl group or an ethyl group.

2. The method for producing a (meth)acrylic acid ester according to claim 1 , wherein the adsorbent is a synthetic zeolite.

3. The method for producing a (meth)acrylic acid ester according to claim 1 or 2, wherein the transesterification reaction is carried out in the presence of hexane.

4. The method for producing a (meth)acrylic acid ester according to claim 1 or 2, wherein the transesterification reaction is carried out in the presence of a polymerization inhibitor.

5. The method for producing a (meth)acrylic acid ester according to claim 4, wherein the polymerization inhibitor is 2,2,6,6-tetramethylpiperidine-1-oxyl.

6. The method for producing a (meth)acrylic acid ester according to claim 5, wherein the amount of the 2,2,6,6-tetramethylpiperidine-1-oxyl used is 0.05 to 0.5 moles per mole of the alcohol.

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