Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Heterocyclic ring compound; a heterocyclic ring is one...
Reexamination Certificate
2000-09-22
2002-06-04
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Heterocyclic ring compound; a heterocyclic ring is one...
Reexamination Certificate
active
06399548
ABSTRACT:
BACKGROUND OF THE INVENTION
Fluid used in hydraulic pumps occasionally fail to protect copper bearing parts from wear when water contamination is present. This can result in loss of copper from the copper-containing parts.
Copper passivators or copper corrosion inhibitors are known in the art. U.S. Pat. No. 5,427,700, issued Jun. 27, 1995 to Stoffa, discloses functional fluids comprising at least one triglyceride, at least one detergent-inhibitor additive, and at least one viscosity modifying additive and a synthetic oil. The fluid may also contain a metal passivator, such as a thiadiazole compound (see col. 43, line 6 et seq.). European Patent Application No. 761 805 A2, published Mar. 12, 1997, discloses a lubricating/functional fluid composition which is said to exhibit in use improved antiwear and antifoaming properties. The improvements are said to result from use of 2,5-dimercapto-1,3,4-thiadiazole and derivatives thereof together with silicone and/or fluorosilicone antifoam agents. These thiadiazole compounds and derivatives are said to be effective corrosion inhibitors for silver, copper, silver alloys and similar metals. An example of such compounds is said to be Hitec 4313, available commercially from Ethyl Corporation. Canadian Patent Application No. 2,095,972 discloses lubricants formed from blends composed of a major amount of mineral oil in the range of 75N to 200N, and minor amounts of poly-alpha-olefin oligomer formed from 1 -alkene of 6 to 20 carbon atoms and having a kinematic viscosity in the range of 2 to 7 cSt at 100° C., and acrylic polymeric viscosity index improver. The lubricants may contain a copper corrosion inhibitor such as 2,5-dimercapto- 1,3,4-thiadiazole or derivatives thereof
It has been found that water contamination in a hydraulic fluid (e.g., water content at least 0.25 weight percent or at least 0.5 weight percent) can cause copper corrosion in, e.g., copper-containing bearing parts. If this corrosion occurs in, for example, a copper-containing (e.g., bronze) cylinder liner in a pump, it can lead to loss of flow in the pump.
It has now been discovered that when an oil-soluble dimercaptothiadiazole compound or derivative thereof is employed in functional fluids that contain water, copper containing metals in contact with the functional fluid are protected from copper loss. This discovery was quite surprising since other compounds known to be copper passivators or copper corrosion inhibitors do not perform nearly as well as the dimercaptothiadiazole compounds or derivatives thereof of this invention.
SUMMARY OF THE INVENTION
The present invention provides a method of protecting a copper-containing metal from loss of copper when in contact with a functional fluid composition containing water (e.g., at least 0.25 weight percent water or at least 0.5 weight percent water), said method comprising employing in said functional fluid an oil-soluble dimercaptothiadiazole compound or derivative thereof in an amount sufficient to protect against loss of copper.
The present invention also provides the above method of protecting a copper-containing metal wherein the oil-soluble dimercaptothiadiazole compound or derivative thereof has the formula:
wherein R
1
and R
2
are hydrogen or hydrocarbyl, n is 0 or 1, x is 1 or 2, y is 1 or 2 and z is 1 or 2. In a preferred embodiment, R
1
and R
2
are C
1
to C
30
alkyl groups.
Preferably, the oil-soluble dimercaptothiadiazole compound or derivative thereof has the formula:
wherein R
1
and R
2
are hydrogen or hydrocarbyl, n is 0 or 1, x is 1 or 2, y is 1 or 2 and z is 1 or 2. More preferably, R
1
and R
2
are each C
8
alkyl groups, n is 0, and x and y are each 2.
Further provided by the present invention is the above method for protecting a copper-containing metal wherein the amount of oil-soluble dimercaptothiadiazole compound or derivative thereof employed is from 0.01 to 0.2 weight percent based on the weight of the functional fluid.
Also provided by the present invention is the above-described method of protecting a copper-containing metal wherein the functional fluid further comprises:
A. 0.5 to 6 weight percent detergent
B. 0.5 to 3 weight percent antiwear additive
C. 0.1 to 1.5 weight percent friction modifier
D. 0 to 1 weight percent seal swell component
E. 5 to 200 ppm foam inhibitor
F. 0.5 to 10 weight percent viscosity index improver
G. balance base oil.
In a preferred embodiment, the functional fluid used in the above method is a hydraulic fluid, preferably a tractor hydraulic fluid.
The present invention also provides a functional fluid composition comprising a base oil, 0.01 to 0.2 weight percent of a dimercaptothiadiazole compound or derivative thereof, and water (e.g., at least 0.25 weight percent water or at least 0.5 weight percent water).
Further provided by the present invention is the above-described functional fluid wherein the oil-soluble dimercaptothiadiazole compound or derivative thereof has the formula:
wherein R
1
and R
2
are hydrogen or hydrocarbyl, n is 0 or 1, x is 1 or 2, y is 1 or 2 and z is 1 or 2. In a preferred embodiment, R
1
and R
2
are C
1
to C
30
alkyl groups.
Preferably, the dimercaptothiadiazole compound or derivative thereof has the formula:
wherein R
1
and R
2
are hydrogen or hydrocarbyl, n is 0 or 1, x is 1 or 2, y is 1 or 2 and z is 1 or 2. More preferably, R
1
and R
2
are each C
8
alkyl groups, n is 0, and x and y are each 2.
The present invention further provides a functional fluid wherein the functional fluid further comprises:
A. 0.5 to 6 weight percent detergent
B. 0.5 to 3 weight percent antiwear additive
C. 0.1 to 1.5 weight percent friction modifier
D. 0 to 1 weight percent seal swell component
E. 5 to 200 ppm foam inhibitor
F. 0.5 to 10 weight percent viscosity index improver
G. balance base oil.
In a preferred embodiment, the functional fluid of the present invention is a hydraulic fluid, preferably a tractor hydraulic fluid.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention relates to functional fluids. These are fluids that are comprised of a major amount of a base oil and various additives. The functional fluids are used in, e.g., hydraulic systems and transmissions, as opposed to being used in the crankcase of an internal combustion engine.
The oil-soluble dimercaptothiadiazole compounds or derivatives thereof used in the present invention have the following formulas:
where R
1
and R
2
are hydrogen or hydrocarbyl, n is 0 or 1, x is 1 or 2, y is 1 or 2 and z is 1 or 2. Preferably, R
1
and R
2
are C
1
to C
30
alkyl groups. A preferred dimercaptothiadiazole derivative is that having formula I above where R
1
and R
2
are each C
8
alkyl, n is 0, and x and y are each 2. This compound is available commercially from Ethyl Corporation as Hitec 4313.
It has been found that the dimercaptothiadiazole compound or derivative thereof is not effective in preventing copper loss when used in amounts below 0.01 weight percent.
Typically, it is used in the functional fluid in amounts from 0.01 to 0.2 weight percent, based on the weight percent of the finished (fully formulated) functional fluid, not taking into account the amount of water present in the functional fluid.
The functional fluids useful in the present invention may also contain other additives, including, but not limited to, detergents, antiwear additives, friction modifiers, seal swell components, foam inhibitors and/or viscosity index improvers. The balance of the hydraulic fluid is base oil. These other additives and base oils are well known in the art, and are disclosed in aforementioned U.S. Pat. No. 5,427,700, European Patent Application No. 761 805, and Canadian Patent Application No. 2,095,972, each of which is incorporated by reference herein.
Base Oils
The base oils used in the functional fluids of this invention may be mineral oil or synthetic oils of viscosity suitable for use in functional fluids. The oils ordinarily have a viscosity of about 1300 cSt 0° F. to 24 cSt at 210° F. (99° C.). The oils may be derived from synthetic or natural sources. Mi
Aoyagi Edward I.
Huron John E.
McLeod Kenneth Lee
Vartanian Paul F.
Chevron Oronite Company LLC
Howard Jacqueline V.
Stokley Linda A.
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