JP2554737B2 - Refrigeration oil for fluorinated alkane refrigerants - Google Patents

Description

The present invention relates to a refrigerating machine oil for a fluoroalkane refrigerant. More specifically, 1,1,1,2-tetrafluoroethane (hereinafter referred to as Freon 134a, which can substitute for Freon compounds such as dichlorodifluoromethane (hereinafter referred to as Freon 12), which is a problem in environmental pollution, is referred to as Freon 134a. Refrigerating machine oil for fluorinated alkane refrigerants, which has a good compatibility with hydrogen-containing CFC compounds (fluorinated alkanes) such as It is about.

[Problems to be Solved by Prior Art and Invention]

Generally, a refrigerator, particularly a compression refrigerator, is composed of a compressor, a condenser, an expansion valve, and an evaporator, and has a structure in which a mixed liquid of a refrigerant and lubricating oil circulates in this closed system. In such a refrigerator, although it depends on the type of device, in general, the temperature in the compressor is 50 ° C. or higher,
Since the temperature in the cooler is as low as -40 ° C, it is usually necessary to circulate the refrigerant and the lubricating oil in this system without phase separation in the temperature range of -40 ° C to + 50 ° C. If phase separation occurs during operation of the refrigerator, it will have a significant adverse effect on the life and efficiency of the device. For example, if phase separation of the refrigerant and lubricating oil occurs in the compressor part, poor lubrication of the moving parts may cause seizure, etc., which significantly shortens the life of the device, while phase separation occurs in the evaporator. However, the presence of high-viscosity lubricating oil causes a decrease in heat exchange efficiency.

Further, since the refrigerating machine oil (lubricating oil for refrigerating machine) is used for the purpose of lubricating the moving parts of the refrigerating machine, the lubrication performance is naturally important. In particular, since the temperature inside the compressor becomes high, the viscosity that can hold the oil film necessary for lubrication is important. The required viscosity depends on the type of compressor used and operating conditions, but the viscosity of the lubricating oil before mixing with the refrigerant is usually 10
2 to 50 cSt at 0 ° C. and particularly 2 to 25 cSt are preferable. If the viscosity is lower than this, the oil film becomes thin, and poor lubrication is likely to occur. If the viscosity is higher, the efficiency of heat exchange decreases. Further, the lubricating oil for a refrigerator is preferably circulated and used in a low temperature range from high temperature to low temperature, so that it preferably has a high viscosity index, and a viscosity index of 40 or more is usually required. Furthermore, as other performance,
Low hygroscopicity is required to prevent the expansion valve from blocking due to freezing.

Conventionally, Freon 12 is often used as a refrigerant for refrigerators, and various mineral oils and synthetic oils satisfying the above-mentioned required characteristics have been used as lubricating oils. However, since CFC12 may cause environmental pollution such as depletion of the ozone layer, its regulation has recently been tightened worldwide. Therefore, Freon 134a is used as a new refrigerant.
The hydrogen-containing chlorofluorocarbon compounds represented by the above have come to the attention. This hydrogen-containing Freon compound, especially Freon 13
4a is preferable as a refrigerant for a refrigerator because it has a low risk of destroying the ozone layer and can be replaced with Freon 12 with almost no change in the structure of a conventional refrigerator.

As a refrigerant for the refrigerator, instead of Freon 12, the Freon
When a hydrogen-containing CFC compound such as 134a is adopted, as a lubricating oil, it is naturally excellent in compatibility with the CFC-containing CFC compound such as C Freon-134a and excellent in lubricating performance capable of satisfying the above-mentioned required performance. Is required. However, the lubricating oil that has been used together with the conventional Freon 12 does not have good compatibility with hydrogen-containing Freon compounds such as Freon 134a, and thus new lubricating oils suitable for these compounds are required. In this case, especially in automobile air conditioners,
In substituting twelve, it is desired that the structure of the device be changed little, and because of the lubricating oil, it is not desirable to significantly change the structure of the source device. Therefore,
Lubricating oils having extremely good compatibility with hydrogen-containing freon compounds such as freon 134a are required.

As a lubricating oil compatible with Freon 134a, for example, Urcon LB-165 and Urcon LB-525 (both manufactured by Union Carbide Co.,
It is reported that these lubricating oils are compatible with Freon 134a in a total composition ratio at a low temperature of at least -50 ° C [Research Disclosure (Research Disclosure Disclosure) No. 17463 (1978
October 2010)]. A high-viscosity refrigerator oil composition containing polyoxypropylene glycol monobutyl ether as a base oil is also known (Japanese Patent Publication No. 57-42119).

However, these lubricating oils are polyalkylene glycol derivatives in which one end of polypropylene glycol has a hydroxyl group and the other end has an n-butyl ether bond, and has relatively good compatibility with Freon 134a at low temperatures. However, it is also known that the compatibility is not sufficient on the high temperature side, and for example, the urcon LB-525 undergoes phase separation with Freon 134a at room temperature (US Pat. No. 4,755,316).

On the other hand, polyglycol having at least two hydroxyl groups in one molecule has been proposed as one having good compatibility with Freon 134a (US Pat. No. 4,755,316). However, this polyglycol does not always have sufficient compatibility, and since it has a large number of hydroxyl groups in one molecule, it has the drawback of inevitably increasing hygroscopicity and decreasing viscosity index. The increase in hygroscopicity causes an increase in the amount of dissolved water in the mixture of the refrigerant and the lubricating oil, and as a result, the expansion valve may be blocked by ice. Further, a decrease in the viscosity index causes an increase in viscosity in a low temperature evaporator, which may reduce the heat exchange efficiency.

It is known that polyglycol exhibits temperature dependence that, when a mixture with a chlorofluorocarbon compound is heated from a low temperature to a high temperature, the mixture that has generally undergone phase separation once becomes compatible and undergoes phase separation.

Thus, the compatibility with Freon 134a is sufficiently good,
At present, a refrigerating machine lubricating oil having excellent lubricating performance has not yet been found, and its development has been strongly desired.

In addition, the operating conditions of refrigerators have become even more severe due to the adoption of inverters and the increase in compressor speed. For refrigerator oils, stability and lubrication at even higher temperatures are required. Sex is required. As described above, there is an increasing need for a refrigerating machine lubricating oil excellent in high-temperature solubility in a fluorine-based refrigerant, particularly a refractory refrigerant such as Freon-134a.

The present invention, in response to such a demand, particularly a hydrogen-containing CFC compound (fluoroalkane) such as CFC12 or CFC134a, which can be a substitute for other CFCs that are difficult to separate, which is a refrigerant that is a problem in environmental pollution. It has been made with the object of providing a lubricating oil for a refrigerator, which has good compatibility over the entire operating temperature range and is excellent in lubricating performance.

[Means for solving the problem]

The present inventors have conducted extensive studies to develop a refrigerating machine oil having both excellent compatibility with fluorinated alkanes such as Freon 134a and lubrication performance, and as a result, the main component is a polyether compound having a specific structure. The present invention has been found to be suitable for the above purpose, and the present invention has been completed based on this finding.

That is, the present invention has the general formula [In the formula, R ¹ and R ² each represent an alkyl group having 1 to 3 carbon atoms, and R ³ , R ⁴ and R ⁵ each represent hydrogen or an alkyl group having 1 to 3 carbon atoms. However, at least one of R ³ , R ⁴ and R ⁵ is an alkyl group having 1 to 3 carbon atoms. A
Is a copolymer chain of ethylene oxide and propylene oxide, and is composed of m ethylene oxide units and n propylene oxide units. However, m and n are 0.
It is a number that satisfies 1 ≦ m / n ≦ 10, 5 ≦ m + n ≦ 100. ] A refrigerating machine oil for a fluoroalkane refrigerant, which comprises a polyether compound of an ethylene oxide-propylene oxide copolymer represented by the following as a main component is provided.

The refrigerator oil of the present invention has the general formula (I) or (II) above.
The main component is a polyether compound of an ethylene oxide-propylene oxide copolymer represented by. Here, R ¹ and R ² each represent an alkyl group having 1 to 3 carbon atoms (methyl group, ethyl group, n-propyl group, i-propyl group), and R ³ , R ⁴ and R ⁵ are each hydrogen. Or alkyl group having 1 to 3 carbon atoms (methyl group, ethyl group, n-
Propyl group, i-propyl group) are shown. In particular, it is preferable that both R ¹ and R ² are methyl groups, and R ³ , R ⁴ and R ⁵
At least one of the above is the above alkyl group, but it is preferable that R ³ , R ⁴ and R ⁵ are all the above alkyl group, especially a methyl group. A is a copolymer chain of m ethylene oxide units and n propylene oxide units, and its copolymerization form is various such as block copolymerization, random copolymerization, and alternating copolymerization. Here, m and n satisfy 0.1 ≦ m ≦ 10, preferably 0.1 ≦ m / n ≦ 3, particularly preferably 0.2 ≦ m / n ≦ 2, and 5 ≦ m + n ≦ 100, preferably 5 ≦ m + n ≦ It is a number that satisfies 50. in this way,
The polyether compound of the general formula (I) or (II) used for the refrigerating machine oil of the present invention must always contain ethylene oxide units and propylene oxide units in a certain ratio. Here, when m / n is less than 0.1, there is a problem that the viscosity index is lowered and compatibility is lowered, and when m / n is more than 10, wax is formed and compatibility is lowered. Furthermore, if m + n is less than 5, there is a problem that the viscosity is too small and the lubricity decreases.
If it exceeds, there is a disadvantage that compatibility and heat exchange efficiency decrease due to high viscosity.

Hereinafter, the ethylene oxide unit is expressed as EO and the propylene oxide unit is expressed as PO, and in order to simplify A, − (EO)
_Although it is expressed as _m − (PO) _n −, this is not limited to block copolymerization, but widely includes random copolymerization, alternating copolymerization, and the like.

By way of specific examples of the polyether compound of general formula (I) or (II) used in the present _{invention, H 3 C-O- (EO} ) 20 - (PO) 20 -CH 3, and so on. Here, the number of repeating units of EO and PO is merely an example, and may actually vary within a range satisfying the above-mentioned conditions.

As the refrigerating machine oil of the present invention, the polyether compound represented by the general formula (I) or (II) may be used alone or in combination of two or more kinds.

The refrigerating machine oil of the present invention contains the above-mentioned polyether compound as a main component, but other various ignition agents used in conventional lubricating oils, such as load bearing additives, chlorine scavengers,
Antioxidants, metal deactivators, defoamers, detergent dispersants, viscosity index improvers, oiliness agents, antiwear additives, extreme pressure agents, rust inhibitors, corrosion inhibitors, pour point depressants, etc. Further, mineral oil or synthetic oil used as a lubricating base oil can be added as desired.

Examples of the load-bearing additive include organic sulfur compounds such as monosulfides, polysulfides, sulfoxides, sulfones, thiosulfinates, sulfurized fats and oils, thiocarbonates, thiophenes, thiazoles, and methanesulfonic acid esters. Type, phosphoric acid monoesters,
Phosphate esters such as phosphoric acid diesters, phosphoric acid triesters (tricresyl phosphate), phosphorous acid monoesters, phosphorous acid diesters, phosphorous acid esters such as phosphorous acid triesters -Based compounds, thiophosphate-based compounds such as thiophosphoric acid triesters, higher fatty acids, hydroxyaryl fatty acids, carboxylic acid-containing polyhydric alcohol esters, fatty acid-based compounds such as metal soaps, polyhydric alcohol esters, Fatty acid ester-based ones such as acrylic acid esters, organic chlorine-based ones such as chlorinated hydrocarbons and chlorinated carboxylic acid derivatives, fluorinated fatty acid carboxylic acids, fluorinated ethylene resins, fluorinated alkyl polysiloxanes, fluorinated Organic fluorine type such as graphite, alcohol type such as higher alcohol, Metals such as phthalates (lead naphthenate), fatty acid salts (lead fatty acid), thiophosphates (zinc dialkyldithiophosphate), thiocarbamates, organomolybdenum compounds, organotin compounds, organogermanium compounds, borate esters, etc. There are compounds.

Examples of chlorine scavengers include glycidyl ether group-containing compounds, epoxidized fatty acid monoesters, epoxidized oils and fats, and epoxycycloalkyl group-containing compounds.
As antioxidants, phenols (2,6-ditertiarybutyl-p-cresol), aromatic amines (α-
Naphthylamine) etc. Examples of the metal deactivator include benzotriazole derivatives. As antifoaming agent, diricone oil (dimethyl polysiloxane),
Examples include polymethacrylates. Examples of the detergent dispersant include sulfonates, phenates, and succinimides. Examples of the viscosity index improver include polymethacrylate, polyisobutylene, ethylene-propylene copolymer, and styrene-diene hydrogenated copolymer.

〔Example〕

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 3 and Comparative Examples 1 to 4 Using various polyether compounds as sample oils, the critical dissolution temperature was measured by the following test method.

That is, sample oil and refrigerant (CFC134a) were enclosed in a glass pressure vessel with an internal volume of about 10 ml at a ratio (weight) of 1: 9,
Gradually raise the temperature from the state of uniform dissolution,
The temperature at which the sample oil and the refrigerant started to separate was measured and set as the critical solution temperature. The results are shown in Table 1.

As is clear from Table 1, when the sample oils having similar kinematic viscosities are compared, the sample oils of Examples have higher critical dissolution temperatures than the sample oils of Comparative Examples (Example 1 and Comparative Examples 1 to 3, etc.). ).

〔The invention's effect〕

INDUSTRIAL APPLICABILITY The refrigerating machine oil of the present invention is excellent in compatibility with a refrigerant and lubrication performance, and is used as a lubricating oil for a compression type refrigerating machine and various refrigerating machines using a fluoroalkane (CFC) refrigerant. Particularly, unlike conventional lubricating oils, hydrogen-containing freon compounds such as freon 134a (hydrogen-containing fluoroalkanes) (specifically, in addition to freon 134a, 1,1,2,2-tetrafluoroethane (freon- 134); 1,1-Dichloro-2,2,2-trifluoroethane (CFC-123); 1-chloro-1,1-difluoroethane (CFC-142b); 1,1-difluoroethane (CFC 152a); chloro Difluoromethane (CFC-2
2) Or trifluoromethane (CFC-23) etc.)
Good compatibility with.

Therefore, the refrigerating machine oil of the present invention is expected to be effectively used as a lubricating oil for refrigerators, coolers (especially car air conditioners), heat pumps and the like that use various freon compounds as refrigerants.

Claims (2)

(57) [Claims] 1. A general formula [In the formula, R ¹ and R ² each represent an alkyl group having 1 to 3 carbon atoms, and R ³ , R ⁴ and R ⁵ each represent hydrogen or an alkyl group having 1 to 3 carbon atoms. Where R ³ , R ⁴ and R ⁵
At least one is an alkyl group having 1 to 3 carbon atoms.
A is a copolymer chain of ethylene oxide and propylene oxide, and is composed of m ethylene oxide units and n propylene oxide units. However, m and n are
It is a number that satisfies 0.1 ≦ m / n ≦ 10,5 ≦ m + n ≦ 100. ] A refrigerating machine oil for a fluoroalkane refrigerant, which comprises a polyether compound of an ethylene oxide-propylene oxide copolymer represented by the following as a main component. 2. The refrigerating machine oil according to claim 1, wherein the fluorinated alkane refrigerant is 1,1,1,2-tetrafluoroethane.