Dipropylene glycol-containing composition and cosmetic

Abstract

Provided is a dipropylene glycol-containing composition containing 90 mass% or more of dipropylene glycol, wherein the 1,3-dimethyl-2-imidazolidinone content is 0.1-5.0 mass ppm, the methyl acetate content is 0.1-100 mass ppm, the isobutyl aldehyde content is 0.1-10 mass ppm, and the ethyl isobutyrate content is 0.1-50 mass ppm with respect to 100 mass% of the total mass of the dipropylene glycol-containing composition.

Description

Dipropylene glycol-containing composition and cosmetics

[0001] The present invention relates to a dipropylene glycol (hereinafter sometimes referred to as "DPG")-containing composition and cosmetics, and particularly to a DPG-containing composition with reduced odor after long-term storage and cosmetics containing the DPG-containing composition.

[0002] DPG is produced, for example, by the production methods described in Patent Documents 1 to 3. DPG produced by the production methods described in Patent Documents 1 to 3 is used as a glycol component for imparting toughness to unsaturated polyester resins; a glycol component of benzoic acid ester plasticizers; a cosmetic raw material; etc.

[0003] International Publication No. 2013 / 111839, Japanese Patent Application Laid-Open No. 2004-115404, Chinese Patent Application Publication No. 114716299 Specification

[0004] Although DPG produced by the production methods described in Patent Documents 1 and 2 is almost odorless immediately after production, it may generate a peculiar odor after long-term storage, and there is a problem that it is difficult to use as a cosmetic raw material. Further, Patent Document 3 describes that propylene glycol, DPG and tripropylene glycol were obtained by continuous rectification in a 4-column rectification column, and it is described that propylene glycol and tripropylene glycol were odorless. However, there is no disclosure that odorless DPG was obtained. From the above, in DPG used as a cosmetic raw material, DPG with suppressed odor generation even after long-term storage has been strongly desired.

[0005] The present invention has been made in view of such a situation, and an object thereof is to provide a DPG-containing composition with reduced odor after long-term storage and cosmetics containing the DPG-containing composition.

[0006] This invention is based on the discovery that by identifying and addressing odor-causing substances and their causes, a DPG-containing composition with reduced odor after long-term storage and cosmetics containing the DPG-containing composition can be obtained. The inventors found that when the quality of the water used in the production of the DPG-containing composition is low (high number of specific algae), the resulting DPG-containing composition is more likely to develop an odor after long-term storage, while when the quality of the water used in the production of the DPG-containing composition is high (low number of specific algae), the odor after long-term storage of the resulting DPG-containing composition is reduced.

[0007] The present invention provides the following means: [1] A dipropylene glycol-containing composition comprising 90% by mass or more of dipropylene glycol, wherein, per 100% by mass of the total mass of the dipropylene glycol-containing composition, the content of 1,3-dimethyl-2-imidazolidinone is 0.1 to 5.0 ppm by mass, the content of methyl acetate is 0.1 to 100 ppm by mass, the content of isobutyraldehyde is 0.1 to 10 ppm by mass, and the content of ethyl isobutyrate is 0.1 to 50 ppm by mass. [2] A cosmetic comprising the dipropylene glycol-containing composition described in [1] above.

[0008] This embodiment provides a DPG-containing composition with reduced odor after long-term storage, and cosmetics containing the DPG-containing composition.

[0009] The definitions and meanings of terms and notations used in this specification are given below. Numerical ranges expressed using "~" mean that the numbers before and after "~" are the lower and upper limits. For numerical ranges (e.g., ranges of content, etc.), the lower and upper limits described in steps may be combined independently. The lower and upper limits of a numerical range may be replaced with the numbers described in the examples. For example, from the description "preferably 10 to 90, more preferably 30 to 60", the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to become "10 to 60". Also, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. "Main component" means 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 97% by mass or more. The "content of 1,3-dimethyl-2-imidazolidinone per 100% by mass of the total mass of the DPG-containing composition," the "content of methyl acetate per 100% by mass of the total mass of the DPG-containing composition," the "content of isobutyraldehyde per 100% by mass of the total mass of the DPG-containing composition," and the "content of ethyl isobutyrate per 100% by mass of the total mass of the DPG-containing composition" were measured using a gas chromatograph-mass spectrometer (GC-MS) (GC analyzer: Agilent 8890, mass spectrometer: Agilent quadrupole MS 5977B, ionization method: EI+, carrier gas: He), and more specifically, the values ​​were measured under the same conditions as in the examples described later. The "content of water per 100% by mass of the total mass of the DPG-containing composition" was measured using a moisture content measuring device CA-310 (manufactured by Nitto Seikou Analytech Co., Ltd.). The number of aphanizomenon (algae) in the "water used during the synthesis of the DPG-containing composition (used water)" was measured using the same method as in the examples described later.

[0010] [DPG-containing composition] The DPG-containing composition of this embodiment (hereinafter referred to as "this embodiment") contains DPG, 1,3-dimethyl-2-imidazolidinone, methyl acetate, isobutyraldehyde, and ethyl isobutyrate as essential components, and may further contain optional components. The DPG-containing composition of this embodiment can reduce odor after long-term storage. There are no particular restrictions on the method for producing the DPG-containing composition, but for example, the hydration method of propylene oxide (PO) is preferred.

[0011] <Hydration Method of Propylene Oxide (PO)> The hydration method of propylene oxide (PO) is a representative commercial production technology for producing propylene glycol (PG), and includes a hydration reaction step in which PO and water are used as raw materials and a hydration reaction is carried out without a catalyst. A portion of the PG produced in the hydration reaction step reacts sequentially with PO to produce DPG and tripropylene glycol (TPG). The reaction solution (first crude solution) obtained in the hydration reaction step contains excess water, so the water is removed by distillation (water removal step) to obtain a second crude solution, and then the purity of the DPG is increased in a distillation purification step. Another embodiment of the present invention is a method for producing DPG that includes a hydration step for hydrating PO, wherein the average number of algae in the water used in the hydration step is 180 or less. Another embodiment of the present invention is a method for producing DPG that further includes a distillation purification step for distilling and purifying the obtained DPG, and it is preferable to introduce a low-boiling point substance when carrying out the distillation purification step.

[0012] By introducing a low-boiling point substance during the distillation and purification process, the purity of DPG in a DPG-containing composition can be efficiently improved. The low-boiling point substance is not particularly limited as long as its boiling point is 100°C or lower; examples include liquids such as organic solvents and water, and gases such as nitrogen. These may be used individually or in combination of two or more. Among these, water is preferred from the viewpoint of economy and ease of handling.

[0013] <Water used during the synthesis of the DPG-containing composition (used water)> "Water used during the synthesis of the DPG-containing composition (used water)" means "water used in the hydration reaction step," "water removed in the water removal step," and / or "water used in the distillation purification step." The "water used in the hydration reaction step," "water removed in the water removal step," and "water used in the distillation purification step" may be the same or different. There are no particular restrictions on the number of aphanizomenon (algae) in the "water used during the synthesis of the DPG-containing composition (used water)," but it is preferably 180 or less, more preferably 150 or less, and particularly preferably 50 or less. If the number of aphanizomenon (algae) in the used water is below the upper limit, the content of 1,3-dimethyl-2-imidazolidinone in the DPG-containing composition can be reduced.

[0014] <DPG> The DPG content of the DPG-containing composition of this embodiment is not particularly limited as long as it is 90% by mass or more relative to 100% by mass of the total mass, but is preferably 95% by mass or more, more preferably 97% by mass or more, and particularly preferably 99% by mass or more. When the DPG content is above the lower limit, the texture performance in cosmetics can be improved.

[0015] In particular, as a method for purifying crude DPG to obtain a DPG-containing composition that can be used as a cosmetic ingredient, examples include a method of removing PG and TPG from the reaction product by distillation using a known method, or a method of performing one or more known purification steps on the fraction after removing PG and TPG, and the known purification steps may be repeated. Examples of known purification methods include a distillation step to remove high-boiling components; a distillation step in which water is introduced from the top of the column and DPG is extracted from the bottom of the column; a step of mixing water and crude DPG and evaporating the water to obtain DPG; a step of extracting impurities with an organic solvent (e.g., pentane, hexane, toluene, etc.); and so on.

[0016] The DPG-containing composition of this embodiment, which contains DPG as its main component, has little odor after long-term storage and is suitable as a raw material for cosmetic applications such as moisturizers.

[0017] <1,3-Dimethyl-2-Imidazolidinone> The 1,3-dimethyl-2-imidazolidinone contained in the DPG-containing composition of this embodiment is an odor-generating substance that causes the generation of odor-causing substances such as methyl acetate, isobutyraldehyde, and ethyl isobutyrate, which will be described later. The content of 1,3-dimethyl-2-imidazolidinone in the DPG-containing composition of this embodiment is not particularly limited as long as it is between 0.1 and 5.0 ppm by mass, but is preferably between 0.2 and 4.0 ppm by mass, more preferably between 0.2 and 3.0 ppm by mass, and particularly preferably between 0.3 and 2.0 ppm by mass. If the content of 1,3-dimethyl-2-imidazolidinone is above the lower limit, the number of steps in the production of the DPG-containing composition can be reduced, improving productivity and economic efficiency, while if it is below the upper limit, the generation of odor-causing substances can be reduced.

[0018] <Odor Substances> The odor substances contained in the DPG-containing composition of this embodiment are thought to cause the odor of the DPG-containing composition to be perceived in sensory evaluation. Examples of odor substances include methyl acetate, isobutyraldehyde, and ethyl isobutyrate. There are no particular restrictions on the content of odor substances relative to 100% of the total mass of the DPG-containing composition of this embodiment, but it is preferably 0.3 to 200 ppm by mass, more preferably 0.3 to 100 ppm by mass, and particularly preferably 0.3 to 20 ppm by mass. If the content of odor substances is above the lower limit, the number of steps in the production of the DPG-containing composition can be reduced, improving productivity and economic efficiency. On the other hand, if it is below the upper limit, the odor of the DPG-containing composition can be reduced.

[0019] <Methyl Acetate> The methyl acetate contained in the DPG-containing composition of this embodiment is an odorous substance generated due to 1,3-dimethyl-2-imidazolidinone, which is an odor-generating substance. The content of methyl acetate in the DPG-containing composition of this embodiment is not particularly limited as long as it is between 0.1 and 100 ppm by mass, but is preferably between 0.1 and 50 ppm by mass, more preferably between 0.1 and 10 ppm by mass, and particularly preferably between 0.1 and 5.0 ppm by mass. If the methyl acetate content is above the lower limit, the number of steps in the production of the DPG-containing composition can be reduced, improving productivity and economic efficiency, while if it is below the upper limit, the odor of the DPG-containing composition can be reduced.

[0020] <Isobutyraldehyde> The isobutyraldehyde contained in the DPG-containing composition of this embodiment is an odorous substance generated due to 1,3-dimethyl-2-imidazolidinone, which is an odor-generating substance. The content of isobutyraldehyde in the DPG-containing composition of this embodiment is not particularly limited as long as it is between 0.1 and 10 ppm by mass, but is preferably between 0.1 and 5.0 ppm by mass, more preferably between 0.1 and 1.0 ppm by mass, and especially preferably between 0.1 and 0.5 ppm by mass. If the isobutyraldehyde content is above the lower limit, the number of steps in the production of the DPG-containing composition can be reduced, improving productivity and economic efficiency, while if it is below the upper limit, the odor of the DPG-containing composition can be reduced.

[0021] <Ethyl Isobutyrate> The ethyl isobutyrate contained in the DPG-containing composition of this embodiment is an odorous substance generated due to 1,3-dimethyl-2-imidazolidinone, which is an odor-generating substance. The content of ethyl isobutyrate in the DPG-containing composition of this embodiment is not particularly limited as long as it is between 0.1 and 50 ppm by mass, but is preferably between 0.1 and 10 ppm by mass, more preferably between 0.1 and 5.0 ppm by mass, and particularly preferably between 0.1 and 1.0 ppm by mass. If the content of ethyl isobutyrate is above the lower limit, the number of steps in the production of the DPG-containing composition can be reduced, improving productivity and economic efficiency, while if it is below the upper limit, the odor of the DPG-containing composition can be reduced.

[0022] <Water> There are no particular restrictions on the water content relative to 100% of the total mass of the DPG-containing composition of this embodiment, but it is preferably 30 ppm by mass or less, more preferably 20 ppm by mass or less, and particularly preferably 5 ppm by mass or less. When the water content is below the upper limit, the number of specific algae (aphanizomenon) contained in the water can be reduced, thereby stably reducing odor over a long period of time.

[0023] The DPG-containing composition of this embodiment may contain other components besides the above-mentioned components (1,3-dimethyl-2-imidazolidinone, methyl acetate, isobutyraldehyde, ethyl isobutyrate, and water). There are no particular limitations on the other components, and examples include acetaldehyde and acetic acid. There are no particular limitations on the content of the other components relative to 100% of the total mass of the DPG-containing composition of this embodiment, but it is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, and particularly preferably 0.5% by mass or less.

[0024] [Cosmetics] The cosmetics of this embodiment contain the DPG-containing composition of this embodiment as an essential component, and further contain 1,3-butanediol, glycerin, etc. as optional components.

[0025] There are no particular restrictions on what constitutes a cosmetic product. Examples include lotions, texture enhancers, and moisturizers for maintaining skin moisture and freshness; and shampoos for cleansing hair and body. These can be used individually or in combination of two or more.

[0026] The present invention will be specifically described below based on examples. The present invention is not limited to the following examples, and various modifications are possible without departing from the spirit of the invention.

[0027] Table 1 shows the "measurement results of the number of aphanizomenon (algae) in the water used during the synthesis of the DPG-containing composition," the "odor sensory evaluation results of the water used during the synthesis of the DPG-containing composition," the "odor sensory evaluation results of the DPG-containing composition," and the "GC-MS measurement results of the content of odor-generating substances and odor-causing substances in the DPG-containing composition" for Examples 1 to 6. Examples 1 and 2 are examples, and Examples 3, 4, 5, and 6 are comparative examples.

[0028] Details of each evaluation item are as follows: <Method for measuring the number of aphanizomenon (algae) in the water used during the synthesis of DPG-containing composition> A sample of water was collected, and the collected sample water was dropped onto a slide glass (manufactured by Matsunami Glass Industry Co., Ltd., product name: Boundary slide glass). The algae on the slide glass were observed under a microscope, and the number of algal individuals was counted. This process was repeated three times, and the average number was taken as the number of individuals.

[0029] <Odor Sensory Evaluation of Water Used in the Synthesis of DPG-Containing Compositions> The odor sensory evaluation of water used in the synthesis of DPG-containing compositions was performed according to the evaluation criteria below, and scores were assigned based on the relative evaluation. The evaluation samples were placed in wide-mouth reagent bottles with stoppers, sealed tightly, and left to stand at room temperature. After that, the odors were quickly smelled in the air, compared, and scored. The evaluation was performed by five adults, and the average score was adopted. <<Evaluation Criteria>> 1: No odor detected 2: Very slight odor detected 3: Slight odor detected 4: Odor detected 5: Strong odor detected Note that the difference between "1: No odor detected" and "2: Very slight odor detected" is whether or not an odor different from that of the air is detected, and the same applies below. If cosmetic raw materials emit even a slight odor, it may impair the palatability of the product. Therefore, in the odor sensory evaluation of the DPG-containing compositions below, "1: No odor detected" is preferable.

[0030] <Odor Sensory Evaluation of DPG-Containing Compositions> The odor sensory evaluation of DPG-containing compositions after storage stability testing (50°C for 8 weeks) was performed according to the evaluation criteria below, and scores were assigned based on the relative evaluation. The evaluation samples were placed in wide-mouth reagent bottles with stoppers, sealed tightly, and left to stand at room temperature. After that, the odors were quickly smelled in the air, compared, and scored. The evaluation was performed by five adults, and the average score was adopted. <<Evaluation Criteria>> 1: No odor detected 2: Very slight odor detected 3: Slight odor detected 4: Odor detected 5: Strong odor detected

[0031] <GC-MS measurement of the content of odor-generating substances and odor-causing substances in DPG-containing compositions> GC-MS measurement of the content of odor-generating substances and odor-causing substances in DPG-containing compositions was performed under the conditions shown below. <<Pretreatment (heat collection) conditions>> SPME fiber (50 / 30 DVB / CAR / PDMS) 5g collected in a 20mL vial <<GC conditions>> INJ temperature: 240℃ Column: DB-1301 (60m, 0.25mm, 1μm) Oven: 40℃ (5 min) → Increase temperature to 200℃ at 5℃ / min → Increase temperature to 240℃ at 20℃ / min MS: 240℃ <> MS Hunter Wiley 8th / NIST, odor library <<Collection conditions>> Fiber preheating: 150℃ 10 min Sample stirring: 40℃ 10 min Extraction time: 40℃ 5 min Internal standard 1,3-dimethyl-2-imidazolidinone Pure Chemical Co., Ltd. Special Grade

[0032] (Example 1) Hydration reaction step: Using 250 g of PO and 750 g of "distilled water (10 aphanizomenon (algae) cells / mL, odor sensory evaluation result 1.0)" as raw materials, a hydration reaction was carried out without a catalyst at 200°C and a pressure of 1.4 MPaG to obtain crude liquid 1 containing PG, DPG, and TPG. Water removal step: The obtained crude liquid 1 was distilled at 120°C and -0.09 MPaG to remove DPG, PG, TPG, and water to obtain crude liquid 2. Distillation purification step: The obtained crude liquid 2 was purified by distillation at 160°C and -0.09 MPaG to obtain DPG-containing composition 1. The distilled water used in the hydration reaction step was used for the distillation purification. The content of 1,3-dimethyl-2-imidazolidinone in DPG-containing composition 1, relative to 100% of the total mass, was 0.3 ppm by mass initially (immediately after synthesis) and 3.3 ppm by mass after the storage stability test (50°C for 8 weeks). The content of methyl acetate in DPG-containing composition 1, relative to 100% of the total mass, was 0.1 ppm by mass initially (immediately after synthesis) and 1.4 ppm by mass after the storage stability test (50°C for 8 weeks). The content of isobutyraldehyde in DPG-containing composition 1, relative to 100% of the total mass, was 0.1 ppm by mass initially (immediately after synthesis) and 0.1 ppm by mass after the storage stability test (50°C for 8 weeks). The content of ethyl isobutyrate in DPG-containing composition 1, relative to 100% of the total mass, was 0.1 ppm by mass initially (immediately after synthesis) and 0.3 ppm by mass after the storage stability test (50°C for 8 weeks). The odor sensory evaluation result after the storage stability test (50°C for 8 weeks) of DPG-containing composition 1 was 1.0 (no odor detected). The DPG content of DPG-containing composition 1 relative to 100% of the total mass was 100% by mass both initially (immediately after synthesis) and after the storage stability test (50°C for 8 weeks).

[0033] (Example 2) DPG-containing composition 2 was obtained in the same manner as in Example 1, except that in the distillation purification process, "ion-exchanged water (140 aphanizomenon (algae) particles / mL)" was used instead of "distilled water (10 aphanizomenon (algae) particles / mL, odor sensory evaluation result 1.0)". The content of 1,3-dimethyl-2-imidazolidinone in DPG-containing composition 2 per 100% of total mass was 0.3 ppm by mass initially (immediately after synthesis) and 2.6 ppm by mass after the storage stability test (50°C for 8 weeks). The content of methyl acetate in DPG-containing composition 2 per 100% of total mass was 0.1 ppm by mass initially (immediately after synthesis) and 0.7 ppm by mass after the storage stability test (50°C for 8 weeks). The content of isobutyraldehyde in DPG-containing composition 2, relative to 100% of the total mass, was 0.1 ppm by mass initially (immediately after synthesis) and 0.1 ppm by mass after the storage stability test (8 weeks at 50°C). The content of ethyl isobutyrate in DPG-containing composition 2, relative to 100% of the total mass, was 0.4 ppm by mass initially (immediately after synthesis) and 0.8 ppm by mass after the storage stability test (8 weeks at 50°C). The odor sensory evaluation result for DPG-containing composition 2 after the storage stability test (8 weeks at 50°C) was 1.0 (no odor detected). The content of DPG in DPG-containing composition 2, relative to 100% of the total mass, was 100% by mass both initially (immediately after synthesis) and after the storage stability test (8 weeks at 50°C).

[0034] (Example 3) DPG-containing composition 3 was obtained in the same manner as in Example 1, except that in the distillation purification process, "odorous ion-exchanged water (4500 aphanizomenon (algae) particles / mL, odor sensory evaluation result 5.0)" was used instead of distilled water. The content of 1,3-dimethyl-2-imidazolidinone in DPG-containing composition 3 per 100% of total mass was 81.3 ppm by mass initially (immediately after synthesis) and 132.8 ppm by mass after the storage stability test (50°C for 8 weeks). The content of methyl acetate in DPG-containing composition 3 per 100% of total mass was 159.5 ppm by mass initially (immediately after synthesis) and 241.6 ppm by mass after the storage stability test (50°C for 8 weeks). The content of isobutyraldehyde in DPG-containing composition 3, relative to 100% of the total mass, was 37.7 ppm by mass initially (immediately after synthesis) and 60.1 ppm by mass after the storage stability test (8 weeks at 50°C). The content of ethyl isobutyrate in DPG-containing composition 3, relative to 100% of the total mass, was 84.7 ppm by mass initially (immediately after synthesis) and 257.6 ppm by mass after the storage stability test (8 weeks at 50°C). The odor sensory evaluation result for DPG-containing composition 3 after the storage stability test (8 weeks at 50°C) was 5.0 (strongly noticeable odor). The content of DPG in DPG-containing composition 3, relative to 100% of the total mass, was 100% by mass both initially (immediately after synthesis) and after the storage stability test (8 weeks at 50°C).

[0035] (Example 4) DPG-containing composition 4 was obtained in the same manner as in Example 1, except that odorous ion-exchanged water (2000 aphanizomenon (algae) particles / mL, odor sensory evaluation result 3.0) was used instead of distilled water in the distillation purification process. The content of 1,3-dimethyl-2-imidazolidinone in DPG-containing composition 4 per 100% of total mass was 60.5 ppm by mass initially (immediately after synthesis) and 100.5 ppm by mass after the storage stability test (50°C for 8 weeks). The content of methyl acetate in DPG-containing composition 4 per 100% of total mass was 140.3 ppm by mass initially (immediately after synthesis) and 222.4 ppm by mass after the storage stability test (50°C for 8 weeks). The content of isobutyraldehyde in DPG-containing composition 4, relative to 100% of the total mass, was 26.8 ppm by mass initially (immediately after synthesis) and 47.7 ppm by mass after the storage stability test (8 weeks at 50°C). The content of ethyl isobutyrate in DPG-containing composition 4, relative to 100% of the total mass, was 157.3 ppm by mass initially (immediately after synthesis) and 304.4 ppm by mass after the storage stability test (8 weeks at 50°C). The odor sensory evaluation result for DPG-containing composition 4 after the storage stability test (8 weeks at 50°C) was 3.0 (slightly noticeable odor). The content of DPG in DPG-containing composition 4, relative to 100% of the total mass, was 100% by mass both initially (immediately after synthesis) and after the storage stability test (8 weeks at 50°C).

[0036] (Example 5) DPG-containing composition 5 was obtained in the same manner as in Example 1, except that odorous ion-exchanged water (200 aphanizomenon (algae) particles / mL, odor sensory evaluation result 1.0) was used instead of distilled water in the distillation purification process. The content of 1,3-dimethyl-2-imidazolidinone in DPG-containing composition 5 per 100% of total mass was 5.8 ppm by mass initially (immediately after synthesis) and 191.4 ppm by mass after the storage stability test (50°C for 8 weeks). The content of methyl acetate in DPG-containing composition 5 per 100% of total mass was 0.1 ppm by mass initially (immediately after synthesis) and 312.8 ppm by mass after the storage stability test (50°C for 8 weeks). The content of isobutyraldehyde in DPG-containing composition 5, relative to 100% of the total mass, was 0.1 ppm by mass initially (immediately after synthesis) and 0.1 ppm by mass after the storage stability test (8 weeks at 50°C). The content of ethyl isobutyrate in DPG-containing composition 5, relative to 100% of the total mass, was 0.1 ppm by mass initially (immediately after synthesis) and 2.8 ppm by mass after the storage stability test (8 weeks at 50°C). The odor sensory evaluation result for DPG-containing composition 5 after the storage stability test (8 weeks at 50°C) was 2.0 (very slight odor was perceptible). The content of DPG in DPG-containing composition 5, relative to 100% of the total mass, was 100% by mass both initially (immediately after synthesis) and after the storage stability test (8 weeks at 50°C).

[0037] (Example 6) Dipropylene glycol was obtained by the method described in Patent Document 2 (Japanese Patent Publication No. 2004-115404). Specifically, dipropylene glycol (DPG-containing composition 6) was obtained as follows: 50 g of dipropylene glycol (isomer mixture, grade: chemical), 50 g of water, and 50 g of cyclohexane were placed in a 500 mL separable flask and stirred at 400 rpm at 50°C for 10 minutes, then allowed to stand for 5 minutes to separate into an aqueous layer and an organic layer. The internal temperature of the separable flask at that time was 50°C. Another 50 g of cyclohexane was added to the separated aqueous layer, and the same operation was repeated twice. The obtained aqueous layer was dehydrated and concentrated in an oil bath at 130°C and 6.7 kPa for 30 minutes to obtain 42 g of dipropylene glycol (DPG-containing composition 6). The content of 1,3-dimethyl-2-imidazolidinone in DPG-containing composition 6 was 5.9 ppm by mass relative to 100% by mass of the total mass.

[0038]

[0039] Table 1 shows that, in the DPG-containing compositions of Examples 1 and 2, where the content of 1,3-dimethyl-2-imidazolidinone is 0.1 to 5.0 ppm by mass, the content of methyl acetate is 0.1 to 100 ppm by mass, the content of isobutyraldehyde is 0.1 to 10 ppm by mass, and the content of ethyl isobutyrate is 0.1 to 50 ppm by mass per 100% by mass of the total mass of the DPG-containing composition containing 90% by mass or more of dipropylene glycol, the odor after long-term storage was reduced.

[0040] The DPG-containing composition of this embodiment can be used in cosmetic applications, industrial product applications, household product applications, pharmaceutical applications, and the like.

Claims

1. A dipropylene glycol-containing composition comprising 90% by mass or more of dipropylene glycol, wherein, per 100% by mass of the total mass of the dipropylene glycol-containing composition, the content of 1,3-dimethyl-2-imidazolidinone is 0.1 to 5.0 ppm by mass, the content of methyl acetate is 0.1 to 100 ppm by mass, the content of isobutyraldehyde is 0.1 to 10 ppm by mass, and the content of ethyl isobutyrate is 0.1 to 50 ppm by mass.

2. A cosmetic comprising the dipropylene glycol-containing composition described in claim 1.

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