Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic phosphorus compound – wherein the phosphorus is...
Reexamination Certificate
2001-02-20
2004-06-29
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic phosphorus compound, wherein the phosphorus is...
C508S436000, C508S438000, C508S554000
Reexamination Certificate
active
06756346
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a lubricating oil composition having a low ash content or an ashless lubricating oil composition, and more specifically an antiwear type lubricating oil composition in which the ash content is reduced as low as possible, is excellent in thermal oxidation stability under severe conditions of a high temperature, is excellent in lubricating properties on various hydraulic apparatuses, and does not generate sludge even when a water content or a lubricating oil containing an overbasic alkaline earth metals additive, such as an engine oil, is incorporated.
BACKGROUND OF THE INVENTION
With a hydraulic apparatus being down-sized and used at a high speed and a high pressure, an oil is being used at a high temperature of 100° C. or higher instead of the conventional temperature range of from 50 to 70° C. Therefore, the conventional oils are not sufficient in thermal oxidation stability, and involve problems in that sludge is formed due to deterioration of the oil at a high pressure and a high temperature, the lubricating performance on a hydraulic pump is deteriorated, and friction between a seal and a rod of a hydraulic cylinder becomes large to generate rapid deterioration of the seal and abnormal vibration.
On the other hand, a conventional lubricating oil containing zinc dialkyldithiophosphate as an antiwear agent exhibits good antiwear performance on a vane pump using a sliding material mainly composed of steel. However, the zinc dialkyldithiophosphate tends to accelerate wear of a copper alloy on a piston pump using a sliding material composed of various copper alloys and steel. Thus, Denison Standard in U.S. recommends lowering the operation conditions when a zinc dialkyldithiophosphate type antiwear hydraulic oil is used in a piston pump.
With a hydraulic apparatus being advanced and precise, a filter having an extremely small pore diameter of from 3 to 10 micrometer is being used in the apparatus. Therefore, a hydraulic oil is required to have excellent filtering properties. However, the conventional oil tends to clog the filter in an early stage because sludge is formed by inclusion of a water content or an alkaline earth metal salt-containing lubricating oil, such as an engine oil, which reacts with an additive contained in the hydraulic oil. Therefore, development of a lubricating oil composition capable of solving all the problems is demanded.
A non-zinc type antiwear oil composition for hydraulic operation containing no zinc dialkyldithiophosphate has been known, and particularly an antiwear composition combining tricresyl phosphate or a triaryl phosphorothionate described in British Patent No 1,415,964 with an acidic phosphoric ester amine salt or triaryl phosphate has been known.
However, such conventional non-zinc type antiwear oil compositions for hydraulic operation involve problems in that friction between a seal and a rod of a hydraulic cylinder is large, the wear resistance becomes insufficient due to a rust preventing agent used in combination, and the filtering properties are extremely deteriorated by inclusion of a slight amount of an alkaline earth metal salt.
In addition to the above-described problems, there are increasing problems of using zinc compound including the zinc dialkyldithiophosphate from the standpoint of recent environmental protection and toxicity.
An object of the invention is to provide a lubricating oil composition in which the content of ashes such as zinc is reduced to as low as possible, that is excellent in thermal oxidation stability, lubricating property, water proofing property and filtering property.
SUMMARY OF THE INVENTION
As a result of investigation by the inventors to solve the problems associated with the conventional oils, it has been found that the problems are entirely solved by combining a specific antiwear agent and a specific rust preventing agent.
The invention relates to a lubricating oil composition comprising
(I) 100 parts by weight of a base oil for a lubricating oil;
(II) as an antiwear agent,
(i) (a) from 0.05 to 10 parts by weight of a phosphorothionate represented by formula (1), and (b) from 0.01 to 1.0 part by weight of an amine salt of a phosphorus compound which phosphorus compound is represented by formula (2a), and/or
(ii) from 0.05 to 10 parts by weight of a dithiophosphate represented by formula (3a);
(III) as a rust preventing agent,
from 0.01 to 1.0 part by weight of a polyalkylene polyamide obtained by reacting (a) a polyalkylene polyamine represented by formula (4a), and (b) a carboxylic acid having from 4 to 30 carbon atoms,
S═P(—O—R
1
)
3
(1)
(in the formula, R
1
represents an alkyl and/or an aryl group having from 1 to 30 carbon atoms),
X═P(—XR
2
)
2
XH (2a)
(in the formula, X represents a sulfur atom and/or an oxygen atom and R
2
represents an alkyl and/or aryl group having from 2 to 30 carbon atoms),
S═P(—O—R
6
)
2
(—S—A′) (3a)
(in the formula, R
6
represents an alkyl and/or aryl group having 1 to 30 carbon atoms and A′ represents a hydrocarbon group optionally further containing one or more oxygen atoms),
R
11
(R
12
)—N(R
10
—NR
13
)
m
H (4a)
(in the formula, R
10
represents an alkylene group having from 1 to 10 carbon atoms, R
11
, R
12
and R
13
each independently represent a hydrogen atom, an alkyl group having from 1 to 30 carbon atoms and/or a hydroxyalkyl group having from 1 to 30 carbon atoms and m is an integer from 1 to 10).
Further, the present invention relates to the use of lubricating compositions according to the present invention in hydraulic operation, in gears, in turbines and/or in bearings.
DETAILED DESCRIPTION OF THE INVENTION
The technical constitution of the invention is described in detail below. The base oil component constituting the lubricating oil composition of the invention is not particularly limited, if it contains petroleum base oils and/or synthetic hydrocarbon base oils. It preferably exhibits a kinematic viscosity of from 2 to 680 mm
2
/s (40° C.), preferably from 5 to 320 mm
2
/s (40° C.), and particularly preferably from 8 to 220 mm
2
/s (40° C.), a total sulfur content (% by weight) of from 0 to 1%, preferably from 0 to 0.3%, a total nitrogen content (% by weight) of from 0 to 100 ppm, preferably from 0 to 30 ppm, and an aniline point of from 80 to 130° C., preferably from 100 to 125° C.
The petroleum base oil for a lubricating oil is a sole substance or a mixture of a solvent refined base oil, a hydrogenation refined base oil and a high hydrogenation decomposed base oil. The high hydrogenation decomposed base oil is a base oil for a lubricating oil having a viscosity index of 130 or more (typically from 145 to 155) obtained by such a manner that slack wax separated by solvent dewaxing as a raw material is isomerized from a linear paraffin to a branched paraffin by hydrogenolysis (catalytic cracking) in the presence of a catalyst, or a base oil for a lubricating oil having a viscosity index of 130 or more (typically from 145 to 155) obtained by such a manner that hydrogen and carbon monoxide as raw materials obtained by a gasification process (partial oxidation) of natural gas (e.g., methane) is subjected to the Fischer-Tropsch polymerization to form a heavy linear paraffin, which is then subjected to isomerization by catalytic cracking in the same manner as above.
The synthetic hydrocarbon base oil may be an olefin oligomer obtained by sole polymerization or copolymerization of a monomer selected from a linear or branched olefin hydrocarbon having from 3 to 15 carbon atoms, preferably from 4 to 12 carbon atoms.
In the invention, the petroleum base oil and the synthetic hydrocarbon base oil may be used singly or in combination as a mixture thereof.
The phosphorothionate is represented by formula (1):
S═P(—O—R
1
)
3
(1)
(in the formula, R
1
represents an alkyl and/or an aryl group having from 1 to 30 carbon atoms, preferably R
1
represents an alkyl group having from 1 to 18 carbon atoms and/or an aryl
Baba Yoshiharu
Hanyuda Kiyoshi
McAvoy Ellen M.
Shell Oil Company
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