Note: Descriptions are shown in the official language in which they were submitted.
035 1 5
218747=~
LUBRICATING COMPOSITION
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates generally to lubricating compositions and has
particular
reference to a lubricant composition containing a base lubricating oil and one
or more
molybdenum compounds and having a sodium content of not greater than 200 ppm,
and
also to a grease composition containing a base lubricating grease and one ar
more
molybdenum compounds and having a sodium content of not greater than 200 ppm.
In
particular, the grease composition is excellent in its frictional and wearing
characteristics and hence is suitably applicable to universal joints inclusive
of constant
velocity joints (CVJ) for automotive use, constant velocity gears and variable
speed
gears.
Description of the Related Art
In the present situation surrounding automotive vehicles, controls regarding
fuel
economy, exhaust gas emissions and the like have become stricter. Behind these
controls lie concerns about the environmental protection from global warming,
air
pollution, acid rain and the like as well as the protection of natural
resources, especially
out of concern about the exhaustion of limited petroleum deposits. In coping
with the
above trend, automotive fuel economy is most effective means available at
present. To
this end, it is of importance that the automobile itself be enhanced in
respect to body
218 7+
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weight, engine performance and the like, whereas improvements in engine oil in
regards to lowered viscosity, the addition of suitable friction regulating
additives, etc.
is also very important.
Automotive engine oils, however, must now be used under more severe
conditions than in the past. This is partly due to the impaired or adverse
frictional
conditions between engine oil and the engine, and elevated oil temperatures of
accompanying increases in engine performance output. Another cause is seen in
reduced quantities of engine oil used in order to reduce automobile weight.
Thus,
reductions in viscosity are a cause of engine wear or seizing.
A keen demand, therefore, has been voiced for the development of an additive
that can overcome those problems stemming from engine oils that have reduced
viscosities. An engine oil generally contains, to maintain desired
performance, various
additives such as friction regulating additives, antioxidants, cleaning
agents,
dispersants, extreme pressure agents, viscosity index improvers, pour point
depressants,
antiwear agents and the like. For instance, Japanese Patent Laid-Open No. 5-
508188
discloses a lubricating composition in which an overbasified alkali metal salt
such as of
a sodium, potassium, lithium or like metal of an acidic organic compound, a
dispersant,
dihydrocarbyl dithiophosphate and an antioxidant are incorporated to reduce
deterioration and prevent wear of the engine, and to present sludge formation.
However,
in order to solve the problems of wear and seizing noted above,
organomolybdenum
compounds are now being seen as essential additives.
Also, Japanese Patent Laid-Open No. 5-279686 suggests that the friction
2187~7"~
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characteristics of an engine oil can be improved, without wear resistance and
other
important qualities impaired, by formulation of an organomolybdenum compound,
a
fatty ester, a metallic cleaning agent (calcium sulfonate, magnesium
sulfonate, calcium
phenate and magnesium phenate), an ashless cleaning dispersant (benzylamine,
its
boron derivative, an imide of alkenyl succinate and its boron derivative) and
an anti-
wear agent [zinc dithiophosphate (ZDTP) and zinc dithiocarbamate (ZDTC)).
Constant velocity joints (CVJ) are being widely used for the rapidly growing
numbers of FF and 4WD vehicles or FR vihicles with indepedent suspension.
Although
CVJ's are used to transmit engine-power to the wheels, smooth power
transmission is
also required even in when the steering wheel has been turned left or right.
To this end,
CVJ's are generally a plunger type joint that is axially slidable on the
engine side and a
fixed type joint that is fixed axially on the wheel side. T'he plunger joint
involves
sliding resistance arising in the axial direction from its rolling and sliding
movements
as it reciprocates, thus leading to undesirable noise and vibration in an
automatic
transmission car, namely vibration during idling, rolling during startup and
acceleration
of the car, and beat frequency and entrapped noises from the car at certain
speeds.
Vibration damping is now a significant problem in keeping with the demand for
more
comfortable quiter, automotive vehicles. Consequently, focus has been centered
not
only on improving the joints themselves, but also on improving the grease
compositions
to be filled therein.
In view of the fact that the damped vibration of an automobile is correlated
to
the friction coefficient and hence conducive to saved fuel, a grease
composition has
2187~~?=
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been sought which could hold vibration to an absolute minimum.
Molybdenum disulfide, a sulfur-phosphorus type additive, a lead type additive
or the like has heretofore been employed as an additive to be incorporated in
a grease
composition for use with constant velocity joints. In recent years, however,
organomolybdenum compounds have been put to use in the production of a grease
exhibiting damped vibration that is a key quality in the art, i.e., a grease
with low
friction performance.
Japanese Patent Laid-Open No. 6-184583, for example, discloses a grease for
use with constant velocity joints and also a grease composition for such
joints wherein a
urea grease is formulated with molybdenum dithiophosphate, molybdenum
dithiocarbamate and ZDTC.
Engine oils, however, are usually composed of a wide variety of additives as
already discussed. In such oils, the additives tend to interact in some cases
with each
other and thus fail to impart their respective inherent properties.
Furthermore, when the prevailing trend toward improved mileage fuel savings
are taken into account, it becomes important to bring out the physical
performance of a
given organomolybdenum compound and retain it. Here, investigation is needed
to see
which of vrious selected additives would need to be formulated in such a way
that the
organomolybdenum compound could fully give rise to its performance.
In the case of the grease of Japanese Patent Laid-Open No. 6-184583 cited
above, it has been found that good friction reduction performance is not
necessarily
attainable.
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Generally, greases contain additives including oiliness improvers, antiwear
agents, extreme pressure agents, solid lubricants, pour point depressants,
viscosity
index improvers, tackifiers, structural stabilizers and the like as well as
special
additives including cleaning dispersants, defoamesr, antiseptics, dyes,
antistatic agents,
emulsifiers, demulsifiers and the like. These additives would in some
instances interact
with each other, and the same thing can be said of organomolybdenum compounds.
In order to meet the requirements for greases recently developed, it is import
for
organomolybdenum compound to exhibit its full physical performance.
Accordingly, a
formulation is required that eliminates the causes of bars to such
performance.
SUMMARY OF THE INVENTION
Accordingly, the present invention seeks to provide a lubricating composition
suitable for use as a lubricant composition or as a grease composition.
As a result of extensive research made in an effort to overcome the foregoing
deficiencies of the prior art, the present inventors have now found that
friction
reduction can be enhanced with good friction coefficient by lowering the
content of
alkali metal, particularly of sodium metal, in a lubricating composition. The
present
invention is based on such finding.
More specifically, the present invention in a first aspect provides a
lubricating
composition comprising a base oil and an organomolybdenum compound,
characterized
in that the composition has a sodium content of not greater than 200 ppm.
In a second aspect, the invention provides a lubricating composition
comprising
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a base oil and one or more organomolybdenum compounds selected from the group
consisting of sulfurized oxymolybdenum dithiocarbamates (MoDTC) represented by
Formula ( I )
R' S X' X' X' S R 3
\ II II / \1I i1 /
N-C-S-Mo Mo-S-C-N
/ \ / \
RZ X' R'
wherein R' to R~ are each a hydrocarbyl group, and X' is an oxygen or sulfur
atom;
and sulfurized oxymolybdenum dithiophosphates (MoDTP) represented by Formula
(2)
R50 S XZ X~ X2 S OR'
\ II II / \ II II /
P-S-Mo iVlo-S-I'
/ \ / \
R60 X2 OR$
wherein RS to Rg are each a hydrocarbyl group, and X'- is an oxygen or sulfur
atom,
characterized in that the composition has a sodium content of not greater than
200 ppm.
In a third aspect, the invention provides a lubricating composition comprising
a
base oil; one or more organomolybdenum compounds selected from the group
consisting of MoDTC represented by Formula ( 1 )
R' S X' X' X' S R 3
\ II II / \ II II
N-C-S-Mo Mo-S-C-N (1)
/ \ /
Rz X~ RQ
wherein R' to R~ and X' are as defined above;
2187~i=~
and MoDTP represented by Formula (2)
R50 S XZ XZ XZ S OR'
\ II II / \ II II /
P-S-Mo Mo-S-P C2)
/ \ / \
RsO X2 OR$
wherein RS to R8 and X'- are as defined above;
and one or more organozinc compounds selected from the group consisting of
ZDTP
represented by Formula (3)
R90 S
\ ~I
P-S Z n ~ a Z Il O (3)
R'°O 2
wherein a is 0 or 1/3, and R9 and R"' are each a hydrocarbyl group;
and ZDTC represented by Formula (4)
R" S
\ I~
N-C-S- Z n (~)
Rya
wherein R" and R''- are each a hydrocarbyl group,
characterized in that the composition has a sodium content of not greater than
200 ppm.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The lubricating composition according to the present invention contains said
organomolybdenum compound as an essential component. In order to ensure that
such
2187474
_g_
compound be able to exhibit its peculiar physical characteristics, the sodium
content in
the present composition should be not greater than 200 ppm, preferably below
100
ppm based on total amount of the composition. Also, the total content of an
alkali metal
including sodium in the composition should be set to be not beyond 200 ppm,
preferably below 100 ppm, more preferably less than 50 ppm. Further, alkali
metals
mentioned herein are those classed among Group I of the Periodic Table in
which
lithium, sodium, potassium, rubidium, cesium and francium are included.
In general, an alkali metal such as sodium becomes introduced into the
resultant
lubricating composition in cases where such alkali metal has not been
completely
removed after it was employed as a catalyst or starting material in separating
and
purifying or synthesizing the desired base lubricating oil. Another such case
is found
with respect to alkali metals or their salts not being completely eliminated
subsequent
to their use as a catalyst or starting material in the syntheses of various
additives as
commonly practiced frequently. Alkali metal compounds for use as starting
materials
and catalysts are exemplified by basic reagents such as alkali hydroxides,
alkali
sulfides, alkali hydrosulfides, alkali oxides, alkali alcoholates and the
like, and reducing
reagents such as alkali metals, alkali metal halides, alkali aluminum halides,
alkali
boron halides and the like.
In the case where the lubricating composition of the present invention is
applied
as a lubricating oil composition, additives such as for example an alkali
metal type
cleaning agent might often be added. However, the use of such particular
additive is not
preferable in the practice of the present invention. When the lubricating
composition is
2187~~7
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applied as a grease composition, there are instances wherein a base
lubricating oil is
incorporated with an alkali metal-containing thickener such as for example
sodium
soap, lithium soap, sodium terephthalamate or the like, instances wherein
sodium nitrite
or sodium sulfonate is added as a rust preventive, and instances wherein,
though rarely,
a cleaning dispersant is added. Thus, some alkali metal compounds are present
in the
resultant grease composition.
The organomolybdenum compounds that can be used in the present invention
include, in addition to MoDTC and MoDTP, reaction products of molybdic acid
with
amines, oxymolybdenum organophosphates, (sulfurized) oxymolybdenum xanthate,
reaction products of molybdenum with basic nitrogens, molybdenum-containing
dispersants and the like. MoDTC and MoDTP among these compounds are noticeably
affected by the sodium content in the lubricating composition.
According to the lubricating composition of the present invention, MoDTC is
represented by the compounds of Formula ( 1 ) indicated above, whereas MoDTP
is
represented by the compounds of Formula (2) shown above. In both formulae, R'
to R4
and RS to R8 are all hydrocarbyl groups that may be by nature saturated,
unsaturated,
chained, branched-chain or straight-chain. Such hydrocarbyl groups may be of
an
aliphatic, alicyclic or aromatic nature in which alkyl, alkenyl, alkylaryl,
cycloalkyl,
cycloalkenyl groups and the like are included.
Suitable alkyl groups are chosen from among methyl, ethyl, propyl, isopropyl,
butyl, isobutyl, tertiary butyl, pentyl, isopentyl, neopentyl, tertiary
pentyl, hexyl, heptyl,
octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl,
myristyl,
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palmityl, stearyl, eicosyl, docosyl, tetracosyl, triacontyl, 2-octyl-dodecyl,
2-
dodecylhexadecyl, 2-tetradecyloctadecyl, branched monomethyl-isostearyl groups
and
the like.
Suitable alkenyl groups are chosen from among vinyl, ally, propenyl,
isopropenyl, butenyl, isobutenyl, pentenyl, isopentenyl, hexenyl, heptenyl,
octenyl,
nonenyl, decenyl, undecenyl, dodecenyl, tetradecenyl, oleyl groups and the
like.
Suitable alkylaryl groups are chosen from among phenyl, tolyl, xylyl, cumenyl,
mesithyl, benzyl, phenethyl, styryl, cinnamyl, benzhydryl, trityl, ethylpheny,
propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl,
octylphenyl,
nonylphenyl, alpha-naphthyl, beta-naphthyl groups and the like.
Suitable cycloalkyl and cycloalkenyl groups are chosen from among
cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl, methylcyclohexyl,
methylcycloheptyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, methyl-
cyclopentenyl,
methylcyclohexenyl, methylcycloheptenyl groups and the like.
The substituent groups, R' to R8, may be the same or different; that is, R' to
R4
may be identical to, or different from RS to R8. Where the base oil is a base
oil for
lubricating oil, i.e., where the lubricating composition is a lubricating oil
composition,
an alkyl group of 8 to 13 carbon atoms is preferred as R' to R4 that are in
MoDTC and
an alkyl group of 6 to 13 carbon atoms as RS to R8 that are in MoDTP. The case
where
R' to R4 are different from each other, is preferable when the resultant
lubricating oil
composition is to have long drain or long service life..
When the base oil is a base grease, i.e., when the lubricating composition is
a
2187~~7~
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grease composition, an alkyl group with a carbon number of 1 to 15, preferably
of 2 to
13, more preferably of 2 to 8, is preferred as R' to R~ that are related to
MoDTC, while
an alkyl group with a carbon number of 1 to 1 S, preferably of 2 to 15, more
preferably
of 2 to 8, is preferred as RS to Rg that are related to MoDTP.
Each of the X' in Formula (1) and XZ in Formula (2) is an oxygen or sulfur
atom
and may be identical or different. Too small a number of oxygen atoms invites
insufficient lubricity, and too large a number of sulfur atoms makes the
finished
lubricating composition highly corrosive. Where severer lubricating conditions
in
particular are to be met, the atomic ratio of oxygen to sulfur is preferably
from 1 : 3 to 3
1.
In the lubricating composition according to the present invention, the
organomolybdenum compounds specified above can be used singly or in
combination.
Though not particularly restricted, the amount of such compound added is of
itself
limited to gain adequate lubricity and to prevent adverse sludge. For example,
when the
lubricating composition is a lubricating oil composition, the organomolybdenum
compound may be used in an amount of 0.005 to 0.2 percent by weight in terms
of
molybdenum, preferably of 0.01 to 0.1 percent by weight, based on a selected
base oil.
One or more members of the above organomolybdenum compounds can also be
used when the lubricating composition is a grease composition. Such a compound
if
added in too small an amount is ineffective for achieving sufficient friction
regulation,
and the compound if added in too large an amount produces no better results
with
uneconomical burdens. Thus, the organomolybdenum compound is added in an
amount
2181~:~7~+
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of 0.01 to 10 percent by weight, preferably of 0.05 to 5 percent by weight,
based on the
weight of the base grease.
MoDTC and MoDTP tend to contain a greater content of alkali metals,
particularly of sodium metals since they are synthesized usually with the use
of an
alkali metal compound, especially of sodium hydrosulfide. Thus, it is
preferred that
MoDTC and MoDTP for use in the lubricating composition of the present
invention be
derived for example by the production methods stated below.
MoDTC can preferably be produced by the method disclosed for instance in
Japanese Patent Laid-Open No. 56-12638. In this known method, molybdenum
trioxide
or molybdate salt is reacted with an alkali sulfide or alkali hydrosulfide,
followed by
addition of carbon disulfide and a secondary amine, and the reaction is
continued at an
appropriate temperature.
MoDTP can preferably be produced by the methods taught for instance in
Japanese Patent Laid-Open Nos. 61-87690 and 61-106587. Both methods are
contrived
to react an alkali sulfide or alkali hydrosulfide, followed by addition of
PzSs and a
secondary amine, and the reaction is continued at an appropriate temperature.
The lubricating composition of the present invention may be incorporated
further with either one or both of ZDTP and ZDTC as organozinc compounds. ZDTP
is
represented by the compounds of Formula (3) as previously shown, and R9 and
R'° in
that formula are each hydrocarbyl groups similar to R' to Rx. ZDTC is
represented by
the compounds of Formula (4) also indicated above, and R" and R''- are each
hydrocarbyl groups similar to R' to R8.
187L~%=~
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In the ZDTP of Formula (3), R9 and R'° are each hydrocarbyl groups and
may be
the same or different. Both of the substituent groups may be selected, like R'
to Rg,
from alkyl, alkenyl, alkylaryl groups and the like, among which an alkyl group
of 3 to
14 carbon atoms is particularly preferred.
In addition, among the R9 and R'° of one or more ZDTP compounds to
be used
more than 60% are preferably occupied by a primary alkyl group. The remaining
quantity of less than 40% may be a secondary alkyl and/or a tertiary alkyl
group.
In Formula (3), a is 0 or 1/3, and the resulting compound is termed a "neutral
ZnDTP" when a is zero and a "basic ZnDTP" when a is 1 /3.
ZDTP to be used in the present invention can be obtained by the method
disclosed for instance in Japanese Patent Laid-Open No. 48-37251. That is,
PzSs is
reacted with a given alcohol to form an alkyl-substituted dithio-phosphoric
acid which
is then neutralized or basified with zinc oxide, whereby a zinc salt is
prepared.
In the ZDTC of Formula (4), R" and R'-' are each hydrocarbyl groups and may
be the same or different. 'the two substituent groups are selected, like R' to
R8, from
alkyl, alkenyl, alkylaryl groups and the like, among which an alkyl group of 3
to 14
carbon atoms is particularly preferred.
One or more members of the above organozinc compounds can be used in the
lubricating composition of the present invention. When this composition is
applied as a
lubricating oil composition, no particular restriction is placed on the amount
of the
organozinc compound to be added. Too small an amount of such compound,
however,
results in an insufficient level of extreme pressure performance. Conversely,
too large
218~~7~
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an amount of the compound is responsible for impaired properties of extreme
pressure
performance and oxidation resistance. In regards to ZDTP, as it contains
phosphorus it
tends to contaminate catalysts employed inexhaust gas-treating systems. The
organozinc compound is therefore added in an amount of 0.005 to 2% by weight,
preferably of 0.01 to 1 % by weight, based on the weight of the base
lubricating oil
selected. The organozinc compound contributes to improvements in extreme
pressure
performance and oxidation resistance of the lubricant composition.
Also, when the lubricating composition is applied as a grease composition, the
amount of the organozinc compound to be used is not particularly restricted.
Needless
to say, if too little of such compound is added a sufficient level of extreme
pressure
performance cannot be effectively gain and if too much is added it will be
prone to poor
lubricity. The amount of the organozinc compound, therefore, is added in an
amount of
0.01 to 10% by weight, preferably of 1 to 5% by weight, based on the weight of
the
base lubricating grease selected. Further, the organozinc compound plays a
role in
improving the friction reduction perfomance of the grease composition.
The lubricating composition of the present invention is comprised of a base
oil,
one or more organomolybdenum compounds as specified above and, if desired, one
or
more organozinc compounds as previously stated. Here, the base oil may be a
base oil
for lubricating oil or a base grease.
The base oil for lubricating oil that can be used as the base oil may be
mineral
or synthetic oils. By the term mineral oil is meant such derived from cracking
of crude
oil and from subsequent distillation and refining. Included in the term
mineral oil is
2187~~7
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paraffinic oils, naphthenic oils and oils made available from hydrogenation
and solvent
refining thereof. The term synthetic oil denotes a chemically synthesized
lubricating oil
and includes poly-alpha-olefins, polyisobutylene (polybutenes), diesters,
polyol esters,
phosphate esters, silicate esters, polyalkylene glycols, polyphenylethers,
silicones,
fluorine compounds, alkyl benzenes and the like.
When the lubricating composition of the present invention is used as an engine
oil composition, it is preferred to select as the base, a mineral oil such as
hydrogenated
oils and hydrogenation refined oils, synthetic oils such as poly-alpha-
olefins, diesters,
polyol esters and the like.
The base greases that can be used as the base oil are composed of a base
lubricating oil and a thickener. Suitable examples of the thickener are soap
thickners
such as of aluminum, barium, calcium and the like, complex soap thickners such
as of
complex calcium, complex aluminum and the like, urea compounds such as
aromatic
diureas, aliphatic diureas, alicyclic diureas, triureas, tetraureas and the
like, organic
non-soap thickners such as terephthalates and the like, inorganic non-soap
thickeners
such as bentonites, silca aerogels and the like. Amongst the above exemplified
compounds, areas are particulary preferred, diureas more preferred and
aromatic
diureas most preferred. The thickeners are usually used alone, but two or more
members may be used in combination if desired. Though not restricted, the
thickener is
added usually in an amount of 3 to 40 percent by weight, preferably of 5 to 20
percent
by weight, based on the weight of the base grease.
The base lubricating oils that can be used in the base grease may be selected
218747
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from various base lubricating oils such as those of a mineral class, those of
a synthetic
class and blends thereof which have been commonly employed for greases. The
mineral
oil type base lubricating oils may include those resulting from refining of
crude oil by
means of solvent refining, hydrogenation refining or the like, or combinations
thereof.
The synthetic oil type base lubricating oils may include alpha-olefin polymers
such as
alpha-olefin oligomers of 3 to 12 carbon atoms, sebacates such as 2-ethylhexyl
sebacates and dioctyl sebacates, dialkyl diesters of 4 to 12 carbon atoms such
as
azelates and adipates, polyol esters such as trimethylolpropane, esters
resulting from
reaction of pentaerythritol and monobasic acids of 3 to 12 carbon atoms, alkyl
benzenes
having an alkyl group of 9 to 40 carbon atoms, polyglycols such as polyglycols
derived
from condensation of butyl alcohol with propylene oxides, phenylethers having
about 2
to 5 ether chains and about 3 to 6 phenyl groups, synthetic oils of a silicone
class and
synthetic oils of a fluorine class such as perfluoroalkyl polyethers. These
mineral and
synthetic oil type base lubricating oils may be used singly or in combination.
Though
selectively determinable with a view to meeting any prescribed properties, the
amount
of the base lubricating oil to be added is usually in the range of 60 to 97
percent by
weight, preferably of 80 to 95 percent by weight, based on the weight of the
base
grease.
It is preferable that said base grease containing the base lubricating oil and
thickener in the above stated proportion have a worked consistency of 175 to
400 at
250C, preferably of 205 to 310.
If the lubricating composition of the present invention is used as a
lubricating
218747=
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oil composition, numerous known additives may be incorporated which are chosen
from friction relaxants such as higher fatty acids, higher alcohols, amines,
esters and the
like, extreme pressure agents such as of a sulfur, chlorine, phosphorus or
organometallic type or the like, antioxidants such as phenols, amines and the
like,
cleaning agents such as sulfonates, phenates, carboxylates and the like of
neutral or
highly basic alkaline earth metals, dispersants such as imide succinates,
benzyl-amines
and the like, viscosity index improvers such as high-molecular
poly(meth)acrylates,
polyisobutylenes, polystyrenes, ethylene-propylene copolymers, styrene-
isobutylene
copolymers and the like, defoamers such as esters, silicones and the like,
rust
preventives, pour point depressants and molybdic acid amines. The amount of
each of
such additive to be added is within the range commonly accepted in the art.
Advantageously, the lubricating oil composition having the formulation as
stated above, can be used as a lubricant for internal combustion engines such
as engines
for vehicles inclusive of automobiles, 2-cycle engines, aircraft engines,
marine engines,
locomotive engines (irrespective of whether the combustion system is gasoline,
diesel,
gas or turbine), as an automatic transmission fluid, as a trans axle
lubricant, as a gear
lubricant and as a metal working lubricant.
If the lubricating composition of the present invention is used as a grease
composition, various known additives may be incorporated which are chosen from
friction relaxants such as higher fatty acids, higher alcohols, amines, esters
and the like,
extreme pressure agents such as of a sulfur, halogen, phosphorus or lead type
or the
like, antioxidants such as phenols, amines, sulfurs, seleniums and the like,
rust
2187~7~
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preventives such as long-chain carboxylic acids and their derivatives,
sulfonate salts,
amines, phosphate esters and their salts and the like, solid lubricants such
as graphites,
molybdenum disulfides, polyethylenes, polytetrafluoroethylenes (PTFE), boron
nitrides
and the like, pour point depressants, viscosity index improvers, tackifiers,
structural
stabilizers, cleaning dispersants, antiseptics, defoamers, colorants, cleaning
agents such
as of neutral or highly basic alkaline earth metals, antistatic agents,
emulsifiers,
demulsifiers and the like.
Also advantageously, the grease composition having the formulation as stated
above according to the present invention is suited for universal joints
inclusive of
constant velocity joints for automotive use, constant velocity gears and
variable speed
gears for automotive use as well as for various other fields of application.
In accordance with the invention, a novel lubricating oil composition is
provided which exhibits good performance of friction reduction.
In accordance with the invention, a novel grease composition is further
provided
which excels in frictional and wear characteristics.
EXAMPLES
The present invention is further described hereunder with reference to the
following examples.
The details of the components used in the inventive and comparative
lubricating
compositions are given below.
Base Oils
2187474
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Base oil for lubricating oil:
A high VI oil of a mineral class derived by subjecting a crude oil-induced
mineral oil to a hydrocracking process; kinematic viscosity: 4.1 cSt at 100
~C; VI: 126;
sodium content: below 10 ppm.
Base grease 1:
A base grease obtained by mixing a refined mineral oil of 15 cSt at 100 ~C
with
an aliphatic amine-based urea compound (a thickener), followed by uniform
dispersion
of the mixture for a worked consistency to reach 287 at 25L7C; sodium content:
below
ppm.
Base grease 2:
A base grease obtained by mixing a low-refined mineral oil of 16.7 cSt at
1 OO~C with a sodium soap (a thickener), followed by uniform dispersion of the
mixture
for a worked consistency to reach 271 at 250C.
Organomolybdenum Compounds
Mo compound 1:
MoDTC of R' to R4 = 2-ethylhexyl group, X' = S/O = 2.2 in Formula ( 1 );
sodium content: below 10 ppm.
Mo compound 2:
MoDTC of R' to R~ = 2-ethylhexyl group : isotridecyl group = 1 : l, X' = S/O =
2.2 in Formula (1); sodium content: below 10 ppm.
Mo compound 3:
MoDTP of RS to R8 = 2-ethylhexyl group, X'- = S/O = 2.2 in Formula (2);
21874?4
-20-
sodium content: below 10 ppm.
Mo compound 4:
MoDTC of R' to R4 = n-butyl group, X' = S/O = 2.2 in Formula ( 1 ); sodium
content: below 10 ppm.
Cleaning agent 1:
Calcium sulfonate; sodium content: below 10 ppm.
Cleaning agent 2:
Magnesium sulfonate; sodium content: below 10 ppm.
Cleaning agent 3:
Calcium salicylate; sodium content: below 10 ppm.
Cleaning agent 4:
Sodium phenate; sodium content: 10.5 percent by weight.
Organozinc Compounds
ZDTP:
R9 to R'° = 2-ethylhexyl group (primary alkyl group), neutral salt :
basic salt =
55 : 45 (in molar ratio) in Formula (3); sodium content: below 10 ppm.
ZDTC:
R" to R''- = 2-ethylhexyl group in Formula (4); sodium content: below 10 ppm.
Na Compound:
Sodium sulfite (rust preventive) (sodium content: 36.5%)
The sodium content of each of the above components was measured by an ICP
process after incineration. No alkali metals other than a sodium metal were
detected in
21874%4
-21-
the base oil for lubricating oil, base grease 1, Mo compounds 1 to 4, ZDTP,
ZDTC or
cleaning agents 1 to 3.
Example 1
The above prepared components were formulated in the proportions shown in
Tables 1 and 2 below, whereby inventive and comparative lubricant compositions
were
provided. In these tables, the numerical figures related to the Mo compounds
are
expressed by percent by weight in terms of molybdenum, and other figures are
expressed by percent by weight.
The resulting lubricant compositions were examined for their coefficients of
friction.
Friction Coefficient Measurement Test:
Friction coefficient measurements were earned out with an SRV measuring
apparatus and under the set of conditions indicated below.
Measurement Conditions:
Line Contact:
Testing was done in accordance with a cylinder-on-plate line contact test.
Namely, an upper cylinder (0 15 x 22 mm) was set to vertically positioned in
the
reciprocating direction on a plate (D 24 x 6.85 mm) and then allowed to
reciprocally
vibrate. After a lapse of 7 minutes, measurement was made of the friction
coefficient.
Both the cylinder and the plate were made of SUJ-2.
loading: 200 N
temperature: 80~C
2187'7
-22-
measuring time: 15 minutes
vibrational amplitude: 1 mm
cycle: 50 Hz
The test results are shown in Tables l and 2.
21 ~747~+
t~ O O M O~
N O ,-, .-.N O
O p
O N O ~p
O ~' O N O
p
O N N ~O
O O .-, ~ ~.j O
O
O O N O~
O .-, .-. CJ O
O O
l~ O O I~~ ~D
r; n
O O
O
~n O ~p in
- -, . ~D
t'1 O r O
O
N O ~ O
O ~ .-.r
O ~ O
C'1 O o0 tn
_U
O O
cCt O
O O C~-
O O
O
O N
M O O
O
I~ O Op
O ~; N O
N O O
O
-, ,~, O
'-, O O
U
N M N M ~ U
.b 'L~ -~."~' ~ ~., U
_ N N U _~ w
. , , ~ c~ cc5 ~ O
'''
O O O '~ '~ '~ ~ ~ ~ .O
O O O N U U .U
v ~ ~ ~ ~ z w
217474
-24-
Table 2
Comparative 1 2 3 4 5 6
Product
Mo compound 0.07 0,07
1
Mo compound 0.07 0.15
2
Mo compound 0.07
3
Cleaning agent 1.0 1.0 1.0 1.0 1.0 1.0
4
ZDTP 1.0
Na content (ppm)1,000 1,010 1,010 1,010 1,010 1,010
Friction coefficient0.12 0.12 0.12 0.15 0.13 0.12
I I I I I I
Example 2
The foregoing components were formulated in the proportions enumerated in
Tables 3 and 4 below, whereby inventive and comparative grease compositions
were
obtained. In these tables, all the numerical figures are expressed by percent
by weight
relative to the weight of a given base grease.
The resulting grease compositions were tested in respect of their frictional
properties under the set of conditions indicated below.
Friction Test:
Point Contact:
Testing was done in accordance with cylinder-on-plate point contact test.
Namely, an upper ball (0 10 mm) was disposed on a plate (C7 24 x 7.$5 mm) and
then
allowed to reciprocally vibrate. After a lapse of 2 hours, measurement was
made of the
2187~~7~
-25-
friction coefficient. Both the ball and the plate were made of SUJ-2.
loading: 200 N
temperature: SO~C
measuring time: 2 hours
vibrational amplitude: 1 mm
cycle: 50 Hz
Wear Resistance Test:
The coefficient of friction and the diameter of wear scar were measured with a
high-speed four-ball testing apparatus under the set of conditions indicated
below.
revolution: 1,800 rpm
loading: 40 kg
temperature: 40~C
time: 60 minutes
The compositons of tested grease and test results are shown in Tables 3 and 4
wherein all the numerical figures are expressed by percent by weight.
2187~~7~~
-26-
O ~n M ~O ~n
M ~ ~" 'ct
~
N O
O
"_" O ~n O ~O
_ M O ~ ~h v~
~
N O
O
.-. ~ O o0 O~ I
p ~.,.j.--.~ ~!7
O
O O ~ '~!' ~7
M
O
O
O O O 00 V1
r-. ~.~ ~ d' vo
O
.-r C
O
O N ~n v1
M M .~ MO d,
.-, O
M O
_U
O p ~ ~ O
M M M
O
O
O O O~ [~ V~
M M
O
O
~' O O .- v1 N
M M
O
O
~" ~ O O N M
M M ~ M
O O
U ,.~ y..,
b p ~ N M
p
z -~ ~ b ~ ~ ~
~ , ~,
0 0 o a
s~. s1 s~ s~ ~ ' ~ 3
~
v , . . ~ .-.
0 0 0 o Q., U o
0 0 0 0
'''~ ~ ~ ~ ~ N N
1 ~ ;~ ~. ~~
Table 4
I
Comparative 7 8 9 10 ; j 12 I 13
11
product ~ I
I
i
ase grease
No . 1 1 1 1 j 1. ~ 2
2
a
I
o compound .0 3.0 ~ 3.0
4 I a 3.0
I I
c
o compound 3.0 i
1
r
,
o compound .0 ;
2
k
Mo compound 3.U
3
E
ZDTP 3.01 3.0 3.0 3.0 3.0 3.0
ZDTC
! 3.0
Na compound 1.0 1.0 1.0 1.0 1.0 1.0
Na content 3, 3, 3, 500 3, 700 3, 700 21, 17,
500 600 000 000
( PPm ) i
SRV/friction 0.06 0.070 0.064 0.07 0.064 0.07 0.07
1 X
coefficient
High-speed
four-ball 0.63 0.75 0.65 0.73 0.74 0.75
0.65
test wear
scar dia (mm)
~ 1 ,
- z~ -
