Environmentally friendly grease composition

Abstract

An environmentally friendly grease composition is provided comprising (a) a vegetable oil and (b) a cellulose fiber. The grease may further comprise glycerin; a rust inhibitor; and/or a fatty acid ester, lecithin, phosphatidyl choline, or a combination thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional application 60/542,189, filed on Feb. 5, 2004, which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable

SEQUENCE LISTING

Not applicable

FIELD OF THE INVENTION

The present invention relates to environmentally friendly grease compositions.

BACKGROUND OF THE INVENTION

The American Society for Testing and Materials (ASTM D288 standard definition of the terms relating to petroleum) defines a lubricating grease as a solid to semi-fluid product of dispersion comprising a thickening agent and a liquid lubricant. The liquid lubricant is often a non-polar liquid oil, and the thickening agent is often a polar paste, which is usually a soap comprised of a metal reacted or complexed with a fatty acid. Other ingredients imparting special properties may also be included. Typically, greases are employed in dynamic rather than static applications.

Lubricating greases are generally lost to the environment rather than being recycled or reused. The National Lubricating Grease Institute Grease Survey for 2000 estimates that 500,000 lbs/year of lubricating greases are discarded to the environment in the United States. This loss of lubricating greases is deleterious to the environment, in part because of the toxicity of the metals that comprise the soap. Although some metals used in the thickening agent can also be relatively environmentally benign (for example, if the metal is calcium or sodium), the alkalinity of the associated polar compounds is often lethal to beneficial microorganisms. Consequently, greases often do not pass environmental persistence testing and thus are not considered to be environmentally friendly.

The food industry is another area in which toxic greases are a problem. Hodson discloses the benefits of using non-toxic food-grade lubricants in food processing applications. D. Hodson, Food-grade Lubricants Reduce Contamination Threats for Food and Beverage Manufacturers, MACHINERY LUBRICATION January-February 2004, (24-27). If a plant uses a nonfood-grade lubricant, the U.S. Food and Drug Administration (FDA) mandates that a batch of food contaminated with the lubricant (i.e., at any measurable level greater than 0 ppm) must be discarded. On the other hand, if a certified food-grade lubricant is used, the FDA allows up to 10 ppm in the food as an acceptable contamination level.

Attempts to formulate environmentally friendly, non-toxic lubricating greases have been deficient. Grease formulations based on inorganic or mineral thickeners, such as bentonite clay or fumed silica, in place of the soap are generally less toxic than metal-based thickeners. Because of the relative hardness of the inorganic compound, however, the lubricating properties of the greases are limited.

Oostemam, for example, discloses a grease based on a synthetic ester oil, a lithium/calcium thickener and other biodegradable ingredients. Oosterman, P., Biodegradable Grease for All Bearing Applications, MACHINERY LUBRICATION, January-February 2004 (84-87). Although the study discloses acceptable lubrication performance characteristics in bearing applications, there is no specific disclosure regarding the biodegradability performance.

Accordingly, there is a need in the art for environmentally friendly, biodegradable and/or non-toxic lubricating greases that have good lubricating properties.

SUMMARY OF THE INVENTION

In one embodiment, the invention is directed to an environmentally friendly grease composition comprising a vegetable oil and a cellulose fiber.

In other embodiments the grease may further comprise glycerin; a rust inhibitor; and/or a fatty acid ester, lecithin, phosphatidyl choline, or a mixture thereof.

In another embodiment, the grease composition comprises canola oil in an amount of from about 70 weight % to about 80 weight %, cellulose fiber in an amount of from about 5 weight % to about 10 weight %, sorbitan mono-oleate in an amount of from about 7 weight % to about 13 weight %, glycerin in an amount of from about 5 weight % to about 10 weight %, and a rust inhibitor in an amount of from about 0.1 weight % to about 0.3 weight %.

BRIEF DESCRIPTION OF THE DRAWINGS

Not applicable

DETAILED DESCRIPTION OF THE INVENTION

All publications and patent applications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed inventions, or that any publication specifically or implicitly referenced is prior art.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described.

In one embodiment, the invention is directed to an environmentally friendly grease composition comprising a vegetable oil and a cellulose fiber. The grease can be used, for example, as a lubricant.

The first component of the present grease composition is a vegetable oil. Vegetable oil, as used herein, means a substance derived from a plant, generally from the seed or nut of a plant, comprising glycerides of fatty acids. Examples of vegetable oils used in the greases of the invention, include, but are not limited to, canola, soy, linseed, tung, corn, safflower, sunflower, peanut, palm, palm kernel, coconut, camelina, oiticica, and cottonseed oils. In one embodiment of the invention, the vegetable oil comprises canola oil.

The vegetable oil used in the grease of the present invention can also be vegetable oil that has been heat-bodied, telemerized, hydrogenated, partially hydrogenated, or trans-esterified. As used herein, heat-bodied oils are fatty acids exposed to temperatures high enough to cause them to form cyclic ring structures, typically with extended legs of hydrocarbon chains. As used herein, telemerized oils are vegetable oils, wherein a dicarboxylic acid links two of the hydroxyl positions of a triglyceride. As used herein, hydrogenated oils are oils which have been exposed to hydrogen gas in order to saturate or partially saturate the carbon atoms. As used herein, trans-esterified oils are oils wherein the unsaturated hydrocarbon side chains of the fatty acids are changed from the cis configuration to the trans configuration. This can be accomplished via a hydrogenation/dehydrogenation reaction.

The vegetable oils of the invention are generally present in the grease in an amount of from about 40 weight % to about 95 weight %.

In one embodiment of the invention, the vegetable oil is present in the grease in an amount of from about 60 weight % to about 90 weight %.

In one embodiment of the invention, the vegetable oil is present in the grease in an amount of from about 70 weight % to about 80 weight %.

Without wishing to be bound by theory, it is believed that vegetable oil acts as an environmentally friendly, non-toxic lubricating component in the grease.

The second component of the present grease composition is a cellulose fiber. Cellulose fiber, as used herein, means a fiber, i.e., a solid characterized by a relatively high tenacity and an extremely high ratio of length to diameter (on the order of several hundred to one), of a polysaccharide comprising anhydroglucose units joined by an oxygen linkage that form molecular chains that are essentially linear. Examples of sources from which cellulose can be obtained include, but are not limited to, cotton, wood pulp, flax, and kenaf.

The cellulose fibers of the invention are generally present in the grease in an amount of from about 1 weight % to about 20 weight %.

In one embodiment of the invention, the cellulose fibers are present in an amount of from about 2 weight % to about 15 weight %.

In one embodiment of the invention, the cellulose fibers are present in an amount of from about 5 weight % to about 10 weight %.

Without wishing to be bound by theory, it is believed that the cellulose fiber acts as an environmentally friendly, non-toxic thickening agent in the grease.

In one embodiment, the grease composition of the present invention comprises glycerin.

Glycerin is generally present in the grease in an amount of up to about 15 weight %.

In one embodiment of the invention, glycerin is used in the grease in an amount of about 12 weight %.

In one embodiment of the invention, glycerin is used in an amount of from about 5 weight % to about 10 weight %.

Without wishing to be bound by theory, it is believed that glycerin acts as an environmentally friendly, non-toxic thickening agent additive, in part assisting with emulsification.

In one embodiment, the grease composition of the present invention comprises a fatty acid ester, lecithin, phosphatidyl choline, or a combination thereof.

A fatty acid ester, as used herein, means an ester formed by reacting a fatty acid with an alcohol. Suitable fatty acids include, but are not limited to, caproic acid, lauric acid, myristic acid, palmitic, stearic, oleaic, linoleic, and linolenic acid. Suitable alcohols include, but are not limited to, mono and polyhydroxy substituted hydrocarbons having between 1 and 20 carbon atoms, preferably polyhydroxy hydrocarbons having between 5 and 12 carbons, for example, sorbitol. Examples of fatty acid esters used in the greases of the invention, include, but are not limited to, sorbiatan monolaurate, sorbitan monostearate, and sorbitan mono-oleate. In one embodiment, the preferred fatty acid comprises sorbitan mono-oleate.

Phosphatidyl choline, as used herein, has the formula
wherein —OC(O)R is derived from a fatty acid, and wherein R and R₁ are saturated or unsaturated hydrocarbons, preferably with 6-22 carbon atoms.

Lecithin, as used herein, means a mixture of neutral and polar lipids and phosphatidyl choline molecules having a variety of —OC(O)R groups.

The fatty acid ester, lecithin, or mixture thereof is generally present in the grease in an amount of from about 1 weight % to about 30 weight %. In a preferred embodiment, the fatty acid ester, lecithin, or mixture thereof is present in an amount of from 2 weight % to about 20 weight %. In a more preferred embodiment, the fatty acid ester, lecithin, or mixture thereof is present in an amount of from about 7 weight % to about 13 weight %.

Without wishing to be bound by theory, it is believed that the fatty acid ester, lecithin, phosphatidyl choline, or a combination thereof acts as a coupling agent between the non-polar liquid and the polar fiber surface, as well as a lubrication aid to the grease. Again, without wishing to be bound by theory, it is believed that the molecules of the above-listed compounds have both a polar and a non-polar component (e.g., in sorbitan mono-oleate, the polar component is the alcohol portion of the molecule, and the non-polar component is the hydrocarbon chain), and this characteristic aids in maintaining the grease structure.

In one embodiment, the grease composition of the invention comprises a rust inhibitor. The rust-inhibitor may be selected from, for example, neutral or overbased petroleum or synthetic oil metal sulfonates such as neutral or overbased calcium sulfonates, neutral or overbased barium sulfonates, neutral or overbased zinc sulfonates; metal soaps; partially esterified polyhydric alcohols such as sorbitan fatty acid esters; amines; phosphoric acid; or linear or branched alcohol esters of phosphates. In one embodiment of the invention the rust inhibitor is Maxhib OS-4300, a proprietary mixture of phosphate esters, commercially available from Rütgers Organics Corporation of Piedmont, S.C.

The rust additive is generally present in the grease of the present invention in an amount less than about 2 weight %.

In one embodiment, the rust additive is present in the grease of the present invention in an amount less than about 0.5 weight %.

In one embodiment, the rust additive is present in the grease of the present invention in an amount of from about 0.1 weight % to about 0.3 weight %.

In one embodiment, the grease composition of the invention comprises an extreme pressure additive. The extreme pressure additive can be a sulfurized oil or a sulfurized fat.

The extreme pressure additive is generally present in the grease compositions of the invention in an amount from about 0.05 weight % to about 5 weight %.

In one embodiment, the extreme pressure additive is present in an amount of from about 0.1 weight % to about 2 weight %.

The viscosities of both the vegetable oil in the grease and the grease itself are important parameters used to characterize the grease's performance. The vegetable oils used in the greases of the present invention have viscosities of from about 30 centiStokes (cSt) to about 50 centiStokes (cSt) at 40° C.

In one embodiment, the vegetable oils of the present invention have viscosities of from about 35 cSt to about 44 cSt at 40° C.

The grease of the present invention generally has a viscosity in the range of from about 400 cSt at 40° C. to about 500 cSt at 40° C.

In one embodiment, the grease of the present invention has a viscosity of from about 450 cSt at 40° C. to about 470 cSt at 40° C.

As used herein, the drop point of grease is the temperature at which the grease passes from a semi-solid to a liquid state. Generally, the drop point is measured using ASTM D-566.

Biodegradability, as used herein means a measure of how quickly and completely the greases of the present invention break down in the environment. The grease compositions of the present invention are environmentally friendly, i.e., they break down quickly and completely in the environment. Tests used to test the biodegradability of the greases of the present invention, include, but are not limited to the OECD 301B test or CEC-L33-A-93 test. According to the 301B test developed by OECD (Organization for Economic Cooperation and Development), a compound is judged to be biodegradable when the amount of CO₂ gas generated by bacterial decomposition (test period: 28 days) accounts for 60% or higher of the total theoretical amount of CO₂ gas calculated based upon the amount of carbon in a sample. The test of CEC-L33-A-93 was developed by CEC (Coordinating European Council), and is generally used for testing the biodegradability of engine oils for two stroke cycle outboard motors. This test is also widely used to evaluated the biodegradability of water-insoluble lubricating oils such as hydraulic oils and grease. In this test, a sample and a source of microorganisms are cultured with shaking at 25° C. for 21 days and are then extracted with carbon tetrachloride. The infrared absorption spectrum of the extract is determined and the absorption intensity due to the methylene groups in the sample is quantified to calculate the biodegradability rate (%) of the sample. Those giving 67% or higher biodegradability rates are acceptable in this test.

In one embodiment, the greases of the present invention are manufactured by first mixing the vegetable oil with a fatty acid ester, lecithin, phosphatidyl choline, or a combination thereof and a rust inhibitor until the components are dissolved. Then, the cellulose fiber and glycerol are added to the dissolved mixture until the desired viscosity and drop point are reached.

The grease compositions of the present invention exhibit excellent lubrication characteristics, and are biodegradable and/or less toxic than conventional greases.

EXAMPLES

The grease compositions of the invention are illustrated by the following examples, which are merely indicative of the nature of the present invention, and should not be construed as limiting the scope of the invention, nor of the appended claims, in any manner.

Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the following illustrative examples, make and utilize the compounds of the present invention and practice the claimed methods. The following working examples therefore, specifically point out the preferred embodiments of the present invention, and are not to be construed as limiting in any way the remainder of the disclosure.

Example 1

A grease formulation composed of about 74 weight % canola oil, about 7 weight % cellulose fiber, about 9.8 weight % sorbitan mono-oleate, about 0.2 weight % Maxhib OS-4300 rust inhibitor, and about 7 weight % glycerin was prepared for testing. Two tests were performed to evaluate the lubricity and stability characteristics of the grease. The two tests were D2266: Four Ball Wear Properties and D942: Oxidation Stability of Lubricating Grease. The tests results were as follows:

ASTM D2266: Four Ball Wear Properties:
	Scar diameter:	0.6	mm
	Time:	1	hour
	Load:	40	Kgf
ASTM D942: Oxidation Stability of Lubricating Grease
	Pressure Drop:	39.36	psi
	Test Duration:	100	hours
	Test Temperature:	99°	C.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom as modifications will be obvious to those skilled in the art.

While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as follows in the scope of the appended claims.

All publications cited herein are incorporated herein by reference for the purpose of disclosing and describing specific aspects of the invention for which the publication is cited.

Claims

1. A grease composition comprising (a) a vegetable oil and (b) a cellulose fiber.

2. The grease composition of claim 1, wherein the vegetable oil is present in an amount of from about 60 weight % to about 90 weight %, and the cellulose fiber is present in an amount of from about 2 weight % to about 15 weight %.

3. The grease composition of claim 1, further comprising glycerin.

4. The grease composition of claim 3, wherein the glycerin is present in an amount up to about 12 weight %.

5. The grease composition of claim 1, further comprising a fatty acid ester, lecithin, phosphatidyl choline, or a combination thereof.

6. The grease composition of claim 5, wherein the fatty acid ester, lecithin, phosphatidyl choline, or combination thereof is present in an amount of from about 2 weight % to about 20 weight %.

7. The grease composition of claim 6, wherein the fatty acid ester is sorbitan mono-oleate.

8. The grease composition of claim 1, further comprising a rust inhibitor.

9. The grease composition of claim 8, wherein the rust inhibitor is present in an amount up to about 0.5 weight %.

10. The grease composition of claim 1, further comprising an extreme pressure additive.

11. The grease composition of claim 10, wherein the extreme pressure additive comprising sulfur is present in an amount of from about 0.1 weight % to about 2 weight %.

12. The grease composition of claim 1, wherein the vegetable oil is selected from the group consisting of canola, soy, linseed, tung, corn, safflower, sunflower, peanut, palm, palm kernel, coconut, and camelina oils.

13. The grease composition of claim 12, wherein the vegetable oil is canola oil.

14. The grease composition of claim 1, wherein the cellulose is derived from wood pulp, cotton, kenaf, flax, or a mixture thereof.

15. The grease composition of claim 1, wherein the vegetable oil has a viscosity of from about 35 cSt at 40° C. to about 44 cSt at 40° C.

16. The grease composition of claim 1, wherein the grease has a viscosity of from about 450 cSt at 40° C. to about 470 cSt at 40° C.

17. A grease composition comprising canola oil, cellulose fiber, sorbitan mono-oleaste, glycerin, and a rust inhibitor.

18. The grease composition of claim 17, wherein the canola oil is present in an amount of from about 70 weight % to about 80 weight %, the cellulose fiber is present in an amount of from about 5 weight % to about 10 weight %, the sorbitan mono-oleate is present in an amount of from about 7 weight % to about 13 weight %, the glycerin is present in an amount of from about 5 weight % to about 10 weight %, and the rust inhibitor is present in an amount of from about 0.1 weight % to about 0.3 weight %.