Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Inorganic compound
Reexamination Certificate
2002-05-02
2004-05-18
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Inorganic compound
C508S287000, C508S306000, C508S506000
Reexamination Certificate
active
06737387
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed, in part, to novel dispersed hydrated potassium borate compositions, as well as additive packages and finished oil compositions comprising the same. The dispersed hydrated potassium borate compositions of this invention exhibit low turbidity and the finished oil compositions comprising such dispersed hydrated potassium borate compositions exhibit improved wear protection under high temperature conditions.
REFERENCES
The following references are cited in this application as superscript numbers:
1
Peeler, U.S. Pat. No. 3,313,727, Alkali Metal Borate E P. Lubricants, issued Apr. 11, 1967
2
Adams, U.S. Pat. No. 3,912,643, Lubricant Containing Nelutralized Alkali Metal Borates, issued Oct. 14, 1975
3
Sims, U.S. Pat. No. 3,819,521, Lubricant Containing Dispersed Borate and a Polyol, issued Jun. 25, 1974
4
Adams, U.S. Pat. No. 3,853,772, Lubricant Containing Alkali Metal Borate Dispersed with a Mixture of Dispersants, issued Dec. 10, 1974
5
Adams, U.S. Pat. No. 3,997,454, Lubricant Containing Potassium Borate, issued Dec. 14, 1976
6
Adams, U.S. Pat. No. 4,089,790, Synergistic Combinations of Hydrated Potassium Borate, Antiwear Agents, and Organic Sulfide Antioxidants, issued May 16, 1978
7
Adams, U.S. Pat. No. 4,163,729, Synergistic Combinations of Hydrated Potassium Borate, Antiwear Agents, and Organic Sulfide Antioxidants, issued Aug. 7, 1979
8
Frost, U.S. Pat. No. 4,263,155, Lubricant Composition Containing an Alkali Metal Borate and Stabilizing Oil-Soluble Acid, issued Apr. 21, 1981
9
Frost, U.S. Pat. No. 4,401,580, Lubricant Composition Containing an Alkali Metal Borate and an Ester-Polyol Compound, issued Aug. 30, 1983
10
Frost, U.S. Pat. No. 4,472,288, Lubricant Composition Containing an Alkali Metal Borate and an Oil-Soluble Amine Salt of a Phosphorus Compound, issued Sep. 18, 1984
11
Clark, U.S. Pat. No.4,534,873, Automotive Friction Reducing Composition, issued Aug. 13, 1985
12
Brewster, U.S. Pat. No. 3,489,619, Heat Transfer and Quench Oil, issued Jan. 13, 1970
13
Salentine, U.S. Pat. No. 4,717,490, Synergistic Combination of Alkali Metal Borates, Sulfur Compounds, Phosphites and Neutralized Phosphate, issued Jan. 5, 1988
All of the above patents are herein incorporated by reference in their entirety to the same extent as if each individual patent was specifically and individually indicated to be incorporated by reference in its entirety.
STATE OF THE ART
High load conditions often occur in gear sets such as those used in automobile transmissions and differentials, pneumatic tools, gas compressors, centrifuges, high-pressure hydraulic systems, metal working and similar devices, as well as in many types of bearings. When employed in such environments, it is conventional to add an extreme-pressure (E.P.) agent to the lubricant composition and, in this regard, alkali metal borates are well known extreme-pressure agents for such compositions.
1-11, 13
E.P. agents are added to lubricants to prevent destructive metal-to-metal contact in the lubrication of moving surfaces. While under normal conditions termed “hydrodynamic”, a film of lubricant is maintained between the relatively moving surfaces governed by lubricant parameters, and principally viscosity. However, when load is increased, clearance between the surfaces is reduced, or when speeds of moving surfaces are such that the film of oil cannot be maintained, the condition of “boundary lubrication” is reached; governed largely by the parameters of the contacting surfaces. At still more severe conditions, significant destructive contact manifests itself in various forms such as wear and metal fatigue as measured by ridging and pitting. It is the role of E.P. additives to prevent this from happening. For the most part, E.P. agents have been oil soluble or easily dispersed as a stable dispersion in the oil, and largely have been organic compounds chemically reacted to contain sulfur, halogen (principally chlorine), phosphorous, carboxyl, or carboxylate salt groups which react with the metal surface under boundary lubrication conditions. Stable dispersions of hydrated metal borates have also been found to be effective as E.P. agents.
Gear sets have been subject to ever increasing demands including requirements for satisfactory performance at high temperatures, e.g., greater than 135° C. and preferably at least 163° C. In turn, this has placed an ever increasing requirement that the E.P. lubricant composition employed in such gear sets provide satisfactory wear and metal fatigue as measured by ridging and pitting requirements of the gear set when evaluated at such high temperatures.
In addition, because hydrated alkali metal borates are insoluble in lubricant oil media, it is necessary to incorporate the borate as a dispersion in the oil and homogenous dispersions are particularly desirable. The degree of formation of a homogenous dispersion can be correlated to the turbidity of the oil after addition of the hydrated alkali metal borate with higher turbidity correlating to less homogenous dispersions. In order to facilitate formation of such a homogenous dispersion, it is conventional to include a dispersant in such compositions. Examples of dispersants include lipophilic surface-active agents such as alkenyl succinimides or other nitrogen containing dispersants as well as alkenyl succinates.
1-4, 12
It is also conventional to employ the alkali metal borate at particle sizes of less than 1 micron in order to facilitate the formation of the homogenous dispersion.
11
Notwithstanding the use of such additives, lubricant compositions comprising such potassium borates can possess unacceptable turbidity.
In view of the above, lubricant compositions comprising a hydrated potassium borate and which possessed low turbidity and acceptable wear and fatigue properties as measured by pitting and ridging, especially when the gear set is operated at high temperature, would be particularly advantageous.
SUMMARY OF THE INVENTION
This invention is directed to the novel and unexpected discovery that reduced wear and fatigue as measured by ridging and pitting in gear sets can be achieved by the use of a lubricant composition comprising a dispersed hydrated potassium borate composition having a specific degree of dehydration.
In addition, this invention is directed to the novel and unexpected discovery that these compositions exhibit acceptable turbidity as evidenced by a turbidity value of less than 300 ntu.
Accordingly, in one of its composition aspects, this invention is directed to a dispersed hydrated potassium borate composition comprising a hydrated potassium borate, a dispersant, optionally a detergent, and an oil of lubricating viscosity wherein said dispersed hydrated potassium borate composition is characterized by a hydroxyl:boron ratio (OH:B) of from at least 1.2:1 to 2.2:1, a potassium to boron ratio of from about 1:2.75 to 1:3.25 and a turbidity value of less than 300 ntu.
In one preferred embodiment, the hydroxyl:boron ratio is from about 1.3:1 to 2.1:1; more preferably, from about 1.3:1 to 2.0:1; and even more preferably, from about 1.3:1 to 1.9:1.
In another preferred embodiment, the dispersed potassium borate compositions described herein have a turbidity of less than about 75 ntu, more preferably, less than about 60 ntu, and still more preferably, less than about 40 ntu.
In still another preferred embodiment, the dispersed hydrated potassium borate composition has a potassium to boron metal ratio of from about 1:2.9 to about 1:3.1 and more preferably about 1:3.
In yet another preferred embodiment, the dispersed hydrated potassium borate composition has an average particle size of less than about 0.6 microns and more preferably from about 0.10 to about 0.30 microns.
Optionally, the dispersed potassium borate compositions contain small amounts of a water-soluble oxo anion. Only from 0.001 moles to 0.11 moles of water soluble oxo anion should be present per mole of boron atom. This water-soluble oxo anion can include nitrate, sulfate, carbonate, phosphate, pyrophosph
Buitrago Juan A.
Harrison James J.
Nelson Kenneth D.
Caroli Claude J.
Chevron Oronite Company LLC
Foley Joseph P.
Howard Jacqueline V.
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