JP2683170B2 - Refrigerating machine oil - Google Patents

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 for a novel refrigerant, and more specifically, it contains monochlorodifluoromethane (hereinafter referred to as "R-22") which is considered to be a refrigerant containing chlorine and decomposing to destroy the ozone layer. It contains difluoromethane (hereinafter abbreviated as R-32), which is a hydrofluorocarbon that does not contain chlorine, and pentafluoroethane (hereinafter abbreviated as R-125), which are expected to be alternatives such as Excellent compatibility with refrigerant, lubricity,
The present invention relates to a refrigerating machine oil having excellent properties such as stability.

[0002]

2. Description of the Related Art In general, a compression refrigerator comprises a compressor, a condenser, an expansion valve, and an evaporator, and a mixture of refrigerant and lubricating oil circulates in this sealed system. Refrigerant and lubricating oil
During the circulation, the temperature in the compressor becomes 50 ° C. or higher, and the temperature in the cooler becomes as low as about −40 ° C.
It is necessary that they be compatible without separation in a temperature range of from 0 ° C to + 50 ° C. If phase separation occurs during operation,
This may cause seizure of the compressor and decrease the efficiency of the evaporator, which has a significant adverse effect on the life and efficiency of the device.

[0003] In addition, viscosity of a refrigerating machine oil that can maintain an oil film necessary for lubrication at high temperatures is important. Usually, the viscosity of the lubricating oil before mixing with the refrigerant is 2 to 50 cSt at 100 ° C.
If the viscosity is lower than this, the oil film becomes thin and lubrication failure easily occurs, and if the viscosity is higher, the efficiency of heat exchange decreases.
Also, refrigeration oil is used in a wide temperature range,
The viscosity index is preferably high, and usually a viscosity index of 40 or more is required. Further, as other performances, stability in a chlorofluorocarbon atmosphere, low hygroscopicity for preventing blockage of the expansion valve due to icing, and high electrical insulation for a compressor with a built-in motor are required.

As refrigerants for refrigerators, chlorofluoroalkanes and hydrochlorofluoroalkanes, commonly called Freon, are widely used. Among them, especially R
-22 is widely used for air conditioners and industrial use. However, hydrochlorofluoroalkanes such as R-22, although somewhat smaller than chlorofluoroalkanes having no hydrogen in the molecule, contain chlorofluoroalkanes because they contain chlorine in the molecule. In recent years, there has been a tendency for the regulation to become stricter worldwide because of the possibility of causing environmental pollution such as destruction of the ozone layer together with species. Therefore, R-32 (difluoromethane) and R-125 (pentafluoroethane), which are chlorine-free hydrofluorocarbons as new refrigerants, and those and 1,1-difluoroethane (hereinafter, R-
A mixed refrigerant with 1,1,1,2 tetrafluoroethane (abbreviated as 152a) (hereinafter abbreviated as R-134a) and the like have been proposed. These refrigerants have a low risk of destruction of the ozone layer and can be replaced with R-22 with almost no change in the structure of the conventional refrigerator. Is expected to be put to practical use. However, when using the novel refrigerants R-32 and R-125 which are regarded as such R-22 substitutes, or the above-mentioned mixed refrigerants containing them, the lubrication conventionally used together with R-22. Oils, that is, paraffinic mineral oils, naphthenic mineral oils, alkylbenzenes and the like, have poor compatibility with new refrigerants and cannot be used at all.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides an R-
The compatibility with the mixed refrigerant containing 32 and R-125 is good over the entire operating temperature range, and it has stability in a CFC atmosphere, low hygroscopicity, high electrical insulation, and hydrolysis resistance. The purpose is to provide a good refrigerating machine oil.

[0006]

The present inventors have found that refrigerating machine oils containing a specific ester as a main component are R-32 and R-12.
The inventors have found that they have excellent compatibility with a mixed refrigerant containing 5 and can meet the above-mentioned objects, and have completed the present invention.

That is, the first invention of the present invention is a compound synthesized from at least one polyhydric alcohol selected from neopentyl glycol, trimethylolpropane and pentaerythritol and a monohydric fatty acid having 3 to 12 carbon atoms , and 2
Volume resistivity at 5 ° C is 10 ¹³ to 10 ¹⁴ Ω · cm Oh
A refrigerating machine oil for a refrigerant containing a mixture of difluoromethane and pentafluoroethane as a main component an ester oil which is loaders, second invention,

At least one polyhydric alcohol selected from neopentyl glycol, trimethylolpropane and pentaerythritol and 1 to 3 carbon atoms.
It is synthesized from valence fatty acid and mixed acids of polybasic acid having a carbon number of 4 to 14, 10 ¹³ no volume resistivity at 25 ° C.
A refrigerating machine oil for a refrigerant containing a mixture of difluoromethane and pentafluoroethane containing a complex ester oil of the order of 10 ¹⁴ Ω · cm as a main component.

Neopentyl glycol, trimethylolpropane or pentaerythritol is used as the dihydric or higher polyhydric alcohol which is a raw material for the alcohol component for synthesizing the ester oil which is the main component of the refrigerator oil composition of the present invention. Polyhydric alcohols having more carbon atoms than this are preferable because the hydrocarbon portion of the alcohol itself becomes too large, and the synthesized ester has poor compatibility with new refrigerants such as R-32 and R-125. Absent. These polyhydric alcohols may be used alone or in combination of two or more for esterification.

Further, as the acid component raw material for the ester oil synthesis, a monovalent fatty acid having 3 to 12 carbon atoms is used as an essential component. If the number of carbon atoms is small, the strength of the acid generated upon hydrolysis is strong, and the influence of damage or the like on the apparatus is large. Conversely, if the number of carbon atoms is 13 or more, the compatibility with the new refrigerant becomes extremely poor. More preferred monovalent fatty acids are straight-chain or branched ones having 3 to 10 carbon atoms. Such one
Examples of the trivalent fatty acid include propionic acid, isopropionic acid, butanoic acid, isobutanoic acid, pentanoic acid, isopentanoic acid, hexanoic acid, heptanoic acid, isoheptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, 3,5,5 5
-Trimethylhexanoic acid, decanoic acid, undecanoic acid, lauric acid etc. These monovalent fatty acids can be subjected to the esterification reaction either as a single type or as a mixture of two or more types.

Further, in the present invention, as the ester oil, one fatty acid having 3 to 12 carbon atoms and 4 to 14 carbon atoms are added.
Multi base acid mixed with mixed carboxylic acid components can be used complex ester oils which are synthesized by the reaction of a multi <br/> valent alcohols. Polybasic acids having 3 or less carbon atoms are special products, are difficult to obtain at low cost, and are inferior in stability of the ester after synthesis, which is not preferable. Further, polybasic acids having 15 or more carbon atoms are R-32 and R-
The compatibility with 125 and the like is significantly reduced, which is not preferable. Of these polybasic acids, R-32 is used in a wider range.
In order to ensure compatibility with R-125, etc., the number of carbon atoms is 4
To 10 are particularly preferred. Examples of such polybasic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, maleic acid and trimellitic acid. Then, when these polybasic acids and the above-mentioned monohydric fatty acids are simultaneously reacted with a polyhydric alcohol, a complex ester, which is one of the materials for the refrigerating machine oil of the present invention, can be synthesized.

It is presumed that the complex ester has a structure in which a plurality of polyhydric alcohols and polybasic acids are alternately connected by ester bonds, and the remaining hydroxyl groups are esterified and blocked by monovalent fatty acids. As the ratio of the polybasic acid to the monovalent fatty acid is larger, an ester having a higher molecular weight and a higher viscosity can be obtained. An ester having an arbitrary viscosity can be obtained by changing the proportion of the polybasic acid. However, in order to avoid a viscosity that is too high and minimize the amount of residual hydroxyl groups, the proportion of the polybasic acid is set to 80 mol% of the entire acid. It is preferable to set the following.

[0013] The ester oil used in the present invention is at 25 ° C.
Has a volume resistivity of 10 ¹³ Or 10 ¹⁴ Ω · cm order
It has a high value and therefore a high electrical insulation.

The refrigerating machine oil containing an ester as a main component of the present invention is a mixed refrigerant of the refrigerants R-32 and R-125, or R-152a (1,1-difluoroethane) and R-152a (1,1-difluoroethane).
As a lubricating oil for refrigerators that use a mixed refrigerant with -134a (1,1,1,2 tetrafluoroethane), they show good mutual solubility in a wide range from low temperature to high temperature, and have lubricating performance and thermal stability. Since it has excellent properties and electrical insulation, has low hygroscopicity and high hydrolysis stability, it can be suitably used.

When the refrigerating machine oil of the present invention is added as a lubricating oil for a refrigerant, the amount of addition thereof varies depending on the kind of the refrigerant and the refrigerating machine oil and the kind of the refrigerator, but usually the refrigerant 90 to 10
Refrigerating machine oil is preferably 10 to 90 parts by weight with respect to parts by weight.

[0016] Incidentally, in the refrigerating machine oil according to the present invention, in the range satisfying the functions as a refrigerating machine oil, it goes without saying that the synthetic oil and lubricants such as mineral oil can be appropriately mixed, also conventionally, used in the refrigeration machine oil Additives such as known antioxidants, antiwear agents, and epoxy compounds may be added as appropriate.

[0017]

The present invention will be described more specifically with reference to the following examples. Production Examples 1 to 6 (Synthesis of Ester) The polyhydric alcohol shown in Table 1 and the monovalent fatty acid shown in Table 1 or a mixture thereof with a polybasic acid are mixed, and the carboxyl group in the organic acid in this mixture is mixed. And a proportion of the amount of hydroxyl groups in the alcohol to be the same amount, the mixture was charged into a four-necked flask equipped with a stirring rod, a nitrogen gas blowing tube, a thermometer and a water separator with a cooler, and the temperature was 8 at 230 ° C under a nitrogen stream. time,
The esterification reaction was carried out while distilling off the generated water out of the system, and then the reaction was carried out at a reduced pressure (2 to 3 mmHg) at the same temperature for 2 hours to obtain esters a to f.

[0018]

[Table 1]

Examples 1 to 6 (Performance evaluation of refrigerating machine oil) Various esters a to Table 1 obtained in Production Examples 1 to 6
f was evaluated for performance as a refrigerating machine oil such as kinematic viscosity, hygroscopicity, baking load, volume resistivity, and the results are shown in Table 2.

[0020] The following refrigerating machine oil a to f (Performance Evaluation in the mixed state with the refrigerant) in admixture with various refrigerants were evaluated compatibility, thermal stability and hydrolytic stability. The results are shown in Table 2.

Comparative Examples 1 to 5 For comparison, mineral oil type refrigerating machine oil, alkylbenzene (manufactured by Mitsubishi Yuka, Pansolv H) and dioctyl sebacate commercially available as ester and two other esters, Unistar H381 and Unistar C3373 (above) Both were manufactured by Nippon Oil & Fat Co., Ltd., and evaluation as a refrigerating machine oil and performance evaluation in a mixed state with a refrigerant were performed by the same method as in the examples. Table 3 shows the results.

[0022] Note that measurements of the physical properties of the refrigerating machine oil in Examples and Comparative Examples are as follows. Lubricity (seizing load) In accordance with ASTM D-3223-7, Falex seizing load was measured under a controlled atmosphere of R-125 (70 ml / min).

The electrically insulating (volume resistivity) was based on the volume resistivity test at 25 ° C. in JIS C2101.

The compatibility (two-layer separation temperature) sample oil 0.6g refrigerant and (R-32, R-125 , mixed refrigerant A, mixed refrigerant B and mixed refrigerant C) 2.4 g was sealed in a glass tube After that, cooling was performed at 1 ° C. per minute, and a temperature at which low temperature two-layer separation occurred, that is, a double-layer separation temperature was measured.

The mixed refrigerant A is R-32 and R-134a.
And 8: 2 (weight ratio, same below), mixed refrigerant B is R-1
25 and R-152a are mixed at 8: 2, and mixed refrigerant C is a mixed refrigerant in which R-32, R-125 and R-134a are mixed at 5: 4: 1.

[0026] according to the thermal stability (Hue) ANSI / ASHRAE 97-1983, enclosed sample oil 1g and refrigerant (R-32 and R-125) 1g and catalyst (iron, copper, each line of aluminum) in a glass tube After that, it was heated to 175 ° C., and after 10 days, the hue of the sample oil was judged by ASTM display.

[0027] according to the hydrolytic stability ANSI / ASHRAE 97-1983, subjected to control the water to 1000ppm試油7g and refrigerant (R-3
2) 3 g and the catalyst (each wire of iron, copper and aluminum) were sealed in a glass tube, heated to 175 ° C., and 14 days later, the total acid value (mg KOH / g) of the test oil was measured. The total acid value of the test oil before the test was 0.01 mg KO.
H / g.

[0028]

[Table 2]

[0029]

[Table 3]

From the evaluation results shown in Table 2, the refrigerating machine oil of the present invention has excellent compatibility with the novel refrigerants R-32 and R-125, good hydrolysis resistance, good electrical insulation and high lubricity. It can be seen that the performance is excellent overall.

[0031]

INDUSTRIAL APPLICABILITY The refrigerating machine oil of the present invention comprising a specific ester is excellent in lubricity, thermal stability, electric insulation, hydrolysis resistance, etc., as well as compatibility with R-32 and R-125. R-32, R-125 that does not destroy the ozone layer
Since it can be suitably used as a lubricating oil for a refrigerator using a refrigerant containing, it greatly contributes to solving environmental problems.

Claims (4)

(57) [Claims] 1. At least one polyhydric alcohol selected from neopentyl glycol, trimethylolpropane and pentaerythritol and 1 to 3 carbon atoms.
It is synthesized from polyvalent fatty acid and has a volume resistivity of 10 ¹³ at 25 ℃.
Refrigerating machine oil for a refrigerant containing a mixture of difluoromethane and pentafluoroethane whose main component is an ester oil of the order of 10 ¹⁴ Ω · cm . 2. The refrigeration according to claim 1, wherein the mixed refrigerant of difluoromethane and pentafluoroethane is a refrigerant further containing 1,1-difluoroethane and / or 1,1,1,2-tetrafluoroethane. Machine oil. 3. A mixed carvone of at least one polyhydric alcohol selected from neopentyl glycol, trimethylolpropane and pentaerythritol, a monovalent fatty acid having 3 to 12 carbon atoms and a polybasic acid having 4 to 14 carbon atoms. is synthesized from acid, is 10 ¹³ volume resistivity at 25 ° C.
Refrigerating machine oil for a refrigerant containing a mixture of difluoromethane and pentafluoroethane whose main component is a complex ester oil of the order of 10 ¹⁴ Ω · cm . 4. The refrigeration according to claim 3, wherein the mixed refrigerant of difluoromethane and pentafluoroethane is a refrigerant further containing 1,1-difluoroethane and / or 1,1,1,2-tetrafluoroethane. Machine oil.