Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Heavy metal or aluminum in an organic phosphorus compound...
Reexamination Certificate
2000-08-22
2003-01-07
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Heavy metal or aluminum in an organic phosphorus compound...
C508S378000, C508S380000, C508S391000, C508S408000
Reexamination Certificate
active
06503872
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to manual transmission lubricants which are thermally and oxidatively stable and are effective even at long drain intervals. More specifically, the invention relates to manual transmission lubricants with a metal thiophosphate, a phosphite and a basic salt of an acidic organic compound which provide thermal and oxidation protection to the manual transmission lubricants.
BACKGROUND OF THE INVENTION
Manual transmissions pose problems for lubricant formulators because of the configuration of the transmission and the metallurgy of the transmission components. The manual transmission uses spur gears which provided pressure and shearing in essentially linear force lines. In other words, the force of shear has only one directional component. This is in contrast to gears used for the driveline which are hypoid gears. In a hypoid gear, the gears mesh in such a way that the shearing force has two directional components'. A linear component and a second transverse component across the gear face. The level of extreme pressure protection needed for a manual transmission is lower than that needed for a hypoid gear assembly.
The manual transmission requires certain frictional properties from the lubricant to provide the ability of the manual transmission to perform gear changes. For the gear to be changed, the transmission must bring the drive shaft and the gear into position for meshing. The meshing is accomplished by a synchronizer when the synchronizing parts (plate to plate or ring to cone) are reduced to relative zero velocity. If these parts do not obtain zero relative velocity, then a phenomenon known as synchronizer clashing (sometimes referred to as crashing) occurs. Clashing of the synchronizer results when the dynamic coefficient of friction building between the engaging synchronizer parts (plate to plate or ring to cone) falls below a critical minimum value. Below this critical minimum value the synchronizer parts do not attain zero relative velocity and the lockup mechanism (e.g., spline camphers) contacts the rotating member (e.g., cone camphers) resulting in a loud noise (clashing/crashing).
The components of the manual transmission are typically bronze or brass. These metals are susceptible to corrosion and chemical attack from typical antiwear and extreme pressure agents which contain sulfur, particularly active sulfur. For instance, organic polysulfides which are typically used with lubricants for hypoid gears cause damage to the manual transmission synchronizer components.
Previously, manual transmission lubricants would use metal thiophosphonates or antiwear agents. These metal salts were typically barium salts. The accumulation of heavy metals, such as barium, in the environment has lead to the desire to eliminate the use of heavy metal salts in manual transmission lubricants.
It is desirable to provide lubricants which can provide the antiwear protection and viscosity protection for manual transmissions without harming the components of the transmission. It is desirable that the lubricants be free of barium salts.
SUMMARY OF THE INVENTION
This invention relates to a manual transmission lubricants comprising a major amount of an oil of lubricating viscosity, (A) at least one metal thiophosphate, (B) at least one phosphite, and (C) at least one basic salt of an acidic organic compound. In another embodiment, the manual transmission further comprises at least metal salt of a phenol. The lubricants provide the antiwear and extreme pressure protection needed for the manual transmission without harming the manual transmission components.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The term “hydrocarbyl” includes hydrocarbon as well as substantially hydrocarbon groups. Substantially hydrocarbon describes groups which contain heteroatom substituents that do not alter the predominantly hydrocarbon nature of the substituent. Examples of hydrocarbyl groups include the following:
(1) hydrocarbon substituents, i.e., aliphatic (e.g., alkyl or alkenyl) and alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, aromatic-, aliphatic- and alicyclic-substituted aromatic substituents and the like as well as cyclic substituents wherein the ring is completed through another portion of the molecule (that is, for example, any two indicated substituents may together form an alicyclic radical);
(2) substituted hydrocarbon substituents, i.e., those substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent; those skilled in the art will be aware of such groups (e.g., halo (especially chloro and fluoro), hydroxy, mercapto, nitro, nitroso, sulfoxy, etc.);
(3) heteroatom substituents, i.e., substituents which will, while having a predominantly hydrocarbon character within the context of this invention, contain an atom other than carbon present in a ring or chain otherwise composed of carbon atoms (e.g., alkoxy or alkylthio). Suitable heteroatoms will be apparent to those of ordinary skill in the art and include, for example, sulfur, oxygen, nitrogen and such substituents as, e.g. parietal, furyl, thienyl, imidazolyl, etc.
In general, no more than about 2, preferably no more than one heteroatom substituent will be present for every ten carbon atoms in the hydrocarbyl group. Typically, there will be no such heteroatom substituents in the hydrocarbyl group. Therefore, the hydrocarbyl group is purely hydrocarbon.
As described above the lubricating compositions comprise (A) at least one metal thiophosphate, (B) at least one hydrocarbyl phosphite, and (C) at least one overbased salt of an acidic organic compound. These lubricants provide thermal and oxidative protection as well at antiwear and extreme pressure protection to machinery.
Metal Thiophosphates
The manual transmission lubricants, and concentrates include at least one metal thiophosphate. Typically, the metal thiophosphate is present at a level from about 0.1% to about 5%, or from about 0.3% or to about 4%, or from about 0.5% to about 3%, or from 0.7% to about 2% by weight in the lubricating composition. Here and elsewhere in the specification and claims, the range and ratio limits may be combined.
The metal thiophosphates include mono and dithiophosphates as well as mixtures of mono and dithiophosphates. The mixtures may be formed in situ reaction or may be formed by blending a metal monothiophosphate with a metal dithiophosphate. The monothiophosphates or mixtures of mono and dithiophosphates may also be formed through reacting a metal dithiophosphate with steam. Alternatively, the monothiophosphate may be prepared by reacting one or more of the phosphites discussed herein with a sulfur or a sulfur compound.
In one embodiment, the metal thiophosphate is represented by the formula
wherein where X
1
and X
2
are independently oxygen or sulfur provided that one of these is sulfur, R3 and R4 are each independently hydrocarbyl groups containing from 3 to about 13 carbon atoms, preferably from 3 to about 8, M is a metal, and z is an integer equal to the valence of M. Preferably both X
1
and X
2
are sulfur.
The hydrocarbyl groups R
3
and R
4
in the thiophosphate may be alkyl, cycloalkyl, aralkyl or alkaryl groups. Illustrative alkyl groups include isopropyl, isobutyl, n-butyl, sec-butyl, the various amyl groups, n-hexyl, methylisobutyl carbinyl, heptyl, 2-ethylhexyl, diisobutyl, isooctyl, nonyl, behenyl, decyl, dodecyl, tridecyl, etc. Illustrative lower alkylphenyl groups include butylphenyl, amylphenyl, heptylphenyl, etc. Cycloalkyl groups likewise are useful and these include chiefly cyclohexyl and the lower alkylkyclohexyl radicals. Many substituted hydrocarbon groups may also be used, e.g., chloropentyl, di-chlorophenyl, and dichlorodecyl.
The thiophosphoric acids from which the metal salts useful in this invention are prepared are well known. Examples of dihydrocarbyl dithiophosphoric acids and metal salts, and processes for preparing such acids and salts are found in, for example, U.
Esposito Michael F.
Gilbert Teresan W.
Howard Jacqueline V.
The Lubrizol Corporation
Tritt William C.
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