Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Elemental halogen or elemental phosphorus
Reexamination Certificate
2001-08-23
2002-11-05
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Elemental halogen or elemental phosphorus
C508S389000, C508S421000, C508S462000, C508S513000, C508S547000
Reexamination Certificate
active
06475961
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to lubricant compositions having antimicrobial properties and to methods for manufacturing and using lubricant compositions having antimicrobial properties. The lubricant compositions are particularly useful for lubricating food handling/processing machinery commonly used in the food processing industry.
BACKGROUND OF THE INVENTION
Oil-based lubricants are commonly used in the food processing industry in order to provide lubrication in gear boxes, pumps, hydraulic systems, agitators, grinders, etc. Although the lubricant is often provided inside a piece of machinery which is generally isolated from the exterior environment, food processing equipment is often cleaned using a high pressure water stream. Over time, water from cleaning operations tends to make its way into the machinery and contact the lubricant, forming a water and oil emulsion. Such water and oil emulsions become fertile grounds for growth of bacteria, yeast, and molds.
A food grade lubricant is available under the name No-Tox® from Bel-Ray Company, Inc. The lubricant incorporates an antimicrobial agent. Another lubricant containing a bacteriostatic agent is available under the name Lubristat® from Whitmore Mfg., Inc.
Lubricants containing antimicrobial agents are disclosed U.S. Pat. No. 3,826,746 to Schiek, et al. In general, Schiek, et al. describes lubricant compositions, such as, petroleum lubricant compositions, containing biocidal agents as microbial inhibitors. The biocidal agents include a substituted nitropyridine and an acid. In general, the concern is that bacteria may metabolize the hydrocarbons and result in the formation of deleterious metabolites.
SUMMARY OF THE INVENTION
A lubricant composition is provided by the invention. The lubricant composition includes a machinery lubricant and an antimicrobially effective amount of an antimicrobial agent exhibiting a partition coefficient between water and the machinery lubricant of between about 0.01 and about 1,000. The partition coefficient is the ratio of the weight fraction of the antimicrobial agent in water relative to the weight fraction of the antimicrobial agent in oil, wherein the ratio is determined at equilibrium. In addition, the lubricant composition exhibits at least a two log reduction of bacteria in water in about two weeks and/or at least a two log reduction of mold and yeast in water in about one month from a concentration of bacteria of between 10
5
and 10
6
CFU/ml (colony forming units/ml) and a mold and yeast concentration of between 10
5
and 10
6
CFU/ml.
A method for manufacturing a lubricant composition is provided by the invention. The method includes a step of mixing machinery lubricant and an antimicrobially effective amount of an antimicrobial agent exhibiting a partition coefficient between water and the machinery lubricant of about 0.01 and about 1,000.
A method for using a lubricant composition in machinery is provided by the invention. The method includes a step of introducing a lubricant composition containing a machinery lubricant and an effective amount of an antimicrobial agent, into machinery to provide lubrication properties. Exemplary machinery includes gear boxes, pumps, hydraulic systems, agitators, and grinders. The lubricant composition can be used in environments where microbial contamination is a concern. Exemplary environments include food processing equipment, pharmaceutical processing equipment and cosmetic processing equipment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention relates to a lubricant composition containing a machinery lubricant and an antimicrobially effective amount of an antimicrobial agent. Machinery lubricants are commonly available. Machinery lubricants which can be used according to the invention include petroleum derived lubricants. A preferred type of machinery lubricant which can be used to provide the lubricant composition according to the invention is a food machinery lubricant. In general, food machinery lubricants include those lubricants which can be used on food processing machinery in the food processing industry where there is a possibility of incidental contact with food. In general, such lubricants do not include large amounts of impurities harmful to humans. Lubricants which can be used on food processing equipment include FDA-approved food grade lubricants. Machinery lubricants can include oils and/or greases.
Various food grade oils and greases are commercially available. In general, types of food grade oils which can be used according to the invention include paraffinic oils, synthetic polyalpha olefin oils, aluminum complex grease, and mineral oil. Exemplary food machinery lubricants which can be used according to the invention are available from Vulcan Oil and Chemical Products of Cincinnati, Ohio under the names Ariadne™, Athena™, Bacchus™, Hercules™, Olympus™, Posseidon™, Zeus™, Prestige™, and Ep Grease™.
The antimicrobial agents which can be incorporated into the machinery lubricants to provide an antimicrobial effect include those antimicrobial agents which function to kill bacteria and/or yeast and mold which may exist in the machinery lubricant or become introduced into the machinery lubricant. Preferred antimicrobial agents include those which can be accepted for use on machinery in the food processing industry. In general, antimicrobial agents which are considered toxic to humans at levels needed to provide antimicrobial effect are not preferred antimicrobial agents for use in the food processing industry. Additional industries in which it is desirable to provide a machinery lubricant containing an antimicrobially effective amount of an antimicrobial agent include pharmaceutical processing and cosmetic processing.
The antimicrobial agents which can be incorporated into the machinery lubricants according to the invention are those exhibiting a distribution coefficient between water and the machinery lubricant which is sufficient to allow it to function as an antimicrobial agent over the life of the lubricant composition on a particular piece of machinery. The applicants discovered the desirability of providing an antimicrobial agent which exhibits solubility in both oil and water phases. As a result, when water is introduced into the lubricant composition, a portion of the antimicrobial agent provided in the oil phase becomes solubilized in the water phase. If the solubility of the antimicrobial agent in the oil phase is too high relative to its solubility in the water phase, a sufficient amount of antimicrobial agent to kill microbes in the water phase may not move into the water phase. In addition, if the antimicrobial agent is too water soluble relative to its oil solubility, too much antimicrobial agent may move into the water phase depleting the oil phase of antimicrobial agent and thereby reducing the longevity or life of the lubricant composition as an antimicrobial composition. That is, the lubricant composition may lose its effectiveness as an antimicrobial composition too quickly. A property which reflects the competitive solubility between the oil phase and the water phase can be referred to as the distribution coefficient. The distribution coefficient is generally expressed as a ratio of the weight fraction of the antimicrobial agent in water relative to the weight fraction of the antimicrobial agent in oil, wherein the ratio is determined at equilibrium. Preferably, the distribution coefficient for an antimicrobial agent in a lubricant composition is between about 0.01 and about 1,000. It is pointed out that a high distribution coefficient of about 1,000 may be considered acceptable if there is very little water contacting the lubricant composition and/or if the lubricant composition is replaced fairly frequently. A preferred distribution coefficient is between about 0.1 and about 100, more preferably between about 0.2 and about 50, and more preferably between about 0.5 and 20. In general, the distribution coefficient can be determined by varying the amounts of oil, water, and antimicr
Hei Robert D. P.
Lokkesmoe Keith D.
Schilling Joel James
Ecolab Inc.
McAvoy Ellen M.
Merchant & Gould P.C.
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