Use of nanomaterials as effective viscosity modifiers in lubricating fluids

Abstract

Nanomaterials have been used as a supplement or replacement of traditional polymer-based viscosity modifiers for lubricants and other related fluids. Compared with traditional polymer-based viscosity modifiers, nanomaterials possess better viscosity-index modification functions, i.e., more even viscosity increase across the whole temperature range. Meanwhile, a cost-effective way of making nanomaterials have been developed based on commercially available graphite materials, and the resulting nanoparticles of graphite are nanodisks (nanoplates). Furthermore, it provides a viscosity modifier which exhibits temporary shear loss, which can contribute to fuel economy, but no permanent shear loss.

Description

[0001] This application claims priority from U.S. Provisional Application Ser. No. 60 / 592,570 filed on Jul. 31, 2004 and Provisional Application Ser. No. 60 / 254,959 filed on Dec. 12, 2000 and U.S. Pat. No. 6,783,746 which issued on Aug. 31, 2004 from application Ser. No. 10 / 021,767 filed on Dec. 12, 2001 and application Ser. No. 10 / 929,636 filed on Aug. 30, 2004 and application Ser. No. 10 / 730,762 filed on Dec. 8, 2003 which claims priority from PCT / US02 / 16888 filed on May 30, 2002 and application Ser. No. 10 / 737,731 filed on Dec. 16, 2003 all of which are incorporated herein in their entirety.TECHNICAL FIELD [0002] The present invention relates to a novel use of nanomaterial as a viscosity modifier for a lubricating oil and a lubricating oil composition. More particularly, the invention relates to a novel viscosity modifier for a lubricating oil capable of producing a lubricating oil composition having excellent viscosity index and lubricating oil compositions containing such a vis...

AI Technical Summary

Benefits of technology

[0019] The present invention provides at a minimum, a fluid of lubricant containing from 0.001% to 50% by weight nanoparticles, and preferably, from 0.01% to 25% by weight, and more preferably, from 0.1% to 20% by weight of nanoparticles. Preferably, however, a minimum of one or more chemical dispersing agents and / or surfactants are also added to achieve long-term stability. The term “dispersant” in the instant invention refers to a surfactant added to a medium to promote uniform suspension of extremely fine solid particles, often of colloidal size. In the lubricant industry the term “dispersant” is generally accepted to describe the long chain oil soluble or dispersible compounds which function to disperse the “cold sludge” formed in engines. The term “surfactanf” in the instant invention refers to any chemical compound that reduces surface tension of a liquid when dissolved into it, or reduces interfacial tension between two liquids or between a liquid and a solid. It is usually, but not exclusively, a long chain molecule comprised of two moieties: a hydrophilic moiety and a lipophilic moiety. The hydrophilic and lipophilic moieties refer to the segment in the molecule with affinity for water, and that with affinity for oil, respectively. These two terms, dispersant and surfactant, are mostly used interchangeably in the instant invention. The particle-containing fluid of the instant invention will have a viscosity index higher than the conventional fluid of the same type. The fluid can have any other chemical agents or other type particles added to it as well to impart other desired properties, e.g. friction reducing agents, antiwear or anticorrosion agents, detergents, antioxidants, dispersants, or thermal property booster. Furthermore, the term fluid in the instant invention is broadly defined to include pastes, gels, greases, and liquid crystalline phases in either organic or aqueous media, emulsions and microemulsions.

[0049] It is an object of the present invention to provide a uniform and stable dispersion where the thermal conductivity and heat transfer capability of the fluid is at least more than 20% improved compared to conventional mineral oil based automatic transmission fluids.

Problems solved by technology

While there have been various patents filed on lubricants containing graphite, e.g. U.S. Pat. No. 6,169,059, there are none which specifically rely on graphite to improve the viscosity index of the fluid.

Furthermore, there are none which teach specifically the use of nanometer-sized graphite with mean particle size much significantly less than 1000 nm in order to increase viscosity index.

While graphite-containing automotive engine oil was once commercialized (Arco graphite), the potential to use graphite as a viscosity modifying material in this oil was not realized.

On the other hand, the use of graphite in lubricants for recirculating systems was made unpopular, partly due to evidence that micron size graphite could “pile up” in restricted flow areas in concentrated contacts, thereby leading to lubricant starvation.

Previously, naturally formed “nano-graphites” have not been available in the marketplace at all.

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