JP2977972B2 - Lubrication method for compression refrigeration system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating method for a compression refrigeration system, and more particularly, to a chlorodifluoromethane (R-134) and a CFC-based refrigerant instead of 1,1,1,2-tetrafluoroethane (R-134a). 22) A method for efficiently lubricating a compression refrigeration system without impairing stability and wear resistance by using a specific hydrocarbon compound and / or polyglycol as a refrigerating machine oil together with a mixed refrigerant comprising About.

[0002]

2. Description of the Related Art
In a compression refrigeration system including a compressor, a condenser, an expansion valve or a capillary tube, and an evaporator, a chlorofluorocarbon-based fluorocarbon compound such as dichlorodifluoromethane (R-12) is mainly used as a refrigerant. Was. In addition, many refrigerating machine oils having no problem have been produced and used in combination therewith. However, these fluorocarbon compounds, which have been conventionally used as refrigerants, are suspected of destroying the ozone layer when released into the atmosphere. It has become That is, 1,1,1,2-tetrafluoroethane (R-134a), 1,1,2,2
-Tetrafluoroethane (R-134b), 1,1-dichloro-2,2,2-trifluoroethane (R-12
3), 1-chloro-1,1-difluoroethane (R-1
42b), 1,1-dichloro-1-fluoroethane (R
Fluorocarbon refrigerants such as -141b) have been developed and put on the market. Among these alternative CFC-based refrigerants, R-134a is currently in a trend of being recommended instead of the conventional R-12. Generally, these alternative Freon-based refrigerants have different properties from conventional Freon-based refrigerants,
It has a drawback of poor compatibility with mineral oil which has been mainly used in conventional Freon-based refrigerants. Therefore, synthetic oils such as polyalkylene glycol compounds (PAG) and ester compounds have been developed and used as refrigerating machine oils suitable for these alternative CFC-based refrigerants (US Pat. No. 4,7,7).
55,316, JP-A-3-33193, etc.). However, these synthetic oils also have some problems with respect to the alternative CFC-based refrigerant. That is, although it has good compatibility with PAG and ester with R-134a as an alternative chlorofluorocarbon-based refrigerant, it has a drawback that stability is not sufficient. In addition, a hydrocarbon compound such as a mineral oil having good stability with respect to R-134a has poor compatibility with R-134a, and a refrigerating machine oil which simultaneously satisfies both requirements of these compatibility and stability is: The fact is that it is hard to find them.

[0003] Accordingly, the present inventor has proposed an R-type refrigerant which is recommended as an alternative chlorofluorocarbon-based refrigerant in a compression refrigeration system.
Intensive research was conducted on the lubrication method when 134a was used as a refrigerant. As a result, they found a method of efficiently lubricating a compression refrigeration system by using a combination of R-22 and R-134a refrigerants and using a specific refrigeration oil. The present invention has been completed based on such findings.

[0004]

That is, the present invention relates to a compression refrigeration system comprising a compressor, a condenser, an expansion valve or a capillary tube, and an evaporator, wherein 1,1,1,2-tetrafluorofluoroethylene is used as a refrigerant. A mixed refrigerant mainly composed of ethane and chlorodifluoromethane is used, and the kinematic viscosity at 40 ° C. is 5 to 500 cS as a refrigerating machine oil.
It is intended to provide a lubrication method for a compression refrigeration system, wherein a hydrocarbon compound and / or polyglycol having an interfacial tension of 8 dyne / cm or more is used.

[0005] Generally, a compression refrigeration system comprises a compressor, a condenser, an expansion valve (or a capillary tube), and an evaporator. As the refrigerating machine oil used in the refrigerating system, generally, a refrigerating machine oil having good compatibility with a refrigerant used in the refrigerating system and having excellent stability is used. However, when using an alternative chlorofluorocarbon refrigerant in the above-mentioned compression refrigeration system, lubricating with refrigeration oil generally used for refrigeration machines results in insufficient wear resistance or insufficient stability. Long-term stable use was not possible. In particular, in a refrigeration system such as an electric refrigerator or a small air conditioner, this tendency is remarkable because a capillary tube is used as an expansion valve. The present invention has successfully and successfully solved such a problem.

First, in the present invention, the refrigerant is 1,1,
1,2-tetrafluoroethane (R-134a) as an alternative chlorofluorocarbon refrigerant (R-134a)
22) is selected and used together. As a result, even if the refrigerant is an alternative CFC-based refrigerant, not only synthetic oil but also mineral oil as the refrigerating machine oil can be lubricated in the compression type refrigerating system without any hindrance to the refrigerating efficiency. In the present invention, R-22 and R-134a are used in combination, and the mixing ratio of R-22 and R-134a may be appropriately selected depending on the situation, and usually R-22 and R-134a are used.
30 to 95% by weight, R-134a at 70 to 5% by weight,
Preferably 50 to 90% by weight of R-22, R-134a
Is determined in the range of 50 to 10% by weight. This mixing ratio is
If R-22 is less than 30% by weight, the vapor pressure becomes low, the refrigeration efficiency becomes poor, and it is easy to separate into two layers, which is not preferable. On the other hand, if R-22 exceeds 95% by weight, the stability becomes poor, which is not preferable. Note that this R-1
In the mixed refrigerant composed of 34a and R-22, one or more of the following first group refrigerant and / or second group refrigerant are blended as a third component refrigerant in a range of less than 1 to 30% by weight. be able to. First group 1,3-dichloro-1,1,2,2,3-pentafluoropropane (R-225cb) 1,1-dichloro-2,2,3,3,3-pentafluoropropane (R-225ca) ) 1,1-Dichlorotrifluoroethane (R-141b) 1-Chloro-1,1-difluoroethane (R-142
b) Chlorotetrafluoroethane (R-124) Second group Difluoroethane (R-152a) Pentafluoroethane (R-125) Trifluoroethane (R-143a) Difluoromethane (R-32) Trifluoromethane (R-23) Here, the first group of refrigerants has an effect of improving the solubility of the refrigerating machine oil, and the second group of refrigerants has an effect of increasing the vapor pressure.

On the other hand, the refrigerating machine oil has a kinematic viscosity at 40 ° C. of 5 to 500 cSt, preferably 10 to 300 cSt, and at the same time having these kinematic viscosities, an interfacial tension (JIS-K-2241) of 8 dyne / d. cm or more, preferably 10 dyne / cm or more hydrocarbon compounds and polyglycols. Here, in hydrocarbon compounds and polyglycols having a kinematic viscosity of less than 5 cSt at 40 ° C., lubricity deteriorates. When the viscosity exceeds 500 cSt, refrigerant and refrigerating machine oil are separated into two layers and lack stability, and at the same time, oil return. Is not preferable because it becomes worse. If the interfacial tension is less than 8 dyne / cm, the hygroscopicity is high and the stability is deteriorated, so that it cannot be used. There are various refrigerating machine oils that can be used in the present invention. Specifically, examples of the mineral oil include hydrocarbon compounds such as a paraffinic mineral oil, an intermediate mineral oil, a naphthenic mineral oil, and an aromatic mineral oil. Further, as synthetic oils, for example, those having 2 to 16 carbon atoms
Olefin (co) polymers (including oligomers), and hydrocarbon compounds such as alkylbenzene and alkylnaphthalene. And polyglycol is
For example, examples of the polyalkylene glycol include polypropylene glycol monomethyl ether, polypropylene glycol monobutyl ether, polypropylene glycol dimethyl ether, and polypropylene glycol dipropyl ether. These refrigerating machine oils are used alone or as a mixture. Furthermore, various additives can be added to these refrigerating machine oils as needed. The additives include phosphate esters,
Including extreme pressure agents such as phosphites, antioxidants, chlorine scavengers, metal deactivators, defoamers, cleaning dispersants, viscosity index improvers, rust inhibitors, corrosion inhibitors, pour point depressants Agents and the like.

In the present invention, R-134a and R-2
2 and the refrigerating machine oil can be used in various mixing ratios, but usually the mixed refrigerant is 50 to 95% by weight,
Refrigeration oil is used in a mixing ratio of 50-5% by weight. By using the mixed refrigerant and the refrigerating machine oil in such a mixing ratio, the compatibility between the two and the lubricating property can be improved. Here, if the refrigerating machine oil is less than 5% by weight, the lubricating property is deteriorated, and if it exceeds 50% by weight, the vapor pressure of the refrigerant is reduced, and the refrigerating efficiency may be reduced.

[0009]

Next, the present invention will be described in more detail based on examples and comparative examples. First, the properties of each refrigerating machine oil used in the examples and comparative examples, the mixing ratio of the alternative mixed CFC refrigerant, and other information are shown in Tables 1 and 2. The interfacial tension and hygroscopicity were measured as follows. 1) Interfacial tension Measured according to JIS-K-2241. 2) Hygroscopicity Take 10 g of refrigerating machine oil in a 50 cc beaker,
After being allowed to stand in a thermo-hygrostat at 85 ° C. and a humidity of 85% for 2 days, the amount of moisture absorbed (% by weight) was measured.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

[0013]

[Table 4]

Examples 1 to 10 and Comparative Examples 1 to 7 In each of the examples and comparative examples, the ratio between the refrigerating machine oil and the refrigerant was 1 unit.
0/90 (weight ratio) and a compression refrigerator (capacity 1) composed of "compressor-condenser-capillary tube-evaporator"
60 W). The test results are:
Table 3 shows the results.

[0015]

[Table 5]

[0016]

[Table 6]

Each performance test was performed as follows. 1) Measurement of two-layer separation temperature Mixing ratio of refrigerant oil and refrigerant (% by weight) = 10/90 2) Measurement of vapor pressure under oil-refrigerant mixing Ratio of refrigerant oil and refrigerant (% by weight) = 10/90 Temperature 40 ° C 3) Measurement of cooling rate of actual machine Freezer temperature of refrigerator (capacity 160W) is -20 ° C
Was evaluated based on the relative cooling rate ratio that reached. 4) Shield tube test: 175 ° C, 10 days, catalyst: Fe, Cu, Al Refrigerant = 1 g, refrigerating machine oil = 4 cc, water = 1 wt% (based on oil) Test method The acid value was measured. 5) Falex abrasion test Refrigerant 10wt% mixed, rotation speed 290rpm, load 300L
Weared at bs for 60 minutes. The test piece used was a standard test piece.

[0018]

As described above, the kinematic viscosity at 40 ° C. is 5 to 5 when R-22 is used in combination with R-134a instead of R-134a.
The use of hydrocarbon compounds and polyglycols with an interfacial tension of 500 cSt and an interfacial tension of 8 dyne / cm or more causes problems in wear resistance, cooling performance and stability, even with synthetic oils, including mineral oils, which are economically advantageous. You can drive without. Therefore, the lubrication method of the present invention is particularly effective in reducing the size of a refrigeration apparatus, and its industrial utility value is high.

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C10M 107/34 C10M 107/34 // C10N 20:00 20:02 30:00 30:06 40:30 (58) Field surveyed (Int. Cl. ⁶ , DB name) C10M 105/02-105/06 C09K 5/04 C10M 101/00-101/04 C10M 107/34 C10N 20:00 C10N 20:02 C10N 40:30 CA (STN)

Claims (1)

(57) [Claims] In a compression refrigeration system comprising a compressor, a condenser, an expansion valve or a capillary tube, and an evaporator, 70 to 5% by weight of 1,1,1,2-tetrafluoroethane and chlorodifluoromethane 30 are used as refrigerants. ~ 95
% By weight as a main component, and a hydrocarbon compound and / or polyglycol having a kinematic viscosity at 40 ° C. of 5 to 500 cSt and an interfacial tension of 8 dyne / cm or more is used as the refrigerating machine oil. The lubrication method for a compression refrigeration system.