JPH04270795A - Refrigerator oil - Google Patents

Abstract

PURPOSE:To develop an oil for refrigerators using cooling media containing R-152a which does not decompose the ozone layer. CONSTITUTION:An oil for refrigerators using cooling media containing 1,1- difluoroethane (R-152a) contains, as a main component, a mixture oil comprising (1) 5-95 pts.wt. of an ester oil synthesized from a 5-15C multi-hydric alcohol and a 3-18C monobasic fatty acid or a mixture of the monobasic fatty acid with a 4-14C multibasic acid, and (2) 95-5 pts.wt. of an alkyl benzene, and a cooling medium comprises the above-mentioned refrigerator oil and a cooling medium containing R-152a. Since the oil has good compatibility with R-152a and has excellent lubricity, thermal stability, electric insulation, hydrolysis resistance, etc., the oil can suitably be used as a lubricating oil for the refrigerators using R-152a as a cooling medium.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a new refrigerant, refrigeration oil, and more specifically, dichlorodifluoromethane (hereinafter referred to as R-12), which is a refrigerant whose use is regulated due to the problem of ozone destruction caused by fluorocarbons. 1,1-difluoroethane (hereinafter referred to as R-152a), a chlorine-free hydrofluorocarbon that is considered as a substitute for
), or the above R-152a and monochlorodifluoromethane (hereinafter abbreviated as R-22) and 1,2-dichloro-1,1,2,2-tetrafluoroethane (hereinafter referred to as R-
114) or R-152a and R-
R-152, consisting of 22 and 1-chloro-1,2,2,2-tetrafluoroethane (hereinafter abbreviated as R-124)
The present invention relates to a refrigerating machine oil that has excellent compatibility with a three-type mixed refrigerant containing a and has excellent properties such as lubricity and stability.

0002

2. Description of the Related Art Generally, a compression type refrigerator is composed of a compressor, a condenser, an expansion valve, and an evaporator, and a mixture of refrigerant and lubricating oil is circulated within this sealed system. During lubrication, the refrigerant and lubricating oil reach a temperature of over 50°C in the compressor, and a low temperature of around -40°C in the cooler, so this -40°C
It is necessary that they be compatible without separation in a temperature range of ~+50°C. If phase separation occurs during operation, it will cause seizure of the compressor and decrease in efficiency of the evaporator, which will have a significant negative impact on the lifespan and efficiency of the equipment.

[0003] Furthermore, it is important for refrigerating machine oil to have a viscosity that can maintain an oil film necessary for lubrication, especially at high temperatures. Normally, the viscosity of lubricating oil before mixing with refrigerant is 2 to 50 cSt at 100°C.
is preferred. If the viscosity is lower than this, the oil film will be thinner and lubrication failure will easily occur, and if it is higher than this, the efficiency of heat exchange will decrease. Furthermore, since it is used in a wide temperature range, it is preferable that the viscosity index is high, and a viscosity index of 40 or more is usually required. Furthermore, other performance requirements include stability in a refrigerant atmosphere, low hygroscopicity to prevent the expansion valve from clogging due to icing, and high electrical insulation in the case of a compressor with a built-in motor.

Chlorofluoroalkanes, commonly called chlorofluorocarbons, are widely used as refrigerants for refrigerators. Among them, R-12 (dichlorodifluoromethane) is particularly used, but chlorofluorocarbons such as R-12, in which all of the hydrogen in the hydrocarbon is replaced with fluorine and chlorine, destroy the ozone layer. Due to the risk of environmental pollution, regulations have recently become stricter around the world. Therefore, new refrigerants such as R-152a, which does not contain chlorine, and R-152a
Mixed fluorocarbon refrigerants containing, for example, R-22 and R-15
Three types of refrigerant mixture of 2a and R-114, R-22 and R-15
Three types of mixed refrigerants such as 2a and R-124 have been proposed. These refrigerants have little risk of destroying the ozone layer, and can be used without changing the structure of conventional refrigerators.
Since it can be substituted for R-12, it is expected to be put to practical use in refrigerators and car air conditioners.

However, when using such a new refrigerant R-152a as an alternative to R-12 or the above-mentioned three-type mixed refrigerant containing it, the conventional lubricating oil that has been used together with R-12, namely , paraffinic mineral oil, naphthenic mineral oil, alkylbenzene, etc. cannot be used because they have poor compatibility with refrigerants.

[0006]

[Problems to be Solved by the Invention] Therefore, the present invention provides R-1
It has good compatibility with 52a and the above-mentioned mixed refrigerants containing it over the entire operating temperature range, has stability in a fluorocarbon atmosphere, low hygroscopicity, high electrical insulation, and has excellent hydrolysis resistance. The purpose was to provide good quality refrigeration oil.

[0007]

[Means for Solving the Problems] The present inventors have discovered that a lubricating oil mainly composed of a mixture of a specific ester and alkylbenzene has excellent compatibility with R-152a or a mixed refrigerant containing R-152a, The present invention has been completed based on the discovery that the above-mentioned object can be met. That is, the first invention of the present invention is: (1) an ester oil synthesized from a polyhydric alcohol having 5 to 15 carbon atoms and a monovalent fatty acid having 3 to 18 carbon atoms;
The second invention is a refrigerating machine oil for a refrigerant containing 1,1-difluoroethane whose main component is a mixed oil of ~95 parts by weight and ■95 to 5 parts by weight of alkylbenzene. 15 polyhydric alcohols and 1 carbon number 3-18
Complex ester oil 5-95 synthesized from a mixed carboxylic acid of a fatty acid and a polybasic acid having 4 to 14 carbon atoms
This is a refrigerating machine oil for refrigerants containing 1,1-difluoroethane whose main component is a mixed oil of 1.1 parts by weight and 95 to 5 parts by weight of alkylbenzene. The present invention also includes a refrigerant obtained by mixing a refrigerant containing 1,1-difluoroethane and the above-mentioned refrigerating machine oil.

The polyhydric alcohol having a carbon number of 15 or less is used as a raw material for the alcohol component for synthesizing the ester oil constituting the refrigerating machine oil composition of the present invention. Polyhydric alcohols having 16 or more carbon atoms are not preferred as refrigerating machine oils because the hydrocarbon portion of the alcohol itself becomes too large, and the synthesized esters have poor compatibility with new refrigerants such as R-152a. The polyhydric alcohol used in the present invention is preferably a polyhydric alcohol having a neo-type carbon structure such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, dipentaerythritol, tripentaerythritol. ,
Among them, neopentyl glycol, trimethylolpropane and pentaerythritol are particularly preferred. These polyhydric alcohols can be used alone or in combination of two or more types for esterification.

[0009] Furthermore, monovalent fatty acids having 3 to 18 carbon atoms are used as essential components as acid component raw materials for the above-mentioned ester oil synthesis. When the number of carbon atoms is small, the strength of the acid generated during hydrolysis is strong, and the effect of damage to equipment is large.On the other hand, when the number of carbon atoms is 19 or more, the compatibility with new refrigerants becomes extremely poor. More preferred monovalent fatty acids are linear or branched fatty acids having 3 to 10 carbon atoms. 1 like this
Examples of fatty acids 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
-trimethylhexanoic acid, decanoic acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, palmitooleic acid, stearic acid, isostearic acid, oleic acid,
These include linoleic acid and linolenic acid. These monovalent fatty acids can be subjected to the esterification reaction either singly or as a mixture of two or more.

The alkylbenzene which is the other component of the lubricating oil composition used in the present invention preferably has a kinematic viscosity of 5 to 50 cSt at 40°C, more preferably 5 to 40 cSt. As these alkylbenzenes, monoalkylbenzenes or dialkylbenzenes represented by the following formulas, or mixtures thereof are preferably used. (Ph)R1 R2 In the formula, Ph is a phenylene group, and R1 is an alkyl group, preferably a C8 to C24 branched alkyl group. R2 is hydrogen or a C8 to C24 alkyl group, preferably hydrogen. Branched alkylbenzenes are superior to linear alkylbenzenes in terms of compatibility with new refrigerants such as R-152a. Furthermore, in addition to the above, products mixed with trialkylbenzenes, tetraalkylbenzenes, etc. can be used as long as they have an appropriate viscosity, so by-products from the production of certain alkylbenzenes can also be used.

[0011] In addition, in the present invention, the above-mentioned monovalent fatty acid having 3 to 18 carbon atoms is used as an ester oil.
A mixed carboxylic acid mixed with 4 polybasic acids is used as an acid component,
A complex ester oil synthesized by reaction with a polyhydric alcohol having 5 to 15 carbon atoms can be used. Polybasic acids having 3 or less carbon atoms are special products, difficult to obtain at low cost, and the stability of the ester after synthesis is poor, so they are not preferred as raw materials for complex ester synthesis. In addition, polybasic acids having 15 or more carbon atoms are R-
This is not preferable because the compatibility with 152a etc. is significantly reduced. A carbon number of 4 to 14 is preferable, and R-
In order to ensure compatibility with 152a etc., the number of carbon atoms is 4 to 1.
0 is 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. When these polybasic acids and the monovalent fatty acid described above 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.

[0012] The complex ester is presumed to have a structure in which multiple polyhydric alcohols and polybasic acids are alternately connected by ester bonds, and the remaining hydroxyl groups are esterified and blocked by monovalent fatty acids. The larger the ratio of polybasic acid to monovalent fatty acid, the higher the molecular weight and higher viscosity of an ester obtained. An ester of any viscosity can be obtained by changing the proportion of polybasic acid, but in order to avoid too high a viscosity and minimize the amount of residual hydroxyl groups, the proportion of polybasic acid should be 80 mol% of the total acid. It is preferable to do the following.

These esters are compatible with new refrigerants such as R-152a when used alone, but they have high hygroscopicity, insufficient electrical insulation, and poor hydrolysis resistance. By mixing alkylbenzenes with a specific structure in a specific ratio, electrical insulation properties and hydrolysis resistance can be significantly improved while maintaining compatibility with new refrigerants such as R-152a. In other words, the present invention, which consists of an alkylbenzene and an ester, improves the hydrolysis resistance and electrical insulation properties of the ester, and improves the low viscosity index and poor lubrication performance, which are the shortcomings of alkylbenzenes.

The blending ratio of ester and alkylbenzene in the refrigerating machine oil of the present invention is 5 to 95 parts by weight of ester and 95 to 5 parts by weight of alkylbenzene. This ratio is determined by the type of refrigerant and the level of compatibility required by the equipment used. In other words, the greater the amount of alkylbenzene blended within the range that ensures the level of compatibility, the lower the hygroscopicity, the higher the electrical insulation, and the more economically advantageous it becomes. However, unless each component is blended in an amount of 5% by weight or more, its properties will not be exhibited. For example, alkylbenzene alone has a very narrow range of compatibility with new refrigerants such as R-152a and cannot be used practically, but by mixing the above esters, they become compatible and the lubricity is greatly improved. Also,
Ester alone has high hygroscopicity and poor electrical insulation, but
By mixing alkylbenzenes, their properties are significantly improved.

The refrigerating machine oil of the present invention containing a mixture of ester and alkylbenzene as a main component may be a single refrigerant R-152a or a mixture of three refrigerants (R-22, R-152a and R-1).
14 or a mixture of R-22, R-152a, and R-124), it exhibits good mutual solubility in a wide range from low to high temperatures, and has good lubricating performance, thermal stability, It can be suitably used because it has excellent electrical insulation, low hygroscopicity, and high hydrolytic stability.

When the refrigerating machine oil of the present invention is added as a lubricating oil for a refrigerant, the amount added depends on the type of refrigerant and refrigerating machine oil,
Although it varies depending on the type of refrigerator, usually the refrigerant is 90 to 1
10 to 90 parts by weight of refrigerating machine oil is preferable to 0 parts by weight.

It goes without saying that the refrigerating machine oil according to the present invention can be mixed with any lubricating oil such as synthetic oil or mineral oil as long as it satisfies its function as a refrigerating machine oil. Additives such as antioxidants, anti-wear agents, and epoxy compounds may be added as appropriate.

[0018]

[Examples] The present invention will be explained in more detail with reference to Examples below. Examples 1 to 6, Synthesis of Ester Ester, which is one component of the refrigerating machine oil of the present invention, was synthesized as follows. In the case of preparing refrigeration oil a, 2-ethylhexanoic acid as a monovalent fatty acid and neopentyl glycol as a polyhydric alcohol in a ratio such that the amount of carboxyl groups in the mixture and the amount of hydroxyl groups in the alcohol are equal,
The mixture was placed in a four-bottle flask equipped with a stirring bar, nitrogen gas blowing tube, thermometer, and water separator with a condenser, and the esterification reaction was carried out at 230°C under a nitrogen stream for 8 hours while distilling the produced water out of the system. After that, reduce the pressure (2 to 3 mm
Hg) and reacted at the same temperature for 2 hours to obtain an ester. Similarly, one or more monovalent fatty acids shown in Table 1 or a mixture of a monovalent fatty acid and a polybasic acid were used instead of 2-ethylhexanoic acid, and the equivalent amount of the polyhydric alcohol shown in Table 1 was used. Various esters were synthesized by reaction.

Two kinds of alkylbenzene, manufactured by Mitsubishi Yuka, with a viscosity of 10 cSt or 40 cSt at 40° C., were used as the branched alkylbenzene.
In addition, the linear alkylbenzene is 40cS manufactured by Ys Chemical Co., Ltd.
t was used.

Performance evaluation of refrigerating machine oil Refrigerating machine oils a to f were obtained by mixing the various esters listed in Table 1 obtained by the above method and branched or linear alkylbenzenes in the proportions shown in Table 1. Viscosity, hygroscopicity, seizure load,
Performance as a refrigerating machine oil such as volume resistivity was evaluated, and the results are shown in Table 2.

Performance evaluation in mixed state with refrigerant Next, using refrigerating machine oils a to f, R-152a alone and three types of mixed refrigerant A (R-22/R-152a/R-114=2
7/19/54 weight ratio), and three-type mixed refrigerant B (R-
22/R-152a/R-124 = 31/24/45 weight ratio), the compatibility when mixed with each refrigerant, and the thermal stability and hydrolytic stability when mixed with R-152a alone were evaluated. . The results are shown in Table 3.

Comparative Examples 1 to 5 For comparison, alkylbenzene alone, ester alone and dioctyl sebacate, which are one component of the refrigerating machine oil of the present invention, were used and evaluated as refrigerating machine oil and as a refrigerant in the same manner as in the examples. The performance was evaluated in a mixed state. Note that dioctyl sebacate was manufactured by Nippon Oil & Fats. The results are shown in Tables 2 and 3.

The physical properties of the refrigerating machine oil in Examples and Comparative Examples were measured as follows. Lubricity In accordance with ASTM D-3233-7, Falex seizure load was measured under a controlled atmosphere of R-152a blowing (70 ml/min).

Compatibility test oil 0.6g and refrigerant (R-152a, three-type mixed refrigerant A
and B) 2.4g are sealed in a glass tube,
Cooling was performed at a rate of 1° C. per minute, and the temperature at which two-layer separation occurred at low temperature, that is, the two-layer separation temperature, was measured.

Thermal stability According to ANSI/ASHRAE 97-1983, 1 g of sample oil, 1 g of refrigerant (R-152a) and catalyst (iron, copper,
After enclosing each aluminum wire) into a glass tube,
Heated to 175°C, and after 10 days, the hue of the sample oil was determined by ASTM
Judgment was made based on the display.

[0026] Electrical insulation JIS C2101 volume resistivity test at 80°C was conducted.

Hygroscopicity: 60 g of sample oil was placed in a 100 ml beaker in an atmosphere with a temperature of 25° C. and humidity of 70%, and evaluation was made based on the water concentration after 3 hours of being left open.

Hydrolytic Stability According to ANSI/ASHRAE 97-1983, 7 g of sample oil with water content adjusted to 1000 ppm and refrigerant (R-
152a) 3g and catalyst (iron, copper, aluminum wire)
was sealed in a glass tube, heated to 175°C, and
Four days later, the total acid value (mgKOH/g) of the sample oil was measured. The total acid value of all sample oils before the test was 0.01 mgK.
It was OH/g.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032] From the evaluation results shown in Tables 2 and 3, alkylbenzenes alone have the disadvantage of low compatibility with new refrigerants and low lubricity as shown by seizure load, and esters alone have low compatibility with new refrigerants. Although it is soluble, it has the disadvantages of high hygroscopicity, low volume resistivity, that is, low electrical insulation, and poor hydrolytic stability. On the other hand, the refrigerating machine oil of the present invention is a novel refrigerant R
It can be seen that the performance is overall superior to that of -152a.

[0033]

Effects of the Invention The refrigerating machine oil of the present invention, which is composed of a specific ester and alkylbenzene, not only has good compatibility with R-152a, but also has good lubricity, thermal stability, electrical insulation, and hydrolysis resistance. Therefore, it can be suitably used as a lubricating oil for refrigerators that use refrigerants containing R-152a, which is expected to be a refrigerant that does not destroy the ozone layer.

Claims (6)

[Claims] Claim 1: Mixed oil of ■5 to 95 parts by weight of ester oil synthesized from polyhydric alcohol having 5 to 15 carbon atoms and monovalent fatty acid having 3 to 18 carbon atoms, and ■95 to 5 parts by weight of alkylbenzene. A refrigerating machine oil for refrigerants containing 1,1-difluoroethane, the main component of which is 1,1-difluoroethane. Claim 2: ■ Complex ester oil 5~ synthesized from a polyhydric alcohol having 5 to 15 carbon atoms, a mixed carboxylic acid of a monovalent fatty acid having 3 to 18 carbon atoms, and a polybasic acid having 4 to 14 carbon atoms. 95 parts by weight and ■9 alkylbenzene
A refrigerating machine oil for refrigerants containing 1,1-difluoroethane, the main component of which is a mixed oil of 5 to 5 parts by weight. 3. The refrigerant containing 1,1-difluoroethane is 1,1-difluoroethane alone, or monochlorodifluoromethane, 1,1-difluoroethane and 1,1-difluoroethane.
, 2-dichloro-1,1,2,2-tetrafluoroethane, or monochlorodifluoromethane, 1,1-difluoroethane and 1-chloro-
The refrigerating machine oil according to claim 1 or 2, which is a ternary mixed refrigerant consisting of 1,2,2,2-tetrafluoroethane. 4. (A) a refrigerant containing 1,1-difluoroethane, and (B) ■ an ester oil synthesized from a polyhydric alcohol having 5 to 15 carbon atoms and a monovalent fatty acid having 3 to 18 carbon atoms; A refrigerant made by mixing a lubricating oil whose main components are a mixture of 95 parts by weight and 95 to 5 parts by weight of alkylbenzene. [Claim 5] (A) a refrigerant containing 1,1-difluoroethane; (B) ■ a polyhydric alcohol having 5 to 15 carbon atoms; a monovalent fatty acid having 3 to 18 carbon atoms; A refrigerant made by mixing 5 to 95 parts by weight of a complex ester oil synthesized from a mixed carboxylic acid with a polybasic acid, and a lubricating oil whose main components are a mixed oil of 95 to 5 parts by weight of alkylbenzene. 6. The refrigerant containing 1,1-difluoroethane is 1,1-difluoroethane alone, or monochlorodifluoromethane, 1,1-difluoroethane and 1,1-difluoroethane.
, 2-dichloro-1,1,2,2-tetrafluoroethane, or monochlorodifluoromethane, 1,1-difluoroethane and 1-chloro-
The refrigerant according to claim 4 or 5, which is a ternary mixed refrigerant consisting of 1,2,2,2-tetrafluoroethane.