JP2977871B2 - Freon resistant lubricating oil - Google Patents

Description

The present invention relates to a CFC-resistant industrial oil based on a novel mixed fatty acid ester.

<Related Art> Conventionally, as a refrigerating machine oil, naphthenic oils, paraffinic oils, alkylbenzenes, polyglycol-based oils and mixtures thereof, or those obtained by blending various base oils with additives are generally used. I have.

On the other hand, fluorocarbons such as trichloromonofluoromethane (CFC11), dichlorofluoromethane (CFC12), monochlorodifluoromethane (CFC22), and trichlorotrifluoroethane (CFC113) have been used as refrigerants. Ozone layer depletion has become a social problem, and it does not contain chlorine, which affects ozone depletion, as a substitute for chlorofluorocarbons. Freon 12 has been widely used in refrigerators such as home refrigerators, air conditioners and car air conditioners.
1,1,1,2 Tetrafluoroethane (R134a), which has similar thermodynamic properties to refrigeration oil, has attracted attention, but has poor compatibility with commonly used refrigerating machine oil.

<Problems to be solved by the present invention> It is an object of the present invention to provide a lubricating oil for a refrigerator suitable for using R134a as a refrigerant.

<Means for Solving the Problems> In order to solve the above problems, the present inventors have studied various synthetic oils and found that trimethylolpropane and / or pentaerythritol and the following chemical structures (a) and (b) It has been found that esters with two different mixed fatty acids are superior.

(A) Neoacid having 5 to 9 carbon atoms (b) Linear saturated fatty acid having 3 to 10 carbon atoms provided that the mixing weight ratio of (a) and (b) is 80:20 to
It is 5:95.

The mixed fatty acid ester of the present invention is obtained by completely or partially esterifying the hydroxyl group of trimethylolpropane and / or pentaerythritol.

Generally, the lubricating oil for a refrigerator using R134a as a refrigerant has good compatibility with R134a as well as a pour point of −10 ° C. or less, preferably −20 to −60 ° C., and at 100 ° C. The kinematic viscosity needs to be in the range of 5 to 40 cst. If the pour point exceeds -10 ° C, the refrigerating machine oil may be solidified at a low temperature, which is not preferable. Also 10
If the kinematic viscosity at 0 ° C. is less than 5 cst, the sealability of the compressor cannot be maintained, while if the kinematic viscosity exceeds 40 cst, the viscosity becomes too high and lubricity deteriorates. Further, the viscosity index, which is an index of the viscosity temperature gradient, is preferably 100 or more. The mixed fatty acid ester of the present invention satisfies the above characteristics.

The neo acid used in the present invention means one in which the carbon at the 2-position is completely substituted with an alkyl group. The neo acids include pivalic acid, 2,2 dimethyl butanoic acid, 2,2 dimethyl pentanoic acid, 2 ethyl 2 methyl butanoic acid, 2,2 dimethyl heptanoic acid, and 2,2,4,4 tetramethyl pentanoic acid. Can be Examples of the linear fatty acid include propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, and the like, and these can be used in combination.

From the viewpoint of chemical stability and compatibility with R134a, neoacid esters having 9 or less carbon atoms are the most excellent, but their viscosity index and pour point are so high that it is difficult to use them alone. For this reason, a linear saturated fatty acid having 10 or less carbon atoms having a low viscosity index and pour point was used in combination. Neoacids having 4 or less carbon atoms have poor lubricity and flammability, and linear saturated fatty acids having 2 or less carbon atoms have extremely low chemical stability in the presence of Freon.

These characteristics naturally depend on the mixing ratio of the mixed fatty acids (a) and (b). That is, when the weight ratio of (a) and (b) is more than 80:20, lubricity and flammability decrease, and viscosity at low temperature increases. If the ratio is less than 5:95, the low-temperature characteristics deteriorate.

The mixed fatty acid ester of the present invention can be produced by a normal ester production method, and can be purified by a series of treatments such as deacidification, washing with water, dehydration, decolorization, and filtration as in the case of purifying a normal ester. it can.

In order to further enhance the performance of the mixed fatty acid ester of the present invention, if necessary, other lubricating oils and lubricating oil additives such as antioxidants, oiliness improvers, defoamers, metal deactivators, etc. Can be added for use.

<Examples> Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Using the raw materials described in Table 1 of Examples 1 to 6 and Comparative Examples 1 to 4, those synthesized by ordinary esterification reaction were tested, and the viscosities and viscosity indices at 40 ° C and 100 ° C ( JIS K2283), pour point (JIS K2269), acid value (JIS K2561) and compatibility with R-134a were measured. Table 2 shows the results. The percentages in the examples are on a weight basis unless otherwise specified.

Claims (2)

(57) [Claims] 1. A CFC-resistant lubricating oil comprising an ester of trimethylolpropane and / or pentaerythritol and a mixed fatty acid of the following (a) and (b) as a base oil. (A) Neoacid having 5 to 9 carbon atoms (b) Linear saturated fatty acid having 3 to 10 carbon atoms provided that the mixing weight ratio of (a) and (b) is 80:20 to 5: 9
5 2. A CFC-resistant lubricating oil according to claim 1, wherein (a) is 2,2 dimethylpentanoic acid, 2ethyl dimethylbutanoic acid or 2,2 dimethylheptanoic acid.