Note: Descriptions are shown in the official language in which they were submitted.
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0 94/28095 PCT~US94/06002
LUBRICATING OIL COMPOSITION
BAu~KuuN~ OF THE LNv~LION
1. Field of the Invention
The present invention relates to a novel lubricating oil
composition, in particular, a lubricating oil composition having
i ~ved friction reducing pLo~eL~ies and wear reRistance and suitable
for use a~ a lubricating oil for internal combustion engines, auto-
matic tr~nRmiRsions, suspension and power steering wheels, particular-
ly as a lubricating oil for internal combustion engines.
2. Descri~tion of the Related Art
Lubricating oils are usually used for smoothing the operation
of internal combustion engines, driving mech~nis~ such as automatic
tr~n~ iRsions, suspensions and power stearings, and gears. Particu-
larly, engine oils are effective in lubricating mainly sliding parts
such a~ a piston ring and a cylinder liner, bearings of a crank shaft
or a connecting rod, and valve trains including cams and valve
lifters; in cooling the engine; in cle~ning and dispersing combustion
products; and in ~L~vellting rust formation and corrosion.
Thus, various functions are required of the engine oils and,
recently, even better function~ are being de -nde~ as the required
perfo -n~e and engine output hec~ - higher and higher and the opera-
tion conditions more severe. Under the~e circumstances, additiveR
such as a corrosion inhibitor, metallic detergent, ashless dispersant
and ant;nY;~nt are inco~oLated into the engine oil in order to
satisfy such requirements.
It is an important basic function of an engine oil to drive
the engine smoothly and to prevent wear and seizure under any given
condition. In the lubricated parts of an engine, a fluid lubrication
state is mostly realized. However, in the valve train and the top and
the bottom dead centers of a piston, a boundary lubrication state is
W 0 94/28095 ~ ~ 6 3 ~ ~ 6 2 - PCTrUS94/06002
apt to occur. In such a boundary lubrication, wear is usually pre-
vented by addition of zinc dithiophosphate (ZnDTP) or zinc dithiocar-
bamate (ZnDTC).
Since the energy 105s in the friction part5 in which the
lubricating oil participates is high in the engine, a friction
modifier (FM) is added to the lubricating oil in order to ini ize the
friction loss and improve the fuel consumption. As the friction
modifiers, extreme-pressure additive~ such a~ molyb~n~ compounds and
phosphoric esters and oiliness improvers such a5 fatty acid esters and
alkyl~ ines are usually used.
However, when a combination of the antiwear agent with the
friction modifier is used, the functions of both of them are not fully
exhibited because of their competitive adsorption onto the metal
~urface. More specifically, ZnDTP and ZnDTC protect the metal surface
from wear due to metal/metal contact by forming a protective film
thereon, while the friction modifier also forms a low-friction film by
the adsorption onto the metal surface, by the reaction therewith or by
the formation of a polymer on the metal surface to reduce the fric-
tion. Therefore, when both ZnDTP or ZnDTC and the friction mod$fier
are added to the lubricating oil, the adsorption of ZnDTP and ZnDTC is
reduced in amount by the competitive ad~orption onto the metal surface
to reduce the wear resistance or no sufficient friction-reducing
effect can be obtained even by the addition of the friction modifier.
On the other hand, an interaction beL~ ZnDTP or ZnDTC and
some detergent-dispersant is apt to occur to reduce the wear resis-
tance. Further, other additives such as the detergent-dispersant
might exert an influence on the effect of the friction modifier.
Thus, the selection of other addLtives such as the detergent-
dispersant and the concentration thereof must be taken into considera-
tion.
The present invention has been completed after investigations
made for the purpose of providing a lubricating oil composition having
i...~ oved friction reduction and antiwear ~L~e~Lies and suitable for
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-- 3
use a~ a lubricating oil for internal combu~tion engines, automatic
transmissions, suspension and power steering wheelL, particularly as a
lubricating oil for internal combustion engines.
SUMMARY OF THE 1 NVhN1I ON
After intensive investigations made for the purpose of
developing a lubricating oil composition having the above-described
excellent properties, the inventor~ have found that the above purpose
can be attained with a lubricating oil composition comprising zinc
dialkyl dithiophosphates, mainly one having seCo~ry alkyl group~, a
calcium sulfonate and a calcium salicylate as a metallic detergent and
sulfurized oxymolybdenum dithiocArbamate in specified proportions.
The present invention has been completed on the basis of this finding.
Specifically, the present invention provides a lubricating
oil composition comprising a base oil contAining (A) from 0.04 to
0.12% by weight (in terms of phosphorus), ba~ed on the whole compo~i-
tion, of a zinc dialkyl dithiophosphate con~Ai n; ng 50 to 100% by
weight (in terms of phosphorun), based on the total phosphorus con-
tent, of a zinc dialkyl dithiophosphate having secon~ry alkyl groups
and SO to O% by weight (in terms of ~hGs~horus), based on the total
phos~ho~s content, of a zinc dialkyl dithiophosphate having primary
alkyl groups, (B) 1.0 to 3.0~ by weight of a calcium sulfonate and 0.3
to 2.5% by weight of a calcium salicylate, and (C) 50 to 2,000 ppm (in
terms of molyb~r- ) of a ~ulfurized oxymolybdenum di~hiocArbamate
cont~i n i ng at least one hydrocarbon group having 8 to 23 carbon atoms,
wherein the oil composition is characterized by having a total ba~e
number of 2 to 13.
DETAILED DESCRIPTION OF THE INVhl~ L ION
The base oil usable as the major c~mpo~ent in the lubricating
oil composition of the present invention is not particularly limited.
Ba~e oils are those usually used in ordinary lubricating oils, such as
mineral oils and synthetic oils.
W O 94/28095 2 ~ 6 3 ~ ~ 6 PCTrUS91/06002 ~
The mineral oils include, for example, 60 neutral oil, lO0
neutral oil, 150 neutral oil, 300 neutral oil and 500 neutral oil
obtained by solvent refining or hydrotreating; and low pour point base
oil~ prepared by removing a wax from these bage oilg so as to improve
the low-temperature fluidity. They may be used either singly or in
the form of a mixture of two or more of them in a proper ratio.
The synthetic oils include, for example, poly-~-olefin
olj: rs, diesters, polyol esters and polyglycol e~ter~. They are
usable either singly or in the form of a mixture. They are also
u~able in the form of a mixture with the above-described mineral oil.
The mixing weight ratio of the synthetic oil to the mineral oil is,
for example, 80:20 to 20:80.
A suitable ba~e oil usable in the composition of the ~-a~ent
invention is one having a viscosity in the range of 3 to 20 cSt at
100C. Particularly preferred are hydrocracked products and/or wax
isomerized product cont~i n ing 3.0~ by weight or below of an aromatic
~ nt and having a ~ulfur content of 50 ppm or below and a
nitrogen content of 50 ppm or below.
In the compositLon of the present invention, the c .Lo~L
(A) is zinc dialkyl dithiuphos~hate (ZnDTP). ZnDTP comprise~ ZnDTP
having ~econ~ry alkyl groups and ZnDTP having primary alkyl groups in
such a ~ ~o Lion that the content of the phosphorus therein is 50 to
100% by weight and 50 to 0% by weight, respectively, ba~ed on the
total ~ho~ho,us content. By u~ing ~uch a ZnDTP, the ob~ect of the
present invention can be effectively attained.
The ZnDTP having ~eCon~ry alkyl groups include those of the
following general formula:
R10~
~P-S Zn [ 1 ]
R20 - 2
~ 0 94/28095 2 1 6 3 2 0 6 PCT~US94/0600~
The groups R1 and R2 in the general formula [1~ each represent a
seco~AAry alkyl group having 3 to 25 carbon atoms, such as propyl,
4 butyl, pentyl, hexyl, cyclohexyl, octyl, decyl, dodecyl, pentadecyl or
octadecyl group. They may be the same or different.
On the other hand, the ZnDTP having primary alkyl groups
include, for example, those of the following general formula:
R30 S
~-S Zn [ 2 ]
R 2
The groups R3 and R4 in the general formula [2 ] each represent a
primary alkyl group having 8 to 25 carbon atoms, such as octyl, decyl,
lauryl, myristyl, palmityl, stearyl or eicosyl group. They may be the
same or different.
In the composition of the pre~ent invention, the amount of
ZnDTP used as the c, ~_r~~t (A) must be 0.04 to 0.12% by weight (in
terms of phosphoru~) based on the whole compo~ition. When the amount
of phosphorus is below 0.05% by weight, the wear re~istance is insuf-
ficient and, when it is above 0.12% by weight, there is no further
significant h--~L~V. - t in wear resistance.
The composition of the present invention contains a calcium
sulfonate and a calcium salicylate as the metallic detergent (B). The
amount of the calcium sulfonate must be l.O to 3.0% by weight ba~ed on
the whole composition. When the amount of calcium sulfonate is below
1.0% by weight, the detergency i5 insufficient and when it is above
3.0~ by weight, the detergency effect is not further increased and the
ash content is increased unfavorably. On the other hand, the calciumsalicylate must be contained in an amount of 0.3 to 2.5~ by weight
ba3ed on the whole composition. When it is below 0.3~ by weight, no
sufficient friction reducing propertie~ can be obtained and, when it
exceeds 2.5~ by weight, the wear resistance is reduced and the ash
content is increased unfavorably.
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W O 94/28095 PCT~US94/06002
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The calcium salicylates are, for example, those of the
following general formula:
R5 ~ COO-Ca-OOC ~ [3]
In the general formula ~3], R5 represent5 a linear, branched or cyclLc
alkyl group having 8 to 23 carbon atoms, such as octyl, nonyl, decyl,
dodecyl, pentadecyl, octadecyl or eicosyl group.
A sulfurized oxymolybdenum dithiocarbamate (MoDTC) having a
hydrocarbon group having 8 to 23 carbon atoms is contained as the
component (C) in the composition of the present invention. MoDTC ha~
a ~tructure of the following general formula:
~ -~-S Mo S O ~4]
R - 2
The groups R6 and R7 in the above general formula ~4] each
represent a hydrocarbon group having 8 to 23 carbon atoms. The
hydrocarbon groups having 8 to 23 carbon atoms include linear and
branched alkyl and alkenyl groups having 8 to 23 carbon atoms, and
cycloalkyl, aryl alkylaryl and arylalkyl groups having 8 to 23 carbon
atoms. Examples of them include 2-ethyl-hexyl, n-octyl, nonyl, decyl,
lauryl, tridecyl, palmityl, stearyl, oleyl, eicosyl, butylphenyl and
nonylphenyl groups. R6 and R7 may be the same or different, and m and
n are positive integers such that the sum of them is 4.
In the composition of the present invention, MoD~C used as
the c~po~e~t (C) may be used either singly or in combination of two
or more of them. The amount of MoDTC is in the range of 50 to 2,000
ppm (in terms of molybdenum)~ preferably lOO to 1,OOO ppm, based on
the whole composition. When the amount of molybdenum is below 50 ppm,
no sufficient low-frictional properties can be obtained and when it is
~ 0 94/28095 2 ~ 6 ~ 2 0 6 PCTAU594/06002
above 2,000 ppm, the frictional properties are not further signifi-
cantly improved.
~, ,
The total base number of the composition of the present
invention must be 2 to 13, preferably 4 to 9. The base number is
determined according to JIS K 2501 (the unit of the total base number
being mgKOH/g).
The total base number of the composition of the present
invention can be ~uitably controlled with a calcium sulfonate having a
total base number (TBN) of 200 to 300 or a calcium sulfonate having a
total base number (TBN) of 10 to 100.
The lubricating oil composition of the present invention may
contain suitable additives usually incorporated into lubricating oils,
such as an ashless detergent-dispersant, viscosity index improver,
pour point depressant, antioxidant, rust inhibitor, corrosion
inhibitor, antifoaming agent and other antiwear agent and friction
modifier, so far as the object of the present invention is not di~-
turbed thereby.
The ashless detergent-dispersant include, for example,
3UCCin~ Y~ succinamideg~ benzylr in~3 and their boron derivatives
and esters. They are used in an amount of usually 0.5 to 7% by
weight, based on the whole composition.
The viscosity index i~ .overs include, for example, polymeth-
acrylates, polyisobutylenes, ethylene/propylene copolymers and hydro-
genated styrene/butadiene copolymers. They are used in an amount of
usually 0.5 to 35% by weight, based on the whole composition. The
antjoYi~nts include, for example, amine antioYi~nts such a~
alkylated diphenyl ~m; neS, phenyl-~-naphthylamines and alkylated
~-naphthyl~in~, and phenolic antioxidants such as 2,6-di-t-butyl-4-
methylphenol and 4,4'-methylenebis(2,6-di-t-butylphenol). They are
used in an amount of usually O.05 to 2% by weight, based on the whole
composition.
2~ ~32~6
WO 94l28095 PCT~US94/06002
-- 8 --
The rust inhibitors include, for example, alkenylsuccinic
acids and partial esters thereof. The corrosion inhibitors include,
for example, benzotriazole and benzimidazole. The antifoaming agents
include, for example, dimethylpolysiloxanes and polyacrylates. They
can be suitably incorporated into the composition.
The following Examples will further illustrate the present
invention and do not limit the invention.
Examples 1 to 8 and Com~arative Exam~les 1 to 10
The coefficient of friction and wear track diameter of the
lubricating oil composition were determined as follows:
(1) Coefficient of friction (~):
The efficient of friction was determined by the LFW-1 test
under the conditions of 270 rpm, 30 kgf, 120C and 10 minute~.
(2) Wear track diameter (mm):
The wear track diameter was dete~mine~ by the Shell four-ball
friction test under the conditions of 1,800 rpm, 20 kgf, 90C and 30
minutes.
Base oil 150N-1 (having viscosity at 100C of 5.7 mm2/fi~
aromatic component content of 4.1 wt%, sulfur content of 11.0 ppm and
nitrogen content of 89.0 ppm) or 150N-2 (having viscosity at 100C of
5.5 mm2/s, aromatic component content of 0.5 wt%, sulfur content of
O.S ppm and nitrogen content of 0.1 ppm) was used.
Each of the lubricating oil compositions listed in Table
was prepared from the base oil, and the coefficient of friction (~)
and the wear track diameter tmm) were determined. The results are
given in Tables 1-1 and 1-2.
~VO 94/28095 PCT/US91/06002
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W O 94/28095 2 t ~ 3 2 0 6 PCTrUS91/06002 ~
- 12 -
A~ can be ~een from a comparison of the data in Table 1-l vs.
Table 1-2, the oil composition according to the invention provides
significantly improved coefficient of function, wear track diameter or
both over the comparative composition set forth in Table 1-2.
The lubricating oil composit~on of the present invention has
excellent antiwear propertie~ and also excellent friction reducing
properties, and is suitable for u~e as a lubricating oil for, for
example, internal combustion engines, automatic transmi~sions, su~pen-
~ions and power steering wheels, particularly a~ a lubricating oil for
internal combu~tion engines.
