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Engine Lubricant Using Molybdenum Dithiocarbamate As an Antioxidant Top Treatment in High Sulfur Base Stocks

IP.com Disclosure Number: IPCOM000004774D
Publication Date: 2001-May-14
Document File: 9 page(s) / 54K

Publishing Venue

The IP.com Prior Art Database

Related People

David M. Shold: ATTORNEY

Abstract

The present invention provides: . A composition comprising: (a) a major amount of an API Group I mineral oil base stock, wherein said base stock contains at least 300 ppm sulfur; (b) a molybdenum dithiocarbamate in an amount suitable to provide about 50 to about 600 ppm molybdenum to the composition; (c) a succinimide dispersant having a polyolefin backbone, where the polyolefin has a number average molecular weight greater than about 1500; (d) a zinc dialkyldithiophosphate derived from at least one secondary alcohol; and (e) at least one oxidation inhibitor selected from the group consisting of hindered phenols, alkylated aromatic amines, and sulfurized olefins.

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By The Lubrizol Corporation and Jack C. Kelley

TITLE

Engine Lubricant Using Molybdenum Dithiocarbamate As an Antioxidant Top Treatment in High Sulfur Base Stocks

BACKGROUND OF THE INVENTION

The present invention relates to the engine oils formulated the meet the new specifications of ILSAC GF-3 using conventional high sulfur base stocks.

Lubricating base stocks or base oils have been categorized into Groups I-V by the American Petroleum Institute (API). They are characterized by their sulfur content, "saturates" or paraffin content and their viscosity index. Group I and II are most abundant base stocks and most commonly used to formulate engine lubricants. Group I base stocks are typically much higher in sulfur content than Group II. The trend is toward Group II base stocks which are both low in sulfur and low in aromatic content. The problem presented to the lubricating oil additive supplier is to formulate a performance additive package for both types of oils, often for the same customer. The performance of a lubricant is demonstrated by passing engine tests (ASTM sequence tests.) The engine testing is a costly investment for the additive supplier. The Sequence IIIF, a General Motors developed test that measures oxidation and wear among other properties, is one of the engine tests that is sensitive to the starting base oil. An additive package formulated to pass the IIIF test in Group II base stocks, may not be adequate for Group I base stocks. This results in multiple formulations and engine testing and will often leads to two additive packages. This is not always economical or convenient for the additive supplier or the customer, the lubricating oil manufacturer.

Lubricating oils containing molybdenum compounds like molybdenum dithiocarbamates (MoDTCs) have been known in the literature. Le Suer in US Patent 3,541,014 showed the value of using oil soluble molybdenum compounds in lubricants in combination with other additives to improve extreme pressure capabilities and antiwear properties of the lubricants. Papay et al. in US Patent 4,178,258 discloses a lubricating oil composition suitable for use in an internal combustion engine, comprising a major amount of a mineral oil and a minor wear and friction reducing amount of an oil soluble molybdenum dithiocarbamate (MoDTC). Inoue et al. in US Patent 4,529,526 discloses a lubricant consisting essentially of a base oil, a molybdenum dithiophosphate (MoDTP) or a MoDTC, a zinc dithiophosphate with at least 50% secondary alkyl groups, an overbased calcium sulfonate and a succinimide dispersant or boron derivative thereof. In US Patent 4,846,983 Ward teaches the production of a molybdenum dithiocarbamate (MoDTC) based on a primary amine and further showed the value in using the MoDTC as an oxidation inhibitor in a Oldsmobile Sequence IIID test, a second generation predecessor of the Sequence IIIF test.

Several patents teach the use of molybdenum compounds in engine oil for use in low sulfur and/or low aromat...