WO2012048201A2

WO2012048201A2 - Lubricants containing nanofibers

Info

Publication number: WO2012048201A2
Application number: PCT/US2011/055228
Authority: WO
Inventors: Brian Mayers; Joseph Mclellan; Rajeev Kumar; Matthew Stewart; Xinhua Li; Sandip Agarwal
Original assignee: Nano Terra Inc.
Priority date: 2010-10-08
Filing date: 2011-10-07
Publication date: 2012-04-12
Also published as: WO2012048201A3

Abstract

Disclosed is a composition comprising one or more lubricants and one or more nanofibers. Also disclosed is an article having a surface disposed thereon the composition of the invention. Also disclosed is a method of reducing friction between two surfaces, comprising disposing the composition of the invention on at least one of the two surfaces that come into contact.

Description

LUBRICANTS CONTAINING NANOFIBERS

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention is directed to nanoflber compositions suitable for use as lubricants and their use.

Background

[0002] A lubricant is a substance introduced between two moving surfaces to reduce the friction between them. Grease is a semisolid lubricant that possesses a high viscosity that is reduced upon application of shear forces.

[0003] There are a number of available thickeners for lubricants. Lithium-base greases are typically made from a fatty acid, usually 12-hydroxystearic acid, and a lithium base to produce a simple soap that acts as a grease thickener. Other additives such as graphite may be present to give the grease extreme pressure ("EP") properties. However, lithium based greases are not useful above 120°C. Moreover, lithium based grease may promote corrosion. Other known grease additives include WS₂, MoS₂, and hexagonal boron nitride. Other additives may serve multiple functions such as thickening and prevention of corrosion, improving thermal conductivity, or imparting electrical conductivity.

BRIEF SUMMARY OF THE INVENTION

[0004] The invention provides a composition comprising one or more lubricants and one or more nanofibers.

[0005] The invention also provides an article having a surface disposed thereon the composition of the present invention.

[0006] The invention also provides a method of reducing friction between two surfaces, comprising disposing the composition of the invention on at least one of the two surfaces that come into contact.

[0007] The added nanofibers may control rheology, thermal conductivity and electrical conductivity of the lubricant. DETAILED DESCRIPTION OF THE INVENTION

[0008] This specification discloses one or more embodiments that incorporate the features of this invention. The disclosed embodinient(s) merely exemplify the invention. The scope of the invention is not limited to the disclosed embodiment(s). The invention is defined by the claims appended hereto.

[0009] The embodiment(s) described, and references in the specification to "one embodiment", "an embodiment", "an example embodiment", etc., indicate that the embodiment(s) described can include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is understood that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0010] References to spatial descriptions (e.g., "above", "below", "up", "down", "top",

"bottom," etc.) made herein are for purposes of description and illustration only, and should be interpreted as non-limiting upon the compositions, methods, and products of any method of the present invention, which can be spatially arranged in any orientation or manner.

[0011] The invention provides compositions comprising one or more lubricants and one or more nanofibers.

[0012] By the term "nanofibers," is intended fibers having a circular cross section as well as fibers having a non-circular cross section. The circular fibers have an average diameter of less than 1 μηι and the non-circular fibers have an average of less than 1 μηι across the longest cross section. The fibers may be solid round fibers, hollow round fibers, multi-lobal solid fibers, hollow mulit-lobal fibers, crescent shaped fibers, square shaped fibers, and any combination thereof. In some embodiments, the fibers have an average fiber diameter of about 50 nm to about 800 nm, about 100 nm to about 700 nm, or about 200 nm to about 600 nm, or about 300 nm to about 400 nm. In some embodiments, about 60%, about 70%, about 80%, or about 90% of the fibers have a diameter of about 800 nm or less. In other embodiments, the fibers have a basis weight of 1 to 300 g/M², In other embodiments, the fibers have a basis weight of 5 to 100 g/M², In other embodiments, the fibers have a basis weight of about 9 g/M

[0013] in one embodiment, the nanofibers are meltblown polymer nanofibers, Such meltblown polymer nanofibers may be prepared by extruding molten fiber-forming polymer through the orifices of a die under pressure to form filaments. In another embodiment, the extruded polymer may be contacted with air or other fluid to attenuate the filaments into fibers. Selection of appropriate polymer flow rates, die operating temperatures, die orifice sizes, and attenuating airflow rates are chosen to give the desired structure and physical properties. Methods for preparing such meltblown polymer nanofibers are well known and taught, for example, in US 2008/0023888, US 2007/0075015, US 2006/0137318, US 2005/0176326, US 2010/0201041, US 20080136054, US 20090091056, US 6114017 and US 2010/0248575. In other embodiments, the nanofibers are prepared by the process of electrospinning or melt electrospinning. In some embodiments, the nanofibers are individual fibers. In other embodiments, the nanofibers are in the form of a non-woven fabric.

[0014] Generally, the process of making the nanofibers can be varied according to the values in the following Table.

Table. Process parameters for preparing nanofibers.

[0015] In one embodiment, the polymer is a thermoplastic polymer containing polyolefins such as polyethylene, polypropylene, polybutylene, poly(4-methyl-l- pentene), and cyclic olefin copolymers, and combinations of such polymers. Other polymers which may be used include polycarbonates, block copolymers such as styrene- butadiene-styrene and styrene-isoprene-styrene block copolymers, poly(styrene co-maleic anhydride), polymethacrylate, polyesters such as polyethylene terephthalate, polyamides, polyimides, polylactic acid, polyhydroxyalkanoate, polyvinyl alcohol, ethylene vinyl alcohol, polyacrylates, polyurethanes, polyaniline, polysulfone, polyether sulfone, cellulose acetate, polybenzimidazole, polyacrylonitrile, polyvinylchloride, polyvinylidine fluoride, polystyrene, polystyrene sulfonate, polyethylene glycol, cross-linked polyethylene glycol, copolymers thereof, and other polymers that will be familiar to those skilled in the art. In particular embodiments, the polymer is selected from polyethylene, polypropylene, polystyrene, polyvinylchloride, and combinations thereof. In some embodiments, the mean molecular weight of the polymer is about 100,000 Da to about 500,000 Da. The polymers can have a narrow molecular weight distribution of about 50,000 Da or less, about 25,000 Da or less, or about 10,000 Da or less.

Examples of lubricants for use in the preparation of the compositions of the invention include mineral oils, vegetable oils, and synthetic lubricants, optionally containing an emulsifying agent. A common emulsifying agent is a calcium, sodium or lithium salt of a fatty acid. Particular lubricants include petroleum fractions, silicones, polyolefins, esters, and fluorocarbons (e.g., fiuoropolymers containing ether linkages). Examples of synthetic lubricants include "polyol esters" and include compounds formed from monobasic fatty acids and polyhydric alcohols having a "neopentyl" structure. Representative alcohols useful for forming synthetic ester lubricants include neopentyl glycol, trimethylolpropane, pentaerythritol and dipentaerythritol. See U.S. Pat. 7,307,049. These alcohols are reacted to form esters with fatty acids generally having from about five to about twelve carbon atoms including: valeric, isopentanoic, hexanoic, heptanoic, octanoic, isooctanoic, 2-ethylhexanoic, pelargonic, isononanoic, decanoic and dodecanoic. The alcohols listed above generally have no beta-hydrogens and differ primarily in the number of hydroxyl groups available to form esters. See U.S. Pat. 7,307,049. Depending on the fatty acids selected, i.e., same or different and numbers of carbon atoms, the properties of the polyol ester formed can be "designed" to provide a particular viscosity range, pour point, flash point and volatility as required for particular applications. Lower molecular weight acids, e.g., valeric, isopentanoic, etc., generally are used when flowability at low temperatures is important. Properties such as oxidative stability and resistance to hydrolysis may be enhanced by incorporation of acids having branching. See U.S. Pat. 7,307,049. In many applications, mixtures of both higher and lower molecular weight acids provide desirable properties. U.S. Pat. No. 4,440,657 discloses many simple esters, diesters and polyol esters suitable for use as lubricants. Other polar liquids can also be used as lubricants, including water, alcohols, glycols, polyglycols, and ionic liquids.

[0017] It has been discovered that when certain oils are combined with meltblown polypropylene nanofibers, that the fibers absorb the oil and a semisolid or gel is produced.

[0018] Grease is a solid or semisolid lubricant. A semisolid lubricant or grease according to the present invention may be prepared by addition of nanofibers to a lubricant in an amount sufficient to result in a semisolid composition. Useful amounts of nanofibers are about 0.1 to 0.002 grams per gram of lubricant. In some embodiments the useful amount of nanofibers could be 0.0001 grams per gram of lubricant or less when used in combination with other additives.

[0019] The compositions of the present invention may also comprise other conventional lubricating composition components such as antioxidants including aryl amines, thickeners, metal passivators such as phosphate esters, fluoropolymers such as Teflon®, solid lubricants such as graphite and molybdenum disulfide, copper, and thickeners such as tar, graphite and mica.

[0020] The present invention also provides an article having a surface one which the composition of the present invention is disposed. The surface may be flat, round, cylindrical or other geometrical shape. In some embodiments, the surface has a constant roughness. In other embodiments, the surface has a varying roughness. In one embodiment, the surface is the surface of a ball bearing.

[0021] The present invention also provides a method of reducing friction between two surfaces, comprising disposing the composition of the present invention on at least one of the two surfaces that may come into contact.

[0022] The compositions of the invention are useful as lubricants and greases. In addition, the compositions are useful as sealants, protectants, thermal insulators and electrical insulators. For example the application of a thin layer of these compositions in slip connections, such as ground glass joints, can ensure that a proper seal is obtained. The compositions may be formulated such that when they are applied to certain surface they will provide a protecting layer. In some embodiments this protective layer protects the surface from contamination (e.g. water, dirt, grit, dust, oil, or air/gas), such contamination may lead to corrosion, increased wear, infection, deterioration, or oxidation of the surface to be protected. In some embodiments the compositions described herein can provide an electrically or thermal insulating barrier on a surface.

Examples

[0023J Example 1 : 0.5 grams non-woven fabric comprised of meltblown polypropylene nanofibers with basis weight of 8.64 grams per square meter, was combined with an excess of dodecane and allowed to absorb the liquid. After about 5 minutes the excess liquid dodecane was poured away and the mass of the wet fabric was found to be 20.3 grams, showing an absorbance capacity of >40x (wet to dry weight ratio).

[0024] Example 2: 1.0 gram of meltblown polypropylene nanofibers, as described in

Example 1, were combined with an 85 grams of Castrol oil (Castrol SP 100). The fibers rapidly absorbed all of the oil and formed a stiff continuous gel. The gel could be removed from its container without any liquid draining.

[0025] Example 3: 1.0 gram of meltblown nanofibers as described in Example 1 were mixed 100 grams of Castrol SP 100 and allowed to absorb the oil. The mixture formed a continuous gel within 5 min. The gel in this mixture was not as stiff as in Example 2, demonstrating that the nanofibers could be used to modify the viscosity of the oil. If the gel was removed from its container liquid oil would slowly drip from the gel.

[0026] Hypothetical Example 1. Polyaniline nanofibers will be fabricated by interfacial polymerization according to literature methods (see for example: Huang, J.; Kaner, R. B. J. AM. CHEM. SOC. 2004, 126, 851-855). The polyaniline nanofibers will be purified by filtration and rinsing and then added to the added to the oil in various quantities to control the rheology and impart electrical and thermal conductivity.

[0027] Hypothetical Example 2. Nanofibers or nanofiber fabrics will be incorporated in bearing seals to impart increased lubricity, lubricant retention, and texture at nano or micro scales in the region of the interface between the seal and shaft. The nanofibers or nanofiber fabric will, in some embodiments be embedded in the seal material; in other embodiments the nanofibers or nanofiber fabric will be applied to the surface of the seal [0028] Hypothetical Example 3. Bulk nanofibers or nanofiber fabrics will be incorporated in bearing seal configuration to impart increased lubricity, lubricant retention/extended lubricant release, and protection of the system from contamination. In some embodiments the bulk nanofiber materials are inserted between the bearing and seal and saturated with an appropriate lubricant.

[0029] It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way.

[0030] The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.

[0031] The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

[0032] All patents, patent applications, and publications cited herein are fully incorporated by reference.

Claims

WHAT IS CLAIMED IS:

1. A composition comprising one or more lubricants and one or more nanofibers.

2. The composition of claim 1, wherein said nanofibers are meltblown polymer nanofibers.

3. The lubricant composition of claim 2, wherein said meltblown polymer nanofibers comprise polypropylene, polyethylene, polyethylene terephthalate, polybutylene terepthalate, polysulfone, polyamides, polyacrylates, polystyrenes, and co-polymers thereof.

4. The composition of claim 1, wherein the nanofibers are electrospun.

5. The composition of claim 1, wherein the nanofibers are generated by chemical synthesis.

6. The composition of claim 1, wherein the fibers are produced using a rotary spinning process.

7. The composition of claim 1, wherein said lubricant is a mineral oil.

8. The composition of claim 1, wherein said lubricant is a synthetic oil.

9. The composition of claim 1, wherein said lubricant comprises a polar liquid.

10. An article having a surface disposed thereon the composition of claim 1.

11. A method of reducing friction between two surfaces, comprising disposing the composition of claim 1 on at least one of the two surfaces that come into contact.