Method for producing (METH)acrylic acid compound

Abstract

A method for producing a (meth)acrylic acid compound using a hydroxycarboxylic acid and / or a polymer thereof as a raw material, the production method comprising at least a reaction step for heating and reacting a mixture comprising a hydroxycarboxylic acid and / or a polymer thereof, a basic catalyst, and a carboxylic anhydride to produce a (meth)acrylic acid compound.

Description

Method for producing (meth)acrylic acid compound

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

[0002] (Meth)acrylic acid compounds are compounds that are widely used as raw materials for synthesizing poly(meth)acrylic acid resins, etc. As methods for producing (meth)acrylic acid compounds, production methods using a polymer of 3-hydroxycarboxylic acid as a raw material have been investigated. Examples of known methods include a method for producing (meth)acrylic acid by heating and / or contacting with a catalyst a composition containing a specific polymer of 3-hydroxycarboxylic acid (Patent Document 1), a method for producing (meth)acrylic acid by heating a raw material composition containing a predetermined amount of polymer of 3-hydroxycarboxylic acid to generate a gaseous decomposition product of the 3-hydroxycarboxylic acid polymer, and then contacting the decomposition product with a dehydration catalyst (Patent Document 2), and a method for producing (meth)acrylic acid by heating a raw material composition containing a predetermined amount of polymer of 3-hydroxycarboxylic acid having a degree of polymerization of 3- to 20-mers (Patent Document 3).

[0003] International Publication No. 2014 / 002886 Japanese Patent Application Laid-Open No. 2014-156449 Japanese Patent Application Laid-Open No. 2014-156450

[0004] All of the conventionally known methods for producing (meth)acrylic acid from a composition containing a polymer of 3-hydroxycarboxylic acid have been carried out by decomposing and dehydrating the polymer of 3-hydroxycarboxylic acid, and have required harsh reaction conditions such as the use of a strong dehydration catalyst and heating at a high temperature.

[0005] An object of the present invention is to provide a novel production method that enables the production of a (meth)acrylic acid compound from a hydroxycarboxylic acid and / or a polymer thereof.

[0006] The present inventors have conducted extensive research into a method for producing (meth)acrylic acid from a composition containing a hydroxycarboxylic acid and / or a polymer thereof, and as a result have found that a (meth)acrylic acid compound can be produced by heating a mixture containing a hydroxycarboxylic acid and / or a polymer thereof, a basic catalyst, and a carboxylic acid anhydride to cause a reaction, thereby completing the present invention.

[0007] That is, the present invention relates to the following items [1] to

[15] . [1] A method for producing a (meth)acrylic acid compound using a hydroxycarboxylic acid and / or a polymer thereof as a raw material, comprising at least a reaction step of heating a mixture containing a hydroxycarboxylic acid and / or a polymer thereof, a basic catalyst, and a carboxylic acid anhydride to react with each other to produce a (meth)acrylic acid compound, wherein (1) the mixture further contains a carboxylic acid anhydride, and / or (2) the weight-average molecular weight of the polymer of the hydroxycarboxylic acid contained in the raw material is 10,000 or more. [2] A method for producing a (meth)acrylic acid compound using a 3-hydroxycarboxylic acid and / or a polymer thereof as a raw material, comprising at least a reaction step of heating a mixture containing a 3-hydroxycarboxylic acid and / or a polymer thereof, a basic catalyst, and a carboxylic acid anhydride to react with each other to produce a (meth)acrylic acid compound. [3] The method according to [1], wherein the hydroxycarboxylic acid is at least one selected from the group consisting of a 2-hydroxycarboxylic acid and a 3-hydroxycarboxylic acid. [4] The method according to any one of [1] to [3], wherein the carboxylic acid anhydride is (meth)acrylic acid anhydride. [5] The (meth)acrylic acid anhydride is represented by the formula (I): [In formula (I), R １ ~R ３each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. [6] The method according to any one of [1] to [5], wherein the basic catalyst is selected from the group consisting of alkali metal carboxylates, quaternary ammonium carboxylates, and ammonium betaine. [7] The method according to any one of [1] to [6], wherein the basic catalyst is at least one alkali metal carboxylate selected from the group consisting of alkali metal salts of α,β-ethylenically unsaturated monocarboxylic acids and alkali metal salts of aliphatic monocarboxylic acids. [8] The method according to any one of [1] to [7], wherein the basic catalyst is at least one alkali metal carboxylate selected from the group consisting of alkali metal (meth)acrylic acid salts and alkali metal acetate salts. [9] The method according to any one of [1] to [8], wherein the amount of the basic catalyst in the mixture is 0.1 to 20 parts by mass per 100 parts by mass of the total of the hydroxycarboxylic acid and its polymer.

[10] The method according to any one of [1] to [9], wherein the amount of the carboxylic acid anhydride in the mixture is 1 to 50 parts by mass relative to 100 parts by mass of the total of the hydroxycarboxylic acid and its polymer.

[11] The method according to any one of [1] to

[10] , wherein the heating temperature in the reaction step is 80 to 220°C.

[12] The hydroxycarboxylic acid is 3-hydroxypropionic acid, and the carboxylic acid anhydride is R １ ~R ３ is a hydrogen atom, or R １ , R ２ is a hydrogen atom and R ３

[14] The production method according to any one of [1] to

[13] , wherein the mixture further contains a polymerization inhibitor.

[15] The production method according to any one of [1] to

[14] , wherein the weight-average molecular weight of a polymer of a hydroxycarboxylic acid contained in the raw material is 10,000 or more, and the water content of the mixture is 0 to 15% by mass based on the total amount of the mixture.

[16] The production method according to any one of [1] to

[15] , further comprising a step of distilling off the (meth)acrylic acid compound produced in the reaction step.

[0008] According to the present invention, a novel production method can be provided that enables the production of a (meth)acrylic acid compound from a hydroxycarboxylic acid and / or a polymer thereof.

[0009] 1 is a diagram showing an HPLC chart of raw material (A) containing 3-hydroxypropionic acid and its polymer obtained in Production Example 1. FIG. 2 is a diagram showing an HPLC chart of reaction product (1) obtained in Example 1. FIG. 3 is a diagram showing an HPLC chart of the distillate obtained in Example 3. １ 1 is a diagram showing a H-NMR chart of the reaction product (3) obtained in Example 3. 2 is a diagram showing an HPLC chart of the reaction product (3) obtained in Example 3. １ FIG. 1 is a diagram showing a H-NMR chart.

[0010] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0011] The production method of the present invention is a method for producing a (meth)acrylic acid compound using a hydroxycarboxylic acid and / or a polymer thereof as a raw material, and includes at least a reaction step of heating a mixture containing a hydroxycarboxylic acid and / or a polymer thereof, a basic catalyst, and a hydroxycarboxylic acid to react with each other to produce a (meth)acrylic acid compound, wherein (1) the mixture further contains a carboxylic acid anhydride, and / or (2) the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more. In the production method of the present invention, by heating the mixture, the raw material hydroxycarboxylic acid and / or a polymer thereof and the basic catalyst, optionally together with the carboxylic acid anhydride, react to produce a (meth)acrylic acid compound. The production method of the present invention may satisfy the above-mentioned (1), (2), or both (1) and (2). Examples of the hydroxycarboxylic acid include 2-hydroxycarboxylic acid and 3-hydroxycarboxylic acid. In the production method of the present invention, when condition (1) is satisfied, 2-hydroxycarboxylic acids and polymers thereof, 3-hydroxycarboxylic acids and polymers thereof, polymers of 2-hydroxycarboxylic acids and 3-hydroxycarboxylic acids, and mixtures thereof can be suitably used. Furthermore, when condition (2) is satisfied, polymers of 2-hydroxycarboxylic acids having a weight-average molecular weight of 10,000 or more, polymers of 3-hydroxycarboxylic acids having a weight-average molecular weight of 10,000 or more, polymers of 2-hydroxycarboxylic acids and 3-hydroxycarboxylic acids having a weight-average molecular weight of 10,000 or more, and mixtures thereof can be suitably used.

[0012] The present inventors have found that in a method for producing a (meth)acrylic acid compound using a hydroxycarboxylic acid and / or a polymer thereof as a raw material, the reaction of the hydroxycarboxylic acid and / or a polymer thereof used as a raw material to give a (meth)acrylic acid compound proceeds efficiently when (1) a carboxylic acid anhydride is further contained, and / or (2) the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more.

[0013] In one aspect, the production method of the present invention is a method for producing a (meth)acrylic acid compound using a 3-hydroxycarboxylic acid and / or a polymer thereof as a raw material, the production method including at least a reaction step of heating a mixture containing: a 3-hydroxycarboxylic acid and / or a polymer thereof; a basic catalyst; and a carboxylic acid anhydride to react with each other and produce a (meth)acrylic acid compound.

[0014] In the production method of the present invention, by heating the mixture, the raw materials, hydroxycarboxylic acid and / or its polymer, a basic catalyst, and a carboxylic acid anhydride, react to produce a (meth)acrylic acid compound. First, (1) Aspect (1) in which the mixture containing a hydroxycarboxylic acid and / or its polymer and a basic catalyst further contains a carboxylic acid anhydride will be described.

[0015] (Hydroxycarboxylic Acid and / or Polymer Thereof) In the production method of the present invention, the hydroxycarboxylic acid and / or polymer thereof is a component that serves as a raw material for providing a (meth)acrylic acid compound. In the production method of the present invention, it is sufficient to use at least one hydroxycarboxylic acid and / or polymer thereof, and only the hydroxycarboxylic acid may be used, only a polymer of the hydroxycarboxylic acid may be used, or a mixture of the hydroxycarboxylic acid and the polymer of the hydroxycarboxylic acid may be used. The hydroxycarboxylic acid may be a single type of hydroxycarboxylic acid or a mixture of two or more types of hydroxycarboxylic acids. The polymer of the hydroxycarboxylic acid may also be a polymer of one type or two or more types of hydroxycarboxylic acids, and the degree of polymerization may be one type or two or more types.

[0016] A 3-hydroxycarboxylic acid is a compound having a carboxylic acid group and at least a hydroxyl group at the β-position of the carbonyl carbon of the carboxylic acid group. Examples of 3-hydroxycarboxylic acids include 3-hydroxypropionic acid, 3-hydroxybutanoic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, and compounds in which the hydrogen atom bonded to the carbon atom of the above 3-hydroxycarboxylic acids is substituted with a substituent such as an alkyl group. A polymer of 3-hydroxycarboxylic acid is, for example, a polymer in which two or more 3-hydroxycarboxylic acids are bonded to each other via an intermolecular ester bond.

[0017] A 2-hydroxycarboxylic acid is a compound having a carboxylic acid group and at least a hydroxyl group at the α-position of the carbonyl carbon of the carboxylic acid group. Examples of 2-hydroxycarboxylic acids include 2-hydroxypropionic acid, 2-hydroxybutanoic acid, 2-hydroxyisobutanoic acid, 2-hydroxypentanoic acid, 2-hydroxyhexanoic acid, and compounds in which the hydrogen atoms bonded to the carbon atoms of the above 2-hydroxycarboxylic acids are substituted with substituents such as alkyl groups. A polymer of 2-hydroxycarboxylic acid is, for example, a polymer in which two or more 2-hydroxycarboxylic acids are bonded to each other via intermolecular ester bonds.

[0018] The hydroxycarboxylic acid polymer may be any polymer in which two or more hydroxycarboxylic acids are polymerized, for example, a multimer in which two or more hydroxycarboxylic acids are ester-bonded. The degree of polymerization and distribution of the multimer are not particularly limited. The hydroxycarboxylic acid polymer may be composed of one type of hydroxycarboxylic acid, or may be composed of two or more types of hydroxycarboxylic acids, or may contain structural units other than hydroxycarboxylic acids. From the viewpoint of efficiently producing a (meth)acrylic acid compound, it is preferable that the hydroxycarboxylic acid polymer contains only hydroxycarboxylic acids as structural units.

[0019] In one embodiment, when the mixture containing a hydroxycarboxylic acid and / or polymer thereof and a basic catalyst further contains a carboxylic acid anhydride, the degree of polymerization of the hydroxycarboxylic acid polymer that can be contained in the mixture is not particularly limited, and hydroxycarboxylic acids with various degrees of polymerization may be used as raw materials. From the viewpoints of availability and manufacturability, the degree of polymerization of the hydroxycarboxylic acid may be, for example, a dimer to 30,000-mer. The content of the dimer to 30,000-mer of hydroxycarboxylic acid relative to 100 parts by mass of the total of the hydroxycarboxylic acid and / or polymer thereof is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. From the same viewpoint, the content of the dimer to 20,000-mer, more preferably 2-15,000-mer, and even more preferably 2-10,000-mer of 3-hydroxycarboxylic acid is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more relative to 100 parts by mass of the total of the hydroxycarboxylic acid and polymer thereof. The content of each polymer relative to 100 parts by mass of the total of hydroxycarboxylic acid and its polymer can be determined by, for example, HPLC and １ It can be calculated from H-NMR or the like.

[0020] In a preferred embodiment, from the viewpoint of production efficiency of the (meth)acrylic acid compound, the content of dimers to 20mers of hydroxycarboxylic acid relative to a total of 100 parts by mass of hydroxycarboxylic acid and its polymer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. From the same viewpoint, the content of preferably dimers to 15mers, more preferably dimers to 10mers of hydroxycarboxylic acid relative to a total of 100 parts by mass of hydroxycarboxylic acid and its polymer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The content of each multimer relative to a total of 100 parts by mass of hydroxycarboxylic acid and its polymer can be determined, for example, by HPLC and １ It can be calculated from H-NMR or the like.

[0021] 3-Hydroxycarboxylic acids and polymers thereof are, for example, represented by the formula (III)-1: [In formula (III)-1, R ４ ~R ６ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n represents an integer of 1 or more.

[0022] When n in formula (III)-1 is 1, the 3-hydroxycarboxylic acid is represented by formula (II)-1: [In formula (II)-1, R ４ ~R ６ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. A compound in which n is 2 or more in formula (III)-1 is a polymer of a 3-hydroxycarboxylic acid represented by formula (II)-1.

[0023] R in formula (II)-1 and formula (III)-1 ４ ~R ６ R each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. ４ ~R ６ each independently preferably represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, more preferably represents a hydrogen atom or a methyl group, and further preferably represents a hydrogen atom. ５ , R ６ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ４ represents a hydrogen atom. In this case, R ５ , R ６ R preferably represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom. ４ ~R ６ The 3-hydroxycarboxylic acid of formula (II)-1, in which represents a hydrogen atom, is also called 3-hydroxypropionic acid.

[0024] In formula (III)-1, n is not particularly limited as long as it is 1 or greater, and it is generally believed that 3-hydroxycarboxylic acids and polymers thereof contain multiple compounds or polymers with different n's. The upper limit of n is not particularly limited, and may be, for example, 30,000 or less, preferably 20,000 or less, more preferably 10,000 or less, 9,000 or less, 8,000 or less, 7,000 or less, 5,000 or less, 3,000 or less, 1,000 or less, or 500 or less. The upper limit of n is not particularly limited, but from the viewpoint of easily enhancing the effect of further including a carboxylic acid anhydride, it may be, for example, 100 or less, 80 or less, 60 or less, 50 or less, 40 or less, or 30 or less. In a preferred embodiment of the present invention, from the viewpoint of production efficiency of the (meth)acrylic acid compound, the proportion of the polymer of 3-hydroxycarboxylic acid represented by formula (III)-1, where n is preferably 2 to 30,000, more preferably n is 2 to 20,000, even more preferably n is 2 to 15,000, and even more preferably 2 to 10,000, relative to 100 parts by mass of the total of 3-hydroxycarboxylic acid and polymer thereof, is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more. Furthermore, from the viewpoint of easily enhancing the effect of further containing a carboxylic acid anhydride, the proportion of the polymer of 3-hydroxycarboxylic acid represented by formula (III)-1, where n is preferably 2 to 20, more preferably n is 2 to 15, and even more preferably n is 2 to 10, relative to 100 parts by mass of the total of 3-hydroxycarboxylic acid and polymer thereof is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more.

[0025] 2-Hydroxycarboxylic acids and polymers thereof are, for example, represented by the formula (III)-2: [In formula (III)-2, R １０ , R １１ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n represents an integer of 1 or more.

[0026] When n in formula (III)-2 is 1, the 2-hydroxycarboxylic acid is represented by formula (II)-2: [In formula (II)-2, R １２ , R １３ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. A compound in which n is 2 or more in formula (III)-2 is a polymer of 2-hydroxycarboxylic acid represented by formula (II)-2.

[0027] R in formula (II)-2 and formula (III)-2 １０ ~R １３ R each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. １０ ~R １３ each independently preferably represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, more preferably represents a hydrogen atom or a methyl group, and further preferably represents a hydrogen atom. １０ , R １１ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. １０ , R １１ R preferably represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, more preferably a hydrogen atom or a methyl group, and even more preferably a methyl group. １２ is CH ２ , R １３ The 2-hydroxycarboxylic acid of formula (II)-2, in which represents a methyl group, is also called 2-hydroxyisobutanoic acid.

[0028] In formula (III)-2, n is not particularly limited as long as it is 1 or greater, and it is generally believed that 2-hydroxycarboxylic acids and polymers thereof contain multiple compounds or polymers with different n's. The upper limit of n is not particularly limited, and may be, for example, 30,000 or less, preferably 20,000 or less, more preferably 10,000 or less, 9,000 or less, 8,000 or less, 7,000 or less, 5,000 or less, 3,000 or less, 1,000 or less, or 500 or less. The upper limit of n is not particularly limited, but from the viewpoint of easily enhancing the effect of further including a carboxylic acid anhydride, it may be, for example, 100 or less, 80 or less, 60 or less, 50 or less, 40 or less, or 30 or less. In a preferred embodiment of the present invention, from the viewpoint of production efficiency of the (meth)acrylic acid compound, the proportion of the polymer of 2-hydroxycarboxylic acid represented by formula (III)-2, where n is preferably 2 to 30,000, more preferably n is 2 to 20,000, even more preferably n is 2 to 15,000, and even more preferably 2 to 10,000, relative to 100 parts by mass of the total of 2-hydroxycarboxylic acid and polymer thereof, is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more. Furthermore, from the viewpoint of easily enhancing the effect of further containing a carboxylic acid anhydride, the proportion of the polymer of 2-hydroxycarboxylic acid represented by formula (III)-2, where n is preferably 2 to 20, more preferably n is 2 to 15, and even more preferably n is 2 to 10, relative to 100 parts by mass of the total of 2-hydroxycarboxylic acid and polymer thereof is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more.

[0029] In another aspect, the production method of the present invention is a method for producing a (meth)acrylic acid compound using a hydroxycarboxylic acid and / or a polymer thereof as a raw material, the method comprising at least a reaction step of heating a mixture containing a hydroxycarboxylic acid and / or a polymer thereof, a basic catalyst, and a hydroxycarboxylic acid and / or a polymer thereof to react with the hydroxycarboxylic acid to produce a (meth)acrylic acid compound, wherein the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more. (2) Aspect (2) in which the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more will be described below. Note that when the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more, it is possible to produce a (meth)acrylic acid compound from a hydroxycarboxylic acid and / or a polymer thereof even if the mixture does not further contain a carboxylic acid anhydride. However, when the mixture further contains a carboxylic acid anhydride, it is possible to produce a (meth)acrylic acid compound more efficiently.

[0030] In this embodiment, the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more. The characteristics of the hydroxycarboxylic acid and its polymer described in the above embodiment (1) also apply to embodiment (2) as long as they are not inconsistent with this characteristic. From the viewpoint of the production efficiency of the (meth)acrylic acid compound when no carboxylic acid anhydride is added, the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is preferably 20,000 or more, more preferably 60,000 or more, even more preferably 70,000 or more, particularly preferably 100,000 or more, and most preferably 130,000 or more. The upper limit of the weight-average molecular weight of the hydroxycarboxylic acid polymer is not particularly limited, but may be, for example, 1,000,000 or less, more preferably 800,000 or less.

[0031] Whether the weight-average molecular weight of the polymer of hydroxycarboxylic acid contained in the raw material is 10,000 or more can be determined, for example, by measuring the weight-average molecular weight in terms of polystyrene by gel permeation chromatography (GPC) using the 3-hydroxycarboxylic acid and / or its polymer used as the raw material as a measurement sample. The measurement conditions for the weight-average molecular weight include those described in the Examples.

[0032] (Method for Producing Hydroxycarboxylic Acid and / or Polymer Thereof) The method for producing hydroxycarboxylic acid is not particularly limited, and it can be produced by a known method.

[0033] The method for producing the 3-hydroxycarboxylic acid polymer is not particularly limited, and for example, the polymer may be chemically synthesized by intermolecularly bonding 3-hydroxycarboxylic acids, or a 3-hydroxycarboxylic acid polymer produced through a fermentation process may be used. For example, a 3-hydroxycarboxylic acid polymer produced by the method described in WO 2011 / 100608 may be used.

[0034] The polymer of 3-hydroxycarboxylic acid may be added to the mixture in the production method of the present invention in the form of a composition containing the polymer of 3-hydroxycarboxylic acid and other by-products, etc., obtained during the production of the polymer of 3-hydroxycarboxylic acid.

[0035] When a polymer of 3-hydroxycarboxylic acid is produced by chemical synthesis, known methods such as those described in Japanese Patent No. 6173314 and Journal of Organic Chemistry, 26(7), pp. 2525-2528, as well as the production methods described in the Examples below, can be used as dehydration condensation methods of 3-hydroxycarboxylic acid.

[0036] When a polymer of 3-hydroxycarboxylic acid is produced through a fermentation process, the polymer is produced by a method such as that described in International Publication No. 2011 / 100608 or International Publication No. 2002 / 42418, and the resulting 3-hydroxycarboxylic acid is dehydrated and condensed by the dehydration condensation method described above. Another method for producing a polymer of 3-hydroxycarboxylic acid is disclosed in Front. Bioeng. Biotechnol., 9: 646995 (2021). It can also be produced using glucose, glycerol, or the like as a raw material.

[0037] The method for producing a polymer of 2-hydroxycarboxylic acid is not particularly limited. For example, the polymer may be chemically synthesized by intermolecularly bonding 2-hydroxycarboxylic acids, or a polymer of 2-hydroxycarboxylic acid produced through a fermentation process may be used.

[0038] The 2-hydroxycarboxylic acid polymer may be added to the mixture in the production method of the present invention in the form of a composition containing the 2-hydroxycarboxylic acid polymer and other by-products obtained during the production of the 2-hydroxycarboxylic acid polymer, for example.

[0039] When a polymer of 2-hydroxycarboxylic acid is produced by chemical synthesis, the method described in WO 2010 / 071019 and the like, as well as the production method described in the Examples below, can be used for polymerization via a lactide derivative of 2-hydroxycarboxylic acid.

[0040] When a polymer of 2-hydroxycarboxylic acid is produced via a fermentation process, the polymer can be produced by producing 2-hydroxycarboxylic acid by a method described in, for example, Applied and Environmental Microbiology, 2017, 83(3), e02622-16, and polymerizing the obtained 2-hydroxycarboxylic acid via the lactide derivative described above.

[0041] The method for producing a polymer of hydroxycarboxylic acid having a weight-average molecular weight of 10,000 or more is not particularly limited, but includes the methods described in the Examples.

[0042] (Basic Catalyst) The basic catalyst acts as a catalyst when producing a (meth)acrylic acid compound using a hydroxycarboxylic acid and / or its polymer as a raw material. The basic catalyst may be any basic substance that acts as a catalyst, and may be any compound containing a basic moiety in its molecular structure. The basic catalyst is not particularly limited, and both soluble and insoluble catalysts in the reaction mixture can be used. The acid dissociation constant (pKa) of the basic catalyst is preferably 0.5 to 40, more preferably 1 to 30, even more preferably 2 to 15, and particularly preferably 3 to 7. A pKa value above a certain level improves reaction efficiency, while a pKa value below a certain level sufficiently suppresses the occurrence of unintended reactions (side reactions). The pKa of the basic catalyst in the present invention refers to the pKa of the conjugate acid, which can be determined by acid-base titration of the conjugate acid. Alternatively, the pKa values ​​listed in Tables 10 and 19 on pages II-317 to II-321 of the "Chemical Handbook: Basics," 4th Revised Edition, may be used. Specific examples of the basic catalyst include carboxylates, amines, inorganic hydroxides, ammonium hydroxides, metal amides, and metal alkoxides, with carboxylates being preferred.More specifically, alkali metal carboxylates (alkali metal salts of α,β-ethylenically unsaturated carboxylic acids, alkali metal salts of aliphatic carboxylic acids, etc.), quaternary ammonium carboxylates (quaternary ammonium salts of α,β-ethylenically unsaturated carboxylic acids, quaternary ammonium salts of aliphatic carboxylic acids, etc.), ammonium betaine, alkali metal hydroxides (for example, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc.), alkaline earth metal hydroxides (magnesium hydroxide, calcium hydroxide, etc.), transition metal hydroxides (copper hydroxide, etc.), alkali metal carbonates (potassium carbonate, sodium carbonate, lithium carbonate, etc.), alkaline earth metal carbonates (magnesium carbonate, calcium carbonate, etc.), Examples of the alkali metal alkoxide include magnesium, calcium carbonate, barium carbonate, etc.), alkali metal hydrogen carbonates (potassium hydrogen carbonate, sodium hydrogen carbonate, lithium hydrogen carbonate, etc.), alkaline earth metal hydrogen carbonates (magnesium hydrogen carbonate, calcium hydrogen carbonate, barium hydrogen carbonate, etc.), alkoxides (for example, alkali metal alkoxides such as potassium methoxide and sodium methoxide), alkali metal amides (potassium amide, sodium amide, etc.), amines or ammoniums (alkylamines such as triethylamine; tertiary arylamines such as N,N-dimethylaniline), heterocyclic amines such as pyridine, and quaternary ammonium hydroxides.

[0043] In a preferred embodiment, the basic catalyst may be preferably a carbonate or a bicarbonate, and more preferably at least one selected from the group consisting of alkali metal carbonates, alkaline earth metal carbonates, alkali metal bicarbonates, and alkaline earth metal carbonates. More specifically, the basic catalyst may be any of those listed above.

[0044] When a carbonate or bicarbonate is used as the alkali metal salt, the carbonate ion or bicarbonate ion disappears from the reaction system as carbon dioxide during the reaction, while the remaining alkali metal ion becomes the alkali metal salt of the target α,β-ethylenically unsaturated carboxylic acid and is thought to act as a catalyst, as will be described later.

[0045] In a preferred embodiment, the basic catalyst may be preferably an alkali metal carboxylic acid salt, more preferably at least one selected from the group consisting of alkali metal salts of α,β-ethylenically unsaturated carboxylic acids and alkali metal salts of aliphatic carboxylic acids, and even more preferably at least one selected from the group consisting of alkali metal salts of α,β-ethylenically unsaturated monocarboxylic acids and alkali metal salts of aliphatic monocarboxylic acids. Examples of alkali metal salts of α,β-ethylenically unsaturated carboxylic acids include alkali metal salts of (meth)acrylic acid. Examples of alkali metals include lithium, sodium, potassium, etc., and preferably sodium or potassium. More specifically, examples include potassium (meth)acrylate and sodium (meth)acrylate. Examples of alkali metal salts of aliphatic carboxylic acids include potassium acetate and sodium acetate.

[0046] When an alkali metal salt of an α,β-ethylenically unsaturated monocarboxylic acid is used as the alkali metal carboxylate, an α,β-ethylenically unsaturated monocarboxylic acid derived from the alkali metal salt of the α,β-ethylenically unsaturated monocarboxylic acid is produced. Therefore, if the structure of the α,β-ethylenically unsaturated monocarboxylic acid in the alkali metal salt of the α,β-ethylenically unsaturated monocarboxylic acid is the same as that of the (meth)acrylic acid compound obtained by the production method of the present invention, the amount of impurities that may be contained in the (meth)acrylic acid compound obtained by the production method of the present invention can be reduced.

[0047] When the alkali metal carboxylate is preferably an alkali metal salt of an aliphatic carboxylic acid, more preferably an alkali metal salt of an aliphatic monocarboxylic acid, an aliphatic (mono)carboxylic acid is produced as a by-product. The aliphatic (mono)carboxylic acid is easily removed by distillation, washing with water, or the like, and therefore the amount of impurities that may be contained in the (meth)acrylic acid compound obtained by the production method of the present invention can be significantly reduced.

[0048] Therefore, it is preferable to use, as the basic catalyst, at least one selected from the group consisting of alkali metal salts of α,β-ethylenically unsaturated monocarboxylic acids and alkali metal salts of aliphatic carboxylic acids, and more preferably at least one selected from the group consisting of alkali metal salts of (meth)acrylic acids and alkali metal salts of aliphatic carboxylic acids, because this makes it possible to greatly reduce the amount of impurities that may be contained in the (meth)acrylic acid compound obtained by the production method of the present invention.

[0049] In another preferred embodiment, the basic catalyst may be preferably a quaternary ammonium salt of a carboxylic acid, more preferably at least one selected from the group consisting of a quaternary ammonium salt of an α,β-ethylenically unsaturated carboxylic acid and a quaternary ammonium salt of an aliphatic carboxylic acid, and even more preferably at least one selected from the group consisting of a quaternary ammonium salt of an α,β-ethylenically unsaturated monocarboxylic acid and a quaternary ammonium salt of an aliphatic monocarboxylic acid. Examples of the quaternary ammonium salt of an α,β-ethylenically unsaturated carboxylic acid include alkali metal salts of (meth)acrylic acid. Examples of the ammonium ion of such a quaternary ammonium salt include N ＋ (-R ａ ) ４ [R ａ each independently represent a hydrocarbon group which may have a substituent (for example, an aromatic substituent such as a benzyl group), for example, an alkyl group having 1 to 12 carbon atoms which may have a substituent. Specific examples of quaternary ammonium carboxylates include tetraethylammonium (meth)acrylate, tetrabutylammonium (meth)acrylate, benzyltributylammonium (meth)acrylate, tetraethylammonium aliphatic carboxylate, tetrabutylammonium aliphatic carboxylate, and benzyltributylammonium aliphatic carboxylate.

[0050] In another preferred embodiment, the basic catalyst may be ammonium betaine, such as trimethylglycine, triethylglycine, tributylglycine, N-lauryl-N,N-dimethylglycine, N-(meth)acryloyloxyethyl-N,N-dimethylammonium-α-N-methylcarboxybetaine, or a vinyl copolymer containing N-(meth)acryloyloxyethyl-N,N-dimethylammonium-α-N-methylcarboxybetaine.

[0051] (Carboxylic Acid Anhydride) According to one embodiment of the production method of the present invention, the mixture containing a hydroxycarboxylic acid and / or its polymer and a basic catalyst further contains a carboxylic acid anhydride. Note that, when the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more, the carboxylic acid anhydride is not an essential component and may or may not be contained in the mixture.

[0052] Carboxylic acid anhydrides are compounds formed by dehydration condensation of two carboxylic acids and are represented by the general formula: R ｂ -CO-O-CO-R ｂ ' [R ｂ and R ｂ and each of the groups ' independently represents a monovalent organic group. In the production method of the present invention, the presence of a carboxylic acid anhydride and a basic catalyst is thought to promote a reaction that produces a (meth)acrylic acid compound using a hydroxycarboxylic acid and / or a polymer thereof as a raw material. The carboxylic acid anhydride is not particularly limited, and examples thereof include (meth)acrylic acid anhydride, acetic acid anhydride, propionic acid anhydride, oxalic acid anhydride, succinic acid anhydride, maleic acid anhydride, phthalic acid anhydride, and benzoic acid anhydride. One type of carboxylic acid anhydride may be used, or two or more types of carboxylic acid anhydrides may be used. Among these, from the viewpoints of ease of availability and efficient production of a (meth)acrylic acid compound, it is preferable to use (meth)acrylic acid anhydride, and it is more preferable to use (meth)acrylic acid anhydride having the structure described below.

[0053] In a preferred embodiment in which (meth)acrylic anhydride is used as the carboxylic acid anhydride, the (meth)acrylic anhydride is preferably a compound obtained by dehydration condensation of two compounds having a (meth)acrylic acid skeleton and a carboxylic acid skeleton. In this embodiment, the (meth)acrylic acid compound is represented by the formula (I): [In formula (I), R １ ~R ３ and each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In this specification, the (meth)acrylic anhydride represented by formula (I) is also referred to as "(meth)acrylic anhydride (I)." In a preferred embodiment of the production method of the present invention, when (meth)acrylic anhydride (I) and a basic catalyst are present, it is believed that the reaction of using a hydroxycarboxylic acid and / or a polymer thereof as a raw material to produce a (meth)acrylic acid compound is more likely to proceed.

[0054] R in formula (I) １ ~R ３ R each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. １ ~R ３ It is preferable that R in formula (I) has a structure corresponding to that of the acrylic acid compound to be produced, from the viewpoint of isolability of the obtained acrylic acid compound and reduction of impurities that may be contained in the compound. For example, when the 3-hydroxycarboxylic acid and / or its polymer used as a raw material is represented by the above formula (III), R in formula (I) １ and R ２ are R in formula (III), respectively. ４ and R ５ and R in formula (I) is preferably the same as ３ is R in formula (III) ６ It is preferable that R １ ~R ３ each independently preferably represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, more preferably represents a hydrogen atom or a methyl group, and further preferably represents a hydrogen atom.２ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R １ and R ３ represents a hydrogen atom. In this case, R ２ preferably represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

[0055] (Other Components) The mixture containing the hydroxycarboxylic acid and / or its polymer and the basic catalyst may contain one or more other components, such as additives such as a polymerization inhibitor, a solvent, etc.

[0056] The polymerization inhibitor is not particularly limited, and examples of phenolic compounds include hydroquinone, p-methoxyphenol, cresol, t-butylcatechol, 3,5-di-t-butyl-4-hydroxytoluene, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-butylphenol), and 4,4'-thiobis(3-methyl-6-t-butylphenol); examples of nitrogen-containing compounds include nitroxides such as piperidine-1-oxyl, pyrrolidine-1-oxyl, 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl, and 2,2,6,6-tetramethylpiperidine-1-oxyl; phenothiazine, 3,7-dioctylphenothiazine, and 3,7-dicumyl. Examples of phenothiazine derivatives such as phenothiazine and 3,7-di-t-butylphenothiazine, and transition metal salts include copper salts such as copper dialkyldithiocarbamate (wherein the alkyl groups are methyl, ethyl, propyl, or butyl and may be the same or different), copper acetate, copper salicylate, copper thiocyanate, copper nitrate, copper chloride, copper carbonate, copper hydroxide, and copper acrylate; manganese dialkyldithiocarbamate (wherein the alkyl groups are methyl, ethyl, propyl, or butyl and may be the same or different), manganese diphenyldithiocarbamate, manganese formate, manganese acetate, manganese octanoate, manganese naphthenate, manganese permanganate, and manganese salts of ethylenediaminetetraacetic acid. When a polymerization inhibitor is used, one type of polymerization inhibitor may be used, or two or more types may be used in combination. When the mixture contains a polymerization inhibitor, the polymerization of the (meth)acrylic acid compound generated in the reaction step can be inhibited, which is preferable because it can improve the production efficiency of the (meth)acrylic acid compound and also inhibit the polymerization of by-products that may be generated.The polymerization inhibitor is preferably a nitroxide such as piperidine-1-oxyl, pyrrolidine-1-oxyl, 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl, or 2,2,6,6-tetramethylpiperidine-1-oxyl, or a phenothiazine derivative such as phenothiazine, 3,7-dioctylphenothiazine, 3,7-dicumylphenothiazine, or 3,7-di-t-butylphenothiazine, more preferably 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl or 2,2,6,6-tetramethylpiperidine-1-oxyl. When the mixture contains a polymerization inhibitor, the content of the polymerization inhibitor is preferably 0.005 to 5 parts by mass, more preferably 0.01 to 2 parts by mass, and even more preferably 0.05 to 0.5 parts by mass, relative to 100 parts by mass of the 3-hydroxycarboxylic acid polymer. When the amount of the polymerization inhibitor is equal to or greater than the above lower limit, the polymerization inhibitory effect of the (meth)acrylic acid compound can be enhanced.

[0057] The mixture used in the production method of the present invention may or may not contain a solvent. The solvent that can be contained in the mixture is preferably an aprotic organic solvent, as it is less likely to inhibit the production of the (meth)acrylic acid compound. Examples of such aprotic organic solvents include ethyl acetate, tetrahydrofuran, toluene, methyl ethyl ketone, and cyclopentanone. The content of the solvent in the mixture is not particularly limited and may be, for example, 0 to 80% by mass based on the total amount of the mixture.

[0058] In a preferred embodiment of the present invention, from the viewpoint of isolating the produced (meth)acrylic acid compound, the content of the solvent contained in the mixture, particularly the solvent having a boiling point lower than the boiling point of the produced (meth)acrylic acid compound, is preferably 0 to 50 mass %, more preferably 0 to 30 mass %, even more preferably 0 to 20 mass %, still more preferably 0 to 10 mass %, and particularly preferably 0 to 5 mass %, based on the total amount of the mixture.

[0059] In the mixture containing a hydroxycarboxylic acid and / or a polymer thereof and a basic catalyst, or in the mixture containing a hydroxycarboxylic acid and / or a polymer thereof, a basic catalyst, and a carboxylic acid anhydride to be reacted in the production method of the present invention, the amount of the basic catalyst relative to 100 parts by mass of the hydroxycarboxylic acid and its polymer in total is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass, from the viewpoint of improving the yield of the (meth)acrylic acid compound.

[0060] In addition, in a mixture containing a hydroxycarboxylic acid and / or a polymer thereof, a basic catalyst, and a carboxylic acid anhydride, the amount of the carboxylic acid anhydride represented by formula (I) relative to 100 parts by mass of the hydroxycarboxylic acid and its polymer in total is preferably 0.1 to 50 parts by mass, more preferably 1 to 30 parts by mass, and even more preferably 5 to 20 parts by mass, from the viewpoint of improving the yield of the (meth)acrylic acid compound.

[0061] In the mixture, the amount of the carboxylic acid anhydride represented by formula (I) relative to the total amount of the hydroxycarboxylic acid and its polymer is preferably 0.05 to 25 mol %, more preferably 0.5 to 15 mol %, and even more preferably 2.5 to 10 mol %, from the viewpoint of improving the yield of the (meth)acrylic acid compound.

[0062] (Method for Producing (Meth)acrylic Acid Compounds) The production method of the present invention includes at least a reaction step of heating a mixture containing a hydroxycarboxylic acid and / or its polymer with a basic catalyst to react and produce a (meth)acrylic acid compound, wherein (1) the mixture further contains a carboxylic acid anhydride, and / or (2) the weight-average molecular weight of the polymer of the hydroxycarboxylic acid contained in the raw material is 10,000 or more. The (meth)acrylic acid compound produced by the production method of the present invention is not particularly limited as long as it is a compound having a (meth)acrylic acid skeleton, and may be acrylic acid, methacrylic acid, compounds in which at least one hydrogen atom of these is substituted with an alkyl group having 1 to 3 carbon atoms, or derivatives thereof (e.g., salts and esters). The (meth)acrylic acid compound produced by the production method of the present invention usually has a structure corresponding to the polymer of the hydroxycarboxylic acid used as the raw material. For example, when the hydroxycarboxylic acid and its polymer are represented by the formula (III)-1: [In formula (III)-1, R ４ ~R ６ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n represents an integer of 1 or more. Or, a compound represented by formula (III)-2: [In formula (III)-2, R １０ , R １１ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n represents an integer of 1 or more. In this case, the (meth)acrylic acid compound obtained by the production method of the present invention is represented by formula (IV): [In formula (IV), R ７ ~R ９ and each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ７ and R ９ are R in formula (III)-1, respectively. ４ and R ５ corresponds to R ９ is R ６ It is considered that R in formula (IV) corresponds to ９ is R in formula (III)-2 １０ corresponds to R ７ and R８ is R １１ The (meth)acrylic acid compound obtained by the production method of the present invention may be one type of (meth)acrylic acid compound or a mixture of two or more types of (meth)acrylic acid compounds.

[0063] The production method of the present invention is not limited in any way to the reaction mechanism as long as it includes the above-mentioned reaction steps, but it is believed that the reaction steps proceed, for example, according to the following reaction mechanism. (1) The case where the mixture further contains a carboxylic acid anhydride and / or (2) The case where the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more will be described. First, the case where (1) the mixture further contains a carboxylic acid anhydride will be described.

[0064] In the following reaction mechanism, an example will be described in which the hydroxycarboxylic acid is 3-hydroxypropionic acid, which is a type of 3-hydroxycarboxylic acid, the basic catalyst is sodium acrylate, and the carboxylic acid anhydride is acrylic anhydride, but this does not mean that the components are limited to these, and the mechanism also applies to other 3-hydroxycarboxylic acids and / or polymers thereof, other basic catalysts, and other carboxylic acid anhydrides. Furthermore, the production method of the present invention is in no way limited to the following reaction mechanism.

[0065]

[0066] In the above reaction scheme, AN a is sodium acrylate, (3HP) ｎ is 3-hydroxypropionic acid or its polymer, AA is acrylic anhydride, and AC is acrylic acid. First, as shown in (1), the negative charge A － (3HP) ｎ It acts on the proton of the terminal hydroxyl group of (3HP) ｎ The negative charge generated on the oxygen atom of AA attacks the carbonyl carbon of AA, forming AC1, ANa, and A-(3HP) shown in (2). ｎ In (1), (3HP) ｎThe chemical formula is 3HP-(3HP) ｎ－１ Then, as shown in (2), A-(3HP) ｎ Furthermore, the negative charge A of AN a － acts to combine AC2, ANa, and A-(3HP) shown in (3). ｎ－１ Although not shown in the above reaction scheme, A-(3HP) ｎ－１ Furthermore, the negative charge A of AN a － acts to combine AC3, AN a and A-(3HP) ｎ－２ This reaction continues to produce (3HP) ｎ It is thought that n decreases by one, and acrylic acid is produced sequentially. In the above reaction scheme (1), (3HP) ｎ One of the hydroxyl groups reacts with AA, but (3HP) ｎ The hydroxyl groups at both ends of the molecule react with AA to form A-(3HP). ｎ It is believed that the reaction will proceed in the same manner even when the cation is -A. Furthermore, it is believed that the synergistic effect of the presence of AA and AN a in the above reaction scheme allows the above reaction to proceed under milder conditions than when the reaction is carried out using only AN a.

[0067] In the above reaction, A-(3HP) shown in (3) ｎ－１ further reacts with AC2 or AN a to form A-(3HP) ｎ It is believed that a reverse reaction returning to the above may also occur. For example, it is believed that such a reverse reaction can be suppressed by removing the produced AC2 from the reaction system.

[0068] The basic compound (e.g., AN a) reacted in (1) may be used in a catalytic amount, and AN a reacted in (2) and (3), etc., is sequentially generated in the system. Therefore, the basic compound used in the production method of the present invention is (3HP). ｎIt is understood that the (meth)acrylic anhydride may be, for example, a compound represented by formula (I), and that the structure thereof is not particularly limited, but that by using a (meth)acrylic anhydride corresponding to the polymer of 3-hydroxycarboxylic acid used, the resulting acrylic acid compound can be a single compound, and impurities can be further reduced.

[0069] Next, an example will be described in which the hydroxycarboxylic acid is 2-hydroxyisobutyric acid, which is a type of 2-hydroxycarboxylic acid, the basic catalyst is sodium methacrylate, and the carboxylic acid anhydride is methacrylic anhydride. As with the above, this does not mean that the components are limited to these, and the mechanism applies similarly to other 2-hydroxycarboxylic acids and / or their polymers, other basic catalysts, and other carboxylic acid anhydrides.

[0070]

[0071] In the above reaction scheme, MANa is sodium methacrylate and (2HIB) ｎ is 2-hydroxyisobutyric acid or its polymer, MAMA is methacrylic anhydride, and MAC is methacrylic acid. First, as shown in (4), the negative charge MA － (2HIB) ｎ It acts on the proton of the terminal hydroxyl group of (2HIB) ｎ The negative charge generated on the oxygen atom of (2HIB) attacks the carbonyl carbon of MAMA, forming MAC1, MANa, and MA-(2HIB) shown in (5). ｎ In (4), (2HIB) ｎ The chemical formula is 2HIB-(2HIB) ｎ－１ Then, as shown in (5), MA-(2HIB) ｎ Furthermore, the negative charge MA － acts to produce MAC2, MANa, and MA-(2HIB) shown in (6). ｎ－１Then, although not shown in the above reaction scheme, MA-(2HIB) ｎ－１ Furthermore, the negative charge MA － acts to combine MAC3, MANa, and MA-(2HIB) ｎ－２ This reaction continues to produce (2HIB) ｎ It is thought that n decreases by one, and methacrylic acid is produced sequentially. In the above reaction scheme (4), (2HIB) ｎ One of the hydroxyl groups reacts with MAMA, (2HIB) ｎ The hydroxyl groups at both ends of the chain react with MAMA to form MA-(2HIB). ｎ It is believed that the reaction will proceed in the same manner even when the hydroxyl group is -MA. Furthermore, it is believed that the synergistic effect of the presence of MAMA and MANa in the above reaction scheme allows the above reaction to proceed under milder conditions than when the reaction is carried out using only MANa.

[0072] Here, it has been found that when the weight-average molecular weight of the polymer of hydroxycarboxylic acid contained in the raw material is 10,000 or more, a (meth)acrylic acid compound can be obtained even in the absence of carboxylic acid anhydride. The reason for this is not clear, but it is thought that the reaction proceeds, for example, according to the following mechanism. Note that the following reaction mechanism will be explained using specific compounds as examples, but this does not mean that the components are limited to these. Furthermore, the production method of the present invention is not limited in any way to the following reaction mechanism.

[0073]

[0074] When a polymer of 3-hydroxycarboxylic acid having a weight-average molecular weight of 10,000 or more, represented by formula (1), reacts with a basic catalyst (sodium carbonate in the reaction scheme), it is believed that compounds represented by formulas (2) and (3) are produced. On the other hand, if acrylic anhydride is not used, the polymers of formulas (2') and (4) ultimately remain as major or minor components. For this reason, for example, when comparing a polymer of 3-hydroxycarboxylic acid having a weight-average molecular weight of 1,000 with a polymer of 3-hydroxycarboxylic acid having a weight-average molecular weight of 10,000, the number of molecules (moles) of the latter is 1 / 10 of the number of molecules of the former, given the same weight. Therefore, in a polymer of 3-hydroxycarboxylic acid having a weight-average molecular weight of 10,000, the residues as major and minor components are 1 / 10 of those of a polymer of 3-hydroxycarboxylic acid having a weight-average molecular weight of 1,000, which is believed to increase the yield of acrylic acid. That is, the lower the molecular weight, the more residues there are as major and minor components, and the lower the yield of acrylic acid. At this time, if there is a lot of water, the polymer represented by formula (1) is hydrolyzed, the weight average molecular weight decreases, and the molecular weight decreases, so that the residues as major and minor components increase and the yield decreases.

[0075] In the production method of the present invention, the water content in the mixture containing a hydroxycarboxylic acid and / or its polymer and a basic catalyst is preferably low. For example, the water content is preferably 0 to 15% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, based on the total amount of the mixture. When the water content is equal to or less than the above-mentioned upper limit, the amount of water contained in the resulting (meth)acrylic acid compound product can be reduced, improving the handleability of the product. The amount of water contained in the (meth)acrylic acid compound product is preferably 0.1% by mass or less, based on the total amount of (meth)acrylic acid compound. Furthermore, when the weight-average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more, it is believed that when the amount of water is equal to or less than the above-mentioned upper limit, residues as major and minor components in the reaction scheme can be further reduced.

[0076] The production method of the present invention includes at least a reaction step of heating a mixture containing at least a hydroxycarboxylic acid and / or a polymer thereof and a basic catalyst to react with each other and produce a (meth)acrylic acid compound.

[0077] The reaction step may be carried out, for example, by heating the mixture placed in a reaction vessel. The reaction step may be carried out batchwise or continuously. Since the (meth)acrylic acid produced in the reaction step is prone to polymerization, it is preferable to carry out a step of distilling off the (meth)acrylic acid compound produced in the reaction step from the viewpoint of preventing such polymerization and improving the yield of the reaction product. For example, it is more preferable to carry out the reaction step and the distillation step of the produced (meth)acrylic acid simultaneously. Examples of the reaction apparatus include a reactor equipped with a stirrer and a reaction apparatus configured to be capable of both heating the mixture and distilling off the produced (meth)acrylic acid (for example, an apparatus equipped with a thin film distiller or a Kugelrohr).

[0078] The heating conditions are not particularly limited as long as the hydroxycarboxylic acid and / or its polymer and the basic catalyst, preferably together with the carboxylic acid anhydride, react to produce a (meth)acrylic acid compound; from the viewpoint of reaction efficiency, the heating temperature is preferably 50°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, and even more preferably 90°C or higher. Furthermore, from the viewpoint of easily suppressing unwanted side reactions, the heating temperature may be preferably less than 300°C, more preferably 250°C or lower, even more preferably 220°C or lower, even more preferably 200°C or lower, particularly preferably 180°C or lower, especially preferably 160°C or lower, and extremely preferably 140°C or lower. In conventional production methods for producing a (meth)acrylic acid compound from a hydroxycarboxylic acid polymer, the heating temperature was as high as more than 300°C. However, the production method of the present invention makes it possible to produce a (meth)acrylic acid compound under milder conditions. The heating temperature in the reaction step may preferably be in the range of 50 to 300°C, 70 to 250°C, 80 to 220°C, 80 to 200°C, 80 to 180°C, 90 to 160°C, 90 to 140°C, etc. In a preferred embodiment of the present invention, from the viewpoint of carrying out the reaction under milder conditions compared to conventional techniques, the heating temperature in the reaction step is preferably 80 to 220°C, more preferably 80 to 200°C, even more preferably 80 to 180°C, still more preferably 90 to 160°C, and particularly preferably 90 to 140°C.

[0079] The heating time is not particularly limited and may be adjusted appropriately depending on the progress of the reaction, etc. Furthermore, when the reaction step is carried out in a continuous manner, the reaction step can be carried out continuously by adding the raw material hydroxycarboxylic acid and / or its polymer to the reaction system while heating and removing the produced (meth)acrylic acid compound from the reaction system. When a carboxylic acid anhydride is used, it is preferable to add the carboxylic acid anhydride, which is thought to be consumed by the reaction, to the reaction system together. In this case, the heating time is also not particularly limited.

[0080] In a preferred embodiment of the present invention, the production method of the present invention further comprises a step of distilling off the (meth)acrylic acid compound produced in the reaction step. By distilling off the produced (meth)acrylic acid compound from the reaction system, it becomes possible to shift the reaction equilibrium toward the production of the (meth)acrylic acid compound, thereby improving the yield of the (meth)acrylic acid compound. In other words, the step of distilling off the (meth)acrylic acid compound is preferably carried out simultaneously with the reaction step.

[0081] Methods for distilling off the (meth)acrylic acid compound include distillation, particularly vacuum distillation. The pressure in the system (degree of vacuum) during vacuum distillation is preferably lower than the vapor pressure of the resulting (meth)acrylic acid compound. Therefore, the upper limit of the degree of vacuum is preferably 101 kPa or less, more preferably 67 kPa or less, and even more preferably 40 kPa or less. In addition, from the viewpoint of making it difficult for high-boiling point components such as polymers (particularly dimers) of (meth)acrylic acid compounds to be included in the distillate, the lower limit of the degree of vacuum is preferably 1.3 kPa or more, preferably 6.7 kPa or more, more preferably 11 kPa or more, and even more preferably 16 kPa or more.

[0082] According to a preferred embodiment of the present invention, a (meth)acrylic acid compound having few impurities can be produced by the production method of the present invention. For example, the (meth)acrylic acid compound produced by the production method of the present invention has a low content of by-products such as water and propionic acid.

[0083] According to the production method of the present invention, a novel method for producing a (meth)acrylic acid compound can be provided. In a preferred embodiment of the present invention, the (meth)acrylic acid compound produced by the production method of the present invention has few impurities and can be used as a useful raw material in the production of resins such as poly(meth)acrylic acid.

[0084] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Furthermore, unless otherwise specified, "%" and "parts" in the following description mean "% by mass" and "parts by mass", respectively.

[0085] [HPLC] The HPLC measurement conditions were as follows: column: YMC-pack ODS-AM-302 150 mm × φ4.6 mm S-5 μm 120 A, temperature: 40°C, flow rate: 1 mL / min, detection wavelength: 210 nm, mobile phase: acetonitrile / 0.5 wt % phosphoric acid aqueous solution (ratio 1 / 1), analysis time: 25 min.

[0086] [ １ H-NMR] １ The H-NMR measurement conditions were 500 MHz, 25° C., solvent: deuterated chloroform, internal standard: tetramethylsilane.

[0087] [GC] The GC measurement conditions were as follows: column: capillary column 007-1701, length 25 m, inner diameter 0.32 mm, liquid phase film thickness 1 μm (manufactured by Quadex); column temperature: 50° C. (3 minutes) → temperature increase 10° C. / min → 100° C. (0 minutes) → temperature increase 15° C. / min → 250° C. (15 minutes); injection temperature: 220° C.; detector (FID) temperature: 220° C.; carrier gas: He; flow rate: 2.23 mL / min (inlet pressure 85.0 kPa); split ratio: 50.0; analysis time: 25 minutes.

[0088] [GPC] The GPC measurement conditions were as follows: column: TSK-gel SuperAWH-H (4 columns) (manufactured by Tosoh Corporation), mobile phase: N,N-dimethylformamide (0.03 M lithium bromide solution), thermostatic bath: 40°C, flow rate: 0.6 mL / min, analysis time: 30 min. Mw is a value converted to standard polystyrene.

[0089] [Production Example 1: Synthesis of Raw Material (A) Containing 3-Hydroxypropionic Acid and Its Polymer] To 10 g (33.3 mmol) of a 30% by mass aqueous solution of 3-hydroxypropionic acid (hereinafter, 3-HPA) (manufactured by Tokyo Chemical Industry Co., Ltd.), 6.38 g (33.3 mmol) of EDC·HCl (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride) (manufactured by Tokyo Chemical Industry Co., Ltd.) was added in four portions at 30°C or below under water cooling, and the mixture was then stirred at 40°C for 4 hours. After confirming the disappearance of 3-HPA by HPLC, an extraction procedure in which a four-fold amount of ethyl acetate was added to the reaction solution was carried out four times to obtain an extract. The extract was concentrated under reduced pressure using an evaporator in a water bath at 55°C to obtain 1.85 g of Raw Material (A) containing 3-HPA and / or a polymer thereof as a colorless, transparent oil. As a result of analyzing the raw material (A) by HPLC, it was found that the 3-HPA polymer contained dimers to decamers (n = 2 to 10), and the proportion of the 3-HPA polymers (n = 2 to 10) in the raw material (A) was 94 mass %, and the proportion of 3-HPA was 6 mass %. The results of the HPLC analysis are shown in Figure 1. １ The average molecular weight of raw material (A) was calculated from the proton ratio of H-NMR, and it was found to be a trimer. Since the molecular weight of the 3-HPA polymer closest to this average value is 234 (trimer), hereinafter raw material (A) will also be described as a trimer with a weight-average molecular weight (Mw) of 234.

[0090] Production Example 2: Synthesis of raw material (B) containing 3-HPA and its polymers 2.32 g of raw material (B) containing 3-HPA and its polymers was obtained as a colorless, transparent oil in the same manner as in Production Example 1, except that 5 g (21.3 mmol) of raw material (A) obtained in Production Example 1 and 1.00 g of distilled water were used instead of 10 g of a 30% by mass aqueous solution of 3-hydroxypropionic acid, and the amount of EDC·HCl was changed to 5.32 g (27.8 mmol). HPLC analysis of raw material (B) revealed that raw material (B) contained 95% by mass of 3-HPA polymers, and that the 3-HPA polymers included tetramers to 15mers (n = 4 to 15). The proportions of each polymer in the 3-HPA polymer (n = 4 to 15) were as follows: tetramer: 30% 29%, hexamer: 25% 24% by mass, total of octamer and nonamer: 33% 31% by mass, total of decamers and higher: 4% 16% by mass. Furthermore, the average molecular weight of raw material (B) was calculated from the HPLC area ratio in the same manner as for raw material (A), and the result was a hexamer. Raw material (B) is therefore a heptamer with a weight-average molecular weight of 522.

[0091] [Production Example 3: Synthesis of Raw Material (C) Containing a 3-HPA Polymer] 1.20 g (16.65 mmol) of β-propiolactone (Tokyo Chemical Industry Co., Ltd.) and 0.0019 g (0.016 mmol) of N,N,N-trimethylglycine carboxylate (Tokyo Chemical Industry Co., Ltd.) were dissolved in 11.8 g of tetrahydrofuran (hereinafter, THF) and stirred at 50°C for 8 hours. The mixture was then cooled to room temperature and allowed to stand for one week. The precipitated solid was filtered and dried to obtain 0.52 g of Raw Material (C) containing a p-3HP polymer. The weight average molecular weight (Mw) of Raw Material (C) was measured by gel permeation chromatography (GPC), and Mw was 20,700. From these results, Raw Material (C) was determined to be a 287-mer.

[0092] [Production Example 4: Synthesis of Raw Material (D) Containing a 3-HPA Polymer] 5.00 g (63.39 mmol) of β-propiolactone and 0.0081 g (0.0694 mmol) of N,N,N-trimethylglycine carboxylate were dissolved in 50 g of THF and allowed to stand at room temperature for two months. The precipitated solid was then filtered and dried to obtain 1.76 g of Raw Material (D) containing a p-3HP polymer. The Mw of Raw Material (D) was measured in the same manner as in Production Example 3, and was found to be 74,600. From these results, Raw Material (D) is determined to be a 1,035-mer.

[0093] [Production Example 5: Synthesis of Raw Material (E) Containing 3-HPA Polymer] 20.00 g (277.55 mmol) of β-propiolactone and 0.0406 g (0.3469 mmol) of N,N,N-trimethylglycine carboxylate were dissolved in 300 g of THF and stirred at 50°C for 50 hours. The mixture was then cooled to room temperature and allowed to stand for two months. The precipitated solid was filtered and dried to obtain 0.52 g of Raw Material (E) containing a p-3HP polymer. The Mw of Raw Material (E) was measured in the same manner as in Production Example 3, and was found to be 139,700. From these results, Raw Material (E) was determined to be a 2,133-mer.

[0094] [Production Example 6: Synthesis of Raw Material (F) Containing 3-HPA Polymer] 25.00 g (364.94 mmol) of β-propiolactone and 0.0406 g (0.3469 mmol) of N,N,N-trimethylglycine carboxylate were dissolved in 200 g of THF and allowed to stand at room temperature for two months. The precipitated solid was filtered and dried, yielding 9.55 g of Raw Material (F) containing a p-3HP polymer. The obtained Raw Material (F) was insoluble in THF and dimethylformamide, and therefore, the Mw could not be measured by GPC using these as the mobile phase. Therefore, the filtrate obtained when filtering Raw Material (F) was measured by GPC under the same conditions as above, and the Mw was found to be 643,000. Therefore, the Mw of the obtained solid p-3HP is considered to be at least 643,000. Furthermore, from these results, Raw Material (F) is determined to be at least an 8,922-mer.

[0095] Reference Example 1: Measurement of thermal decomposition temperature of each raw material For each of the above raw materials, the thermal decomposition temperature at which there was a 5% weight loss was measured using a simultaneous thermogravimetry and differential thermal analysis (TG-DTA) device. The thermal decomposition temperature at which there was a 5% weight loss is considered to be the temperature at which 5% of the 3-HPA contained in each raw material is converted to acrylic acid. The measurement conditions and results are as follows. <Measurement conditions> Measurement device: Heating conditions: 50°C to 100°C; 10°C / min, 100°C; 5 min, 100°C to 400°C; 10°C / min <Measurement results> Raw material (A): 165°C Raw material (B): 175°C Raw material (C): 232°C Raw material (D): 237°C Raw material (E): 243°C Raw material (F): 266°C

[0096] The above measurement results show that, in the absence of a basic catalyst and a carboxylic acid anhydride, high temperature and long time conditions are required to produce acrylic acid from the raw materials (A) to (F) containing a 3-HPA polymer.

[0097] Example 1 240 mg of raw material (A) containing 3-HPA and its polymer obtained in Production Example 1, 5.7 mg of potassium acrylate (manufactured by Nippon Shokubai Co., Ltd.), 50.3 mg of acrylic anhydride (manufactured by Osaka Organic Chemical Industry Ltd.), and 0.3 mg of a polymerization inhibitor (commercially available 4-hydroxy-TEMPO) were placed in a 10 mL pressure-resistant vessel and heated at 100°C for 1 hour with stirring to obtain 296 mg of reaction product (1). The obtained reaction product (1) was analyzed by HPLC, and the amounts of (a) acrylic acid, (b) A-3-HPA polymer, (c) 3-HPA polymer, and (d) 3-HPA, represented by the following chemical formulas, contained in reaction product (1) were quantified. However, for (b), acrylic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as a standard sample. The quantitative results are shown in Table 1, and the HPLC chart is shown in Figure 2.

[0098] In the HPLC analysis of the product of Example 1, the reaction product (1) was completely dissolved in the mobile phase, and no insoluble matter was found. The obtained acrylic acid contained not only that derived from the raw material (A) but also that derived from potassium acrylate and acrylic anhydride, so the yield in this example was calculated as follows: Yield (%) = (weight of acrylic acid contained in the reaction product) / ((weight of raw material (A) + weight of potassium acrylate + weight of acrylic anhydride)).

[0099] 1 and 2, when the distribution of polymerization degrees of the A-3-HPA polymer contained in the reaction product (1) is compared with the distribution of polymerization degrees of the 3-HPA polymer in the raw material (A), the content of polymers with low polymerization degrees is increased in the reaction product (1) compared with the raw material (A). This indicates that a reaction as shown in reaction scheme (2) occurred, in which the ester bond of the 3-HPA polymer is cleaved to produce acrylic acid.

[0100] Example 2 A reaction product (2) according to Example 2 was produced in the same manner as in Example 1, except that heating was carried out at 100° C. for 1 hour and then at 150° C. for 1 hour. The results are shown in Table 1.

[0101] Example 3 1,000 mg of the raw material (A) obtained in Production Example 1, 24 mg of potassium acrylate (pKa of acrylic acid: 4.26), 200 mg of acrylic anhydride, and 1 mg of a polymerization inhibitor (4-hydroxy-TEMPO) were placed in a Kugelrohr sample ball, and while rotating, the pressure was reduced to 25 KPa to 18 KPa, the jacket temperature was set to 125°C, and the mixture was heated to 125°C. Next, the temperature was increased from that temperature to 194°C in 2 hours, and a transparent distillate was obtained. This distillate was analyzed by HPLC and １ Analysis by H-NMR revealed that the distillate contained 620 mg of acrylic acid (GC content 96.6%). １ The H-NMR charts are shown in Figures 3 and 4, respectively. In the HPLC chart, no peaks other than those shown in Figure 3 were detected. 350 mg of reaction product (3) was produced in the sample ball. １The results of the analysis are shown in Table 1, and the HPLC and １ The H-NMR charts are shown in Figures 5 and 6, respectively. In the HPLC chart, no peaks other than those shown in Figure 5 were detected. The yield was calculated as follows: Yield (%) = (weight of acrylic acid contained in the reaction product + weight of acrylic acid in the distillate) / (weight of raw material (B) + weight of potassium acrylate + weight of acrylic anhydride).

[0102] Example 4 A distillate and a reaction product (4) were obtained in the same manner as in Example 3, except that the pressure was changed from 20 KPa to 18 KPa and other conditions and compositions were changed as shown in Table 1. Analysis of these products was carried out. The analysis results are shown in Table 1.

[0103] Comparative Examples 1 to 3 Production of acrylic acid and analysis of comparative reaction products (1) to (3) were carried out in the same manner as in Example 1, except that the conditions were changed as shown in Table 1. The results are shown in Table 1.

[0104]

[0105] Table 1 confirms that the production method of the present invention described in Examples 1 to 4 allows the reaction to proceed even at relatively low temperatures, resulting in the production of acrylic acid. In each example, heating was terminated before the reaction was completely completed in order to observe the progress of the reaction, and 3-HPA polymer remained in the reaction product. Therefore, the reaction yield can be further improved by, for example, extending the reaction time. In contrast, in Comparative Examples 1 to 3, the target product, acrylic acid, was hardly obtained.

[0106] In the following examples and comparative examples, the weight loss rate when the reaction was carried out under the following conditions was measured by a TG-DTA apparatus and was considered to correspond to the yield.

[0107] Example 5 100 parts by mass of raw material (B) containing 3-HPA and its polymer obtained in Production Example 2, 2 parts by mass of potassium acrylate (manufactured by Nippon Shokubai Co., Ltd.), and 22 parts by mass of acrylic anhydride (manufactured by Osaka Organic Chemical Industry Ltd.) were placed in an aluminum container (10 mg), heated from 50°C to 100°C over 5 minutes, maintained at 100°C for 5 minutes, heated to 150°C over 5 minutes, and then heated at 150°C for 55 minutes (heating condition 1). The heating time from 50 to 150°C was 70 minutes in total. Based on the weight loss rate, the yield corresponded to 66.1%.

[0108] Example 6-1 A reaction was carried out in the same manner as in Example 5, except that raw material (B) was replaced with raw material (C) (Mw: 20,700) containing 3-HPA and a polymer thereof obtained in Production Example 3, and acrylic anhydride was not used. Based on the weight loss rate, the yield was 22.4%.

[0109] Example 6-2 The reaction was carried out in the same manner as in Example 6-1, except that 5 parts by mass of acrylic anhydride was further used. Based on the weight loss rate, the yield was 56.0%.

[0110] Example 6-3 A reaction was carried out in the same manner as in Example 6-2, except that the amount of acrylic anhydride was changed to 10 parts by mass. Based on the weight loss rate, the yield was 85.5%.

[0111] Example 6-4 A reaction was carried out in the same manner as in Example 6-2, except that the amount of acrylic anhydride was changed to 25 parts by mass. Based on the weight loss rate, the yield was 95.5%.

[0112] Example 6-5 A reaction was carried out in the same manner as in Example 6-1, except that sodium 3-hydroxypropionate (manufactured by Cosmo Bio Co., Ltd.) was used instead of potassium acrylate. Based on the weight loss rate, the yield was equivalent to 10.2%.

[0113] Example 6-6 A reaction was carried out in the same manner as in Example 6-1, except that 2 parts by mass of potassium acrylate and 2 parts by mass of sodium 3-hydroxypropionate (manufactured by Cosmo Bio Co., Ltd.) were used. Based on the weight loss rate, the yield was 35.0%.

[0114] Example 6-7 A reaction was carried out in the same manner as in Example 6-6, except that 9 parts by mass of acrylic anhydride was further used. Based on the weight loss rate, the yield was 54.0%.

[0115] Example 6-8 A reaction was carried out in the same manner as in Example 6-1, except that the amount of potassium acrylate was changed to 6 parts by mass. Based on the weight loss rate, the yield was 65.7%.

[0116] Example 6-9 A reaction was carried out in the same manner as in Example 6-1, except that 5 parts by mass of potassium carbonate (K carbonate) was used instead of potassium acrylate. Based on the weight loss rate, the yield was 65.0%.

[0117] Comparative Example 5 A reaction was carried out in the same manner as in Example 5, except that only 100 parts by mass of the raw material (B) containing 3-HPA and its polymer obtained in Production Example 2 was used. Based on the weight loss rate, the yield was equivalent to 0.6%.

[0118] Comparative Example 6 A reaction was carried out in the same manner as in Comparative Example 5, except that instead of the raw material (B), only the raw material (C) containing 3-HPA and its polymer obtained in Production Example 3 was used. Based on the weight loss rate, the yield was equivalent to 0.6%.

[0119] Example 7-1 A reaction was carried out in the same manner as in Example 5, except that raw material (D) (Mw: 74,600) containing 3-HPA and a polymer thereof obtained in Production Example 4 was used instead of raw material (B), the amount of potassium acrylate was changed to 5 parts by mass, and acrylic anhydride was not used. Based on the weight loss rate, the yield corresponded to 41.0%.

[0120] Example 7-2a The reaction was carried out in the same manner as in Example 7-1, except that 10 parts by mass of acrylic anhydride was further used. Based on the weight loss rate, the yield was 87.8%.

[0121] Example 7-2b A reaction product 7-2b was obtained in the same manner as in Example 7-2a, except that instead of heating condition 1, the mixture placed in a pressure-resistant vessel was heated with stirring, heated from 50°C to 100°C over 5 minutes, then maintained at 100°C for 5 minutes, heated to 150°C over 5 minutes, and heated at 150°C for 85 minutes (heating condition 2). The heating time from 50 to 150°C under heating condition 2 was 85 minutes in total. Based on the weight loss, the yield was 97.2%.

[0122] Example 7-2c Reaction product 7-2c was obtained in the same manner as in Example 7-2a, except that instead of heating condition 1, the mixture placed in a pressure-resistant vessel was heated with stirring, heated from 50°C to 100°C over 5 minutes, then maintained at 100°C for 5 minutes, heated to 150°C over 5 minutes, and heated at 150°C for 135 minutes (heating condition 3). The heating time from 50 to 150°C under heating condition 3 was 150 minutes in total. Based on the weight loss, the yield was 98.3%.

[0123] Examples 7-3a to 7-3c Analyses were performed in the same manner as in Examples 7-2a to 7-2c, except that 5 parts by mass of potassium carbonate was used instead of potassium acrylate and acrylic anhydride was not used. Based on the weight loss rates, the yields of 7-3a, 7-3b, and 7-3a were 55.7%, 71.4%, and 80.9%, respectively.

[0124] Example 8-1 A reaction was carried out in the same manner as in Example 5, except that raw material (E) (Mw: 139,700) containing 3-HPA and a polymer thereof obtained in Production Example 5 was used instead of raw material (B), the amount of potassium acrylate was changed to 5 parts by mass, and acrylic anhydride was not used. Based on the weight loss rate, the yield corresponded to 48.3%.

[0125] Example 8-2a The reaction was carried out in the same manner as in Example 8-1, except that 10 parts by mass of acrylic anhydride was further used. Based on the weight loss rate, the yield was 91.0%.

[0126] Example 8-2b A reaction was carried out in the same manner as in Example 8-2a, except that heating was carried out under heating condition 2 instead of heating condition 1. The weight loss rate corresponds to a yield of 97.2%.

[0127] Example 8-2c A reaction was carried out in the same manner as in Example 8-2a, except that heating was carried out under heating condition 3 instead of heating condition 1. The weight loss rate corresponds to a yield of 97.2%.

[0128] Examples 8-3a to 8-3b Reactions were carried out in the same manner as in Examples 8-2a to 8-2c, except that 5 parts by mass of potassium carbonate was used instead of potassium acrylate and acrylic anhydride was not used. Based on the weight loss rates, the yields of 8-3a, 8-3b, and 8-3c were 59.9%, 89.3%, and 97.7%, respectively.

[0129] Example 9-1 A reaction was carried out in the same manner as in Example 5, except that raw material (F) (Mw: at least 643,000) containing 3-HPA and a polymer thereof obtained in Production Example 5 was used instead of raw material (B), the amount of potassium acrylate was changed to 5 parts by mass, and acrylic anhydride was not used. Based on the weight loss rate, the yield was equivalent to 34.7%.

[0130] Examples 9-2a to 9-2c The reaction was carried out in the same manner as in Example 9-1, except that 11 parts by mass of acrylic anhydride were further used. Based on the weight loss rate, the yield of acrylic acid in 9-2a was equivalent to 50.2%. The reaction was also carried out in the same manner as above, except that heating condition 1 was changed to heating condition 2. Based on the weight loss rate, the yield of acrylic acid in 9-2b was equivalent to 77.3%. The analysis was also carried out in the same manner as above, except that heating condition 1 was changed to heating condition 3. Based on the weight loss rate, the yield of acrylic acid in 9-2c was equivalent to 98.2%.

[0131] Examples 9-3a to 9-3c Reactions were carried out in the same manner as in Examples 9-2a to 9-2c, except that the amount of acrylic anhydride was changed to 10 parts by mass and zinc(II) acrylate was used instead of potassium acrylate. Based on the weight loss rates, the yields of 9-3a, 9-3b, and 9-3c were 46.0%, 77.4%, and 95.1%, respectively.

[0132] Examples 9-4a to 9-4c Reactions were carried out in the same manner as in Example 9-1, except that potassium carbonate was used instead of potassium acrylate, under heating conditions 1 to 3. Based on the weight loss rates, the yields of 9-4a, 9-4b, and 9-4c corresponded to 67.2%, 92.4%, and 96.6%, respectively.

[0133] Examples 9-5a to 9-5c Reactions were carried out in the same manner as in Example 9-1, except that sodium carbonate was used instead of potassium acrylate, under heating conditions 1 to 3. Based on the weight loss rates, the yields of 9-5a, 9-5b, and 9-5c corresponded to 41.0%, 68.3%, and 93.5%, respectively.

[0134] Examples 9-6a to 9-6c: Reactions were carried out in the same manner as in Examples 9-5a to 9-5c, except that 20 parts by mass of water was added. Based on the weight loss rate, the yield of 9-6a was 33.8%, the yield of 9-6b was 58.8%, and the yield of 9-6c was 76.3%, respectively.

[0135] Example 10: 0.500 g of raw material (F) and 0.025 g of potassium carbonate were mixed in a container and placed in a vacuum distiller. The mixture was heated for approximately 140 minutes under conditions of a bath temperature of 100-155°C and an internal pressure of 20.6-16.0 kPa. Initially, a gas believed to be carbon dioxide was generated. 0.470 g of a distillate was then obtained. GC analysis of the obtained distillate revealed that it contained 97.0% acrylic acid, giving a yield of 94%.

[0136] The conditions and results of Examples 5 to 9 and Comparative Examples 5 and 6 are summarized in Tables 2 and 3.

[0137] Tables 2 and 3 confirm that the production method of the present invention described in Examples 5 to 9 allows the reaction to proceed even at relatively low temperatures, such as around 150°C, and produces acrylic acid. For example, in Examples 5, 6-2 to 6-4, 6-7, 7-2, 8-2, and 9-2 to 9-3, in which the mixture containing 3-hydroxycarboxylic acid and / or its polymer and a basic catalyst further contained a carboxylic acid anhydride, acrylic acid was obtained regardless of the molecular weight of the raw material. Furthermore, in Examples 6 to 9, in which the weight-average molecular weight of the 3-hydroxycarboxylic acid polymer contained in the raw material was 10,000 or higher, acrylic acid was obtained even without further containing a carboxylic acid anhydride. In contrast, in Comparative Examples 5 and 6, the desired product, acrylic acid, was hardly obtained. Furthermore, comparing Example 9-5 with Example 9-6, Example 9-5, which contained a lower water content in the mixture, had a higher yield of the desired product, acrylic acid, than Example 9-6, which contained water in the mixture. In addition, when Example 9-5c and Example 10 were compared, which had the same types and ratios of raw materials and basic catalysts, it was confirmed that the weight loss rate in Example 9-5c was almost the same as the yield of acrylic acid measured by GC analysis in Example 10. Therefore, it can be said that the weight loss rate in each of the above examples corresponds to the yield.

Claims

1. A method for producing a (meth)acrylic acid compound using a hydroxycarboxylic acid and / or a polymer thereof as a raw material, comprising at least a reaction step of heating a mixture containing a hydroxycarboxylic acid and / or a polymer thereof and a basic catalyst to react with each other to produce a (meth)acrylic acid compound, in which (1) the mixture further contains a carboxylic acid anhydride, and / or (2) the weight average molecular weight of the polymer of the hydroxycarboxylic acid contained in the raw material is 10,000 or more.

2. A method for producing a (meth)acrylic acid compound using a 3-hydroxycarboxylic acid and / or a polymer thereof as a raw material, comprising at least a reaction step of heating a mixture containing a 3-hydroxycarboxylic acid and / or a polymer thereof, a basic catalyst, and a carboxylic acid anhydride to react with each other and produce a (meth)acrylic acid compound, according to claim 1.

3. The method according to claim 1, wherein the hydroxycarboxylic acid is at least one selected from the group consisting of 2-hydroxycarboxylic acids and 3-hydroxycarboxylic acids.

4. The method according to claim 2, wherein the carboxylic acid anhydride is (meth)acrylic anhydride.

5. The (meth)acrylic anhydride has the formula (I): [In formula (I), R １ ~R ３ and each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

6. The method of claim 1, wherein the basic catalyst is selected from the group consisting of alkali metal carboxylates, quaternary ammonium carboxylates, and ammonium betaines.

7. The method according to claim 1, wherein the basic catalyst is at least one carboxylate alkali metal salt selected from the group consisting of alkali metal salts of α,β-ethylenically unsaturated monocarboxylic acids and alkali metal salts of aliphatic monocarboxylic acids.

8. The method according to claim 1, wherein the basic catalyst is at least one alkali metal carboxylate selected from the group consisting of alkali metal (meth)acrylates and alkali metal acetates.

9. The method according to claim 1, wherein the amount of the basic catalyst in the mixture is 0.1 to 20 parts by mass per 100 parts by mass of the total of the hydroxycarboxylic acid and its polymer.

10. The method according to claim 2, wherein the amount of the carboxylic acid anhydride in the mixture is 1 to 50 parts by mass per 100 parts by mass of the total of the hydroxycarboxylic acid and its polymer.

11. The method according to claim 1, wherein the heating temperature in the reaction step is 80 to 220°C.

12. The hydroxycarboxylic acid is 3-hydroxypropionic acid, and the carboxylic acid anhydride is R １ ~R ３ The method according to claim 2 , wherein the (meth)acrylic anhydride is represented by formula (I), in which represents a hydrogen atom.

13. The method of claim 1, wherein the mixture further comprises a polymerization inhibitor.

14. The method according to claim 1, wherein the content of the solvent in the mixture is 0 to 50% by mass based on the total amount of the mixture.

15. The production method described in claim 1, wherein the weight average molecular weight of the hydroxycarboxylic acid polymer contained in the raw material is 10,000 or more, and the water content in the mixture is 0 to 15 mass % based on the total amount of the mixture.

16. The method according to any one of claims 1 to 15, further comprising a step of distilling off the (meth)acrylic acid compound produced in the reaction step.

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