Method for producing (meth)acrylic acid esters

Abstract

The present invention provides technology for improving the yield of a (meth)acrylic acid ester. This (meth)acrylic acid ester production method includes: reacting (meth)acrylic acid and a secondary alcohol within a reactor and in the presence of an acid-type esterification catalyst and a polymerization inhibitor; and bringing a liquid L including an esterification material of the esterification catalyst obtained during production of the (meth)acrylic acid ester into contact with water in the reactor and / or a reservoir tank at a temperature T between 50°C to 105°C inclusive.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a (meth)acrylic acid ester. In particular, the present invention relates to a method for producing a (meth)acrylic acid ester by direct esterification of (meth)acrylic acid with a secondary alcohol. [Background technology]

[0002] It is a known technique to produce a (meth)acrylic acid ester by the esterification reaction between an alcohol and (meth)acrylic acid. This reaction is an equilibrium reaction accompanied by the evolution of water, as shown below.

[0003] [ka]

[0004] In order to shift the equilibrium reaction toward the production of (meth)acrylic esters, it is necessary to remove the water produced during the reaction. However, this reaction is generally accompanied by side reactions that produce impurities. It is preferable to remove these impurities in order to obtain high-purity (meth)acrylic esters that meet the technical requirements for their final use as monomers for the production of polymers that can be used in many fields of application. Furthermore, for economic reasons, it is preferable to recycle, as far as possible, the usable products present in the crude reaction mixture, especially unreacted reactants and catalysts, into the process.

[0005] To achieve these goals, separation / purification processes involving a combination of sequential distillation, extraction and / or settling separations are commonly implemented, but these processes are difficult to implement and energy-expensive, especially due to the presence of azeotropes.

[0006] For example, U.S. Pat. No. 6,072,076 discloses a process for producing alkyl (meth)acrylates by esterifying (meth)acrylic acid with alkanols having chain lengths ranging from 1 to 8 carbon atoms in the presence of an acid esterification catalyst.

[0007] Furthermore, JP-A 2014-534972 (corresponding to the specification of U.S. Patent Application Publication No. 2015 / 0299093) discloses a method for continuously producing 2-octyl acrylate by direct esterification, which method involves the use of a single reactor and recycling of usable compounds, for example, recycling unreacted reaction materials on the one hand and acid catalysts (particularly sulfur-containing acid-type esterification catalysts, especially sulfonic acid-type acid catalysts) on the other hand, thereby continuously producing very pure 2-octyl acrylate in high yield. Summary of the Invention

[0008] However, the method disclosed in U.S. Pat. No. 6,072,076 cannot be applied to the production of (meth)acrylic acid esters by esterification of (meth)acrylic acid with secondary alcohols. This is because secondary alcohols are more susceptible to dehydration reactions resulting in the production of alkenes and water in the presence of an acid catalyst than primary alcohols, such as 2-ethylhexanol. This water production can accumulate when at least a portion of the aqueous phase produced by the esterification reaction is reintroduced into the system, posing the risk of the desired (meth)acrylic acid ester being more easily decomposed into the secondary alcohol and (meth)acrylic acid by hydrolysis. Furthermore, according to U.S. Pat. No. 6,072,076, the crude reaction mixture containing the desired (meth)acrylic acid ester and residual alcohol is purified by distillation in a rectification apparatus with a long residence time in the presence of an acid catalyst. In the case of synthesizing a (meth)acrylic acid ester using a secondary alcohol, there is a problem that this distillation generates alkenes and water, and also decomposes the (meth)acrylic acid ester (i.e., the yield of the (meth)acrylic acid ester is low).

[0009] Furthermore, the technology disclosed in JP 2014-534972 A (corresponding to the specification of U.S. Patent Application Publication No. 2015 / 0299093) has the problem that it is difficult to sufficiently suppress the decomposition of (meth)acrylic acid esters (i.e., the yield of (meth)acrylic acid esters is low).

[0010] As described above, the techniques disclosed in U.S. Pat. No. 6,072,076 and JP 2014-534972 A (corresponding to U.S. Patent Application Publication No. 2015 / 0299093) do not provide a sufficient yield of (meth)acrylic acid esters. Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for improving the yield of (meth)acrylic acid esters.

[0011] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that the above-mentioned problems can be solved by contacting a liquid containing an esterification product of an esterification catalyst, obtained during the production of a (meth)acrylic acid ester, with water at a temperature within a predetermined range in a reactor and / or a residence tank, thereby completing the present invention.

[0012] That is, the above-mentioned object is achieved by a method for producing a (meth)acrylic acid ester, which includes reacting (meth)acrylic acid with a secondary alcohol in a reactor in the presence of an acid-type esterification catalyst and a polymerization inhibitor, and contacting, in the reactor and / or a residence tank, a liquid L containing an esterification product of the esterification catalyst obtained during the production of the (meth)acrylic acid ester with water at a temperature T of 50°C or higher and 105°C or lower. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating one embodiment of a process for producing a (meth)acrylic acid ester. [Figure 2] FIG. 2 is a schematic diagram illustrating another embodiment of the process for producing a (meth)acrylic acid ester. [Figure 3]FIG. 3 is a schematic diagram illustrating another embodiment of the process for producing a (meth)acrylic acid ester. [Figure 4] FIG. 4 is a schematic diagram illustrating another embodiment of the process for producing a (meth)acrylic acid ester. [Figure 5] FIG. 5 is a schematic diagram illustrating another embodiment of the process for producing a (meth)acrylic acid ester. [Figure 6] FIG. 6 is a schematic diagram illustrating another embodiment of the process for producing a (meth)acrylic acid ester. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention provides a method for producing a (meth)acrylic acid ester, which comprises reacting (meth)acrylic acid with a secondary alcohol in a reactor in the presence of an acid-type esterification catalyst and a polymerization inhibitor, and contacting, in the reactor and / or a residence tank, a liquid L containing an esterification product of the esterification catalyst obtained during the production of the (meth)acrylic acid ester with water at a temperature T of 50° C. or higher and 105° C. An object of the present invention is to provide a technology for improving the yield of a (meth)acrylic acid ester.

[0015] Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the claims. Furthermore, the embodiments described in this specification can be arbitrarily combined to form other embodiments.

[0016] In this specification, contacting a liquid L containing an esterified product of an acid-type esterification catalyst obtained during the production of a (meth)acrylic acid ester with water at a temperature T of 50°C or higher and 105°C or lower in a reactor and / or retention tank is also simply referred to as "hot water treatment."

[0017] In this specification, the "acid-type esterification catalyst" may also be simply referred to as "esterification catalyst."

[0018] In this specification, the "esterification product of an acid-type esterification catalyst" may also be simply referred to as the "esterification product of an esterification catalyst."

[0019] As used herein, the term "(meth)acrylic" encompasses both acrylic and methacrylic. Thus, for example, the term "(meth)acrylic acid" encompasses both acrylic acid and methacrylic acid.

[0020] In this specification, unless otherwise specified, measurements of physical properties etc. are carried out at room temperature (25±5°C).

[0021] Terms used herein should be understood to be used in the sense commonly used in the art unless otherwise specified. Therefore, unless otherwise defined, all technical terms and chemical technical terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. In the event of a conflict, the present specification (including definitions) shall prevail. Throughout this specification, singular expressions should be understood to include the concept of the plural form unless otherwise specified. Therefore, singular articles (for example, in English, "a," "an," "the," etc.) should be understood to include the concept of the plural form unless otherwise specified.

[0022] The present invention is characterized in that a liquid containing an esterified product of an esterification catalyst obtained during the production of a (meth)acrylic acid ester is brought into contact with water at a predetermined temperature range in a reactor and / or a residence tank. This configuration can improve the yield of the (meth)acrylic acid ester. The detailed mechanism by which this effect is achieved remains unclear, but is thought to be as follows.

[0023] The present inventors have found that an esterification product of the esterification catalyst is formed during the production of a (meth)acrylic acid ester, and when the esterification product of the esterification catalyst is introduced into a refinery tower and subjected to thermal load, it decomposes into the esterification catalyst and a secondary alcohol. The present inventors have speculated that the esterification product of the esterification catalyst is formed by, for example, the reaction of the secondary alcohol and / or an alkene produced by an intramolecular dehydration reaction of the secondary alcohol with the esterification catalyst.

[0024] The present inventors have also found that the yield and purity of the (meth)acrylic acid ester tend to increase as the amount of secondary alcohol in the product obtained after thermal aging of a product containing a (meth)acrylic acid ester decreases. The present inventors speculated that the esterification product of the esterification catalyst is decomposed into the esterification catalyst and the secondary alcohol in the final product column, and the esterification catalyst dehydrates the secondary alcohol to produce an alkene and water, and that the produced water hydrolyzes the (meth)acrylic acid ester to produce the secondary alcohol and (meth)acrylic acid, thereby reducing the yield of the (meth)acrylic acid ester.

[0025] As a result of further intensive investigation into the above facts and speculation, the present inventors have found that the esterification product of the esterification catalyst can be decomposed by contacting a liquid containing the esterification product of the esterification catalyst obtained during the production of a (meth)acrylic ester with water at a temperature within a predetermined range before the (meth)acrylic ester is introduced into the final product column. Decomposition of the esterification product of the esterification catalyst facilitates removal of the esterification catalyst. As a result, the decomposition rate of the (meth)acrylic ester in the final product column is reduced, and the yield of the final product (meth)acrylic ester can be improved. Note that the above mechanism is speculation and does not limit the technical scope of the present invention.

[0026] In this specification, the term "reactor and / or retention tank" refers to a reactor, a retention tank, both of these, or a tank that functions as both a reactor and a retention tank (for example, a reactor that functions as a retention tank as shown in FIGS. 2 and 4 described below). In one embodiment of the present invention, the contacting of a liquid L containing an ester of an esterification catalyst obtained during the production of a (meth)acrylic acid ester with water at a temperature T of 50°C or higher and 105°C or lower is preferably carried out in a retention tank or a reactor that functions as a retention tank, and more preferably in a retention tank.

[0027] When liquid L containing an esterified product of an esterification catalyst obtained during the production of a (meth)acrylic acid ester (also simply referred to as "liquid L" in this specification) is brought into contact with water in a reactor and / or residence tank, the water may be in a liquid state, a gaseous state (water vapor), or a combination thereof. When liquid L is brought into contact with water at a temperature within a predetermined range, liquid L may be brought into contact with liquid water at a temperature above 100°C, for example, in a pressurized environment.

[0028] In one embodiment of the present invention, the method for producing a (meth)acrylic acid ester may include introducing water in the form of a liquid, a gas, or a combination thereof (i.e., part or all of the water to be contacted with the liquid L) into a reactor and / or a residence tank while distilling off water (while distilling a mixture containing water).

[0029] As described above, the method for producing a (meth)acrylic acid ester according to the present invention includes contacting a liquid L with water in a reactor and / or a residence tank at a temperature T of 50°C or higher and 105°C or lower. If the temperature T is only lower than 50°C, the yield of the (meth)acrylic acid ester will be insufficient. If the temperature T is only higher than 105°C, there is a risk of being disadvantageous in terms of cost.

[0030] The temperature T is not particularly limited, but is preferably 55°C or higher and 105°C or lower, more preferably 60°C or higher and 105°C or lower, even more preferably 65°C or higher and 105°C or lower, even more preferably 70°C or higher and 105°C or lower, even more preferably 75°C or higher and 105°C or lower, even more preferably 80°C or higher and 105°C or lower, even more preferably higher than 80°C and 105°C or lower, even more preferably 85°C or higher and 105°C or lower, and particularly preferably 95°C or higher and 105°C or lower. By contacting the liquid L with water in the reactor and / or retention tank at a temperature T within these ranges, the yield of the (meth)acrylic acid ester is further improved. Furthermore, the (meth)acrylic acid ester can be produced in a higher yield in a shorter period of time.

[0031] In this specification, the temperature T refers to "the temperature when the liquid L is brought into contact with water in the reactor and / or retention tank," and specifically refers to the temperature of the mixture containing the liquid L and water in the reactor and / or retention tank. The temperature of the mixture containing the liquid L and water in the reactor and / or retention tank is measured by a thermometer installed in the reactor and / or retention tank.

[0032] In this specification, the phrase "the method for producing a (meth)acrylic acid ester includes contacting liquid L with water in a reactor and / or retention tank at a temperature T within a predetermined range" means "as long as the method includes contacting liquid L with water in a reactor and / or retention tank at a temperature T within the range, the method may further include contacting liquid L with water in the reactor and / or retention tank at a temperature outside the range."

[0033] The contact of liquid L with water in the reactor and / or retention tank may include, when a temperature within a predetermined range is set as the set temperature, contacting the liquid L with the water for a retention time within a predetermined range while maintaining the temperature T at the set temperature within ±5°C of the set temperature (herein, "within ±5°C of the set temperature" means "within a range of -5°C or higher and +5°C or lower of the set temperature"). For example, in a method for producing a (meth)acrylic acid ester according to a preferred embodiment of the present invention, the contact of liquid L with water in the reactor and / or retention tank includes, when a temperature within a predetermined range is set as the set temperature, contacting the liquid L with the water for a retention time of 0.5 hours to 100 hours while maintaining the temperature T at the set temperature within ±5°C of the set temperature (herein, "within ±5°C of the set temperature" means "within a range of -5°C or higher and +5°C or lower of the set temperature").

[0034] In this specification, the retention time refers to "the time during which the temperature of the mixture (temperature T) containing liquid L and water in the reactor and / or retention tank is maintained within a range of ±5°C of the set temperature, starting from the time when the temperature of the mixture (temperature T) reaches a range of ±5°C of the set temperature." The end point of the retention time is the time when temperature T goes out of the range of ±5°C of the set temperature.

[0035] In this specification, when one set temperature is selected, if there are two or more periods during which the temperature of a mixture containing liquid L and water (temperature T) is maintained within a range of the set temperature ±5°C, with a period outside this range in between, the maintenance time at the set temperature is treated as the sum of the two or more periods during which the temperature is maintained within a range of the set temperature ±5°C.

[0036] For example, when 90°C is selected as one set temperature, if there is only one time period during which the temperature T is maintained within the range of 85°C or more and 95°C or less, and if that time period is 10 hours, then the holding time at the set temperature of 90°C will be 10 hours.

[0037] For example, when 90°C is selected as one set temperature, if there are two periods during which the temperature T is maintained within the range of 85°C or more and 95°C or less, separated by a period during which the temperature T is outside this range, and if the two periods during which the temperature T is maintained within the range of 85°C or more and 95°C or less are 2 hours and 8 hours, respectively, then the holding time at the set temperature of 90°C will be 10 hours.

[0038] The set temperature may be changed during contact between the liquid L and water in the reactor and / or retention tank. That is, only one set temperature may be selected, or two or more set temperatures may be selected. When changing the set temperature, if two or more identical set temperatures are selected so that the times at which these two or more identical set temperatures are set are discontinuous, these two or more identical set temperatures are treated as different set temperatures, and the retention times at the set temperatures within a predetermined temperature range are calculated.

[0039] When contacting liquid L with water in a reactor and / or retention tank, if only one set temperature is selected within a predetermined temperature range, the retention time at that set temperature is the retention time at the set temperature within that predetermined temperature range.

[0040] For example, when the set temperature range is 55°C or more and 100°C or less, and only one temperature is selected as the set temperature for contact between liquid L and water in the reactor and / or retention tank, and the set temperature is 90°C, if the holding time at the set temperature of 90°C (the time at 85°C or more and 95°C or less, i.e., the time when temperature T is 85°C or more and 95°C or less) is 10 hours, then the holding time at the set temperature within the range of 55°C or more and 100°C or less will be 10 hours.

[0041] In this specification, when the set temperature is changed during contact between the liquid L and water in the reactor and / or retention tank, and two or more temperatures are selected as the set temperature, the retention time at the set temperature within a predetermined temperature range is treated as follows.

[0042] When changing the set temperature, if two or more set temperatures are selected within a predetermined temperature range, the sum of the holding times at each selected set temperature is treated as the holding time at the set temperature within the predetermined temperature range. Also, when changing the set temperature, if one or more set temperatures are selected within a predetermined temperature range and one or more set temperatures outside the predetermined temperature range are selected, the sum of the holding times at each set temperature selected within the predetermined temperature range (or, if there is only one such time, that time) is treated as the holding time at the set temperature within the predetermined temperature range.

[0043] The start and end points of the holding time at each set temperature are the same as those described above. However, there may be cases where part or all of the time from when the set temperature is changed to when the temperature T first leaves the range of ±5°C of the set temperature before the change overlaps with part or all of the holding time at another set temperature. If such overlapping time exists, the holding time at a set temperature within a specified temperature range is calculated by subtracting this overlapping time from the total holding time at each set temperature within that specified temperature range.

[0044] The retention time (retention time at a set temperature within a predetermined temperature range) is not particularly limited, but is preferably 0.1 hours or more, more preferably 0.5 hours or more, even more preferably 1 hour or more, even more preferably 3 hours or more, even more preferably 5 hours or more, and particularly preferably 10 hours or more. Within this range, the yield of the (meth)acrylic acid ester is further improved. The retention time at a set temperature within the predetermined temperature range is not particularly limited, but is preferably 100 hours or less, more preferably 70 hours or less, even more preferably 50 hours or less, even more preferably 40 hours or less, even more preferably 30 hours or less, even more preferably 20 hours or less, and particularly preferably 10 hours or less. Within these ranges, the (meth)acrylic acid ester can be produced in a shorter period of time. Note that, in a preferred embodiment, examples of the range of the retention time include any combination selected from these upper and lower limits. In a preferred embodiment, the range of the retention time is, for example, 0.1 to 100 hours, 0.5 to 100 hours, 1 to 100 hours, 3 to 100 hours, 5 to 100 hours, 10 to 100 hours, 1 to 70 hours, 3 to 70 hours, 5 to 70 hours, 10 to 70 hours, 1 to 50 hours, 3 to 50 hours, 5 to 10 hours, 10 hours or less Examples of retention times include, but are not limited to, 1 hour to 50 hours, 1 hour to 40 hours, 3 hours to 40 hours, 5 hours to 10 hours, 10 hours to 40 hours, 1 hour to 30 hours, 3 hours to 30 hours, 5 hours to 30 hours, 10 hours to 30 hours, 1 hour to 20 hours, 3 hours to 20 hours, 5 hours to 20 hours, 1 hour to 10 hours, 3 hours to 10 hours, and 5 hours to 10 hours.

[0045] The set temperature is preferably in the range of 50°C to 100°C, more preferably 55°C to 100°C, even more preferably 60°C to 100°C, even more preferably 65°C to 100°C, even more preferably 70°C to 100°C, even more preferably 75°C to 100°C, even more preferably more than 75°C to 100°C, even more preferably more than 80°C to 100°C, even more preferably more than 80°C to 100°C, even more preferably more than 85°C to 100°C, even more preferably more than 90°C to 100°C, and particularly preferably 95°C to 100°C. When the set temperature is within these ranges, the yield of the (meth)acrylic acid ester is further improved by contacting the liquid L with water in the reactor and / or retention tank while maintaining the temperature T within ±5°C of the set temperature. Furthermore, the (meth)acrylic acid ester can be produced in a shorter period of time and in a higher yield.

[0046] It is preferable to select only one set temperature and one holding time.

[0047] As described above, the contact of liquid L with water in a reactor and / or retention tank may include, when a temperature within a predetermined range is set as the set temperature, contacting the liquid L with the water for a retention time within a predetermined range while maintaining the temperature T within a range of the set temperature ±5°C (a range of not less than -5°C of the set temperature and not more than +5°C of the set temperature). For example, in a preferred embodiment of the present invention, the contact of liquid L with water in a reactor and / or retention tank in the method for producing a (meth)acrylic acid ester includes, when a temperature within a range of not less than 55°C and not more than 100°C of the set temperature, contacting the liquid L with the water for a retention time of not less than 0.5 hours and not more than 100 hours while maintaining the temperature T within a range of not less than ±5°C of the set temperature (a range of not less than -5°C of the set temperature and not more than +5°C of the set temperature). In addition, these embodiments may include selecting a set temperature within these temperature ranges and contacting the liquid L with water, and may further include selecting a set temperature outside these temperature ranges and contacting the liquid L with water.

[0048] Examples of preferred combinations of the set temperature and the holding time include a combination of a set temperature in the range of 50°C or higher and 100°C or lower, and a holding time of 0.1 hour or higher and 100 hours or lower while maintaining the temperature T within the set temperature ±5°C; a combination of a set temperature in the range of 55°C or higher and 100°C or lower, and a holding time of 0.1 hour or higher and 70 hours or lower while maintaining the temperature T within the set temperature ±5°C; combinations of set temperatures in the range of 55°C to 100°C and hold times of 1 hour to 70 hours with temperature T maintained within ±5°C of the set temperature; combinations of set temperatures in the range of 55°C to 100°C and hold times of 5 hours to 70 hours with temperature T maintained within ±5°C of the set temperature; combinations of set temperatures in the range of 60°C to 100°C and hold times of 0.1 hour to 70 hours with temperature T maintained within ±5°C of the set temperature. combination of a set temperature in the range of 60°C or higher and 100°C or lower, and a holding time of 0.5 hours or higher and 70 hours or lower while maintaining temperature T within the set temperature ±5°C; a set temperature in the range of 60°C or higher and 100°C or lower, and a holding time of 5 hours or higher and 70 hours or lower while maintaining temperature T within the set temperature ±5°C; a set temperature in the range of 65°C or higher and 100°C or lower, and a holding time of 0.1 hours or higher and 70 hours or lower while maintaining temperature T within the set temperature ±5°C; A combination of a set temperature within a range of 0°C or less, and a holding time of 0.5 to 70 hours while maintaining temperature T within a range of the set temperature ±5°C; a combination of a set temperature within a range of 65°C or more and 100°C or less, and a holding time of 1 to 70 hours while maintaining temperature T within a range of the set temperature ±5°C; a combination of a set temperature within a range of 65°C or more and 100°C or less, and a holding time of 0.1 to 50 hours while maintaining temperature T within a range of the set temperature ±5°C; a set temperature within a range of 65°C or more and 100°C or less;and a holding time of 0.5 hours to 50 hours while maintaining temperature T within the set temperature ±5°C range; a set temperature within the range of 65°C to 100°C and a holding time of 3 hours to 50 hours while maintaining temperature T within the set temperature ±5°C range; a set temperature within the range of 65°C to 100°C and a holding time of 5 hours to 70 hours while maintaining temperature T within the set temperature ±5°C range; a set temperature within the range of 70°C to 100°C and a holding time of 5 hours to 70 hours while maintaining temperature T within the set temperature ±5°C range. combinations of a set temperature in the range of 70°C to 100°C and a holding time of 0.5 hours to 50 hours with temperature T maintained within ±5°C of the set temperature; combinations of a set temperature in the range of 70°C to 100°C and a holding time of 5 hours to 50 hours with temperature T maintained within ±5°C of the set temperature; combinations of a set temperature in the range of 70°C to 100°C and a holding time of 5 hours to 50 hours with temperature T maintained within ±5°C of the set temperature; combinations of a set temperature in the range of 75°C to 100°C and a holding time of 0.1 hours or more with temperature T maintained within ±5°C of the set temperature A combination of a holding time of 40 hours or less, a combination of a set temperature in the range of 75°C or more and 100°C or less, and a holding time of 1 hour or more and 40 hours or less while maintaining temperature T within the set temperature ±5°C, a combination of a set temperature in the range of 75°C or more and 100°C or less, and a holding time of 3 hours or more and 40 hours or less while maintaining temperature T within the set temperature ±5°C, a combination of a set temperature in the range of 75°C or more and 100°C or less, and a holding time of 5 hours or more and 40 hours or less while maintaining temperature T within the set temperature ±5°C, A combination of a set temperature in the range of more than 75°C and less than 100°C, and a holding time of 0.1 to 40 hours while maintaining the temperature T within the set temperature ±5°C; a set temperature in the range of more than 75°C and less than 100°C, and a holding time of 1 to 40 hours while maintaining the temperature T within the set temperature ±5°C; a set temperature in the range of more than 75°C and less than 100°C, and a holding time of 5 to 40 hours while maintaining the temperature T within the set temperature ±5°C; a set temperature in the range of more than 80°C and less than 100°C;and a holding time of 0.1 to 40 hours while maintaining temperature T within the set temperature ±5°C; a set temperature within the range of 80°C to 100°C and a holding time of 1 to 40 hours while maintaining temperature T within the set temperature ±5°C; a set temperature within the range of 80°C to 100°C and a holding time of 5 to 40 hours while maintaining temperature T within the set temperature ±5°C; a set temperature within the range of more than 80°C to 100°C and a holding time of 5 to 40 hours while maintaining temperature T within the set temperature ±5°C; A combination of a set temperature in the range of more than 80°C and less than 100°C, and a holding time of 3 hours or more and less than 40 hours with temperature T maintained within ±5°C of the set temperature; a combination of a set temperature in the range of more than 80°C and less than 100°C, and a holding time of 1 hour or more and less than 30 hours with temperature T maintained within ±5°C of the set temperature; a combination of a set temperature in the range of more than 80°C and less than 100°C, and a holding time of 5 hours with temperature T maintained within ±5°C of the set temperature combinations of a set temperature in the range of 85°C to 100°C and a holding time of 1 hour to 40 hours with temperature T maintained within ±5°C of the set temperature; combinations of a set temperature in the range of 85°C to 100°C and a holding time of 3 hours to 40 hours with temperature T maintained within ±5°C of the set temperature; combinations of a set temperature in the range of 85°C to 100°C and a holding time of 1 hour to 30 hours with temperature T maintained within ±5°C of the set temperature; A combination of a set temperature in the range of 85°C or higher and 100°C or lower, and a holding time of 5 hours or higher and 30 hours or lower while maintaining temperature T within the set temperature ±5°C; a combination of a set temperature in the range of 90°C or higher and 100°C or lower, and a holding time of 1 hour or higher and 30 hours or lower while maintaining temperature T within the set temperature ±5°C; a set temperature in the range of 90°C or higher and 100°C or lower, and a holding time of 5 hours or higher and 30 hours or lower while maintaining temperature T within the set temperature ±5°C; a set temperature in the range of 95°C or higher and 100°C or lower;and a holding time of 1 hour to 20 hours while maintaining temperature T within the range of the set temperature ±5°C; a set temperature within the range of 95°C to 100°C and a holding time of 3 hours to 20 hours while maintaining temperature T within the range of the set temperature ±5°C; a set temperature within the range of 95°C to 100°C and a holding time of 5 hours to 20 hours while maintaining temperature T within the range of the set temperature ±5°C; a set temperature within the range of 95°C to 100°C and a holding time of 5 hours to 20 hours while maintaining temperature T within the range of the set temperature ±5°C; Examples of such a combination include a combination of a set temperature within ±5°C for a holding time of 1 hour to 10 hours, a set temperature within ±5°C for a set temperature of 95°C to 100°C for a holding time of 3 hours to 10 hours, and a set temperature within ±5°C for a set temperature of 95°C to 100°C for a holding time of 5 hours to 10 hours. However, the combinations of set temperatures and holding times are not limited to these. Contact between the liquid L and water in the reactor and / or retention tank may include contact between the liquid L and water at a set temperature within these temperature ranges, as long as the contact between the liquid L and water is carried out at a set temperature outside these temperature ranges.

[0049] In one embodiment of the present invention, in the method for producing a (meth)acrylic acid ester, contacting liquid L with water in a reactor and / or residence tank preferably includes contacting the liquid L with water for 0.1 hours or longer while maintaining temperature T within a range of 50°C or higher and 105°C or lower. In this embodiment, the temperature range in which temperature T is maintained is more preferably 55°C or higher and 105°C or lower, even more preferably 65°C or higher and 105°C or lower, even more preferably 75°C or higher and 105°C or lower, even more preferably higher than 80°C and 105°C or lower, even more preferably 85°C or higher and 105°C or lower, and particularly preferably 95°C or higher and 105°C or lower. In this embodiment, the time for which temperature T is maintained is more preferably 0.5 hours or longer, even more preferably 3 hours or longer.

[0050] In one embodiment of the present invention, the contact between the liquid L and water in the reactor and / or residence tank in the method for producing a (meth)acrylic acid ester preferably includes at least one selected from the group consisting of the following (i), (ii), (iii), (iv), and (v), more preferably includes at least one selected from the group consisting of the following (iii), (iv), and (v), further preferably includes at least one selected from the group consisting of the following (iv) and (v), and particularly preferably includes the following (v): (i) contacting the liquid L with the water for a period of 5 hours to 70 hours while maintaining a temperature T in the range of 55°C to 65°C; (ii) contacting the liquid L with the water for a period of 5 hours to 100 hours while maintaining a temperature T in the range of 65°C to 75°C; (iii) contacting the liquid L with the water for a period of 0.5 hours to 40 hours while maintaining a temperature T in the range of 75°C to 85°C; (iv) contacting the liquid L with the water for a period of 0.5 hours to 25 hours while maintaining a temperature T in the range of 85°C to 95°C; (v) The liquid L is brought into contact with the water for a period of 0.1 to 10 hours while maintaining a temperature T within a range of 95°C to 105°C.

[0051] In the case of (i) above, the time (the time during which liquid L and water are contacted while maintaining a temperature T in the range of 55°C to 65°C) is preferably 45 hours to 70 hours. In the case of (ii) above, the time (the time during which liquid L and water are contacted while maintaining a temperature T in the range of 65°C to 75°C) is preferably 35 hours to 45 hours. In the case of (iii) above, the time (the time during which liquid L and water are contacted while maintaining a temperature T in the range of 75°C to 85°C) is preferably 20 hours to 40 hours, more preferably 25 hours to 35 hours. In the case of (iv) above, the time (the time during which liquid L and water are contacted while maintaining a temperature T in the range of 85°C to 95°C) is preferably 10 hours to 25 hours. In (vi), the time (the time during which the liquid L is brought into contact with water while maintaining the temperature T within the range of 95°C to 105°C) is preferably from 0.5 hours to 10 hours, more preferably from 1 hour to 10 hours, even more preferably from 3 hours to 10 hours, and particularly preferably from 5 hours to 10 hours.

[0052] In these embodiments, the contacting of liquid L with water in the reactor and / or residence tank includes contacting liquid L with water while maintaining temperature T within these temperature ranges, and may further include contacting liquid L with water while temperature T is outside these temperature ranges.

[0053] If these relationships are satisfied, the (meth)acrylic acid ester can be produced in a short period of time and in a high yield.

[0054] When a temperature within a predetermined range is set as the set temperature, the ratio of the retention time (the retention time at which the temperature within the predetermined range is set as the set temperature) to the time (hereinafter also referred to as "elapsed time"), starting from the time when the temperature (temperature T) of the mixture containing liquid L and water in the reactor and / or retention tank first reaches a range within ±5°C of the set temperature and ending from the time when the temperature T goes from within ±5°C of the set temperature to outside of ±5°C of the set temperature, is not particularly limited. However, the ratio of the retention time to the elapsed time is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more (upper limit 100%). By keeping the retention time within this range, the hot water treatment can be carried out efficiently.

[0055] When the set temperature is changed and two or more set temperatures are selected within a specified temperature range, the elapsed time is defined as the time when the temperature T first reaches a range within ±5°C of the initially set temperature within the specified temperature range, and the time when the temperature T changes from within ±5°C of the last set temperature within the specified temperature range to outside that range for the last time.

[0056] The mass ratio of water to the total mass of liquid L and water contacted in the reactor and / or retention tank is not particularly limited, but is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more (upper limit: less than 100% by mass). The mass ratio of water to the total mass of liquid L and water contacted in the reactor and / or retention tank is not particularly limited, but is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 60% by mass or less (lower limit: more than 0% by mass). The mass ratio of water to the total mass of liquid L and water contacted in the reactor and / or retention tank may be, for example, 50% by mass or less, or 40% by mass or less. Within these ranges, the decomposition rate of the esterified product of the esterification catalyst is improved. Furthermore, the yield of the (meth)acrylic acid ester is further improved. Furthermore, since a predetermined decomposition rate of the esterified product of the esterification catalyst is reached in a shorter time, the productivity of the (meth)acrylic acid ester is further improved. Therefore, preferred examples of the mass ratio of water relative to the total mass of liquid L and water include 10% by mass or more and 90% by mass or less, 15% by mass or more and 85% by mass or less, 20% by mass or more and 80% by mass or less, 25% by mass or more and 80% by mass or less, 30% by mass or more and 80% by mass or less, 20% by mass or more and 60% by mass or less, 25% by mass or more and 60% by mass or less, 30% by mass or more and 60% by mass or less, 40% by mass or more and 60% by mass or less, 30% by mass or more and 50% by mass or less, and 30% by mass or more and 40% by mass or less, but the mass ratio of water relative to the total mass of liquid L and water is not limited to these.

[0057] The flash point of the (meth)acrylic acid ester produced is not particularly limited. However, for example, when 1-methylheptyl acrylate is produced, the flash point of the 1-methylheptyl acrylate produced is preferably 90°C or higher, more preferably 92°C or higher, even more preferably 93°C or higher, and particularly preferably higher than 93°C (the upper limit is the flash point of pure 1-methylheptyl acrylate). The flash point of the (meth)acrylic acid ester can be determined using a Cleveland open-type method.

[0058] The higher the purity of the (meth)acrylic acid ester produced, the more preferable, and it is particularly preferably 99.9% by mass or more (upper limit: 100% by mass). That is, a method for producing a (meth)acrylic acid ester according to a preferred embodiment of the present invention can produce a (meth)acrylic acid ester with a purity of 99.9% by mass or more. For example, when the (meth)acrylic acid ester is 1-methylheptyl acrylate or 1-methylheptyl methacrylate, the purity of the (meth)acrylic acid ester is preferably 99.9% by mass or more, more preferably 99.92% by mass or more, and even more preferably 99.94% by mass or more (upper limit: 100% by mass).

[0059] In one embodiment of the present invention, a method for producing 1-methylheptyl acrylate includes contacting a liquid L containing an esterification product of an esterification catalyst obtained during the production of 1-methylheptyl acrylate with water in a reactor and / or residence time tank at a temperature T of 50°C or higher and 105°C or lower, followed by purification to remove low-boiling substances (e.g., substances having a boiling point lower than that of 1-methylheptyl acrylate) and high-boiling substances (e.g., substances having a boiling point higher than that of 1-methylheptyl acrylate). When the liquid L is a liquid obtained by subjecting a reaction mixture containing 1-methylheptyl acrylate and an esterification product of the esterification catalyst to a neutralization treatment, a water-washing treatment, and, if necessary, an organic solvent-cutting treatment (e.g., a toluene-cutting treatment), the purity of 1-methylheptyl acrylate can be calculated, for example, by the following formula. Here, the liquid L is preferably a liquid obtained by subjecting a reaction mixture containing 1-methylheptyl acrylate and an esterification product of the esterification catalyst to a neutralization treatment, a water-washing treatment, and an organic solvent-cutting treatment (e.g., a toluene-cutting treatment).

[0060]

number

[0061] In the calculation of the above formula, the content of 2-octene in 1-methylheptyl acrylate and the content of 2-octanol in 1-methylheptyl acrylate can be quantified using gas chromatography (GC), and the acid content in 1-methylheptyl acrylate can be quantified by neutralization titration.

[0062] The decomposition rate of the esterified product of the esterification catalyst resulting from contacting the liquid L with water at the temperature T in the reactor and / or residence tank is not particularly limited, but is preferably as high as possible from the viewpoints of the yield and purity of the (meth)acrylic acid ester.

[0063] In the method for producing a (meth)acrylic acid ester according to the present invention, details of the (meth)acrylic acid, secondary alcohol, acid-type esterification catalyst, and polymerization inhibitor used in the synthesis of the (meth)acrylic acid ester, as well as the type and amount of organic solvent added as needed, are the same as those described in the step (a) below. Furthermore, details of the reaction, such as the reaction conditions for the (meth)acrylic acid ester, in the method for producing a (meth)acrylic acid ester according to the present invention are the same as those described in the step (a) below.

[0064] An embodiment of the method for producing a (meth)acrylic acid ester according to the present invention will be described below with reference to Figures 1 to 6. However, the method for producing a (meth)acrylic acid ester according to the present invention is not limited to the following embodiment.

[0065] One embodiment of the present invention is a method for producing a (meth)acrylic acid ester, which includes the following (a), (b), (c), (d), and (e). A schematic diagram of the production process of this embodiment is shown in Figure 1.

[0066] (a) supplying an acid-type esterification catalyst, (meth)acrylic acid, a secondary alcohol, and a polymerization inhibitor (and, if used, other components (e.g., an organic solvent, etc.)) to a reactor 1, and reacting the (meth)acrylic acid with the secondary alcohol in the presence of the esterification catalyst and the polymerization inhibitor, while distilling water produced by the esterification reaction as an azeotropic composition with the secondary alcohol and / or, if used, an organic solvent (the secondary alcohol, the organic solvent, if used, or a combination thereof) from the top of a first distillation column 2, and condensing the obtained distillate and allowing it to stand to separate it into an oil phase and an aqueous phase, while obtaining a reaction mixture A containing a (meth)acrylic acid ester and an esterification product of the esterification catalyst (an esterification product of the acid-type esterification catalyst) in the reactor 1 (step (a)); (b) The reaction mixture A is withdrawn from the bottom of the reactor 1 and supplied to a retention tank 3. The reaction mixture A is neutralized (neutralization treatment) and washed with water (water-washing treatment) in the retention tank 3 to obtain a mixture M1 (the mixture after neutralization and water-washing). The mixture M1 is separated into an oil phase O1 and an aqueous phase W1. The aqueous phase W1 is removed from the retention tank 3 to leave the oil phase O1 in the retention tank 3. If necessary, the oil phase O1 is subjected to a heat treatment, an organic solvent-removing treatment, or a combination thereof. In the retention tank 3, an oil phase (the oil phase O1, or the oil phase O1 that has been subjected to a heat treatment, an organic solvent-removing treatment, or a combination thereof) (here, the oil phase corresponds to liquid L because it contains an esterification product of an acid-type esterification catalyst) is separated from the mixture M1. ) with water while contacting and retaining it at a temperature T of 50°C or higher and 105°C or lower to obtain a mixture M2 (mixture after hot water treatment), separating the mixture M2 into an oil phase O2 and an aqueous phase W2, removing the aqueous phase W2 from the retention tank 3, optionally subjecting the oil phase O2 to a heat treatment, an organic solvent removal treatment, or a combination thereof, and optionally recovering the resulting gas and / or condensate from the retention tank 3 (recovering the resulting gas, condensate, or a combination thereof from the retention tank 3 as necessary), and obtaining the residue in the retention tank 3 (the oil phase O2, or the oil phase O2 that has been subjected to a heat treatment, an organic solvent removal treatment, or a combination thereof) as a reaction mixture B (step (b)); (c) supplying the reaction mixture B to a second distillation column 4 and distilling it to separate it into a bottom liquid of the second distillation column 4 containing a (meth)acrylic acid ester and a recovered alcohol (step (c)); (d) withdrawing the bottom liquid of the second distillation column 4 from the bottom of the second distillation column 4, supplying it to a third distillation column 5, and distilling it to separate it into a purified (meth)acrylic acid ester as a final product and a bottom liquid of the third distillation column 5, and withdrawing the purified (meth)acrylic acid ester from the top of the third distillation column 5 (step (d)); (e) The bottom liquid of the third distillation column 5 is withdrawn from the bottom of the third distillation column 5, supplied to a treatment device 6, and separated into a recovered (meth)acrylic acid ester and waste oil (step (e)).

[0067] In this embodiment, a conventionally known method can be used in the same manner or with appropriate modifications, and is not limited to the following embodiment.

[0068] [Process (a)] In this step, (meth)acrylic acid, a secondary alcohol, an acid-type esterification catalyst, a polymerization inhibitor, and, if necessary, an organic solvent (reaction materials) are supplied to reactor 1 via pipe 11a. Other compounds may also be supplied to reactor 1. While FIG. 1 shows (meth)acrylic acid, a secondary alcohol, an acid-type esterification catalyst, a polymerization inhibitor, and, if necessary, an organic solvent, all being supplied via the same pipe 11a, they may also be supplied via separate pipes. Specifically, (meth)acrylic acid may be directly introduced into the reactor via pipe 11a, and the acid-type esterification catalyst and polymerization inhibitor may be directly introduced into the reactor via separate pipes (not shown). A portion of the secondary alcohol may be directly introduced into the reactor via a separate pipe, and another portion may be introduced into the top of first distillation column 2 via separate pipe 11c to ensure column reflux. Alternatively, as described in detail below, recovered alcohol (a secondary alcohol-rich fluid) obtained from second distillation column 4 (a subsequent purification stage) may be supplied to reactor 1 via pipe 11b. Alternatively, as will be described in detail below, the recovered (meth)acrylic acid ester obtained from the treatment device 6 may be supplied to the reactor 1 via pipes 64 and 11b.

[0069] Examples of the acid-type esterification catalyst (esterification catalyst) include sulfur-containing acid-type esterification catalysts and acidic cation exchange resins. Among these, examples of sulfur-containing acid-type esterification catalysts include sulfur-containing acid compounds such as sulfuric acid and organic sulfonic acids. Examples of sulfur-containing acid compounds include sulfuric acid, para-toluenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, dodecylsulfonic acid, and xylenesulfonic acid. The acidic cation exchange resin is not limited by its physical properties, such as resin structure, degree of crosslinking, or a combination thereof. For example, porous or gel-type strong acidic cation exchange resins, weak acidic cation exchange resins, and the like can be used, with porous or gel-type strong acidic cation exchange resins being preferred. Examples of porous strongly acidic cation exchange resins include MSC-1 (manufactured by Dow), PK-208, PK-212, PK-216, PK-220, and PK-228 (all manufactured by Mitsubishi Chemical Corporation), Amberlyst (registered trademark)-16, IR-116, IR-118, IR-122, C-26, C-26TR, C-264, and C-265 (all manufactured by Rohm and Haas Company), SPC-108 and SPC-112 (all manufactured by Bayer), and KC-470 (manufactured by Sumitomo Chemical Co., Ltd.). Examples of gel-type strongly acidic cation exchange resins include HCR-S, HCR-W2, and HGR-W2 (all manufactured by Dow Chemical), SK-1B, SK-106, and SK-110 (all manufactured by Mitsubishi Chemical Corporation), Duolite (registered trademark) C20H and C255LFH (all manufactured by Rohm and Haas), and K1221 and K1431 (all manufactured by Bayer). These esterification catalysts may be used alone or in combination of two or more. Among these, in terms of ease of handling and cost, acid-type esterification catalysts containing sulfur are preferred, and sulfuric acid, para-toluenesulfonic acid, and methanesulfonic acid are preferred.The acid-type esterification catalyst preferably contains a sulfur-containing acid-type esterification catalyst, more preferably contains a sulfur-containing acid compound, even more preferably contains at least one compound selected from the group consisting of sulfuric acid and organic sulfonic acids, still more preferably contains at least one compound selected from the group consisting of sulfuric acid, para-toluenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, dodecylsulfonic acid, and xylenesulfonic acid, and particularly preferably contains at least one compound selected from the group consisting of sulfuric acid, para-toluenesulfonic acid, and methanesulfonic acid. The acid-type esterification catalyst is preferably at least one selected from the group consisting of sulfur-containing acid-type esterification catalysts and acidic cation exchange resins, more preferably sulfur-containing acid-type esterification catalysts, even more preferably sulfur-containing acid compounds, even more preferably at least one compound selected from the group consisting of sulfuric acid and organic sulfonic acids, even more preferably at least one compound selected from the group consisting of sulfuric acid, para-toluenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, dodecylsulfonic acid, and xylenesulfonic acid, and particularly preferably at least one compound selected from the group consisting of sulfuric acid, para-toluenesulfonic acid, and methanesulfonic acid. The amount of the esterification catalyst added is, for example, 0.5 to 10 parts by mass, preferably 1 to 5 parts by mass, per 100 parts by mass of (meth)acrylic acid. When two or more esterification catalysts are used in combination, the amount of the esterification catalysts added refers to the total amount of these esterification catalysts.

[0070] An acid-type esterification catalyst (esterification catalyst), particularly a sulfur-containing acid-type esterification catalyst, may be supplied to the reactor as is or in the form of a solution (e.g., an aqueous solution). When the acid-type esterification catalyst (esterification catalyst) is supplied to the reactor in the form of a solution (e.g., an aqueous solution), the concentration of the esterification catalyst in the solution may be, for example, from 50% by mass to 90% by mass, preferably from 60% by mass to 80% by mass, but is not limited to these ranges. When two or more esterification catalysts are used in combination, the concentration of the esterification catalyst refers to the total concentration of these esterification catalysts in the solution.

[0071] The acrylic acid or methacrylic acid used as a starting material is produced by known methods, for example, industrially from propylene or isobutene. Independently of the use of renewable alcohols, the method for producing a (meth)acrylic acid ester according to one embodiment of the present invention may also include the use of renewable (meth)acrylic acid during esterification. For example, acrylic acid can be obtained by a method comprising a first step of dehydrating glycerol to obtain acrolein from glycerol, followed by a step of vapor-phase oxidation of the resulting acrolein; or by dehydrating 2-hydroxypropionic acid (lactic acid) or 3-hydroxypropionic acid and their esters, but the method for producing (meth)acrylic acid is not limited to these methods. The (meth)acrylic acid used as a starting material preferably contains at least one compound selected from the group consisting of acrylic acid and methacrylic acid. The (meth)acrylic acid may contain either acrylic acid or methacrylic acid, but more preferably contains methacrylic acid. Among these, acrylic acid or methacrylic acid is preferred. The (meth)acrylic acid is preferably acrylic acid or methacrylic acid, and particularly preferably methacrylic acid. The amount of (meth)acrylic acid added is, for example, 10 to 50 parts by mass, preferably 20 to 35 parts by mass, per 100 parts by mass of the total amount of reaction materials (the total amount of (meth)acrylic acid, secondary alcohol, acid-type esterification catalyst, polymerization inhibitor, and, if added, organic solvent and / or water (organic solvent, water, or a combination thereof)). When (meth)acrylic acid is added in portions, the amount of (meth)acrylic acid added refers to the total amount of (meth)acrylic acid. When acrylic acid and methacrylic acid are used in combination, the amount of (meth)acrylic acid added refers to the total amount of acrylic acid and methacrylic acid.

[0072] The secondary alcohol is not particularly limited, and examples thereof include isopropanol, 2-pentanol, 3-pentanol, 2-heptanol, 3-heptanol, 2-octanol, 3-octanol, 4-octanol, 2-nonanol, 2-decanol, 2-undecanol, 2-dodecanol, 2-tridecanol, 2-tetradecanol, 2-pentadecanol, 2-hexadecanol, 2-heptadecanol, 2-octadecanol, 2-nonadecanol, 2-eicosanol, 2-docosanol, etc. These secondary alcohols may be used alone or in combination of two or more. The secondary alcohol preferably contains at least one compound selected from the group consisting of isopropanol, 2-pentanol, 3-pentanol, 2-heptanol, 3-heptanol, 2-octanol, 3-octanol, 4-octanol, 2-nonanol, 2-decanol, 2-undecanol, 2-dodecanol, 2-tridecanol, 2-tetradecanol, 2-pentadecanol, 2-hexadecanol, 2-heptadecanol, 2-octadecanol, 2-nonadecanol, 2-eicosanol, and 2-docosanol, more preferably contains at least one compound selected from the group consisting of 2-heptanol, 3-heptanol, 2-octanol, 3-octanol, 4-octanol, and 2-nonanol, and even more preferably contains 2-octanol. Among these, at least one selected from the group consisting of 2-octanol, 3-octanol, and 4-octanol is preferred, with 2-octanol being particularly preferred. The secondary alcohol is more preferably at least one selected from the group consisting of 2-octanol, 3-octanol, and 4-octanol, even more preferably 2-octanol, 3-octanol, or 4-octanol, with 2-octanol being particularly preferred. 2-Octanol is a renewable alcohol, specifically obtained as a by-product of sebacic acid obtained by cracking castor oil, and is useful as 1-methylheptyl bio(meth)acrylate (bio(meth)acrylic acid ester).That is, in a preferred embodiment of the present invention, the secondary alcohol is 2-octanol, and 1-methylheptyl (meth)acrylate is produced. 1-methylheptyl (meth)acrylate has the following structure. 1-methylheptyl (meth)acrylate preferably contains at least one compound selected from the group consisting of 1-methylheptyl acrylate and 1-methylheptyl methacrylate, and more preferably contains 1-methylheptyl methacrylate. 1-methylheptyl (meth)acrylate is preferably 1-methylheptyl acrylate or 1-methylheptyl methacrylate, and particularly preferably 1-methylheptyl methacrylate.

[0073] [ka]

[0074] Furthermore, (meth)acrylic acid esters are obtained by reacting equimolar amounts of a secondary alcohol and (meth)acrylic acid, but it is preferable to use a larger amount of the secondary alcohol. Specifically, the amount of secondary alcohol added is substantially equimolar to that of (meth)acrylic acid or more, for example, 0.9 to 3.0 moles, preferably 1.0 to 2.0 moles, per mole of (meth)acrylic acid. Note that when two or more secondary alcohols are used in combination, the amount of secondary alcohol added refers to the total amount of these secondary alcohols. As shown in FIG. 1, a portion of the secondary alcohol is directly introduced into reactor 1 via pipe 11a. In addition, a portion of the secondary alcohol may be introduced into the top of first distillation column 2 via pipe 11c. This more reliably achieves reflux in first distillation column 2.

[0075] The polymerization inhibitor is not particularly limited, and examples thereof include phenothiazine, hydroquinone, methoquinone, methylhydroquinone, benzoquinone, hydroquinone monomethyl ether, di(tert-butyl)-p-cresol (BHT), p-phenylenediamine, TEMPO (2,2,6,6-tetramethyl-1-piperazinyloxy), p-tert-butylcatechol, di(tert-butyl)catechol, TEMPO derivatives such as OH-TEMPO, 2,6-tert-butyl-4-methylphenol, and copper(II) dibutyldithiocarbamate. These polymerization inhibitors may be used alone or in combination of two or more. The polymerization inhibitor preferably contains at least one compound selected from the group consisting of phenothiazine, hydroquinone, methoquinone, methylhydroquinone, benzoquinone, hydroquinone monomethyl ether, di(tert-butyl)-p-cresol (BHT), p-phenylenediamine, TEMPO (2,2,6,6-tetramethyl-1-piperazinyloxy), p-tert-butylcatechol, di(tert-butyl)catechol, TEMPO derivatives (e.g., OH-TEMPO), 2,6-tert-butyl-4-methylphenol, and copper(II) dibutyldithiocarbamate, and more preferably contains phenothiazine. Among these, phenothiazine is preferred. The polymerization inhibitor is preferably phenothiazine. The amount of the polymerization inhibitor added is, for example, 0.05 to 5 parts by mass, preferably 0.1 to 2 parts by mass, per 100 parts by mass of (meth)acrylic acid. When two or more polymerization inhibitors are used in combination, the amount of polymerization inhibitors to be added refers to the total amount of these polymerization inhibitors. The polymerization inhibitor may be additionally added in a subsequent purification step. In this case, the amount of polymerization inhibitor to be added refers to the total amount of the amount initially added to the reactor and the amount additionally added in the subsequent purification step.

[0076] An esterification catalyst, (meth)acrylic acid, a secondary alcohol, and a polymerization inhibitor are supplied to a reactor. In this case, the water produced in the esterification reaction and / or water separately added to the reactor (water produced in the esterification reaction, water separately added to the reactor, or a combination thereof) forms an azeotropic composition with the secondary alcohol.

[0077] Alternatively, an organic solvent may be further supplied to the reactor in addition to the esterification catalyst, (meth)acrylic acid, secondary alcohol, and polymerization inhibitor. In this case, the water produced by the esterification reaction and / or water separately added to the reactor (water produced by the esterification reaction, water separately added to the reactor, or a combination thereof) forms an azeotropic composition with the secondary alcohol and / or organic solvent, if used (secondary alcohol, organic solvent, if used, or a combination thereof). Examples of organic solvents that can be used when further supplying organic solvent to the reactor include aliphatic hydrocarbons such as hexane, heptane, pentane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ethers such as diethyl ether, diisopropyl ether, methyl tert-butyl ether, and tetrahydrofuran; and ketones such as acetone, methyl ethyl ketone, diisopropyl ketone, and methyl isobutyl ketone. These organic solvents may be used alone or in combination. The organic solvent preferably contains at least one solvent selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons, ethers, and ketones, more preferably contains aromatic hydrocarbons, further preferably contains at least one solvent selected from the group consisting of toluene and xylene, and particularly preferably contains toluene. Among these, toluene is preferred. The organic solvent is preferably toluene. Note that the organic solvent does not contain a secondary alcohol.

[0078] The amount of organic solvent added is preferably 10 to 60 parts by mass, more preferably 15 to 40 parts by mass, and even more preferably 20 to 35 parts by mass, relative to 100 parts by mass of (meth)acrylic acid. When two or more organic solvents are used in combination, the amount of organic solvents added refers to the total amount of these organic solvents.

[0079] After supplying (meth)acrylic acid, a secondary alcohol, an esterification catalyst, a polymerization inhibitor, and, if necessary, an organic solvent to a reactor, the (meth)acrylic acid and the secondary alcohol are subjected to a batch reaction in the presence of the esterification catalyst. The batch reaction conditions are not particularly limited, and known conditions can be used. For example, the reaction temperature is preferably 40°C to 120°C, more preferably 50°C to 110°C. By maintaining the reaction temperature within this range, the formation of impurities such as alkenes can be effectively suppressed. Furthermore, sufficient reaction rate can be maintained to achieve sufficient productivity. The reaction time, measured after the predetermined reaction temperature is reached, is preferably 4 hours to 24 hours, more preferably 5 hours to 15 hours. The pressure during the reaction is not particularly limited and can be appropriately selected from atmospheric pressure, reduced pressure, or elevated pressure depending on the reaction mode. However, atmospheric pressure or reduced pressure is preferred, more preferably reduced pressure, and the pressure is particularly preferably adjusted (reduced) to reach the reaction temperature. After the reaction has continued for the predetermined time, the reaction can be terminated by cooling the reactor.

[0080] The reactor 1 may be equipped with an external heating means (for example, a heat exchanger), and in this case, the reactor 1 is heated to a predetermined temperature by the heating means. The reactor 1 may also be equipped with a stirrer. The esterification reaction is an equilibrium reaction accompanied by the generation of water, as shown below. Therefore, in order to shift the reaction toward the ester production side, the generated water must be removed from the system.

[0081] [ka]

[0082] For this reason, reactor 1 is equipped with a distillation column (first distillation column) 2. This makes it possible to distill the produced water out of the system and remove water from the reaction system. Here, first distillation column 2 can be, for example, a packed distillation column or a plate distillation column having a theoretical plate number of 5 to 15 (e.g., about 10). Note that, although FIG. 1 shows reactor 1 and first distillation column 2 as separate facilities, reactor 1 and first distillation column 2 may also be integrated into one facility.

[0083] The distillation method used in the first distillation column 2 can be a known method such as simple distillation (e.g., flash distillation) or molecular distillation (thin film distillation), but is not particularly limited thereto. In this case, simple distillation is intended to be a batch distillation without a rectification portion and can be carried out using a general apparatus. Molecular distillation (thin film distillation) can be carried out using a Hickman distillation apparatus, a falling film distillation apparatus, a rotor tray distillation apparatus, a brush molecular distillation apparatus, or the like. The first distillation column 2 may be heated by a heating means such as a thermosiphon or a forced circulation external heat exchanger, and in this case, the first distillation column 2 is heated to a predetermined temperature by the heating means. When the reactor 1 and the first distillation column 2 are equipped with external heating means, the heating means of the reactor 1 and the first distillation column 2 may be installed separately or may be the same (shared). The distillation conditions are not particularly limited. The distillation pressure is, for example, 30 Torr to 850 Torr or 30 Torr to 650 Torr (1 Torr = approximately 1.3 hPa) or atmospheric pressure, but is not limited thereto. The distillation temperature (particularly the column bottom temperature) is, for example, 40°C to 120°C, preferably 40°C to 110°C, more preferably 50°C to 100°C, but is not limited thereto. The distillation time is, for example, 4 hours to 24 hours, preferably 5 hours to 15 hours, but is not limited thereto. Under these conditions, the produced water can be efficiently distilled out of the system.

[0084] The water produced by the esterification reaction forms an azeotropic composition with the secondary alcohol and / or the organic solvent, if used (the secondary alcohol, the organic solvent, if used, or a combination thereof), and is distilled as a gas from the top of the first distillation column 2. This gas is condensed to a liquid in a condenser (not shown), and then introduced into an intermediate tank (not shown) where it is allowed to stand, where it is separated into an oil phase and an aqueous phase (oil-water separation). Part or all of the oil phase may be introduced into the first distillation column 2 as reflux (not shown). Part of the oil phase may be recycled and supplied to the reactor 1 via pipes 22a and 11b.

[0085] As described above, during the esterification reaction, a mixture containing mainly a secondary alcohol and / or an organic solvent, if used (a secondary alcohol, an organic solvent, if used, or a combination thereof), an azeotropic composition with water, and a small amount of (meth)acrylic acid is distilled and, after condensation, separated into two phases: an oil phase and an aqueous phase. For this purpose, the reactor 1 and the first distillation column (e.g., a packed distillation column) 2 may be equipped with a condenser to which water (e.g., water at 25°C) is supplied, and a decanter to receive the condensed azeotropic composition. This decanter may be equipped with a system capable of automatically removing the reaction water produced by opening a solenoid valve to control the position of the lower aqueous phase. Alternatively, the decanter may be operated under reduced pressure by adjusting the vacuum system.

[0086] Furthermore, the aqueous phase may be partially discarded, or partially or entirely supplied to residence tank 3 via pipe 22b. The aqueous phase is not reintroduced into first distillation column 2. This allows the equilibrium of the esterification reaction to constantly shift toward the production of (meth)acrylic acid esters (i.e., improves the selectivity and yield). Alternatively, the aqueous phase may be biologically treated and then distilled before being discharged to recover the secondary alcohol and (meth)acrylic acid contained in low concentrations.

[0087] The esterification reaction produces a reaction mixture (reaction mixture A) in reactor 1 that contains a (meth)acrylic acid ester and a by-product, an ester of the acid-type esterification catalyst. In addition to the (meth)acrylic acid ester and the ester of the acid-type esterification catalyst, reaction mixture A may generally contain unreacted secondary alcohol, unreacted (meth)acrylic acid, the esterification catalyst, a polymerization inhibitor, other high-boiling by-products, and the like. The (meth)acrylic acid ester is generally contained in reaction mixture A in a proportion of about 50% by mass or more and 95% by mass or less.

[0088] [Step (b)] In this step, the reaction mixture A obtained in step (a) is withdrawn from the bottom of reactor 1 and supplied to residence tank 3 via pipe 31. The aqueous phase separated from first distillation column 2 is supplied to residence tank 3 via pipe 22b. The aqueous phase and, if necessary, additional water are supplied to residence tank 3, whereby reaction mixture A is neutralized and washed with water. This removes acid and alkaline components from reaction mixture A. In this step, mixture M1 obtained by neutralizing and washing reaction mixture A is separated into an oil phase O1 and an aqueous phase W1. The aqueous phase W1 is removed from residence tank 3, leaving the oil phase O1 in residence tank 3. The oil phase O1 and water are then retained in residence tank 3 while in contact with each other at a temperature T of 50°C or higher and 105°C or lower. This decomposes the esterified product of the esterification catalyst, which is difficult to remove by neutralization and water washing, into the esterification catalyst and a secondary alcohol. The resulting mixture M2 (mixture after hot water treatment) is then separated into an oil phase O2 and an aqueous phase W2, and the aqueous phase W2 is removed from the retention tank 3. At this time, since the esterification catalyst is present in the aqueous phase W2, the esterified product of the esterification catalyst in the reaction mixture A is removed in the form of the esterification catalyst. The retention tank 3 may be equipped with a stirring device, or may be a tank in which the mixture is retained while being stirred (a stirring retention tank) or a mixer. The retention tank 3 may also be equipped with a heating means.

[0089] Neutralization is carried out using a base, thereby neutralizing the acid content in reaction mixture A. Examples of bases that can be used include sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonium carbonate. These bases may be used alone or in combination of two or more. The base preferably contains at least one compound selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonium carbonate, and more preferably contains sodium hydroxide. Among these, sodium hydroxide is preferred. The base is preferably sodium hydroxide. The base may also be used in the form of an aqueous solution. The amount of base added may be any amount sufficient to neutralize the residual acid content in reaction mixture A, and can be appropriately selected taking into consideration factors such as the amount of esterification catalyst supplied to the reactor.

[0090] After neutralization, the resulting mixture is allowed to stand (stirring, if present, is stopped), whereby the mixture is separated into an oil phase and an aqueous phase (oil-water separation). The aqueous phase (acid components and alkaline components (bases) containing the esterification catalyst) is removed from the system via pipe 33, leaving only the oil phase in residence tank 3 (neutralization step).

[0091] Next, water is added to the retention tank 3 and stirred if necessary to remove the base remaining in the oil phase (water washing). After washing with water, the resulting mixture M1 is allowed to stand (and stirring, if used, is stopped), whereby the mixture M1 is separated into an oil phase and an aqueous phase (oil-water separation). Of these, the aqueous phase (aqueous phase W1) (alkaline component (base)) is removed from the system via pipe 33, leaving only the oil phase (oil phase O1) in the retention tank 3 (water washing step).

[0092] The neutralization step and the water-washing step may each be carried out as separate batch processes, or may be carried out continuously in a continuous extraction tower (the neutralization step and the water-washing step may also be carried out continuously in a continuous extraction tower). Furthermore, the neutralization step and the water-washing step may each be carried out once or repeatedly.

[0093] By these steps, most or all of the esterification catalyst contained in reaction mixture A is removed from the system as an aqueous phase.

[0094] The neutralization treatment and the water-washing treatment are preferably carried out at a temperature of less than 50° C. For example, in the neutralization treatment and the water-washing treatment, the liquid temperature of the mixture containing water is preferably less than 50° C.

[0095] After washing with water, the oil phase O1 may be heated. If an organic solvent is used, it is preferable to heat the oil phase O1 after washing with water. After washing with water, the oil phase O1 may be subjected to a heat treatment. If an organic solvent is used, it is preferable to heat the oil phase O1 after washing with water. (Heating Step) After washing with water, the oil phase O1 may be subjected to an organic solvent-cutting treatment. In this specification, the organic solvent-cutting treatment refers to a treatment to reduce the content of the organic solvent or to completely remove the organic solvent. The organic solvent-cutting treatment may be performed, for example, by distillation of the oil phase O1. The method of the organic solvent-cutting treatment is not particularly limited, but examples include methods including heating. As a result, the organic solvent may be recovered as a gas or, if necessary, condensed. This gas or condensate may be supplied (recycled) to the reactor 1 via pipes 32 and 11b. Note that this supply (recycle) of the gas or condensate is generally performed batchwise. Details of the heating method are the same as those described below in step (f) (description of heating the oil phase after washing with water in step (f)), except for the target of the heat treatment. The method of organic solvent cutting is not particularly limited, but may include, for example, heating the oil phase O1 in the retention tank 3 and performing simple distillation. The pressure in the retention tank 3 is not particularly limited, but may, for example, be gradually reduced. The pressure in the retention tank 3 may, for example, be gradually reduced from 680 hPa to 90 hPa. Furthermore, the temperature of the bottoms liquid during distillation may, for example, be increased from 110°C to 130°C, or may, for example, be increased from 110°C to 125°C. The organic solvent removal rate in simple distillation is not particularly limited, but, for example, it is preferable to distill off 90% by mass or more of the organic solvent contained in the bottoms liquid (removal rate of 90% by mass or more), and more preferably 95% by mass or more (removal rate of 95% by mass or more). The organic solvent cutting process is not particularly limited, but may, for example, be a toluene cut process, which is a process that reduces the toluene content or removes all of the toluene. The organic solvent cutting step in which the organic solvent cutting treatment is performed is not particularly limited, but for example, a toluene cutting step in which a toluene cutting treatment is performed can be mentioned. Note that if toluene remains in the bottom liquid, it becomes more difficult to reduce the pressure (reduce pressure) in the distillation in step (c) (distillation in the second distillation column).Therefore, it is preferable to carry out the hot water treatment step described below using the oil phase O1 that has been subjected to the toluene cutting step at the above temperature, at the above removal rate, or at a combination of these. Note that when a heat treatment, an organic solvent cutting treatment, or a combination thereof is performed after the water washing treatment and before the hot water treatment, the oil phase O1 hereinafter refers to the oil phase O1 that has been subjected to the heat treatment, the organic solvent cutting treatment, or a combination thereof.

[0096] After washing with water (after the water-washing treatment), or after heat treatment, organic solvent-cutting treatment, or a combination of these, the oil phase O1 is retained in a retention tank 3 containing the oil phase O1 while being in contact with water at a temperature T of 50°C or higher and 105°C or lower. This decomposes the esterification product of the esterification catalyst, which is difficult to remove by neutralization and water-washing, into the esterification catalyst and a secondary alcohol.

[0097] After the oil phase O1 and water are allowed to contact and retain at a temperature T of 50°C or higher and 105°C or lower, the resulting mixture M2 is allowed to stand (stirring, if used, is stopped), whereby the mixture M2 is separated into an oil phase O2 and an aqueous phase W2 (oil-water separation). Of these, part or all (preferably all) of the aqueous phase (aqueous phase W2) (acid-type esterification catalyst) is removed to the outside of the system via pipe 33, leaving the oil phase (oil phase O2) in the retention tank 3 (hot water treatment step).

[0098] Although water may be present in the oil phase (oil phase O2) after the hot water treatment, in step (c) described below, the water will be removed via the same route as the recovered alcohol containing secondary alcohol (secondary alcohol-rich fluid). Therefore, it is thought that there will be almost no decrease in the yield of the (meth)acrylic acid ester due to water contamination into the oil phase by the hot water treatment.

[0099] The oil phase (oil phase O2) after the hot water treatment may be heated. When an organic solvent is used, it is preferable to heat the oil phase (oil phase O2) after the hot water treatment. After water washing, the oil phase O2 may be subjected to a heat treatment. When an organic solvent is used, it is preferable to heat the oil phase O2 after water washing. (Heating Step) When an organic solvent is used, the oil phase (oil phase O2) after the hot water treatment may be subjected to an organic solvent cutting treatment. The method of the organic solvent cutting treatment is not particularly limited, but examples include methods including heating. By using these, the organic solvent may be recovered as a gas, or may be condensed if necessary. This gas or condensate may be supplied (recycled) to the reactor 1 via pipes 32 and 11b. Note that this gas or condensate supply (recycle) is generally performed in batches. Details of the heating method are the same as those described below in step (f) (description of heating the oil phase after water washing in step (f)), except for the target of the heat treatment. The organic solvent cutting treatment may be performed, for example, by distillation of the oil phase O2. The method of organic solvent cutting treatment is not particularly limited, but may include, for example, heating the oil phase O2 in the retention tank 3 and performing simple distillation. The pressure in the retention tank 3 is not particularly limited, but may, for example, be gradually reduced. The pressure in the retention tank 3 may, for example, be gradually reduced from 680 hPa to 90 hPa. Furthermore, the temperature of the bottoms liquid during distillation may, for example, be increased from 110°C to 130°C, or may, for example, be increased from 110°C to 125°C. The organic solvent removal rate in simple distillation is not particularly limited, but, for example, it is preferable to distill off 90% by mass or more of the organic solvent contained in the bottoms liquid (removal rate of 90% by mass or more), and more preferably 95% by mass or more (removal rate of 95% by mass or more). The organic solvent cutting treatment is not particularly limited, but may, for example, be a toluene cutting treatment, which is a treatment that reduces the toluene content or removes all of the toluene. The organic solvent cutting step in which the organic solvent cutting treatment is performed is not particularly limited, but for example, a toluene cutting step in which a toluene cutting treatment is performed can be mentioned. Note that if toluene remains in the bottom liquid, it becomes more difficult to reduce the pressure (reduce pressure) in the distillation in step (c) (distillation in the second distillation column).For this reason, it is preferable to carry out a toluene cutting step using the above temperature for the oil phase O2, achieving the above removal rate, or achieving both of these.

[0100] After the neutralization treatment, the water washing treatment, and the hot water treatment, and if necessary, the heating treatment, the organic solvent removal treatment, or a combination thereof, an oil phase (reaction mixture B) containing a (meth)acrylic acid ester remains in the retention tank 3.

[0101] A method for producing a (meth)acrylic acid ester according to a preferred embodiment of the present invention includes contacting a liquid L with water in a reactor and / or a retention tank to separate a mixture containing the liquid L and the water into an organic phase containing the (meth)acrylic acid ester and an aqueous phase containing an acid-type esterification catalyst, and removing a part or all of the aqueous phase.

[0102] In a preferred embodiment of the method for producing (meth)acrylic acid according to the present invention, the contacting of liquid L with water in the reactor and / or residence tank involves using as liquid L a liquid obtained by neutralizing and washing a reaction mixture (e.g., the reaction mixture A) containing a (meth)acrylic ester and an esterified product of the esterification catalyst, and contacting the liquid (i.e., the liquid obtained by neutralizing and washing a reaction mixture containing a (meth)acrylic ester and an esterified product of the esterification catalyst) with water at a temperature T. In this case, it is preferable that the reaction mixture containing a (meth)acrylic ester and an esterified product of the esterification catalyst is extracted from the reactor, and that liquid L (the liquid obtained by neutralizing and washing the reaction mixture) is contacted with water in the residence tank. In this embodiment, liquid L may be a liquid obtained by neutralizing a reaction mixture containing a (meth)acrylic ester and an esterified product of the esterification catalyst, washing with water, and removing an organic solvent (e.g., removing toluene).

[0103] In a more preferred embodiment of the method for producing (meth)acrylic acid according to the present invention, the contacting of liquid L with water in the reactor and / or residence tank comprises using as liquid L a liquid obtained by neutralizing and washing a reaction mixture containing an ester of a (meth)acrylic ester and an ester of the esterification catalyst (e.g., the reaction mixture A) and contacting the liquid (i.e., the liquid obtained by neutralizing and washing a reaction mixture containing an ester of a (meth)acrylic ester and an ester of the esterification catalyst) with water at a temperature T; the production method further comprises supplying the reaction mixture obtained after the contacting treatment (e.g., the reaction mixture B) to a distillation column and distilling it. In this case, it is preferred that the reaction mixture containing an ester of a (meth)acrylic ester and an ester of the esterification catalyst is extracted from the reactor, and that liquid L (i.e., the liquid obtained by neutralizing and washing the reaction mixture) be contacted with water in the residence tank. In this embodiment, the liquid L may be a liquid obtained by subjecting a reaction mixture containing an ester of a (meth)acrylic acid ester and an esterification catalyst to a neutralization treatment, a water washing treatment, and an organic solvent removal treatment (for example, a toluene removal treatment).

[0104] In this embodiment (the method for producing a (meth)acrylic acid ester, including the steps (a), (b), (c), (d), and (e)), as shown in FIG. 1, steps (a) and (b) are performed in separate apparatuses. Furthermore, steps (a) and (b) are performed batchwise. Therefore, as shown in FIG. 2, steps (a) and (b) may be performed in a single apparatus (another embodiment (I)). That is, in this other embodiment (I), reactor 1 also functions as residence tank 3 ("1(3)" in FIG. 2). Specifically, in this other embodiment (I), after completion of the reaction in step (a), the aqueous phase or water separated from first distillation column 2 is supplied via pipe 22b to reaction mixture A in reactor 1(3) obtained in step (a). In this other embodiment (I), steps (a) and (b) are performed in the same manner as steps (a) and (b), except that the reactor 1 and the residence tank 3 are integrated (the reactor 1(3) is used). In addition, in this other embodiment (I), a tank 25 may be provided to separately store the aqueous phase separated from the first distillation column 2 until it is supplied to the reactor 1(3). Alternatively, as shown in FIGS. 3 and 4, the aqueous phase separated from the first distillation column 2 may be removed (wastewater) via pipe 22c. In this case, water is separately supplied to perform step (b) (neutralization step, water washing step, hot water treatment step, and, if necessary, heating treatment, organic solvent removal treatment, or a combination thereof). In FIGS. 3 and 4, the entire aqueous phase separated from the first distillation column 2 is removed via pipe 22c. However, a portion of the aqueous phase may be removed via pipe 22c and the remainder may be supplied to the residence tank 3 or the reactor 1(3) (not shown). Furthermore, as shown in Figures 2 and 4, a part or all of the oil phase obtained by condensation and / or oil-aqueous separation of the gas distilled from the top of first distillation column 2 (the oil phase obtained by condensation of the gas distilled from the top of first distillation column 2, the oil phase obtained by oil-aqueous separation of the gas distilled from the top of first distillation column 2 or the condensate thereof, or a combination thereof) may be supplied (recycled) to reactor 1 (3) via pipes 22a (32) and 11b.

[0105] By the step (b), an oil phase (reaction mixture B) is obtained in the residence tank 3 (FIG. 1, FIG. 3) or the reactor 1 (3) (FIG. 2, FIG. 4).

[0106] [Process (c)] In this step, the oil phase (reaction mixture B) obtained in step (b) is supplied to second distillation column 4 via pipe 41 and distilled. This separates the bottom liquid of second distillation column 4, which contains (meth)acrylic acid ester, from recovered alcohol (secondary alcohol-rich fluid) (low-boiling impurities) containing secondary alcohol. As mentioned above, steps (a) and (b) are generally performed batchwise, but steps after this step are performed continuously (continuous operation).

[0107] In the second distillation column 4, the oil phase (reaction mixture B) obtained in the residence tank 3 is distilled. The gas or its condensate distilled from the top of the column contains a secondary alcohol, (meth)acrylic acid, and a small amount of a (meth)acrylic acid ester (light-boiling impurity). Therefore, this gas or condensate may be supplied (recycled) to the reactor 1 via pipes 42 and 11b. The supply (recycle) of this gas or condensate (recovered alcohol) is generally carried out in batches.

[0108] Here, the distillation method used in the second distillation column 4 can be a known method such as simple distillation (e.g., flash distillation) or molecular distillation (thin film distillation), but is not particularly limited thereto. The second distillation column 4 can be a packed column or a plate column having a theoretical plate number of 5 to 20 (e.g., about 15). The second distillation column 4 may also be heated by a heater such as a thermosiphon or a forced circulation external heat exchanger. In this case, the distillation conditions are not particularly limited. The distillation pressure is, for example, but not limited to, a reduced pressure of 5 to 50 Torr (1 Torr = about 1.3 hPa) or atmospheric pressure. The distillation temperature (particularly the column bottom temperature) is, for example, but not limited to, 80 to 150°C, preferably 100 to 130°C. Under these conditions, components with relatively low boiling points (low-boiling impurities containing secondary alcohols as the main component) can be efficiently distilled out of the system. If necessary, a polymerization inhibitor may be introduced from the top of the second distillation column 4. In this case, the polymerization inhibitor may be used in the form of a solution dissolved in a secondary alcohol.

[0109] A fluid (column bottom liquid) containing a large amount of (meth)acrylic acid ester remains at the bottom of the second distillation column 4 (reaction mixture C).

[0110] The operations from the second distillation column 4 onwards are continuous, but in this case, the recycle (return) of the gas or its condensate (recovered alcohol) is also a batch operation because the return destination is a batch operation. Meanwhile, the bottom liquid of the second distillation column 4 containing the (meth)acrylic acid ester is sent to the third distillation column 5 via pipe 51.

[0111] [Step (d)] In this step, the bottom liquid (reaction mixture C) from the second distillation column 4 obtained in step (c) is extracted from the bottom of the second distillation column 4 and supplied to the third distillation column 5 via pipe 51 for distillation. As a result, the final product, a purified (meth)acrylic acid ester, is distilled from the top of the distillation column 4 via pipe 52, and a bottom liquid (bottom liquid D) remains at the bottom of the third distillation column 5. The purified (meth)acrylic acid ester is usually shipped as a product. Meanwhile, the bottom liquid (bottom liquid D) from the third distillation column 5 contains high-boiling impurities (e.g., Michael adducts resulting from the addition of secondary alcohols to (meth)acrylic acid esters, esters of (meth)acrylic acid dimers) and polymerization inhibitors, and is sent to the next step (treatment device 6) via pipe 61.

[0112] Here, the distillation method used in the third distillation column 5 can be a known method such as simple distillation (e.g., flash distillation) or molecular distillation (thin film distillation), but is not particularly limited thereto. For example, a packed column or a plate column having a theoretical plate number of 5 to 20 (e.g., theoretical plate number = approximately 5 to approximately 10) can be used. The third distillation column 5 may also be heated by a heater such as a thermosiphon or a forced circulation external heat exchanger. In this case, the distillation conditions are not particularly limited. The distillation pressure is, for example, but not limited to, a reduced pressure of 5 to 50 Torr (1 Torr = approximately 1.3 hPa) or atmospheric pressure. The distillation temperature (particularly the column bottom temperature) is, for example, but not limited to, 80 to 150°C, preferably 100 to 130°C. Under these conditions, the purified (meth)acrylic acid ester can be efficiently distilled out of the system. If necessary, a polymerization inhibitor may be introduced from the top of the third distillation column 5. In this case, the polymerization inhibitor may be used in the form of a solution dissolved in the (meth)acrylic acid ester.

[0113] In this embodiment (the method for producing a (meth)acrylic acid ester, including the steps (a), (b), (c), (d), and (e)), as shown in FIG. 1, steps (c) and (d) are performed in separate apparatuses. However, as shown in FIG. 3, steps (c) and (d) may be performed in a single apparatus (another embodiment (II)). That is, in this other embodiment (II), the second distillation column 4 and the third distillation column 5 are used as the same apparatus ("4(5)" in FIG. 3). In this other embodiment (II), steps (c) and (d) are performed under the same conditions as those described for steps (c) and (d), except that they are performed in a single distillation column. When steps (c) and (d) are performed as a batch process, the oil phase (reaction mixture B) obtained in step (b) is supplied to the second distillation column 4(5) via pipe 41 and distilled (first distillation). The bottom liquid (reaction mixture C) remaining at the bottom is then distilled in the second distillation column 4(5) (second distillation). In step (c) (first distillation), the gas or condensate (light-boiling impurities) distilled from the top of the second distillation column 4(5) is supplied (recycled) to the reactor 1 via pipes 42 and 11b. Next, in step (d) (second distillation), the purified (meth)acrylic acid ester, the final product, is distilled from the top of the second distillation column 4(5) via pipe 52a after switching the distillation line. Finally, the bottom liquid (bottom liquid D) remains at the bottom of the second distillation column 4(5). When steps (c) and (d) are performed continuously, the gas or condensate (light-boiling impurities) distilled from the top of the second distillation column 4(5) in step (c) is supplied (recycled) to the reactor 1 via pipes 42 and 11b, and the final product, the purified (meth)acrylic acid ester, is distilled from the side of the second distillation column 4(5) via pipe 52b (side cut). Finally, a column bottom liquid (column bottom liquid D) remains at the bottom of the second distillation column 4(5).

[0114] Furthermore, the embodiments described in this specification can be arbitrarily combined to form another embodiment. For example, as shown in Fig. 4, another embodiment (I) in Fig. 2 and another embodiment (II) in Fig. 3 may be combined (another embodiment (III)).

[0115] [Step (e)] In this step, the bottom liquid (bottom liquid D) of the third distillation column 5 obtained in step (d) is extracted from the bottom of the third distillation column 5 and supplied to a treatment device 6 via a pipe 61. This separates the bottom liquid (bottom liquid D) into an active ingredient (recovered (meth)acrylic acid ester) and waste oil.

[0116] The processing device 6 may be a distillation column. The distillation method used in the processing device 6 may be, but is not limited to, a known method such as simple distillation (e.g., flash distillation) or molecular distillation (thin film distillation). Preferably, the processing device 6 is a molecular distillation column (thin film distillation column). Alternatively, the processing device 6 may be heated by a heater such as a thermosiphon or a forced circulation external heat exchanger. In this case, the distillation conditions are not particularly limited. The distillation pressure may be, for example, under a reduced pressure of 5 to 50 Torr (1 Torr = approximately 1.3 hPa) or under atmospheric pressure, but is not limited thereto. The distillation temperature (particularly the column bottom temperature) may be, for example, 80 to 150°C, preferably 100 to 130°C, but is not limited thereto. Under these conditions, the active ingredient (hereinafter sometimes referred to as recovered (meth)acrylic acid ester) contained in the column bottom liquid D can be efficiently separated from the waste oil.

[0117] The recovered (meth)acrylic acid ester separated in the treatment device 6 may be supplied (recycled) to the reactor 1 via pipes 64 and 11b.

[0118] The recovered (meth)acrylic acid ester may be supplied (recycled) to the retention tank 3 via pipe 62. The recovered (meth)acrylic acid ester supplied (recycled) to the retention tank 3 is subjected to the same neutralization step, water washing step, and hot water treatment step as in step (b) above, and, if necessary, is further subjected to a heating step, an organic solvent removal step, a distillation step, or a combination thereof. The gas or condensate obtained after these steps may be supplied (recycled) to the reactor 1.

[0119] The operations from the second distillation column 4 onwards are continuous, but the recycling (return) of the recovered (meth)acrylic acid ester is also a batch operation because the return destination is a batch operation.

[0120] The waste oil separated in the treatment device 6 is disposed of via a pipe 63.

[0121] The method for producing a (meth)acrylic acid ester according to another embodiment (IV) of the present invention may further include the following steps (f) and (g) in addition to the steps (a), (c), (d), and (e). This other embodiment (IV) can improve the yield of the (meth)acrylic acid ester when the bottom liquid of the second distillation column 4 contains an esterified product of the esterification catalyst. A schematic diagram of the production process of this other embodiment (IV) is shown in FIG. 5.

[0122] A method for producing a (meth)acrylic acid ester according to yet another embodiment (V) of the present invention may include the steps (a), (b), (c), (d), (e), and (g). This embodiment (V) can further improve the yield of the (meth)acrylic acid ester when the bottom liquid of the second distillation column 4 contains an esterified product of the esterification catalyst. A schematic diagram of the production process of this embodiment (V) is shown in FIG. 6.

[0123] (f) After the step (a) and before the step (c), the reaction mixture A is withdrawn from the bottom of the reactor 1 and supplied to a neutralization water-washing tank 7, where the reaction mixture A is neutralized and washed with water in the neutralization water-washing tank 7 and allowed to stand to separate the oil and water. The aqueous phase is then removed to the outside of the system via a pipe 73, while the residue (oil phase) is subjected, if necessary, to a heat treatment, an organic solvent removal treatment, or a combination of these (for example, if an organic solvent is present, the organic solvent is distilled off by heating, if necessary) to obtain a reaction mixture B' (step (f)).

[0124] Step (c) after step (f) is the same as described above, except that reaction mixture B' is used instead of reaction mixture B in the above description.

[0125] (g) In the step (d), the bottom liquid of the second distillation column 4 is extracted from the bottom of the second distillation column 4 and then supplied to the third distillation column 5. Before distillation, the bottom liquid of the second distillation column 4 is extracted from the bottom of the second distillation column 4 and supplied to a residence tank 3'. In the residence tank 3', the bottom liquid of the second distillation column 4 (here, since the bottom liquid contains an esterified product of the esterification catalyst, it corresponds to liquid L) is contacted with water at a temperature T of 50°C or higher and 105°C or lower. and retaining the oil phase O3 while heating to obtain a mixture M3 (mixture after hot water treatment), separating the mixture M3 into an oil phase O3 and an aqueous phase W3, removing the aqueous phase W3 from the residence tank 3', recovering the resulting gas or condensate from the residence tank 3' as needed, and supplying the residue in the residence tank 3' (the oil phase O3) to the third distillation column 5 in place of the column bottom liquid of the second distillation column 4 after subjecting it to a heat treatment, an organic solvent removal treatment, or a combination thereof as needed (step (g)).

[0126] [Process (f)] This step is performed after step (a) and before step (c). This step is generally performed in batches. The details of the neutralization and water washing in this step are the same as those described for the neutralization and water washing in step (b). In this step, reaction mixture A is withdrawn from the bottom of reactor 1 and supplied to neutralization water washing tank 7. After neutralization and water washing in neutralization water washing tank 7, reaction mixture A may be subjected to a heat treatment, an organic solvent removal treatment, or a combination of these, if necessary. In this step, reaction mixture A is withdrawn from the bottom of reactor 1 and supplied to neutralization water washing tank 7. After neutralization and water washing in neutralization water washing tank 7, heated gas or a condensate thereof may be obtained. After neutralization, the aqueous phase (acid components and alkali components (base) including the esterification catalyst) is removed from the system via pipe 73, leaving the oil phase in neutralization water washing tank 7. In addition, in the water washing treatment, the aqueous phase portion (alkali component (base)) is removed to the outside of the system via pipe 73, and the residue (oil phase) in the neutralization water washing tank 7 is obtained as reaction mixture B'.

[0127] The oil phase after water washing (after water washing treatment) may be heated. When an organic solvent is used, it is preferable to heat the oil phase after water washing (after water washing treatment). After water washing, the oil phase may be subjected to a heat treatment. When an organic solvent is used, it is preferable to heat the oil phase after water washing (after water washing treatment). (Heating step) When an organic solvent is used, the oil phase after water washing (after water washing treatment) may be subjected to an organic solvent cutting treatment. The method of the organic solvent cutting treatment is not particularly limited, but examples include methods including heating. As a result, the organic solvent may be recovered as a gas, or may be condensed if necessary. This gas or condensate may be supplied (recycled) to the reactor 1 via pipes 72 and 11b. The supply (recycle) of this gas or condensate is generally performed batchwise.

[0128] The method for heating the oil phase after water washing (after the water washing treatment) is not particularly limited, and may be heated with a heater or distilled. Preferably, the oil phase after water washing is distilled. Known methods such as simple distillation (e.g., flash distillation) and molecular distillation (thin film distillation) can be used as the distillation method for distilling the oil phase after water washing, but are not particularly limited thereto. For example, a distillation column such as a packed column or a plate column having 5 to 20 theoretical plates can be used. The distillation column may be heated by a heater such as a thermosiphon or a forced circulation external heat exchanger. In this case, the distillation conditions are not particularly limited. The distillation pressure is, for example, but is not limited to, a reduced pressure of 5 to 50 Torr (1 Torr = approximately 1.3 hPa) or atmospheric pressure. The distillation temperature (particularly the column bottom temperature) is, for example, but not limited to, 80 to 150°C, preferably 100 to 130°C. The distillation time is, for example, but not limited to, 4 hours to 24 hours, preferably 5 hours to 15 hours, etc. Under such conditions, the gas (organic solvent) can be efficiently distilled out of the system.

[0129] The organic solvent cutting method is not particularly limited, but may include, for example, heating the oil phase in the neutralization water-washing tank 7 and performing simple distillation. The pressure in the neutralization water-washing tank 7 is not particularly limited, but may, for example, be gradually reduced. The pressure in the neutralization water-washing tank 7 may, for example, be gradually reduced from 680 hPa to 90 hPa. Furthermore, the temperature of the bottoms liquid during distillation may, for example, be increased from 110°C to 130°C, or from 110°C to 125°C. The organic solvent removal rate in simple distillation is not particularly limited, but, for example, it is preferable to distill off 90% by mass or more of the organic solvent contained in the bottoms liquid (removal rate of 90% by mass or more), and more preferably 95% by mass or more (removal rate of 95% by mass or more). The organic solvent cutting process is not particularly limited, but may, for example, be a toluene-cutting process, which involves reducing the toluene content or completely removing toluene. The organic solvent cutting step in which the organic solvent is cut is not particularly limited, but may be, for example, a toluene cutting step in which a toluene cutting treatment is performed. If toluene remains in the bottom liquid, it becomes more difficult to reduce the pressure (reduce pressure) in the distillation in step (c) (distillation in the second distillation column). For this reason, it is preferable to perform the toluene cutting step by using the above temperature for the oil phase in the neutralization water washing tank 7, achieving the above removal rate, or achieving both of these.

[0130] After the neutralization treatment and water washing treatment in this step, and if necessary, further heat treatment, organic solvent removal treatment, or a combination of these, the oil phase containing the (meth)acrylic acid ester (reaction mixture B') remains in the neutralization and water washing tank 7.

[0131] Thereafter, in step (c), the oil phase (reaction mixture B') obtained in step (f) is supplied to the second distillation column 4 via pipe 41 and distilled. Step (c) after step (f) is the same as described above, except that reaction mixture B' is used instead of reaction mixture B in the above description.

[0132] [Process (g)] This step is carried out after the bottom liquid of the second distillation column 4 is withdrawn from the bottom of the second distillation column 4 in step (d) and before it is fed to the third distillation column 5 for distillation. This step is generally carried out batchwise. In this step, the bottom liquid of the second distillation column 4 is withdrawn from the bottom of the second distillation column 4 and fed to the residence tank 3' via pipe 51a. The bottom liquid of the second distillation column 4 and water are contacted and retained in the residence tank 3' at a temperature T of 50°C to 105°C. This decomposes the esterified product of the esterification catalyst, which is difficult to remove by neutralization and water washing, into the esterification catalyst and secondary alcohol. The resulting mixture M3 (mixture after hot water treatment) is then separated into an oil phase O3 and an aqueous phase W3. The aqueous phase W3 is removed from the residence tank 3', leaving the oil phase (oil phase O3) in the residence tank 3'. A part or all (preferably all) of the aqueous phase (aqueous phase W3) is removed to the outside of the system via pipe 35. At this time, since the esterification catalyst is present in the aqueous phase W3, the esterified product of the esterification catalyst in the bottom liquid of second distillation column 4 is removed in the form of the esterification catalyst (hot water treatment step).

[0133] The resulting secondary alcohol is recovered as a gas and, if necessary, condensed. This gas or condensate may be recycled to the reactor 1 via pipes 34 and 11b. The gas or condensate is generally recycled in batches.

[0134] Here, the retention tank 3' may be equipped with a stirring device, or may be a tank for retaining the material while stirring (a stirring retention tank) or a mixer. The retention tank 3' may also be equipped with a heating means. Details of the hot water treatment in this step are the same as those described for the hot water treatment in step (b), except that the target of treatment and some of the piping are different.

[0135] Although water may be present in the oil phase (oil phase O3) after hot water treatment, the water can be removed by the side cut or vertically divided wall column (DWC) in step (d) described above. Therefore, it is thought that there will be almost no decrease in the yield of (meth)acrylic acid ester due to water contamination of the oil phase by hot water treatment.

[0136] The oil phase (oil phase O3) after the hot water treatment may be heated. When an organic solvent is used, it is preferable to heat the oil phase (oil phase O3) after the hot water treatment. After the hot water treatment, the oil phase O3 may be subjected to a heat treatment. When an organic solvent is used, it is preferable to heat the oil phase O3 after the hot water treatment. (Heating Step) When an organic solvent is used, the oil phase (oil phase O3) after the hot water treatment may be subjected to an organic solvent cutting treatment. The method for the organic solvent cutting treatment is not particularly limited, but examples include methods including heating. As a result, the secondary alcohol, the organic solvent, or a combination thereof may be recovered as a gas, or may be condensed if necessary. This gas or condensate may be supplied (recycled) to reactor 1 via pipes 34 and 11b. Note that this supply (recycle) of the gas or condensate is generally performed in batches. The details of the heating method are also the same as those described in the step (f) of heating the oil phase after water washing (description of the method for heating the oil phase after water washing), except for the target of the heat treatment and some of the pipes. The organic solvent removal treatment may be carried out, for example, by distillation of the oil phase O3. The method of the organic solvent removal treatment is not particularly limited, and may include, for example, heating the oil phase O3 in the retention tank 3' and performing simple distillation. The pressure in the retention tank 3' is not particularly limited, and may, for example, be gradually reduced. The pressure in the retention tank 3' may, for example, be gradually reduced from 680 hPa to 90 hPa. Furthermore, during this distillation, the temperature of the bottoms liquid may, for example, be increased from 110°C to 130°C, or from 110°C to 125°C. The organic solvent removal rate in simple distillation is not particularly limited, and, for example, it is preferable to distill off 90% by mass or more of the organic solvent contained in the bottoms liquid (removal rate of 90% by mass or more), and more preferably 95% by mass or more (removal rate of 95% by mass or more). The organic solvent cutting treatment is not particularly limited, but examples thereof include a toluene cutting treatment, which is a treatment that reduces the toluene content or removes all toluene. The organic solvent cutting step that performs the organic solvent cutting treatment is not particularly limited, but examples thereof include a toluene cutting step that performs a toluene cutting treatment.If toluene remains in the bottom liquid, it becomes more difficult to reduce the pressure (decompression) in the next distillation step. Therefore, it is preferable to perform a toluene-cutting step using the above-mentioned temperature for the oil phase O3, achieving the above-mentioned removal rate, or achieving both of these. If a heat treatment, organic solvent-cutting treatment, or a combination thereof is performed after the hot water treatment, hereinafter, the oil phase O3 refers to the oil phase O3 that has been subjected to the heat treatment, organic solvent-cutting treatment, or a combination thereof.

[0137] After the hot water treatment, if necessary, the residue (oil phase O3) is subjected to a heat treatment, an organic solvent removal treatment, or a combination thereof, and the residue (oil phase O3) remains in residence tank 3'. The resulting residue (oil phase O3) in residence tank 3' is supplied to third distillation column 5 via pipe 51b in place of the bottom liquid of second distillation column 4.

[0138] 5, the steps (a), (f), and (g) are generally performed in batches, and the steps (c), (d), and (e) are performed continuously. In this case, intermediate tanks may be provided between the steps (c) and (g), and between the steps (g) and (d), respectively.

[0139] 6, generally, the steps (a), (b), and (g) are performed in batches, and the steps (c), (d), and (e) are performed continuously. In this case, intermediate tanks may be provided between the steps (c) and (g), and between the steps (g) and (d), respectively.

[0140] A method for producing a (meth)acrylic ester according to one embodiment of the present invention further includes subjecting a reaction mixture containing an ester of a (meth)acrylic ester and an esterification product of an esterification catalyst (e.g., the reaction mixture A) to a treatment including a neutralization treatment and a water-washing treatment, and distilling the reaction mixture obtained after the treatment including the neutralization treatment and the water-washing treatment (e.g., the reaction mixture B, the reaction mixture B', etc.) to obtain a distilled liquid. The contacting of the liquid L with water in the reactor and / or the retention tank preferably includes using the distilled liquid as the liquid L and contacting the distilled liquid with water in the retention tank at the temperature T. In this case, the reaction mixture containing the (meth)acrylic ester and an esterification product of the esterification catalyst is preferably one extracted from the reactor. The method for producing a (meth)acrylic ester preferably further includes distilling the distilled liquid with water in the retention tank. The treatment including the neutralization treatment and the water washing treatment may consist solely of the neutralization treatment and the water washing treatment, or may further include a treatment other than the neutralization treatment and the water washing treatment in addition to the neutralization treatment and the water washing treatment. The treatment including the neutralization treatment and the water washing treatment may be, for example, a treatment including the neutralization treatment, the water washing treatment, and an organic solvent cutting treatment (e.g., a toluene cutting treatment, etc.).

[0141] A method for producing a (meth)acrylic ester according to one embodiment of the present invention further includes: subjecting a reaction mixture containing an ester of a (meth)acrylic ester and an ester of an esterification catalyst (e.g., reaction mixture A) to a treatment including neutralization and water washing; supplying the reaction mixture obtained after the treatment including the neutralization and water washing (e.g., reaction mixture B, reaction mixture B') to a distillation column for distillation; and withdrawing the bottom liquid from the distillation column from the bottom of the distillation column. The contacting of liquid L with water in the reactor and / or residence tank preferably includes using the bottom liquid as liquid L and contacting the bottom liquid with water in the residence tank at temperature T. In this case, the reaction mixture containing the (meth)acrylic ester and an ester of an esterification catalyst is preferably the one withdrawn from the reactor. The method for producing a (meth)acrylic ester preferably further includes supplying the bottom liquid after the treatment including contacting the bottom liquid with water in the residence tank to another distillation column for distillation. The treatment including the neutralization treatment and the water washing treatment may consist solely of the neutralization treatment and the water washing treatment, or may further include a treatment other than the neutralization treatment and the water washing treatment in addition to the neutralization treatment and the water washing treatment. The treatment including the neutralization treatment and the water washing treatment may be, for example, a treatment including the neutralization treatment, the water washing treatment, and an organic solvent cutting treatment (e.g., a toluene cutting treatment, etc.).

[0142] A method for producing a (meth)acrylic acid ester according to one embodiment of the present invention preferably includes, before contacting a liquid L containing an esterification product of the esterification catalyst obtained during the production of the (meth)acrylic acid ester with water at a temperature T of 50°C or higher and 105°C or lower in a reactor and / or a retention tank, obtaining the liquid L by subjecting a reaction mixture containing the (meth)acrylic acid ester and the esterification product of the esterification catalyst or a liquid obtained from the reaction mixture to an organic solvent-cutting treatment (for example, a toluene-cutting treatment).

[0143] It is particularly preferable that the method for producing a (meth)acrylic acid ester according to one embodiment of the present invention satisfies the following (A), (B), and (C): (A) contacting the liquid L with water in the reactor and / or retention tank includes contacting the liquid L with water for a retention time of 3 hours to 10 hours in a state where the set temperature is set to a temperature in the range of 95°C to 105°C and the temperature T is maintained within a range of the set temperature ±5°C; (B) the mass ratio of water to the total mass of the liquid L and water contacted in the reactor and / or retention tank is 20 mass% or more and 60 mass% or less; (C) The method for producing the (meth)acrylic acid ester includes, before contacting liquid L with water at a temperature T in a reactor and / or a retention tank, subjecting a reaction mixture containing the (meth)acrylic acid ester and an esterification product of the esterification catalyst or a liquid obtained from the reaction mixture to an organic solvent-cutting treatment (e.g., toluene-cutting treatment) to obtain liquid L.

[0144] In (B), the mass ratio of water to the total mass of liquid L and water is preferably 25% by mass or more and 60% by mass or less, more preferably 30% by mass or more and 60% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less. In (B), the mass ratio of water to the total mass of liquid L and water may be 30% by mass or more and 40% by mass or less.

[0145] According to the method for producing a (meth)acrylic acid ester of the present invention, the (meth)acrylic acid ester can be produced in high yield.

[0146] The (meth)acrylic acid ester obtained by the method for producing a (meth)acrylic acid ester according to the present invention can be used as a raw material for, for example, vibration-damping materials, printing toners, inks, paints, pressure-sensitive adhesives, adhesives, baking binders, synthetic resins, coating agents, dispersants, fiber treatment agents, etc., but the uses of the (meth)acrylic acid ester are not limited to these.

[0147] Although the embodiments of the present invention have been described in detail, it is clear that this is by way of illustration and example only and not of limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0148] The present invention encompasses the following aspects and configurations: 1. A method for producing a (meth)acrylic acid ester, comprising: Reacting (meth)acrylic acid with a secondary alcohol in a reactor in the presence of an acid-type esterification catalyst and a polymerization inhibitor; a method for producing a (meth)acrylic acid ester, comprising: bringing a liquid L containing an esterification product of the esterification catalyst, obtained during the production of the (meth)acrylic acid ester, into contact with water at a temperature T of 50°C or higher and 105°C or lower in the reactor and / or residence tank; 2. The production method according to 1 above, wherein the contact of the liquid L with the water in the reactor and / or the retention tank comprises contacting the liquid L with the water for a retention time of 0.5 hours to 100 hours in a state where the set temperature is set to a temperature in the range of 55°C to 100°C and the temperature T is maintained within a range of the set temperature ±5°C; 3. The manufacturing method according to 1. or 2., wherein the temperature T is greater than 80°C and not greater than 105°C; 4. The production method according to any one of 1. to 3., wherein the ratio of the mass of the water to the total mass of the liquid L and the water is 10 mass% or more; 5. Separating a mixture containing the liquid L and the water into an organic phase containing the (meth)acrylic acid ester and an aqueous phase containing the esterification catalyst by contacting the liquid L with the water in the reactor and / or the residence tank; the production method according to any one of 1. to 4., which comprises removing a part or all of the aqueous phase; 6. The production method according to any one of 1. to 5., wherein the contact of the liquid L with the water in the reactor and / or the retention tank includes using as the liquid L a liquid obtained by subjecting a reaction mixture containing the (meth)acrylic acid ester and the esterified product to a neutralization treatment and a water-washing treatment, and contacting the liquid (i.e., the liquid obtained by the neutralization treatment and the water-washing treatment) with the water at the temperature T; 7. The contacting of the liquid L with the water in the reactor and / or the retention tank includes using a liquid obtained by subjecting a reaction mixture containing the (meth)acrylic acid ester and the esterified product to a neutralization treatment and a water-washing treatment as the liquid L, and contacting the liquid (i.e., the liquid obtained by the neutralization treatment and the water-washing treatment) with the water at the temperature T; The production method according to any one of 1. to 5., further comprising supplying the reaction mixture obtained after the treatment including the contacting to a distillation column and distilling the mixture; 8. The production method includes subjecting a reaction mixture containing the (meth)acrylic acid ester and the esterified product to treatments including a neutralization treatment and a water-washing treatment; further comprising distilling the reaction mixture obtained after the treatments, including the neutralization treatment and the water washing treatment; 6. The production method according to any one of 1. to 5., wherein the contact of the liquid L with the water in the reactor and / or the retention tank includes contacting the distilled liquid with the water at the temperature T in the retention tank using the distilled liquid as the liquid L; 9. The production method includes subjecting a reaction mixture containing the (meth)acrylic acid ester and the esterified product to treatments including a neutralization treatment and a water-washing treatment; supplying the reaction mixture obtained after the treatments including the neutralization treatment and the water washing treatment to a distillation column and distilling the mixture; and Further comprising withdrawing the bottoms liquid from the bottom of the distillation column; 6. The production method according to any one of 1. to 5., wherein the contact of the liquid L with the water in the reactor and / or the residence tank includes contacting the bottom liquid with the water in the residence tank at the temperature T using the bottom liquid as the liquid L; 10. The method according to any one of 1. to 9., wherein the secondary alcohol is 2-octanol.

[0149] 11. The production method according to any one of 1. to 10., wherein the acid-type esterification catalyst is a sulfur-containing acid-type esterification catalyst.

[0150] 12. The method according to any one of items 1 to 11 above, wherein the purity of the (meth)acrylic acid ester is 99.9% by mass or more. [Example]

[0151] The effects of the present invention will be explained using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. In the following examples, unless otherwise specified, operations were performed at room temperature (25±5°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0152] (Example 1-1) [Reaction process] A 5 L glass round-bottom flask equipped with a stirrer was charged with 1200 g of acrylic acid, 2385 g of 2-octanol (1.1 moles per mole of acrylic acid), 400 g of toluene, 40 g of a 70% by mass aqueous solution of methanesulfonic acid, and 6 g of phenothiazine. The round-bottom flask was then immersed in an oil bath to heat the liquid in the round-bottom flask.

[0153] The round-bottom flask was removed from the oil bath after the liquid temperature in the round-bottom flask reached 110°C and was maintained at this temperature for 8 hours. The liquid was then cooled to terminate the esterification reaction. This procedure yielded a reaction mixture. The pressure in the round-bottom flask was gradually reduced from 800 hPa to 180 hPa so that the liquid temperature in the round-bottom flask remained at 110°C.

[0154] After the reaction was completed, the reaction mixture in the round-bottom flask was analyzed using gas chromatography (GC). As a result, it was confirmed that in addition to the reaction product (target product), 1-methylheptyl acrylate, an esterified product (sulfonic acid ester) of the esterification catalyst was also produced.

[0155] [Neutralization process and washing process] Next, the reaction mixture obtained in the reaction step was cooled to 40°C, and then 3756 g of the reaction mixture obtained in the reaction step and 1000 g of a 5% by mass aqueous sodium hydroxide solution were charged into a 5 L separatory funnel, followed by stirring for 5 minutes. The mixture was then allowed to stand to separate into oil and water, and only the aqueous phase was extracted from the separatory funnel.

[0156] Then, 1000 g of water was added to the separatory funnel and stirred for 5 minutes. The resulting mixture was then left to stand to separate into oil and water, and only the aqueous phase was removed from the separatory funnel.

[0157] By the above operations, after the neutralization step and the water washing step were completed, a liquid (oil phase) was obtained. The obtained liquid (oil phase) was used in the next step (toluene cutting step).

[0158] In the neutralization step and the water-washing step, the liquid temperature of the mixture containing water was 40°C or lower.

[0159] [Toluene cutting process] Next, 900 g of the liquid (oil phase) obtained after the neutralization step and the water washing step was placed in a 1 L round-bottom flask, and the flask was immersed in an oil bath at 130°C to heat the liquid inside the round-bottom flask and perform simple distillation. The pressure inside the round-bottom flask was gradually reduced from 680 hPa to 90 hPa. The distillate yield in this simple distillation was 15% by mass.

[0160] [Hot water treatment process] Next, 680 g of the liquid (oil phase) obtained after the toluene cutting step and 120 g of water were placed in a 1 L glass round-bottom flask equipped with a stirrer, and the flask was then immersed in an oil bath to heat the liquid in the round-bottom flask.

[0161] The temperature of the oil bath was adjusted so that the set temperature was 100°C, and the temperature of the mixture of the reaction mixture (the liquid obtained after the toluene cutting step) and water in the round-bottom flask was maintained within the range of 95°C or higher and 105°C or lower for 5 hours, starting from the time when the temperature reached 95°C. The round-bottom flask was then removed from the oil bath and cooled.

[0162] After cooling, the liquid in the round-bottom flask was transferred to a separatory funnel and left to stand to separate the oil and water, after which only the oil phase was removed from the separatory funnel.

[0163] By the above operations, a liquid (oil phase) was obtained after the hot water treatment step was completed.

[0164] (Example 1-2) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 90°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 85°C to 95°C was 21 hours, starting from the time when the temperature reached 85°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1.

[0165] (Examples 1-3) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 80°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period within the range of 75°C to 85°C was 33 hours, starting from the time when the temperature reached 75°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1.

[0166] (Examples 1-4) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 70°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 65°C or higher and 75°C or lower was 43 hours, starting from the time when the temperature reached 65°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1.

[0167] (Examples 1-5) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 60°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 55°C to 65°C was 62 hours, starting from the time when the temperature reached 55°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1.

[0168] (Examples 1 to 6) A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1, except that in the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 50°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time during which the temperature remained within the range of 45°C to 55°C was 89 hours, starting from the time when the temperature reached 45°C. In Example 1-6, when the set temperature was 50°C in the hot water treatment step and the temperature of the mixture of the reaction mixture and water was maintained, there was a time during which the temperature remained within the range of 50°C to 55°C.

[0169] (Examples 1-7) In the hot water treatment step, a liquid (oil phase) was obtained after the hot water treatment step in the same manner as in Example 1-1, except that 720 g of the liquid (oil phase) obtained after the toluene cutting step and 80 g of water were charged into a 1 L glass round-bottom flask equipped with a stirrer.

[0170] (Examples 1-8) In the hot water treatment step, a liquid (oil phase) was obtained after the hot water treatment step in the same manner as in Example 1-1, except that 640 g of the liquid (oil phase) obtained after the toluene cutting step and 160 g of water were charged into a 1 L glass round-bottom flask equipped with a stirrer.

[0171] (Examples 1-9) In the hot water treatment step, a liquid (oil phase) was obtained after the hot water treatment step in the same manner as in Example 1-1, except that 480 g of the liquid (oil phase) obtained after the toluene cutting step and 320 g of water were charged into a 1 L glass round-bottom flask equipped with a stirrer.

[0172] (Examples 1-10) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 90°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 85°C to 95°C was 5 hours, starting from the time when the temperature reached 85°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1.

[0173] (Examples 1-11) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 80°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 75°C to 85°C was 5 hours, starting from the time when the temperature reached 75°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1.

[0174] (Examples 1-12) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 70°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 65°C to 75°C was 5 hours, starting from the time when the temperature reached 65°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1.

[0175] (Examples 1-13) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 60°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period during which the temperature remained within the range of 55°C to 65°C was 5 hours, starting from the time when the temperature reached 55°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1.

[0176] (Examples 1-14) A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 1-1, except that in the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 50°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time during which the temperature remained within the range of 45°C to 55°C was 5 hours, starting from the time when the temperature reached 45°C. In Example 1-14, when the set temperature was 50°C in the hot water treatment step and the temperature of the mixture of the reaction mixture and water was maintained, there was a time during which the temperature remained within the range of 50°C to 55°C.

[0177] (Examples 1-15) In the hot water treatment step, the set temperature was set to 100°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time during which the temperature remained within the range of 95°C or higher and 105°C or lower was 0.1 hours, starting from the time when the temperature reached 95°C. The same procedure as in Example 1-1 was repeated, except that a liquid (oil phase) was obtained after the hot water treatment step.

[0178] (Comparative Example 1-1) A liquid (oil phase) was obtained after the toluene cutting step was completed in the same manner as in Example 1-1, except that the hot water treatment step was not carried out.

[0179] (Comparative Example 1-2) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 40°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period during which the temperature remained within the range of 35°C to 45°C was 5 hours, starting from the time when the temperature reached 35°C. In the hot water treatment step of Comparative Example 1-2, the temperature of the mixture of the reaction mixture and water never exceeded 45°C.

[0180] (Comparative Examples 1-3) In the hot water treatment step, the set temperature was set to 100°C, and 800 g of only the liquid (oil phase) obtained after the toluene cutting step was placed in a 1 L glass round-bottom flask equipped with a stirrer. The temperature of the reaction mixture in the round-bottom flask was maintained so that the time period within the range of 95°C to 105°C was 5 hours, starting from the time when the temperature reached 95°C. In the same manner as in Example 1-1, a liquid (oil phase) was obtained after the hot water treatment step.

[0181] Example 2-1 [Reaction process] A 5 L glass round-bottom flask equipped with a stirrer was charged with 1200 g of methacrylic acid, 2000 g of 2-octanol (1.1 moles per mole of methacrylic acid), 400 g of toluene, 80 g of a 70% by mass aqueous solution of methanesulfonic acid, and 6 g of phenothiazine. The round-bottom flask was then immersed in an oil bath to heat the liquid in the round-bottom flask.

[0182] The round-bottom flask was removed from the oil bath after the liquid temperature in the round-bottom flask reached 120°C and was maintained at this temperature for 9 hours. The liquid was then cooled to terminate the esterification reaction. This procedure yielded a reaction mixture. The pressure in the round-bottom flask was gradually reduced from 850 hPa to 330 hPa so that the liquid temperature in the round-bottom flask was maintained at 120°C.

[0183] After the reaction was completed, the reaction mixture in the round-bottom flask was analyzed using gas chromatography (GC). As a result, it was confirmed that in addition to the reaction product (target product), 1-methylheptyl methacrylate, an ester (sulfonic acid ester) of the esterification catalyst had also been produced.

[0184] [Neutralization process and washing process] Next, the reaction mixture obtained in the reaction step was cooled to 40°C, and then 3500 g of the reaction mixture obtained in the reaction step and 1000 g of a 5% by mass aqueous sodium hydroxide solution were charged into a 5 L separatory funnel, followed by stirring for 5 minutes. The mixture was then allowed to stand to separate into oil and water, and only the aqueous phase was extracted from the separatory funnel.

[0185] Then, 1000 g of water was added to the separatory funnel and stirred for 5 minutes. The resulting mixture was then left to stand to separate into oil and water, and only the aqueous phase was removed from the separatory funnel.

[0186] By the above operations, after the neutralization step and the water washing step were completed, a liquid (oil phase) was obtained. The obtained liquid (oil phase) was used in the next step (toluene cutting step).

[0187] In the neutralization step and the water-washing step, the liquid temperature of the mixture containing water was 40°C or lower.

[0188] [Toluene cutting process] Next, 900 g of the liquid (oil phase) obtained after the neutralization step and the water washing step was placed in a 1 L round-bottom flask, and the flask was immersed in an oil bath at 130°C to heat the liquid inside the round-bottom flask and perform simple distillation. The pressure inside the round-bottom flask was gradually reduced from 680 hPa to 90 hPa. The distillate yield in this simple distillation was 20% by mass.

[0189] [Hot water treatment process] Next, 680 g of the liquid (oil phase) obtained after the toluene cutting step and 120 g of water were placed in a 1 L glass round-bottom flask equipped with a stirrer, and the flask was then immersed in an oil bath to heat the liquid in the round-bottom flask.

[0190] The temperature of the oil bath was adjusted so that the set temperature was 100°C, and the temperature of the mixture of the reaction mixture (the liquid obtained after the toluene cutting step) and water in the round-bottom flask was maintained within the range of 95°C or higher and 105°C or lower for 5 hours, starting from the time when the temperature reached 95°C. The round-bottom flask was then removed from the oil bath and cooled.

[0191] After cooling, the liquid in the round-bottom flask was transferred to a separatory funnel and left to stand to separate the oil and water, after which only the oil phase was removed from the separatory funnel.

[0192] By the above operations, a liquid (oil phase) was obtained after the hot water treatment step was completed.

[0193] (Example 2-2) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 90°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 85°C to 95°C was 21 hours, starting from the time when the temperature reached 85°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1.

[0194] (Example 2-3) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 80°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period within the range of 75°C to 85°C was 33 hours, starting from the time when the temperature reached 75°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1.

[0195] (Examples 2-4) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 70°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period within the range of 65°C to 75°C was 43 hours, starting from the time when the temperature reached 65°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1.

[0196] (Examples 2-5) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 60°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 55°C to 65°C was 62 hours, starting from the time when the temperature reached 55°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1.

[0197] (Examples 2-6) A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1, except that in the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 50°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time during which the temperature remained within the range of 45°C to 55°C was 89 hours, starting from the time when the temperature reached 45°C. In Example 2-6, when the set temperature was 50°C in the hot water treatment step and the temperature of the mixture of the reaction mixture and water was maintained, there was a time during which the temperature remained within the range of 50°C to 55°C.

[0198] (Examples 2-7) In the hot water treatment step, 680 g of the liquid (oil phase) obtained after the neutralization step and the water washing step and 120 g of water were charged into a 1 L glass round-bottom flask equipped with a stirrer, and a liquid (oil phase) was obtained after the hot water treatment step in the same manner as in Example 2-1, except that the toluene cutting step was performed after the hot water treatment step rather than before.

[0199] (Examples 2-8) In the hot water treatment step, a liquid (oil phase) was obtained after the hot water treatment step in the same manner as in Example 2-1, except that 560 g of the liquid (oil phase) obtained after the toluene cutting step and 240 g of water were charged into a 1 L glass round-bottom flask equipped with a stirrer.

[0200] (Examples 2-9) In the hot water treatment step, a liquid (oil phase) was obtained after the hot water treatment step in the same manner as in Example 2-1, except that 480 g of the liquid (oil phase) obtained after the toluene cutting step and 320 g of water were charged into a 1 L glass round-bottom flask equipped with a stirrer.

[0201] (Examples 2-10) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 90°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 85°C to 95°C was 5 hours, starting from the point when the temperature reached 85°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1.

[0202] (Example 2-11) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 80°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 75°C to 85°C was 5 hours, starting from the time when the temperature reached 75°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1.

[0203] (Example 2-12) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 70°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 65°C to 75°C was 5 hours, starting from the time when the temperature reached 65°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1.

[0204] (Example 2-13) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 60°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period in which the temperature remained within the range of 55°C to 65°C was 5 hours, starting from the time when the temperature reached 55°C. A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1.

[0205] (Example 2-14) A liquid (oil phase) was obtained after the hot water treatment step was completed in the same manner as in Example 2-1, except that in the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 50°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time during which the temperature remained within the range of 45°C to 55°C was 5 hours, starting from the time when the temperature reached 45°C. In Example 2-14, when the set temperature was 50°C in the hot water treatment step and the temperature of the mixture of the reaction mixture and water was maintained, there was a time during which the temperature remained within the range of 50°C to 55°C.

[0206] (Example 2-15) In the hot water treatment step, the set temperature was set to 100°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time during which the temperature remained within the range of 95°C or higher and 105°C or lower was 0.1 hours, starting from the time when the temperature reached 95°C. The same procedure as in Example 2-1 was repeated, except that a liquid (oil phase) was obtained after the hot water treatment step was completed.

[0207] (Example 2-16) In the hot water treatment step, the set temperature was set to 100°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time it took for the temperature to be within the range of 95°C or higher and 105°C or lower was 0.5 hours, starting from the time when the temperature reached 95°C. The same procedure was followed as in Example 2-1, except that a liquid (oil phase) was obtained after the hot water treatment step was completed.

[0208] (Comparative Example 2-1) A liquid (oil phase) was obtained after the toluene cutting step was completed in the same manner as in Example 2-1, except that the hot water treatment step was not carried out.

[0209] (Comparative Example 2-2) In the hot water treatment step, the temperature of the oil bath was changed so that the set temperature was 40°C, and the temperature of the mixture of the reaction mixture and water in the round-bottom flask was maintained so that the time period during which the temperature remained within the range of 35°C to 45°C was 5 hours, starting from the time when the temperature reached 35°C. In the hot water treatment step of Comparative Example 2-2, the temperature of the mixture of the reaction mixture and water never exceeded 45°C.

[0210] (Comparative Example 2-3) In the hot water treatment step, the set temperature was set to 100°C, and 800 g of only the liquid (oil phase) obtained after the toluene cutting step was placed in a 1 L glass round-bottom flask equipped with a stirrer. The temperature of the reaction mixture in the round-bottom flask was maintained so that the time period within the range of 95°C to 105°C was 5 hours, starting from the time when the temperature reached 95°C. In the same manner as in Example 2-1, a liquid (oil phase) was obtained after the hot water treatment step.

[0211] (evaluation) The liquid (oil phase) obtained after the hot water treatment step in the Example, the liquid (oil phase) obtained after the toluene cut step in the Comparative Example, and the liquid (oil phase) obtained after the hot water treatment step in the Comparative Example were quantitatively analyzed for 2-octanol according to the following method.

[0212] [Quantitative analysis of 2-octanol (pretreatment)] (concentrated) 100 g of the liquid (oil phase) obtained after the hot water treatment step in this example was placed in a round-bottom flask and subjected to simple distillation at an operating pressure of 68 hPa. The simple distillation was stopped when the amount of distillate reached 75 g.

[0213] Similarly, 100 g of the liquid (oil phase) obtained in the comparative example was placed in a round-bottom flask and subjected to simple distillation at an operating pressure of 68 hPa. The simple distillation was stopped when the amount of distillate reached 75 g.

[0214] (heating) 25 g of the liquid remaining in the round-bottom flask after concentration was aged at 135° C. for 6 hours. The liquid after aging was quantitatively analyzed for 2-octanol by the following method.

[0215] [Quantitative analysis of 2-octanol] The 2-octanol concentration (mass%) in the liquid was measured by quantitatively analyzing the 2-octanol using gas chromatography (GC). The conditions for the quantitative analysis were as follows: Gas chromatography: Shimadzu Corporation GC-2014 Column: Agilent Technologies DB-1 (column length 30 m, inner diameter 0.25 mm, film thickness 0.25 μm) Column temperature: 70℃ Carrier gas: He.

[0216] The results obtained are shown as "secondary alcohol concentration after aging under heat" in Tables 1 to 4. In this evaluation, a small value for "secondary alcohol concentration after aging under heat" indicates a high yield of (meth)acrylic acid ester.

[0217] [Table 1]

[0218] [Table 2]

[0219] [Table 3]

[0220] [Table 4]

[0221] (Example 3-1) The liquid (oil phase) obtained after the hot water treatment step in Example 1-1 was purified according to the following method to obtain 1-methylheptyl acrylate with a purity of 99.94% by mass.

[0222] The liquid (oil phase) obtained after the hot water treatment step was supplied to the top of a light-ends cut column. The light-ends cut column was an Oldershaw distillation column with 20 plates, and low boiling points were removed while controlling the operating pressure to 20 to 30 hPa and the reflux ratio to 10 to 20 so that the distillate yield was 5 to 15% by mass. Next, the bottom liquid from the light-ends cut column was supplied to the bottom of a heavy-ends cut column. The heavy-ends cut column was an Oldershaw distillation column with 20 plates, and high boiling points were removed while controlling the operating pressure to 20 to 30 hPa and the reflux ratio to 0.1 to 0.5 so that the distillate yield was 65 to 75% by mass. Through the above operation, 1-methylheptyl acrylate (3-1) with a purity of 99.94% by mass was obtained.

[0223] (Comparative Example 3-1) In Example 3-1, the same operation as in Example 3-1 was carried out, except that the liquid (oil phase) obtained in Example 1-1 was changed to the liquid (oil phase) obtained in Comparative Example 1-1, thereby obtaining 1-methylheptyl acrylate (C3-1) with a purity of 99.34 mass%.

[0224] (evaluation) The flash point and purity of the 1-methylheptyl acrylate obtained in Example 3-1 and Comparative Example 3-1 were determined according to the following methods.

[0225] (flash point) The flash point of 1-methylheptyl acrylate was determined by Cleveland open-type flash point determination.

[0226] (purity) The purity of 1-methylheptyl acrylate was calculated using the following formula. The 2-octene in 1-methylheptyl acrylate and the 2-octanol in 1-methylheptyl acrylate were quantitatively analyzed using gas chromatography (GC) to determine their contents (ppm by mass). The acid content in 1-methylheptyl acrylate was determined by neutralization titration with 0.1N NaOH (quantitatively determined as acrylic acid) to determine its content (ppm by mass).

[0227]

number

[0228] The evaluation results of the flash point and purity of 1-methylheptyl acrylate are shown in Table 5. In Table 5, the flash point of 1-methylheptyl acrylate is listed as "flash point," and the purity of 1-methylheptyl acrylate is listed as "purity."

[0229] [Table 5]

[0230] Comparison of each Example with each Comparative Example in Tables 1 to 4 shows that the secondary alcohol concentration (mass %) after thermal aging was reduced by the method for producing a (meth)acrylic acid ester, which includes contacting a liquid L containing an esterified product of an esterification catalyst obtained during the production of a (meth)acrylic acid ester with water in a reactor and / or residence tank at a temperature T of 50° C. or higher and 105° C. or lower. This indicates that the yield of the (meth)acrylic acid ester was significantly improved.

[0231] Furthermore, the higher the temperature T, the lower the secondary alcohol concentration (mass%) after heating. This confirmed that the (meth)acrylic acid ester was produced in a higher yield in a shorter period of time.

[0232] Furthermore, by controlling the mass of water relative to the total mass of liquid L and water, the secondary alcohol concentration (mass%) after thermal aging was further reduced, confirming that the (meth)acrylic acid ester was produced in a higher yield.

[0233] A comparison between Example 3-1 and Comparative Example 3-1 in Table 5 confirms that the purity of the (meth)acrylic acid ester is improved when the method for producing a (meth)acrylic acid ester includes contacting, in a reactor and / or a residence tank, a liquid L containing an esterified product of an esterification catalyst obtained during the production of the (meth)acrylic acid ester with water at a temperature T of 50°C or higher and 105°C or lower.

[0234] A comparison of Example 3-1 and Comparative Example 3-1 in Table 5 confirmed that the flash point of 1-methylheptyl acrylate of Example 3-1, which was subjected to the hot water treatment step, was higher than the flash point of 1-methylheptyl acrylate of Comparative Example 3-1, which was not subjected to the hot water treatment. This is thought to be because the (meth)acrylic ester was produced through a hot water treatment step that included contacting water with a liquid L containing an esterification product of an acid-type esterification catalyst obtained during the production of a (meth)acrylic ester, thereby reducing low-boiling substances (e.g., raw material (meth)acrylic acid, secondary alcohol, by-product alkene, or a combination thereof), and a high-purity (meth)acrylic ester was obtained.

[0235] In addition, in this example, a (meth)acrylic acid ester was produced using a glass round-bottom flask equipped with a stirrer, etc., but it is presumed that the effects of the present invention can be similarly obtained when the present invention is applied to a (meth)acrylic acid ester production process such as those shown in Figures 1 to 6.

[0236] This application is based on Japanese Patent Application No. 2022-185007, filed on November 18, 2022, the disclosure of which is incorporated by reference in its entirety. [Explanation of symbols]

[0237] 1: reactor, 2: first distillation column, 3, 3': Retention tank, 4: second distillation column, 5: third distillation column, 6: Processing equipment, 7: Neutralization washing tank.

Claims

1. A method for producing a (meth)acrylic acid ester, comprising: Reacting (meth)acrylic acid with a secondary alcohol in a reactor in the presence of an acid-type esterification catalyst and a polymerization inhibitor; contacting a liquid L containing an ester of the esterification catalyst, obtained during the production of the (meth)acrylic ester, with water at a temperature T of 75°C or higher and 105°C or lower in the reactor and / or residence tank.

2. 2. The production method according to claim 1, wherein the contact of the liquid L with the water in the reactor and / or the retention tank comprises contacting the liquid L with the water for a holding time of 0.5 hours to 100 hours in a state where the temperature T is maintained within a range of ±5°C of the set temperature, when the set temperature is set within a range of 80°C to 100°C.

3. The manufacturing method according to claim 1 , wherein the temperature T is greater than 80° C. and equal to or less than 105° C.

4. The method according to claim 1 , wherein the ratio of the mass of the water to the total mass of the liquid L and the water is 10 mass % or more.

5. the liquid L is brought into contact with the water in the reactor and / or the residence tank, thereby separating a mixture containing the liquid L and the water into an organic phase containing the (meth)acrylic acid ester and an aqueous phase containing the esterification catalyst; The process of claim 1 , further comprising removing some or all of the aqueous phase.

6. the contacting of the liquid L with the water in the reactor and / or the retention tank includes using, as the liquid L, a liquid obtained by subjecting a reaction mixture containing the (meth)acrylic acid ester and the esterified product to a neutralization treatment and a water-washing treatment, and contacting the liquid with the water at the temperature T; The method according to claim 1 , further comprising supplying the reaction mixture obtained after the treatment including the contacting to a distillation column for distillation.

7. The production method includes subjecting a reaction mixture containing the (meth)acrylic acid ester and the esterified product to treatments including a neutralization treatment and a water-washing treatment; supplying the reaction mixture obtained after the treatments including the neutralization treatment and the water washing treatment to a distillation column and distilling the mixture; and Further comprising withdrawing the bottoms liquid from the bottom of the distillation column; 2. The production method according to claim 1, wherein the contact of the liquid L with the water in the reactor and / or the residence tank comprises using the bottom liquid as the liquid L and contacting the bottom liquid with the water in the residence tank at the temperature T.

8. The method of claim 1, wherein the secondary alcohol is 2-octanol.

9. The method according to claim 1 , wherein the purity of the (meth)acrylic acid ester is 99.9% by mass or more.

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