Liquid Additives for the Stabilization of Lubricant Compositions

Abstract

A lubricating oil composition comprising: (A) a base stock; and (B) a liquid additive package. The liquid additive package comprises: (i) an alkylated diphenylamine; (ii) at least 5 weight % of a phenyl naphthylamine, based on the weight of the additive package; and (iii) a sulfur-containing phenol.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority to U.S. Provisional Application No. 61 / 080,547, filed on Jul. 14, 2008, the entirety of which is incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to lubricating oil compositions. More specifically to lubricating oil compositions comprising additive packages for reducing oxidative deterioration.BACKGROUND OF THE INVENTION[0003]Lubricants, such as those used in a variety of machinery, are susceptible to oxidative deterioration during storage, transportation, and usage, particularly when such lubricants are exposed to high temperatures and iron catalytic environments, which greatly promote the oxidation of the lubricant. This oxidation, if not controlled, contributes to the formation of corrosive acidic products, sludge, varnishes, resins, and other oil-insoluble products and may lead to a loss of designated physical and tribological properties of the lubricant...

AI Technical Summary

Problems solved by technology

Lubricants, such as those used in a variety of machinery, are susceptible to oxidative deterioration during storage, transportation, and usage, particularly when such lubricants are exposed to high temperatures and iron catalytic environments, which greatly promote the oxidation of the lubricant.

This oxidation, if not controlled, contributes to the formation of corrosive acidic products, sludge, varnishes, resins, and other oil-insoluble products and may lead to a loss of designated physical and tribological properties of the lubricants.

These oxidation products may lead to the formation of harmful deposits on critical engine parts, such as the pistons, piston liners, valves, and valve lifters.

However, under such operating conditions, the thermal and oxidative stress on the lubricants has become severe that conventional ADPA antioxidants insufficiently stabilize the lubricants.

Gatto states that there are a number of problems that may be associated with the use of hindered phenols.

Gatto states that hindered phenols under high temperatures can dealkylate and produce free phenol and that water extractablility of certain water soluble phenols is another potential problem.

However, PNA is typically sold as a solid at room temperature, and, as such, is not easily blended into the base oil.

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