JPH09100483A - Refrigerator oil and working fluid for refrigerator using the oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a refrigerator oil compatible with a hydrofluorocarbon refrigerant, resistant to migration, causing little abrasion and seizure and useful for a compression refrigerator by using a base oil produced by mixing a specific low-viscosity base oil with a high-viscosity base oil at a specific ratio. SOLUTION: This refrigerator oil contains a base oil produced by mixing (A) 95-55wt.% of a low-viscosity base oil composed of a polyoxyalkylene derivative (Z) of the formula, R1 -O-(AO)n -R2 (R1 is a 1-4C alkyl; R2 is H or R1 ; (AO)n is an oxypropylene or oxyethylene polymer group having an average polymerization degree of (n)) and having a kinetic viscosity (ηv ) of 5-30cSt at 100 deg.C with (B) 5-45wt.% of a high-viscosity base oil composed of the compound Z and having an ηv not less than 1.5 times that of the component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating machine oil used in a compression refrigerating machine such as a car air conditioner, a refrigerator and an air conditioner, and a working fluid for a refrigerating machine, and more particularly to a hydrofluorocarbon refrigerant. It is suitable for use in refrigerators for car air conditioners.

[0002]

2. Description of the Related Art Chlorofluorocarbons have been widely used as a refrigerant in a compression refrigerator. In recent years, the use of these refrigerants has been restricted due to environmental problems, and as an alternative refrigerant, a hydrofluorocarbon refrigerant that is a fluorinated hydrocarbon containing no chlorine (hereinafter referred to as HFC
Also called a refrigerant. ) Is being adopted.

However, conventionally used mineral oil type refrigerating machine oils are not compatible with hydrofluorocarbon refrigerants. Therefore, as refrigerating machine oil, synthetic oil, particularly polyoxyalkylene glycol-based compound (hereinafter, also referred to as PAG).
And polyhydric alcohol ester compounds are used.

[0004]

However, when a hydrofluorocarbon refrigerant is used, the amount of refrigerating machine oil in the compressor decreases due to the phenomenon called migration described below, so that lubrication is insufficient and wear, seizure, etc. There is a problem that it occurs.

The migration is because the compressor itself has a relatively high temperature when the operation of the compression refrigerator is stopped,
This is a phenomenon in which refrigerating machine oil evaporates together with the refrigerant and liquefies in a condenser or evaporator that has a relatively low temperature. For this reason, the refrigerating machine oil in the compressor becomes low. If the operation of the compression refrigerator is started again in this state, lubrication in the compressor is not sufficient, and wear and seizure may occur.

In the conventionally used chlorofluorocarbon refrigerant, since the refrigerant itself has lubricity, even if the refrigerating machine oil is reduced, a lubrication problem is unlikely to occur.

In order to prevent migration from occurring, it may be possible to reduce vaporization of the refrigerating machine oil by using PAG or ester compound having a relatively large molecular weight. However, since the viscosity of the refrigerating machine oil is high, the loss in operation is large, and since such a PAG has poor compatibility with the hydrofluorocarbon refrigerant, this measure is not appropriate.

[0008] In particular, migration tends to be a problem in the case of a compression type refrigerator mounted on an automobile such as a car air conditioner. In a car air conditioner, the power source depends on an internal combustion engine such as a gasoline engine, and the compressor must be placed in the engine room. Therefore, the engine room is kept at a relatively high temperature even after the engine is stopped, the temperature difference between the condenser and the evaporator is large, and migration is likely to occur.

An object of the present invention is to provide a refrigerating machine oil that is compatible with a hydrofluorocarbon refrigerant, is less likely to cause a migration phenomenon, and is less likely to cause abrasion and seizure.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have used a polyoxyalkylene glycol compound having a specific structure as a refrigerating machine oil, and the viscosity of the refrigerating machine oil is The viscosity should be within a range where energy loss during operation is small, a sufficient sealing effect is obtained, and compatibility with a hydrofluorocarbon refrigerant is sufficiently obtained. And, as a part thereof, a high-viscosity base oil, that is, by containing a certain amount or more of a high molecular weight polyoxyalkylene glycol-based compound, it is possible to leave a refrigerating machine oil portion that is difficult to vaporize in the compressor, which causes problems in lubricity I came to the idea that it would not occur.

The refrigerating machine oil used in the compression refrigerating machine according to the first aspect of the present invention has a kinematic viscosity at 100 ° C. of 5 cSt.
A low-viscosity base oil 9 comprising the polyoxyalkylene glycol derivative represented by the above chemical formula 1 and having a viscosity of 30 cSt or more
5 to 55% by weight was mixed with 5 to 45% by weight of a high-viscosity base oil composed of a polyoxyalkylene glycol derivative represented by the following chemical formula 1 and having a viscosity 1.5 times or more that of the low-viscosity base oil. It uses a base oil.

Embedded image R ₁ —O— (AO) _n —R ₂ wherein R ₁ is an alkyl group having 1 to 4 carbon atoms, R ₂ is an alkyl group having 1 to 4 carbon atoms or hydrogen, and (AO) _n is It is a polymer group of an oxypropylene group and / or an oxyethylene group, and n is a number representing the average degree of polymerization.

In these embodiments, in order to prevent the migration phenomenon from occurring easily, the high-viscosity base oil is contained in an amount of 5% by weight or more,
It is preferable to mix 20% by weight or more.
Further, in order to maintain the required compatibility with the hydrofluorocarbon refrigerant, the mixing amount of the high-viscosity base oil is 55% by weight or less,
It is necessary that the amount is preferably 40% by weight or less. If the viscosity of the high-viscosity base oil is less than 15 cSt, especially 20 cSt
If it is less than, the suppression of the migration phenomenon is insufficient.
On the contrary, if it exceeds 30 cSt, the energy loss of the refrigerator increases, and it is particularly preferably 25 cSt or less. The viscosity of the high-viscosity base oil is 1.5 times or more, preferably 1.8 times or more that of the low-viscosity base oil in order to maintain lubricity.

The refrigerating machine oil used in the compression type refrigerating machine according to the second aspect of the present invention has a kinematic viscosity at 100 ° C. of 5 cSt.
Using a base oil consisting of a polyoxyalkylene glycol derivative represented by the following chemical formula 2 and having a molecular weight of less than 30 cSt, the polyoxyalkylene glycol derivative having a molecular weight of 1.5 times or more the average molecular weight of the polyoxyalkylene glycol derivative. 5 to 45 wt% of the molecule is included.

Embedded image R ₁ —O— (AO) _n —R ₂ where R ₁ is an alkyl group having 1 to 4 carbon atoms, R ₂ is an alkyl group having 1 to 4 carbon atoms or hydrogen, and (AO) _n is It is a polymer group of an oxypropylene group and / or an oxyethylene group, and n is a number representing the average degree of polymerization.

In this embodiment, 5% by weight or more, preferably 5% by weight or more, of molecules of the polyoxyalkylene glycol derivative having a molecular weight of 1.5 times or more the average molecular weight of the polyoxyalkylene glycol derivative (hereinafter also referred to as high molecular weight molecule). When 10% by weight or more is contained, the migration phenomenon is unlikely to occur, and even if it occurs, there is little problem in lubricity. However, if the high molecular weight molecule exceeds 45% by weight, the content of molecules having an average molecular weight is reduced, and a large amount of relatively low molecular weight molecules are included, so that the lubricity during operation of the refrigerator decreases, which is not preferable.

In order to obtain such a molecular weight distribution, it is possible to mix polyoxyalkylene glycol derivatives polymerized under different conditions, or to select polymerization conditions such that the molecular weight has a desired distribution.

The high-viscosity base oil and the low-viscosity base oil used in the present invention can be specified by their distillation characteristics. Usually, the 10% by volume distillation temperature of the high-viscosity base oil is low-viscosity base oil. It is preferably 20 ° C. or higher, especially 25 ° C. or higher than that of oil.

Still another aspect of the present invention is a working fluid for a refrigerator, which contains the above-mentioned refrigerator oil and a hydrofluorocarbon refrigerant. Hydrofluorocarbon refrigerants include 1,1,1,2-tetrafluoroethane (R13
4a), pentafluoroethane (R125), difluoromethane (R32), 1,1,1-trifluoroethane (R143a), 1,1-difluoroethane (R152)
A hydrofluorocarbon refrigerant in which hydrogen of a hydrocarbon having 1 to 2 carbon atoms such as a) is replaced with fluorine is used. The mixing ratio of refrigerating machine oil and refrigerant is usually 10: 90-9 by weight.
0:10, 20:80 to 80:20, especially 2
0:80 to 60:40 is preferable.

The viscosity of the refrigerating machine oil is usually 5 to 500 cSt at 40 ° C., and particularly 4 for refrigerators.
0 ° C. viscosity is 8 to 32 cSt, 40 ° C. viscosity is 25 to 100 cSt for room air conditioners and industrial refrigerators, and 100 ° C. viscosity is 8 to 30 cSt for car air conditioners.

The polyoxyalkylene glycol derivatives represented by Chemical Formulas 1 and 2 used in the present invention are

Embedded image R ₁ —O— (AO) _n —R ₂ , R ₁ is an alkyl group having 1 to 4 carbon atoms, R ₂ is an alkyl group having 1 to 4 carbon atoms or hydrogen, (AO) _n Is required to be a polymer group of oxypropylene group and / or oxyethylene group from the viewpoint of obtaining compatibility with a hydrofluorocarbon refrigerant in a wide temperature range.
From the viewpoint of excellent lubricity, it is particularly preferable that R ₁ is a methyl group and R ₂ is a methyl group or hydrogen. As the high-viscosity, high-molecular weight component, it is preferable to use a diether structure in which R ₂ is a methyl group from the viewpoint of compatibility with the refrigerant.

Further, the polymer group (AO) _n is a block polymer group of oxypropylene group and oxyethylene group or a random polymer group, and it may contain more oxypropylene groups than oxyethylene groups at room temperature. However, it is preferable because the phenomenon of precipitation of fine crystals, that is, "cloudiness" is less likely to occur, the pour point is low, and the hygroscopicity is relatively low. In particular, the polymer group (AO) _n is ((PO) _p (EO)
_When expressed by _q ), it is more preferable that 0.1 ≦ q / (p + q) ≦ 0.3. Here, PO and EO represent an oxypropylene group and an oxyethylene group, respectively,
p and q are numbers showing the average degree of polymerization. The numbers n, p, and q representing the average degree of polymerization are appropriately determined so as to satisfy the predetermined viscosity and molecular weight.

Various additives may be added to the refrigerating machine oil of the present invention. For example, tricresyl phosphate (TCP)
Extreme pressure agents and antiwear agents, such as antioxidants such as ditertiary butyl paracresol (DBPC), acid scavengers such as alkyl or alkenyl or phenyl epoxy polyalkylene glycol derivatives, copper corrosion inhibitors such as benzotriazole, The necessary amount of additives generally known for conventional refrigerating machine oils such as defoaming agents such as silicone oil may be added. Further, a conventionally known base oil for refrigerating machine oil may be mixed to the extent that the function of the refrigerating machine oil of the present invention is not impaired.

[0022]

EXAMPLES Hereinafter, more detailed description will be given based on examples.
The present invention is not limited by these.

Table 1 below shows the structures and characteristics of the low viscosity base oil and the high viscosity base oil used. In addition, the following two-layer separation temperature,
Each base oil and HFC refrigerant (R134a) were mixed at a ratio of 1: 9 for measurement, and the 10 vol% distillation temperature was measured by a gas chromatograph distillation method (ASTM D2877).

[0024]

[Table 1]

Low-viscosity base oil and high-viscosity base oil were mixed in the weight ratios shown in Table 2 to prepare test oils for Examples 1 to 3 and Comparative Examples 1 to 3. Table 2 also shows the kinematic viscosity at 100 ° C. and the two-layer separation temperature. In Comparative Examples 2 and 3 containing 50% by weight or more of high-viscosity base oil, the two-layer separation temperature was low, and it was found that the compatibility with the refrigerant was not sufficient. The test oil contained 0.5% by weight DBPC and TCP to prevent seizure.
1.0 wt% was added.

[0026]

[Table 2]

As the evaluation of the test oil, a durability test 1 corresponding to the normal state and a durability test 2 as the evaluation of the lubricity in the state where migration has occurred were conducted, and the results are shown in Table 3. Durability test 1 is a system in which a motor is connected to a car air conditioner compressor (a reciprocating type refrigeration compressor, in which the working fluid is in contact with iron and aluminum materials), 800 g of R134a refrigerant, and normal charging. The test oil was charged in an amount of 200 g, and after running for a long time under the operating conditions shown in Table 4, the compressor was disassembled and the amount of wear of the rotating shaft was measured.
In endurance test 2, the amount of test oil filled was set to 25 g, which is one eighth of the usual amount, and the amount of wear was measured in the same manner as in endurance test 1 except for that. From Table 3, it can be seen that the test oil of this example has sufficient lubricity. Further, in Comparative Example 1 in which the high-viscosity base oil is not added, it is found that the amount of wear is large and seizure may occur, so that the lubricity required for the operation of the compressor cannot be obtained.

[0028]

[Table 3]

[0029]

[Table 4] Rotation speed: 5000 rpm Discharge side pressure: 19 kg / cm ² G Suction side pressure: 1 kg / cm ² G Superheat degree: 10 ° C Operating time: 200 hours (continuous operation)

[0030]

As described above, according to the present invention, a specific polyoxyalkylene glycol compound is used as the refrigerating machine oil, and the viscosity of the refrigerating machine oil has a small energy loss during operation and a sufficient sealing effect. The viscosity of the range is obtained, and as a part thereof, a high-viscosity base oil, that is, a base oil containing a certain amount or more of a high molecular weight polyoxyalkylene glycol compound is used. As a result, since the refrigerating machine oil portion that is difficult to vaporize is included, a migration phenomenon is unlikely to occur, and problems in lubrication such as wear and seizure can be effectively suppressed.

Claims (3)

[Claims] 1. A low-viscosity base oil 95 to 5 comprising a polyoxyalkylene glycol derivative represented by the following chemical formula 1 having a kinematic viscosity at 100 ° C. of 5 cSt or more and less than 30 cSt.
A base oil obtained by mixing 5% by weight with 5 to 45% by weight of a high-viscosity base oil composed of a polyoxyalkylene glycol derivative represented by the following chemical formula 1 and having a viscosity 1.5 times or more that of the low-viscosity base oil. Refrigerating machine oil for use in a compression type refrigerating machine. Embedded image R ₁ —O— (AO) _n —R ₂ wherein R ₁ is an alkyl group having 1 to 4 carbon atoms, R ₂ is an alkyl group having 1 to 4 carbon atoms or hydrogen, and (AO) _n is It is a polymer group of an oxypropylene group and / or an oxyethylene group, and n is a number representing the average degree of polymerization. 2. A base oil comprising a polyoxyalkylene glycol derivative represented by the following chemical formula 2 having a kinematic viscosity at 100 ° C. of 5 cSt or more and less than 30 cSt is used, and the average molecular weight of the polyoxyalkylene glycol derivative is 1.5. A refrigerating machine oil for use in a compression type refrigerating machine, which contains 5 to 45% by weight of a molecule of the polyoxyalkylene glycol derivative having a double or more molecular weight. Embedded image R ₁ —O— (AO) _n —R ₂ where R ₁ is an alkyl group having 1 to 4 carbon atoms, R ₂ is an alkyl group having 1 to 4 carbon atoms or hydrogen, and (AO) _n is It is a polymer group of an oxypropylene group and / or an oxyethylene group, and _n is a number representing the average degree of polymerization. 3. A working fluid for a refrigerating machine, which comprises the refrigerating machine oil according to claim 1 or 2, and a hydrofluorocarbon refrigerant.