JPH11193213A - Composition for cleansing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition for cleansing, capable of rapidly removing a cosmetic soil, manifesting high cleansing ability, having high stability, readily used and excellent in massaging properties, washing-away properties and sense of use. SOLUTION: This composition for cleansing comprises (A) 0.05-5 wt.% anionic surfactant, 0.1-5 wt.% nonionic surfactant having >=9 HLB, 70-90 wt.% oil containing 40-100 wt.% silicone oil, 0.5-29 wt.% alcohols and 0.1-29 wt.% water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in permeability to skin details, has a quick release of dirt against make-up stains, shows high cleaning performance, has high stability, and has massage properties, washability and use. The present invention relates to a cleansing composition having a good feeling.

[0002]

2. Description of the Related Art Recent makeup cosmetics are water-resistant,
It is highly functional for the purpose of sebum resistance and long lasting makeup, and contains a large amount of solid fat, silicone-based, fluorine-based polymers, pigments, etc., which enhances the adhesion to the skin. It is hard to drop. Conventionally, cleansing compositions used to remove makeup cosmetics include oil-in-water or water-in-oil type cleansing creams and gel-type cleansing surfactant-in-oil type emulsions (JP-A-6-16523, JP-A-6-16524) and the like are known. However, these cleansing compositions are mainly blended with a hydrocarbon oil such as liquid paraffin or an ester oil such as triglyceride as a cleaning component, and have a satisfactory cleaning performance against makeup stains as described above. It was not shown. As a solution, a large amount of low-viscosity silicone oil having high permeability and dispersibility with respect to makeup stains can be considered. However, it has been difficult to stably blend a large amount of such a silicone oil into a product.

[0003] Conventional cleansing creams and gel-like cleansings have a detergency, so that after applying them, a sufficient amount of massage is applied to break the emulsified particles and at the same time evaporate the water, so that the oil is stained. It is necessary to remove the dirt, it takes a long time for the dirt to float, and there is a problem that the makeup removal is completed without sufficiently removing the dirt.

[0004] On the other hand, as a cleansing composition which has a high degree of soil release and high detergency, there is a cleansing oil composed of an oil component (JP-A-63-10710 and JP-A-1-211513). Since the cleansing oil is in the form of a liquid, if an oil agent having good compatibility is selected, it does not separate and has no stability problem, and a cyclic silicone oil can be stably compounded. However, since cleansing oil is liquid, it is inconvenient to use, and although it is sufficient as a makeup remover for point makeup, it is not satisfactory as a general-purpose makeup remover.

[0005]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a cleansing composition which has a quick release of stains on makeup stains, exhibits high cleaning performance, has high stability and is easy to use. It is in.

[0006]

Under these circumstances, the present inventors have conducted intensive studies and found that anionic surfactants, nonionic surfactants having an HLB of 9 or more, oils containing silicone oil in a specific ratio, alcohols, Combination of water and water at a specific blending ratio provides excellent penetration into skin details, quick release of dirt against makeup dirt, high cleaning performance, high stability, massageability, and wash-off The present inventors have found that a cleansing composition having good properties and feeling of use can be obtained, and completed the present invention.

That is, the present invention provides the following components (A) to
(E): (A) 0.05 to 5% by weight of an anionic surfactant, (B) 0.1 to 5% by weight of a nonionic surfactant having an HLB of 9 or more, and (C) 40 to 100% by weight of silicone oil. The present invention provides a cleansing composition containing 70 to 95% by weight of an oil agent, (D) 0.5 to 29% by weight of an alcohol, and (E) 0.1 to 29% by weight of water.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The anionic surfactant of component (A) used in the present invention is not particularly limited as long as it is used in a usual cleansing composition, and examples thereof include alkyl sulfates and alkyl ethers. Sulfate, fatty acid soap, ether carboxylic acid and its salt, alkane sulfonate, α-olefin sulfonate, sulfonate of higher fatty acid ester, dialkyl sulfosuccinate, monoalkyl sulfosuccinate, polyoxyethylene monoalkyl Sulfosuccinate, sulfonate of higher fatty acid amide, sulfate of glycerin fatty acid ester, sulfate of higher fatty acid alkylolamide, acylated amino acid salt, acylated methyltaurine salt,
Alkyl phosphate esters and the like. Among these, the alkyl phosphate ester represented by the general formula (1) is preferable because the effect of accelerating the floating of stains is higher.

[0009]

Embedded image

(Wherein, R ¹ represents a hydrocarbon group having 8 to 36 carbon atoms, X ¹ represents a hydrogen atom, an alkali metal, ammonium, a basic amino acid or an alkanolamine;
² represents a hydrogen atom, an alkali metal, ammonium, a basic amino acid, an alkanolamine or R ^1- (OCH ₂ CH ₂ ) _m- , and m represents a number from 0 to 5)

In the formula, examples of the hydrocarbon group having 8 to 36 carbon atoms represented by R ¹ include a linear or branched alkyl group or alkenyl group having 8 to 36 carbon atoms, and particularly, a C8 to C36 hydrocarbon group.
Preferred are straight-chain or branched-chain alkyl groups of up to 20. Specific examples include an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, an octadecyl group, and an icosyl group.

Among X ¹ and X ² , the alkali metal includes, for example, lithium, sodium, potassium and the like; the basic amino acid includes, for example, arginine, lysine, histidine, ornithine; Those having several to three hydroxyalkyl groups are preferable, and examples thereof include triethanolamine, diethanolamine, and monoethanolamine.

Further, m represents a number from 0 to 5, and particularly preferably 0.

Among such alkyl phosphate salts (1), those in which R ¹ is a branched alkyl group are particularly preferred.

The anionic surfactant of the component (A) may be used alone or in combination of two or more, and is contained in the entire composition in an amount of 0.05 to 5% by weight, preferably 0.1 to 4% by weight. ,
Particularly preferably, the content is 0.1 to 3% by weight. 0.05
If the amount is less than 5% by weight, the floating of the stain cannot be accelerated.

The nonionic surfactant of the component (B) is HL
It is B9 or more, preferably HLB 10 to 17, particularly preferably 12 to 17, and any of those used in ordinary cleansing compositions can be used.
When the HLB is less than 9, the washability during rinsing is poor. Note that HLB is an index indicating a hydrophilic-lipophilic balance, and in the present invention, a value calculated using the following equation by Oda and Teramura is used.

[0017]

(Equation 1)

Such nonionic surfactants include:
For example, polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyethylene glycol fatty acid ester, ethylene oxide derivative of propylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, ethylene oxide of mono- or polyglycerin fatty acid ester Derivatives, ethylene oxide derivatives of trimethylolpropane fatty acid ester, polyoxyethylene hydrogenated castor oil, polyoxyethylene hydrogenated castor oil fatty acid ester, polyoxyethylene hydrogenated castor oil pyroglutamate, polyoxyalkylene such as polyoxyethylene glycerin pyroglutamate Nonionic surfactants; sucrose fatty acid esters; alkyl glucosides; Serine fatty acid esters; polyglycerol alkyl ethers and the like. These preferably have a hydrophobic group such as an alkyl group, a phenyl group and a fatty acid residue having 8 to 36 carbon atoms.

More specifically, polyoxyethylene (3
0) hydrogenated castor oil, polyoxyethylene (40) hydrogenated castor oil, polyoxyethylene (50) hydrogenated castor oil, polyoxyethylene (60) hydrogenated castor oil, polyoxyethylene (15) decyltetradecyl ether, polyoxyethylene (20) decyl tetradecyl ether, polyoxyethylene (25) decyl tetradecyl ether,
Polyoxyethylene (10) hexyl decyl ether,
Polyoxyethylene (15) hexyl decyl ether,
Polyoxyethylene (20) hexyl decyl ether,
Polyoxyethylene (25) hexyl decyl ether,
Polyoxyethylene (10) octyl dodecyl ether, polyoxyethylene (16) octyl dodecyl ether, polyoxyethylene (20) octyl dodecyl ether, polyoxyethylene (25) octyl dodecyl ether, polyoxyethylene (15) glycerin monoisostea Polyoxyethylene (30) glyceryl monoisostearate, polyoxyethylene (3
0) glyceryl triisostearate, polyoxyethylene (40) glyceryl triisostearate, polyoxyethylene (30) trimethylolpropane trimiristate, polyoxyethylene (6) sorbitan monolaurate, polyoxyethylene (20) Sorbitan monolaurate, polyoxyethylene (20) sorbitan monostearate, polyoxyethylene (20) sorbitan monooleate, polyoxyethylene (30) sorbitol tetraoleate, polyoxyethylene (40)
Sorbitol tetraoleate and the like.

Of these, polyoxyethylene alkyl ether, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene hydrogenated castor oil are preferred, and those having a branched structure in the molecule are particularly preferred.

The nonionic surfactant of the component (B) can be used alone or in combination of two or more, and is contained in the total composition in an amount of 0.1 to 5% by weight, preferably 0.5 to 4% by weight. And particularly preferably 1 to 3% by weight. If it is less than 0.1% by weight, sufficient rinsing performance cannot be obtained, and if it exceeds 5% by weight, the storage stability at high temperatures deteriorates.

As the oil agent of the component (C), a liquid agent at room temperature is used. Among the oil agents, examples of the silicone oil include linear or cyclic dimethylpolysiloxane and methylphenylpolysiloxane. Of these,
A cyclic methylpolysiloxane of 10 cPa · s or less is preferred. Such a low-viscosity cyclic methylpolysiloxane is volatile, and does not remain on the skin even when used by wiping it off with a tissue paper or the like, giving a refreshing feel. The silicone oil can be used alone or in combination of two or more, and is blended in the oil agent in an amount of 40 to 100% by weight, preferably 40 to 90% by weight. If the amount is less than 40% by weight, the floating of dirt against makeup dirt and the cleaning power are not sufficient.

Further, as oils other than silicone oil,
It is not particularly limited as long as it is liquid at room temperature, and examples thereof include hydrocarbons, higher alcohols, higher fatty acids, higher alcohol higher fatty acid esters, animal and vegetable oils and fats, cholesterol fatty acid esters, and ethers. Among them, liquid paraffin, polyisobutene, isostearyl cholesteryl ester, neopentyl glycol dicaprate, triglyceride 2-ethylhexanoate, hexadecyl 2-ethylhexanoate, octadecyl myristate, olive oil, dialkyl ether represented by the general formula (2) Is preferred.

[0024]

Embedded image R ² -OR ³ (2)

(Wherein R ² and R ³ are the same or different and each represents a linear or branched alkyl group having 4 to 24 carbon atoms, and at least one of R ² and R ³ is branched at two or more positions. And the total carbon number of R ² and R ³ is 16 to 32).

The dialkyl ether (2) is preferable because it has excellent cleaning performance and is particularly less irritating to the eyes. In the general formula (2), R ² and R ³ each having 4 to 22 carbon atoms and having a total carbon number of 16 to 26 have higher detergency and are preferred. Further, a compound in which one of R ² and R ³ is a straight-chain alkyl group can be produced using a raw material generally used as a cosmetic raw material as a starting material, which is preferable in production. Further, as the alkyl group branched at two or more positions, those branched at the α-position are preferable because they have less oiliness.

Such a dialkyl ether (2) is
It is preferable to mix 2 to 60% by weight, especially 3 to 40% by weight in the oil agent because the detergency can be further increased.

The oil agent containing the silicone oil of the component (C) accounts for 70 to 95% by weight, preferably 75 to 9% by weight in the total composition.
0% by weight, particularly preferably 80 to 90% by weight. If the content is less than 70% by weight, sufficient cleaning performance cannot be obtained.
If it exceeds 5% by weight, the stability will be poor.

The alcohols of the component (D) include, for example, monoalcohols such as ethanol and isopropanol, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, hexanediol, butylene glycol, isoprene glycol, heptanediol, propylene glycol, and the like. Dipropylene glycol, tris (ethoxyethoxyethyl) phosphate, sorbitol, xylitol, maltitol,
Polyols such as polyoxyethylene methyl glucoside are exemplified. Of these, ethanol, glycerin, propylene glycol, 1,3-butylene glycol and sorbitol are particularly preferred.

The alcohol of component (D) may be one or two alcohols.
More than one species may be used in combination, with 0.1% being present in the total composition.
The content is 5 to 29% by weight, preferably 2 to 25% by weight, particularly preferably 4 to 15% by weight. If the amount is less than 0.5% by weight, the nonionic surfactant is difficult to dissolve at the time of production. If the amount exceeds 29% by weight, the feel of alcohols remains strong, and the feeling of use deteriorates.

The water of the component (E) accounts for 0.1 to 2 in the total composition.
9% by weight, preferably 1 to 20% by weight, particularly preferably 3 to 15% by weight. If it is less than 0.1% by weight, it is difficult to dissolve the anionic surfactant, and if it exceeds 29% by weight, it is difficult to secure the stability.

In the cleansing composition of the present invention, in addition to the above-mentioned essential components, components usually incorporated in cosmetics, pharmaceuticals, and the like, for example, a pharmaceutical agent, a moisturizing component, an anti-inflammatory agent, an amphoteric surfactant, a bactericide, Preservatives, ultraviolet absorbers, antioxidants, organic and inorganic powders, pigments, extracts, fragrances, and the like can be appropriately compounded as necessary. In addition, a solid oil component and a semi-solid oil component can be added as long as the effects of the present invention are not impaired.

The cleansing composition of the present invention can be produced according to a conventional method, for example, the components (A), (B),
It is manufactured by mixing and stirring (D) and (E) to make them uniform, and then adding the component (C) thereto.

The cleansing composition of the present invention can be obtained as a gel or a cream.
The viscosity at ℃ is 5,000-100,000 cPa · s,
In particular, it is preferably 10,000 to 60,000 cPa · s. Further, the cleansing composition of the present invention can be applied, for example, as a cleansing cream, a cleansing gel, a massage cream, a massage gel, and the like, and can be in any form for rinsing or wiping.

[0035]

EFFECT OF THE INVENTION The cleansing composition of the present invention is excellent in penetrating into the details of the skin, and has a high washing performance with a high degree of floating of stains on makeup stains, especially makeup stains such as lipstick and eye makeup which are difficult to remove. It has high stability and is easy to use because it is gel-like or cream-like, and has good massage properties, wash-out properties, and good usability.

[0036]

EXAMPLES Next, the present invention will be further described with reference to examples, but the present invention is not limited to these examples.

Example 1 Cleansing compositions having the compositions shown in Tables 1 and 2 were produced by a conventional method, and evaluated for appearance, viscosity immediately after production, stability, ease of use, stain floating, detergency and rinsing ability. did. The results are shown in Tables 1 and 2.

(Evaluation Method) (1) Appearance: Observed visually. (2) Viscosity immediately after production: Measured at 25 ° C. with a rotational viscometer (T-B, 10 rpm) equipped with a B8R type helical stand.

(3) Stability: The appearance after storage at room temperature for about one month was visually observed and evaluated according to the following criteria. ；: No change. X: separation.

(4) Ease of use: Ease of use when each of the cleansing compositions was used by 10 women was evaluated, and the number of persons evaluated as easy to use was evaluated according to the following criteria. ；: Six or more people evaluated that it was easy to use. Δ: 3 to 5 persons evaluated that it was easy to use. X: Two or less evaluated that it was easy to use.

(5) Stain lifting: A commercially available hard-to-remov lipstick is applied to the arm in a circle having a diameter of 2 cm (about 0.05 g), and 0.1 g of each cleansing composition is applied and massaged. Then, the number of times until the dirt emerged at that time was evaluated, and the evaluation was made based on the following criteria. ○: Floats within 5 times of massage. Δ: Floats within 6 to 20 massages. ×: Floats after 21 or more massages.

(6) Detergency: In the same manner as in the dirt floating test, the dirt was rinsed with running water after massaging 10 times (cleansing oil was wiped off with a tissue), and the lipstick was visually evaluated. ○: Almost no lipstick remains. Δ: About half remained. ×: Clearly remaining.

(7) Rinsing property: 1.0 g of the cleansing composition was applied to the arm, and after massaging, the feeling when washed off with running water was sensory evaluated according to the following criteria. ○; X: Oiliness remains.

[0044]

[Table 1]

[0045]

[Table 2]

Embodiment 2

(Table 3) (Components) (% by weight) (1) 2-Heptylundecyl arginine phosphate 0.1 (2) Polyoxyethylene octyl dodecyl ether (20EO) 2.4 (3) Glycerin 6.0 (4) ) Purified water 7.0 (5) Cyclic silicone (2.8 cPs; 7/3 mixture of silicone SH244 / silicone SH245, manufactured by Dow Corning Toray Silicone Co., Ltd.) 65.0 (6) Stearyl-1,3-dimethylbutyl ether 15.0 (7) Liquid paraffin 4.4 (8) Linden extract 0.1 (9) Fragrance trace

(Preparation method) The components (1) to (4) were mixed and dissolved (if necessary, heated), and the oil component was added dropwise with stirring to obtain a cleansing composition. The resulting cleansing composition was gel-like, easy to use, had a quick release of stains on makeup stains, had high detergency, and was excellent in massage properties, washability, and feeling of use.

Comparative Example 1

(Table 4) (Components) (% by weight) (1) Polyoxyethylene sorbitan monostearate (20EO) 1.0 (2) Sorbitan monostearate 2.5 (3) Polyoxyethylene octyl dodecyl ether (20EO) 5 5.0 (4) Methylphenylpolysiloxane (20 cPs; SF577, manufactured by Dow Corning Toray Silicone Co., Ltd.) 5.0 (5) Glyceryl tri-2-ethylhexanoate 10.0 (6) Liquid paraffin 55.0 (7 ) Polyoxyethylene methyl glucoside (10EO) 3.0 (8) Glycerin 5.0 (9) Purified water 13.5

(Preparation method) A cleansing gel was obtained by subjecting all components to heating, dissolving, mixing and cooling operations. The obtained cleansing gel was slow in lifting the dirt and low in cleaning properties, with respect to makeup dirt that was difficult to remove.

Embodiment 3

(Ingredient) (% by weight) (1) Sodium N-stearoyl-L-glutamate 0.1 (2) Polyethylene glycol isostearate (20EO) 3.0 (3) Sorbitol 11.0 (4) Tris ( (Ethoxyethoxyethyl) phosphate 1.0 (5) Asnaro extract 0.5 (6) Acrylic acid / alkyl methacrylate copolymer (PEMULEN TR-1, manufactured by BF Goodrich) 0.4 (7) Succinic acid 0 0.01 (8) Methyl paraben 0.3 (9) Purified water 13.59 (10) Methyl polysiloxane (Silicone KF96A (1cs), manufactured by Shin-Etsu Silicone Co., Ltd.) 15.0 (11) Perfluoropolyether (FOMBLIN HC / 04) 0.5 (12) Cyclic silicone (2.8 cPs; 7/3 mixture of silicone SH244 / silicone SH245, Dow Corning Toray Silicone) 5.0 (13) isononyl isononanoate 9.5 (14) tri-2-ethylhexanoate glyceryl 10.0 (15) dibutylhydroxytoluene 0.1

(Preparation method) The components (1) to (9) were mixed and dissolved (heated if necessary), and the oil component was added dropwise with stirring to obtain a cleansing composition. The resulting cleansing composition was gel-like, easy to use, had a quick release of stains on makeup stains, had high detergency, and was excellent in massage properties, washability, and feeling of use.

Embodiment 4

[Table 6] (Components) (% by weight) (1) Arginine 2-heptylundecyl phosphate 0.5 (2) Sodium N-lauroyl-β-alanine 0.5 (3) Polyoxyethylene octyl dodecyl ether (20EO) 3.0) (4) Glycerin 4.0 (5) Xylitol 4.0 (6) 1,3-butylene glycol 0.8 (7) Hibamata extract 0.5 (8) Carboxyvinyl polymer (Carbopol 981, BF 0.4 (9) Potassium hydroxide 0.1 (10) Blue No. 1 0.01 (11) Methyl paraben 0.2 (12) Ethyl paraben 0.2 (13) Purified water 5.79 ( 14) Methyl polysiloxane (Silicone KF96A (1cs), Shin-Etsu Silicone Co., Ltd.) 13.0 (15) Cyclic silicone (2.8 cPs; 7/3 mixture of silicone SH244 / silicone SH245, Dow Corning Toray) 45.0 (16) Squalane 20.0 (17) Cetyl alcohol 2.0

(Preparation method) The components (1) to (13) were mixed and dissolved (if necessary, heated), and the oil component was added dropwise with stirring to obtain a cleansing composition. The resulting cleansing composition was gel-like, easy to use, had a quick release of stains on makeup stains, had high detergency, and was excellent in massage properties, washability, and feeling of use.

Embodiment 5

(Table 7) (Components) (% by weight) (1) Arginine 2-heptylundecyl phosphate 0.2 (2) Lauryl dimethylamine oxide 0.2 (3) Polyoxyethylene octyl dodecyl ether (20EO) 1.2 (4) Polyoxyethylene hydrogenated castor oil (40EO) 1.2 (5) Glycerin 2.0 (6) Diglycerin 1.0 (7) Polyoxyethylene methyl glucoside 0.5 (8) Oat extract 0.2 (9) ) Disodium edetate 0.05 (10) Lactic acid 0.05 (11) Purified water 3.4 (12) Cyclic silicone (2.8 cPs; 7/3 mixture of silicone SH244 / silicone SH245, Dow Corning Toray Silicone) 45.0 (13) Polyisobutene 20.0 (14) Isotridecyl isononanoate 24.8 (15) Olive oil 0.2

The components (1) to (11) were mixed and dissolved (if necessary, heated), and the oil component was added dropwise with stirring to obtain a cleansing composition. The resulting cleansing composition is gel-like and easy to use, has a quick release of stains on makeup stains, has high detergency, massage properties, washability,
It was excellent in usability.

Embodiment 6

(Table 8) (Components) (% by weight) (1) Arginine 2-hexyldecyl phosphate 0.4 (2) Sodium polyoxyethylene lauryl ether sulfate (3EO) 1.0 (3) Polyoxyethylene octyl dodecyl ether ( (20EO) 2.0 (4) Alkyl glucoside (AG-10LK, manufactured by Kao Corporation) 1.6 (5) Dipropylene glycol 3.0 (6) Maltitol 4.0 (7) Ethanol 2.0 (8) Methyl paraben 0.1 (9) Purified water 10.5 (10) Cyclic silicone (2.8 cPs; 7/3 mixture of silicone SH244 / silicone SH245, manufactured by Dow Corning Silicone Toray) 70.0 (11) Isopropyl stearate 2.0 (12) isostearyl isostearate 3.0 (13) nicotinic acid-dl-α-tocopherol 0.2 (14) l-menthol 0.1 (15) butyric Paraben 0.1

(Preparation method) The components (1) to (9) were mixed and dissolved (if necessary, heated), and the oil component was added dropwise with stirring to obtain a cleansing composition. The resulting cleansing composition was gel-like, easy to use, had a quick release of stains on makeup stains, had high detergency, and was excellent in massage properties, washability, and feeling of use.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ichiro Sugai 2-1-3 Bunka, Sumida-ku, Tokyo Inside Kao Research Institute

Claims (3)

[Claims] 1. The following components (A) to (E): (A) 0.05 to 5% by weight of an anionic surfactant, (B) 0.1 to 5% by weight of a nonionic surfactant having an HLB of 9 or more, C) A cleansing composition containing 70 to 95% by weight of an oil agent containing 40 to 100% by weight of silicone oil, (D) 0.5 to 29% by weight of alcohol, and (E) 0.1 to 29% by weight of water. . 2. The cleansing composition according to claim 1, wherein the nonionic surfactant of the component (B) has a branched structure. 3. The oil agent of the component (C) is represented by the general formula (2): R ² —OR ³ (2) (wherein R ² and R ³ are the same or different and have 4 to 4 carbon atoms)
24 linear or branched alkyl groups; R ² and R
³ is an alkyl group branched at two or more positions, and the total carbon number of R ² and R ³ is 16 to 3
The cleansing composition according to claim 1 or 2, which comprises a dialkyl ether represented by formula (2).