JPS627239B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lubricating oil composition for compressors that has extremely excellent antioxidative properties. Compressor oil is generally used in compressors for the purposes of cooling by removing heat generated by adiabatic compression, lubricating bearings and other parts, and sealing to prevent gas leakage at sliding parts. Gases to be compressed include air, oxygen, carbon dioxide, nitrogen, hydrogen, various hydrocarbon gases, chlorine gas,
There are ammonia gas, etc., but of these, air compressors are the most common and have the most severe conditions for compressor oil. In an air compressor, the presence of high temperature and high pressure air, copper,
The most severe conditions for compressor oil oxidation are created by the presence of metals that catalyze oxidation, such as iron, and by the presence of condensate water produced by compression. For this reason, when ordinary turbine oil, engine oil, hydraulic oil, etc. are used as compressor oil, the oil deteriorates due to oxidation in a very short period of time, and at the same time, it can cause serious problems such as the formation of sludge or the corrosion of copper-based materials. causing serious trouble. Once such a phenomenon occurs, it will not return to its original state unless the compressor is overhauled or thoroughly cleaned internally, and the cost and time required for this will be enormous. The purpose of the present invention is to have an extremely long oxidation life even when used in a compressor, to reduce the possibility of serious problems such as sludge formation even if the oil deteriorates due to oxidation, and to have a favorable color of the oil after use. An object of the present invention is to provide a compressor oil composition with extremely excellent antioxidant properties. Many compounds are known and are in practical use as antioxidants that are effective when added to lubricating oils, but it is clear that a single antioxidant cannot maintain the oxidation life required for compressor oils. It became.
For example, if peroxide decomposers such as aromatic amines, alkylphenols, or zinc dialkyldithiophosphates are added alone to mineral lubricating oils and are used in compressors, they will quickly deteriorate due to oxidation and become unusable. I can't stand it. It is also known that the antioxidant effect is generally increased by using an antioxidant in combination, particularly a free radical chain terminator and a peroxide decomposer. However, as will be discussed later, simply using two types of antioxidants together, even if it is a combination of a free radical chain terminator and a peroxide decomposer, will not work under severe usage conditions. It has insufficient antioxidant properties and cannot be used as a compressor lubricant with a long oxidation life. The compressor oil composition according to the present invention is characterized in that a synergistic effect can be obtained by using three specific antioxidants together, and thereby each antioxidant can be used alone or in combination. We succeeded in significantly extending the oxidation life of the compressor oil compared to the previous case. The present invention provides 1(A) lubricating base oil with a viscosity of 20 to 100 cst at 37.8°C, (B) (a) diphenylamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, phenyl-p-octylphenyl. Aromatic amine selected from amine, p,p'-dioctyldiphenylamine, 2,6-di-t-butyl-α-dimethylamine-p-cresol and tetramethyldiaminodiphenylmethane (b) 2. 6-di-t-butyl-p-cresol, 4,4'-methylenebis(2,6-di-
t-butylphenol), 4,4'-dihydroxy-3,3',5,5'-tetra-t-butylbiphenyl, 4,4'-thiobis(2,
6-di-t-butylphenol), bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide and 2,2'-
Alkylphenol selected from methylenebis(4-methyl-6-t-butylphenol) and (c) O,O′-dipropyldithiophosphoric acid-S
-dodecyl, O,O'-bis(propylphenyl)-S-phenylmethyldithiophosphate and O,O'-bis(propylphenyl)-S-styryldithiophosphate. The present invention relates to a lubricating oil composition for a compressor, characterized in that the three components of alkyl or aryl triester of phosphoric acid are each contained in an amount of 0.01 to 3.0% by weight based on the total amount of the lubricating oil composition. The additives used in the present invention will be explained in detail below. The aromatic amine (a) in (B) above refers to diphenylamine, phenyl-α-naphthylamine, phenyl-
β-naphthylamine, phenyl-p-octylphenylamine, p,p'-dioctyldiphenylamine, 2,6-di-t-butyl-α-dimethylamino-p-cresol, tetramethyldiaminodiphenylmethane and these It is a mixture of Among these, phenyl-α-naphthylamine and diphenylamine are particularly preferred. The (b) alkylphenol in (B) above is 2,6-
Di-t-butyl-p-cresol, 4,4'-methylenebis(2,6-di-t-butylphenol), 4,4'-dihydroxy-3,3',5,5'-tetra-t- Butylbiphenyl, 4,4'-thiobis(2,6-di-t-butylphenol), bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide, 2,2'-methylenebis(4
-methyl-6-t-butylphenol) and mixtures thereof. Among these, 4,
Particularly preferred are 4'-methylenebis(2,6-di-t-butylphenol) and 2,6-di-t-butyl-p-cresol. The alkyl or aryl triester of dithiophosphate (c) in (B) above refers to O,O'-dipropyldithiophosphate-S-dodecyl, O,O'-bis(propylphenyl)-S- enylmethyl dithiophosphate, O,O'-bis(propylphenyl)-S-styryldithiophosphate, and mixtures thereof. Among these, O,O'-bis(propylphenyl)-S-styryldithiophosphate and O,O'-bis(propylphenyl)-S-phenylmethyldithiophosphate are particularly preferred. The three types of additives used in the present invention are each 0.01 to 3.0% by weight based on the total amount of the lubricating oil composition, preferably
It is preferable to add 0.03 to 1.0% by weight. Particularly preferred addition amounts are (a) 0.05-0.3% by weight of aromatic amines, (b) 0.05-0.2% by weight of alkylphenols, and (c) 0.03-0.2% by weight of alkyl or aryl triesters of dithiophosphoric acids. In addition, (A) lubricant base oil in the present invention is 37.8℃
The viscosity at is 20~100cst, preferably 30~
50 cst, mineral lubricating oil or its refined products;
and synthetic hydrocarbon oils with a viscosity of 20 to 100 cst. at 37.8°C. In addition to antioxidants, the lubricating oil composition for compressors of the present invention may also contain detergent-dispersing agents, metal deactivators, rust inhibitors, anti-foaming agents, pour point depressants, etc., as necessary. . The effects of the composition according to the present invention will be explained in detail through the following examples, but the present invention is not limited by these examples. Examples 1 to 10 A lubricating oil composition for a compressor was prepared by adding various additives as shown in Table 1 to a mineral lubricating oil base oil having a viscosity of 35.0 cst at 37.8°C. 2,5-dimercapto-1,3,4 used as various additives in the table
- Thiadiazole and benzotriazole are metal deactivators, alkenylsuccinic acid half esters are rust inhibitors, and silicone oils are antifoam agents. The performance of the lubricating oil composition for compressors was evaluated using a rotary vane air compressor, an Indiana Stirling oxidation test, a rotary pump oxidation test, and a turbine oil oxidation stability test. When conducting a practical test for 2000 hours with a rotary vane air compressor, the acid value after the test is preferably 0.3 mg KOH/g or less, and when conducting the Indiana Stirling oxidation test at 165.5°C for 48 hours, after the test It is said that the acid value of is preferably 0.5 mg·KOH/g or less. On the other hand, for rotary pump oxidation tests, it is said that an oxidation life of 150 minutes or more, and 400 minutes or more under strict conditions, is preferable. Furthermore, the acid value in the turbine oil oxidation stability test
It is said that the time required to reach 1.0 mgKOH/g is preferably 2,500 hours or more, more preferably 4,000 hours or more, and the hue (union value) at 2,000 hours is low and sludge formation is low. is considered preferable. The compositions of Examples 1 to 10 are compositions according to the present invention, and include three additives: (a) aromatic amine;
A composition using (b) an alkylphenol and (c) an alkyl or aryl triester of dithiophosphoric acid. The compositions of Examples 1 to 10 were excellent on average in both the acid value and oxidation test life after the practical test. The compositions of Examples 1 to 10 also showed excellent results in the turbine oil oxidation stability test according to JIS K2515. That is, these compositions take a long time to reach a certain total acid value, and the hue after a certain period of time also shows a small union value, so it can be said that they have extremely excellent antioxidative properties. Comparative Examples 1 to 10 Comparative Examples 1 (commercially available lubricating oil for compressors) and Comparative Examples 2 to 4 are compositions containing only one of the three additives, and the compositions of Examples 1 to 10 are Compared to , the results in either or both of the acid value and oxidation test life after practical tests are significantly inferior, and the results in the turbine oil oxidation stability test are also poor, so it cannot be used for a long time as a compressor lubricant. . Comparative Examples 5 to 8 are compositions in which two types of antioxidants are added, and although they exhibit somewhat better performance than the compositions of Comparative Examples 1 to 4, they are inferior to the compositions of Examples 1 to 10. It has poor antioxidant properties and cannot be used for long periods of time under severe usage conditions. That is,
Comparative Examples 5 and 6 are compositions that use the antioxidants (b) and (c) of the present invention in combination, but the rotary pump oxidation test life is short, and the acid value in the turbine oil oxidation stability test is 1.0 mgKOH. /g is also short, which is not preferable. Comparative Example 7 is (a) and (c) of the present invention.
Although this composition used a combination of antioxidants, it showed performance comparable to the compositions of Examples 1 to 10 in terms of acid value and oxidation test life after practical tests, but its performance in the turbine oil oxidation stability test was inferior. In particular, the amount of sludge produced is extremely large, which poses a practical problem. Comparative Example 8 is a composition that uses the antioxidants (a) and (b) of the present invention in combination, but the acid value after the practical test was poor, and the amount of sludge produced was low even in the turbine oil oxidation stability test. Very common and undesirable. Comparative Examples 9 and 10 are compositions in which three antioxidants (a) and (b) of the present invention and zinc dialkyldithiophosphate, which is well known as a peroxide decomposer, are used in combination. The acid value after a practical test using a rotary vane air compressor and the results of a turbine oil oxidation stability test are inferior to those of the composition of the present invention. As is clear from the above Examples and Comparative Examples, the extremely excellent antioxidant properties of the lubricating oil composition for compressors of the present invention are due to the three specific antioxidants (a), (b), and (c). This was achieved for the first time through a synergistic effect by using antioxidants as essential ingredients, and the use of one or two of (a), (b) and (c) or three antioxidants Even when used in combination, the results cannot be obtained if a peroxide decomposer other than the alkyl or aryl triester of dithiophosphoric acid is used as (c).

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Claims (1)

[Claims] 1 (A) For a lubricating base oil having a viscosity of 20 to 100 cst at 37.8°C, (B) (a) diphenylamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine,
phenyl-p-octylphenylamine,
p,p'-dioctyldiphenylamine, 2,
6-di-t-butyl-α-dimethylamino-
an aromatic amine selected from p-cresol and tetramethyldiaminodiphenylmethane, (b) 2,6-di-t-butyl-p-cresol,
4,4'-methylenebis(2,6-di-t-butylphenol), 4,4'-dihydroxy-
3,3',5,5'tetra-t-butylbiphenyl, 4,4'-thiobis(2,6-di-t-butylphenol), bis(3,5-di-t-
an alkylphenol selected from butyl-4-hydroxybenzyl) sulfide and 2,2'-methylenebis(4-methyl-6-t-butylphenol), and (c) O,O'-dipropyldithiophosphoric acid-S -dodecyl, O,O'-bis(propylphenyl)-S-phenylmethyldithiophosphate and O,O'-bis(propylphenyl)-S-styryldithiophosphate. 1. A lubricating oil composition for a compressor, characterized in that the three components of alkyl or aryl triester of phosphoric acid are each contained in an amount of 0.01 to 3.0% by weight based on the total amount of the lubricating oil composition.