JPH0649472A - Fluorine-containing aromatic lubricant - Google Patents

Abstract

PURPOSE:To provide a lubricating oil for refrigerating machine oil, etc., containing a specific fluorine-containing aromatic compound, exhibiting excellent compatibility with a fluoroalkane refrigerant over a wide temperature range from a low-temperature to a high temperature and useful as a refrigerant compo sition for refrigeration system. CONSTITUTION:A refrigerant composition for refrigerating machine, etc., free from ozonosphere destruction problem can be produced by compounding a fluoroalkane refrigerant with a lubricant containing a fluorine-containing aromatic compound exhibiting excellent compatibility with a fluoroalkane refrigerant over a wide temperature range from a low-temperature to a high temperature and expressed by the formula R<1>-(OR<2>)n (R<1> is hydrocarbon group having 1-4 aromatic groups and containing fluorine atoms substituting a part or total of H atoms; the ratio of the number of F atoms to that of C atoms in R<2> is >=0.2; <2> is 1-10C hydrocarbon group; n is 1 or 2; when n is 2, the compound may have plural kinds of OR<2> groups).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricant having excellent compatibility with a fluoroalkane-based refrigerant. More specifically, the present invention provides CFC-12 because of environmental protection issues.
(1,1-dichloro-1,1-difluoromethane) and H
Fluorinated alkanes, which are promising substitutes for chlorine atom-containing refrigerants such as CFC-22 (chlorodifluoromethane), preferably hydrofluoroalkanes such as hydrofluoroethane, and more preferably HFC-134a (1,1,
The present invention relates to a refrigerating machine oil composition having excellent compatibility with a fluoroalkane-based refrigerant suitable for a refrigerating system using 1,2-tetrafluoroethane) as a refrigerant.

[0002]

2. Description of the Related Art At present, CFC-12 is mainly used as a refrigerant for refrigerators for car air conditioners and refrigerators, and HCFC-22 is used as a refrigerant for refrigerators for room air conditioners. From the standpoint of CFC-12 and H
It has been desired to develop a refrigerant that can substitute for a chlorine-containing refrigerant such as CFC-22.

Lower fluoroalkanes (for example, fluoroalkanes having 5 or less carbon atoms) are promising as alternative refrigerants, but hydrofluoroalkanes such as hydrofluoroethane are particularly preferable. Among them, HFC-134
Since a has a physical property close to that of CFC-12 as a refrigerant and can be used as a substitute for CFC-12 with a minimum change in the apparatus, it is particularly promising. Also,
HFC-134 (1, which is an isomer of HFC-134a,
1,2,2-Tetrafluoroethane), HFC-152
a (1,1-difluoroethane), HFC-32 (difluoromethane) which is an alternative candidate for HCFC-22, HF
C-125 (pentafluoroethane), HFC-14
Fluorinated alkanes such as 3a (1,1,1-trifluoroethane) are considered to be usable as well.

In a refrigeration system using CFC-12, mineral oil is used as a lubricating oil for a compressor. CFC-12 has a high lipophilicity because it contains chlorine atoms and is compatible with mineral oil in a wide temperature range, so that the refrigerant and the lubricating oil are not separated even in the refrigeration system in which the refrigerant repeatedly evaporates and condenses. However, various fluorinated alkane-based refrigerants represented by HFC-134a do not have sufficient compatibility with mineral oil because they do not contain chlorine atoms, and when mineral oil is used as lubricating oil, for example, the lubricating oil is replaced by the refrigerant in the compressor. As a result, a number of serious problems occur, such as insufficient lubrication and the fact that lubricating oil adheres to the inner wall of the heat exchanger and the heat exchange rate deteriorates.

As a lubricating oil for a refrigerator using a fluorinated alkane such as HFC-134a as a refrigerant, at least 0 ° C. to 50 ° C. or higher, preferably −20 ° C. or lower to 70 ° C. or higher, particularly preferably. Is -40 ° C or less ~ 9
It is necessary to show compatibility with fluorinated alkanes such as HFC-134a in a temperature range of 0 ° C or higher, or in a temperature range wider than that.

Since it has been used together with HFC-134a, it has been used as a lubricating oil having a good compatibility with HFC-134a.
Various polyalkylene glycol compounds and polyester compounds have been proposed. For example, US Pat.
The polyalkylene glycol having two or more hydroxyl groups (particularly polyoxypropylene glycol) disclosed in Japanese Patent No. 755,316 is said to have a wide temperature range in which it exhibits compatibility. However, the temperature range showing the compatibility is not yet sufficient for a lubricating oil, and it is particularly necessary to improve the compatibility in the high temperature region.

Further, polyoxyalkylene glycol has insufficient lubricity under the condition of using a lubricating oil, and further has a high hygroscopic property, so that it causes freezing of water, corrosion of metal, and volume resistivity. Problems such as reduction (problem in closed refrigerators such as refrigerators) are likely to occur, and it cannot be said to be a practically excellent lubricating oil for refrigeration systems. In addition, JP-A-3-12
The polyester compounds disclosed in JP-A-8991, JP-A-3-1799091 and the like are also HFC-134a.
Although it is said that it has excellent compatibility with, it has a high hygroscopicity because it contains an ester group, and it is prone to decomposition such as hydrolysis, causing a problem in durability.

In addition to the above polyalkylene glycol and polyester type oils, fluorine atom-containing oils can be considered as oils that are expected to have affinity with fluorinated alkanes such as HFC-134a. The following patents have been filed as known documents relating to fluorine atom-containing oil.

Japanese Unexamined Patent Publication (Kokai) No. 60-96684 discloses that
When a fluorocarbon lubricating oil such as fluorinated silicone or perfluoropolyether is used in a fluorocarbon working medium used for a pump or the like, the heat resistance of the fluorocarbon working medium is improved. It is disclosed to improve. There is no mention in this patent of the compatibility of the lubricating oil with the fluorinated alkanes used as working medium.

Further, JP-A-1-118598 discloses that a fluorine compound such as perfluoropolyether or fluorinated silicone is used as a lubricant for a fluorocarbon type refrigerant. The compatibility of these fluorine compounds and fluorinated alkanes in the low temperature region below room temperature is not discussed at all. Further, the compatibility of fluorine compounds other than perfluoropolyether and fluorinated silicones with fluorinated alkanes is not described at all.

[0011]

Therefore, the inventor of the present invention
JP-A-60-96684, JP-A-1-11859
The perfluoropolyethers listed in the examples of Japanese Patent No. 8 (Fomblin Y-06, Y-25, manufactured by Nippon Montedison Co., Ltd.
Y-45) and various perfluoropolyethers of the following structures and HFC-134a, HFC-134, and H
When the compatibility with fluorinated alkanes such as FC-152a was investigated, the compatibility may be exhibited in a high temperature region around room temperature or higher. However, in any case except the one having a low molecular weight, 0 ° C or lower The compatibility in the low temperature region is insufficient, and H
FC-134a, HFC-134, and HFC-152
It was found that it is not suitable as a lubricating oil for a refrigerator using a fluorinated alkane such as a as a refrigerant.

[0012]

[Chemical 1]

[0013]

Therefore, the present inventors have
HFC-1 in a wide temperature range from low temperature to high temperature
The inventors have earnestly studied to develop a fluorine atom-containing substance which exhibits good compatibility with fluorinated alkanes such as 34a and which satisfies the required properties as a lubricating oil for a refrigerator, such as lubricating properties, low hygroscopicity and durability.

As a result, the fluorine-containing aromatic compound having the structure represented by the general formula [I] has good compatibility with fluorinated alkanes such as HFC-134a and HFC-134.
They have found that they are suitable as a lubricating oil for a refrigeration system using a refrigerant containing a fluorinated alkane such as a and completed the present invention. Therefore, an object of the present invention is to provide a fluoroalkane such as HFC-134a, which is a promising refrigerant as a substitute for a chlorine atom-containing refrigerant such as CFC-12 or HCFC-22, and a wide temperature range from a low temperature region to a high temperature region. It is an object of the present invention to provide a novel use of a fluorine-containing aromatic compound having good compatibility and having properties suitable as a lubricating oil for a refrigeration system, as a lubricant for a refrigeration system.

Another object of the present invention is to provide a refrigerant composition for a refrigeration system containing the above-mentioned fluorine-containing aromatic compound lubricant and a fluoroalkane-based refrigerant. Another object of the present invention is to provide a fluorinated aromatic compound and a lubricating oil composition containing the fluorinated aromatic compound in order to impart lubricating performance to the fluoroalkane-based refrigerant used in the refrigeration system. To provide a method of using as a lubricating oil.

Since the fluorine atom-containing aromatic compound represented by the formula (I) used in the present invention has a lower fluorine atom content than the perfluoropolyether oil, it is produced from the perfluoropolyether oil. There is an advantage that the cost is low. In addition, the compound of formula (I) exhibits the surprising property that it exhibits good compatibility with various fluoroalkane-based refrigerants, despite its low content of fluorine atoms.

The present invention has been completed based on the discovery of the characteristics of the compound of the general formula (I), which is completely unexpected from the knowledge about the conventional refrigerating machine oil as described above. That is, the present invention includes: a fluoroalkane-based refrigerant, and a formula (I).
And a lubricant containing a fluorine-containing aromatic compound represented by.

R ^1- (OR ² ) _n (I) [wherein n is 1 or 2] R ¹ is an aromatic ring 1 to
It is a hydrocarbon containing four and a part or all of the hydrogen atoms are replaced by fluorine atoms. However,
The ratio of the number of fluorine atoms contained in R ¹ / the number of carbon atoms is 0.2 or more. R ² is a hydrocarbon group having 1 to 10 carbon atoms.

When n is 2, the compound represented by the formula (I) may be composed of plural kinds of OR ² groups. ] As noted above, the present invention has surprisingly found that certain fluorinated aromatic compounds have HFC-134a.
It was made by the new finding that it is useful as a lubricant for a refrigeration system using a fluoroalkane as a refrigerant.

The present invention will be described in more detail below. The value of n in the formula (I) depends on the valence of R ¹ , and is 1 or 2 for reasons such as easiness of synthesis and taking an appropriate viscosity range. Also, in the formula (I), n
When is 2, plural R ^{2 s} may be the same or different.

R ¹ in the formula (I) is an aromatic ring having 1 to 4
It is a hydrocarbon that contains hydrogen atoms and hydrogen atoms are partially or wholly replaced by fluorine atoms. The number of aromatic rings in R ¹ is selected from the range of 1 to 4, but 1 or 2 is preferable in view of easy availability of raw materials. The fluorine atom contained in R ¹ in the formula (I) may be directly substituted on the aromatic ring in R ¹ or may be substituted on the carbon constituting the portion other than the aromatic ring. Good.

However, the number of fluorine atoms contained in R ¹ /
The ratio of the number of carbon atoms is 0.2 or more, preferably 0.4 or more. If this ratio is too low, the compatibility with the fluoroalkane becomes low, which is not preferable. Further, R ¹ in the formula (I) is substituted with a fluorine atom, but it may be further substituted with another substituent or may be linked with a linking group.

R ² in the formula (I) is 1 to 10 carbon atoms,
It is preferably 1 to 5, and more preferably 1 to 3 hydrocarbon groups. R ² may be substituted with a substituent or may be linked with a linking group. Examples of the substituents contained in R ¹ and R ² in the formula (I) are summarized below. Halogen atoms such as fluorine, chlorine and bromine, a hydroxyl group, a thiol group, an alkoxy group, a nitrile group, a nitro group and an ether group. , Thioether group, ester group, carbonyl group, sulfonyl group, sulfinyl group, carboxyl group, carboxylate group, amino group, thiocarbamate group, amide group, imide group, pyridine group, pyrimidine group,
Piperidine group, triazine group, phosphine group, benzimidazole group, phosphite group, triazole group,
Examples thereof include polar groups such as a tetrazole group, a thiazole group, a thiadiazole group, and various oxygen-containing, nitrogen-containing, phosphorus-containing, and sulfur-containing atoms.

Specific examples of R ^{1 in} the formula (I) include the followings.

[0025]

[Chemical 2]

[0026]

[Chemical 3]

Specific examples of R ² in the formula (I) include the followings.

[0028]

[Chemical 4]

The fluorinated aromatic compound of the formula (I) used in the present invention can be synthesized, for example, by reacting a phenolic hydroxyl group with an alkyl tosylate. However, the compound of formula (I) can be synthesized by various methods and is not limited to the above method. Further, the lubricating oil for a refrigerator used in the present invention is usually a rust inhibitor, an antioxidant, a viscosity index improver, a corrosion inhibitor, an oiliness improver, a pour point depressant, an extreme pressure additive, etc. Various additives added to the lubricating oil can be used by adding the amounts usually used.

[0030]

EXAMPLES The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited to the examples. The kinematic viscosity of the lubricating oil of the present invention was measured using an E type rotational viscometer (manufactured by Tokyo Keiki Co., Ltd.).

Reference Example 1 50 m of dimethylformamide
In 1 liter, potassium hydroxide 8.4g, 2,2-bis (4-hydroxyphenyl) hexafluoropropane 16.5g
Was added, and the mixture was stirred at 70 ° C. for 2 hours and a half. A solution prepared by diluting 30 g of ethyl p-toluenesulfonate with dimethylformamide was added dropwise to this solution at room temperature. After reacting at 80 ° C. for 3 hours, it was washed with water and purified by a silica gel column to obtain 4.1 g of a colorless transparent oil [S1].

Infrared absorption spectrum analysis, mass spectrometry [m
/ E 392 (M⁺), 323 (M ⁺-CF³)]Than
[S1] is a compound having the structure shown below.
confirmed.

[0033]

[Chemical 5]

Reference Example 2 50 m of dimethyl sulfoxide
5.0 g of potassium hydroxide and 1,3-bis (hexafluoro-2-hydroxy-2-propyl) benzene 1
2.3 g was added, and the mixture was stirred at 70 ° C. for 2 hours. A solution prepared by diluting 18 g of ethyl p-toluenesulfonate with dimethyl sulfoxide was added dropwise to this solution at room temperature. After reacting at 80 ° C. for 7 hours, it was washed with water and purified by a silica gel column to obtain 12.3 g of compound [S2] as a white solid.

Infrared absorption spectrum analysis, H ¹ -NMR analysis [2.5 ppm, t, 3H: 3.5 ppm, d, 2
It was confirmed from [H: 7.0-8.0 ppm, m, 4H (internal standard: tetramethylsilane)] that [S2] is a compound having the structure shown below.

[0036]

[Chemical 6]

(Examples 1 and 2) The compatibility of the oils [S1] and [S2] obtained in Reference Example 1 with a 1: 1 mixture of polypropylene glycol and HFC-134a was examined by the following method. First, 0.2 g of oil was placed in a glass tube, cooled with liquid nitrogen together with the glass tube, decompressed, and then about 1.5 g of HFC-134a was introduced. After sealing the glass tube, put it in a temperature-controlled water tank, and after the temperature reached equilibrium, visually check the oil and HFC-
The compatibility temperature range from room temperature to 90 ° C. was measured by the method of determining the compatibility with 134a. The low temperature region below room temperature was cooled in a methanol refrigerant and measured by the same method.

The kinematic viscosity of a 1: 1 mixture of oils [S1] and [S2] and polypropylene glycol at 40 ° C. was measured using an E-type rotational viscometer (manufactured by Tokyo Keiki Co., Ltd.). The results are shown in Table 1. (Comparative Examples 1 to 3) Commercially available perfluoropolyether and H
The results of examination of compatibility with FC-134a in the same manner as in Example 1 are shown in Table 1 together with the kinematic viscosity at 40 ° C.

In Table 1, Mn means the number average molecular weight. From Table 1, commercially available perfluoropolyethers are HF
Although the compatibility with C-134a in the low temperature region is insufficient,
In comparison, the oil of the present invention exhibits good compatibility with HFC-134a in a wide temperature range from a low temperature region to a high temperature region.

[0040]

[Table 1]

[0041]

According to the present invention, CFC-12 or HCF is used.
It shows good compatibility with a fluoroalkane such as HFC-134a, which is a promising refrigerant as a substitute for a chlorine atom-containing refrigerant such as C-22, in a wide temperature range from a low temperature range to a high temperature range, and as a lubricating oil for a refrigeration system. A novel use of a fluorine-containing aromatic compound having suitable characteristics as a lubricant for a refrigeration system is provided. Further, there is provided a refrigerant composition for a refrigeration system containing the above-mentioned fluorine-containing aromatic compound lubricant and a fluoroalkane-based refrigerant.

Furthermore, since the fluorine atom-containing aromatic compound represented by the formula (I) used in the present invention has a lower fluorine atom content than the perfluoropolyether oil, the perfluoropolyether oil is used. It has the advantage of lower manufacturing costs.

Claims (2)

[Claims] 1. A lubricant containing a fluorine-containing aromatic compound represented by (I) R ^1- (OR ² ) _n (I) [wherein n is 1 or 2]. R ¹ is an aromatic ring 1 to
It is a hydrocarbon containing four and a part or all of the hydrogen atoms are replaced by fluorine atoms. However,
The ratio of the number of fluorine atoms contained in R ¹ / the number of carbon atoms is 0.2 or more. R ² is a hydrocarbon group having 1 to 10 carbon atoms. When n is 2, the compound represented by formula (I) may be composed of plural kinds of OR ² groups. ] 2. A fluoroalkane-based refrigerant, and formula (I)
A refrigerant composition comprising a lubricant containing a fluorine-containing aromatic compound represented by: R ^1- (OR ² ) _n (I) [where n is 1 or 2] R ¹ is an aromatic ring 1 to
It is a hydrocarbon containing four and a part or all of the hydrogen atoms are replaced by fluorine atoms. However,
The ratio of the number of fluorine atoms contained in R ¹ / the number of carbon atoms is 0.2 or more. R ² is a hydrocarbon group having 1 to 10 carbon atoms. When n is 2, the compound represented by formula (I) may be composed of plural kinds of OR ² groups. ]