JP2651375B2 - Refrigeration oil for fluorinated alkane refrigerant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 chlorofluorocarbon 134a) which can be a substitute for chlorofluorocarbon compound such as dichlorodifluoromethane (hereinafter referred to as chlorofluorocarbon 12) which is a problem due to environmental pollution. Refrigeration oil for fluorinated alkane refrigerants, which is mainly composed of a polyether compound of an ethylene oxide-propylene oxide copolymer having good compatibility with hydrogen-containing fluorocarbon compounds (fluorinated alkanes) such as It is about.

[0002]

Generally, a refrigerating machine, especially a compression type refrigerating machine, comprises a compressor, a condenser, an expansion valve, and an evaporator. Is circulated. In such a refrigerator, although it depends on the type of the device, generally, the temperature in the compressor is 50 ° C. or more, while the temperature in the cooler is about −40 ° C., so that the refrigerant and the lubricating oil are: Usually this -40
It is necessary to circulate in this system without phase separation in the temperature range from ° 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 varies depending on the type of compressor used and operating conditions, but usually the viscosity of the lubricating oil before mixing with the refrigerant is 2 to 50 cS at 100 ° C.
t In particular, 2 to 25 cSt is preferable. 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 has been used as a refrigerant for a refrigerator.
, And various mineral oils and synthetic oils satisfying the above-mentioned required characteristics have been used as lubricating oils. However, Freon 12 has a possibility of causing environmental pollution such as destruction of the ozone layer, and thus its regulation has recently become stricter worldwide. Therefore, a hydrogen-containing Freon compound represented by Freon 134a has been attracting attention as a new refrigerant. This hydrogen-containing chlorofluorocarbon compound, particularly chlorofluorocarbon 134a, has a low risk of destruction of the ozone layer, and can be replaced with chlorofluorocarbon 12 with almost no change in the structure of the conventional refrigerator. It is preferred. When a hydrogen-containing chlorofluorocarbon compound such as chlorofluorocarbon 134a is used instead of chlorofluorocarbon 12 as a refrigerant for the refrigerator, the lubricating oil naturally has excellent compatibility with the hydrogen-containing fluorocarbon compound such as chlorofluorocarbon 134a, and What has excellent lubrication performance that can satisfy the required performance described above is required. However, conventional CFC 1
Since the lubricating oil used together with No. 2 has poor compatibility with hydrogen-containing chlorofluorocarbon compounds such as chlorofluorocarbon 134a, a new lubricating oil suitable for these compounds is required. In this case, particularly in the case of an air conditioner for an automobile, 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 current device for lubricating oil. Absent. Therefore, a lubricating oil having extremely good compatibility with the hydrogen-containing Freon compound such as Freon 134a is required. Examples of lubricating oils compatible with Freon 134a include Urcon LB-165 and Urcon LB made of polyalkylene glycol.
-525 (All manufactured by Union Carbide, trade name)
And these lubricants are at least-
It has been reported that at a low temperature of 50 ° C., it is compatible with Freon 134a in all composition ratios (“Research Disclosure” No. 17463 (October 1978)). Further, a high-viscosity refrigerator oil composition using polyoxypropylene glycol monobutyl ether as a base oil is also known (JP-B-57-42119).

[0004] However, these lubricating oils are polyalkylene glycol derivatives having one end of polypropylene glycol having a hydroxyl group and the other end having an n-butyl ether bond, and have a relatively good phase with Freon 134a on the low temperature side. Although it has solubility, it is not sufficiently compatible on the high temperature side. For example, it is also known that Urcon LB-525 causes phase separation with Freon 134a at room temperature (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. As described above, lubricating oils for refrigerators having sufficiently good compatibility with Freon 134a and excellent lubricating performance have not been found yet, 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. As described above, there is an increasing need for a lubricating oil for a refrigerator having excellent high-temperature solubility in a fluorine-based refrigerant, particularly, a hardly-soluble refrigerant such as Freon-134a.
The present invention satisfies such a demand, and particularly, a hydrogen-containing chlorofluorocarbon compound (fluorinated alkane) such as chlorofluorocarbon 134a, which can be a substitute for chlorofluorocarbon 12 or other chlorofluorocarbon compounds which are difficult to decompose due to environmental pollution The purpose of the present invention is to provide a refrigerating machine lubricating oil which has good compatibility with the entire temperature range and has excellent lubricating performance.

[0005]

Means for Solving the Problems The present inventors have developed Freon 1
As a result of intensive studies to develop a refrigerating machine oil excellent in both compatibility with fluorinated alkanes such as 34a and lubricating performance, it has been found that the main component is a polyether compound having a specific structure. And found that the present invention was completed based on this finding. That is, the present invention relates to a compound represented by the general formula: R ¹ -O-A-R ² (I) wherein R ¹ and R ² are each hydrogen or carbon atom 1
And R ¹ and R ² are an alkyl group having 1 to 3 carbon atoms, and the other is hydrogen. 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 0.1 ≦
It is a number that satisfies m / n ≦ 10,5 ≦ m + n ≦ 100. ] It is intended to provide a refrigerating machine oil for a fluorinated alkane refrigerant, which comprises a polyether compound of an ethylene oxide-propylene oxide copolymer represented by the following formula:

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The refrigerating machine oil of the present invention contains, as a main component, a polyether compound of an ethylene oxide-propylene oxide copolymer represented by the aforementioned general formula (I). Here, R ¹ and R ² each represent hydrogen or an alkyl group having 1 to 3 carbon atoms (methyl group, ethyl group), and ^one of R ¹ and R ² is an alkyl group having 1 to 3 carbon atoms.
(Excluding the propyl group) and the other is hydrogen. As the alkyl group having 1 to 3 carbon atoms, a methyl group is particularly preferable. 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 are 0.1.
≦ m / n ≦ 10, preferably 0.1 ≦ m / n ≦ 3, particularly preferably 0.2 ≦ m / n ≦ 2 (provided that m / n is 1.5 or more)
) , And 5 ≦ m + n ≦ 100, preferably 5 ≦ m + n ≦ 50. Further, in the present invention, apart from the polyether compound of the ethylene oxide-propylene oxide copolymer represented by the above general formula (I),

[0007]

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[Wherein, R ³ , R ⁴ and R ⁵ each represent hydrogen or an alkyl group having 1 to 3 carbon atoms. Provided that at least one of R ³ , R ⁴ and R ⁵ has 1 carbon atom
To 3 alkyl groups. A has the same meaning as in the above formula (I). Ethylene oxide represented by the formula
A polyether compound of a propylene oxide copolymer can also be used. In the above general formula (II),
Examples of the alkyl group having 1 to 3 carbon atoms represented by R ³ , R ⁴ or R ⁵ include a methyl group, an ethyl group, an n-propyl group, and an i-propyl group. Also, R ³ , R ⁴
And at least one of R ⁵ is an alkyl group having 1 to 3 carbon atoms. In the present invention, it is preferable that R ³ , R ⁴ and R ⁵ are all an alkyl group, particularly preferably a methyl group.

As described above, the polyether compound of the general formula (I) or (II) used in the refrigerating machine oil of the present invention must necessarily contain ethylene oxide units and propylene oxide units at a certain ratio. Where m /
When n is less than 0.1, there is a problem that the viscosity index is reduced and the compatibility is also reduced. When n is more than 10, it becomes waxy and the compatibility is reduced. Further, when m + n is less than 5, there is a problem that the viscosity is too small and lubricity is reduced, and when it is more than 100, there is a disadvantage that compatibility and heat exchange efficiency are reduced due to high viscosity. Hereinafter, ethylene oxide units are expressed as EO, propylene oxide units are expressed as PO, and A is expressed as-(EO) _m- (PO) _n- for simplicity, but this is limited to block copolymerization. Instead, the present invention widely covers random copolymerization, alternating copolymerization, and the like. Specific examples of the polyether compound of the general formula (I) or (II) used in the present invention include:

[0010]

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And the like. Here, EO and PO
Is merely an example, and may actually be various as long as the above-mentioned condition is satisfied. As the refrigerating machine oil of the present invention, the polyether compounds of the above general formulas (I) and (II) 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, for example, load-bearing additives, chlorine scavengers, antioxidants, and metals Activator, defoamer, detergent / dispersant, viscosity index improver, oil agent,
Antiwear additives, extreme pressure agents, rust inhibitors, corrosion inhibitors, pour point depressants, etc., and mineral oil or synthetic oil used as a lubricating base oil can be added as desired.

Examples of the load-bearing additives include monosulfides, polysulfides, sulfoxides, sulfones, thiosulfinates, sulfurized oils, thiocarbonates, thiophenes, thiazoles, methanesulfonic acid esters and the like. Organic sulfur compounds, phosphoric acid esters such as phosphoric acid monoesters, phosphoric acid diesters, phosphoric acid triesters (tricresyl phosphate), phosphorous acid monoesters, phosphorous acid diesters , Phosphite esters such as phosphite triesters, thiophosphate esters such as thiophosphate triesters, higher fatty acids, hydroxyaryl fatty acids, carboxylic acid-containing polyhydric alcohol esters, metal soaps Fatty acid type, polyhydric alcohol esters, acrylic acid Fatty acid ester-based compounds such as ters, organic chlorine-based compounds such as chlorinated hydrocarbons and chlorinated carboxylic acid derivatives, fluorinated aliphatic carboxylic acids, fluorinated ethylene resins, fluorinated alkylpolysiloxanes, fluorinated Organic fluorine compounds such as graphite, alcohol compounds such as higher alcohols, naphthenates (lead naphthenate), fatty acid salts (fatty acid lead), thiophosphates (zinc dialkyldithiophosphate), thiocarbamates, organic There are metal compounds such as molybdenum compounds, organic tin compounds, organic germanium compounds, and borate esters.

The chlorine scavenger includes glycidyl ether group-containing compounds, epoxidized fatty acid monoesters, epoxidized oils and fats, and epoxycycloalkyl group-containing compounds. As antioxidants, phenols (2,6-
Di-tert-butyl-p-cresol) and aromatic amines (α-naphthylamine). Examples of the metal deactivator include a benzotriazole derivative. Examples of the antifoaming agent include dicorn oil (dimethylpolysiloxane) and polymethacrylates. Detergents include 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.

[0014]

EXAMPLES 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 and 2 and Comparative Examples 1 to 3 Using various polyether compounds as sample oils, critical dissolution temperatures were measured by the following test methods. That is, a sample oil and a refrigerant (Freon 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 the sample oil and the refrigerant began to separate was measured and defined as the critical melting temperature. The results are shown in Table 1.

[0015]

[Table 1]

As is apparent from Table 1 above, when comparing sample oils having similar kinematic viscosities, the sample oil of the example has a higher critical solution temperature than the sample oil of the comparative example (Example 1 and Comparative Example 3).
Such).

[0017]

The refrigerating machine oil of the present invention has excellent compatibility with a refrigerant and lubricating performance, and is used as a lubricating oil for various types of refrigerating machines using a fluorinated alkane (fluorocarbon) refrigerant, including a compression type refrigerating machine. . In particular, unlike conventional lubricating oils, hydrogen-containing freon compounds such as freon 134a (hydrogen-containing fluorinated alkanes) (specifically, other than freon 134a,
1,1,2,2-tetrafluoroethane (CFC-13
4); 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 (especially car air conditioners), heat pumps and the like using various fluorocarbon compounds as refrigerants.

Claims (2)

(57) [Claims] ^1. A compound represented by the general formula R ¹ —O—A—R ^{2 wherein} R ¹ and R ² are each hydrogen or
Represents an alkyl group having 1 to 3 carbon atoms (excluding a propyl group) , and ^one of R ¹ and R ² is an alkyl group having 1 to 3 carbon atoms (a propyl group).
And the other is hydrogen. A is a copolymer chain of ethylene oxide and propylene oxide, and m
Of ethylene oxide units and n propylene oxide units. However, m and n are 0.1 ≦ m / n ≦ 10
(Except those with m / n of 1.5 or more) , 5 ≦ m + n ≦ 10
It is a number that satisfies 0. A kinematic viscosity at 100 ° C. of from 2 to 50 cS , comprising a polyether compound of an ethylene oxide-propylene oxide copolymer represented by the following formula:
t (excluding those below 4.91 cSt)
Refrigeration oil for fluorinated alkane refrigerant. 2. The method according to claim 1, wherein the fluorinated alkane refrigerant is 1,1,1,2.
The refrigerating machine oil according to claim 1, which is -tetrafluoroethane.