JP2774307B2 - 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 having good compatibility with a hydrogen-containing chlorofluorocarbon compound (fluorinated alkane) such as fluorinated alkane refrigerant.

[Problems to be solved by conventional technology and invention]

Generally, a refrigerator, and particularly a compression type refrigerator, comprises a compressor, a condenser, an expansion valve, and an evaporator, and has a structure in which a liquid mixture of a refrigerant and a lubricating oil circulates in this 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
2 to 25 cSt is preferred to obtain 2 to 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. In addition, as other performance,
It is required to have anti-seizure performance for preventing seizure of the movable part and low hygroscopicity for preventing blockage of the expansion valve due to icing in the expansion valve.

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 refrigerator, 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 an air conditioner for an automobile, it is demanded 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 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 (the above-mentioned US patent specification). 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.

Furthermore, these polyglycols have insufficient seizure resistance, and therefore, extreme pressure agents and antiwear agents are also blended. However, when these are blended, although the effect of improving abrasion resistance can be obtained, there is a problem that the high-temperature solubility in a hydrogen-containing chlorofluorocarbon compound (fluorinated ethane-based refrigerant) such as chlorofluorocarbon 134a is insufficient, and such improvement is required. Was desired.

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, lubricating oils for refrigerators that have sufficiently good compatibility with hydrogen-containing Freon compounds (fluorinated ethane-based refrigerants) such as Freon 134a and have excellent lubricating performance have not yet been found. At present, its 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 have excellent high-temperature solubility in fluorine-based refrigerants, especially hardly soluble refrigerants such as Freon 134a or hydrogen-containing Freon compounds (fluorinated ethane-based refrigerants).

The present invention responds to such a demand, and particularly includes a fluorocarbon compound such as a hydrogen-containing fluorocarbon compound such as fluorocarbon 134a, which can be a substitute for fluorocarbon 12 or other fluorocarbon compounds which are difficult to decompose, which is a problem due to environmental pollution. The object of the present invention is to provide a lubricating oil for refrigerators which has good compatibility with alkane fluoride over the entire operating temperature range and also has excellent lubricating performance.

[Means for solving the problem]

The present inventors have conducted intensive studies to develop a refrigerating machine oil having excellent compatibility with fluorinated alkanes such as Freon 134a, lubricating performance, and seizure resistance. As a result, a polyether compound having a specific structure has been obtained. As a main component, and a mixture thereof with a phosphate ester was found to be suitable for the above purpose.

 The present invention has been completed based on such findings.

That is, the present invention relates to a compound represented by the general formula R ¹ -O-A-R ^2. Wherein R ¹ and R ² each represent hydrogen or an alkyl group having 1 or 2 carbon atoms, at least one of R ¹ and R ² is an alkyl group having 1 or 2 carbon atoms, and R ^{3 to} R ⁵ are Each represents hydrogen or an alkyl group having 1 to 3 carbon atoms, and at least one of R ^{3 to} R ⁵ is an alkyl group having 1 to 3 carbon atoms. A represents an ethylene oxide unit and a propylene oxide unit, and represents a copolymer chain composed of a total of 3 to 100 units, and A ^{1 to} A ³ are each one or more alkylene oxides having 2 to 4 carbon atoms. It shows a polymer chain composed of 3 to 100 units. ] To a base oil mainly composed of a polyether compound represented by the general formula [In the formula, R ⁶ represents hydrogen or an alkyl group having 1 to 3 carbon atoms, and k represents an integer of 1 or 2. When k is 2, each
R ⁶ may be the same or different. However, (R ⁶ ) _k has a total of 3 or less carbon atoms. ] It is intended to provide a refrigerating machine oil for a fluorinated alkane refrigerant, characterized by containing a phosphate ester represented by the following formula:

The refrigerating machine oil of the present invention contains the polyether compound represented by the general formula [I] and / or [II] as a main component. Here, R ¹ , R ² , R ³ , R ⁴ and R ⁵ each represent hydrogen or an alkyl group having 1 to 3 carbon atoms (methyl group, ethyl group, n-propyl group, iso-propyl group), In particular, those in which all of R ^{1 to} R ⁵ are alkyl groups, particularly all of which are methyl groups are preferred. A represents an ethylene oxide unit and a propylene oxide unit, and represents a copolymer chain composed of a total of 3 to 100 units thereof, and A ^{1 to} A ³ represent ^one or more alkylene oxide units having 2 to 4 carbon atoms. It is a (co) polymer chain consisting of 3 to 100, preferably 3 to 50. Here, the numbers from 3 to 100 representing the number of units represent the average value of the number of polymerization of alkylene oxide units (ethylene oxide units, propylene oxide units, butylene oxide units), and represent real numbers including integers.

That formula - (R ⁷ O) - wherein, R ⁷ represents an alkylene group having 2 to 4 carbon atoms] and alkylene oxide units a side represented by the general formula :-( R ⁷ 'O) - [ In the formula, R ⁷ ′ 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 the formula: 0-100, and a + b = 3-100
Is a number that satisfies When either a or b is 0, the homopolymerized chain of the other alkylene oxide unit is formed.

Here, when a + b exceeds 100, there is a disadvantage that the compatibility is reduced and separation occurs.

Specific examples of the polyether compound of the general formula (I) or (II) used in the present invention include: (However, the copolymer represented by the block copolymer is not limited to the block copolymer but includes a random copolymer or an alternating copolymer.).

As the refrigerating machine oil of the present invention, the above general formulas [I] and [I
The polyether compounds of [I] may be used alone, or two or more of them may be used in combination.

In the present invention, a phosphate ester represented by the above general formula [III] is blended with a base oil containing a polyether compound as a main component as described above. Here, R ⁶ represents hydrogen or an alkyl group having 1 to 3 carbon atoms as in the above R ^{1 to} R ^5, and k represents an integer of 1 or 2. When two R ⁶ are bonded, different alkyl groups may be bonded, but the total number of carbon atoms of both alkyl groups needs to be 3 or less.

Specific examples of the phosphate represented by the general formula [III] include tricresyl phosphate (tricresyl phosphate (TCP)), triphenyl phosphate, and tri-isopropylphenyl phosphate. It is particularly preferable to use tricresyl phosphate.

In the present invention, the amount of the phosphoric acid ester is not particularly limited, but is usually appropriately selected within the range of 0.1 to 5% by weight, preferably 0.2 to 3% by weight of the whole refrigerating machine oil to be prepared.

The present invention, by combining the polyether compound having the above-described structure and the above-mentioned phosphate ester, sufficiently develops the effect of the phosphate ester as an anti-wear agent, improves seizure resistance, and reduces appearance deterioration and It is intended to reduce adverse effects such as lowering of high-temperature critical melting temperature and improve lubricating performance as refrigerating machine oil.

The refrigerating machine oil of the present invention usually contains the above-mentioned polyether compound as a main component, and is mixed with a phosphoric ester of the general formula [III]. In addition, various additives used in conventional lubricating oils are used. Such as load-bearing additives, chlorine scavengers, antioxidants, metal deactivators, defoamers, detergents / dispersants, viscosity index improvers, oil agents, anti-wear additives, extreme pressure agents,
Rust inhibitors, corrosion inhibitors, pour point depressants and the like can be added.

Further, as a base oil, a mineral oil or a synthetic oil generally used as a lubricating oil base oil can be added as required together with the above polyether compound.

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,
Phosphoric acid esters such as phosphoric diesters, phosphoric triesters (excluding those having the structure of the general formula [III]), phosphite monoesters, phosphite diesters, phosphorus phosphites Phosphites such as acid triesters, thiophosphates such as thiophosphate triesters, higher fatty acids, hydroxyaryl fatty acids, carboxylic acid-containing polyhydric alcohol esters,
Fatty acid-based compounds such as metal soaps, fatty acid ester-based compounds such as polyhydric alcohol esters and acrylic acid esters, organic chlorine-based compounds such as chlorinated hydrocarbons and chlorinated carboxylic acid derivatives, fluorinated fats Aromatic carboxylic acids, fluorinated ethylene resins, fluorinated alkylpolysiloxanes, organic fluorinated compounds such as fluorinated graphite, alcoholic compounds such as higher alcohols, naphthenates (lead naphthenate), fatty acid salts (lead fatty acid) ), Thiophosphates (zinc dialkyldithiophosphate), thiocarbamates, organic molybdenum compounds, organic tin compounds,
Metal compounds such as organic germanium compounds and borates are available. 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 the antioxidant include 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 silicone oil (dimethylpolysiloxane) and polymethacrylates. Detergents include sulfonates, phenates, succinimides and the like. As viscosity index improvers,
Examples 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 and 2 and Comparative Examples 1 to 15 Various kinds of polyether compounds and mixtures of these with various additives were used as sample oils and subjected to the following high-temperature critical melting temperature, stability, abrasion resistance, The seizure was measured.
The kinematic viscosity of each sample oil was adjusted to about 10 cSt (100 ° C.).

(1) Critical melting temperature at high temperature Sample oil and refrigerant (Freon 134a) are sealed in a glass pressure-resistant container with 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. Then, the temperature at which the sample oil and the refrigerant began to separate was measured and defined as the high critical melting temperature.

(2) Stability Evaluation was performed by a shield tube test.

A 2: 1 mixture of sample oil and refrigerant (Freon 134a)
Enclosed in a glass tube with copper and aluminum catalysts, 17
After heating at 5 ° C. for 720 hours, the appearance of the oil and the catalyst was observed, and the total acid value was measured.

(3) Abrasion resistance Evaluation was performed by a Falex wear test.

The amount of abrasion was measured at a blowing rate of Freon 134a of 10 / hour, a load of 300 pounds, and a time of 1 hour.

(4) Seizure resistance It was evaluated by a Falex seizure test.

In accordance with ASTM D 3233, the blowing amount of Freon 134a was 10
The seizure load (lb) was measured as / hour. The results are shown in Table 1.

As is clear from Table 1 above, the sample oil of the example has a higher high-temperature critical melting temperature than the sample oil of the comparative example, and is excellent in seizure resistance.

〔The invention's effect〕

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

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.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ identification code FI C10N 30:00 30:06 40:30 (58) Investigated field (Int.Cl. ⁶ , DB name) C10M 105/18 C10M 107 / 34 C10M 137/04 C10N 40:30

Claims (3)

(57) [Claims] ^1. A compound of the general formula R ¹ —O—A—R ² ... [I] and / or Wherein R ¹ and R ² each represent hydrogen or an alkyl group having 1 or 2 carbon atoms, at least one of R ¹ and R ² is an alkyl group having 1 or 2 carbon atoms, and R ^{3 to} R ⁵ are Each represents hydrogen or an alkyl group having 1 to 3 carbon atoms, and at least one of R ^{3 to} R ⁵ is an alkyl group having 1 to 3 carbon atoms. A represents an ethylene oxide unit and a propylene oxide unit, and represents a copolymer chain composed of a total of 3 to 100 units, and A ^{1 to} A ³ are each one or more alkylene oxides having 2 to 4 carbon atoms. It shows a polymer chain composed of 3 to 100 units. ] To a base oil mainly composed of a polyether compound represented by the general formula [In the formula, R ⁶ represents hydrogen or an alkyl group having 1 to 3 carbon atoms, and k represents an integer of 1 or 2. When k is 2, each
R ⁶ may be the same or different. However, (R ⁶ ) _k has a total of 3 or less carbon atoms. ] A refrigerating machine oil for a fluorinated alkane refrigerant, which comprises a phosphate ester represented by the following formula: 2. The refrigerating machine oil according to claim 1, wherein the phosphate ester is tricresyl phosphate. 3. The refrigerating machine oil according to claim 1, wherein the fluorinated alkane refrigerant is 1,1,1,2-tetrafluoroethane.