Method for producing thiol compound

Abstract

A method for producing a thiol compound comprises the step of irradiating a colored thiol compound or a composition containing the thiol compound with light. Preferably, in the step of irradiating the composition with light having a wavelength of 250 nm to 600 nm.

Description

Technical Field

[0001] The present invention relates to a method for producing a thiol compound.

[0002] This application claims priority based on Japanese Patent Application No. 2020-095577 filed in Japan on June 1, 2020, the contents of which are incorporated herein by reference. Background Art

[0003] In recent years, from the viewpoint of energy saving and productivity improvement, there is a demand for a curable resin having good curability that cures quickly with low energy. As such a curable resin, a curable resin containing thiols has attracted attention.

[0004] For example, Patent Documents 1 and 2 describe photocurable resin compositions containing thiol compounds. Patent Document 3 describes photocuring a resin composition containing a thiol compound and then thermally curing it. Patent Documents 4 to 7 describe resin compositions containing thiol compounds that are excellent in low-temperature curing properties.

[0005] In addition, Patent Document 8 describes a method for producing a mercaptocarboxylic acid polyol ester by subjecting a mercaptocarboxylic acid or a mercaptocarboxylic acid ester to an esterification reaction with a polyol. Patent Document 8 describes that the produced pentaerythritol tetrakis(3-mercaptobutyrate) is a pale yellow liquid.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 5801556

[0009] Patent Document 2: Japanese Patent No. 6468315

[0010] Patent Document 3: Japanese Patent No. 6184003

[0011] Patent Document 4: Japanese Patent Application Publication No. 2015-93887

[0012] Patent Document 5: Japanese Patent Application Publication No. 2017-43721

[0013] Patent Document 6: Japanese Patent Application Publication No. 2016-12131

[0014] Patent Document 7: Japanese Patent Application Publication No. 2016-104875

[0015] Patent Document 8: Japanese Patent Application Publication No. 2011-084479

[0016] Patent Document 9: Japanese Patent No. 5713886 Summary of the invention

[0017] Problems to be solved by the invention

[0018] Conventionally, curable resins used for specific applications are required to have little coloration and excellent transparency. The specific applications include, for example, optical materials and the outer surface of a final product.

[0019] In the curable resin used for such a specific purpose, in recent years, it is also required to improve the curability. However, thiol compounds are typically sometimes colored yellow, or orange, brown, red, etc. In the curable resin requiring transparency, it is difficult to make it contain colored thiol compounds in order to improve the curability. Therefore, it is required to reduce the colored technology of thiol compounds.

[0020] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a thiol compound which can reduce coloration of the thiol compound.

[0021] Methods for solving problems

[0022] [1] A method for producing a thiol compound, comprising the step of irradiating a colored thiol compound or a composition containing the thiol compound with light.

[0023] [2] The method for producing a thiol compound according to [1], wherein the light includes light having a wavelength of 250 nm to 600 nm.

[0024] [3] The method for producing a thiol compound according to [1] or [2], wherein the thiol compound or the composition has a Heiger color value of 100 or more,

[0025] The light irradiation step is performed until the Hessian value of the thiol compound or the composition becomes less than 100.

[0026] [4] The method for producing a thiol compound according to any one of [1] to [3], wherein the thiol compound comprises a thiol having at least one secondary mercapto group.

[0027] [5] The method for producing a thiol compound according to any one of [1] to [3], wherein the thiol compound comprises one or both of 3-mercaptocarboxylic acid and 3-mercaptocarboxylic acid ester.

[0028] [6] The method for producing a thiol compound according to [5], wherein the thiol compound comprises one or both of 3-mercaptobutyric acid and 3-mercaptobutyric acid ester.

[0029] [7] The method for producing a thiol compound according to [6], wherein the 3-mercaptobutyric acid ester is any one of the compounds represented by the following formulas (1) to (4).

[0030]

[0031] (In formula (1), R 1 represents a hydrogen atom or a group represented by formula (5).

[0032] (In formula (2), R 2 , R 3 Each independently represents a hydrogen atom or a group represented by formula (5).

[0033] (In formula (3), R 4 , R 5 Each independently represents a hydrogen atom or a group represented by formula (5).

[0034] (In formula (4), R 6 , R 7 , R 8 Each independently represents a hydrogen atom or a group represented by formula (5).

[0035] (In formula (5), * indicates the position at which the compound represented by formula (1) to (4) is bonded.)

[0036] [8] The method for producing a thiol compound according to [6], wherein the 3-mercaptobutyric acid ester is any one of the compounds represented by the following formulas (6) to (9).

[0037]

[0038] [9] The method for producing a thiol compound according to any one of [1] to [8], wherein the composition comprises the thiol compound and at least one solvent selected from the group consisting of toluene, xylene, cyclohexane, methylcyclohexane, acetonitrile, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and water.

[0039] Effects of the Invention

[0040] The method for producing a thiol compound of the present invention comprises a light irradiation step of irradiating a colored thiol compound or a composition containing a colored thiol compound with light. Therefore, according to the method for producing a thiol compound of the present invention, coloration of the thiol compound can be reduced. DETAILED DESCRIPTION

[0041] Means for Solving the Problems The present inventors have conducted intensive studies as described below in order to solve the above-mentioned problems.

[0042] Generally, the compound is stored in a light-shielded environment. This is to prevent the compound from being degraded by light energy. It is also believed that thiol compounds will degrade if exposed to light, so they are stored in a light-shielded environment like general compounds.

[0043] However, as a result of intensive studies by the present inventors, it has been found that even a colored thiol compound is decolorized by exposing it to light.

[0044] It is presumed that this is because, in the colored thiol compound, impurities whose details are unclear are decomposed by light energy, and changes such as becoming colorless substances occur. Generally speaking, in the thiol compound, impurities such as byproducts and remaining raw materials generated during synthesis are contained. The thiol compound is purified as needed during the manufacture and / or after manufacture. Therefore, the impurity amount contained in the thiol compound used in the material of curable resin is very small. However, the details of the impurities colored by the originally colorless and transparent thiol compound are unclear. Therefore, the removal method is also unclear, and it is presumed that it is sometimes not fully removed.

[0045] Therefore, the present inventors further conducted studies and confirmed that the coloring of the thiol compound can be reduced regardless of the type of the thiol compound by irradiating a colored thiol compound or a composition containing the colored thiol compound with light, thereby arriving at the present invention.

[0046] Hereinafter, the method for producing the thiol compound of the present invention will be described in detail. In addition, the present invention is not limited only to the embodiments described below.

[0047] The method for producing a thiol compound according to the present embodiment includes a light irradiation step of irradiating a colored thiol compound or a composition containing the colored thiol compound with light.

[0048] "Colored thiol compounds"

[0049] The colored thiol compound contains impurities whose details are unclear. The so-called colored thiol compound is not particularly limited as long as it is a thiol compound with a higher Heckel value than the pure substance. For example, the colored thiol compound is a substance with a Heckel value of 100 or more, a substance with a Heckel value of 80 or more, a substance with a Heckel value of 40 or more, or a substance with a Heckel value of 20 or more. Generally speaking, if the Heckel value is 10 or more, coloring can be confirmed by visual observation.

[0050] The colored thiol compound has at least one thiol group. The thiol group may be any one of a primary thiol group, a secondary thiol group, and a tertiary thiol group. The colored thiol compound may have two or more thiol groups selected from a primary thiol group, a secondary thiol group, and a tertiary thiol group. The colored thiol compound may be only one type or may be two or more types.

[0051] Examples of the thiol compound having a primary mercapto group include 3-mercaptopropionic acid, 3-mercaptopropionic acid ester, bisphenol A type thiol, polyether polymer type thiol, and the like.

[0052] Examples of 3-mercaptopropionic acid esters include esters of 3-mercaptopropionic acid and an alcohol selected from 1,4-butanediol, 1,3,5-tris(2-hydroxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, trimethylolpropane, and pentaerythritol. Specifically, pentaerythritol tetrakis(3-mercaptopropionate) and trimethylolpropane tris(3-mercaptopropionate) can be used.

[0053] As bisphenol A type mercaptan, for example, bisphenol A type mercaptan QX11 manufactured by Mitsubishi Chemical Corporation can be used.

[0054] As the polyether polymer type mercaptan, for example, polyether polymer type mercaptan CAPCURE 3-800 manufactured by Cognis can be used.

[0055] Examples of the thiol compound having a secondary mercapto group include 3-mercaptobutyric acid and 3-mercaptobutyric acid esters. Examples of 3-mercaptobutyric acid esters include esters of 3-mercaptobutyric acid and an alcohol selected from 1,4-butanediol, 1,3,5-tris(2-hydroxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, trimethylolpropane, and pentaerythritol.

[0056] The colored thiol compound preferably comprises a thiol having at least one secondary thiol group.

[0057] The colored thiol compound preferably contains one or both of 3-mercaptocarboxylic acid and 3-mercaptocarboxylic acid ester, and more preferably contains one or both of 3-mercaptobutyric acid and 3-mercaptobutyric acid ester.

[0058] Specifically, 3-mercaptobutyric acid ester is preferably any one of the compounds represented by the following formulae (1) to (4). When the colored thiol compound includes any one of the compounds represented by the following formulae (1) to (4), the effect of reducing the coloring of the thiol compound by irradiation light is significant.

[0059]

[0060] (In formula (1), R 1 represents a hydrogen atom or a group represented by formula (5).

[0061] (In formula (2), R 2 , R 3 Each independently represents a hydrogen atom or a group represented by formula (5).

[0062] (In formula (3), R 4 , R 5 Each independently represents a hydrogen atom or a group represented by formula (5).

[0063] (In formula (4), R 6 , R 7 , R 8 Each independently represents a hydrogen atom or a group represented by formula (5).

[0064] (In formula (5), * indicates the position at which the compound represented by formula (1) to (4) is bonded.)

[0065] The 3-mercaptobutyric acid ester is more preferably any one of 1,4-bis(3-mercaptobutyryloxy)butane represented by the following formula (6), 1,3,5-tris(2-(3-mercaptobutyryloxy)ethyl)-1,3,5-triazine-2,4,6-trione represented by the following formula (7), trimethylolpropane tris(3-mercaptobutyric acid ester) represented by the following formula (8), and pentaerythritol tetrakis(3-mercaptobutyric acid ester) represented by the following formula (9).

[0066]

[0067] The thiol compound can be produced by a conventionally known method.

[0068] For example, as described in Patent Document 9, 3-mercaptocarboxylic acid such as 3-mercaptobutyric acid can be synthesized by reacting an α,β-unsaturated carboxylic acid with hydrogen sulfide in an aqueous solution in the presence of a basic compound.

[0069] For example, 3-mercaptobutyric acid esters such as compounds represented by formulas (6) to (9) can be synthesized by synthesizing 3-mercaptobutyric acid and then subjecting the 3-mercaptobutyric acid to an esterification reaction with a polyol as described in Patent Document 8.

[0070] (Composition)

[0071] The composition in the present embodiment contains a colored thiol compound and, if necessary, contains a solvent and / or other compounds other than the thiol compound. The Heckel value of the composition containing the colored thiol compound is, for example, 100 or more. The Heckel value of the composition containing the colored thiol compound may be 80 or more, 40 or more, or 20 or more. Generally speaking, if the Heckel value is 10 or more, coloring can be confirmed by visual observation.

[0072] [Solvent]

[0073] The composition in this embodiment may contain a solvent as necessary. The solvent may be appropriately selected according to the type of the thiol compound and the wavelength of the light irradiated in the light irradiation step.

[0074] As the solvent, for example, organic solvents such as hydrocarbons, alcohols, esters, ketones, and ethers, and / or water can be used. Specifically, it is preferred to use at least one selected from toluene, xylene, cyclohexane, methylcyclohexane, acetonitrile, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and water. Among these solvents, acetonitrile and water do not show strong light absorption to light in the range of wavelengths above 200nm, and are easy to make the light irradiated in the light irradiation process pass through. Therefore, when the solvent is acetonitrile and / or water, it is easy to irradiate light efficiently to the thiol compound in the light irradiation process, which is preferred.

[0075] When the thiol compound is solid at room temperature (25° C.), it is preferred to prepare a composition in which the thiol compound is dissolved or dispersed in a solvent and irradiate with light. When the composition contains a thiol compound that is solid at room temperature and a solvent in which the thiol compound is dissolved or dispersed, light is irradiated to the thiol compound uniformly without unevenness in the light irradiation step, compared with a case in which no solvent is contained. As a result, coloration of the thiol compound can be reduced with less light energy.

[0076] When the thiol compound is a liquid having high viscosity at room temperature (25° C.), it is also preferred to prepare a composition in which the thiol compound is dissolved or dispersed in a solvent and irradiate with light. When the composition contains a thiol compound which is a liquid having high viscosity at room temperature and a solvent in which the thiol compound is dissolved or dispersed, light is irradiated to the thiol compound uniformly without unevenness in the light irradiation step, compared with a case in which no solvent is contained. As a result, coloration of the thiol compound can be reduced with less light energy.

[0077] In addition, when the coloring of the thiol compound is significant (for example, the Heigl's color value is 150 or more), the thiol compound may be diluted with a solvent to prepare a composition before the light irradiation step. As a result, the concentration of the thiol compound in the liquid becomes dilute compared to the case where the light irradiation step is performed only on the thiol compound, and the light is irradiated efficiently and uniformly. As a result, the irradiation time of the irradiated light can be shortened and / or the irradiation intensity can be weakened in the light irradiation step.

[0078] In the case where the composition includes a solvent, the content of the solvent in the composition is not particularly limited, for example, it can be 10 to 90% by mass, preferably 30 to 70% by mass, more preferably 40 to 60% by mass, and can be appropriately determined according to the type of thiol compound, etc. If the content of the solvent in the composition is 30% by mass or more, the effect of light reaching the inside becomes significant by dilution, and light can be uniformly and efficiently irradiated to the thiol compound in the light irradiation process. In addition, if the content of the solvent in the composition is 70% by mass or less, the consumption of the solvent can be reduced, and the light irradiation process can be carried out more efficiently with smaller equipment. Further, if the content of the solvent in the composition is 70% by mass or less, the solvent can be easily removed when the solvent is removed after the light irradiation process, and the processing efficiency can be improved when the solvent is recycled and reused.

[0079] [Other compounds other than thiol compounds]

[0080] The composition containing the thiol compound in this embodiment may contain other compounds that are neither thiol compounds nor solvents as needed. Examples of other compounds include byproducts generated when synthesizing the thiol compound, residual raw materials, stabilizers, pH adjusters, etc., which can be determined based on the use of the thiol compound after the light irradiation step, etc., and are not particularly limited.

[0081] When the composition contains other compounds other than the thiol compound, the content of the other compounds in the composition is not particularly limited, and may be, for example, 0.1 to 10% by mass, and may be appropriately determined depending on the type of the thiol compound.

[0082] Preferably, the composition does not contain a polymer. Here, the so-called polymer refers to a substance obtained by combining more than 5 monomers, typically a substance obtained by combining more than 10 monomers. When the composition contains a polymer, it is not easy to obtain the decolorization effect brought about by the irradiation light. In more detail, the movement of the molecules of the polymerized substance is restricted, and generally the fluidity is low or completely absent. Therefore, it is known that chemical reactions are not easy to occur in the composition containing the substance. It is inferred that even if the composition containing the polymer is irradiated with light, the impurities whose details are unclear are not easy to be decomposed. The content of the polymer in the composition is preferably less than 10% by mass, more preferably less than 5% by mass.

[0083] In addition, it is preferred that the composition does not contain a photopolymer. This is because, in addition to the state in which the movement of the molecules of the photopolymer is restricted, it is not easy to obtain the decolorization effect brought about by the irradiation light for the following reasons. Photopolymers generally contain compounds such as photopolymerization initiators and their decomposition products. If these compounds are irradiated with light excessively, there are many colored substances. Therefore, it is presumed that by irradiating light to the composition containing the photopolymer, not only the impurities whose details are unclear contained in the composition are sometimes decomposed, but these compounds are colored instead, and it is not easy to obtain the decolorization effect. The content of the photopolymer in the composition is preferably less than 10% by mass, and more preferably less than 5% by mass.

[0084] [Light irradiation process]

[0085] In the light irradiation step of the present embodiment, the colored thiol compound or the composition containing the colored thiol compound is irradiated with light. In the production process of the thiol compound of the present embodiment, the light irradiation step may be performed once or a plurality of times.

[0086] In the light irradiation process, the wavelength of the irradiated light can be appropriately determined according to the type of thiol compound and the composition of the composition. In the present embodiment, the irradiated light preferably includes light with a wavelength of 250nm to 600nm. Light with a wavelength of 250nm or more is not easily shielded by the absorption of the thiol compound and the organic solvent, and is preferred. In addition, light with a wavelength of 600nm or less is preferred because it has sufficient energy to reduce the coloring of the thiol compound. In order to effectively reduce the coloring of the colored thiol compound, the irradiated light more preferably includes light with a wavelength in the range of 300nm to 550nm, and further preferably includes light in the range of 350 to 500nm.

[0087] The type of light source used in the light irradiation process is not particularly limited. Specifically, as the light source, sunlight, incandescent lamps, fluorescent lamps, light emitting diode (LED) lamps, etc. can be used. Among these light sources, sunlight has a strong irradiation intensity, contains light of a wide range of wavelengths, and does not require the supply of energy from a power supply, etc., and can therefore be preferably used.

[0088] The evaluation method of coloration is not particularly limited, but since the color of the colored thiol compound is typically yellow, the Heilongjiang color value (APHA) can be preferably used. As a method for determining the Heilongjiang color value, for example, a method of measuring with a spectrometer or a method using a colorimetric tube can be used.

[0089] The amount of change in the Heiger color value (APHA) of the measurement object (the colored thiol compound or the composition containing the colored thiol compound) caused by performing the light irradiation step can be adjusted by adjusting the wavelength, irradiation intensity, and irradiation amount (light irradiation time) of the irradiated light relative to the composition and amount of the colored thiol compound or the composition containing the colored thiol compound. The stronger and more the energy of the irradiated light in the light irradiation step is, the greater the effect of reducing the coloration of the colored thiol compound is.

[0090] For example, when the Heck value (APHA) of the thiol compound or the composition containing the thiol compound is 100 or more, the light irradiation step is preferably performed until the Heck value becomes less than 100. In this case, the thiol compound after the light irradiation step can be preferably used in applications as a resin raw material for optical materials, exterior materials, coatings, etc. In order to obtain a thiol compound more suitable for these applications, the light irradiation step is more preferably performed until the Heck value becomes 80 or less, and further preferably performed until the Heck value becomes 60 or less.

[0091] Even when the APHA value of the thiol compound or the composition containing the thiol compound is less than 100, a light irradiation step may be performed to further reduce coloration. For example, when the APHA value is 80 or more, the light irradiation step may be performed until the APHA value becomes less than 80, more preferably until the APHA value becomes 70 or less, and further preferably until the APHA value becomes 60 or less. When the APHA value is 60 or more, the light irradiation step may be performed until the APHA value becomes less than 60, more preferably until the APHA value becomes 50 or less, and further preferably until the APHA value becomes 40 or less.

[0092] As a container for containing the thiol compound or the composition containing the thiol compound during the light irradiation step, for example, a resin container made of polypropylene or the like, a glass container, etc. can be used, and the material and shape are not particularly limited. As the container, when the thiol compound or the composition containing the thiol compound in the container is irradiated with light from outside the container during the light irradiation step, it is preferable to use a container having good transmittance to light of the irradiated wavelength.

[0093] The light irradiation step is preferably performed while stirring the thiol compound or the composition containing the thiol compound contained in the container. This can efficiently reduce the coloring of the colored thiol compound without unevenness, and can efficiently diffuse the heat provided to the thiol compound or the composition containing the thiol compound from the light source.

[0094] The temperature, pressure and other conditions during the light irradiation step are not particularly limited.

[0095] The thiol compound after the light irradiation step or the composition containing the thiol compound can be used directly as a resin raw material for optical materials, exterior materials, coatings, etc. In the case where the composition after the light irradiation step contains a solvent, the solvent can be removed by a known method as needed. In addition, in the case where the composition after the light irradiation step contains other compounds other than the thiol compound, the other compounds can be removed by a known method as needed.

[0096] The thiol compound after the light irradiation step can be used as an intermediate product.

[0097] For example, the thiol compound after the light irradiation step may be 3-mercaptocarboxylic acid synthesized as an intermediate product in the step of synthesizing 3-mercaptocarboxylic acid esters such as 3-mercaptobutyrate. 3-mercaptocarboxylic acid esters may be produced by esterifying the 3-mercaptocarboxylic acid after the light irradiation step, thereby obtaining a product with less coloration.

[0098] The method for producing a thiol compound of the present embodiment includes a light irradiation step of irradiating a colored thiol compound or a composition containing the colored thiol compound with light. Therefore, according to the method for producing a thiol compound of the present embodiment, coloration of the thiol compound can be reduced.

[0099] The method for producing a thiol compound according to the present embodiment can be easily implemented by adding a light irradiation step to the conventional method for producing a thiol compound without changing the conventional method for producing a thiol compound.

[0100] Furthermore, the light irradiation step in the method for producing a thiol compound according to the present embodiment does not require special equipment and can be easily performed by using sunlight as a light source.

[0101] Furthermore, the method for producing a thiol compound according to the present embodiment can be carried out without using a decolorizing agent, an adsorbent, or other compound. Therefore, for example, compared with the case where a decolorizing agent and / or an adsorbent, or other compound is added to an already colored thiol compound or a composition containing the colored thiol compound, it is preferable that impurities and foreign substances are not mixed in due to the newly added compound.

[0102] Example

[0103] Hereinafter, the present invention will be specifically described by way of examples and comparative examples. In addition, the examples shown below are for easier understanding of the contents of the present invention, and the present invention is not limited to these examples.

[0104] The following Examples and Comparative Examples were carried out at room temperature (25° C.) unless otherwise specified.

[0105] In the following examples and comparative examples, the Heige color value (APHA) was determined using the spectrophotometer SD6000 of Nippon Denshoku Industries Co., Ltd. The Heige color value calibration was carried out using APHA 500, 200, 100, 50, 20, 10, 5 prepared by diluting a color standard solution (1000 degrees) (Kanto Chemical, for color test) with pure water and pure water (APHA0).

[0106] [Example 1]

[0107] The compound represented by formula (9) was synthesized according to the method described in Patent Document 8. The APHA value (APHA) of the synthesized compound represented by formula (9) was determined. The result was APHA160.

[0108] The compound represented by the formula (9) of APHA160 was subjected to a light irradiation step by the method described below.

[0109] That is, 50 mL (60 g) of the compound represented by formula (9) of APHA160 was placed in a translucent polypropylene container (IBOI (registered trademark), wide-mouth bottle 50 mL, manufactured by Azwan Co., Ltd.) and sealed. The container was then left standing under a light source (white LED; LED Backlight TENQOO (trade name); manufactured by Toshiba Lifetech Co., Ltd.), and light was irradiated onto the compound represented by formula (9) through the container.

[0110] As shown in Table 1, the Heigen value (APHA) of the compound represented by formula (9) decreased over time after the start of light irradiation, and became APHA72 after 30 days. Then, the container was left in a dark place for 12 days, but the Heigen value of the compound represented by formula (9) did not change. Therefore, it can be confirmed that the compound represented by formula (9) is less colored by irradiating light using a white LED, and does not color even if it is stored in a dark place afterwards.

[0111] Table 1

[0112]

[0113] [Example 2]

[0114] 50 mL (60 g) of the compound represented by formula (9) of APHA160, which is the same as in Example 1, was placed in the same container as in Example 1 and sealed. The container was then placed near a south-facing window where sunlight was shining, and the compound represented by formula (9) was irradiated with light through the container.

[0115] As shown in Table 1, the Heck value (APHA) of the compound represented by formula (9) decreased over time after the start of light irradiation, and became APHA23 after 30 days. Then, the container was left in a dark place for 12 days. As a result, the compound represented by formula (9) became APHA22, which was almost unchanged. Therefore, it can be confirmed that the compound represented by formula (9) is less colored by irradiation with sunlight, and does not color even if it is stored in a dark place afterwards.

[0116] [Comparative Example 1]

[0117] 50 mL (60 g) of the compound represented by formula (9) of APHA160, which is the same as in Example 1, was placed in the same container as in Example 1 and sealed. The container was then wrapped with aluminum foil to block light, and allowed to stand under the same light source (white LED) as in Example 1, and the container wrapped with aluminum foil was irradiated with light.

[0118] As shown in Table 1, the APHA value of the compound represented by formula (9) hardly changed even after light irradiation, and after 30 days, it was APHA 158. Then, the container was left in a dark place for 12 days. As a result, the APHA value of the compound represented by formula (9) was APHA 160.

[0119] [Example 3]

[0120] A liquid was prepared by mixing the compound represented by formula (9) of APHA160, which was the same as in Example 1, with toluene (Jure Chemical, special grade) at a volume ratio of 1:1. The Heck value (APHA) of the obtained mixed liquid was determined to be APHA67. 50 mL of the mixed liquid was measured and added to the same container as in Example 1 and sealed. Furthermore, the container was left to stand under the same light source (white LED) as in Example 1, and light was irradiated to the mixed liquid through the container.

[0121] As shown in Table 2, the APHA value of the mixed solution decreased over time after the start of light irradiation and reached APHA 37 after 12 days.

[0122] Table 2

[0123]

[0124] [Example 4]

[0125] A mixed solution was prepared in the same manner as in Example 3 except that acetonitrile (Fuji Film & Co., Ltd., special reagent grade) was used instead of toluene. The Heck's color value (APHA) of the obtained mixed solution was determined to be APHA 100. 50 mL of the mixed solution was measured and placed in the same container as in Example 1 and sealed. Furthermore, the container was left standing under the same light source (white LED) as in Example 1, and light was irradiated to the mixed solution through the container.

[0126] As shown in Table 2, the APHA value of the mixed solution decreased over time after the start of light irradiation and reached APHA 37 after 12 days.

[0127] [Example 5]

[0128] The Heiger color value (APHA) of the compound represented by formula (6) (Kalenzu MT (registered trademark) BD1 (manufactured by Showa Denko K.K.)) was determined. The result was APHA57. 30 mL (33 g) of the compound represented by formula (6) of APHA57 was added to the same container as in Example 1 and sealed. Furthermore, the container was left to stand under the same light source (white LED) as in Example 1, and light was irradiated to the compound represented by formula (6) through the container.

[0129] As shown in Table 3, the Heck value (APHA) of the compound represented by formula (6) decreased over time after the start of light irradiation and became APHA38 after 8 days.

[0130] Table 3

[0131]

[0132] [Comparative Example 2]

[0133] 30 mL (33 g) of the compound represented by formula (6) of APHA57, which is the same as in Example 5, was placed in the same container as in Example 1 and sealed. The container was then wrapped with aluminum foil to block light, and allowed to stand under the same light source (white LED) as in Example 1, and the container wrapped with aluminum foil was irradiated with light.

[0134] As shown in Table 3, the Heck value (APHA) of the compound represented by formula (6) hardly changed even after irradiation with light, and was APHA 58 after 8 days.

[0135] [Example 6]

[0136] The Heiger color value (APHA) of the compound represented by formula (7) (Kalenzu MT (registered trademark) NR1 (manufactured by Showa Denko K.K.)) was determined. The result was APHA45. 30 mL (38 g) of the compound represented by formula (7) of APHA45 was added to the same container as in Example 1 and sealed. Furthermore, the container was left to stand under the same light source (white LED) as in Example 1, and light was irradiated to the compound represented by formula (7) through the container.

[0137] As shown in Table 3, the Heck value (APHA) of the compound represented by formula (7) decreased over time after the start of light irradiation and became APHA36 after 8 days.

[0138] [Comparative Example 3]

[0139] 30 mL (38 g) of the compound represented by formula (7) of APHA45, ​​which is the same as in Example 6, was placed in the same container as in Example 1 and sealed. The container was then wrapped with aluminum foil to block light, and allowed to stand under the same light source (white LED) as in Example 1, and the container wrapped with aluminum foil was irradiated with light.

[0140] As shown in Table 3, the Heck value (APHA) of the compound represented by formula (7) hardly changed even after irradiation with light, and was APHA 46 after 8 days.

[0141] [Example 7]

[0142] The Heiger color value (APHA) of the compound represented by formula (8) (Kalenzu MT (registered trademark) TPMB (manufactured by Showa Denko K.K.)) was determined. The result was APHA42. 30 mL (34 g) of the compound represented by formula (8) of APHA42 was added to the same container as in Example 1 and sealed. Furthermore, the container was left to stand under the same light source (white LED) as in Example 1, and light was irradiated to the compound represented by formula (8) through the container.

[0143] As shown in Table 3, the Heck value (APHA) of the compound represented by formula (8) decreased over time after the start of light irradiation and became APHA31 after 8 days.

[0144] [Comparative Example 4]

[0145] 30 mL (34 g) of the compound represented by formula (8) of APHA42, which is the same as in Example 7, was placed in the same container as in Example 1 and sealed. The container was then wrapped with aluminum foil to block light, and allowed to stand under the same light source (white LED) as in Example 1, and the container wrapped with aluminum foil was irradiated with light.

[0146] As shown in Table 3, the Heck value (APHA) of the compound represented by formula (8) did not change even after irradiation with light, and was APHA 42 after 8 days.

[0147] [Example 8]

[0148] The Heiger color value (APHA) of the compound represented by formula (9) (Kalenzu MT (registered trademark) PE1 (manufactured by Showa Denko K.K.)) was determined. The result was APHA57. 30 mL (36 g) of the compound represented by formula (9) of APHA57 was added to the same container as in Example 1 and sealed. Furthermore, the container was left to stand under the same light source (white LED) as in Example 1, and light was irradiated to the compound represented by formula (9) through the container.

[0149] As shown in Table 3, the Heck value (APHA) of the compound represented by formula (9) decreased over time after the start of light irradiation and became APHA32 after 8 days.

[0150] [Comparative Example 5]

[0151] 30 mL (36 g) of the compound represented by formula (9) of APHA57, which is the same as in Example 8, was placed in the same container as in Example 1 and sealed. The container was then wrapped with aluminum foil to block light, and allowed to stand under the same light source (white LED) as in Example 1, and the container wrapped with aluminum foil was irradiated with light.

[0152] As shown in Table 3, the Heck value (APHA) of the compound represented by formula (9) hardly changed even after light irradiation, and was APHA 56 after 8 days.

[0153] [Example 9]

[0154] 3-Mercaptobutyric acid was synthesized according to the method described in Patent Document 9. The Heiger color value (APHA) of the synthesized 3-mercaptobutyric acid was determined. The result was APHA25. 30 mL (34 g) of 3-mercaptobutyric acid of APHA25 was added to the same container as in Example 1 and sealed. Furthermore, the container was left to stand under the same light source (white LED) as in Example 1, and light was irradiated to the 3-mercaptobutyric acid through the container.

[0155] As shown in Table 3, the APHA value of 3-mercaptobutyric acid decreased over time after the start of light irradiation and became APHA 14 after 8 days.

[0156] [Comparative Example 6]

[0157] 30 mL (34 g) of 3-mercaptobutyric acid of the same APHA25 as in Example 9 was added to the same container as in Example 1 and sealed. The container was then wrapped with aluminum foil to block light, and allowed to stand under the same light source (white LED) as in Example 1, and light was irradiated onto the container wrapped with aluminum foil.

[0158] As shown in Table 3, the APHA value of 3-mercaptobutyric acid hardly changed even when irradiated with light, and was APHA25 after 8 days.

[0159] [Example 10]

[0160] The compound represented by formula (9) was synthesized according to the method described in Patent Document 8. The APHA value (APHA) of the synthesized compound represented by formula (9) was determined. The result was APHA169.

[0161] The compound represented by the formula (9) of APHA169 was subjected to a light irradiation step by the method described below.

[0162] That is, a light source was inserted into a 50 mL three-necked flask containing 50 mL (60 g) of the compound represented by formula (9) to which APHA169 was added and a stirring bar, and the compound represented by formula (9) was irradiated with light while stirring. As the light source, a photochemical reaction LED light source device PER-AMP (wavelength 470 nm, output 610 mW (manufactured by Creative Science Laboratory Co., Ltd.) was used in combination with an LED lamp PER-LED-470 and a power supply unit PER-AMP-N4.

[0163] As shown in Table 4, the Heck value (APHA) of the compound represented by formula (9) decreased over time after the start of light irradiation and became APHA 43 after 7 hours.

[0164] Table 4

[0165]

[0166] [Example 11]

[0167] As the light source, a LED light source device PER-AMP for photochemical reaction (wavelength 385nm, output 605mW (manufactured by Creative Science Laboratory Co., Ltd.) was used in combination with an LED lamp PER-LED-385 and a power supply unit PER-AMP-N4. Except for this, the light irradiation process was carried out in the same manner as in Example 10.

[0168] As shown in Table 4, the Heck value (APHA) of the compound represented by formula (9) decreased over time after the start of light irradiation and became APHA42 after 7 hours.

[0169] [Example 12]

[0170] As the light source, a LED light source device PER-AMP for photochemical reaction (wavelength 325nm, output 36mW (manufactured by Creative Science Laboratory Co., Ltd.) was used in combination with an LED lamp PER-LED-325 and a power supply unit PER-AMP-D2. Except for this, the light irradiation process was carried out in the same manner as in Example 10.

[0171] As shown in Table 4, the Heck value (APHA) of the compound represented by formula (9) decreased over time after the start of light irradiation, becoming APHA 168 after 7 hours and APHA 149 after 24 hours.

[0172] In Table 5, the thiol compounds in the measurement objects (thiol compounds or compositions containing the thiol compounds) in Examples 1 to 12 and Comparative Examples 1 to 6, the amount of the measurement objects, the light source, the time for which the light irradiation process was performed (light irradiation time), and the Hague color values ​​(APHA) before and after the light irradiation process are summarized and displayed.

[0173]

[0174] As shown in Table 5, in Examples 1 to 12, it was confirmed that the Hirsch value (APHA) of the thiol compound or the composition containing the thiol compound was reduced and coloration was reduced by performing the light irradiation step.

[0175] On the other hand, in Comparative Examples 1 to 6 in which the light irradiation step was performed while shielding the light, no decrease in the Hague color value (APHA) of the thiol compound or the composition containing the thiol compound due to the light irradiation step was observed.

Claims

1. A method for producing a thiol compound, comprising the step of irradiating a colored thiol compound or a composition containing the thiol compound with light, The colored thiol compound has a Heiger value of 10 or more, and the thiol compound contains one or both of 3-mercaptocarboxylic acid and 3-mercaptocarboxylic acid ester, The light includes light with a wavelength of 250 nm to 600 nm.

2. The method for producing a thiol compound according to claim 1, wherein the thiol compound or the composition has a Heiger color value of 100 or more. The light irradiation step is performed until the Heigl's value of the thiol compound or the composition becomes less than 100. 3 . The method for producing a thiol compound according to claim 1 , wherein the thiol compound comprises a thiol having at least one secondary mercapto group. 4 . The method for producing a thiol compound according to claim 1 , wherein the thiol compound comprises one or both of 3-mercaptobutyric acid and 3-mercaptobutyric acid ester.

5. The method for producing a thiol compound according to claim 4, wherein the 3-mercaptobutyric acid ester is any one of the compounds represented by the following formulas (1) to (4): In formula (1), R 1 represents a hydrogen atom or a group represented by formula (5), In formula (2), R 2 , R 3 Each independently represents a hydrogen atom or a group represented by formula (5). In formula (3), R 4 , R 5 Each independently represents a hydrogen atom or a group represented by formula (5). In formula (4), R 6 , R 7 , R 8 Each independently represents a hydrogen atom or a group represented by formula (5). In formula (5), * represents a position at which the atom binds to the compound represented by formulae (1) to (4).

6. The method for producing a thiol compound according to claim 4, wherein the 3-mercaptobutyric acid ester is any one of the compounds represented by the following formulas (6) to (9):

7. The method for producing a thiol compound according to claim 1 or 2, wherein the composition comprises the thiol compound and at least one solvent selected from the group consisting of toluene, xylene, cyclohexane, methylcyclohexane, acetonitrile, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, methyl acetate, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and water.

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