Method for producing (METH)acrylic acid ester having vinyl ether group

Abstract

To provide a method for efficiently preventing polymerization in the gas phase in producing a (meth)acrylic acid ester having a vinyl ether group by ester exchange reaction.SOLUTION: There is provided a method for producing a (meth)acrylic acid ester having a vinyl ether group, which comprises a step of obtaining a (meth)acrylic acid ester having a vinyl ether group by ester exchange reaction by using a raw material solution containing a raw material (meth)acrylic acid ester, a vinyl ether compound containing a hydroxyl group, a catalyst, N-nitrosamine (salt) and water, wherein the mass ratio of water in the raw material solution is 1500 ppm or more and 5 mass% or less and the molar ratio of water to N-nitrosamine (salt) is 40 or more and 1100 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a (meth)acrylic acid ester having a vinyl ether group. More specifically, the present invention relates to a method for producing a (meth)acrylic acid ester having a vinyl ether group that is used as a raw material for various industrial products. [Background technology]

[0002] (Meth)acrylic acid esters having a vinyl ether group have a (meth)acryloyl group containing a radically polymerizable double bond, and are easily polymerizable compounds that can be easily polymerized by heat, light, ultraviolet light, etc., and are therefore very useful as monomers for polymers, and various methods for producing them have been investigated. As one of the reaction processes, a process for producing a (meth)acrylic acid ester having a vinyl ether group by subjecting a raw material (meth)acrylic acid ester and a hydroxyl group-containing vinyl ether compound to an ester exchange reaction is known. In this reaction process, since both the raw material and the target product are easily polymerizable compounds, various methods for preventing their polymerization have been investigated.

[0003] For example, it has been disclosed that popcorn polymerization of an acrylic acid ester or a methacrylic acid ester can be prevented by adding an N-nitrosamine to the acrylic acid ester or the methacrylic acid ester (see, for example, Patent Document 1).

[0004] Also disclosed is a method for producing a (meth)acrylic ester having an ether group from a reaction raw material containing a (meth)acrylic ester and a hydroxyl group-containing ether compound, the production method comprising the step of reacting the reaction raw material in the presence of a specific N-nitrosophenylhydroxylamine salt, a phosphite ester and / or a thioether, and a primary antioxidant (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 1973-125315 [Patent Document 2] JP 2012-197236 A Summary of the Invention [Problem to be solved by the invention]

[0006] The above-mentioned N-nitrosamines themselves do not have a polymerization inhibitory effect, but the decomposition products due to heat, acid, etc. during the reaction exert a polymerization inhibitory effect, particularly in the gas phase of the reaction system. Here, in the invention described in Patent Document 2, only about 30% of the total amount of N-nitrosamines is decomposed by the end of the reaction, and most of them remain in the system without being decomposed, which poses problems in terms of efficiency and economy.

[0007] The present invention has been made in consideration of the above-mentioned current situation, and an object of the present invention is to provide a method for efficiently preventing polymerization in the gas phase when producing a (meth)acrylic acid ester having a vinyl ether group by a transesterification reaction. [Means for solving the problem]

[0008] The present inventors have conducted various studies on methods for efficiently preventing polymerization in the gas phase when producing a (meth)acrylic ester having a vinyl ether group by transesterification, and have focused on the decomposition rate of N-nitrosamine (salt).The present inventors have found that in a method for producing a (meth)acrylic ester having a vinyl ether group, which uses a raw material solution containing a raw material (meth)acrylic ester, a hydroxyl group-containing vinyl ether compound, a catalyst, N-nitrosamine (salt), and water to obtain a (meth)acrylic ester having a vinyl ether group by transesterification, the mass ratio of water in the raw material solution is set to 1500 ppm or more and 5 mass% or less, and the molar ratio of water to N-nitrosamine (salt) is set to 40 or more and 1100 or less, and that the decomposition rate of N-nitrosamine (salt) can be increased and polymerization in the gas phase can be more efficiently prevented.The inventors have come up with the idea of ​​brilliantly solving the above-mentioned problems, and have arrived at the present invention.

[0009] That is, the present invention (1) is a method for producing a (meth)acrylic ester having a vinyl ether group, comprising a step of obtaining a (meth)acrylic ester having a vinyl ether group by transesterification using a raw material solution containing a raw material (meth)acrylic ester, a hydroxyl group-containing vinyl ether compound, a catalyst, an N-nitrosamine (salt), and water, wherein the mass proportion of water in the raw material solution is 1500 ppm or more and 5 mass% or less, and the molar ratio of water to N-nitrosamine (salt) is 40 or more and 1100 or less.

[0010] The present invention (2) relates to the method for producing a (meth)acrylic acid ester having a vinyl ether group according to the present invention (1), characterized in that the hydroxyl group-containing vinyl ether compound is diethylene glycol monovinyl ether, and the (meth)acrylic acid ester having a vinyl ether group is 2-(2-vinyloxyethoxy)ethyl (meth)acrylate.

[0011] The present invention (3) is the method for producing a (meth)acrylic acid ester having a vinyl ether group according to the present invention (1) or (2), characterized in that the N-nitrosamine (salt) is N-nitrosophenylhydroxylamine (salt). Effect of the Invention

[0012] The method for producing a (meth)acrylic acid ester having a vinyl ether group of the present invention has the above-mentioned configuration and can efficiently prevent polymerization of the (meth)acryloyl group in the gas phase. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing an example of a manufacturing apparatus for carrying out the manufacturing method of the present invention. [Diagram 2] 1 is a graph showing the correlation between water concentration and NPH decomposition rate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described in detail below. In addition, a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

[0015] <Step of Obtaining a (Meth)acrylic Acid Ester Having a Vinyl Ether Group> The production method of the present invention includes a step of obtaining a (meth)acrylic ester having a vinyl ether group by transesterification using a raw material solution containing a raw material (meth)acrylic ester, a hydroxyl group-containing vinyl ether compound, a catalyst, an N-nitrosamine (salt), and water, in which the mass proportion of water in the raw material solution is 1500 ppm or more and 5 mass% or less, and the molar ratio of water to N-nitrosamine (salt) is 40 or more and 1100 or less. In this specification, the step of obtaining a (meth)acrylic ester having a vinyl ether group by transesterification is also referred to as a reaction step.

[0016] In this specification, the term "(meth)acrylic acid ester" refers to an acrylic acid ester and / or a methacrylic acid ester, and the term "(meth)acryloyl group" refers to an acryloyl group and / or a methacryloyl group.

[0017] (water) In the production method of the present invention, the raw material solution contains water at 1500 ppm or more and 5 mass % or less in 100 mass % of the raw material solution, and the molar ratio of water to N-nitrosamine (salt) is 40 to 1100. By containing water at 1500 ppm or more and a molar ratio of 40 or more, the decomposition rate of N-nitrosamine (salt) becomes very high, and the decomposition product functions as a polymerization inhibitor, and gas phase polymerization can be sufficiently prevented. In addition, if the mass ratio of water is 5 mass % or less and the molar ratio is 1100 or less, it is considered that the effect can be prevented from becoming saturated.

[0018] The mass ratio of water is preferably 2000 ppm or more, more preferably 2500 ppm or more, and particularly preferably 3000 ppm or more, from the viewpoint of more sufficiently preventing gas phase polymerization in the reaction step. Also, from the viewpoint of more effectively preventing the effect from being saturated, the mass ratio of water is preferably 4 mass% or less, and particularly preferably 3 mass% or less. The mass ratio and molar ratio of water refer to the mass ratio or molar ratio of water in the raw material solution to be subjected to the reaction step. The raw material solution may be charged in a reaction vessel or other reaction apparatus all at once, or may be continuously or intermittently supplied to the reaction apparatus. The raw material, catalyst, water, etc. may also be supplied to the reaction apparatus during the reaction period. For example, one of the preferred forms of the present invention is that water is supplied to the reaction apparatus during the reaction period. The raw material, catalyst, water, etc. supplied during the reaction period are also considered to be part of the raw material solution.

[0019] From the viewpoint of more adequately preventing gas phase polymerization in the reaction step, the molar ratio of water to the N-nitrosamine (salt) is preferably 60 or more, and more preferably 75 or more. Moreover, from the viewpoint of more effectively preventing the effect from becoming saturated, the molar ratio of water is preferably 900 or less, and more preferably 800 or less. The above molar ratio of water refers to the molar ratio of water to N-nitrosamine (salt) in the raw material solution subjected to the reaction step.

[0020] The water may be water that is already contained in the raw materials or agents (moisture derived from the raw materials, etc.), may be water that is added (mixed) to the raw materials, etc., or may be both of these, but as described below, it is preferable that at least a portion of the water is added to the raw materials, etc. Examples of water added to the raw materials, etc. include tap water (tap water), distilled water, purified water, pure water, ion-exchanged water, industrial pure water, etc., and one or more of these can be used.

[0021] (N-Nitrosamines (salts)) The N-nitrosamine (salt) is a compound having a group represented by O=NN=. The "=" at the right end of O=NN= may be one double bond or two single bonds. Examples of the N-nitrosamine (salt) include N-nitrosamine-N-methylaniline, N-nitroso-N,N'-dimethylamine, N-nitroso-N-methyl-p-toluenesulfonamide, N-nitrosophenylhydroxylamine (salt) (NPH), ortho-nitrosoresorcinol monomethyl ether, N-nitroso-N-methylurethane, para-nitrosodiphenylamine, α-nitroso-β-naphthol, M-nitroso-N-methyl-β-aminonaphthalene, 5-nitroso-8-hydroxyquinoline, β-nitroso-α-naphthol, and N-nitrosophenylhydroxylamine, and one or more of these may be used. The above-mentioned N-nitrosamine (salt) refers to N-nitrosamine and / or N-nitrosamine salt, and may be in the form of anion in the raw material solution.

[0022] Of these, the N-nitrosamine (salt) is preferably NPH. The above-mentioned NPH is represented by the following general formula (1);

[0023] [ka]

[0024] (In the formula, M represents a metal atom, an ammonium group, or a hydrogen atom. n represents a positive number equal to the valence of M. The dotted line connecting M and the oxygen atom indicates that M may be coordinated to the oxygen atom.) M in the above general formula (1) represents a metal atom, an ammonium group, or a hydrogen atom, and examples of the metal atom include aluminum, copper, iron (III), tin, zinc, magnesium, titanium, cobalt, nickel, zirconium, vanadium (V), niobium, tantalum, phosphorus, bismuth (III), etc. Among these, the above M is preferably aluminum, zinc, tin, phosphorus, iron (III), or an ammonium group, more preferably aluminum, zinc, tin, or an ammonium group, and even more preferably aluminum or an ammonium group. The NPH is particularly preferably, for example, N-nitrosophenylhydroxylamine ammonium salt (NPHN).

[0025] The N-nitrosamine (salt) is preferably 10 ppm or more, more preferably 50 ppm or more, and even more preferably 100 ppm or more in 100 mass% of the raw material solution. This makes it possible to more sufficiently prevent the polymerization of the raw material and the target product in the reaction step. In addition, the mass ratio of the N-nitrosamine (salt) is preferably 2 mass% or less, more preferably 1 mass% or less, and even more preferably 1000 ppm or less. This is economical and can more sufficiently prevent the excessive N-nitrosamine (salt) from remaining and causing the target product to deteriorate in polymerization and color. When two or more kinds of the N-nitrosamines (salts) are used, the above mass ratio is the mass ratio of the total.

[0026] In the reaction step of the present invention, the mass proportion of N-nitrosamine (salt) is preferably 2 ppm to 5 mass% relative to 100 mass% of the hydroxyl group-containing vinyl ether compound, which is the reaction raw material. The amount used is more preferably 10 ppm to 1 mass%, further preferably 20 to 5000 ppm, and particularly preferably 100 to 2000 ppm.

[0027] (Raw material (meth)acrylic ester) The raw material (meth)acrylic acid ester is not particularly limited as long as it can undergo an ester exchange reaction with a hydroxyl group-containing vinyl ether compound to produce the target product, that is, a (meth)acrylic acid ester having a vinyl ether group, and one or more of them can be used.

[0028] [ka]

[0029] (In the formula, R 1 R represents a hydrogen atom or a methyl group. 3 represents an organic group. R in the above general formula (2) 3 The organic group represented by the formula (I) is not particularly limited, but for example, a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms, or an aromatic group having 6 to 10 carbon atoms which may be substituted, etc. are preferable, and an alkyl group having 1 to 4 carbon atoms is more preferable.

[0030] Examples of the (meth)acrylic acid ester represented by the above general formula (2) include lower alkyl (meth)acrylate esters (the alkyl group of the alkyl ester has 1 to 4 carbon atoms), such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, and t-butyl (meth)acrylate. Among these, methyl acrylate (AM), methyl methacrylate, ethyl acrylate, and ethyl methacrylate are preferred, and methyl acrylate (AM) and ethyl acrylate are more preferred.

[0031] The raw material (meth)acrylic acid ester is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, still more preferably 40% by mass or more, and particularly preferably 50% by mass or more in 100% by mass of the raw material solution. The mass ratio of the raw material (meth)acrylic acid ester is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less. When two or more kinds of the raw material (meth)acrylic acid esters are used, the above mass ratio is the mass ratio of the total.

[0032] (Hydroxyl group-containing vinyl ether compound) The hydroxyl group-containing vinyl ether compound is not particularly limited as long as it contains a hydroxyl group and can undergo an ester exchange reaction with a raw material (meth)acrylic acid ester to produce a target product, that is, a vinyl ether group-containing (meth)acrylic acid ester, and one or more of such compounds can be used. Among them, preferred are compounds represented by the following general formula (3):

[0033] [ka]

[0034] (In the formula, R 2represents an organic group. Preferred are hydroxyl group-containing vinyl ether compounds represented by the following formula:

[0035] In the hydroxyl group-containing vinyl ether compound represented by the above general formula (3), R 2 The organic group represented by the formula (1) is not particularly limited, and examples thereof include linear, branched or cyclic alkylene groups having 2 to 20 carbon atoms, alkylene groups having 2 to 20 carbon atoms having an oxygen atom in the structure via an ether bond and / or an ester bond, and aromatic groups having 6 to 11 carbon atoms which may be substituted. Among these, alkylene groups having 2 to 6 carbon atoms and alkylene groups having 4 to 10 carbon atoms having an oxygen atom in the structure via an ether bond are preferred.

[0036] Examples of the hydroxyl group-containing vinyl ether compound represented by the above general formula (3) include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxyisopropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-hydroxybutyl vinyl ether, 3-hydroxyisobutyl vinyl ether, 2-hydroxyisobutyl vinyl ether, 1-methyl-3-hydroxypropyl vinyl ether, 1-methyl-2-hydroxypropyl vinyl ether, 1-hydroxymethylpropyl vinyl ether, 4-hydroxycyclohexyl vinyl ether, 1,6-hexanediol monovinyl ether, 1,4-cyclohexanedimethanol monovinyl ether, 1,3-cyclohexanedimethanol monovinyl ether, 1,2-cyclohexanedimethanol monovinyl ether, Examples of the vinyl ether include vinyl ether, p-xylene glycol monovinyl ether, m-xylene glycol monovinyl ether, o-xylene glycol monovinyl ether, diethylene glycol monovinyl ether (DEGV), triethylene glycol monovinyl ether, tetraethylene glycol monovinyl ether, pentaethylene glycol monovinyl ether, oligoethylene glycol monovinyl ether, polyethylene glycol monovinyl ether, dipropylene glycol monovinyl ether, tripropylene glycol monovinyl ether, tetrapropylene glycol monovinyl ether, pentapropylene glycol monovinyl ether, oligopropylene glycol monovinyl ether, polypropylene glycol monovinyl ether, and ethylene glycol-propylene glycol copolymer monovinyl ether. One or more of these may be used.

[0037] Of the hydroxyl group-containing vinyl ether compounds represented by the above general formula (3), 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxyisopropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxycyclohexyl vinyl ether, 1,6-hexanediol monovinyl ether, 1,4-cyclohexanedimethanol monovinyl ether, DEGV, triethylene glycol monovinyl ether, and dipropylene glycol monovinyl ether are preferred, and DEGV is more preferred.

[0038] The amount of the hydroxyl group-containing vinyl ether compound is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 35% by mass or more, based on 100% by mass of the raw material solution. The mass proportion of the hydroxyl group-containing vinyl ether compound is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less. When two or more kinds of the hydroxyl group-containing vinyl ether compounds are used, the above mass ratio is the total mass ratio thereof.

[0039] In the above reaction step, the molar ratio of the raw material (meth)acrylic acid ester to the hydroxyl group-containing vinyl ether compound can be appropriately set depending on the combination of the types of raw material (meth)acrylic acid ester and hydroxyl group-containing vinyl ether compound, but is preferably, for example, 20 / 1 to 1 / 5. A blending ratio in this range is preferable in terms of yield and economic efficiency. More preferably, it is 15 / 1 to 1 / 3, and even more preferably, it is 10 / 1 to 1 / 2. Particularly preferably, it is 5 / 1 to 1 / 1.

[0040] (catalyst) The catalyst is not particularly limited as long as it has the effect of accelerating the transesterification reaction, and examples of the catalyst include oxides such as calcium oxide, barium oxide, lead oxide, zinc oxide, and zirconium oxide; hydroxides such as potassium hydroxide, sodium hydroxide, lithium hydroxide, calcium hydroxide, thallium hydroxide, tin hydroxide, lead hydroxide, and nickel hydroxide; halides such as lithium chloride, calcium chloride, tin chloride, lead chloride, zirconium chloride, and nickel chloride; carbonates such as potassium carbonate, rubidium carbonate, cesium carbonate, lead carbonate, zinc carbonate, and nickel carbonate; hydrogen carbonates such as potassium hydrogen carbonate, rubidium hydrogen carbonate, and cesium hydrogen carbonate; phosphates such as sodium phosphate, potassium phosphate, rubidium phosphate, lead phosphate, zinc phosphate, and nickel phosphate; nitrates such as lithium nitrate, calcium nitrate, lead nitrate, zinc nitrate, and nickel nitrate; carboxylates such as lithium acetate, calcium acetate, lead acetate, zinc acetate, and nickel acetate; sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, potassium t-butoxide, calcium alkoxy compounds such as titanium methoxide, calcium ethoxide, barium methoxide, barium ethoxide, tetraethoxytitanium, tetrabutoxytitanium, and tetra(2-ethylhexanoxy)titanium; acetylacetonate complexes such as lithium acetylacetonate, zirconia acetylacetonate, zinc acetylacetonate, dibutoxytin acetylacetonate, and dibutoxytitanium acetylacetonate; quaternary ammonium alkoxides such as tetramethylammonium methoxide, tetramethylammonium t-butoxide, and trimethylbenzylammonium ethoxide; dialkyltin compounds such as dimethyltin oxide, methylbutyltin oxide, dibutyltin oxide (DBTO), and dioctyltin oxide; distannoxanes such as bis(dibutyltin acetate) oxide and bis(dibutyltin laurate) oxide; and dialkyltin dicarboxylates such as dibutyltin diacetate and dibutyltin dilaurate (DBTL). One or more of these can be used.

[0041] Among these catalysts, potassium carbonate, cesium carbonate, tetraethoxytitanium, tetrabutoxytitanium, tetra(2-ethylhexanoxy)titanium, zirconia acetylacetonate, DBTO, dioctyltin oxide, bis(dibutyltin acetate) oxide, bis(dibutyltin laurate) oxide, dibutyltin diacetate, and DBTL are preferably used, and more preferably DBTO and DBTL.

[0042] The catalyst is preferably present in an amount of 100 ppm or more, more preferably 500 ppm or more, and even more preferably 1000 ppm or more, relative to 100% by mass of the raw material solution. The mass ratio of the catalyst is preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less. When two or more of the above catalysts are used, the above mass ratio is the total mass ratio thereof.

[0043] The amount of the catalyst used is not particularly limited and can be appropriately set, but is preferably in the range of 0.0001 to 20 mol% relative to 100 mol% of the hydroxyl group-containing vinyl ether compound. From the viewpoints of yield and economy, it is preferable that the amount of the catalyst used is in such a range. It is more preferably 0.0003 to 15 mol%, even more preferably 0.0005 to 10 mol%, and particularly preferably 0.001 to 5 mol%.

[0044] (Primary antioxidant) The raw material solution preferably further contains a primary antioxidant. The primary antioxidant is not particularly limited as long as it can capture and decompose the peroxy radicals generated in the liquid phase of the reaction system in the reaction step of the present invention, thereby suppressing the radical polymerization reaction involving the peroxy radicals. For example, phenol-based antioxidants such as hydroquinone, methoxyhydroquinone, hydroquinone monomethyl ether (MEHQ), benzoquinone, p-tert-butylcatechol, 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert-butyl-4,6-dimethylphenol, 2,4,6-tri-tert-butylphenol, 3,5-di-tert-butyl-4-hydroxytoluene (BHT), and 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane (TPB); alkylated diphenylamine, N,N'-diphenyl-p-phenylenediamine, phenotypic antioxidants such as phenylmethylsuccinimide, ... aromatic amine antioxidants such as azine (PTZ); cyclic amine antioxidants such as 4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, and 1-hydroxy-4-benzoyloxy-2,2,6,6-tetramethylpiperidine; copper dimethyldithiocarbamate, copper diethyldithiocarbamate, Examples of the primary antioxidant include copper dithiocarbamate antioxidants such as copper dibutyldithiocarbamate; and N-oxyl antioxidants such as 2,2,6,6-tetramethylpiperidine-N-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl, and esters of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl. Among these, the primary antioxidant is preferably a phenolic antioxidant or an aromatic amine antioxidant. Thus, the embodiment in which the primary antioxidant is a phenolic antioxidant and / or an aromatic amine antioxidant is also one of the preferred embodiments of the present invention. As the primary antioxidant, hydroquinone, MEHQ, 3,5-di-tert-butyl-4-hydroxytoluene, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, and PTZ are more preferred.

[0045] The primary antioxidant is preferably 100 ppm or more, more preferably 500 ppm or more, and even more preferably 1000 ppm or more, based on 100 mass % of the raw material solution. The mass proportion of the N-nitrosamine (salt) is preferably 2 mass % or less, more preferably 1 mass % or less, and even more preferably 5000 ppm or less. When two or more types of the primary antioxidants are used, the above mass ratio is the total mass ratio thereof.

[0046] In the reaction step of the present invention, the amount of the primary antioxidant used is preferably 2 ppm to 5 mass% relative to 100 mass% of the hydroxyl group-containing vinyl ether compound, which is the reaction raw material. The amount of the primary antioxidant used is preferably within such a range in terms of yield, inhibition of polymerization in the liquid phase of the reaction system, and economic efficiency. The amount used is more preferably 10 ppm to 3 mass%, further preferably 50 ppm to 1 mass%, and particularly preferably 100 ppm to 5000 ppm.

[0047] (Secondary antioxidant) The raw material solution may further contain a phosphite and / or a thioether. The above-mentioned phosphite and / or thioether act as a secondary antioxidant that decomposes peroxides produced in the liquid phase of the reaction system in the reaction step of the present invention, thereby inhibiting polymerization reactions involving peroxides.

[0048] Specific examples of the above phosphorous ester include triphenyl phosphite (TPP), tris(2,4-di-tert-butylphenyl)phosphite, 2,2-methylenebis(4,6-di-tert-butylphenyl)octylphosphite (BPOP), diphenyl mono(tridecyl)phosphite, diphenyl monodecylphosphite, cyclic neopentatetraylbis(octadecylphosphite), trioleylphosphite, etc., and one or more of these can be used. Among these, TPP, tris(2,4-di-tert-butylphenyl)phosphite, BPOP, diphenyl mono(tridecyl)phosphite, and diphenyl monodecylphosphite are preferred, and TPP, tris(2,4-di-tert-butylphenyl)phosphite, and BPOP are more preferred. Particularly preferred are TPP and tris(2,4-di-tert-butylphenyl)phosphite.

[0049] Specific examples of the thioether include dilauryl 3,3'-thiodipropionate (TDPL), distearyl 3,3'-thiodipropionate, didodecyl 3,3'-thiodipropionate, dioctadecyl 3,3'-thiodipropionate, and pentaerythritol tetrakis (β-laurylthiopropionic acid). Among these, TDPL, distearyl 3,3'-thiodipropionate, didodecyl 3,3'-thiodipropionate, and dioctadecyl 3,3'-thiodipropionate are preferred, and TDPL and distearyl 3,3'-thiodipropionate are more preferred. TDPL is particularly preferred.

[0050] The feedstock solution may also contain a secondary antioxidant, such as tris(2,4-di-t-butylphenyl)phosphite (DBPP).

[0051] The secondary antioxidant is preferably present in an amount of 100 ppm or more, more preferably 500 ppm or more, and even more preferably 1000 ppm or more, based on 100% by mass of the raw material solution. The mass proportion of the secondary antioxidant is preferably 2% by mass or less, more preferably 1% by mass or less, and even more preferably 5000 ppm or less. When two or more types of the secondary antioxidants are used, the above mass ratio is the total mass ratio thereof.

[0052] In the reaction step of the present invention, the amount of the secondary antioxidant in the raw solution is preferably 2 ppm to 5 mass% relative to 100 mass% of the hydroxyl-containing vinyl ether compound, which is the raw material for the reaction. The amount of the secondary antioxidant is preferably within such a range in terms of yield, inhibition of polymerization in the liquid phase of the reaction system, and economic efficiency. The amount is more preferably 10 ppm to 3 mass%, further preferably 50 ppm to 1 mass%, and particularly preferably 100 to 5000 ppm.

[0053] (Target product: (meth)acrylic acid ester having a vinyl ether group) In the production method of the present invention, a (meth)acrylic acid ester having a vinyl ether group is produced by transesterification of a raw material (meth)acrylic acid ester and a hydroxyl group-containing vinyl ether compound. Therefore, the obtained (meth)acrylic acid ester having a vinyl ether group is a compound synthesized by transesterification of a compound selected from the raw material (meth)acrylic acid ester and the hydroxyl group-containing vinyl ether compound. In this specification, the target product, a (meth)acrylic acid ester having a vinyl ether group, is also simply referred to as a (meth)acrylic acid ester having a vinyl ether group. In particular, when the raw material (meth)acrylic acid ester is a compound represented by general formula (2) and the hydroxyl group-containing vinyl ether compound is a compound represented by general formula (3), the obtained (meth)acrylic acid ester having a vinyl ether group has the following general formula (4):

[0054] [ka]

[0055] (In the formula, R 1 R represents a hydrogen atom or a methyl group. 2 represents an organic group.) In this way, the embodiment in which the obtained (meth)acrylic acid ester having a vinyl ether group is a (meth)acrylic acid ester having a vinyl ether group represented by general formula (4) is also one of the preferred embodiments of the present invention. In addition, R in the general formula (4) 1 is R in general formula (2). 1 The same as R in general formula (4). 2 is R in general formula (3). 2 is the same as:

[0056] Specific examples of the (meth)acrylic acid ester having a vinyl ether group represented by the above general formula (4) include 2-vinyloxyethyl (meth)acrylate, 3-vinyloxypropyl (meth)acrylate, 1-methyl-2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 1-methyl-3-vinyloxypropyl (meth)acrylate, 1-vinyloxymethylpropyl (meth)acrylate, 2-methyl-3-vinyloxypropyl (meth)acrylate, and (meth)acrylic acid. 1,1-Dimethyl-2-vinyloxyethyl, 3-vinyloxybutyl (meth)acrylate, 1-methyl-2-vinyloxypropyl (meth)acrylate, 2-vinyloxybutyl (meth)acrylate, 4-vinyloxycyclohexyl (meth)acrylate, 6-vinyloxyhexyl (meth)acrylate, 4-vinyloxymethylcyclohexylmethyl (meth)acrylate, 3-vinyloxymethylcyclohexylmethyl (meth)acrylate, 2-vinyloxymethylcyclohexylmethyl (meth)acrylate, p-vinyloxymethylphenylmethyl (meth)acrylate , m-vinyloxymethylphenylmethyl (meth)acrylate, o-vinyloxymethylphenylmethyl (meth)acrylate, 2-(vinyloxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxy)propyl (meth)acrylate, 2-(vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxy)ethyl (meth)acrylate (meth)acrylate 2-(vinyloxyethoxyisopropoxy)ethyl, (meth)acrylate 2-(vinyloxyisopropoxyethoxy)ethyl, (meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)ethyl, (meth)acrylate 2-(vinyloxyethoxyethoxy)propyl, (meth)acrylate 2-(vinyloxyethoxyisopropoxy)propyl, (meth)acrylate 2-(vinyloxyisopropoxyethoxy)propyl, (meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)propyl, (meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)propyl,2-(vinyloxyethoxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropoxyethoxy)ethyl (meth)acrylate, 2-(isopropoxy Examples of such acrylates include 2-(vinyloxyethoxy)ethyl acrylate, 2-(isopropoxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropoxyethoxyethoxyethoxy)ethyl (meth)acrylate, polyethylene glycol monovinyl ether (meth)acrylate, and polypropylene glycol monovinyl ether (meth)acrylate. Among these, 2-(vinyloxyethoxy)ethyl acrylate (VEEA (registered trademark)) and 2-(vinyloxyethoxy)ethyl methacrylate (VEEM (registered trademark)) are preferred, and 2-(vinyloxyethoxy)ethyl acrylate is more preferred. 2-(vinyloxyethoxy)ethyl acrylate is particularly prone to polymerization, and by applying the production method of the present invention, polymerization in the gas phase can be efficiently prevented.

[0057] The reaction step is preferably carried out in an atmosphere in which the molecular oxygen concentration in the gas phase of the reaction system is 0.001 to 21% by volume. By setting the molecular oxygen concentration in the gas phase in this range, the polymerization reaction during the reaction step can be more effectively prevented, and the target product, a (meth)acrylic acid ester having a vinyl ether group, can be produced in a high yield. The molecular oxygen concentration in the gas phase is more preferably 0.005 to 15% by volume, and even more preferably 0.01 to 10% by volume.

[0058] Methods for adjusting the molecular oxygen concentration in the gas phase of the reaction system to the above-mentioned preferred range include (a) a method of supplying molecular oxygen or a gas containing molecular oxygen such as air to a reaction vessel during the reaction (where steam is present) to adjust the molecular oxygen concentration in the gas phase, (b) a method of supplying molecular oxygen or a gas containing molecular oxygen such as air and an inert gas such as nitrogen or argon to a reaction vessel during the reaction (where steam is present) to adjust the molecular oxygen concentration in the gas phase, and (c) a method of premixing molecular oxygen or a gas containing molecular oxygen such as air with an inert gas such as nitrogen or argon and supplying the mixture to a reaction vessel during the reaction (where steam is present) to adjust the molecular oxygen concentration in the gas phase. In addition, molecular oxygen and / or a mixed gas containing molecular oxygen may be supplied to the reaction system continuously or intermittently to either or both of the liquid phase and the gas phase in the reaction system.

[0059] In addition, since the reaction in the above reaction step is an ester exchange reaction, alcohol is produced as a by-product as the reaction proceeds. It is preferable to remove the by-product alcohol from the reaction system. Examples of the method for removing the by-produced alcohol include a method of carrying out the reaction under reduced pressure, a method of carrying out the reaction using an azeotropic solvent, a method of carrying out the reaction in the presence of an adsorbent, etc. Among these, the method of carrying out the reaction under reduced pressure and the method of carrying out the reaction using an azeotropic solvent are preferred.

[0060] The azeotropic solvent is not particularly limited as long as it does not inhibit the transesterification reaction, and examples thereof include ethers such as diethyl ether, diisopropyl ether, and dibutyl ether; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as pentane, hexane, heptane, and cyclohexane; and halogenated hydrocarbons such as chloroform, methylene chloride, 1,2-dichloroethane, and chlorobenzene. These azeotropic solvents may be used alone or in combination of two or more. In addition, the raw material (meth)acrylic acid ester used in excess may be used as the azeotropic solvent.

[0061] The amount of the azeotropic solvent used is not particularly limited, but is preferably 0 to 300% by mass of the hydroxyl group-containing vinyl ether compound, which is the reaction raw material. From the viewpoints of yield and economy, it is preferable that the amount of the azeotropic solvent used is within such a range. The amount used is more preferably 1 to 200% by mass, further preferably 2 to 150% by mass, and particularly preferably 3 to 100% by mass.

[0062] The reaction temperature in the reaction step is not particularly limited, but is preferably equal to or higher than the boiling point or azeotropic temperature of the by-produced alcohol, and is specifically preferably equal to or higher than 40°C, more preferably equal to or higher than 50°C, and even more preferably equal to or higher than 60°C. This allows the by-produced alcohol to be sufficiently removed, and the amount of decomposition of N-nitrosamine (salt) is increased, so that the polymerization inhibition effect in the gas phase becomes more remarkable. In addition, the reaction temperature is preferably equal to or lower than 180°C, more preferably equal to or lower than 140°C, and even more preferably equal to or lower than 100°C. This allows the polymerization reaction of the easily polymerizable compound to be difficult to proceed, so that the polymerization inhibition effect in the gas phase becomes more remarkable. The reaction pressure is not particularly limited, and may be normal pressure, pressurized pressure, or reduced pressure, but reduced pressure is preferable from the viewpoint of removing the by-produced alcohol, as described above. In addition, the reaction time may be appropriately set so that the reaction in the reaction step is completed, and may be, for example, 3 to 20 hours.

[0063] The production method of the present invention may include other steps described below so long as it includes the above reaction step.

[0064] <Step of mixing raw materials and water> In the production method of the present invention, the water in the raw material solution may be only that which is previously contained in at least one selected from the raw material (meth)acrylic acid ester, hydroxyl group-containing vinyl ether compound, catalyst, N-nitrosamine (salt), and other agents (also referred to as raw materials, etc. in this specification) (moisture derived from raw materials, etc.), but mixing the raw materials, etc. with water and controlling the mass ratio and molar ratio of water in the raw material solution within a predetermined range is one of the preferred forms of the production method of the present invention. That is, the production method of the present invention preferably includes, for example, a step of mixing at least one selected from the group consisting of the raw material (meth)acrylic acid ester, hydroxyl group-containing vinyl ether compound, catalyst, and N-nitrosamine (salt) with water before the step of obtaining a (meth)acrylic acid ester having a vinyl ether group. The mixing step may be a step of adding water to the raw materials, etc., a step of adding the raw materials, etc. to water, or a step of putting the raw materials, etc. and water into a reaction vessel, respectively. This allows the mass ratio and molar ratio of water in the raw material solution to be suitably adjusted. The production method of the present invention also preferably includes a step of supplying water and / or raw materials to the liquid phase part of the reaction system, for example, during the step of obtaining a (meth)acrylic acid ester having a vinyl ether group.

[0065] [Purification after reaction process] In the production method of the present invention, after the above reaction step, the resulting (meth)acrylic acid ester having a vinyl ether group can be purified and separated from the reaction solution. The method for carrying out the purification step is not particularly limited, but examples thereof include a raw material recovery operation, a catalyst recovery operation, a neutralization operation, a filtration operation, a decantation operation, an extraction operation, a water washing operation, an evaporation operation, a distillation operation, and a column chromatography operation. The above-mentioned operations can be carried out alone or in combination of two or more. Among these, purification by distillation is particularly preferred. Furthermore, the impurities removed by purification can be reused as raw materials or agents, if necessary.

[0066] <Separation process of raw material (meth)acrylic acid ester> For example, the production method of the present invention preferably includes a step of separating the unreacted raw material (meth)acrylic acid ester after the above reaction step. In the step of separating the raw material (meth)acrylic acid ester, the raw material (meth)acrylic acid ester is preferably separated by evaporation through distillation. The separated raw material (meth)acrylic acid ester can be recovered and reused as a raw material (meth)acrylic acid ester in the reaction step.

[0067] The temperature in the separation step of the raw material (meth)acrylic acid ester can be appropriately set based on the boiling point of the raw material (meth)acrylic acid ester. The pressure is not particularly limited and may be normal pressure, increased pressure, or reduced pressure, but reduced pressure is preferred. The time may be appropriately set so that the raw material (meth)acrylic acid ester can be sufficiently removed.

[0068] <Catalyst separation process> For example, the production method of the present invention preferably includes a step of separating the catalyst after the reaction step. In the catalyst separation step, the catalyst is preferably separated by evaporating the target product, the (meth)acrylic acid ester having a vinyl ether group, by distillation, which makes it possible to remove impurities having a higher boiling point than the target product, the (meth)acrylic acid ester having a vinyl ether group, together with the catalyst.

[0069] The temperature in the catalyst separation step is usually higher than the temperature in the raw material (meth)acrylic acid ester separation step, and can be appropriately set based on the boiling point of the target product, the (meth)acrylic acid ester having a vinyl ether group, etc. The pressure is not particularly limited and may be normal pressure, increased pressure, or reduced pressure, but reduced pressure is preferred. The time may be appropriately set.

[0070] <Purification process of the target product, the (meth)acrylic acid ester having a vinyl ether group> It is preferable that the production method of the present invention further includes a step of purifying the target product, that is, the (meth)acrylic ester having a vinyl ether group, after, for example, the above-mentioned reaction step, the above-mentioned raw material (meth)acrylic ester separation step, and the above-mentioned catalyst separation step. In the purification step of the (meth)acrylic acid ester having a vinyl ether group, it is preferable to separate the (meth)acrylic acid ester having a vinyl ether group, which is the target product, by evaporating it by distillation. This makes it possible to remove impurities having a higher boiling point than the (meth)acrylic acid ester having a vinyl ether group, which is the target product. In addition, for example, it is more preferable to remove the impurities having a lower boiling point than the (meth)acrylic acid ester having a vinyl ether group, which is the target product, by evaporating it by distillation, and then evaporating and separating the (meth)acrylic acid ester having a vinyl ether group, which is the target product, by distillation. The purification step of the (meth)acrylic acid ester having a vinyl ether group is preferably carried out using a rectification column, such as an Oldershaw type rectification column.

[0071] The temperature in the purification step of the (meth)acrylic acid ester having a vinyl ether group can be appropriately set based on the boiling point of the (meth)acrylic acid ester having a vinyl ether group and the boiling points of impurities. The pressure is not particularly limited and may be normal pressure, increased pressure, or reduced pressure, but reduced pressure is preferred. The time may be appropriately set.

[0072] FIG. 1 is a diagram showing an example of a production apparatus for carrying out the production method of the present invention. FIG. 1 shows an apparatus equipped with a reaction tank 11 for an ester exchange reaction, a first distillation column 21 for evaporating a raw material (meth)acrylic acid ester and separating it from a (meth)acrylic acid ester having a vinyl ether group, and a second distillation column 31 for evaporating the (meth)acrylic acid ester having a vinyl ether group and separating a catalyst and high-boiling-point impurities from the (meth)acrylic acid ester having a vinyl ether group.

[0073] The raw material solution 1 to be fed to the apparatus is first introduced into the reaction tank 11. In the transesterification reaction in the reaction tank 11, the water content in the raw material solution 1 is 1500 ppm or more and 5 mass % or less, so that the polymerization of the (meth)acryloyl group is sufficiently prevented while the target product, the (meth)acrylic acid ester having a vinyl ether group, can be obtained. Although not shown, the alcohol by-produced in the transesterification reaction is usually a low boiling component, and can be evaporated and removed from the reaction tank 11. The obtained solution containing the (meth)acrylic acid ester having a vinyl ether group is sent to the first distillation tower 21 via line 71. In the first distillation tower 21, the unreacted raw material (meth)acrylic acid ester is evaporated and separated. The separated raw material (meth)acrylic acid ester is returned to the reaction tank 11 via line 81. The solution containing the (meth)acrylic acid ester having a vinyl ether group, which is the bottom liquid in the first distillation tower 21, is sent to the second distillation tower 31 via line 72. In the second distillation column 31, the (meth)acrylic acid ester having a vinyl ether group is evaporated, and a crude product 3 is obtained from the top of the second distillation column 31. The bottom liquid in the second distillation column 31 contains a large amount of impurities, such as a catalyst, that have a higher boiling point than the (meth)acrylic acid ester having a vinyl ether group, and is therefore removed as waste oil 2.

[0074] The (meth)acrylic acid ester having a vinyl ether group obtained by the production method of the present invention can be suitably used as a raw material for various industrial products. EXAMPLES

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[0076] [Comparative Example 1] A 2L glass round-bottom flask (reactor) equipped with an Oldershaw type rectification column, a stirrer, a thermometer, a gas inlet tube, and a liquid sequential input line was prepared. 620g of methyl acrylate (hereinafter abbreviated as "AM"), 453g of diethylene glycol monovinyl ether (hereinafter abbreviated as "DEGV"), 1.1g of phenothiazine (hereinafter abbreviated as "PTZ") as a primary antioxidant, 1.1g of tris(2,4-di-t-butylphenyl)phosphite (hereinafter abbreviated as "DBPP") as a secondary antioxidant, 0.32g of N-nitrosophenylhydroxyamine ammonium salt (hereinafter abbreviated as "NPHN"), and 2.1g of dibutyltin oxide (hereinafter abbreviated as "DBTO") as a catalyst were charged into the round-bottom flask. The moisture content in AM was 110ppm, and the moisture content in DEGV was 220ppm. Next, the reactor was immersed in an oil bath at 120°C while bubbling a liquid phase of oxygen / nitrogen mixed gas, the oxygen concentration of which was adjusted to 7% by volume, through the gas inlet tube at 15 ml / min, and heating was started under total reflux conditions. As the reaction proceeded, methanol, a by-product, was concentrated at the top of the Oldershaw type rectification column, and after the temperature at the top of the column reached 63°C, which is the azeotropic point of AM and methanol, distillation was started at a reflux ratio of 8 and a withdrawal rate of 50 g / h. At the same time, AM was fed to the reactor through a liquid successive injection line at a rate equal to the distillation rate. The reaction was carried out for 8 hours, with the start of distillation being the start of the reaction (reaction time 0 hours). The reaction solution was sampled 8 hours after the start of the reaction, and the amount of NPH remaining in the reaction solution was measured. The amount of remaining NPH was quantified using high performance liquid chromatography, and the decomposition rate of NPH was calculated from the measured value. The results are shown in Table 1. In Comparative Example 1, the water content in the reaction solution was 156 ppm, and the molar ratio of water to NPH was 5.

[0077] [Comparative Example 2] The decomposition rate of NPH was determined by carrying out the same operation as in Comparative Example 1, except that 0.25 g of ion-exchanged water was additionally added to the raw material solution. The results are shown in Table 1. In Comparative Example 2, the water content in the reaction solution was 390 ppm, and the molar ratio of water to NPH was 11.

[0078] [Comparative Example 3] The decomposition rate of NPH was determined by carrying out the same operation as in Comparative Example 1, except that 0.72 g of ion-exchanged water was additionally added to the raw material solution. The results are shown in Table 1. In Comparative Example 3, the water content in the reaction solution was 820 ppm, and the molar ratio of water to NPH was 24.

[0079] [Comparative Example 4] The decomposition rate of NPH was determined by carrying out the same operation as in Comparative Example 1, except that 1.13 g of ion-exchanged water was additionally added to the raw material solution. The results are shown in Table 1. In Comparative Example 4, the water content in the reaction solution was 1200 ppm, and the molar ratio of water to NPH was 35.

[0080] [Example 1] The decomposition rate of NPH was determined by carrying out the same operation as in Comparative Example 1, except that 1.60 g of ion-exchanged water was additionally added to the raw material solution. The results are shown in Table 1. In Example 1, the water content in the reaction solution was 1640 ppm, and the molar ratio of water to NPH was 48. [Table 1]

[0081] (summary) The results of Comparative Examples 1 to 4 and Example 1 are shown in Table 1, and the correlation (graph) between the water content in the reaction solution and the NPH decomposition rate is shown in Figure 2. It was confirmed that the NPH decomposition rate tends to increase as the water content in the reaction solution increases.

[0082] [Comparative Example 5] In a jacketed reactive distillation reactor, 1364 kg of AM, 997 kg of DEGV, 2.4 kg of PTZ as a primary antioxidant, 2.4 kg of DBPP as a secondary antioxidant, 0.70 kg of NPHN, and 4.6 kg of DBTO as a catalyst were charged. The moisture content in the AM was 93 ppm, and the moisture content in the DEGV was 215 ppm. Next, a mixed gas of oxygen and nitrogen with an oxygen concentration of 7% by volume was introduced at a flow rate of 2 Nm3 While bubbling the mixture at 10000 kPa (1.0 MPa) into the liquid at 1000 K / h, steam was supplied to the jacket under total reflux conditions to start raising the temperature. The reaction temperature was set to 120°C. As the reaction proceeded, methanol, a by-product, was concentrated at the top of the distillation tower, and after the temperature at the top of the tower reached 63°C, which is the azeotropic point of AM and methanol, distillation was started at a reflux ratio of 8 and a flow rate of 110 kg / h. At the same time, AM was fed to the reaction vessel through a liquid successive feeding line at the same flow rate. The reaction was carried out in one batch for 8 hours, with the start of distillation being the start of the reaction (reaction time 0 hours). In addition, in order to prevent polymerization inside the reaction vessel, a 1% by mass PTZ / AM solution was fed from the top of the distillation tower at a flow rate of 11 kg / h. In Comparative Example 5, the water content in the reaction liquid was 144 ppm, and the molar ratio of water to NPH was 4. The above reaction was repeated, and after the seventh reaction (seventh batch), a drop in the liquid delivery flow rate and an overcurrent in the liquid delivery pump were observed when the reaction liquid was transferred to the next process. Therefore, the reaction was stopped and the inside of the reactor was inspected. As a result, a large amount of polymer was found to be attached to the gas phase of the reactor. The results are shown in Table 2.

[0083] [Comparative Example 6] The same reaction as in Comparative Example 5 was repeated except that 1.69 kg of industrial pure water was additionally added to the raw material solution in Comparative Example 5. The water content in the reaction solution in Comparative Example 6 was 857 ppm, and the molar ratio of water to NPH was 25. As a result, after the 12th reaction (12th batch) was completed, a decrease in the liquid delivery flow rate and an overcurrent in the liquid delivery pump were observed when the reaction liquid was transferred to the next process. Therefore, the reaction was stopped and the inside of the reactor was inspected. As a result, a large amount of polymer was found to be attached to the gas phase of the reactor. The results are shown in Table 2.

[0084] [Example 2] The same reaction as in Comparative Example 5 was repeated except that 3.24 kg of industrial pure water was additionally added to the raw material solution in Comparative Example 5. The water content in the reaction solution in Example 2 was 1511 ppm, and the molar ratio of water to NPH was 44. As a result, up until the 60th reaction (60th batch), the reaction liquid was transferred to the next process smoothly without any drop in the liquid delivery flow rate or overcurrent in the liquid delivery pump. After that, the inside of the reactor was inspected, but no polymer adhesion was found in the gas phase of the reactor. The results are shown in Table 2. [Table 2]

[0085] (summary) As mentioned above, it was confirmed that the NPH decomposition rate tends to increase as the water content in the reaction solution increases, and at the actual equipment level, the results showed that the number of continuous production batches could be extended. [Explanation of symbols]

[0086] 1: Raw material solution 2: Waste oil 3: Product (unfinished product) 11: Reactor 21: First distillation tower 31: Second distillation tower 71, 72, 81: Line

Claims

1. A method for producing a (meth)acrylic ester having a vinyl ether group, comprising the step of obtaining a (meth)acrylic ester having a vinyl ether group by transesterification using a raw material solution containing a raw material (meth)acrylic ester, a hydroxyl group-containing vinyl ether compound, a catalyst, an N-nitrosamine (salt), and water, The mass ratio of water in the raw material solution is 1500 ppm or more and 5 mass % or less, and A method for producing a (meth)acrylic ester having a vinyl ether group, characterized in that the molar ratio of water to N-nitrosamine (salt) is 40 or more and 1,100 or less.

2. The hydroxyl group-containing vinyl ether compound is diethylene glycol monovinyl ether, 2. The method for producing a (meth)acrylic ester having a vinyl ether group according to claim 1, wherein the (meth)acrylic ester having a vinyl ether group is 2-(2-vinyloxyethoxy)ethyl (meth)acrylate.

3. 3. The method for producing a (meth)acrylic ester having a vinyl ether group according to claim 1, wherein the N-nitrosamine (salt) is N-nitrosophenylhydroxylamine (salt).

Images