JP2710980B2 - Refrigeration oil for fluorinated alkane refrigerant - Google Patents

Description

The present invention relates to a refrigerating machine oil for a fluorinated alkane refrigerant. More specifically, 1,1,1,2-tetrafluoroethane (hereinafter referred to as Freon 134a, which can be an alternative to Freon compounds such as dichlorodifluoromethane (hereinafter referred to as Freon 12), which is a refrigerant causing environmental pollution, The present invention relates to a refrigerating machine oil for a fluorinated alkane refrigerant, which is mainly composed of a polyether compound having good compatibility with a hydrogen-containing Freon compound (fluorinated alkane) such as fluorinated alkane.

[Problems to be solved by conventional technology and invention]

In general, a refrigerator, particularly a compression refrigerator, includes a compressor, a condenser, an expansion valve, and an evaporator, and has a structure in which a liquid mixture of a refrigerant and lubricating oil circulates in the closed system. In such a refrigerator, although it depends on the type of the device, in general, the temperature in the compressor is 50 ° C. or higher,
Since the temperature in the cooler is as low as about −40 ° C., the refrigerant and the lubricating oil usually need to circulate 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, the life and efficiency of the apparatus will be significantly adversely affected. For example, if phase separation of refrigerant and lubricating oil occurs in the compressor part, the moving parts will be poorly lubricated, causing seizure etc., significantly shortening the life of the device, while phase separation occurs in the evaporator. In addition, the presence of a lubricating oil having a high viscosity causes a reduction in heat exchange efficiency.

Further, since the refrigerating machine oil (lubricating oil for the refrigerating machine) is used for lubricating the movable parts of the refrigerating machine, the lubricating performance naturally becomes important. In particular, since the temperature inside the compressor becomes high, a viscosity capable of holding an oil film required for lubrication is important. The required viscosity depends on the type of compressor used and operating conditions, but usually the viscosity of lubricating oil before mixing with refrigerant is 10
Preferred is 2-50 cSt at 0 ° C. If the viscosity is lower than this, the oil film becomes thin and lubrication failure easily occurs, and if it is higher, the efficiency of heat exchange decreases. Further, since lubricating oil for refrigerators is circulated in a wide temperature range from high temperature to low temperature, the viscosity index is preferably high, and usually a viscosity index of 40 or more is required. Further, as other performances, low hygroscopicity or the like for preventing blockage of the expansion valve due to icing is required.

Conventionally, Freon 12 is often used as a refrigerant of a refrigerator, and various mineral oils and synthetic oils satisfying the above-mentioned required characteristics have been used as a lubricating oil. However, CFCs 12 have a risk of causing environmental pollution such as destruction of the ozone layer. Therefore, Freon 134a is used as a new refrigerant.
The hydrogen-containing CFC compounds represented by the above have been attracting attention. This hydrogen-containing Freon compound, especially Freon 13
4a is preferable as a refrigerant for a refrigerator, because it has little risk of destruction of the ozone layer and can be replaced with Freon 12 without changing the structure of the conventional refrigerator.

As the refrigerant for the refrigerant machine, use the above CFC instead of CFC12
When a hydrogen-containing Freon compound such as 134a is employed, the lubricating oil naturally has excellent compatibility with the hydrogen-containing Freon compound such as Freon 134a and has excellent lubricating performance capable of satisfying the above-mentioned required performance. Is required. However, lubricating oils that have been used with conventional Freon 12 have poor compatibility with hydrogen-containing Freon compounds such as Freon 134a,
New lubricating oils suitable for these compounds are needed. In this case, particularly in the case of an air conditioner for automobiles, it is desired that the structure of the device is hardly changed when replacing the CFC 12, and it is not desirable to greatly change the structure of the source device for lubricating oil. Absent. Therefore, a lubricating oil having extremely good compatibility with a hydrogen-containing Freon compound such as Freon 134a is required.

Examples of lubricating oils having compatibility with Freon 134a include, for example, Urcon LB-165 and Urcon LB-525 made of polyalkylene glycol (both manufactured by Union Carbide,
It has been reported that these lubricating oils become compatible with Freon 134a in all composition ratios at least at a low temperature of −50 ° C. [Research Disclosure Disclosure] No. 17463 (1978
October)). A high-viscosity refrigerator oil composition using polyoxypropylene glycol monobutyl ether as a base oil is also known (JP-B-57-42119).

However, these lubricating oils are polyalkylene glycol derivatives having a hydroxyl group at one end of polypropylene glycol and an n-butyl ether bond at the other end, and have relatively good compatibility with Freon 134a on the low temperature side. However, at the high temperature side, the compatibility is not enough,
For example, the aforementioned Urcon LB-525 is a fluorocarbon 1 at room temperature.
It is also known to cause phase separation with 34a (US Pat. No. 4,755,316).

On the other hand, a polyglycol having at least two hydroxyl groups in one molecule has been proposed as having good compatibility with Freon 134a (US Pat. No. 4,755,316). However, this polyglycol does not always have sufficient compatibility, and has a disadvantage that the number of hydroxyl groups in one molecule is so large that an increase in hygroscopicity and a decrease in viscosity index cannot be avoided. 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 leads to an increase in viscosity in a low-temperature evaporator, which may lower the heat exchange efficiency.

It is known that when a mixture of a polyglycol and a Freon compound is heated from a low temperature to a high temperature, the mixture, which has been generally phase-separated, once dissolves and exhibits phase dependence.

Thus, the compatibility with Freon 134a is sufficiently good,
At present, lubricating oils for refrigerators having excellent lubrication performance have not yet been found, and their development has been strongly desired.

In addition, the operating conditions of refrigerators have become more and more severe due to the use of inverters and an increase in the number of rotations of compressors. Is required. in this way,
There is an increasing need for lubricating oils for refrigerators that are excellent in high-temperature solubility in fluorinated refrigerants, especially in insoluble refrigerants such as Freon 134a, and have low hygroscopicity.

The present invention satisfies such demands, and in particular, a hydrogen-containing chlorofluorocarbon (fluorinated alkane) such as chlorofluorocarbon 134a, which can substitute for chlorofluorocarbon 12 or other chlorofluorocarbon compounds which are difficult to decompose, which is a problem due to environmental pollution. The purpose of the present invention is to provide a lubricating oil for refrigerators, which has good compatibility with the entire temperature range, has excellent lubricating performance, and has low hygroscopicity.

[Means for solving the problem]

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

That is, the present invention provides a compound represented by the general formula: R ¹ -O-A-R ² (1) wherein R ¹ is an unsaturated hydrocarbon group having 2 to 10 carbon atoms (provided that
A represents a polymer chain (n is a number from 3 to 90) composed of n alkylene oxide units of one or more kinds having 2 to 4 carbon atoms, R ² represents hydrogen, Carbon number 1
20 alkyl groups, alkenyl groups having 2 to 20 carbon atoms, alkynyl groups having 2 to 20 carbon atoms, aryl groups having 6 to 20 carbon atoms, aralkyl groups having 7 to 20 carbon atoms or cycloalkyl groups having 4 to 20 carbon atoms Is shown. ] It is intended to provide a refrigerating machine oil for a fluorinated alkane refrigerant containing a polyether compound represented by the following formula:

The refrigerating machine oil of the present invention contains the polyether compound represented by the general formula (I) as a main component. Here, R ¹ represents an unsaturated hydrocarbon group having 2 to 10 carbon atoms excluding an aromatic unsaturated hydrocarbon, for example, an alkenyl group, an alkynyl group, a cycloalkenyl group and the like. , Isopropenyl, butenyl, ethynyl, propynyl, butynyl and the like.

As described above, R ² represents, in addition to hydrogen, an alkyl group having 1 to 20 carbon atoms (methyl group, ethyl group, propyl group, butyl group, etc.) and an alkenyl group having 2 to 20 carbon atoms (vinyl group, allyl group). , Butenyl group, etc.), alkynyl group having 2 to 20 carbon atoms (ethynyl group, propynyl group, etc.), aryl group having 6 to 20 carbon atoms (phenyl group, tolyl group, xylyl group, nonylphenyl group, dodecylphenyl group, etc.) Aralkyl groups having 7 to 20 carbon atoms (benzyl group, phenethyl group, etc.) or
And 20 cycloalkyl groups (cyclohexyl group, cycloheptyl group, methylcyclohexyl group, nonylcyclohexyl group, etc.). Among them, hydrogen, an alkyl group having 1 to 4 carbon atoms and an alkenyl group having 2 to 4 carbon atoms are preferable.

A is a (co) polymer chain composed of 3 to 90, preferably 3 to 50, one or more alkylene oxide units having 2 to 4 carbon atoms. Here, 3 representing the above number of units
Numerals of up to 90 indicate the average value of the number of polymerization of alkylene oxide units (ethylene oxide units, propylene oxide units, butylene oxide units), and indicate real numbers including integers.

That formula: - (R ³ O) - wherein, R ³ represents an alkylene group having 2 to 4 carbon atoms] and alkylene oxide units a number represented by the general formula :-( R ³ 'O) - [Wherein, R ³ ′ represents an alkylene group having 2 to 4 carbon atoms.] A block copolymer chain, a random copolymer chain or an alternating copolymer chain containing b alkylene oxide units represented by Are numbers satisfying 0 to 90 and a + b = 3 to 90, respectively. When either a or b is 0, the homopolymerized chain of the other alkylene oxide unit is formed.

Here, when a + b exceeds 90, the compatibility is lowered and there is a disadvantage that separation occurs.

By way of specific examples of the polyether compound of general formula (I) used in the present _{invention, CH 2 = CH-CH 2} O (C 3 H 6 O) 4~40 H CH 2 = CH-CH 2 O (C 3 _{H 6 O) 4~40 CH 3 CH} 2 = CH-CH 2 O (C 3 H 6 O) 4~40 CH 2 CH = CH 2 CH 2 = CH-CH 2 O (C 3 H 6 O) 2~ _{20 - (C 2 H 4 O} ) 2~20 CH 3 CH 2 = CHO (C 3 H 6 O) 4~40 H CH 2 = CHO (C 3 H 6 O) 4~40 CH = CH 2 CH 2 = CHO (C ₃ H ₆ O) _{4 to 40} CH ₃ CH≡CO (C ₃ H ₆ O) _{4 to 40} H CH≡CO (C ₃ H ₆ O) _{4 to 40} C≡CH (However, the above block copolymerization Are not limited to block copolymers, but also include random copolymers or alternating copolymers.)

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

The refrigerating machine oil of the present invention contains the above-mentioned polyether compound as a main component. In addition, various additives used in conventional lubricating oils such as a load-bearing additive, a chlorine scavenger,
Antioxidants, metal deactivators, defoamers, detergents / dispersants, viscosity index improvers, oil agents, anti-wear additives, extreme pressure agents, rust inhibitors, corrosion inhibitors, pour point depressants, etc. Further, a mineral oil or a synthetic oil used as a lubricating base oil can be added as required.

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. Series, phosphoric acid monoesters,
Phosphate esters such as phosphoric diesters and phosphoric triesters (tricresyl phosphate), and phosphites such as phosphite monoesters, phosphite diesters, and phosphite triesters Thiophosphates such as thiophosphate triesters, higher fatty acids, hydroxyaryl fatty acids, carboxylic acid-containing polyhydric alcohol esters, fatty acid such as metal soap, polyhydric alcohol esters, Fatty acid esters such as acrylic esters, organic chlorine-based compounds such as chlorinated hydrocarbons and chlorinated carboxylic acid derivatives, fluorinated aliphatic carboxylic acids, fluorinated ethylene resins, fluorinated alkylpolysiloxanes, Organic fluorinated materials such as fluorinated graphite and alcohols such as higher alcohols , Naphthenates (lead naphthenate), fatty acid salts (lead fatty acid), thiophosphates (zinc dialkyldithiophosphate), thiocarbamates, organic molybdenum compounds, organic tin compounds, organic germanium compounds, metals such as borate esters There is a compound type.

Examples of the chlorine scavenger include glycidyl ether group-containing compounds, epoxidized fatty acid monoesters, epoxidized oils and fats, and epoxycycloalkyl group-containing compounds.
Examples of antioxidants include phenols (2,6-di-tert-butyl-p-cresol), aromatic amines (α-
Naphthylamine). As metal deactivators,
And benzotriazole derivatives. Examples of the antifoaming agent include dicorn oil (dimethylpolysiloxane) and polymethacrylates. As a cleaning dispersant,
Sulfonates, phenates, succinimides and the like. Examples of the viscosity index improver include polymethacrylate, polyisobutylene, an ethylene-propylene copolymer, and a 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 1-4 and Comparative Examples 1-3 Critical dissolution temperatures were measured by the following test methods using various polyether compounds as sample oils.

That is, a sample oil and a refrigerant (CFC 134a) are sealed in a glass pressure-resistant container having an internal volume of about 10 ml at a ratio (weight) of 1: 9, and the temperature is gradually increased from a uniformly dissolved state. The temperature at which oil and refrigerant began to separate was measured and defined as the critical melting temperature.

The load-bearing capacity test conforms to ASTM3233 and has an oil temperature of 30.
The test was carried out by measuring the seizure load (pound) after running-in for 5 minutes at 150 ° C. and a load of 150 pounds.

 The results are shown in Table 1.

As is clear from Table 1 above, when comparing the sample oils having similar kinematic viscosities, the sample oil of the example has a higher load carrying capacity and a higher critical melting temperature than the sample oil of the comparative example. It can be seen that Comparative Example 1, Example 2 and Comparative Examples 2 and 3).

〔The invention's effect〕

INDUSTRIAL APPLICABILITY The refrigerating machine oil of the present invention has excellent compatibility with a refrigerant and lubricating performance (load-bearing capacity), and is used as a lubricating oil for various refrigerating machines using a fluorinated alkane (CFC) refrigerant, including a compression type refrigerating machine. . In particular, unlike conventional lubricating oils,
134a and other hydrogen-containing fluorocarbon compounds (hydrogen-containing fluorinated alkanes) (specifically, in addition to the above-mentioned fluorocarbon 134a, 1,1,2,2-
Tetrafluoroethane (Freon-134); 1,1-dichloro-2,2,2-trifluoroethane (Freon-123); 1-chloro-1,1-difluoroethane (Freon-142b); 1,1-difluoroethane (Freon-152a); good compatibility with chlorodifluoromethane (Freon-22) or trifluoromethane (Freon-23).

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

Claims (3)

(57) [Claims] (1) a compound represented by the general formula: R ¹ -O-A-R ^{2 wherein} R ¹ is an unsaturated hydrocarbon group having 2 to 10 carbon atoms (provided that
A represents a polymer chain (n is a number from 3 to 90) composed of n alkylene oxide units of one or more kinds having 2 to 4 carbon atoms, R ² represents hydrogen, Carbon number 1
20 alkyl groups, alkenyl groups having 2 to 20 carbon atoms, alkynyl groups having 2 to 20 carbon atoms, aryl groups having 6 to 20 carbon atoms, aralkyl groups having 7 to 20 carbon atoms or cycloalkyl groups having 4 to 20 carbon atoms Is shown. ] A refrigerating machine oil for a fluorinated alkane refrigerant comprising a polyether compound represented by the following formula: 2. The refrigerating machine oil according to claim 1, wherein R ¹ is an alkenyl group having 2 to 10 carbon atoms. 3. The refrigerating machine oil according to claim 1, wherein the fluorinated alkane refrigerant is 1,1,1,2-tetrafluoroethane.