JPH03109492A - Lubricating oil for fluorocarbon compressor - Google Patents

Abstract

PURPOSE:To obtain the title lubricating oil using a specific polyoxypropylene glycol dialkyl ether, etc., as base oil, having good compatibility to fluorocarbon R-134a over wide temperature range and having low hygroscopicity and good stability. CONSTITUTION:The aimed lubricating oil using a polyoxypropylene glycol dialkyl ether or polyoxyethylene-polyoxypropylene copolymer expressed by the formula [R1 and R2 are 1-4C alkyl and R1+R2 is <=6C; m+n is integer of 701-3000 (preferably 701-2000) and n is 0 or integer of <=m] as a base oil. Then lubricating oil is suitable, especially as air conditioner for car.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a lubricating oil for a compressor that uses fluorocarbons as a refrigerant, and in particular fluorocarbons R-134a (I , 1,1,2-tetrafluoroethane).

(Prior Art) Conventionally, refrigerators, air conditioners, refrigerators, etc. have used fluorocarbons whose constituent elements are fluorine and chlorine as refrigerants, such as R-11 (dichloromonofluoromethane), R-12 (dichlorodifluoromethane), Freon such as R-22 (monochlorodifluoromethane) has been used, but in connection with the recent problem of ozone layer depletion, a new type of refrigerant that does not have any impact on the ozone layer has begun to appear, such as R-1348.

On the other hand, regarding refrigeration oil, many mineral oil-based and synthetic oil-based oils have been known, but it has been found that these cannot be used because they have no compatibility with the new Freon R134a at low temperatures. . Therefore, this countermeasure has become an important issue today.

In addition, other properties required for refrigeration oil include lubricity,
These include wear resistance, sealing performance, heat resistance, and sludge precipitation prevention properties, and these points also need to be considered.

Incidentally, polyether-based synthetic lubricating oil is an example of conventionally known synthetic oil, and this is described in Oil Chemistry Journal, Vol. 2.
9, No. 9, pp. 336-343 (I980) and Belotchik, Vol. 8, No. 6, No. 562-566
There is an introduction in g (I985). Also, JP-A-61-28
No. 1199 discloses a mixture of polyglycol and alkylbenzene represented by the following formula, 1?1 +O(RZO)-1h) -, and JP-A-57-63395 discloses a polyether, for example, with an addition mole number of 53. An oil obtained by mixing a high molecular weight polyoxypropylene monobutyl ether with an epoxycycloalkyl compound, and JP-A-59-11759
Publication No. 0 introduces high viscosity mixed oils of polyether compounds and paraffinic or naphthenic mineral oils.

(Problems to be Solved by the Invention) However, none of the above-mentioned known synthetic oil-based lubricating oils could be used as lubricating oil for R-134a Freon compressors due to problems such as compatibility.

On the other hand, U.S. Patent No. 4,755.316 describes a refrigerating machine oil for Freon R134a that has hydroxyl groups (-O
H) is a polyoxyalkylene glycol (hereinafter referred to as PA
Compared to general PAG, which has a hydroxyl group and an alkyl group at the end, this PAG is compatible with Freon R-134a and dissolves in a wider temperature range, making it suitable for use in refrigeration systems. It is said to improve oil return to the compressor and prevent seizure when the compressor is started at high temperatures. It is introduced that the compatible temperature range with Freon R-134a is 40°C to +50°C.

However, Freon R134a is a candidate refrigerant to replace Freon R-12, and is mainly used in car air conditioners and refrigerators.

In particular, in the case of a car air conditioner, the temperature can far exceed +50°C when the compressor starts up in the summer. In this case, with the refrigerating machine oil described in U.S. Pat. No. 4,755,316, the oil and refrigerant undergo two-phase separation in the compressor at startup, with the refrigerant having a higher specific gravity becoming the lower layer, and the oil and refrigerant are separated into two phases in the absence of lubricating oil. It may start up and cause the compressor to burn out. In other words, the two-layer separation temperature at high temperature is +
It can be said that 50°C is insufficient at high temperatures such as in summer.

Another problem is that it is highly hygroscopic.

Therefore, an object of the present invention is to provide a fluorocarbon compressor that has excellent compatibility with refrigerants, particularly the new refrigerant Freon R134a, over an extremely wide temperature range compared to the conventional technology, and has low hygroscopicity and good stability. An object of the present invention is to provide a lubricating oil for fluorocarbon compressors that is suitable for use in car air conditioners.

(Means for Solving the Problems) The present inventors have conducted intensive research on various synthetic oils to solve the above problems, and have found that specific polyoxyalkylene glycols are effective in achieving the objects of the present invention. This discovery led to the completion of the present invention.

That is, the present invention provides a lubricating oil for fluorocarbon compressors using a specific polyoxypropylene glycol dialkyl ether or dialkyl ether of polyoxyethylene polyoxypropylene copolymer as a base oil having a structure represented by the following general formula (I). It is.

In other words, the present invention is based on R8-t+CH! -C)l-0+-e-CHz-CH2
-0″r:Rz(I)OH3 (R and R2 in the formula have the same or different carbon number 1
~4 alkyl groups, the number of carbon atoms in R and +R2 is 6 or less, and m+n has an average molecular weight of more than 700 and 300
An integer less than or equal to 0, n indicates 0 or an integer where m>n)
It is characterized by using the compound represented by as the base oil.

Such compounds are difficult to obtain on the market. They are Union Carbide Corporation and Asahi Denka Kogyo Co., Ltd.
General products from PAG manufacturers such as PAG manufacturers have alkyl groups with 4 or more carbon atoms, and they are difficult to be miscible with R-134a. Therefore, the present inventors prepared and investigated the compound of general formula (I).

In the present invention, the reason why the average molecular weight of the compound represented by the general formula (I) is limited to within the above range is as follows.

That is, if the average molecular weight is 700 or less, 1
The viscosity at 00°C is 8 cSt or less, which is insufficient for use as a lubricating oil for car air conditioners.

Furthermore, when used in a car air conditioner, swelling of the rubber hose is a major problem, so it is essential to select a material with a molecular weight of over 700 from the viewpoint of rubber swelling. On the other hand, if the molecular weight exceeds 3000, the compatibility with Freon R-134a decreases, making it impossible to achieve the object of the present invention. In general, the compatibility between refrigeration oil and refrigerant, that is, the characteristics up to the two-phase separation temperature, is considered to be a low-temperature characteristic, but when the refrigerant is Freon R134a, this behavior differs from the conventional behavior, and in addition to low-temperature separation, there is a high-temperature characteristic. There is also a two-phase separation temperature. For this reason, in the present invention, the molecular weight is particularly set to 3000 or less to ensure compatibility over a wide temperature range.

Incidentally, oils with poor compatibility have difficulty returning to the compressor, causing the compressor to seize.

Furthermore, even if the molecular weight is within the range of more than 700 and less than 3000 in the present invention, if the total number of carbon atoms in the alkyl group in the formula (I) is 7 or more, the compatibility with Freon R-134a is poor. This makes it difficult to use it as refrigeration oil. In other words, in the case of polyoxypropylene glycol dialkyl ether or dialkyl ether of polyoxyethylene polyoxypropylene copolymer, when the molecular weight is 3000 or less and the number of carbon atoms in the alkyl groups at both ends is 1 to 4, it is called Freon R134a. Compatible;
It is preferable for use as a refrigerating machine oil. Further, in the case where R and R2 in the formula (I) have 3 or 4 carbon atoms, those having a branched alkyl group are particularly preferred. In order to make the compatibility with Freon R134a more preferable, R1 and R2 of the compound of formula (I) have 1 carbon number.
It is preferable to select ~3 molecules having an average molecular weight of more than 700 and less than 2000. Furthermore, when the ratio of polypropylene oxide to polyethylene oxide is greater than 1:1, low-temperature properties such as pour point deteriorate and hygroscopicity increases.

Polyoxypropylene glycol alkyl ether containing no polyethylene oxide is preferred because it has the lowest hygroscopicity.

As mentioned above, the polyoxypropylene glycol dialkyl ether and the dialkyl ether of polyoxyethylene polyoxypropylene copolymer used in the present invention have excellent low-temperature compatibility with Freon R-1348, and also have excellent lubrication under the Freon atmosphere. Performance and thermal stability are also good.

As mentioned above, the polyoxypropylene glycol dialkyl ether of general formula (I) or its analogues must exhibit the function as a lubricant, and the selection of viscosity is important. About 40cSt, especially 8 to 20cS for energy saving.
It is preferable that the

It goes without saying that the fluorocarbon compressor lubricating oil of the present invention may contain appropriate antioxidants, hydrochloric acid scavengers, and anti-wear agents that have been conventionally used in refrigeration oils.

In addition, for viscosity adjustment, etc., a boat fishing PAG can be mixed and used.

(Examples) The present invention will be explained in detail below using Examples and Comparative Examples.

1-7 611-5 As the polyoxypropylene glycol dialkyl ether of the present invention and the dialkyl ether of the polyoxyethylene polyoxypropylene copolymer, Al-Al is shown in Table 1 below as an example and a general as a comparative example. The performance of Freon R-134a as a lubricating oil for a compressor was evaluated using sample oils of PAG AIO to A14.

The lubricity, compatibility, and thermal stability of the test oils shown in Table 1 as lubricating oils for compressors were evaluated under the conditions shown below.

According to ASTM D-3233-73, the Palex seizure load was measured by blowing Freon R-134a (70 Id/ml) and controlling the atmosphere.

■Productivity Test oil 0.6g and refrigerant (Freon R-134a) 2.4
After sealing g in a glass tube, cooling and heating were performed at 1"C per minute, and the temperature at which two-phase separation occurred, that is, the two-phase separation temperature, was measured.

1 g of oil sample and refrigerant (Freon R-134a and R-12
) Ig and catalyst (iron, copper, and aluminum wires) were sealed in a glass tube, heated to 175°C, and 10 days later, the hue of the sample oil was determined by ASTM.

The degree of swelling (%) of acrylonitrile-butadiene rubber with respect to Jk1 dish test oil was evaluated under conditions of 120°C and 120 hours.

Hygroscopicity: 60 g of sample oil was placed in a 100 d beaker in an atmosphere with a temperature of 25° C. and a humidity of 70%, and the water content was compared and evaluated after 3 hours of being opened.

The above evaluation results are shown in Table 2 below.

From the evaluation results shown in Table 2, the following was confirmed.

The two-phase separation temperatures of the sample oils of Examples 1 to 7 are sufficiently low on the low temperature side and sufficiently high on the high temperature side, and have excellent compatibility. It also has good lubricity and thermal stability, and has low rubber swelling and excellent rubber swelling properties. In particular, if the refrigerant is R-
In the process of transitioning from R-12 to R-134a, there may be cases where R-12 contaminates, especially in car air conditioners.
The thermal stability of the compounds of the present invention in which alkyl groups were introduced at both ends of Examples 1 to 7 in the coexistence with R-12 was also that of Comparative Example 2.
It is much better than the general PAG of No. 3. Among them, Examples 1.2 and 6.7 have a high high-temperature two-layer separation temperature, and when compared with the average molecular weight of 1000 (Examples 4 and 6.7), those having a branched alkyl group are more preferable. I understand. As described above, the present invention is extremely suitable as a lubricating oil for R134a. In addition, hygroscopicity is also common in PAG.
It can be said that it is considerably lower than (Comparative Example 2.3). In these respects, the product of the present invention can be said to be far superior in properties to PAG, which is generally used as refrigerating machine oil.

On the other hand, the sample oil of Comparative Example 1 has good compatibility, but has a low viscosity and is inferior in terms of lubricity and rubber swelling.
Undesirable. In addition, the test oil of Comparative Example 2°4.5 was R-
It is not compatible with R-134a and cannot be used as a refrigerating machine oil for R-134a. This shows that the molecular weight, the number of carbon atoms in the terminal alkyl group, and its structure are important for compatibility with R-134a. The test oil of Comparative Example 3 is a compound described in U.S. Pat. It has poor stability over time and extremely high hygroscopicity, so it cannot be said to be a good refrigerating machine oil.

(Effects of the Invention) As explained above, the refrigerating machine oil for a fluorocarbon compressor of the present invention maintains sufficient compatibility with fluorocarbon R134a as a refrigerant and has excellent overall performance, so it is suitable for use under fluorocarbon regulations. Amid social trends, even if fluorocarbon R-134a, which is attracting attention as an alternative to fluorocarbon R-12, is used, the conventional system can be used as is, making a sufficient contribution to reducing the amount of regulated fluorocarbons used. The effect of being able to do this is obtained.

Claims (1)

[Claims] 1. The following general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (R_1 and R_2 in the formula are the same or different alkyl groups having 1 to 4 carbon atoms) The number of carbon atoms in R_1+R_2 is 6 or less, m+n is an integer with an average molecular weight of more than 700 and less than 3000, and n is 0 or an integer of m≧n) as the base oil. A lubricating oil for fluorocarbon compressors. 2. The fluorocarbon compression according to claim 1, wherein in the above formula (I), R_1 and R_2 represent the same or different alkyl groups having 1 to 3 carbon atoms, and have an average molecular weight of more than 700 and less than 2000. Machine lubricant. 3. The lubricant for a Freon compressor according to claim 1, which is used for compressing Freon R-134a.