JPH08319478A - Refrigerant mixture composition - Google Patents

Abstract

PURPOSE: To obtain a refrigerant mixture composition which can be used for a refrigerator designed to use a specified chlorofluorocarbon such as R12 and causes no trouble even in the presence of a lubricating oil for R12 by adding polyhydric alcohol(s) such as propylene glycol to a chlorofluorocarbon substitute used as the refrigerant. CONSTITUTION: This refrigerant composition is produced by mixing a chlorofluorocarbon substitute comprising 1,1,1,2-tetrafluoroethane and 1,2- difluoroethane, used as the refrigerant, with one or more of (di-, tri- and tetra-) ethylene glycols, (di- and tri-)propylene glycols, hexylene glycol, and ethylene glycol dimethyl ether. This composition does not cause troubles such as gas leakage and seizure when used for a refrigerator designed to use a specified chlorofluorocarbon conventionally used, such as R12, even in the presence of a lubricating oil for R12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixed refrigerant composition used in a refrigerating engine for a specified CFC such as R-12 (dichlorodifluoromethane).

[0002]

2. Description of the Related Art Conventionally, as a refrigerant used in a cooling device such as a car cooler or a refrigerating engine such as a refrigerator, a specific fluorocarbon (a fluorocarbon compound) such as R-12 (dichlorodifluoromethane, CCl ₂ F ₂ ) is used. Are known. However, in recent years, a chlorofluorocarbon compound released into the atmosphere reaches the ozone layer while maintaining its molecular structure, and when the compound is decomposed by ultraviolet rays or the like, chlorine radicals are generated,
It was revealed that the radical destroys the ozone layer. Therefore, the production and use of specific CFCs is prohibited.

Therefore, various alternatives to the specified CFCs have been studied, and R-of the specified CFCs for refrigerant has been studied.
As alternatives to No. 12, alternative CFCs such as R-134a and R-152a have been developed. R-134a is 1,1,
It is 1,2-tetrafluoroethane and is represented by the chemical formula CF ₃ CH ₂ F. Also, R-152a is 1,1-
It is difluoroethane and is represented by the chemical formula CF ₂ CH ₃ . Since R-134a and R-152a do not contain chlorine in the molecule, as is clear from the above chemical formula,
It is considered that there is no risk of destroying the ozone layer even when it reaches the ozone layer and is decomposed.

However, if the alternative CFCs such as R-134a and R-152a are directly applied to the conventional R-12 refrigerating engine, these alternative CFCs are converted into R.
Since the operating pressure at room temperature is higher than that of -12, there is a disadvantage that gas leakage occurs from the valve connecting portion, O-ring, etc. Further, the CFC substitute is incompatible with commonly used refrigerating machine oil. Since it is low, there is an inconvenience such as seizure of the compression pump.

Therefore, a polyglycol having at least two hydroxyl groups in one molecule described in US Pat. No. 4,755,316 is known as a refrigerating machine oil for R-134a. Lubricants containing a polyoxyalkylene glycol derivative as a main component, which are described in JP-A-2-242888 and JP-A-3-121195, are known as those having further improved compatibility. The polyoxyalkylene glycol derivative described in JP-A-2-242888 has R ¹
A general formula (OR ² ) _n OH (wherein R ¹ is a carbon number 1
To an alkyl group, R ² is an alkylene group having 2 to 4 carbon atoms, and n is a number of 6 to 80),
The polyoxyalkylene glycol derivative described in JP-A-3-121195 is R ¹ O (CH ₂ CH (C
H ₃ ) O) _n R ² ) _n OH (wherein R ¹ ,
R ² is an alkyl group having 1 to 4 carbon atoms and may be the same or different) and has an average molecular weight of 500 to 18
00 polyoxyalkylene glycol dialkyl ether.

The polyoxyalkylene glycol derivative described in each of the above publications is used in a new refrigerating engine as R-134a.
When filled with R-134a, it has excellent compatibility with R-134a. However, when the R-12 lubricating oil remains in the refrigeration engine, for example, when the R-12 is extracted from a used automobile air conditioner and is newly filled with R-134a, the R-12 lubricating oil is used. There is a disadvantage that compatibility with oil cannot be obtained.

[0007]

Therefore, the present invention is based on R
An object of the present invention is to provide a refrigerant composition containing CFC substitute that can be used without any trouble even if a lubricating oil for -12 is interposed.

[0008]

In order to achieve such an object, the mixed refrigerant composition of the present invention comprises 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane or a mixture thereof. CFC alternative refrigerant and ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, ethylene glycol dimethyl ether, or a mixture of two or more thereof. It is characterized by

[0009]

The mixed refrigerant composition of the present invention comprises ethylene glycol, diethylene glycol, triethylene glycol,
Since it contains any one of tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, ethylene glycol dimethyl ether, or a mixture of two or more thereof, R-134a which is an alternative CFC for a refrigerant per se.
(1,1,1,2-tetrafluoroethane), R-15
2a (1,1-difluoroethane) or a mixture thereof, and after extracting R-12 from the conventional R-12 refrigeration engine, lubrication for R-12 in the refrigeration engine When the refrigerating engine is filled with oil remaining, it shows compatibility with the lubricating oil for R-12. The mixed refrigerant composition of the present invention also comprises the R-1
It exhibits a refrigerant action close to 2, and does not cause gas leakage or seizure of the compression pump.

[0010]

EXAMPLE 1 Next, the mixed refrigerant composition of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing a configuration example of a refrigerating engine that uses the mixed refrigerant composition of the present invention as a refrigerant.

In this Example, 170 g of an additive was added to 1600 g of propylene glycol, 50 g of tripropylene glycol, and 50 g of hexylene glycol, and the mixture was stirred to form a uniform mixture, and then 100 g of the mixture was mixed with R-1.
600 g of 34a was added and stirred to obtain a uniform mixed refrigerant composition. Each of the above stirring was performed at room temperature. Further, the obtained mixed refrigerant composition was an orange and transparent liquid.

The additive may be any additive as long as it is generally used in a refrigerant composition. In this embodiment, the additive is dioctyl sebacate as a pour point stabilizer. 50 g of a mixture with bis (2-ethylhexyl) azelate, 50 g of phthalic acid ester as a viscosity stabilizer, 50 g of benzotriazole as a copper metal deactivator, extreme pressure agent, load bearing agent, antiwear agent, rust inhibitor 10 g of phosphoric acid ester, a metal corrosion inhibitor, a lubricant, a corrosion inhibitor, and 10 g of dicyclohexylamine as a gas phase rust inhibitor.

Examples of the viscosity stabilizer include phthalic acid esters such as di-2-ethylhexyl phthalate, tricresyl phosphate, di (N-butyl) cresyl phosphate, and polysulfate. Mention may be made of olefin polymers or copolymers such as methacrylate, polyisobutylene, styrene copolymers such as polyalkylstyrene, diisodecyl adipate. Further, as the copper corrosion inhibitor, in addition to benzotriazole, 2
-Methylbenzimidazole, 2,6-t-butyl-p
-Cresol, 2,6-t-butyl-4-ethylphenol, 2 (N-dodecyl-dithio) benzimidazole, N, N'-disalicylidene-1,2-aminopropane, imidazole, benzimidazole, pyrazole,
Mention may be made of 3,5-dimethylpyrazole, methylenebisbenzotriazole and zinc dithiophosphate. Further, as the extreme pressure agent, load-bearing agent, antiwear agent, and rust preventive agent, tris (isopropylphenyl) phosphate, phenylphosphonic acid, phenylphosphonic acid dimethyl ester, triethylphosphite, diethylphosphite, trimethylphosphite, Tributyl phosphate, tris (2
-Chloroethyl) phosphate, cresyl diphenyl phosphate and other phosphate esters, zinc dithiophosphate, sulfide terpenes, sulfurized olefins, sulfurized fats, polymer amines, penitaerythritol monooleate,
Examples thereof include sorbitan monooleate, succinic acid and derivatives thereof, oleic beef tallow amide, and calcium sulfonate. Also, the metal corrosion inhibitor,
Lubricants, corrosion inhibitors, gas phase rust inhibitors other than dicyclohexylamine, diethanolamine, triethanolamine, rosin amine, β-aphtyl amine, hexadecyl amine, dicapric acid, propylene glycol, dicyclohexylammonium nitrite, toluidine,
Mention may be made of nut quinoline, thiourea, sodium oleate, sodium benzoate, N-olein sarcosine, sorbitan monooleate, pentaerythritol monooleate.

Next, the R-12 was taken out from the refrigerating engine of the automobile air conditioner that had been charged with the R-12, and the mixed refrigerant composition of the present example was charged instead, and the refrigerating engine was operated. It was

As shown in FIG. 1, in the refrigerating engine, a compression pump 1, a condenser 2, a throttle valve 3 and an evaporator 4 are connected by a conduit 5 to form a cooling cycle. 4 are equipped with fans 6 and 7, respectively. A refrigerant supply port 8 is provided in the conduit 5 between the compression pump 1 and the condenser 2, and a filter 9 is provided in the conduit 5 between the condenser 2 and the throttle valve 3.

In the refrigerating engine shown in FIG. 1, the supplied refrigerant becomes refrigerant vapor A at the outlet of the evaporator 4, and is adiabatically compressed by mechanical work in the compression pump 1 to become high temperature and high pressure vapor B. The condenser 2 radiates heat to the gas supplied from the fan 37 at a high level of temperature and condenses at a constant pressure to form a liquid C.
become. At this time, the gas supplied from the fan 6 becomes hotter and is discharged outside the vehicle compartment.

Next, the liquid C is isenthalpically expanded by being blown out from the throttle valve 3 to become a low temperature wet vapor D, and the evaporator 4 absorbs the heat of the gas supplied from the fan 7 at a low level temperature. Cooling the gas by
Return to low temperature and low pressure steam A. At this time, the gas cooled by the evaporator 4 is discharged into the vehicle compartment from the outlet 10 to cool the vehicle.

Since such a refrigerating engine is originally designed to use R-12 which is a specific CFC as a refrigerant, even if R-12 is removed, the lubricating oil of the compression pump 1 remains in the conduit 5. ing. A naphthene-based mineral oil is used as the lubricating oil for R-12, and although it is compatible with R-12, R-134a, R which are alternative CFCs.
It is not compatible with -152a or its lubricating oil. For this reason,
Normally, after the R-12 is pulled out, if the respective parts of the refrigeration engine are not precisely cleaned, the compression pump 1 may be seized during operation.

However, according to the mixed refrigerant composition of the present embodiment, it is compatible with not only R-134a but also the above-mentioned lubricating oil for R-12. Therefore, R-12 is extracted and then immediately filled. Also, it is possible to operate the compression pump 1 without causing seizure.

When the refrigerating engine shown in FIG. 1 was operated for 30 minutes with the mixed refrigerant composition of this example, the average pressure on the high pressure side of the compressor 1 was 11.0 kg / cm ² , and the average pressure on the low pressure side was 1. It was 0.7 kg / cm ² . The average temperature of the mixed refrigerant composition measured at the outlets of the compressor 1, the condenser 2, and the throttle valve 3 during operation of the refrigerating engine is 41.9 ° C., respectively.
The average temperature of the air sucked from the fan 7 was 20.4 ° C., and the average temperature of the air discharged from the outlet 10 was 3.7 ° C.

When the refrigerating engine shown in FIG. 1 was operated for 30 minutes by R-12, the average pressure on the high pressure side of the compressor 1 was 11.3 kg / cm ² , and the average pressure on the low pressure side was 1.7 k.
It was g / cm ² . Further, during operation of the refrigerating engine, the average temperatures of the mixed refrigerant composition measured at the outlets of the compressor 1, the condenser 2, and the throttle valve 3 are 50.7 ° C. and 44.5, respectively.
The average temperature of the air sucked from the fan 7 was 26.3 ° C., and the average temperature of the air discharged from the outlet 10 was 4.1 ° C.

From the pressure and temperature, it is clear that the refrigerating engine is operating normally with the mixed refrigerant composition of this example as in the case of using R-12.

[0023]

Example 2 In this example, 95 g of an additive was added to 1000 g of ethylene glycol dimethyl ether and stirred to form a uniform mixture, and 100 g of the mixture was added with R-.
600 g of 134a was added and stirred to obtain a uniform mixed refrigerant composition. Each of the above stirring was performed at room temperature. Further, the obtained mixed refrigerant composition was an orange and transparent liquid. In this example, the additive is a mixture of dioctyl sebacate and bis (2-ethylhexyl) azelate 25.
g, phthalic acid ester 25 g, benzotriazole 25
g, phosphoric acid ester 10 g, dicyclohexylamine 1
It consists of 0 g.

Then, as in Example 1, R-12 was extracted from the refrigerating engine shown in FIG. 1, and the mixed refrigerant composition of this example was charged in its place, and the refrigerating engine was operated.

When the refrigerating engine shown in FIG. 1 was operated for 30 minutes with the mixed refrigerant composition of this example, the average pressure on the high pressure side of the compressor 1 was 10.8 kg / cm ² , and the average pressure on the low pressure side was 1. It was 0.2 kg / cm ² . The average temperature of the mixed refrigerant composition measured at the outlets of the compressor 1, the condenser 2 and the throttle valve 3 during operation of the refrigerating engine is 49.5 ° C., respectively.
The average temperature of the air sucked from the fan 7 was 17.1 ° C, and the average temperature of the air discharged from the outlet 10 was 2.4 ° C. From the pressure and temperature, it is clear that the refrigerating engine is operating normally with the mixed refrigerant composition of this example as in the case of using R-12.

[0026]

Example 3 In this example, first, 1000 g of ethylene glycol dimethyl ether and 5 parts of dipropylene glycol were used.
Additive 170 to 0 g, 50 g of tetraethylene glycol
g was added and stirred to make a uniform mixture, and then 600 g of R-134a was added to 100 g of the mixture and stirred to obtain a uniform mixed refrigerant composition. Each of the above stirring was performed at room temperature.
Further, the obtained mixed refrigerant composition was an orange and transparent liquid. In this example, the additive is dioctyl sebacate and bis (2-ethylhexyl) azelate.
And 50 g of a phthalic acid ester, 50 g of benzotriazole, 10 g of triethylphosphite as a phosphoric acid ester, and 10 g of dicyclohexylamine.

Next, as in Example 1, R-12 was extracted from the refrigeration engine shown in FIG. 1, and the mixed refrigerant composition of this example was charged instead, and the refrigeration engine was operated.

When the refrigerating engine shown in FIG. 1 was operated for 30 minutes with the mixed refrigerant composition of this example, the average pressure on the high pressure side of the compressor 1 was 10.7 kg / cm ² , and the average pressure on the low pressure side was 1. It was 0.7 kg / cm ² . Further, during operation of the refrigerating engine, the average temperature of the mixed refrigerant composition measured at the outlets of the compressor 1, the condenser 2 and the throttle valve 3 is 41.1 ° C., respectively.
The average temperature of the air sucked from the fan 7 was 20.5 ° C, and the average temperature of the air discharged from the outlet 10 was 3.7 ° C. From the pressure and temperature, it is clear that the refrigerating engine is operating normally with the mixed refrigerant composition of this example as in the case of using R-12.

In the refrigerating engine, when the combination of the used refrigerant and lubricating oil is inappropriate, the refrigerant composition is withdrawn after the operation is completed, and the refrigerant composition changes from orange immediately after stirring to dark brown, and is extremely dark. It is sometimes observed that it is black and opaque. It is considered that this is because the combination of the refrigerant and the lubricating oil is improper, which causes a load on the compressor 1 and causes corrosion and the like in each part of the refrigeration engine.

However, when the mixed refrigerant composition was extracted and examined after the end of the operation of the refrigerating engine in Examples 1 to 3, it was still orange immediately after stirring and no turbidity was observed. Therefore, according to the mixed refrigerant composition of the present embodiment, the combination of the refrigerant and the lubricating oil is suitable, and even if it is used for a long period of time, the compressor 1 will be loaded, and the refrigeration engine parts will not be corroded. It is considered that there is no risk of this occurring.

[0031]

Example 4 In this example, first, 1000 g of propylene glycol, 50 g of dipropylene glycol, and 50 g of diethylene glycol were added with 170 g of an additive and stirred to form a uniform mixture, and then 100 g of the mixture was mixed with R-13.
600 g of 4a was added and stirred to obtain a uniform mixed refrigerant composition. Each of the above stirring was performed at room temperature. Further, the obtained mixed refrigerant composition was an orange and transparent liquid. In this example, the additive is 50 g of a mixture of dioctyl sebacate and bis (2-ethylhexyl azelate),
Phthalates 50 g, benzotriazole 50 g,
10 g of triethyl phosphite as a phosphoric acid ester,
It consists of 10 g of dicyclohexylamine.

Next, as in Example 1, R-12 was taken out from the refrigerating engine shown in FIG. 1, and the mixed refrigerant composition of this example was charged in its place, and the refrigerating engine was operated.

When the refrigerating engine shown in FIG. 1 was operated for 30 minutes with the mixed refrigerant composition of this example, the average pressure on the high pressure side of the compressor 1 was 11.0 kg / cm ² , and the average pressure on the low pressure side was 1. It was 0.8 kg / cm ² . Further, during operation of the refrigerating engine, the average temperature of the mixed refrigerant composition measured at the outlets of the compressor 1, the condenser 2 and the throttle valve 3 is 42.0 ° C., respectively.
The temperature was 40.7 ° C. and 0.8 ° C., the average temperature of the air sucked from the fan 7 was 21.0 ° C., and the average temperature of the air discharged from the outlet 10 was 3.8 ° C. From the pressure and temperature, it is clear that the refrigerating engine is operating normally with the mixed refrigerant composition of this example as in the case of using R-12.

[0034]

Example 5 In this example, first, 1000 g of propylene glycol and 25 g of hexylene glycol were added to 20 g of the additive 20.
0 g was added and stirred to make a uniform mixture, and then 650 g of R-152a was added to 100 g of the mixture and stirred to obtain a uniform mixed refrigerant composition. Each of the above stirring was performed at room temperature. Further, the obtained mixed refrigerant composition was an orange and transparent liquid. In this example, the additive is 50 g of a mixture of dioctyl sebacate and bis (2-ethylhexyl azelate), 50 g of a phthalate ester, a metal corrosion inhibitor, a lubricant, a pickling inhibitor, a corrosion inhibitor, and a gas. 25 g of diethanolamine as a rust preventive agent, 50 g of benzotriazole, 15 methacrylic acid as a pour point depressant
g, and 10 g of methyl phosphate as a phosphoric acid ester.

Next, as in Example 1, R-12 was extracted from the refrigerating engine shown in FIG. 1, and the mixed refrigerant composition of this example was charged instead, and the refrigerating engine was operated.

When the refrigerating engine shown in FIG. 1 was operated for 30 minutes with the mixed refrigerant composition of this example, the average pressure on the high pressure side of the compressor 1 was 9.4 kg / cm ² , and the average pressure on the low pressure side was 1. It was 0.5 kg / cm ² . Further, during the operation of the refrigerating engine, the average temperatures of the mixed refrigerant composition measured at the outlets of the compressor 1, the condenser 2 and the throttle valve 3 are 48.0 ° C. and 4 respectively.
The average temperature of the air sucked from the fan 7 was 25.7 ° C., and the average temperature of the air discharged from the outlet 10 was 5.0 ° C. From the pressure and temperature, it is clear that the refrigerating engine is operating normally with the mixed refrigerant composition of this example, and the mixed refrigerant composition of this example is compatible with R-152a. .

[0037]

Example 6 In this example, an orange transparent liquid mixed refrigerant composition was obtained in exactly the same manner as in Example 4 except that propylene glycol in Example 4 was changed to ethylene glycol dimethyl ether.

Next, as in Example 1, R-12 was extracted from the refrigerating engine shown in FIG. 1, and the mixed refrigerant composition of this example was charged in its place, and the refrigerating engine was operated.

When the refrigerating engine shown in FIG. 1 was operated for 30 minutes with the mixed refrigerant composition of this example, the average pressure on the high pressure side of the compressor 1 was 9.4 kg / cm ² , and the average pressure on the low pressure side was 1. It was 0.4 kg / cm ² . Further, during the operation of the refrigerating engine, the average temperatures of the mixed refrigerant composition measured at the outlets of the compressor 1, the condenser 2 and the throttle valve 3 are 56.1 ° C. and 4 respectively.
The average temperature of the air sucked from the fan 7 was 23.8 ° C, and the average temperature of the air discharged from the outlet 10 was 4.7 ° C. From the pressure and temperature, it is clear that the refrigerating engine is operating normally with the mixed refrigerant composition of this example, and the mixed refrigerant composition of this example is compatible with R-152a. .

[0040]

Example 7 In this example, first, 500 g of propylene glycol, 50 g of tripropylene glycol, 50 g of tetraethylene glycol and 25 g of hexylene glycol.
Add 100 g of additive to and stir to make a uniform mixture,
Then, to 100 g of the mixture, 200 g of R-134a and R
450 g of -152a was added and stirred to obtain a uniform mixed refrigerant composition. Each of the above stirring was performed at room temperature. Further, the obtained mixed refrigerant composition was an orange and transparent liquid.
In this example, the additive is a mixture of dioctyl sebacate and bis (2-ethylhexyl azelate) 2.
5 g, phthalic acid ester 25 g, diethanolamine 2
It consists of 5 g and 25 g of benzotriazole.

Next, as in Example 1, R-12 was extracted from the refrigerating engine shown in FIG. 1, and the mixed refrigerant composition of this example was charged in its place, and the refrigerating engine was operated.

When the refrigerating engine shown in FIG. 1 was operated for 30 minutes with the mixed refrigerant composition of this example, the average pressure on the high pressure side of the compressor 1 was 11.5 kg / cm ² , and the average pressure on the low pressure side was 1. It was 0.6 kg / cm ² . The average temperature of the mixed refrigerant composition measured at the outlets of the compressor 1, the condenser 2 and the throttle valve 3 during operation of the refrigerating engine is 46.4 ° C., respectively.
The average temperature of the air sucked from the fan 7 was 23.3 ° C, and the average temperature of the air discharged from the outlet 10 was 5.1 ° C. From the pressure and temperature, the refrigeration engine was operating normally with the mixed refrigerant composition of this example, and the mixed refrigerant composition of this example was compatible with the mixture of R-134a and R-152a. It is clear to have.

[0043]

Example 8 In this example, an orange transparent liquid mixed refrigerant composition was obtained in exactly the same manner as in Example 6 except that propylene glycol in Example 6 was changed to ethylene glycol dimethyl ether.

Next, as in Example 1, R-12 was extracted from the refrigerating engine shown in FIG. 1 and, instead, the mixed refrigerant composition of this example was charged, and the refrigerating engine was operated.

When the refrigerating engine shown in FIG. 1 was operated for 30 minutes with the mixed refrigerant composition of this example, the average pressure on the high pressure side of the compressor 1 was 11.8 kg / cm ² , and the average pressure on the low pressure side was 1. It was 0.7 kg / cm ² . The average temperature of the mixed refrigerant composition measured at the outlets of the compressor 1, the condenser 2 and the throttle valve 3 during operation of the refrigerating engine is 47.9 ° C., respectively.
The average temperature of the air sucked from the fan 7 was 20.8 ° C., and the average temperature of the air discharged from the outlet 10 was 4.2 ° C. From the pressure and temperature, the refrigeration engine was operating normally with the mixed refrigerant composition of this example, and the mixed refrigerant composition of this example was compatible with the mixture of R-134a and R-152a. It is clear to have.

In the mixed refrigerant composition of the present invention, ethylene glycol or triethylene glycol may be used alone or in combination in addition to the polyhydric alcohol used in each of the above-mentioned examples. You may use it, mixing with the polyhydric alcohol used for.

[0047]

From the above, it is clear that the mixed refrigerant composition of the present invention can be used without any trouble even in the presence of the lubricating oil for R-12.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration example of a refrigeration engine.

[Explanation of symbols]

1 ... Compressor, 2 ... Condenser, 3 ... Throttle valve, 4 ... Evaporator.

Claims (1)

[Claims] 1. A 1,1,1,2-tetrafluoroethane,
Alternative CFCs for refrigerants consisting of either 1,1-difluoroethane or mixtures thereof, and ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, ethylene glycol dimethyl ether Or a mixture of two or more thereof.