Note: Descriptions are shown in the official language in which they were submitted.
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LUBRICATING OIL COMPOSITION
BACKGROUND OF THE ~Nvh.~.lON
1. Field of the Invention
The present invention relates to a lubricating oil composi-
tion, in particular, a lubricating oil composition having ; -ovæd
frictLon reducing properties and suitable for use as a lubricating oil
for internal combustion engines, automatic tr~n i~sions, suspensions
and power steering wheels, particularly as a lubricating oil for
internal combustion engineQ.
2. Descri~tion of the Related Art
Lubricating oils are usually used for smoothing the working
of internal combustion engines, driving -5` ~ni - such as automatic
transmi~ions, suspen~ions and power stearings, and gears. Particu-
larly, engine oilR are effective in lubricating mainly sliding parts
nuch as a piston ring and a cylinder liner, bearing~ of a crank shaft
or a connecting rod, and valve train including cam~ and valve lifters;
in cooling the engine; in cle~ning and disperning combustion products;
and in p ~væl.Ling ru3t f~ - ion and corrosion.
Thus, various functions are required for the engine oils and,
recently, even better function~ are being d =nded as the required
performance and engine output become higher and higher and the opera-
tion condition~ more severe. Under these circumstances, additives
~uch as an antiwear agent, metallic detergent, ashless dispersant and
ant;~Yj~nt are incorporated into the engine oil in order to satisfy
such requirements.
Since the energy loss in the friction parts in which the
lubricating oil participates is high in the engine, the lubricating
oil is used in combination with additives such as a friction modifier
(FM) in order to i nim~ ze the friction loss and i..,~ ove the fuel
con~umption (see, for example, J~r~n~se Patent Publication No.
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23595/1991). Further, since the engine oil for automobiles is used
under the various conditions of oil temperature, engine speed and
load, more excellent frictional properties under the wide-range
conditions of use are necessitated for further improving the fuel
consumption.
The present invention has been completed after investigations
made for the purpose of providing a lubricating oil composition having
; ~roved friction reducing properties over those of an ordinary
lubricating oil cont~ining molybdenum dithiocarbamate and a phosphoric
ester, and is suitable for use as a lubricating oil for internal
combustion engines, automatic transmissions, suspensions and power
steering wheels, particularly as a lubricating oil for internal
combustion engines.
SUMMARY OF THE INVENTION
After intensive investigations made for the purpose of
developing a lubricating oil composition having improved friction
reduction properties, the inventors have found that the above purpose
can be attained with a lubricating oil composition cont~; n; ng a
upecified ~ho~horic ester and/or phosphorous ester, sulfurized
oxymolyLæ- dithioc~rb- -te and a calcium sal$cylate in 3pecified
proportions. The present invention has been completed on the basis of
thi~ finding.
Specifically, the present invention provides a lubricating
oil composition which comprises a base oil con~;n;~g (A) from 0.01 to
0.8~ by weight, based on the whole composition, of at least one
~ _und ~elected from the group conaisting of (a) phosphoric esters
of the general formula:
Rl--O O
\11 3
P-O-R [1]
R2_o
l ~ 3 Z ~ 1
0 94/28094 PCT~US94/06001
wherein R1, R2 and R3 may be the same or different and each represents
a hydrogen atom or a hydrocarbyl group having 3 to 23 carbon atoms,
with the proviso that at least one of R1 to R3 is a hydrocarbyl group
having 3 to 23 carbon atoms, and
(b) phosphorous esters of the general formula:
R4--o
p_o_R6 [2]
R5-o
wherein R4, R5 and R6 may be the ~ame or different and each repreQent~
a hydrogen atom or a hydrocarbyl group having 3 to 23 carbon atoms,
with the proviso that at least one of R4 to R6 is a hydrocarbyl group
having 3 to 23 carbon atoms;
(B) from 50 to 2,000 ppm in terms of molybde- , of sulfurized
oxymolyb~e- dithiocarbamate having at least one hydrocarbyl group
having 8 to 18 carbon atoms; and
(C) from 0.3 to 2.5~ by weight, based on the whole composition of a
calcium salicylate having a total base number of 10 to 100.
DETAILED DESCRIPTIOW OF THE INV~w ~ lON
The base oil usable as the major component in the lubricating
oil composition of the present invention is not particularly limited.
Base oils are those usually used in ordinary lubricating oils, such as
mineral oil~ and synthetic oils.
The mineral oils include, for example, 60 neutral oil, lOO
neutral oil, 150 neutral oil, 300 neutral oil and 500 neutral oil
obtained by ~olvent refining or hydrorefining; and low-pour point base
oils prepared by removing a wax from these base oils 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.
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The synthetic oils include, for example, poly-~ olefin
oligomers, diesters, polyol esters and polyglycol esters. They are
usable either singly or in the form of a mixture. They are al~o
usable in the form of a mixture with the above-described mineral oil.
The blending weight ratio of the synthetic oil to the mineral oil is,
for example, 80:20 to 20:80.
A ~uitable base oil usable in the composition of the present
invention is one having a viscosity in the range of 3 to 20 cSt at
100C. Particularly preferred are hydrocracked products and/or wax
i~omerized products contAining 3.0~ by weight or below of an aromatic
c~mro~t and having a sulfur content of 50 ppm or below and a
nitrogen content of 50 ppm below.
In the composition of the present invention, the component
(A) is at least one compound selected from the group consisting of a
(a) phosphoric ester of the general formula:
Rl_o o
P--o--R3 [ l ]
R2_o
wherein Rl, R2 and R3 are each as defined above, and (b) phosphorous
esters of the general formula:
R4-o
\
p_o_R6 [2]
R5--o
wherein R4, R5 and R6 are each as defined above.
The groups Rl, R2 and R3 in the above general formula [l] may
be the same or different and each represents a hydrogen atom or a
hydrocarbyl group having 3 to 23 carbon atoms, with the proviso that
at least one of Rl to R3 is the hydrocarbyl group having 3 to 23
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0 94/28094 PCTrUS94/06001
carbon atoms. The hydrocarbyl groups having 3 to 23 carbon atoms
include linear, branched and cyclic alkyl and alkenyl groups having 3
to 23 carbon atoms, aryl groups having 6 to 23 carbon atoms, alkylaryl
groups having 7 to 23 carbon atoms and arylalkyl groups having 7 to 23
carbon atoms. Examples include propyl, butyl, pentyl, hexyl, cyclo-
hexyl, octyl, decyl, lauryl, myristyl, palmityl, stearyl, oleyl,
eicosyl, phenyl, xylyl, benzyl and phenethyl groups.
The groups R4, R5 and R6 in the above general formula [2] for
the phosphorous esters may be the same or different and each repre-
sents a hydrogen atom or a hydrocarbyl group having 3 to 23 carbon
atoms, with the proviso that at least one of R4 to R6 is a hydrocarbyl
group having 3 to 23 carbon atoms. Examples include those mentioned
above with reference to R1, R2 and R3 in the above general formula
[1~ .
The composition of the present invention may contain phos-
phoric esters either singly or in combination of two or more of them
and/or the phosphorous esters either singly or in combination of two
or more of them as the component (A). Further, a combination of one
or more of the phosphoric esters with one or more of the phosphorous
e~ters may be also used.
The composition of the present invention must contain the
phosphoric ester and/or phosphorus ester as the c~mro~ent (A) in an
amount of 0.01 to 0.8% by weight, preferably 0.05 to 0.5% by weight,
ba~ed on the whole composition. When the amount of (A) is below 0.01%
by weight, no sufficiently low frictional properties can be obtained
and, when it exceeds 0.8% by weight, there is no significant further
; _ ~v~ --t in frictional properties.
The sulfurized oxymolybdenum dithiocarbamates (MoDTC) which
contain at least one hydrocarbyl group having 8 to 18 carbon atoms are
used as component (B). MoDTC has a structure represented by the
following general formula:
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WO 94/28094 PCTrUS94/0600l
-R7 ~ [3]
~N-C-S Mo2SmOn
_R -2
The groups R7 and R8 in the above general formula [3] each
represent a hydrocarbyl group having 8 to 18 carbon atoms. The
hydrocarbyl groups having 8 to 18 carbon atoms include linear and
branched alkyl and alkenyl groups having 8 to 18 carbon atoms, and
cycloalkyl, aryl, alkylaryl and arylalkyl groups having 8 to 18 carbon
atoms. Examples include 2-ethylhexyl, n-octyl, nonyl, decyl, lauryl,
tridecyl, palmityl, stearyl, oleyl, eicosyl, butylphenyl and nonyl-
phenyl groups. R7 and Ry may be the same or different from each
other. m and n are positive integers such that the sum of m + n is 4.
In the composition of the present invention, the MoDTC used
as component (B) may be used singly or as a combination of two or more
of them. The amount of MoDTC is in the range of 50 to 2,000 ppm,
preferably 100 to 1,000 ppm (in terms of molybd~nlm) based on the
whole composition. When the amount of molybdenum is below 50 ppm, no
sufficient friction reduction properties can be obtained and when it
is above 2,000 ppm, there is no further significant i,..~ovl --t in the
frictional properties.
A calcium salicylate having a total base number of 10 to 100
is used as the component (C) in the composition of the present inven-
tion. The calcium salicylate is, for example, one represented by the
following general formula:
R9 ~ CO0-Ca-OOC ~ 9 [4]
The group R9 in the general formula [4] represents a linear, branched
or cyclic alkyl group having 8 to 23 carbon atoms, such as an octyl,
nonyl, decyl, dodecyl, pentadecyl, octadecyl or eicosyl group.
Z ~ G~ 3 Z- ~ 7
0 94/28094 PCT~US94/06001
The calcium salicylate used as component (c) may be used
either singly or in combination of two or more of them. The amount of
the calcium salicylate is in the range of 0.3 to 2.5% by weight based
on the whole composition. When the amount of (C) is below 0.3% by
weight, no sufficient low frictional properties can be obtained and,
when the amount exceeds 2.5% by weight, the wear resistance is reduced
and the ash content is increased unfavorably.
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 dis-
turbed.
The ashless detergent-dispersants include, for example,
SUCC; n i m; des, succinamides, benzylamines, their boron derivatives and
e~ters. 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, poly-
methacrylates, polyisobutylenes, ethylene/propylene copolymers and
hydrogenated styrene/buta~; ~n~ copolymers. They are used in an amount
of from 0.5 to 35% by weight, based on the whole composition. The
anti-oxidants include, for example, amine antioxidants such as
alkylated diphenylamines, phenyl-~-naphthylamines and alkylated
~-naphthyl~ines, and phenolic antioxidants such as 2,6-di-t-butyl-4-
methyl-phenol and 4,4'-methylenebis(2,6-di-t-butyl-4-methyl-phenol and
4,4'-methylenebi~(2,6-di-t-butylphenyl). They are used in an amount
of usually 0.05 to 2~ by weight, based on the whole composition.
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 oil composition.
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The following Bxamples further illustrate the present inven-
tion and do not limit the invention.
Examples 1 to 8 and Comparative Examples l to 5
The coefficient of friction of the lubricating oil composi-
tion was determined as follows:
(1) Coefficient of friction (~):
The coefficient of friction was determined by the LFW-1 test
under the conditions of 270 rpm, 30 kgf, 120C and lO minutes.
8ase oil 150N-l (having viscosity at 100C of 5.7 mm2/s,
aromatic component content of 4.1 wt~, sulfur content of ll.O 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
0.5 ppm and nitrogen content of O.l ppm) was used.
Each of the lubricating oil compositions listed in Table
wa~ prepared from the ba~e oil, and the coefficient of friction (~)
thereof wa~ dete_ i n~A . The results are given in Tables 1-1 and 1-2.
~3 ZO~
~VO 94/28094 PCT/US94/06001
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0 94/28094 PCTAUS94/06001
As demonstrated by Example~ 1-8 in Table 1-1, and comparative
Examples 1-5 in Table 1-2, a lubricating oil cont~ining the combina-
tion of salicylate, MoDTC and phosphoric ester according to the
invention provides a significantly lower coefficient of friction over
an oil compo~ition cont~ining any two c -n~nts.
The lubricating oil composition of the present invention ha~
~uperior low frictional properties to those of ordinary lubricating
oils comprising MoDTC and a pho~phoric ester, and is ~uitable for use
as a lubricating oil for, for example, internal combustion engines,
automatic transmission~, suspensions and power steering wheels,
particularly as a lubricating oil for internal combustion engines.
