JP2859253B2 - 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. 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.

[0002]

2. Description of the Related Art Generally, a refrigerator, especially a compression type refrigerator,
It is composed of 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 this closed system. 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, it is necessary to circulate through 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, when phase separation of refrigerant and lubricating oil occurs in the compressor part,
The moving parts will have poor lubrication, causing seizures, etc.
Significantly shortening the life of the device, while phase separation occurs in the evaporator, reduces the efficiency of heat exchange due to the presence of high viscosity lubricating oil. Also, refrigerator oil (lubricating oil for refrigerator)
Since lubrication is used for lubricating the movable parts of the refrigerator, lubrication 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,
Usually, the viscosity of the lubricating oil before mixing with the refrigerant is 2-50 cSt at 100 ° C, especially 2-25 cS
t is preferred. 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, it is preferable that the viscosity index is high, and usually a viscosity index of 40 or more is required. Further, as other performance, anti-seizure performance for preventing seizure of the movable portion, low hygroscopicity for preventing clogging of the expansion valve due to icing, and the like are 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 the refrigerant of 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.

[0004] As lubricating oils having compatibility with Freon 134a, for example, Urcon LB-165 and Urcon LB-525 (both manufactured by Union Carbide, trade names) made of polyalkylene glycol are known. It has been reported that lubricating oils are compatible with Freon 134a in all composition ratios at least at a low temperature of −50 ° C. [Research Disclosure (Research)
No. 17463 (October 1978)
Moon)〕. Further, 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 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 on the low temperature side. However, the compatibility is not sufficient on the high temperature side. For example, the Urcon LB-525 has a
It is also known to cause phase separation with 34a (U.S. 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 the wear resistance is obtained, there is a problem that the high-temperature solubility in a hydrogen-containing chlorofluorocarbon compound (fluorinated ethane-based refrigerant) such as chlorofluorocarbon 134a becomes 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.

[0006]

As described above, Freon 1
At present, lubricating oils for refrigerators having sufficiently good compatibility with hydrogen-containing Freon compounds (fluorinated ethane-based refrigerants) such as 34a and excellent lubricating performance have not yet been found. Development was strongly desired. Furthermore, the operating conditions of the refrigerator have become more and more severe due to inverters, increase in the number of rotations of the compressor, etc.
Refrigerator lubricating oils are required to have even higher temperature stability and lubricity. As described above, the necessity of a lubricating oil for a refrigerator excellent in high-temperature solubility in a fluorine-based refrigerant, particularly a sparingly soluble refrigerant such as Freon 134a or a hydrogen-containing fluorocarbon compound (fluorinated ethane-based refrigerant) is increasing. The present invention satisfies such a demand, and particularly includes fluorine-containing fluorocarbon compounds such as fluorocarbon 134a and the like, which can substitute for fluorocarbon 12 or other fluorocarbon compounds which are difficult to decompose, which are particularly problematic for 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.

[0007]

Means for Solving the Problems The present inventor has developed a Freon 13
As a result of intensive studies to develop a refrigerating machine oil having excellent compatibility with fluorinated alkanes such as 4a, lubricating performance and anti-seizure properties, the main component was a polyether compound having a specific structure. It has been found that a composition in which a phosphate ester is blended can be suitable for the above purpose. The present invention has been completed based on such findings. That is, the present invention relates to the general formula R ¹ -OA ¹ -R ² ... [I] and / or the general formula

[0008]

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[Wherein R ^{1 to} R ⁵ each have 1 to 1 carbon atoms.
Indicates 3 alkyl group, A ¹ to A ³ are each one or two or more alkylene oxide units having 2 to 4 carbon atoms 3
The figure shows a polymer chain composed of ~ 100. ] To a base oil comprising a polyether compound represented by the general formula

[0010]

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[Wherein R ⁶ is hydrogen or a group having 1 to 3 carbon atoms.
And k represents an integer of 1 or 2. k
When R is 2, each R ⁶ may be the same or different. However, (R ⁶ ) _k has a total carbon number of 3 or less. ] Refrigeration oil for a fluorinated alkane refrigerant, characterized by comprising a phosphate ester represented by the formula:

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The refrigerating machine oil of the present invention contains a polyether compound represented by the aforementioned general formula [I] and / or [II] as a main component. Where R ¹ , R ² , R
^3, R ⁴ and R ⁵ are each an alkyl group having 1 to 3 carbon atoms (methyl group, ethyl group, n- propyl group, iso - propyl) show, all particularly R ¹ to R ⁵ is a methyl group Some are preferred. A ^{1 to} A ^{3 each} have 2 to 2 carbon atoms.
One or two or more alkylene oxide units 3-1
It is a (co) polymer chain consisting of 00, preferably 3 to 50. Here, the numbers of 3 to 100 representing the number of units 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.

[0013] That formula - (R ⁷ O) - wherein, R ⁷ represents an alkylene group having 2 to 4 carbon atoms] and alkylene oxide units a number represented by the general formula :-( R ⁷ 'O A) a block copolymer chain, a random copolymer chain or an alternating copolymer chain containing b alkylene oxide units represented by the formula: wherein R ⁷ ′ represents an alkylene group having 2 to 4 carbon atoms; And b are each 0 to 100, and a + b = 3 to 1
It is a number that satisfies 00. 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 lowered and separation occurs. Specific examples of the polyether compound of the general formula (I) or (II) used in the present invention include:

[0014]

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(However, the copolymer represented by the block copolymer is not limited to the block copolymer but includes a random copolymer or an alternating copolymer.).
The refrigerating machine oil of the present invention includes the above general formulas [I] and [II]
May be used alone, respectively.
Also, two or more of the two may be used in combination. In the present invention, the phosphate represented by the general formula [III] is blended with the base oil containing the above-described polyether compound as a main component. Here, R ⁶ represents hydrogen or an alkyl group having 1 to 3 carbon atoms as in 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 above-mentioned phosphate ester is not particularly limited, but is usually the total amount of the refrigerating machine oil to be prepared.
It is appropriately selected within the range of 0.1 to 5% by weight, preferably 0.2 to 3% by weight. 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 a phosphoric ester of the general formula [III], and also contains various additives used in conventional lubricating oils. Such as load-bearing additives, chlorine scavengers, antioxidants, metal deactivators, defoamers, cleaning dispersants, viscosity index improvers,
Oil agent, anti-wear additive, extreme pressure agent, rust inhibitor, corrosion inhibitor,
A pour point depressant and the like can be blended. 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 additives include monosulfides, polysulfides, sulfoxides, sulfones, thiosulfinates, sulfurized fats and oils, thiocarbonates, thiophenes, thiazoles, methanesulfonic acid esters and the like. Phosphoric acid esters such as organic sulfur compounds, phosphoric acid monoesters, phosphoric diesters, and phosphoric acid triesters (excluding those having the structure of general formula [III]); Phosphites such as acid monoesters, phosphite diesters, and phosphite triesters; thiophosphates such as thiophosphate triesters; higher fatty acids; hydroxyaryl fatty acids; Carboxylic acid polyhydric alcohol esters, fatty acid compounds such as metal soaps, polyhydric alcohol esters, Fatty acid esters such as acrylates; organic chlorines such as chlorinated hydrocarbons and chlorinated carboxylic acid derivatives; fluorinated aliphatic carboxylic acids; fluorinated ethylene resins; fluorinated alkylpolysiloxanes; Organic fluorine compounds such as fluorinated graphite, alcohol compounds such as higher alcohols, naphthenates (lead naphthenate), fatty acid salts (lead fatty acid), thiophosphates (zinc dialkyldithiophosphate), thiocarbamates , Organic molybdenum compounds,
Metal compounds such as organic tin compounds, organic germanium compounds, and borate esters 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. 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 silicone 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.

[0019]

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 to 3 and Comparative Examples 1 to 15 A mixture of various polyether compounds and various additives was used as a sample oil 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) High temperature critical melting temperature 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,
From the homogeneously dissolved state, gradually raise the temperature,
The temperature at which the sample oil and the refrigerant began to separate was measured and defined as the high temperature critical melting temperature. (2) Stability Evaluation was performed by a shield tube test. A 2: 1 mixture of sample oil and refrigerant (CFC 134a) was sealed in a glass tube with iron, copper, and aluminum catalysts, heated at 175 ° C. for 720 hours, and the appearance of the oil and catalyst was observed to determine the total acid value. Was measured. (3) Abrasion resistance Evaluation was performed by a Falex wear test. Freon 13
4a blowing rate of 10 L / hour, load of 300 pounds,
The amount of wear was measured with the time being one hour. (4) Seizure resistance It was evaluated by a Falex seizure test. ASTM
According to D 3233, the blowing amount of Freon 134a is 1
The seizure load (lb) was measured as 0 L / hour. The results are shown in Table 1.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

[Table 6] 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.

[0026]

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.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ identification code FI C10N 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 general formula R ¹ -OA ¹ -R ² ... [I] and / or a general formula [Wherein, R ^{1 to} R ⁵ each represent an alkyl group having 1 to 3 carbon atoms, and A ^{1 to} A ³ each include one or more of 3 to 100 alkylene oxide units having 2 to 4 carbon atoms. 1 shows a polymerized chain. ] To a base oil containing a polyether compound represented by the following 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 carbon number of 3 or less. ] A refrigerating machine oil for a fluorinated alkane refrigerant, characterized by containing a phosphate ester represented by the formula: 2. The refrigerating machine oil according to claim 1, wherein the phosphate ester is tricresyl phosphate. 3. The method of claim 1, wherein the fluorinated alkane refrigerant is 1,1,1,2.
The refrigerating machine oil according to claim 1, which is -tetrafluoroethane.