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Lubricating composition

The present disclosure is directed to additive and lubricant compositions and methods for use thereof. More particularly, this invention is directed to an additive composition comprising (i) a triazole compound substituted with an aryl moiety, (ii) a nitrogen-containing compound, and (iii) a sulfurized compound.

Lubricating oils as used in the internal combustion engines and transmissions of automobiles or trucks are subjected to a demanding environment during use. This environment results in oxidation of the oil which is catalyzed by the presence of impurities in the oil, and is also promoted by the elevated temperatures of the oil during use.

The oxidation of lubricating oils contributes to the formation of sludge in oils and the breakdown of viscosity characteristics of the lubricant. The oxidation is often controlled to some extent by selecting the proper antioxidant additives thereby significantly improving the life of the lubricating oils. Antioxidant additives can extend the useful life of the lubricating oil by, for example, reducing or preventing unacceptable viscosity increases and/or deposit formation.

Additionally, protecting the metal surface of an engine against wear degradation by selecting the proper balance of antiwear agents in a lubricating composition can significantly increase the life of the metal surface. Antiwear agents form a thin film on metal surfaces which prevents metal to metal contact, resulting in a decrease in the amount of wear. A well-known and commonly used antiwear agent is zinc dialkyldithiophosphate (ZDDP).

However, the demanding environment in which lubricating oils are subjected, including high temperatures and/or high pressures, decompose ZDDP in a lubricating oil composition. Studies have shown that some exhaust emission catalysts may be deactivated by phosphorus, largely derived from ZDDP compounds which have been the mainstay antiwear agents in passenger car motor oil and heavy duty diesel formulations for the past 50 years. Consequently, future engine oils will contain reduced phosphorus levels. Furthermore, as ZDDP decomposes and releases zinc molecules, these zinc molecules are capable of reacting with other performance additives present in the lubricating composition, creating sludge and other particulate matter that can cause adverse effects on engine performance. These undesirable effects of oxidation present problems in meeting ever more severe engine performance requirements.

Simply lowering the amount of ZDDP is not a practical solution to the problem because of the accompanying reduction of antiwear properties. Therefore, it would be desirable for a lubricating oil composition to comprise improved additives that reduce the oxidative degradation of lubricating oils.

It has now been discovered that a composition comprising (i) a triazole compound substituted with an aryl moiety, (ii) a nitrogen-containing compound, and (iii) a sulfurized compound can provide a highly effective system which can inhibit oxidation.

In accordance with the disclosure, there is provided an additive composition comprising (i) a triazole compound substituted with an aryl moiety; (ii) a nitrogen-containing compound represented by the formula (I):

wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono; and (iii) a sulfurized compound.

In an aspect, there is also provided a lubricant composition comprising a a major amount of a base oil; and a minor amount of an additive composition comprising (i) a triazole compound substituted with an aryl moiety; (ii) a nitrogen-containing compound represented by the formula (I):

wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono; and (iii) a sulfurized compound.

Moreover, there is provided a method of decreasing oxidation degradation of a lubricant composition, said method comprising providing to a machine a lubricant composition comprising a major amount of a base oil; and a minor amount of an additive comprising (i) a triazole compound substituted with an aryl moiety; (ii) a nitrogen-containing compound represented by the formula (I):