1,3-butylene glycol product

Abstract

To provide a high-purity 1,3-butylene glycol product that is colorless and odorless (or almost colorless and odorless), unlikely to cause coloration and odor over time, and / or unlikely to cause an acid concentration increase over time even in a state containing water.SOLUTION: A 1,3-butylene glycol product containing 1,3-butylene glycol, wherein after the 1,3-butylene glycol product has been kept at 180°C for 3 hours in an air atmosphere, at least one of the contents of compounds represented by the following Formula (A) or (B) is less than 8 ppm. In the following formula(e), R1 to R4 are the same as or different from each other, representing a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be substituted with a hydroxy group, or an alkenyl group having 2 to 4 carbon atoms which may be substituted with a hydroxy group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to 1,3-butylene glycol products. This application claims priority to Japanese Patent Application Nos. 2019-239974, 2019-239975, 2019-239976, 2019-239977, 2019-239978, and 2019-239979, filed in Japan on December 28, 2019, Japanese Patent Application No. 2020-006660, filed in Japan on January 20, 2020, and Japanese Patent Application No. 2020-018910, filed in Japan on February 6, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] 1,3-Butylene glycol is a colorless, transparent, odorless liquid with properties such as low volatility, low toxicity, and high hygroscopicity, and has excellent chemical stability. Therefore, its uses are diverse, including as a raw material for various synthetic resins and surfactants, as well as cosmetics, moisture absorbents, high-boiling-point solvents, and antifreeze materials. In recent years, 1,3-butylene glycol has particularly attracted attention for its excellent properties as a moisturizer, and demand for it in the cosmetics industry is expanding.

[0003] 1,3-butylene glycol obtained by conventional manufacturing methods has a problem in that its acid concentration (acidity) increases when stored in an aqueous environment for a long period of time. The cause of this increase in acid concentration was unknown, but it was thought to be related to by-products contained in crude 1,3-butylene glycol. Cosmetics generally contain water, and a long period of time passes between production and actual use by consumers. Furthermore, the liquid properties of cosmetics are strictly controlled to ensure shelf stability. When 1,3-butylene glycol obtained by conventional methods is used in cosmetics, the increase in acid concentration can disrupt the liquid balance of the cosmetics, potentially resulting in a loss of the intended effects. Furthermore, the increase in acid concentration in cosmetics can cause skin irritation and other problems. Even in cosmetics that do not contain water, the acid concentration can increase due to moisture absorption during use or storage. Therefore, there was a need to remove by-products from crude 1,3-butylene glycol and obtain highly purified 1,3-butylene glycol.

[0004] Furthermore, 1,3-butylene glycol obtained by conventional manufacturing methods sometimes has an odor due to the influence of by-products. Even if the product is transparent immediately after production, it may develop coloration over time, posing a problem during long-term storage. For example, cosmetics are exposed to air when used and when stored after use. Furthermore, cosmetics are generally manufactured under an air atmosphere, and may also be heated for sterilization or other purposes. When 1,3-butylene glycol obtained by conventional methods is used in cosmetics, coloration can progress due to the presence of air or the influence of heat. To solve these problems, there has been a need to remove by-products from crude 1,3-butylene glycol and highly purify the resulting 1,3-butylene glycol.

[0005] As a method for obtaining high-purity 1,3-butylene glycol, a method has been proposed in which caustic soda is added to crude 1,3-butylene glycol obtained by hydrogen reduction of acetaldols and the mixture is distilled. Other methods have also been proposed, such as adding an alkali metal base to crude 1,3-butylene glycol from which high-boiling components have been removed, heat-treating the mixture, distilling the 1,3-butylene glycol, separating the alkali metal compounds and high-boiling components as residue, and then distilling the low-boiling components from the 1,3-butylene glycol fraction (Patent Documents 1 to 6). Thus, various methods for purifying 1,3-butylene glycol have been proposed to obtain high-purity 1,3-butylene glycol. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-258129 [Patent Document 2] International Publication No. 00 / 07969 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-213822 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-213824 [Patent Document 5] Japanese Patent Application Laid-Open No. 2001-213825 [Patent Document 6] Japanese Patent Application Laid-Open No. 2001-213828 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the 1,3-butylene glycol products obtained by these purification methods still contain by-products, and have problems such as an odor, an increase in acid concentration over time when water is added, and discoloration over time.

[0008] 1,3-Butylene glycol can be produced by methods such as (1) reduction (hydrogenation) of acetaldols, (2) hydrolysis of 1,3-butylene oxide, (3) selective hydrogenolysis of erythritol, (4) selective addition of water to butadiene, (5) hydrogenation of n-butanal-3-one, (6) hydrogenation of 1-butanol-3-one, (7) hydrogenation of 3-hydroxy-1-butanoic acid, (8) hydrogenation of β-butyrolactone, and (9) hydrogenation of diketene.

[0009] Among the above production methods, (1) the method of obtaining 1,3-butylene glycol by reduction (hydrogenation) of acetaldols is preferred. Among these, the method of reducing acetaldols in a liquid phase is preferred from the viewpoint of yield. The reasons for this include the fact that acetaldols have a high boiling point, are thermally unstable, and readily undergo dehydration at high temperatures to form crotonaldehyde and the like, and that the dehydration reaction and reduction (hydrogenation) reaction at high temperatures are faster than the reduction reaction. Specifically, when reducing acetaldols in a gas phase, the reaction system must be heated to a high temperature. However, subjecting acetaldols to a high temperature causes dehydration to form crotonaldehyde and the like, and the subsequent reduction reaction produces by-products such as butanol. This results in a relatively low yield of the target 1,3-butylene glycol. Therefore, to obtain a high-purity 1,3-butylene glycol product, liquid-phase reduction is preferred over gas-phase reduction.

[0010] When 1,3-butylene glycol is produced, by-products are generally produced during the production process. For example, when 1,3-butylene glycol is produced by hydrogen reduction of acetaldols, low-boiling substances (low-boiling compounds) having unsaturated bonds, such as acetaldehyde, butylaldehyde, crotonaldehyde, acetone, and methyl vinyl ketone, as well as condensates thereof (e.g., acetaldehyde trimer), hydrogenated products of the condensates, and condensates of 1,3-butylene glycol and the low-boiling substances (e.g., acetal compounds of 1,3-butylene glycol and acetaldol). Other by-products include acetals of crotonaldehyde and 1,3-butylene glycol, acetals of acetaldehyde and 1,3-butylene glycol, and acetals of acetaldol or acetaldehyde and the hydrogenated acetaldehyde trimer. In addition, other by-products include acetic acid contained as an impurity in the raw material acetaldols, and acetic acid used to neutralize the caustic soda used in the production of acetaldols, and a condensation product of 1,3-butylene glycol (an ester of acetic acid and 1,3-butylene glycol). These by-products can have properties of color-causing substances, odor-causing substances, and even acidic substances.

[0011] It is unclear whether the acetal compounds are color-causing substances, odor-causing substances, or acidic substances, and it is conceivable that they possess all of these properties, but they are believed to have strong odor-causing properties. Specifically, although the acetal compounds themselves are unlikely to be odor-causing substances, they may generate odor-causing substances over time or upon heating. Furthermore, the acetal compounds may generate acetaldol upon hydrolysis, which is an odor-causing substance and also has an oxidation (coloring) promoting effect, and therefore can also be considered a color-causing substance. Here, color-causing substances are defined to include not only substances that currently have a color, but also substances that change over time to have a color. Odor-causing substances are defined to include not only substances that currently emit an odor, but also substances that change over time to emit an odor. Acidic substances are defined to include substances whose acid concentration increases over time when they come into contact with water.

[0012] It is not clear whether the ester is a color-causing substance, an odor-causing substance, or an acidic substance, and it is possible that it has all of these properties, but it is believed to have the properties of both an odor-causing substance and an acidic substance strongly, because acetic acid is generated when the ester is hydrolyzed with water.

[0013] In addition, when 1,3-butylene glycol is produced, the by-products in the production process are thought to include a wide variety of by-products that correspond to color-causing substances, odor-causing substances, or acidity-causing substances in addition to the above-mentioned acetal derivatives and ester derivatives. For example, the above-mentioned hydrogenated acetaldehyde trimer is thought to potentially correspond to any of the color-causing substances, odor-causing substances, and acidity-causing substances.

[0014] It is difficult to completely remove the above-mentioned by-products even by using conventional purification methods such as distillation. This is thought to be because new by-products are produced when crude 1,3-butylene glycol is subjected to high-temperature conditions or alkali treatment during the purification stage of crude 1,3-butylene glycol. For these reasons, as mentioned above, the 1,3-butylene glycol products of Patent Documents 1 to 6 contain a wide variety of by-products, and therefore have an odor, become discolored over time, and furthermore, when they contain water, the acid concentration increases over time.

[0015] Therefore, an object of the present disclosure is to provide a high-purity 1,3-butylene glycol product that is colorless and odorless (or nearly colorless and odorless) and is unlikely to develop or increase coloration or odor over time, and / or is unlikely to experience an increase in acid concentration over time even when containing water. Another object of the present disclosure is to provide a moisturizing agent and a cosmetic that have excellent moisturizing performance and can maintain high quality for a long period of time. [Means for solving the problem]

[0016] The inventors of the present disclosure conducted extensive research to achieve the above-mentioned objectives and found that, when 1,3-butylene glycol products are stored for a long period of time, their quality deteriorates over time, including increased color and odor, and decreases in their initial boiling point, dry point, and potassium permanganate test values. They also found that the content of certain chemicals in 1,3-butylene glycol products increases over time. They then subjected 1,3-butylene glycol products to a heating test (accelerated test) under specific conditions and examined the correlation between the content of the specific chemicals in the samples after the test and the deterioration over time in the product's quality (color, odor, initial boiling point, dry point, potassium permanganate test value, acid concentration, etc.). They found a clear correlation between the two. Furthermore, they also considered the pathways by which the specific chemicals are produced and discovered a method for preventing the incorporation of the specific chemicals and their precursors into 1,3-butylene glycol products. More specifically, they found that by adjusting the distillation conditions (such as the content of specific impurities in the feed liquid and the reflux ratio) of the product column, high-boiling stripping column, and dehydration column, and further by adjusting the reaction conditions in the reaction step (for example, the hydrogenation step of acetaldols) (particularly by increasing the hydrogen partial pressure in the reactor), it is possible to suppress the incorporation of the specific chemical substances and their precursors into the 1,3-butylene glycol product, and to obtain 1,3-butylene glycol that is colorless and odorless (or almost colorless and odorless), is unlikely to develop or increase in coloration or odor over time, and is unlikely to experience an increase in acid concentration over time even when containing water. The invention according to the present disclosure was completed based on these findings and through further investigation.

[0017] That is, the present disclosure provides a 1,3-butylene glycol product containing 1,3-butylene glycol, which is represented by the following formula (A) or (B) after being kept at 180°C for 3 hours in an air atmosphere: [ka] (In the formula, R 1 ~R 4are the same or different and are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be substituted with a hydroxyl group, or an alkenyl group having 2 to 4 carbon atoms which may be substituted with a hydroxyl group. The present invention provides a 1,3-butylene glycol product in which the content of at least one of the compounds represented by the formula (I) is less than 8 ppm.

[0018] In the 1,3-butylene glycol product, the total content of the compound represented by formula (A) after being kept in an air atmosphere at 180° C. for 3 hours is preferably less than 66 ppm.

[0019] Furthermore, it is preferable that the total content of the compound represented by formula (B) after being kept at 180° C. for 3 hours in an air atmosphere is less than 31 ppm.

[0020] The compound represented by (A) is, for example, any of the compounds represented by the following formulas (1) to (7), and the compound represented by (B) is, for example, any of the compounds represented by the following formulas (8) to (10). [ka]

[0021] In this case, it is preferable that the total content of the compounds represented by the formulas (1) to (4) after being kept in an air atmosphere at 180° C. for 3 hours is less than 34 ppm.

[0022] Furthermore, it is preferable that the total content of the compounds represented by the formulas (5) to (10) after being kept at 180° C. for 3 hours in an air atmosphere is less than 63 ppm.

[0023] Furthermore, it is preferable that the total content of the compounds represented by the formulas (1) to (10) after being kept at 180° C. for 3 hours in an air atmosphere is less than 97 ppm.

[0024] In the 1,3-butylene glycol product, after being kept in an air atmosphere at 180°C for 3 hours, it is preferred that the methyl vinyl ketone content is less than 8 ppm, and / or the 1-hydroxy-3-butanone content is less than 1 ppm, and / or the acetone content is less than 6 ppm, and / or the formaldehyde content is less than 2 ppm, and / or the crotonaldehyde content is less than 1 ppm, and / or the acetaldol content is less than 1 ppm, and / or the acetaldehyde content is less than 5 ppm, and / or the butyraldehyde content is less than 4 ppm.

[0025] Furthermore, after being kept at 180°C for 3 hours in an air atmosphere, the total content of methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol and acetaldehyde is preferably less than 24 ppm.

[0026] Furthermore, after being kept at 180° C. for 3 hours in an air atmosphere, the total content of methyl vinyl ketone, acetone and butyraldehyde is preferably less than 18 ppm.

[0027] Furthermore, it is preferable that the APHA is less than 79 after being kept at 180°C for 3 hours in an air atmosphere.

[0028] Furthermore, after being kept at 180°C for 3 hours in an air atmosphere, it is preferable that the initial boiling point is higher than 203°C and / or the dry point is 209°C or lower.

[0029] Furthermore, it is preferable that the potassium permanganate test value after being kept at 180°C for 3 hours in an air atmosphere is 30 minutes or more.

[0030] Furthermore, it is preferable that the acid concentration (as acetic acid) after being kept at 180° C. for 3 hours in an air atmosphere is less than 16 ppm.

[0031] Furthermore, it is preferable that the total content of 1-hydroxy-3-butanone and acetaldol is less than 19 ppm in a state that has not undergone a test in which the mixture is kept at 180°C for 3 hours in an air atmosphere.

[0032] Furthermore, without undergoing a test in which the mixture is kept at 180°C for 3 hours in an air atmosphere, it is preferable that the methyl vinyl ketone content is less than 10 ppm, and / or the 1-hydroxy-3-butanone content is less than 9 ppm, and / or the acetone content is less than 9 ppm, and / or the formaldehyde content is less than 3 ppm, and / or the crotonaldehyde content is less than 2 ppm, and / or the acetaldol content is less than 10 ppm, and / or the acetaldehyde content is less than 4 ppm, and / or the butyraldehyde content is less than 8 ppm.

[0033] Furthermore, it is preferable that the total content of methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, and acetaldehyde is less than 47 ppm when not subjected to a test of holding the material at 180°C for 3 hours in an air atmosphere.

[0034] The present disclosure also provides a moisturizer comprising the 1,3-butylene glycol product.

[0035] Furthermore, the present disclosure provides a cosmetic comprising the moisturizing agent.

[0036] In the present disclosure, "1,3-butylene glycol product" refers to a composition in which 1,3-butylene glycol accounts for the majority of the constituent components (for example, the 1,3-butylene glycol content is 95% by weight or more, preferably 98% by weight or more). [Effects of the Invention]

[0037] According to the present disclosure, there is provided a high-purity 1,3-butylene glycol product that is colorless and odorless (or nearly colorless and odorless) and is unlikely to develop or increase coloration or odor over time, and / or is unlikely to experience an increase in acid concentration over time even when containing water. Furthermore, the present disclosure provides moisturizing agents and cosmetics that have excellent moisturizing performance and can maintain high quality for a long period of time. [Brief explanation of the drawings]

[0038] [Figure 1] 1 is a flowchart illustrating an example of a manufacturing method (purification method) for producing a 1,3-butylene glycol product according to the present disclosure. [Figure 2] 1 is a chart of a gas chromatography analysis of a 1,3-butylene glycol product in Example 1. [Figure 3] 1 is a chart showing the gas chromatography analysis of the 1,3-butylene glycol product in Example 12. [Figure 4] 1 is a chart of a gas chromatography analysis of a 1,3-butylene glycol product in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0039] [1,3-butylene glycol products] The 1,3-butylene glycol product according to the present disclosure is a 1,3-butylene glycol product containing 1,3-butylene glycol, which has a structure represented by the following formula (A) or (B) after being kept at 180°C for 3 hours in an air atmosphere: [ka] (In the formula, R 1 ~R 4 are the same or different and are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be substituted with a hydroxyl group, or an alkenyl group having 2 to 4 carbon atoms which may be substituted with a hydroxyl group. The content of at least one of the compounds represented by the formula (A) is less than 8 ppm. The compound represented by formula (A) is a cyclic acetal compound, and the compound represented by formula (B) is a carboxylic acid 3-hydroxybutyl ester compound. These compounds are present as impurities during the production of 1,3-butylene glycol, but their content increases over time when the 1,3-butylene glycol product is stored for a long period of time. The compound represented by formula (A) hydrolyzes in the presence of moisture to produce the corresponding carbonyl compound. The carbonyl compound thus produced is not only a reducing substance that reduces the potassium permanganate test value, but is also highly reactive and easily produces various complex compounds in the presence of heat or oxygen, which can become color-causing substances, odor-causing substances, or acidic substances. Furthermore, the compound represented by formula (B) hydrolyzes in the presence of moisture to produce the corresponding carboxylic acid. The carboxylic acid thus produced can become an odor-causing substance or acidic substance.

[0040] In the formulas (A) and (B), R 1 ~R 4 are the same or different and are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be substituted with a hydroxyl group, or an alkenyl group having 2 to 4 carbon atoms which may have a hydroxyl group. Examples of the alkyl group having 1 to 4 carbon atoms which may be substituted with a hydroxyl group include methyl, ethyl, propyl, butyl, 2-hydroxyethyl, and 2-hydroxypropyl groups. Examples of the alkenyl group having 2 to 4 carbon atoms which may be substituted with a hydroxyl group include vinyl and 1-propenyl groups. R 1 Examples of R include a hydrogen atom and a methyl group. 2 Examples of R include a hydrogen atom, methyl, vinyl, 2-hydroxyethyl, 2-hydroxypropyl, 1-propenyl, and butyl groups. 3 Examples of R include a methyl group. 4 Examples of the aryl group include a hydrogen atom, methyl, 2-hydroxypropyl, and 1-propenyl groups.

[0041] Representative examples of the compound represented by formula (A) include compounds represented by the following formulas (1) to (7): Representative examples of the compound represented by formula (B) include compounds represented by the following formulas (8) to (10): [ka]

[0042] The content of each compound represented by formula (A) or (B) [e.g., compounds represented by formulas (1) to (10)] can be quantified by GC-MS analysis under the following conditions. In GC-MS analysis, even very small peaks are all subjected to mass spectrometry to quantify each component. Because analysis is performed for specific masses, substances with different masses will not be detected even if other impurities overlap the peak, resulting in higher sensitivity than the GC analysis described below. In this specification, the unit "ppm" used to determine the content of each component [the content of each compound represented by formula (A) or (B)] in GC-MS analysis means "ppm by weight." (GC-MS analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Ion source temperature: EI 230℃, CI 250℃ Q pole temperature: 150℃ Sample: Ready for analysis

[0043] Under the above analytical conditions, the retention time of the peak of 1,3-butylene glycol is usually 5.5 to 7 minutes. Under the above analytical conditions, when the relative retention time of the peak of 1,3-butylene glycol is taken as 1.0, typically, the relative retention time of the peak of the compound represented by formula (1) is 1.3 to 1.7, the relative retention time of the peak of the compound represented by formula (2) is 1.6 to 2.0, the relative retention time of the peak of the compound represented by formula (3) is 0.7 to 1.0, the relative retention time of the peak of the compound represented by formula (4) is 0.4 to 0.6, the relative retention time of the peak of the compound represented by formula (5) is 1.3 to 1.7, the relative retention time of the peak of the compound represented by formula (6) is 1.6 to 2.0, the relative retention time of the peak of the compound represented by formula (7) is 0.6 to 0.8, the relative retention time of the peak of the compound represented by formula (8) is 1.6 to 2.0, the relative retention time of the peak of the compound represented by formula (9) is 1.0 to 1.2, and the relative retention time of the peak of the compound represented by formula (10) is 1.6 to 2.0.

[0044] The compound represented by the formula (1) is a compound produced by the reaction (acetalization reaction) of methyl vinyl ketone and 1,3-butylene glycol. Methyl vinyl ketone is produced by the dehydration reaction of 1-hydroxy-3-butanone. 1-Hydroxy-3-butanone is produced by the oxidation of 1,3-butylene glycol. The compound represented by the formula (2) is a compound produced by the reaction (acetalization reaction) of 1-hydroxy-3-butanone and 1,3-butylene glycol. The compound represented by the formula (3) is a compound produced by the reaction (acetalization reaction) of acetone and 1,3-butylene glycol. The compound represented by the formula (4) is a compound produced by the reaction (acetalization reaction) of formaldehyde and 1,3-butylene glycol. Acetone and formaldehyde are produced by the decomposition of 1-hydroxy-3-butanone. The compound represented by the formula (5) is a compound produced by the reaction of crotonaldehyde with 1,3-butylene glycol (acetalization reaction). Crotonaldehyde is produced by the dehydration reaction of acetaldol. Acetaldol is produced by the oxidation of 1,3-butylene glycol. Acetaldol can also be produced by the dimerization of acetaldehyde. The compound represented by the formula (6) is a compound produced by the reaction of acetaldol with 1,3-butylene glycol (acetalization reaction). The compound represented by the formula (7) is a compound produced by the reaction of acetaldehyde with 1,3-butylene glycol (acetalization reaction). Acetaldehyde is produced by the decomposition of acetaldol. The compound represented by the formula (8) is a compound produced by the reaction of crotonic acid with 1,3-butylene glycol (esterification reaction). Crotonic acid is produced by the oxidation of crotonaldehyde. The compound represented by the formula (9) is a compound produced by the reaction (esterification reaction) of acetic acid with 1,3-butylene glycol. Acetic acid is produced by the oxidation of acetaldehyde. The compound represented by the formula (10) is a compound produced by the reaction (esterification reaction) of 3-hydroxybutanoic acid with 1,3-butylene glycol. 3-Hydroxybutanoic acid is produced by the oxidation of acetaldol.In addition, formic acid is produced by oxidation of formaldehyde, and this formic acid reacts with 1,3-butylene glycol (esterification reaction) to produce 2-hydroxypropyl formate. 2-Butanol is then produced by decarboxylation of 2-hydroxypropyl formate. The estimated production pathways for each compound (impurity) (sometimes referred to as "impurity production pathway diagrams") are shown below. In the formula below, "1,3BG" represents 1,3-butylene glycol.

[0045] [ka]

[0046] The 1,3-butylene glycol product according to the present disclosure has a content of at least one of the compounds represented by formula (A) or (B) [e.g., compounds represented by formulas (1) to (10)] of less than 8 ppm (e.g., 7 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, and even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after being kept at 180°C for 3 hours in an air atmosphere. Therefore, among the contents of the compounds represented by formula (A) or (B) [for example, compounds represented by formulas (1) to (10)], the content of one compound may be less than 8 ppm (for example, 7 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and the contents of two compounds (or three compounds, four compounds, five compounds, six compounds, seven compounds, eight compounds, nine compounds, ten compounds, etc.) may each be less than 8 ppm (for example, 7 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0047] In the 1,3-butylene glycol product according to the present disclosure, after being kept at 180°C for 3 hours in an air atmosphere, it is preferable that the content of at least four (4, 5, 6, 7, 8, 9, or 10) compounds among the compounds represented by formula (A) or (B) [e.g., compounds represented by formulas (1) to (10)] is less than 8 ppm (e.g., 7 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm). In particular, it is preferred that the contents of all of the compounds represented by the formulas (1) to (10) are less than 8 ppm (for example, 7 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, and even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0048] In the 1,3-butylene glycol product according to the present disclosure, among the contents of the compounds represented by formula (A) or (B) [e.g., compounds represented by formulas (1) to (10)] after being kept at 180°C for 3 hours in an air atmosphere, at least one (e.g., 1, 2, 3, 4, ..., or 10) of the sum of the contents of the two compounds may be less than 16 ppm (e.g., 15 ppm or less, preferably 14 ppm or less, more preferably 13 ppm or less, even more preferably 12 ppm or less, particularly preferably 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0049] In the 1,3-butylene glycol product according to the present disclosure, after being kept at 180°C for 3 hours in an air atmosphere, the sum of the contents of the compounds represented by formula (A) or (B) [e.g., compounds represented by formulas (1) to (10)] may be such that at least one (e.g., 1, 2, 3, 4, ...) of the three contents is less than 24 ppm (e.g., 20 ppm or less, preferably 18 ppm or less, more preferably 16 ppm or less, even more preferably 14 ppm or less, particularly preferably 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0050] In the 1,3-butylene glycol product according to the present disclosure, after being kept at 180°C for 3 hours in an air atmosphere, the sum of the contents of the compounds represented by formula (A) or (B) [e.g., compounds represented by formulas (1) to (10)] may be such that at least one (e.g., one, two, ...) of the four contents is less than 32 ppm (e.g., 30 ppm or less, preferably 25 ppm or less, more preferably 20 ppm or less, even more preferably 18 ppm or less, particularly preferably 16 ppm or less, 14 ppm or less, 12 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0051] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a total content of the compounds represented by formula (A), in particular, the total content of the compounds represented by formulas (1) to (7), after being kept in an air atmosphere at 180°C for 3 hours, of less than 66 ppm (for example, 60 ppm or less, preferably 50 ppm or less, more preferably 40 ppm or less, even more preferably 30 ppm or less, particularly preferably 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0052] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a total content of the compounds represented by formula (B), in particular, the total content of the compounds represented by formulas (8) to (10), after being kept in an air atmosphere at 180°C for 3 hours, of less than 31 ppm (for example, 25 ppm or less, preferably 20 ppm or less, more preferably 18 ppm or less, even more preferably 16 ppm or less, particularly preferably 14 ppm or less, 13 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0053] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a total content of the compounds represented by the formulas (1) to (4) of less than 34 ppm (for example, 30 ppm or less, preferably 25 ppm or less, more preferably 20 ppm or less, even more preferably 18 ppm or less, and particularly preferably 16 ppm or less, 15 ppm or less, 14 ppm or less, 13 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after being kept in an air atmosphere at 180°C for 3 hours.

[0054] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a total content of compounds represented by the formulas (5) to (10) of less than 63 ppm (for example, 60 ppm or less, preferably 50 ppm or less, more preferably 40 ppm or less, even more preferably 30 ppm or less, and particularly preferably 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after being kept in an air atmosphere at 180°C for 3 hours.

[0055] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a total content of compounds represented by the formulas (1) to (10) of less than 97 ppm (for example, 80 ppm or less, preferably 70 ppm or less, more preferably 60 ppm or less, even more preferably 50 ppm or less, and particularly preferably 40 ppm or less, 30 ppm or less, 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after being kept in an air atmosphere at 180°C for 3 hours.

[0056] As shown in the impurity generation pathway diagram, methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, and acetaldehyde are precursors of the compounds represented by formula (A) or (B). Butyraldehyde, due to its structure, can also be a precursor of the compound represented by formula (A). Additionally, these compounds are carbonyl compounds that are prone to generating various complex compounds under heat or oxygen, which can become discoloring, odor-causing, or acidic substances. Therefore, it is desirable for 1,3-butylene glycol products to have a low content of these compounds after being stored at 180°C for 3 hours in an air atmosphere.For example, after being kept at 180°C for 3 hours in an air atmosphere, the 1,3-butylene glycol product of the present disclosure has a methyl vinyl ketone content of less than 8 ppm (e.g., 7 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or a 1-hydroxy-3-butanone content of less than 1 ppm (preferably 0.5 ppm or less), and / or an acetone content of less than 6 ppm (e.g., 5 ppm or less, preferably 4 ppm or less, more preferably 3 ppm or less, even more preferably 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or a formaldehyde content of less than 2 ppm (preferably 1 ppm or less, more preferably Preferably, the content of crotonaldehyde is less than 1 ppm (preferably 0.5 ppm or less), and / or the content of acetaldol is less than 1 ppm (preferably 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the content of acetaldehyde is less than 5 ppm (for example, 4 ppm or less, preferably 3 ppm or less, more preferably 2 ppm or less, even more preferably 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the content of butyraldehyde is less than 4 ppm (for example, 3 ppm or less, preferably 2 ppm or less, more preferably 1 ppm or less, even more preferably 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0057] The contents of methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, acetaldehyde, and butyraldehyde in 1,3-butylene glycol products can be quantified by GC-MS analysis (gas mass spectrometry) under the above conditions. Under the above analytical conditions, when the relative retention time of the peak of 1,3-butylene glycol is taken as 1.0, the relative retention time of the peak of methyl vinyl ketone is usually 0.3 to 0.5, the relative retention time of the peak of 1-hydroxy-3-butanone is 0.4 to 0.6, the relative retention time of the peak of acetone is 0.3 to 0.5, the relative retention time of the peak of formaldehyde is 0.3 to 0.5, the relative retention time of the peak of crotonaldehyde is 0.3 to 0.5, the relative retention time of the peak of acetaldol is 0.4 to 0.6, the relative retention time of the peak of acetaldehyde is 0.3 to 0.5, and the relative retention time of the peak of butyraldehyde is 0.3 to 0.5.

[0058] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a total content of methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, and acetaldehyde of less than 24 ppm (e.g., 20 ppm or less, preferably 18 ppm or less, more preferably 16 ppm or less, even more preferably 14 ppm or less, particularly preferably 12 ppm or less, 11 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after being kept in an air atmosphere at 180°C for 3 hours.

[0059] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a total content of methyl vinyl ketone, acetone, and butylaldehyde of less than 18 ppm (e.g., 16 ppm or less, preferably 15 ppm or less, more preferably 14 ppm or less, even more preferably 13 ppm or less, particularly preferably 12 ppm or less, 11 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after being kept in an air atmosphere at 180°C for 3 hours. Methyl vinyl ketone, acetone, and butylaldehyde are impurities present in relatively large amounts in the 1,3-butylene glycol product after the heating test.

[0060] Furthermore, the 1,3-butylene glycol product according to the present disclosure desirably has an APHA of less than 79 (preferably 65 or less, more preferably 60 or less, even more preferably 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, 25 or less, 20 or less, and particularly preferably 18 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9 or less, 8 or less, or 7 or less) after being kept at 180°C for 3 hours in an air atmosphere.

[0061] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has an initial boiling point of higher than 203°C and a dry point of not higher than 209°C after being kept at 180°C in an air atmosphere for 3 hours. The initial boiling point is preferably 204°C or higher, more preferably 205°C or higher, even more preferably 206°C or higher or 207°C or higher, and particularly preferably 208°C or higher.

[0062] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a potassium permanganate test value (PMT) of 30 minutes or more after being kept in an air atmosphere at 180°C for 3 hours. The potassium permanganate test value is more preferably more than 30 minutes (e.g., 32 minutes or more), even more preferably 35 minutes or more (e.g., 40 minutes or more), and particularly preferably 50 minutes or more (particularly 60 minutes or more).

[0063] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has an acid concentration (as acetic acid) of less than 16 ppm after being kept in an air atmosphere at 180° C. for 3 hours. The acid concentration (as acetic acid) is more preferably 14 ppm or less, and even more preferably 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm.

[0064] As mentioned above, methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, acetaldehyde, and butyraldehyde are precursors of the compounds represented by formula (A) or (B). In particular, 1-hydroxy-3-butanone and acetaldol are precursors of various impurities. Therefore, it is desirable that the amount of these impurities in the 1,3-butylene glycol product be as low as possible before the heating test. From this perspective, it is preferable that the 1,3-butylene glycol product according to the present disclosure, when not subjected to a test of holding the product in an air atmosphere at 180°C for 3 hours (before the heating test), has a total content of 1-hydroxy-3-butanone and acetaldol of less than 19 ppm (for example, 18 ppm or less, preferably 16 ppm or less, more preferably 14 ppm or less, even more preferably 12 ppm or less, and particularly preferably 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0065] Furthermore, the 1,3-butylene glycol product according to the present disclosure has a methyl vinyl ketone content of less than 10 ppm (for example, 8 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, and even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) and / or a 1-hydroxy-3-butanone content of less than 10 ppm (for example, 8 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, and even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) in a state that has not undergone a test of being held at 180°C for 3 hours in an air atmosphere (before the heating test). less than 9 ppm (e.g., 7 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the acetone content is less than 9 ppm (e.g., 7 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, or less than 0.2 ppm). m or less, 0.3 ppm or less, or less than 0.2 ppm), and / or a formaldehyde content of less than 3 ppm (e.g., 2 ppm or less, preferably 1 ppm or less, more preferably 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or a crotonaldehyde content of less than 2 ppm (e.g., 1.5 ppm or less, preferably 1 ppm or less, more preferably 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or an acetaldehyde content of The alcohol content is less than 10 ppm (e.g., 8 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the acetaldehyde content is less than 4 ppm (e.g., 3 ppm or less, preferably 2 ppm or less, more preferably 1 ppm or less, even more preferably 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).It is preferred that the butyraldehyde content is less than 8 ppm (for example, 7 ppm or less, preferably 6 ppm or less, more preferably 5 ppm or less, and even more preferably 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0066] Furthermore, in the 1,3-butylene glycol product according to the present disclosure, before undergoing a test of holding the product in an air atmosphere at 180°C for 3 hours (before the heating test), the total content of methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, and acetaldehyde is preferably less than 47 ppm (for example, 40 ppm or less, preferably 30 ppm or less, more preferably 25 ppm or less, even more preferably 20 ppm or less, particularly preferably 18 ppm or less, 16 ppm or less, 14 ppm or less, 13 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[0067] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has an acid concentration (as acetic acid) of less than 11 ppm (e.g., 10 ppm or less, preferably 9 ppm or less, more preferably 8 ppm or less, even more preferably 7 ppm or less, particularly preferably 6 ppm or less, and most preferably 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) in a state that has not undergone a test in which the product is kept in an air atmosphere at 180°C for 3 hours (before the heating test). By lowering the acid concentration in the 1,3-butylene glycol product, the increase over time of the impurity represented by formula (B) can be suppressed.

[0068] The 1,3-butylene glycol product according to the present disclosure, in a state that has not undergone a test of holding at 180°C for 3 hours in an air atmosphere (before the heating test), preferably has an acid concentration (as acetic acid) of less than 23 ppm (for example, 20 ppm or less, preferably 19 ppm or less, 18 ppm or less, 17 ppm or less, or 16 ppm or less, more preferably 15 ppm or less, even more preferably 14 ppm or less, 13 ppm or less, 12 ppm or less, or 11 ppm or less, and particularly preferably 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after a 90 wt % aqueous solution thereof is held at 100°C for 1 week. The 90 wt% aqueous solution refers to an aqueous solution prepared by mixing a 1,3-butylene glycol product with water (e.g., purified water) and adjusting the concentration of the 1,3-butylene glycol product to 90 wt%. By lowering the concentration of the acid precursor in the 1,3-butylene glycol product, it is possible to suppress the increase over time of the impurity represented by the formula (B).

[0069] In the 1,3-butylene glycol product according to the present disclosure, in a state that has not undergone a test of holding the product in an air atmosphere at 180°C for 3 hours (before the heating test), the ratio of the acid concentration (as acetic acid) of a 90 wt % aqueous solution after holding the product at 100°C for 1 week to the acid concentration before holding [(acid concentration after holding at 100°C for 1 week) / (acid concentration before holding)×100(%)] is preferably 200% or less, more preferably 150% or less, and even more preferably 120% or less.

[0070] The 1,3-butylene glycol product according to the present disclosure has an APHA (Hazen color scale) of, for example, 6 or less (preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less) before undergoing a test of holding the product in an air atmosphere at 180°C for 3 hours (before the heating test). Furthermore, the APHA of the 1,3-butylene glycol product after holding the product in an air atmosphere at 100°C for 75 days is, for example, 42 or less (preferably 35 or less, 30 or less, 25 or less, 20 or less, 18 or less, 16 or less, 15 or less, 14 or less, or 13 or less, more preferably 12 or less, 11 or less, 10 or less, 9 or less, 8 or less, 7 or less, or 6 or less, and even more preferably 5 or less, 4 or less, 3 or less, or 2 or less).

[0071] With regard to the APHA of the 1,3-butylene glycol product according to the present disclosure, the ratio of the APHA after 75 days at 100°C to the APHA before the holding [(APHA after 75 days at 100°C) / (APHA before the holding)] is not particularly limited, but is preferably 10 or less, more preferably 8 or less, even more preferably 7 or less, and particularly preferably 6 or less (for example, 5 or less, 4 or less, or 3 or less). The ratio may be 1 or more, and may be 2 or more.

[0072] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has an initial boiling point of higher than 203°C in a state that has not undergone a test in which the product is held at 180°C for 3 hours in an air atmosphere (before the heating test). The initial boiling point is preferably 204°C or higher, more preferably 205°C or higher, even more preferably 206°C or higher or 207°C or higher, and particularly preferably 208°C or higher.

[0073] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a dry point of 209°C or lower in a state that has not undergone a test in which it is held at 180°C for 3 hours in an air atmosphere (before the heating test).

[0074] Furthermore, the 1,3-butylene glycol product according to the present disclosure preferably has a potassium permanganate test value (PMT) of 30 minutes or more in a state (before the heating test) in which it is held in an air atmosphere at 180°C for 3 hours. The potassium permanganate test value (PMT) is more preferably more than 30 minutes (e.g., 32 minutes or more), even more preferably 35 minutes or more (e.g., 40 minutes or more), and particularly preferably 50 minutes or more (particularly 60 minutes or more).

[0075] In the 1,3-butylene glycol product according to the present disclosure, the 1,3-butylene glycol content is, for example, 98.6% or more. The 1,3-butylene glycol content is expressed as the area ratio (GC area ratio) of the 1,3-butylene glycol peak in gas chromatography analysis (GC analysis) under the following conditions: (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[0076] In this disclosure, the "area ratio" of a peak refers to the ratio of the area of ​​a specific peak to the sum of the areas of all peaks appearing in a chart. Furthermore, "all peaks" refers to, for example, all peaks that appear when the relative retention time of the 1,3-butylene glycol peak is set to 1.0 and the analysis is continued until the relative retention time reaches 7.8 and then stopped. By ensuring that the 1,3-butylene glycol content in a 1,3-butylene glycol product is, for example, 98.6% or more, the basic properties inherent to 1,3-butylene glycol are ensured.

[0077] The 1,3-butylene glycol content (GC area ratio) is preferably 98.7% or more, more preferably 98.8% or more, even more preferably 98.9% or more, and particularly preferably 99.0% or more. The 1,3-butylene glycol content (GC area ratio) is particularly preferably 99.1% or more, 99.2% or more, 99.3% or more, 99.4% or more, 99.5% or more, 99.6% or more, 99.7% or more, or 99.8% or more.

[0078] In the GC analysis, the total area ratio of peaks having shorter retention times than the peak of 1,3-butylene glycol is preferably 0.28% or less, more preferably 0.25% or less, even more preferably 0.23% or less, 0.2% or less, 0.17% or less, 0.15% or less, 0.12% or less, 0.1% or less, 0.07% or less, 0.04% or less, 0.03% or less, 0.02% or less, 0.01% or less, or 0.007% or less, and particularly preferably 0.005% or less (e.g., 0.002% or less).

[0079] In the GC analysis, the total area ratio of peaks having a longer retention time than the peak of 1,3-butylene glycol is preferably 1% or less, more preferably 0.9% or less, even more preferably 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or 0.2% or less, and particularly preferably 0.1% or less.

[0080] In the 1,3-butylene glycol product according to the present disclosure, the water content is preferably less than 0.4% by weight. The water content is preferably 0.3% by weight or less, more preferably 0.2% by weight or less, even more preferably 0.1% by weight or less, 0.07% by weight or less, 0.05% by weight or less, 0.03% by weight or less, 0.02% by weight or less, or 0.01% by weight or less, and particularly preferably 0.005% by weight or less. The water content can be quantified using a Karl Fischer moisture analyzer.

[0081] A 1,3-butylene glycol product having a 1,3-butylene glycol content equal to or greater than a specific value and having a content of a specific substance equal to or less than a specific value after a heating test under the above-mentioned specific conditions is highly pure and high quality, and exhibits little deterioration in quality over time, making it suitable for use as a raw material for moisturizers and cosmetics.

[0082] [Moisturizers and cosmetics] The moisturizing agent of the present disclosure contains the 1,3-butylene glycol product described above. Therefore, it has excellent moisturizing performance. The moisturizing agent of the present disclosure may contain components other than the 1,3-butylene glycol product described above, for example, moisturizing agent components other than the 1,3-butylene glycol product described above. The moisturizing agent of the present disclosure may contain, for example, 10% by weight or more of the 1,3-butylene glycol product, preferably 30% by weight or more, more preferably 50% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more. The moisturizing agent may be composed solely of the 1,3-butylene glycol product described above.

[0083] The cosmetic preparation of the present disclosure contains the moisturizing agent described above. The amount of the 1,3-butylene glycol product in the cosmetic preparation of the present disclosure may be any amount that can exhibit moisturizing properties, depending on the type and form of the cosmetic. The amount of the 1,3-butylene glycol product in the cosmetic preparation of the present disclosure is, for example, 0.01 to 40 wt %, preferably 0.1 to 30 wt %, more preferably 0.2 to 20 wt %, even more preferably 0.5 to 15 wt %, and particularly preferably 1 to 10 wt %.

[0084] In addition to the 1,3-butylene glycol product, the cosmetic composition of the present disclosure may contain, for example, other moisturizers; oils such as vegetable oils, hydrocarbon oils, higher fatty acids, higher alcohols, and silicones; surfactants such as anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants; preservatives, sequestering agents, thickeners, powders, UV absorbers, UV blockers, fragrances, pH adjusters; medicinal ingredients and physiologically active ingredients such as vitamins, skin activators, blood circulation promoters, whitening agents, antibacterial agents, and anti-inflammatory agents.

[0085] The cosmetic of the present disclosure may be a skin cosmetic such as a lotion, emulsion, cream, gel, pack, or mask, or a hair cosmetic such as a shampoo, rinse, or hair growth agent. It may also be a sunscreen cosmetic, a makeup cosmetic, or the like. It may also be a pharmaceutical or quasi-drug containing a medical ingredient.

[0086] The cosmetic composition of the present disclosure can be produced by utilizing a method known per se.

[0087] [Method of producing 1,3-butylene glycol] The 1,3-butylene glycol product of the present disclosure can be produced, for example, by the following 1,3-butylene glycol production method 1 or the following 1,3-butylene glycol production method 2.

[0088] Method 1 for producing 1,3-butylene glycol: A method for producing 1,3-butylene glycol, in which purified 1,3-butylene glycol is obtained from a reaction crude liquid containing 1,3-butylene glycol, comprising the steps of: The process includes a dehydration process for removing water by distillation, a high boiling point removal process for removing high boiling point components by distillation, and a product distillation process for obtaining purified 1,3-butylene glycol. A method for producing 1,3-butylene glycol, in which a 1,3-butylene glycol feed solution having an acetaldehyde content of 500 ppm or less, a crotonaldehyde content of 200 ppm or less, a water content of 0.7 wt% or less, and a 1,3-butylene glycol concentration of 97.6 area % or more as determined by gas chromatography analysis under the following conditions is subjected to distillation in a product column used in the product distillation step, at a reflux ratio of 0.3 or more. (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[0089] Method 2 for producing 1,3-butylene glycol: A method for producing 1,3-butylene glycol, in which purified 1,3-butylene glycol is obtained from a reaction crude liquid containing 1,3-butylene glycol, comprising the steps of: The method includes a dehydration step for removing water by distillation and a high boiling point removal step for removing high boiling point components by distillation, A method for producing 1,3-butylene glycol, in which a feed liquid containing 1,3-butylene glycol having an acetaldehyde content of 500 ppm or less, a crotonaldehyde content of 200 ppm or less, a water content of 3% by weight or less, and a 1,3-butylene glycol concentration of 96.7 area % or more as determined by gas chromatography analysis under the following conditions is subjected to distillation in a high boiling removal tower used in the high boiling removal step, at a reflux ratio of 0.03 or more. (Gas chromatographic analysis conditions) Same as the above-mentioned Production Method 1 of 1,3-butylene glycol.

[0090] The above-mentioned 1,3-butylene glycol production method 1 (hereinafter may be simply referred to as "production method 1") is a production method for 1,3-butylene glycol in which purified 1,3-butylene glycol is obtained from a crude reaction liquid containing 1,3-butylene glycol (1,3BG) (hereinafter may be referred to as "crude 1,3-butylene glycol"), and includes a dehydration step in which water is removed by distillation, a high-boiling point removal step in which high-boiling point components are removed by distillation, and a product distillation step in which purified 1,3-butylene glycol is obtained. In the product column used in the product distillation step, a 1,3-butylene glycol feed solution having an acetaldehyde content of 500 ppm or less, a crotonaldehyde content of 200 ppm or less, a water content of 0.7 wt% or less, and a 1,3-butylene glycol concentration of 97.6 area% or more as determined by gas chromatography analysis under the above conditions is subjected to distillation under conditions of a reflux ratio of 0.3 or more, a liquid concentrated with low boiling point components is distilled from above the feed stage, and 1,3-butylene glycol is extracted from below the feed stage. The 1,3-butylene glycol thus obtained is colorless and odorless (or nearly colorless and odorless), does not easily become discolored over time, and is also not susceptible to an increase in acid concentration over time even when containing water, making it suitable for use as a 1,3-butylene glycol product.

[0091] The above-mentioned 1,3-butylene glycol production method 2 (hereinafter sometimes simply referred to as "production method 2") is a method for producing 1,3-butylene glycol from a reaction crude liquid containing 1,3-butylene glycol, and includes a dehydration step for removing water by distillation and a high-boiling component removal step for removing high-boiling components by distillation. In the high-boiling component removal tower used in the high-boiling component removal step, a feed liquid containing 1,3-butylene glycol having an acetaldehyde content of 500 ppm or less, a crotonaldehyde content of 200 ppm or less, a water content of 3 wt% or less, and a 1,3-butylene glycol concentration of 96.7 area % or more as determined by gas chromatography analysis under the above conditions is distilled under conditions of a reflux ratio of 0.03 or more, and 1,3-butylene glycol with improved purity is distilled from above the feed stage, and a liquid in which the high-boiling components are concentrated is withdrawn from below the feed stage. The 1,3-butylene glycol obtained in this manner is colorless and odorless (or nearly colorless and odorless), and there is almost no development or increase in coloration over time.Furthermore, even when it contains water, there is little increase in the acid concentration over time, so it can be used as a 1,3-butylene glycol product.

[0092] [Crude 1,3-butylene glycol] Examples of crude 1,3-butylene glycol include (1) a reaction crude liquid obtained by the reduction (hydrogenation) of acetaldols, (2) a reaction crude liquid obtained by the hydrolysis of 1,3-butylene oxide, (3) a reaction crude liquid obtained by the selective hydrogenolysis of erythritol, (4) a reaction crude liquid obtained by the selective addition of water to butadiene, (5) a reaction crude liquid obtained by the hydrogenation of n-butanal-3-one, (6) a reaction crude liquid obtained by the hydrogenation of 1-butanol-3-one, (7) a reaction crude liquid obtained by the hydrogenation of 3-hydroxy-1-butanoic acid, (8) a reaction crude liquid obtained by the hydrogenation of β-butyrolactone, and (9) a reaction crude liquid obtained by the hydrogenation of diketene. In the present disclosure, crude 1,3-butylene glycol may be one or a mixture of two or more of the above (1) to (9). The crude 1,3-butylene glycol is preferably a crude reaction liquid obtained by the reduction (particularly, liquid phase reduction) of acetaldols (1) above.

[0093] Hereinafter, a case where a crude reaction liquid obtained by reduction (hydrogenation) of acetaldols is used as crude 1,3-butylene glycol will be mainly described. The step of reducing (hydrogenating) acetaldols may also be referred to as the "hydrogenation step."

[0094] The acetaldol used as a raw material in the hydrogenation step is not particularly limited as long as it is a compound that can be converted to 1,3-butylene glycol by hydrogen reduction. Examples of the raw material acetaldol include acetaldol, its cyclized dimer, para-aldol, aldoxane, a cyclic trimer of acetaldehyde, and mixtures thereof.

[0095] The method for producing acetaldols (e.g., acetaldol and para-aldol) is not particularly limited, but may be, for example, those obtained by an aldol condensation reaction of acetaldehyde in the presence of a basic catalyst, or those obtained by thermal decomposition of aldoxane, etc. The process for producing acetaldols may be referred to as an "acetaldol production process" or an "acetaldehyde polymerization process."

[0096] The reaction crude liquid containing acetaldols obtained by the above reaction may be neutralized with an acid and used to produce 1,3-butylene glycol. In addition to acetaldols, such a reaction crude liquid may contain acetaldehyde (AD), crotonaldehyde (CR), other aldehyde components, low-boiling substances, high-boiling substances such as aldehyde dimers and trimers, water, salts, etc. In this specification, compounds having a boiling point lower than that of 1,3-butylene glycol may be referred to as "low-boiling substances" or "low-boiling products," and compounds having a boiling point higher than that of 1,3-butylene glycol may be referred to as "high-boiling substances" or "high-boiling products."

[0097] The reaction crude liquid containing the acetaldols may be subjected to pretreatment such as dealcoholization distillation, dehydration distillation, desalting, alkali treatment, dealkalization treatment, and impurity removal, as necessary, to remove by-products such as unreacted acetaldehyde and crotonaldehyde, and may be used after that. Pretreatment methods include distillation, adsorption, ion exchange, heating to convert to high boiling point substances, and decomposition. Various distillation methods can be used for distillation, such as reduced pressure, normal pressure, increased pressure, azeotropy, extraction, and reaction. In particular, it is preferred to subject the reaction crude liquid containing acetaldols to simple evaporation, distillation, or hydrogenation to remove aldehydes such as acetaldehyde and crotonaldehyde, and then subject the resulting product to a hydrogenation step.

[0098] The content of acetaldols in the hydrogenation raw material is not particularly limited, but is, for example, 30% by weight or more (e.g., 30 to 99% by weight), more preferably 40% by weight or more (e.g., 40 to 98% by weight), 50% by weight or more (e.g., 50 to 97% by weight), or 60% by weight or more (e.g., 60 to 95% by weight), even more preferably 65 to 90% by weight, particularly preferably 70 to 90% by weight, and most preferably 75 to 90% by weight. When the content of acetaldols is within the above range, impurities contained in the reaction crude liquid containing 1,3-butylene glycol (crude 1,3-butylene glycol) tend to be reduced.

[0099] The hydrogenation raw material may or may not contain water, but preferably does so from the viewpoint of the purity of the 1,3-butylene glycol product. The water content of the hydrogenation raw material is not particularly limited, but is preferably, for example, 2% by weight or more, more preferably 5% by weight or more, even more preferably 10% by weight or more, and particularly preferably 15% by weight or more. The upper limit may be, for example, 90% by weight, 80% by weight, 70% by weight, 60% by weight, 50% by weight, 40% by weight, 30% by weight, or 20% by weight. When the water content is within the above range, the amount of acetal compounds between 1,3-butylene glycol and acetaldol contained in the obtained crude 1,3-butylene glycol is reduced, and therefore the purity of the finally obtained 1,3-butylene glycol product tends to be higher. This is because the presence of a certain amount of water in the hydrogenation raw material causes the acetal compounds to be hydrolyzed to 1,3-butylene glycol, and the co-produced acetaldol is reduced to 1,3-butylene glycol.

[0100] Examples of hydrogenation catalysts include Raney nickel. The hydrogenation catalyst can be used in a suspended state or packed in a reaction vessel. The amount of hydrogenation catalyst used is not particularly limited, but is preferably 1 to 30 parts by weight, more preferably 4 to 25 parts by weight, even more preferably 8 to 20 parts by weight, and particularly preferably 12 to 18 parts by weight, per 100 parts by weight of the hydrogenation raw material. The amount of hydrogen used in the reduction reaction is not particularly limited, but is preferably 0.5 to 40 parts by weight, more preferably 1 to 30 parts by weight, even more preferably 4 to 20 parts by weight, and particularly preferably 8 to 12 parts by weight, per 100 parts by weight of the hydrogenation raw material. The pressure in the reaction system (total pressure; gauge pressure) in the reduction reaction is not particularly limited, but is, for example, 9 to 70 MPa, preferably 10 to 40 MPa. The hydrogen pressure (hydrogen partial pressure) in the reaction system is not particularly limited, but is, for example, 7 to 60 MPa, preferably 10 to 30 MPa. From the viewpoint of reducing reducing substances such as acetaldehyde and crotonaldehyde, it is advisable to increase the hydrogen pressure in the reaction system, preferably 10 MPa or more, and even 100 MPa. The reaction temperature in the reduction reaction is not particularly limited, but is, for example, 40 to 150°C, preferably 50 to 140°C, and more preferably 60 to 130°C. The reaction time (residence time) in the reduction reaction is not particularly limited, but is, for example, 10 to 500 minutes, preferably 20 to 400 minutes, more preferably 30 to 300 minutes, even more preferably 50 to 280 minutes, and particularly preferably 80 to 250 minutes. This reaction can be carried out in any of a batch system, a semi-batch system, and a continuous system.

[0101] The crude 1,3-butylene glycol thus obtained contains low-boiling substances (low-boiling compounds) having unsaturated bonds, such as acetaldehyde (AD), butylaldehyde, crotonaldehyde (CR), acetone, and methyl vinyl ketone, as well as condensates thereof, condensates of 1,3-butylene glycol with the above-mentioned low-boiling substances (for example, acetals formed from 1,3-butylene glycol and acetaldol), alcohols such as ethanol, isopropyl alcohol, and butanol, water (solvent), salts produced by neutralization treatment, and catalysts (when used in suspension). By removing these impurities in a purification step, a 1,3-butylene glycol product (purified 1,3-butylene glycol) can be obtained.

[0102] [Purification of crude 1,3-butylene glycol] Production method 1 of the present disclosure includes at least a dehydration step of removing water by distillation, a high boiling point removal step of removing high boiling point components by distillation (high boiling point removal distillation step), and a product distillation step for obtaining purified 1,3-butylene glycol. Production method 2 of the present disclosure includes at least a dehydration step of removing water by distillation and a high boiling point removal step of removing high boiling point components by distillation (high boiling point removal distillation step).

[0103] In the production method of the present disclosure, the order of the dehydration step and the high-boiling point removal step does not matter. In Production Method 1, both the dehydration step and the high-boiling point removal step are performed before the product distillation step. In addition to these steps, the production method of the present disclosure may also include a desalting step, an alkali reaction step (alkali treatment step), and a dealkalization step. Furthermore, a catalyst separation step, an alkali neutralization step, and a dealcoholization step (low-boiling point removal step) may also be performed before the dehydration step. The above steps may be performed in the order described above, but the order of the steps may be changed as appropriate, except that the dealcoholization step is performed after the alkali reaction step. For example, the dealcoholization step (low-boiling point removal step), desalting step, alkali reaction step, and dealkalization step may be performed at any appropriate location, but are typically performed after the hydrogenation step. Among the above steps, the catalyst separation step, alkali neutralization step, dealcoholization step (low-boiling point removal step), desalting step, alkali reaction step, and dealkalization step may be performed as needed, but are not necessarily required.

[0104] FIG. 1 is a flowchart showing an example of a production method (purification method) for producing a 1,3-butylene glycol product according to the present disclosure. A is a dehydrating tower and is involved in the dehydration step. B is a demineralizing tower and is involved in the demineralizing step. C is a high boiler removal distillation tower (high boiler removal tower) and is involved in the high boiler removal distillation step (high boiler removal step). D is an alkali reactor and is involved in the alkali reaction step. E is a dealkalizing tower and is involved in the dealkalizing step. F is a product distillation tower (product tower) and is involved in the product distillation step. A-1, B-1, C-1, E-1, and F-1 are condensers. A-2, C-2, and F-2 are reboilers. Hereinafter, an example of an embodiment of the above-described method for producing 1,3-butylene glycol will be described using this flow sheet.

[0105] Crude 1,3-butylene glycol (corresponding to "X-1") obtained by hydrogen reduction of the hydrogenated raw material is supplied to the dehydration tower A. The crude 1,3-butylene glycol (corresponding to "X-1") may be supplied to the dehydration tower A after undergoing a dealcoholization step (distillation step using a dealcoholization tower) for removing alcohols such as ethanol and low boiling points.

[0106] In the production method of the present disclosure, in the dehydration column A used in the dehydration step, for example, a feed liquid containing 1,3-butylene glycol and water is subjected to distillation, and a liquid concentrated with low-boiling components including water is distilled from above the feed stage (preferably the top of the column) (corresponding to "X-2" in FIG. 1). Also, a crude 1,3-butylene glycol stream containing 1,3-butylene glycol is obtained from below the feed stage (preferably the bottom of the column).

[0107] Dehydration column A and other distillation columns for separating 1,3-butylene glycol can be, for example, perforated plate columns or bubble cap columns. However, packed columns with low pressure loss, such as Sulzer Packing or Melapak (both trade names of Sumitomo Heavy Industries, Ltd.), are preferred. This is because 1,3-butylene glycol and trace impurities contained therein undergo thermal decomposition at high temperatures (e.g., 150°C or higher) to produce low-boiling substances that cause coloration, and therefore the distillation temperature must be low. Furthermore, a long thermal history (residence time) of 1,3-butylene glycol can have a similar effect. Therefore, the reboiler used should be one with a short residence time for the process fluid, such as a gravity-flow thin-film evaporator or a forced-agitation thin-film evaporator.

[0108] The number of theoretical plates in the dehydrating column A is, for example, 1 to 100, preferably 2 to 80, 3 to 80, 4 to 60, 5 to 40, 6 to 30, or 7 to 20, and more preferably 8 to 15. The feed position of the charge liquid is, for example, 10 to 90%, preferably 20 to 80%, more preferably 30 to 70%, and even more preferably 40 to 60% of the height of the column downward from the top of the column. In the distillation in the dehydrating column A, the pressure (absolute pressure) at the top of the column is, for example, 101 kPa or less, preferably 0.1 to 90 kPa, more preferably 0.5 to 70 kPa, even more preferably 1 to 50 kPa, 2 to 30 kPa, or 3 to 20 kPa, and particularly preferably 4 to 10 kPa. The distillation in the dehydration column A may be carried out under pressure, and in that case, the pressure (gauge pressure) at the top of the column may be, for example, 0.2 MPaG or less, or 0.1 MPaG or less.

[0109] The concentration of 1,3-butylene glycol in the liquid fed to dehydrating tower A is, for example, 9% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, even more preferably 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, or 60% by weight or more, and particularly preferably 70% or more. The upper limit of the concentration of 1,3-butylene glycol in the liquid fed to dehydrating tower A is, for example, 90% by weight, 85% by weight, or 80% by weight. However, in consideration of the hydrogenation reaction in the step before the dehydration step, etc., a higher water concentration in the liquid fed to dehydrating tower A may be preferable. Taking all of this into consideration, the concentration of 1,3-butylene glycol in the feed liquid to dehydration column A may be, for example, 1% by weight or more, 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In addition, the concentration of 1,3-butylene glycol in the feed liquid to dehydration column A may be, for example, 99% by weight or less, 95% by weight or more, 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, or 45% by weight or less. The concentration of 1,3-butylene glycol in the liquid charged to the dehydrating tower A can be adjusted to the above range by, for example, adjusting the reaction conditions in the hydrogenation step (e.g., the concentration of acetaldols used as a raw material) and the distillation conditions of a dealcoholization tower (low boiling point removal tower) that is installed as needed before the dehydrating tower.

[0110] The concentration (wt%) of 1,3-butylene glycol was determined by calculating the ratio of the area of ​​the 1,3-butylene glycol peak to the total peak area (GC area%) in gas chromatography analysis under the following conditions, and then calculating it using the following formula: The concentration (wt%) of water in the liquid charged to dehydration tower A was measured by the method described below (Karl Fischer method). Concentration of 1,3-butylene glycol in the feed liquid to dehydration tower A (wt%) = (1 - water concentration in the feed liquid to dehydration tower A (wt%) / 100) x GC area % of the above 1,3-butylene glycol (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[0111] In the production method of the present disclosure, the content of acetaldehyde in the feed liquid to dehydration tower A is, for example, 1000 ppm or less, preferably 900 ppm or less, more preferably 800 ppm or less, 700 ppm or less, 600 ppm or less, or 500 ppm or less, and even more preferably 400 ppm or less, 300 ppm or less, 200 ppm or less, 155 ppm or less, or 140 ppm or less, and may be 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, 2 ppm or less, or 1 ppm or less.

[0112] The content of crotonaldehyde in the feed liquid to dehydration tower A is, for example, 400 ppm or less, preferably 300 ppm or less, more preferably 200 ppm or less, even more preferably 150 ppm or less, 130 ppm or less, 117 ppm or less, or 100 ppm or less, and may be 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, 2 ppm or less, or 1 ppm or less.

[0113] The acetaldehyde and crotonaldehyde contents in the feed liquid to dehydrating tower A can be reduced, for example, by providing a dealcoholization tower (low boiling point removal tower) upstream of dehydrating tower A and adjusting the distillation conditions of the dealcoholization tower (low boiling point removal tower). For example, the acetaldehyde and crotonaldehyde contents in the feed liquid to dehydrating tower A can be reduced by increasing the reflux ratio, number of stages, and distillate yield of the dealcoholization tower (low boiling point removal tower). Furthermore, the acetaldehyde and crotonaldehyde contents can also be adjusted by the conditions of the hydrogenation reaction in the hydrogenation step. When hydrogenation is completed, the acetaldehyde and crotonaldehyde concentrations can be reduced to below the detection limit, but disadvantages such as an increase in reaction pressure and a larger reaction tank arise.

[0114] The acetaldehyde content and crotonaldehyde content in the liquid fed to the dehydration tower A can be determined quantitatively by GC-MS analysis (gas mass spectrometry).

[0115] In the production method of the present disclosure, the water content in the liquid fed to dehydration tower A is, for example, 90% by weight or less, 85% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, or 40% by weight or less, preferably 35% by weight or less, more preferably 30% by weight or less, and even more preferably 25% by weight or less. The lower limit of the water content in the liquid fed to dehydration tower A is, for example, 10% by weight or 15% by weight. In addition, when considering the hydrogenation reaction in the hydrogenation step, a high water concentration and low viscosity are advantageous for the hydrogenation reaction because they increase the solubility and dispersibility of hydrogen in the liquid. The water content in the liquid fed to dehydration tower A can be reduced, for example, by providing a dealcoholization tower (low boiling point removal tower) upstream of dehydration tower A and adjusting the distillation conditions of the dealcoholization tower (low boiling point removal tower). For example, the water content in the liquid charged to the dehydrating tower A can be reduced by increasing the reflux ratio, number of stages, and distillate rate of the dealcoholization tower (low boiling point removal tower). The water content in the liquid charged to the dehydrating tower A can be quantified using a Karl Fischer water content meter.

[0116] In the production method of the present disclosure, the content of low-boiling components (excluding water) in the feed liquid to dehydrating tower A is, for example, 20% or less, preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, particularly preferably 3% or less or 2% or less, and may be 1% or less, 0.5% or less, or 0.1% or less. The content of low-boiling components excluding water (also referred to as "low boilers" or "low boilers") in the feed liquid to dehydrating tower A is the ratio (area %) of the total area of ​​peaks having a shorter retention time than the peak of 1,3-butylene glycol to the total peak area in gas chromatography analysis under the above conditions. The content of low-boiling components (excluding water) in the feed liquid to dehydrating tower A can be reduced, for example, by providing a dealcoholization tower (low boiling tower) upstream of dehydrating tower A and adjusting the distillation conditions of the dealcoholization tower (low boiling tower). For example, by increasing the reflux ratio, number of stages, or distillate rate of the dealcoholization tower (low boiling point removal tower), it is possible to reduce the concentration of low boiling point components (excluding water) in the liquid fed to the dehydration tower A. In addition, the concentration of low boiling point components (excluding water) in the liquid fed to the dehydration tower A can also be reduced by, for example, the reaction conditions (e.g., reaction temperature) in the hydrogenation step.

[0117] The content of high-boiling components in the liquid fed to dehydrating column A is, for example, 20% or less, preferably 10% or less, more preferably 7% or less, 4% or less, 3% or less, or 2% or less, even more preferably 1% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, or 0.05% or less, and particularly preferably 0.01% or less. The content of high-boiling components in the liquid fed to dehydrating column A can be adjusted, for example, by the reaction conditions in the hydrogenation step (e.g., reaction temperature, etc.). The content of high-boiling components in the liquid fed to dehydrating column A is the ratio (area %) of the total area of ​​peaks having a longer retention time than the 1,3BG peak to the total peak area in gas chromatography analysis under the above conditions.

[0118] In the production method of the present disclosure, the reflux ratio in the dehydrating tower A [amount refluxed to the dehydrating tower / amount distilled out of the dehydrating tower (amount discharged outside the distillation tower)] is, from the viewpoint of reducing the content of low boilers (including water) in a crude 1,3-butylene glycol stream containing 1,3-butylene glycol taken out from below the feed tray of the dehydrating tower A (preferably from the bottom of the tower), for example, more than 0.3, preferably 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 15 or more, 20 or more, or 25 or more, and more preferably 30 or more (e.g., 40 or more). In particular, in Production Method 2 of the present disclosure, the reflux ratio in dehydrating tower A is preferably 10 or more, more preferably 20 or more, even more preferably 30 or more, and particularly preferably 50 or more. The upper limit of the reflux ratio is, for example, 100, preferably 50, from the viewpoint of energy costs. When the number of theoretical plates of dehydrating tower A is sufficiently large, sufficient separation is possible if the reflux ratio is, for example, 0.03 or more. In the reflux to dehydrating tower A, a condensate of the dehydrating tower top vapor is usually refluxed to the dehydrating tower, but part or all of the reflux may be replaced by charging a water-containing liquid (e.g., pure water, etc.) to the dehydrating tower. In this case, the "dehydrating tower reflux amount" means the sum of the reflux amount of the condensate of the dehydrating tower top vapor to the dehydrating tower and the charging amount of the water-containing liquid (e.g., pure water, etc.) to the dehydrating tower.

[0119] In the production method of the present disclosure, the distillation rate in dehydrating tower A can be appropriately set depending on the concentration of water in the feed liquid to dehydrating tower A. The distillation rate is desirably a rate sufficient to distill off all of the water in the feed liquid. For example, when the water concentration in the feed liquid to dehydrating tower A is X% by weight, the distillation rate in dehydrating tower A is preferably X% by weight or more. Therefore, the distillation rate in dehydrating tower A is, for example, 95% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, or 5% by weight or less. The distillate yield refers to the ratio (wt %) of the amount of liquid withdrawn from the dehydrating tower A above the feed tray (for example, the top of the tower) to the amount charged to the dehydrating tower A.

[0120] In the production method of the present disclosure, the 1,3BG recovery rate in the dehydration tower A is, for example, 99.3% or more. In this specification, the 1,3BG recovery rate in the dehydration tower A is a value (%) calculated by the following formula: {1 - [1,3BG concentration in distillate (wt%) x (distillate volume (parts) - recycled volume (parts))] / (1,3BG concentration in feed solution (wt%) x feed volume (parts))} x 100 Furthermore, low-boiling and high-boiling substances may be hydrolyzed with water to produce 1,3BG, while high-boiling substances may be produced by polymerization of 1,3BG. Furthermore, trace impurities may be produced or lost, so the material balance in the dehydration tower may not always be achieved. This also applies to other distillation towers, such as dealcoholization towers (low-boiling towers), high-boiling towers, and product towers.

[0121] Next, a crude 1,3-butylene glycol stream containing 1,3-butylene glycol withdrawn from the dehydrating tower A below the feed tray (preferably from the bottom) is supplied to a demineralizing tower B. In the demineralizing tower B, a crude 1,3-butylene glycol stream after desalting is obtained from the top of the tower by distillation, and salts, high boiling point substances, etc. are discharged as bottoms from the bottom of the tower. The bottoms rate (%) of the demineralizing tower B [(demineralizing tower bottoms amount (parts) / demineralizing tower charge amount (parts)) × 100] is, for example, 0.1 to 40 wt%, preferably 1 to 35 wt%, more preferably 2 to 30 wt%, even more preferably 3 to 25 wt%, particularly preferably 5 to 20 wt%, and may be 7 to 15 wt%. At least a portion of the bottoms from the demineralizing tower may be recycled to a process prior to the desalting step.

[0122] The crude 1,3-butylene glycol stream after the desalting is supplied to a high boiling removal column C. In the high boiling removal column C, high boiling components (high boilers) are discharged from below the feed tray (preferably from the bottom of the column). On the other hand, a crude 1,3-butylene glycol stream after the high boilers have been removed (1,3-butylene glycol with improved purity) is obtained from above the feed tray.

[0123] Although perforated plate columns, bubble cap columns, and the like can be used as the high-boiling column C, a packed column with low pressure loss, such as Sulzer Packing or Melapak (both trade names of Sumitomo Heavy Industries, Ltd.), is more preferred. This is because 1,3-butylene glycol and trace amounts of impurities contained therein undergo thermal decomposition at high temperatures (e.g., 150°C or higher), producing low-boiling substances that cause coloration, and therefore the distillation temperature must be low. Furthermore, a long thermal history (residence time) of 1,3-butylene glycol can have a similar effect. Therefore, the reboiler used is preferably one with a short residence time for the process fluid, such as a gravity-flow thin-film evaporator or a forced-agitation thin-film evaporator.

[0124] The number of theoretical plates in the high boiling removal column C is, for example, 1 to 100, preferably 2 to 90, more preferably 3 to 80, even more preferably 4 to 70, 5 to 60, 8 to 50, or 10 to 40, and particularly preferably 15 to 30. The feed position of the charge liquid is, from the top of the high boiling removal column downward, for example, 10 to 90%, preferably 20 to 80%, more preferably 30 to 70, and even more preferably 40 to 60% of the height of the column. In the distillation in the high boiling removal column C, the pressure (absolute pressure) at the top of the column is, for example, 0.01 to 50 kPa, preferably 0.1 to 30 kPa, more preferably 0.3 to 20 kPa, and even more preferably 0.5 to 10 kPa.

[0125] In Production Method 1 of the present disclosure, the concentration of 1,3BG in the feed liquid to high boiling desorption tower C is, for example, 95% or more, preferably 96% or more (e.g., 96.7% or more), more preferably 97% or more, even more preferably 98% or more, and particularly preferably 99% or more. In Production Method 2 of the present disclosure, the concentration of 1,3BG in the feed liquid to high boiling desorption tower C is 96.7% or more, preferably 97% or more, more preferably 98% or more, and even more preferably 99% or more. The concentration of 1,3BG in the feed liquid to high boiling desorption tower C can be improved by adjusting the distillation conditions of dehydrating tower A and demineralizing tower B. For example, the concentration of 1,3BG in the feed liquid to high boiling desorption tower C can be increased by increasing the reflux ratio of dehydrating tower A or increasing the bottoms rate of demineralizing tower B. The above concentration of 1,3BG is the ratio (area %) of the area of ​​the 1,3BG peak to the total peak area in gas chromatography analysis (GC analysis) under the following conditions. (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[0126] The content of high boiling point components in the feed liquid to high boiling desorption tower C is, for example, 4% or less, preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, or 0.05% or less, and particularly preferably 0.01% or less. In particular, in production method 2 of the present disclosure, the content of high boiling point components in the feed liquid to high boiling desorption tower C is preferably 3% or less, more preferably 2% or less, even more preferably 1.5% or less, 1% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, or 0.05% or less, and particularly preferably 0.01% or less. The content of high boiling point components in the feed liquid to high boiling desorption tower C can be reduced by adjusting the distillation conditions of the demineralization tower B. For example, the content of high boiling point components in the liquid fed to high boiling desorption column C can be reduced by increasing the bottoms rate of demineralization column B. The content of high boiling point components in the liquid fed to high boiling desorption column C is the ratio (area %) of the total area of ​​peaks with longer retention times than the peak of 1,3BG to the total peak area in gas chromatography analysis under the above conditions.

[0127] In the production method of the present disclosure, the content of acetaldehyde in the feed liquid to high boiling removal column C is, for example, 500 ppm or less, preferably 205 ppm or less (e.g., 200 ppm or less), more preferably 100 ppm or less, even more preferably 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, or 10 ppm or less, and particularly preferably 5 ppm or less, and may be less than 2 ppm or less than 1 ppm. The crotonaldehyde content in the feed liquid to high boiling desorption column C is, for example, 200 ppm or less, preferably 110 ppm or less, more preferably 100 ppm or less, even more preferably 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, or 3 ppm or less, and particularly preferably 2 ppm or less, and may even be less than 1 ppm. The acetaldehyde content and crotonaldehyde content in the feed liquid to high boiling desorption column C can be reduced, for example, by providing a dealcoholization column (low boiling desorption column) or a dehydration column upstream of high boiling desorption column C and adjusting the distillation conditions of the dealcoholization column (low boiling desorption column) or the dehydration column. For example, by increasing the reflux ratio, number of stages, and distillate yield of the dealcoholization tower (low boiling removal tower) and the dehydration tower, it is possible to reduce the acetaldehyde content and the crotonaldehyde content in the liquid fed to the high boiling removal tower C. The acetaldehyde content and the crotonaldehyde content in the liquid fed to the high boiling removal tower C can be quantified by GC-MS analysis (gas mass spectrometry).

[0128] In the production method of the present disclosure, the water content in the feed liquid to high boiling removal column C is, for example, 3% by weight or less, preferably 2% by weight or less, more preferably 1.2% by weight or less, even more preferably 1.1% by weight or less, 1.0% by weight or less, 0.95% by weight or less, 0.9% by weight or less, 0.8% by weight or less, 0.7% by weight or less, 0.6% by weight or less, 0.5% by weight or less, 0.4% by weight or less, 0.3% by weight or less, or 0.2% by weight or less, and particularly preferably 0.1% by weight or less. The water content in the feed liquid to high boiling removal column C can be reduced by adjusting the distillation conditions of the dehydrating column A. For example, the water concentration in the feed liquid to high boiling removal column C can be reduced by increasing the reflux ratio, number of stages, or distillate rate of the dehydrating column A. The water content in the feed liquid to high boiling removal column CF can be quantified using a Karl Fischer water content meter. In addition, in the production method 2 of the present disclosure, the water content in the liquid fed to the high boiling removal tower C is 3% by weight or less, preferably 2% by weight or less, 1.2% by weight or less, 0.4% by weight or less, 0.3% by weight or less, or 0.2% by weight or less, and particularly preferably 0.1% by weight or less, 0.05% by weight or less, or 0.03% by weight or less.

[0129] In the production method of the present disclosure, the content of low-boiling components (excluding water) in the liquid fed to high boiling removal column C is, for example, 1.8% or less, preferably 1.6% or less, more preferably 1.4% or less, even more preferably 1.2% or less, 1.1% or less, 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or 0.2% or less, and particularly preferably 0.1% or less. The content of low-boiling components excluding water (also referred to as "low boilers" or "low boilers") in the liquid fed to high boiling removal column C is the ratio (area %) of the total area of ​​peaks having a shorter retention time than the peak of 1,3-butylene glycol to the total peak area in gas chromatography analysis under the above conditions. The content of low boiling point components (excluding water) in the liquid fed to the high boiling decoupling tower C can be reduced, for example, by providing a dealcoholization tower (low boiling decoupling tower) upstream of the high boiling decoupling tower C and adjusting the distillation conditions of the dealcoholization tower (low boiling decoupling tower). For example, the concentration of low boiling point components (excluding water) in the liquid fed to the high boiling decoupling tower C can be reduced by increasing the reflux ratio, number of stages, or distillate yield of the dealcoholization tower (low boiling decoupling tower).

[0130] In the production method of the present disclosure, the reflux ratio in high boiling removal column C [amount refluxed to high boiling removal column / amount distilled from high boiling removal column (amount discharged outside the distillation column)] is, from the viewpoint of lowering the dry point of the 1,3-butylene glycol product, 0.03 or more, preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.2 or more, 1.5 or more, 2 or more, 3 or more, 4 or more, 5 or more, or 10 or more, and particularly preferably 20 or more. In particular, in Production Method 2 of the present disclosure, the reflux ratio in high boiling removal tower C is preferably 0.1 or more, more preferably 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.2 or more, 1.5 or more, 2 or more, 3 or more, 4 or more, 5 or more, or 10 or more, and particularly preferably 20 or more. From the viewpoint of energy costs, the upper limit of the reflux ratio is, for example, 100, preferably 50. When the number of theoretical plates in high boiling removal tower C is large, sufficient separation is possible even if the reflux ratio in high boiling removal tower C is about 1 or less.

[0131] In the production method of the present disclosure, by setting the reflux ratio in high boiling point removal tower C within the above range, high-purity 1,3BG with an extremely low content of high-boiling point components and a low dry point can be produced at a high recovery rate.

[0132] In the production method of the present disclosure, the bottoms yield of the high boiling removal tower C is, for example, less than 30% by weight. However, this is not the case when the bottoms of the high boiling removal tower are distilled in an additional distillation tower to remove high boiling components and then commercialize the resulting 1,3BG. 1,3BG can be obtained in high yield by limiting the final amount of high boiling components withdrawn from the system to less than 30% by weight of the amount charged to the high boiling removal tower C. The bottoms yield refers to the ratio (by weight) of the amount of liquid withdrawn from below the feed tray of the high boiling removal tower C (for example, from the bottom of the tower) to the amount charged to the high boiling removal tower C (including the recycled amount if this liquid is recycled to the previous process described below). When this liquid is recycled to the previous process described below, the lower the outflow rate, the higher the recovery rate of 1,3BG.

[0133] The bottoms rate of the high boiling removal column C is preferably 25% by weight or less, more preferably 20% by weight or less, even more preferably 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, or 2% by weight or less, and can be 1% by weight or less, from the viewpoint of improving the recovery rate of 1,3BG. Furthermore, the bottoms rate of the high boiling removal column C is, for example, 0.01% by weight or more, preferably 0.1% by weight or more, 0.5% by weight or more, or 1% by weight or more, more preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 6% by weight or more, 7% by weight or more, 8% by weight or more, 9% by weight or more, 10% by weight or more, or 15% by weight or more, and particularly preferably 20% by weight or more, from the viewpoint of lowering the dry point of the 1,3-butylene glycol product.

[0134] At least a portion of the liquid containing concentrated high-boiling components withdrawn from below the feed tray of high-boiling column C (hereinafter, sometimes referred to as "bottom liquid") may be recycled to a step preceding the high-boiling component removal step (dashed arrow shown below high-boiling column C in Figure 1). By recycling at least a portion of the bottom liquid to a step preceding the high-boiling component removal step, the recovery rate of 1,3BG can be improved. In this specification, the recovery rate of 1,3BG in high-boiling column C is a value (%) calculated by the following formula: {1 - [GC area % of 1,3BG in bottoms × (bottoms amount (parts) - recycled amount (parts))] / (GC area % of 1,3BG in feed solution × feed amount (parts))} × 100 Note that low-boiling and high-boiling substances may be hydrolyzed with water to produce 1,3BG, while high-boiling substances may be produced by polymerization of 1,3BG. Furthermore, trace impurities may be produced or lost, so that a material balance in the high-boiling removal tower may not always be obtained.

[0135] The recovery rate of 1,3BG in high boiler removal column C is, for example, more than 80%, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 99% or more.

[0136] Examples of processes preceding the high-boiling point removal process include an acetaldehyde polymerization process (an aldol condensation process of acetaldehyde), a reaction process (a hydrogenation process), a dealcoholization process (a low-boiling point removal process), a dehydration process, and a desalination process. Among these, since 1,3BG is produced by hydrolysis of high-boiling points, it is preferable to recycle the acetaldehyde to the acetaldehyde polymerization process (an aldol condensation process of acetaldehyde). Furthermore, 1,3BG may also be produced by hydrogenation reduction, and from this perspective, the acetaldehyde may be recycled to the hydrogenation process.

[0137] The amount of the bottoms recycled to the process prior to the high boiling point removal step can be appropriately selected within the range of the amount of the bottoms. The amount of the bottoms recycled to the process prior to the high boiling point removal step is, for example, less than 30% by weight, preferably 25% by weight or less, based on the amount charged to high boiling point removal column C. The recycled amount may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less, based on the amount charged to high boiling point removal column C. From the viewpoint of improving the 1,3BG recovery rate in the high boiling removal tower and the yield throughout the 1,3BG production process, the amount of the bottoms recycled to the steps preceding the high boiling removal tower is, for example, 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 7% by weight or more, or 10% by weight or more, and particularly preferably 20% by weight or more, relative to the amount charged to high boiling removal tower C. Note that when the amount of bottoms is minimized, 1,3BG can be recovered at a high yield without recycling to the preceding steps.

[0138] In Production Method 2 of the present disclosure, the crude 1,3-butylene glycol stream withdrawn from above the feed tray of the high boiling removal tower C can be used as a 1,3-butylene glycol product as is. Alternatively, the crude 1,3-butylene glycol stream withdrawn from above the feed tray of the high boiling removal tower C can be subjected to an alkali treatment in an alkali reactor D described below and evaporated (or distilled) in a dealkalizer E, and the overhead distillate of the dealkalizer E can be used as a 1,3-butylene glycol product.

[0139] According to Production Method 2 of the present disclosure, the acetaldehyde and crotonaldehyde contents in the high boiling removal tower feed liquid are set within specific ranges, and the reflux ratio of the high boiling removal tower is set within a specific range. This makes it possible to industrially efficiently produce high-purity 1,3-butylene glycol that is colorless and odorless (or almost colorless and odorless), is resistant to coloration and odor generation over time, and is resistant to an increase in acid concentration over time even when containing water.

[0140] In Production Method 1 of the present disclosure, the crude 1,3-butylene glycol stream withdrawn from the high boiler removal column C above the feed stage is supplied to, for example, an alkali reactor (e.g., a flow-type tubular reactor) D and subjected to a base treatment (alkali treatment). By base treatment, by-products contained in the crude 1,3-butylene glycol can be decomposed. The base is added to the alkali reactor D or to a pipe upstream thereof. The amount of base added is, for example, 0.05 to 10 wt %, preferably 0.1 to 1.0 wt %, based on the crude 1,3-butylene glycol stream to be subjected to the alkali treatment. If the amount of base added exceeds 10 wt %, the base may precipitate in the distillation column, pipes, etc., and cause blockage. Furthermore, a decomposition reaction of high-boiling compounds may occur, which may result in the generation of by-products. If the amount of base added is less than 0.05 wt %, the effect of decomposing by-products is small.

[0141] The base added to the alkaline reactor D or the piping upstream thereof is not particularly limited, but is preferably, for example, an alkali metal compound. Examples of alkali metal compounds include sodium hydroxide, potassium hydroxide, sodium (bi)carbonate, and potassium (bi)carbonate. A basic ion exchange resin can also be used as the base. From the viewpoint of reducing by-products contained in the finally obtained 1,3-butylene glycol product, sodium hydroxide and potassium hydroxide are preferred as the base. The base may be added as a solid as is, but is preferably added as an aqueous solution for operational reasons and to promote contact with the liquid to be treated. The above bases may be used alone or in combination of two or more.

[0142] The reaction temperature in the alkali reactor D is not particularly limited, but is preferably 90 to 140°C, more preferably 110 to 130°C, for example. If the reaction temperature is less than 90°C, a long reaction residence time is required, which increases the reactor capacity and is uneconomical. If the reaction temperature exceeds 140°C, the coloration of the final 1,3-butylene glycol product may increase. The reaction residence time is preferably 5 to 120 minutes, more preferably 10 to 30 minutes, for example. If the reaction residence time is less than 5 minutes, the reaction may be insufficient, and the quality of the final 1,3-butylene glycol product may deteriorate. If the reaction residence time exceeds 120 minutes, a large reactor is required, which increases the equipment cost and is therefore disadvantageous from an economic standpoint.

[0143] After leaving the alkali reactor D, the crude reaction liquid stream is optionally supplied to a dealkalizer (e.g., a thin-film evaporator) E, where the base and other components are removed from the bottom of the column by evaporation. Meanwhile, a crude 1,3-butylene glycol stream (which becomes the 1,3-butylene glycol product in Production Method 2 of the present disclosure) after debasing is obtained from the top of the dealkalizer E. The evaporator used in the dealkalizer E is preferably a gravity-flow thin-film evaporator or a forced-agitation thin-film evaporator with a short residence time, in order to minimize the thermal history of the process fluid. A demister may be installed in the space above the charge position of the dealkalizer (e.g., thin-film evaporator) E to remove droplets of the base and other components. This prevents the base and other components from being mixed into the 1,3-butylene glycol product.

[0144] In the evaporator used in the dealkalizer E, evaporation is carried out at the top of the column under a reduced pressure of, for example, 20 kPa absolute pressure or less, preferably 0.5 to 10 kPa absolute pressure. The temperature of the evaporator is preferably, for example, 90 to 120°C. The crude 1,3-butylene glycol stream containing low boiling point substances distilled from the top of the column is supplied to a product distillation column (product column) F. As described above, in Production Method 2 of the present disclosure, the distillate (corresponding to E-1) from the top of the dealkalizer E can be used as the 1,3-butylene glycol product.

[0145] The alkali reactor D and the dealkalizer E may be installed between the demineralizer B and the high boiling demineralizer C, between the demineralizer A and the demineralizer B (in this case, the demineralizer may also serve as the dealkalizer), or before the dehydrator A. Alternatively, the alkali treatment can be performed without installing the alkali reactor D and the dealkalizer E by feeding a base into the high boiling demineralizer feed line, feeding into the dehydrator feed line, or adding it to the reaction liquid after hydrogenation [and then feeding it into the dealcoholizer (low boiling demineralizer)].

[0146] In production method 1 of the present disclosure, in product column F used in the product distillation step, a feed liquid having a 1,3-butylene glycol concentration of, for example, 97.6 area % or more as determined by GC analysis is distilled, a liquid in which low-boiling point components are concentrated is distilled from above the feed stage (corresponding to "X-6" in FIG. 1), and 1,3-butylene glycol is withdrawn from below the feed stage (corresponding to "Y" in FIG. 1). The withdrawn 1,3-butylene glycol can be used as a 1,3-butylene glycol product.

[0147] For example, a perforated plate column or a bubble cap column can be used as product column F. However, a packed column with low pressure drop, such as Sulzer Packing or Melapak (both trade names of Sumitomo Heavy Industries, Ltd.), is more preferable. This is because 1,3-butylene glycol and trace amounts of impurities contained therein undergo thermal decomposition at high temperatures (e.g., 150°C or higher), producing low-boiling substances that cause coloration, and therefore the distillation temperature must be low. Furthermore, a long thermal history (residence time) of 1,3-butylene glycol can have a similar effect. Therefore, the reboiler used should be one with a short residence time for the process fluid, such as a gravity-flow thin-film evaporator or a forced-agitation thin-film evaporator.

[0148] The number of theoretical plates in product column F is, for example, 1 to 100, preferably 2 to 90, 3 to 80, 4 to 70, 5 to 60, 8 to 50, or 10 to 40, and more preferably 15 to 30. The feed position of the charge liquid is, for example, 10 to 90%, preferably 20 to 80%, more preferably 30 to 70%, and even more preferably 40 to 60% of the height of the column downward from the top of the column. In the distillation in product distillation column F, the pressure (absolute pressure) at the top of the column is, for example, 20 kPa or less, preferably 0.1 to 10 kPa, more preferably 0.3 to 8 kPa, and even more preferably 0.5 to 5 kPa.

[0149] In Figure 1, the feed to product tower F is the liquid obtained by condensing the top vapor of dealkalization tower E in condenser E-1, but the top vapor from dealkalization tower E may also be fed directly to product tower F.

[0150] The concentration of 1,3-butylene glycol in the feed liquid (1,3-butylene glycol feed liquid) to product column F is 97.6% or more, preferably 97.8% or more, more preferably 98% or more, even more preferably 98.2% or more (e.g., 98.4% or more, 98.6% or more, or 98.8% or more), and particularly preferably 99% or more (e.g., 99.1% or more, 9.2% or more, 99.3% or more, 99.4% or more, 99.5% or more, 99.6% or more, 99.7% or more, 99.8% or more, or 99.9% or more).

[0151] The concentration of 1,3-butylene glycol in the liquid charged to product column F can be improved, for example, by adjusting the distillation conditions of dehydrating column A, by providing a dealcoholization column (low boiling column) upstream of dehydrating column A and adjusting the distillation conditions therefor, or by adjusting the distillation conditions of high boiling column C. For example, the purity of 1,3-butylene glycol in the liquid charged to product column F can be increased by increasing the reflux ratio of the dealcoholization column (low boiling column), dehydrating column A, and / or high boiling column C, or by increasing the number of plates.

[0152] The concentration of 1,3-butylene glycol in the liquid charged to the product column F is the ratio (area %) of the area of ​​the 1,3-butylene glycol peak to the total peak area in gas chromatography analysis under the following conditions. (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[0153] In the production method 1 of the present disclosure, the content of acetaldehyde in the feed liquid to product column F is 500 ppm or less, preferably 205 ppm or less (e.g., 200 ppm or less), more preferably 150 ppm or less, even more preferably 120 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, or 10 ppm or less, and particularly preferably 5 ppm or less, and may be less than 2 ppm. The crotonaldehyde content in the feed liquid to product column F is 200 ppm or less, preferably 150 ppm or less, more preferably 130 ppm or less, even more preferably 110 ppm or less, 100 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, or 3 ppm or less, and particularly preferably 2 ppm or less, and may even be less than 1 ppm. The acetaldehyde content and crotonaldehyde content in the feed liquid to product column F can be reduced, for example, by providing a dealcoholization column (low boiling point removal column) or a dehydration column upstream of product column F and adjusting the distillation conditions of the dealcoholization column (low boiling point removal column) or the dehydration column. For example, the acetaldehyde content and crotonaldehyde content in the feed liquid to product column F can be reduced by increasing the reflux ratio, number of stages, and distillate rate of the dealcoholization column (low boiling point removal column) and the dehydration column. The acetaldehyde content and crotonaldehyde content in the feed liquid to product column F can be reduced by increasing the reaction temperature, the residence time, or the amount of base added in the alkali reaction step. The acetaldehyde content and crotonaldehyde content in the feed liquid to product column F can be quantified by GC-MS analysis (gas mass spectrometry).

[0154] In Production Method 1 of the present disclosure, the water content in the feed liquid to product column F is 0.7% by weight or less, preferably 0.6% by weight or less, 0.5% by weight or less, 0.4% by weight or less, 0.3% by weight or less, or 0.2% by weight or less, and particularly preferably 0.1% by weight or less. The water content in the feed liquid to product column F can be reduced by adjusting the distillation conditions of the dehydrating column A. For example, the water concentration in the feed liquid to product column F can be reduced by increasing the reflux ratio, number of stages, or distillate rate of the dehydrating column A. The water content in the feed liquid to product column F can be quantified using a Karl Fischer moisture content meter.

[0155] The content of low-boiling components (excluding water) in the liquid fed to product column F is, for example, 1.8% or less, preferably 1.6% or less, more preferably 1.4% or less, even more preferably 1.2% or less, 1.1% or less, 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or 0.2% or less, and particularly preferably 0.1% or less. The content of low-boiling components (excluding water) in the liquid fed to product column F is the ratio (area %) of the total area of ​​peaks having a shorter retention time than the peak of 1,3-butylene glycol to the total peak area in gas chromatography analysis under the above conditions. The content of low-boiling components (excluding water) in the liquid fed to product column F can be reduced, for example, by providing a dealcoholization column (low-boiling column) upstream of product column F and adjusting the distillation conditions of the dealcoholization column (low-boiling column). For example, by increasing the reflux ratio, number of stages, and distillate rate of the dealcoholization tower (low boiling point removal tower), the concentration of low boiling point components (excluding water) in the feed liquid to product tower F can be reduced.

[0156] The content of high-boiling components (excluding water) in the liquid fed to product column F is, for example, 1.8% or less, preferably 1.6% or less, more preferably 1.4% or less, even more preferably 1.2% or less, 1.1% or less, 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or 0.2% or less, and particularly preferably 0.1% or less. The content of high-boiling components excluding water (also referred to as "high boilers" or "high boilers") in the liquid fed to product column F is the ratio (area %) of the total area of ​​peaks having a longer retention time than the peak of 1,3-butylene glycol to the total peak area in gas chromatography analysis under the above conditions. The content of high-boiling components (excluding water) in the liquid fed to product column F can be reduced, for example, by adjusting the distillation conditions of the high-boiling separation column. For example, the concentration of high boiling point components (excluding water) in the liquid fed to the product column F can be reduced by increasing the reflux ratio, number of stages, and bottoms rate of the high boiling separation column.

[0157] In Production Method 1 of the present disclosure, the reflux ratio in product column F [amount refluxed to product column / amount distilled from product column (amount discharged outside the distillation column)] is, from the viewpoint of increasing the initial boiling point of the 1,3-butylene glycol product, 0.3 or more, preferably 0.4 or more, more preferably 0.5 or more, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 20 or more, or 50 or more, and particularly preferably 400 or more (e.g., 500 or more). The upper limit of the reflux ratio in product column F is, for example, 700 or 1000 from the viewpoint of energy costs.

[0158] In Production Method 1 of the present disclosure, the distillate rate from product column F is, for example, less than 30% by weight, preferably 29% by weight or less, more preferably 28% by weight or less, even more preferably 27% by weight or less, 26% by weight or less, 25% by weight or less, 24% by weight or less, 23% by weight or less, 22% by weight or less, 21% by weight or less, 20% by weight or less, 19% by weight or less, 18% by weight or less, 17% by weight or less, 16% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, or 0.6% by weight or less, and particularly preferably 0.4% by weight or less, from the viewpoint of improving the recovery rate of 1,3-butylene glycol. The distillate yield refers to the ratio (by weight) of the amount of liquid extracted from above the feed tray of product column F (e.g., from the top of the column) to the amount charged to product column F (including the recycled amount if recycled to the previous process described below).

[0159] At least a portion of the liquid (hereinafter sometimes referred to as "distillate") in which low boiling components are concentrated and which is withdrawn from above the feed tray of product column F may be recycled to a step preceding the product distillation step (the dashed arrow shown to the right of product column F in FIG. 1). By recycling at least a portion of the distillate to a step preceding the product distillation step, the recovery rate of 1,3-butylene glycol can be improved.

[0160] Examples of the process before the product distillation process include a dehydration process, a dealcoholization process (low boiling point removal process), etc. The dealcoholization process (low boiling point removal process) is preferably performed before the dehydration process.

[0161] The amount of the distillate recycled to the process prior to the product distillation step can be appropriately selected within the range of the amount of the distillate. The amount of the distillate recycled to the process prior to the product distillation step is, for example, less than 30% by weight relative to the amount charged to the product column F. From the viewpoint of improving the 1,3BG recovery rate in the product column and the yield throughout the process, the amount of the distillate recycled to the process prior to the product distillation step is, for example, 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 1.5% by weight or more, 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 7% by weight or more, or 10% by weight or more, and particularly preferably 20% by weight or more.

[0162] In production method 1 of the present disclosure, by setting the contents of acetaldehyde and crotonaldehyde in the feed liquid to product column F to not more than specific values ​​and setting the reflux ratio in product column F within a specific range, it is possible to industrially efficiently produce high-purity 1,3-butylene glycol that is colorless and odorless (or almost colorless and odorless), is resistant to coloration and odor generation over time, and is resistant to an increase in acid concentration over time even when containing water.

[0163] The recovery rate of 1,3BG in product column F is, for example, more than 80%, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 99% or more.

[0164] In this specification, the recovery rate of 1,3BG in product tower F is a value (%) calculated by the following formula. {1 - [GC area % of 1,3BG in the distillate × (distillate amount (parts) - recycled amount (parts))] / (GC area % of 1,3BG in the feed solution × feed amount (parts))} × 100 As mentioned above, low-boiling and high-boiling substances may be hydrolyzed with water to produce 1,3BG, while high-boiling substances may be produced by polymerization of 1,3BG. Therefore, the material balance in the product column may not always be achieved.

[0165] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, each configuration and their combinations in each embodiment are merely examples, and additions, omissions, and other modifications of configurations are possible as appropriate within the scope of the gist of this disclosure. The present disclosure is not limited by the embodiments, but is limited only by the scope of the claims. [Example]

[0166] The present disclosure will be described in more detail below with reference to examples. In the examples, "parts" refers to "parts by weight" unless otherwise specified. Gas chromatography analysis (GC analysis), measurement of initial boiling point, and measurement of water content were performed by the methods described below.

[0167] [Example 1] The method for producing 1,3-butylene glycol will be described with reference to FIG. 100 parts of an acetaldol solution containing 30% by weight of water as a raw material (a mixed solution of 69 parts of acetaldol and 29 parts of water, containing a total of 2 parts of low-boiling and high-boiling impurities, and less than 0.1 parts of Na salt) were charged into a liquid-phase hydrogen reduction reactor with 10 parts of hydrogen, and 15 parts of Raney nickel were added as a catalyst. The reactor was maintained at 120°C and 10 MPa (gauge pressure) to carry out liquid-phase hydrogen reduction. After separating the catalyst from the liquid after the reaction, the liquid was neutralized with caustic soda to obtain crude 1,3-butylene glycol (1) containing low-boiling impurities and water.

[0168] The acetaldehyde solution containing 30% by weight of water used as a raw material was produced by stirring acetaldehyde and water in the presence of 100 ppm by weight of NaOH at 30°C for a residence time of 10 hours to dimerize acetaldehyde [acetaldehyde polymerization process (acetaldehyde aldol condensation process)].

[0169] Crude 1,3-butylene glycol (1) (corresponding to "X-1" in Figure 1) was charged to dehydration column A. The concentration of 1,3-butylene glycol in the charge to dehydration column A was 56 wt%, the concentration of water was 40 wt%, the content of acetaldehyde (AD) was 130 ppm, the content of crotonaldehyde (CR) was 89 ppm, and in the GC analysis described below, the total area ratio of impurity peaks with a shorter retention time (RT) than 1,3-butylene glycol was 3%, and the total area ratio of impurity peaks with a longer retention time than the 1,3-butylene glycol peak was 1%. In dehydration column A, distillation was performed under conditions of a column top pressure of 10 kPa (absolute pressure) and a reflux ratio of 1. Water was extracted from the top of the column, and 43 parts (distillate) per 100 parts of the charge was discharged and removed outside the system (corresponding to "X-2" in Figure 1). From the bottom of the column, crude 1,3-butylene glycol (2) was obtained, which had a 1,3-butylene glycol concentration of 96.9 GC area %, water of 0.9 wt %, a total area ratio of impurity peaks having shorter retention times than 1,3-butylene glycol of 0.8%, a total area ratio of peaks having longer retention times than 1,3-butylene glycol peaks of 2.3%, an acetaldehyde content of 18 ppm, and a crotonaldehyde content of 17 ppm in a GC analysis described below.

[0170] Next, crude 1,3-butylene glycol (2) was charged into demineralizer B. In demineralizer B, salts, high boiling point materials, and a portion of 1,3-butylene glycol were discharged as evaporation residue from the bottom of the column (corresponding to "X-3" in Figure 1). The amount of evaporation residue discharged was 5 parts per 100 parts of the charged liquid. Meanwhile, crude 1,3-butylene glycol (3) containing 1,3-butylene glycol, low boiling point materials, and a portion of the high boiling point materials was obtained from the top of the column.

[0171] Next, the crude 1,3-butylene glycol (3) was charged into high boiling separation column C. In high boiling separation column C, distillation was carried out under conditions of a column top pressure of 5 kPa (absolute pressure) and a reflux ratio of 0.05, and high boiling point materials and a portion of 1,3-butylene glycol were discharged from the column bottom (corresponding to "X-4" in Figure 1). The amount of the discharged material from the column bottom was 20 parts per 100 parts of the charged liquid. Meanwhile, 80 parts of crude 1,3-butylene glycol (4) containing low boiling point materials was obtained as a distillate from the column top.

[0172] Next, the crude 1,3-butylene glycol (4) was charged into an alkaline reactor D. At this time, a 20 wt % aqueous solution of caustic soda was added so that the concentration of caustic soda in the charged liquid was 0.1 wt %. The reaction temperature in the alkaline reactor D was maintained at 120°C, and the reaction was carried out for a residence time of 20 minutes.

[0173] Next, the crude reaction liquid discharged from the alkali reactor D was charged into a dealkalizer E. In the dealkalizer E, caustic soda, high boiling point substances, and a portion of 1,3-butylene glycol were discharged from the bottom of the column (corresponding to "X-5" in Figure 1). The amount of the liquid discharged from the bottom of the column was 10 parts per 100 parts of the charged liquid. Meanwhile, 90 parts of crude 1,3-butylene glycol (5) containing 1,3-butylene glycol and low boiling point substances was obtained from the top of the column. The crude 1,3-butylene glycol (5) containing 1,3-butylene glycol and low boiling point substances was subjected to water content measurement, GC analysis, and GC-MS analysis. As a result, the water concentration was 1 wt %, the area ratio of 1,3-butylene glycol was 99%, the total area ratio of impurity peaks having a shorter retention time than 1,3-butylene glycol was 0.4%, the total area ratio of impurity peaks having a longer retention time than 1,3-butylene glycol was 0.6%, the acetaldehyde content was 20 ppm, and the crotonaldehyde content was 9 ppm.

[0174] Next, crude 1,3-butylene glycol (5) was charged into product column F. In product column F, 10 parts of low boiling point materials and a portion of 1,3-butylene glycol were distilled from the top of the column relative to 100 parts of the charged liquid (corresponding to "X-6" in Figure 1), and the entire amount was discharged outside the system. The column was operated at a reflux ratio (reflux amount / distillate amount) of 0.5, and 90 parts of 1,3-butylene glycol product were obtained from the bottom of the column (distillate amount: 10 parts) (corresponding to "Y" in Figure 1).

[0175] The resulting 1,3-butylene glycol product was subjected to measurement of the initial boiling point, moisture content, GC analysis, and GC-MS analysis. The initial boiling point was 203.3°C, the dry point was 209°C, the moisture content was 0.2% by weight, the area ratio of 1,3-butylene glycol was 99.2%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.08%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 0.7%, the acetaldehyde content was 1.5 ppm, and the crotonaldehyde content was 0.9 ppm. The potassium permanganate test value was 35 minutes. The recovery rate of 1,3-butylene glycol in product column F was 90%.

[0176] [Example 2] The same operation as in Example 1 was carried out, except that the reflux ratio of dehydrating tower A was changed to 50. 1,3-butylene glycol product was obtained from the bottom of product tower F. Note that, due to the change in the conditions of dehydrating tower A, the composition of the dehydrating tower bottoms changed, and the compositions of the charged liquids of high boiling removal tower C and product tower F each changed, resulting in a change in the quality of the product. The resulting 1,3-butylene glycol product was subjected to measurement of the initial boiling point, moisture content, GC analysis, and GC-MS analysis. The initial boiling point was 206.7°C, the dry point was 208.9°C, the moisture content was 0.1% by weight, the area ratio of 1,3-butylene glycol was 99.3%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.05%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 0.7%, the acetaldehyde content was 0.7 ppm, and the crotonaldehyde content was 0.7 ppm. The potassium permanganate test value was 45 minutes. The recovery rate of 1,3-butylene glycol in product column F was 90%.

[0177] [Examples 3 to 27] Dehydration column A, high-boiling dehydration column C, and product column F were operated under the conditions shown in Tables 1 and 2. In Examples 4 to 22 and 24 to 27, the distillate from product column F was entirely recycled to the hydrogen reduction reactor. In Example 23, product column F was not used, and the overhead distillate from dealkalization column E (a demister was installed in the space above the charging position) was used as the 1,3-butylene glycol product. The concentration of the aqueous caustic soda solution in alkali reactor D was increased by 1.5 times, and the amount of aqueous caustic soda solution added was half that of Example 1, thereby minimizing the increase in moisture content due to the alkali treatment. If the alkali concentration of the aqueous caustic soda solution is too high, crystals will precipitate, so it is preferable to heat it to 40°C or higher. In Table 2, the column for "Product column F bottoms" for Example 23 lists the composition and physical properties of the overhead distillate from dealkalization column E. In Example 16, 8 parts of the 10 parts of the high boiling column bottoms were recycled to the hydrogenation step, and 2 parts were discharged outside the system. In Example 25, the pressure of the hydrogenation reaction was reduced to 7 MPaG (gauge pressure). As a result, the acetaldehyde and crotonaldehyde contents in the dehydrating column feed were high. In Example 26, the reflux ratio of the dehydrating column was reduced to 0.3, the purity of 1,3-butylene glycol in the product column feed was reduced, and the reflux ratio of the product column was increased to 20. In Example 27, the pressure of the hydrogenation reaction was increased to 40 MPaG (gauge pressure) (the remaining conditions were the same as in Example 18).

[0178] [Comparative Example 1] The reflux ratio of dehydration tower A was changed to 0.5, the distillate volume to 42 parts, the reflux ratio of high boiling tower C was changed to 0.02, the reflux ratio of product tower F was changed to 0.05, and the distillate volume to 20 parts. 80 parts of 1,3-butylene glycol product was obtained from the bottom of product tower F in the same manner as in Example 1. The initial boiling point of the obtained 1,3-butylene glycol product was 193.2 ° C, the dry point was 210.3 ° C, the water concentration was 0.6 wt%, the area ratio of 1,3-butylene glycol was 98.3%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.2%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 1.5%, the acetaldehyde content was 5 ppm, and the crotonaldehyde content was 4 ppm. The potassium permanganate test value was 0 min. The recovery rate of 1,3-butylene glycol in product tower F was 80%.

[0179] Comparative Example 2 The feed composition of the dehydration tower A was changed, the reflux ratio was changed to 0.5, the distillate amount was changed to 32 parts, the reflux ratio of the high boiling tower C was changed to 0.02, the reflux ratio of the product tower F was changed to 0.05, and the distillate amount was changed to 20 parts. Except for this, 80 parts of 1,3-butylene glycol product was obtained from the bottom of the product tower F in the same manner as in Example 1. The initial boiling point of the obtained 1,3-butylene glycol product was 199.0 ° C., the dry point was 210.1 ° C., the water concentration was 0.4 wt%, the area ratio of 1,3-butylene glycol was 98.5%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.1%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 1.4%, the acetaldehyde content was 4 ppm, and the crotonaldehyde content was 2 ppm. The potassium permanganate test value was 5 minutes. The recovery rate of 1,3-butylene glycol in product column F was 80%.

[0180] Comparative Example 3 The feed composition of the dehydration tower A was changed, the reflux ratio was changed to 0.5, the distillate amount was changed to 32 parts, the reflux ratio of the high boiling tower C was changed to 0.02, the reflux ratio of the product tower F was changed to 0.05, and the distillate amount was changed to 30 parts. Except for this, 70 parts of 1,3-butylene glycol product was obtained from the bottom of the product tower F in the same manner as in Example 1. The initial boiling point of the obtained 1,3-butylene glycol product was 203.0 ° C., the dry point was 210.2 ° C., the water concentration was 0.2 wt%, the area ratio of 1,3-butylene glycol was 98.4%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.1%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 1.5%, the acetaldehyde content was 2 ppm, and the crotonaldehyde content was 1.3 ppm. The potassium permanganate test value was 30 minutes. The recovery rate of 1,3-butylene glycol in product column F was 70%.

[0181] Comparative Example 4 The feed composition of dehydration tower A was changed, the distillate volume was changed to 23 parts, the reflux ratio of high boiling tower C was changed to 0.02, the reflux ratio of product tower F was changed to 0.1, and the distillate volume was changed to 20 parts. 80 parts of 1,3-butylene glycol product was obtained from the bottom of product tower F in the same manner as in Example 1. The initial boiling point of the obtained 1,3-butylene glycol product was 203.1 ° C, the dry point was 209.5 ° C, the water concentration was 0.2 wt%, the area ratio of 1,3-butylene glycol was 98.8%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.1%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 1.1%, the acetaldehyde content was 2 ppm, and the crotonaldehyde content was 1.3 ppm. The potassium permanganate test value was 30 minutes. The recovery rate of 1,3-butylene glycol in product tower F was 80%.

[0182] [Gas Chromatography Analysis] Gas chromatography analysis of the target 1,3-butylene glycol products was performed under the following conditions. A chart of the gas chromatography analysis of the 1,3-butylene glycol product in Example 1 is shown in Figure 2. A chart of the gas chromatography analysis of the 1,3-butylene glycol product in Example 12 is shown in Figure 3. Furthermore, a chart of the gas chromatography analysis of the 1,3-butylene glycol product in Comparative Example 2 is shown in Figure 4. (Gas chromatographic analysis conditions) Analytical equipment: Shimadzu GC2010 Analytical column: A column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) ("Agilent J&W GC Column - DB-1", manufactured by Agilent Technologies, Inc.) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction and temperature: Split sample introduction, 250°C Split gas flow rate and carrier gas: 23 mL / min, helium Column gas flow rate and carrier gas: 1 mL / min, helium Detector and temperature: Flame ionization detector (FID), 280°C Injected sample: 0.2 μL of 80 wt% 1,3-butylene glycol product aqueous solution

[0183] [Initial boiling point and dry point measurement] The test was carried out in accordance with the test method specified in the atmospheric distillation test method of JIS K2254 "Petroleum products - Distillation test method."

[0184] [Moisture measurement] The measurement was carried out using a Karl Fischer moisture content analyzer.

[0185] [GC-MS analysis] Analyzer: Agilent 6890A-GC / 5973A-MSD Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Ion source temperature: EI 230℃, CI 250℃ Q pole temperature: 150℃ Sample: Ready for analysis

[0186] [Potassium permanganate test] In this specification, the potassium permanganate test value (PMT) is a value measured in accordance with the procedure of the visual colorimetric method of JIS K1351 (1993).

[0187] [Coloration test 1 (coloration test 1)] The target 1,3-butylene glycol product was placed in a wide-mouth bottle, sealed, and held in a thermostatic chamber set at 180°C for 3 hours. Using a colorimeter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) and a quartz cell with a 10 mm optical path length, the Hazen color number (APHA) of the 1,3-butylene glycol product after 3 hours of holding at 180°C was measured. The Hazen color number (APHA) of the 1,3-butylene glycol product before the test was also measured in the same way. Furthermore, the contents of each impurity in the 1,3-butylene glycol product before and after Time-Dependent Coloration Test 1 were measured by the GC-MS analysis described above. The initial boiling point, dry point, potassium permanganate test value, odor, and acid content of the 1,3-butylene glycol product before and after Time-Dependent Coloration Test 1 were also measured.

[0188] [Coloration test 2 (coloration test 2)] The target 1,3-butylene glycol products were placed in wide-mouth bottles, which were then sealed and kept in a thermostatic chamber set to 100°C for 75 days. Using a colorimeter ("ZE6000" manufactured by Nippon Denshoku Industries Co., Ltd.) and a quartz cell with an optical path length of 10 mm, the Hazen color number (APHA) of the 1,3-butylene glycol products after 75 days of storage at 100°C was measured.

[0189] [Water addition heating test (acid concentration analysis)] The target 1,3-butylene glycol product was prepared into a 90 wt % aqueous solution, and after holding at 100°C for one week, the sample was subjected to acid concentration analysis using the following method. In addition, the acid concentration of the 1,3-butylene glycol product before the test was also analyzed using the following method. (Acid concentration analysis) Measurements were performed by potentiometric titration using an automatic potentiometric titrator (AT-510, manufactured by Kyoto Electronics Manufacturing Co., Ltd.). 50 g of sample was diluted with 50 g of distilled water, and while stirring, 0.01 N aqueous sodium hydroxide solution was titrated from a burette until the automatic end point stopped. The acid concentration (acid content) in terms of acetic acid was then calculated using the following formula: Acid concentration (wt%) = titration volume (ml) × F × A × (100 / sample volume (g)) F: 1.0 (factor of 0.01N sodium hydroxide solution) A: 0.0006 (the number of grams of acetic acid equivalent to 1 ml of sodium hydroxide solution)

[0190] [Odor test] The target 1,3-butylene glycol product (100 ml) was placed in a wide-mouth reagent bottle (internal volume: 100 ml), sealed, and left to stand at room temperature for a while (approximately 120 minutes), after which the stopper was opened and the bottle was transferred to a 300 ml wide-mouth beaker, and 100 ml of pure water was added to make a total of 200 ml. The bottle was then shaken by hand to mix, after which the odor was immediately smelled and scored according to the following evaluation criteria. Similar odor tests were also conducted on the samples after the above-mentioned Time-Dependent Coloration Test 1 and the samples after the above-mentioned Water-Added Heating Test. 1: No smell 2: Slight odor 3: You can clearly smell it

[0191] The above-mentioned coloration tests 1 and 2 and the water-added heating test are accelerated tests assuming long-term storage of 1,3BG products.

[0192] [Discussion of results] The results of the above comparative examples and examples are shown in Tables 1, 2 and 3.

[0193] [Table 1]

[0194] [Table 2]

[0195] [Table 3]

[0196] Many impurities are generated during the 1,3BG production process. The impurities generally contained in the 1,3BG product are listed in Table 3, although the impurities vary depending on the aldol condensation conditions, hydrogenation conditions, and subsequent purification conditions. The impurities contained in the 1,3BG product, such as acetaldol, crotonaldehyde, various carbonyl compounds, and alcohols, react with oxygen to generate peroxides during long-term storage. Aldehydes, in particular, generate peroxides more easily than ketones, alcohols, and hydrocarbons. Peroxides generated from impurities react with the product 1,3BG, promoting oxidation from the top of the tree (1,3BG) (see the impurity generation pathway diagram). Acetaldol is primarily produced by the dimerization of acetaldehyde. Therefore, by reducing a series of impurities in the reaction system and purification system, the concentration of peroxides generated from impurities during long-term storage can be suppressed, thereby suppressing the generation of many impurities via the oxidation of 1,3BG to 1-hydroxy-3-butanone, acetaldol, and further impurities generated from both of these compounds. For example, among the impurities shown in Table 3, substances generated by reaction with oxygen during long-term storage in the presence of oxygen include 1-hydroxy-3-butanone, acetaldol, 2-butanol, the compound represented by formula (8), the compound represented by formula (9), and the compound represented by formula (10). Other impurities are generated when 1-hydroxy-3-butanone or acetaldol is present with 1,3BG and other impurities, as well as a small amount of water.

[0197] The results of the comparative examples and examples show that, during long-term storage of 1,3BG, the greater the initial content (initial content) of acetaldehyde, crotonaldehyde, methyl vinyl ketone, acetone, formaldehyde, butylaldehyde, acetaldol, and 1-hydroxy-3-butanone in the 1,3BG product, the greater the overall content of impurities represented by formulas (1) to (10). Furthermore, in comparative examples 1 and 2, where the initial contents of acetaldehyde, crotonaldehyde, methyl vinyl ketone, acetone, formaldehyde, butylaldehyde, acetaldol, and 1-hydroxy-3-butanone were high and the impurities represented by formulas (1) to (10) increased after heating tests under specific conditions simulating long-term storage, the 1,3BG product's APHA, odor, initial boiling point, dry point, PMT, and acid content deteriorated significantly. On the other hand, in Examples 1, 7, 18, and 27, in which the initial contents of acetaldehyde, crotonaldehyde, methyl vinyl ketone, acetone, formaldehyde, butyraldehyde, acetaldol, and 1-hydroxy-3-butanone were low and the impurities represented by formulas (1) to (10) increased little or not at all after the heating test, the quality of the 1,3BG product was found to show little or no deterioration even after the heating test. In particular, going from Example 1 to Example 18 to Example 7 to Example 27, the contents of the impurities represented by formulas (1) to (10) after the heating test decreased overall, and the stability of the quality of the 1,3BG product also improved. These results indicate a correlation between the contents of the impurities represented by formulas (1) to (10) after the heating test and the deterioration of the quality of the 1,3BG product over time. It also shows that there is a certain correlation between the content (initial content) of acetaldehyde, crotonaldehyde, methyl vinyl ketone, acetone, formaldehyde, butylaldehyde, acetaldol, and 1-hydroxy-3-butanone in 1,3BG products and the content of impurities represented by formulas (1) to (10) in 1,3BG products after the heating test.

[0198] In summary, the configuration of the present disclosure and its variations are noted below. [1] A 1,3-butylene glycol product containing 1,3-butylene glycol, which has the following formula (A) or (B) after being kept at 180 ° C for 3 hours in an air atmosphere: [ka] (In the formula, R 1 ~R 4 are the same or different and are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be substituted with a hydroxyl group, or an alkenyl group having 2 to 4 carbon atoms which may be substituted with a hydroxyl group. 1,3-butylene glycol products in which the content of at least one of the compounds represented by the formula (I) is less than 8 ppm (or 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm). [2] The 1,3-butylene glycol product according to [1], wherein, after being kept at 180°C for 3 hours in an air atmosphere, the content of two compounds (or three compounds, four compounds, five compounds, six compounds, seven compounds, eight compounds, nine compounds, or ten compounds) among the compounds represented by formula (A) or (B) is less than 8 ppm (or 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm). [3] The 1,3-butylene glycol product according to [1], wherein the content of at least four (four, five, six, seven, eight, nine, or ten) compounds represented by formula (A) or (B) after being kept at 180°C for three hours in an air atmosphere is less than 8 ppm (or 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm). [4] The 1,3-butylene glycol product according to any one of [1] to [3] above, in which the total content of the compounds represented by formula (A) [or the total content of the compounds represented by the following formulas (1) to (7)] after being kept at 180°C for 3 hours in an air atmosphere is less than 66 ppm (or 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm). [5] The 1,3-butylene glycol product according to any one of [1] to [4] above, in which the sum of the contents of the compounds represented by formula (B) [or the sum of the contents of the compounds represented by the following formulas (8) to (10)] after being kept at 180°C for 3 hours in an air atmosphere is less than 31 ppm [or 25 ppm or less, 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 13 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm]. [6] The 1,3-butylene glycol product according to any one of [1] to [5], wherein the compound represented by (A) is any one of the compounds represented by the following formulas (1) to (7), and the compound represented by (B) is any one of the compounds represented by the following formulas (8) to (10): [ka] [7] The 1,3-butylene glycol product according to [6], wherein the total content of the compounds represented by the formulas (1) to (4) after being kept at 180°C for 3 hours in an air atmosphere is less than 34 ppm (or 30 ppm or less, 25 ppm or less, 20 ppm or less, 18 ppm or less, 16 ppm or less, 15 ppm or less, 14 ppm or less, 13 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm). [8] The 1,3-butylene glycol product according to [6] or [7], wherein the total content of the compounds represented by the formulas (5) to (10) after being kept at 180°C for 3 hours in an air atmosphere is less than 63 ppm (or 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm). [9] The 1,3-butylene glycol product according to any one of [6] to [8], wherein the total content of the compounds represented by the formulas (1) to (10) after being kept in an air atmosphere at 180°C for 3 hours is less than 97 ppm (or 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[10] After being kept at 180°C for 3 hours in an air atmosphere, the methyl vinyl ketone content is less than 8 ppm (or 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the 1-hydroxy-3-butanone content is less than 1 ppm (or 0.5 ppm or less), and / or the acetone content is less than 6 ppm (or 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the formaldehyde content is less than 2 ppm (or 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less). The 1,3-butylene glycol product according to any one of [1] to [9] above, wherein the content of crotonaldehyde is less than 1 ppm (or 0.5 ppm or less), and / or the content of acetaldol is less than 1 ppm (or 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the content of acetaldehyde is less than 5 ppm (or 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the content of butyraldehyde is less than 4 ppm (3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[11] The 1,3-butylene glycol product according to any one of [1] to

[10] above, in which the total content of methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, and acetaldehyde is less than 24 ppm (or 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after being kept at 180°C for 3 hours in an air atmosphere.

[12] The 1,3-butylene glycol product according to any one of [1] to

[11] above, in which the total content of methyl vinyl ketone, acetone, and butyraldehyde is less than 18 ppm (or 16 ppm or less, 15 ppm or less, 14 ppm or less, 13 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after being kept at 180°C for 3 hours in an air atmosphere.

[13] The 1,3-butylene glycol product according to any one of [1] to

[12] above, having an APHA of less than 79 (or 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, 25 or less, 20 or less, 18 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9 or less, 8 or less, or 7 or less) after being kept at 180°C for 3 hours in an air atmosphere.

[14] The 1,3-butylene glycol product according to any one of [1] to

[13] above, which has an initial boiling point of higher than 203°C (or 204°C or higher, 205°C or higher, 206°C or higher, 207°C or higher, or 208°C or higher) and / or a dry point of 209°C or lower after being kept at 180°C for 3 hours in an air atmosphere.

[15] The 1,3-butylene glycol product according to any one of [1] to

[14] , wherein the potassium permanganate test value after being kept at 180°C for 3 hours in an air atmosphere is 30 minutes or more (or more than 30 minutes, 32 minutes or more, 35 minutes or more, 40 minutes or more, 50 minutes or more, or 60 minutes or more).

[16] The 1,3-butylene glycol product according to any one of [1] to

[15] , having an acid concentration (as acetic acid) of less than 16 ppm (or 14 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) after being kept at 180°C for 3 hours in an air atmosphere.

[17] The 1,3-butylene glycol product according to any one of [1] to

[16] above, having a total content of 1-hydroxy-3-butanone and acetaldol of less than 19 ppm (or 18 ppm or less, 16 ppm or less, 14 ppm or less, 12 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) without undergoing a test of holding the product at 180°C for 3 hours in an air atmosphere.

[18] In a state that has not undergone a test of holding in an air atmosphere at 180°C for 3 hours, the content of methyl vinyl ketone is less than 10 ppm (or 8 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the content of 1-hydroxy-3-butanone is less than 9 ppm (or 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less). or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the acetone content is less than 9 ppm (or 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the formaldehyde content is less than 3 ppm (or 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm). less than 0.2 ppm), and / or the content of crotonaldehyde is less than 2 ppm (or 1.5 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the content of acetaldol is less than 10 ppm (or 8 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or the content of acetaldehyde is less than 10 ppm (or 8 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm). The 1,3-butylene glycol product according to any one of [1] to

[17] above, having a butyl aldehyde content of less than 4 ppm (or 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm), and / or a butyl aldehyde content of less than 8 ppm (or 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[19] The 1,3-butylene glycol product according to any one of [1] to

[18] above, in which the total content of methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, and acetaldehyde is less than 47 ppm (or 40 ppm or less, 30 ppm or less, 25 ppm or less, 20 ppm or less, 18 ppm or less, 16 ppm or less, 14 ppm or less, 13 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) when not subjected to a test in which the product is kept in an air atmosphere at 180°C for 3 hours.

[20] The 1,3-butylene glycol product according to any one of [1] to

[19] above, which has an acid concentration (acetic acid equivalent) of less than 11 ppm (or 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm) without undergoing a test in which the product is kept at 180°C for 3 hours in an air atmosphere.

[21] The 1,3-butylene glycol product according to any one of [1] to

[20] above, wherein, without undergoing a test in which the product is kept at 180°C for 3 hours in an air atmosphere, a 90% by weight aqueous solution of the 1,3-butylene glycol product is kept at 100°C for 1 week, and the acid concentration (as acetic acid) is less than 23 ppm (or 20 ppm or less, 19 ppm or less, 18 ppm or less, 17 ppm or less, 16 ppm or less, 15 ppm or less, 14 ppm or less, 13 ppm or less, 12 ppm or less, 11 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, 5 ppm or less, 4 ppm or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, or less than 0.2 ppm).

[22] The 1,3-butylene glycol product according to any one of the items [1] to

[21] , wherein, without undergoing a test in which the product is kept at 180°C for 3 hours in an air atmosphere, the acid concentration (as acetic acid) of a 90% by weight aqueous solution of the 1,3-butylene glycol product after being kept at 100°C for 1 week is such that the ratio of the acid concentration before the keep [(acid concentration after keeping at 100°C for 1 week) / (acid concentration before the keep)×100(%)] is 200% or less (or 150% or less, or 120% or less).

[23] The 1,3-butylene glycol product according to any one of [1] to

[22] above, which has an APHA of 6 or less (or 5 or less, 4 or less, 3 or less, or 2 or less) when not subjected to a test in which the product is kept at 180°C for 3 hours in an air atmosphere.

[24] The 1,3-butylene glycol product according to any one of [1] to

[23] above, having an APHA of 42 or less (or 35 or less, 30 or less, 25 or less, 20 or less, 18 or less, 16 or less, 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less) after being kept at 100°C for 75 days in an air atmosphere.

[25] The 1,3-butylene glycol product according to any one of [1] to

[24] , wherein the ratio of APHA after 75 days at 100°C to APHA before the holding [(APHA after 75 days at 100°C) / (APHA before the holding)] is 10 or less (or 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, or 3 or less).

[26] The 1,3-butylene glycol product according to any one of [1] to

[25] above, which has an initial boiling point of higher than 203°C (or 204°C or higher, 205°C or higher, 206°C or higher, 207°C or higher, or 208°C or higher) and / or a dry point of 209°C or lower, without undergoing a test in which the product is held at 180°C for 3 hours in an air atmosphere.

[27] The 1,3-butylene glycol product according to any one of [1] to

[26] above, which has a potassium permanganate test value of 30 minutes or more (or more than 30 minutes, 32 minutes or more, 35 minutes or more, 40 minutes or more, 50 minutes or more, or 60 minutes or more) without undergoing a test in which it is kept at 180°C for 3 hours in an air atmosphere.

[28] The 1,3-butylene glycol product according to any one of [1] to

[27] , wherein the content of 1,3-butylene glycol (GC area percentage under the GC analysis conditions below) is 98.6% or more (or 98.7% or more, 98.8% or more, 98.9% or more, 99.0% or more, 99.1% or more, 99.2% or more, 99.3% or more, 99.4% or more, 99.5% or more, 99.6% or more, 99.7% or more, or 99.8% or more). <Gas chromatography (GC) analysis conditions> Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[29] The 1,3-butylene glycol product according to any one of [1] to

[28] , wherein in the GC analysis, the total area ratio of peaks having shorter retention times than the peak of 1,3-butylene glycol is 0.28% or less (or 0.25% or less, 0.23% or less, 0.2% or less, 0.17% or less, 0.15% or less, 0.12% or less, 0.1% or less, 0.07% or less, 0.04% or less, 0.03% or less, 0.02% or less, 0.01% or less, 0.007% or less, 0.005% or less, or 0.002% or less).

[30] The 1,3-butylene glycol product according to any one of [1] to

[29] , wherein in the GC analysis, the total area ratio of peaks having a longer retention time than the peak of 1,3-butylene glycol is 1% or less (or 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less).

[31] The 1,3-butylene glycol product according to any one of [1] to

[30] , wherein the water content is less than 0.4% by weight (or 0.3% by weight or less, 0.2% by weight or less, 0.1% by weight or less, 0.07% by weight or less, 0.05% by weight or less, 0.03% by weight or less, 0.02% by weight or less, 0.01% by weight or less, or 0.005% by weight or less).

[32] A moisturizer containing the 1,3-butylene glycol product according to any one of [1] to

[31] above.

[33] The moisturizing agent according to

[32] , wherein the content of the 1,3-butylene glycol product according to any one of [1] to

[31] is 10% by weight or more (or 30% by weight or more, 50% by weight or more, 80% by weight or more, or 90% by weight or more).

[34] A cosmetic comprising the moisturizer according to

[32] or

[33] above.

[35] The cosmetic according to the above

[34] , wherein the content of the 1,3-butylene glycol product according to any one of the above [1] to

[31] is 0.01 to 40% by weight (or 0.1 to 30% by weight, 0.2 to 20% by weight, 0.5 to 15% by weight, or 1 to 10% by weight).

[36] The cosmetic according to

[34] or

[35] above, which is a skin cosmetic, a hair cosmetic, a sunscreen cosmetic, or a makeup cosmetic.

[37] A method for producing 1,3-butylene glycol, in which the 1,3-butylene glycol product according to any one of [1] to

[31] is obtained from a reaction crude liquid containing 1,3-butylene glycol, The process includes a dehydration process for removing water by distillation, a high-boiling point removal process for removing high-boiling components by distillation, and a product distillation process for obtaining purified 1,3-butylene glycol (1,3-butylene glycol product). In the product column used in the product distillation step, the acetaldehyde content is 500 ppm or less (or 205 ppm or less, 200 ppm or less, 150 ppm or less, 120 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, or less than 2 ppm), and the crotonaldehyde content is 200 ppm or less (or 150 ppm or less, 130 ppm or less, 110 ppm or less, 100 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, 2 ppm or less, or less than 1 ppm), water content is 0.7% by weight or less (or 0.6% by weight or less, 0.5% by weight or less, 0.4% by weight or less, 0.3% by weight or less, 0.2 % by weight or less, or 0.1% by weight or less), and the concentration of 1,3-butylene glycol as determined by gas chromatography analysis under the following conditions is 97.6 area% or more (or 97.8 area% or more, 98 area% or more, 98.2 area% or more, 98.4 area% or more, 98.6 area% or more, 98.8 area% or more, 99 area% or more, 99.1 area% or more, 99.2 area% or more, 99.3 area% or more, 99.4 area% or more, 99.5 area% or more, 99.6 area% or more, 99 1. A method for producing 1,3-butylene glycol, comprising distilling a 1,3-butylene glycol feed solution having a reflux ratio of 0.3 or more (or 0.4 or more, 0.5 or more, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 20 or more, 50 or more, 400 or more, or 500 or more) to obtain the 1,3-butylene glycol product. (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[38] A method for producing 1,3-butylene glycol, in which the 1,3-butylene glycol product according to any one of [1] to

[31] is obtained from a reaction crude liquid containing 1,3-butylene glycol, The method includes a dehydration step for removing water by distillation and a high boiling point removal step for removing high boiling point components by distillation, In the high boiling removal tower used in the high boiling removal step, the acetaldehyde content is 500 ppm or less (or 205 ppm or less, 200 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, less than 2 ppm, or less than 1 ppm), the crotonaldehyde content is 200 ppm or less (or 110 ppm or less, 100 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, 2 ppm or less, or less than 1 ppm), and the water content is 3% by weight or less (or 2% by weight or less). 1.2% by weight or less, 0.4% by weight or less, 0.3% by weight or less, 0.2% by weight or less, 0.1% by weight or less, 0.05% by weight or less, or 0.03% by weight or less), a 1,3-butylene glycol concentration of 96.7 area % or more (or 97% or more, 98% or more, or 99% or more) as determined by gas chromatography analysis under the following conditions, is subjected to distillation under conditions of a reflux ratio of 0.03 or more (or 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.2 or more, 0.4% by weight or less, 0.3% by weight or less, 0.2% by weight or less, 0.1% by weight or less, 0.05% by weight or less, or 0.03% by weight or less), (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C [Industrial Applicability]

[0199] The 1,3-butylene glycol product according to the present disclosure is highly pure and colorless and odorless (or nearly colorless and odorless), and is unlikely to develop or increase coloration or odor over time, and / or is unlikely to experience an increase in acid concentration over time even when containing water. This 1,3-butylene glycol product has excellent moisturizing properties and can be used as a raw material for moisturizers and cosmetics that can maintain high quality for a long period of time. [Explanation of symbols]

[0200] A: Dehydration tower B: Desalination tower C: High boiling point removal distillation column (high boiling point removal column) D: Alkaline reactor E: Dealkalization tower F: Product distillation column (product column) A-1, B-1, C-1, E-1, F-1: Condenser A-2, C-2, F-2: Reboiler X-1: Crude 1,3-butylene glycol X-2: Water (drainage) X-3: Salts, high boiling points, and some 1,3-butylene glycol X-4: High boiling point substances and part of 1,3-butylene glycol X-5: Caustic soda, high boiling point substances, and some 1,3-butylene glycol X-6: Low boiling point substances and part of 1,3-butylene glycol Y: 1,3-butylene glycol products

Claims

1. A 1,3-butylene glycol product containing 1,3-butylene glycol, which has a 1,3-butylene glycol content of the following formula (A) or (B) after being kept at 180°C for 3 hours in an air atmosphere: 【Chemical 1】 (In the formula, R 1 ~R 4 are the same or different and are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be substituted with a hydroxyl group, or an alkenyl group having 2 to 4 carbon atoms which may be substituted with a hydroxyl group. A 1,3-butylene glycol product in which the content of at least one of the compounds represented by the formula (I) is less than 8 ppm.

2. 2. The 1,3-butylene glycol product according to claim 1, wherein the total content of the compounds represented by formula (A) after being kept at 180° C. for 3 hours in an air atmosphere is less than 66 ppm.

3. 3. The 1,3-butylene glycol product according to claim 1, wherein the total content of the compounds represented by formula (B) after being kept at 180° C. for 3 hours in an air atmosphere is less than 31 ppm.

4. The 1,3-butylene glycol product according to any one of claims 1 to 3, wherein the compound represented by formula (A) is any one of compounds represented by the following formulas (1) to (7), and the compound represented by formula (B) is any one of compounds represented by the following formulas (8) to (10): 【Chemistry 2】

5. 5. The 1,3-butylene glycol product according to claim 4, wherein the total content of the compounds represented by the formulas (1) to (4) after being kept at 180° C. for 3 hours in an air atmosphere is less than 34 ppm.

6. The 1,3-butylene glycol product according to claim 4 or 5, wherein the total content of the compounds represented by the formulas (5) to (10) after being kept at 180°C for 3 hours in an air atmosphere is less than 63 ppm.

7. The 1,3-butylene glycol product according to any one of claims 4 to 6, wherein the total content of the compounds represented by the formulas (1) to (10) after being kept at 180°C for 3 hours in an air atmosphere is less than 97 ppm.

8. The 1,3-butylene glycol product according to any one of claims 1 to 7, which, after being kept in an air atmosphere at 180°C for 3 hours, has a methyl vinyl ketone content of less than 8 ppm, and / or a 1-hydroxy-3-butanone content of less than 1 ppm, and / or an acetone content of less than 6 ppm, and / or a formaldehyde content of less than 2 ppm, and / or a crotonaldehyde content of less than 1 ppm, and / or an acetaldol content of less than 1 ppm, and / or an acetaldehyde content of less than 5 ppm, and / or a butyraldehyde content of less than 4 ppm.

9. The 1,3-butylene glycol product according to any one of claims 1 to 8, wherein after being kept at 180°C for 3 hours in an air atmosphere, the total content of methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, and acetaldehyde is less than 24 ppm.

10. The 1,3-butylene glycol product according to any one of claims 1 to 9, wherein the total content of methyl vinyl ketone, acetone, and butyraldehyde is less than 18 ppm after being kept at 180°C for 3 hours in an air atmosphere.

11. The 1,3-butylene glycol product according to any one of claims 1 to 10, which has an APHA of less than 79 after being kept at 180°C for 3 hours in an air atmosphere.

12. The 1,3-butylene glycol product according to any one of claims 1 to 11, which has an initial boiling point higher than 203°C and / or a dry point lower than 209°C after being kept at 180°C for 3 hours in an air atmosphere.

13. 13. The 1,3-butylene glycol product according to any one of claims 1 to 12, which has a potassium permanganate test value of 30 minutes or more after being kept at 180°C for 3 hours in an air atmosphere.

14. The 1,3-butylene glycol product according to any one of claims 1 to 13, which has an acid concentration (as acetic acid) of less than 16 ppm after being kept at 180°C for 3 hours in an air atmosphere.

15. The 1,3-butylene glycol product according to any one of claims 1 to 14, having a total content of 1-hydroxy-3-butanone and acetaldol of less than 19 ppm when not subjected to a test of holding the product at 180°C for 3 hours in an air atmosphere.

16. The 1,3-butylene glycol product according to any one of claims 1 to 15, which, without undergoing a test of maintaining the product in an air atmosphere at 180°C for 3 hours, has a methyl vinyl ketone content of less than 10 ppm, and / or a 1-hydroxy-3-butanone content of less than 9 ppm, and / or an acetone content of less than 9 ppm, and / or a formaldehyde content of less than 3 ppm, and / or a crotonaldehyde content of less than 2 ppm, and / or an acetaldol content of less than 10 ppm, and / or an acetaldehyde content of less than 4 ppm, and / or a butyraldehyde content of less than 8 ppm.

17. The 1,3-butylene glycol product according to any one of claims 1 to 16, wherein the total content of methyl vinyl ketone, 1-hydroxy-3-butanone, acetone, formaldehyde, crotonaldehyde, acetaldol, and acetaldehyde is less than 47 ppm when the product is not subjected to a test of holding the product at 180°C for 3 hours in an air atmosphere.

18. A moisturizer comprising the 1,3-butylene glycol product of any one of claims 1 to 17.

19. A cosmetic comprising the moisturizing agent according to claim 18.

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