Note: Descriptions are shown in the official language in which they were submitted.
CA 0223~449 1998-0~-2~
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BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to a lubricating oil composition, and more
specifically to a lubricating oil composition with a novel metal salt of an organic
acid added therein, said metal salt having a chain-hydrocarbon-group-substitutedaromatic structure and high friction characteristics improving effects.
DESCRIPTION OF THE PRIOR ART
It is the fundamental theme of lubrication to reduce friction and
wear which occur at sliding surfaces of moving parts in machineries, devices,
equipments and the like. Technical developments have been continued for many
years. In recent years, still further improvements are required in lubrication
technology for the reduction of friction and wear in the field of lubrication
especially ~om the viewpoint of resource and energy saving, and in attempts to
achieve low friction and low wear by improvements in the quality of lubricating
oils, investigations are now under way from a variety of viewpoints. For the
production of a lubricating oil excellent in friction characteristics with such
technical developments as a basis, it has already become indispensable to
incorporate additives in base stocks for lubricating oils so that the base stocks
can be provided with desired friction characteristics. Accordingly a number of
various friction modifiers have been proposed, resulting in the use of fatty acids
and their metal salts, alcohols, esters, amines and the like - all of which are of
the oiliness improver type - and phosphate esters, phosphite esters, zinc dithio-
phosphate and the like - all of which are of the extreme pressure agent type - in
automatic transmission fluids, wet brake oils, sliding surface oils, plastic work-
ing oils and the like; and also in the use of phosphate esters, phosphite esters,
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acidic phosphite ester amine salts, molybdenum dithiophosphate, molybdenum
dithiocarbamate and the like - all of which are of the extreme pressure agent type
- in engine oils, gear oils, cuKing oils and the like.
Meanwhile, an automatic transmission fluid has been proposed,
which contains magnesium sulfonate, especially over-based magnesium
sulfonate having a base number of 300 mg-KOH/g or greater and added to
improve its friction characteristics (see JP Kokai 62-84190). Further, it has also
been proposed to use calcium salicylate, which has been used as a metallic
delelge"t, as a friction coefficient modifier for automatic transmission fluids (see
JP Kokai 5-163496).
No matter whether these conventionally-proposed friction
modifiers are of the organic type or of the metallic type, their friction reducing
effects are however not sufficient. Especially, magnesium sulfonate, calcium
salicylate and the like are still insufficient in assuring stable reducing effects for
friction characteristic as their effects vary significantly depending on the kind
and use conditions of a lubricating base stock, although they provide friction
reducing effects to some extents. Therefore they merely exhibit advantageous
effects as friction-reducing adjuvants which show their effects when employed incombination with other friction modifiers. If an organic acid metal salt is
discovered with long-lasting stable friction reducing effects, it will find utility in
a much wider range of fields and hence to have a significantly-increased
industrial value. Its development has therefore been desired strongly.
In view of the technical developments on friction reducing
technology in lubrication field and the circumstances of development of
conventional friction modifiers as described above, the present invention has asan object thereof the provision of a lubricating oil composition which contains a
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novel metal salt of an organic acid, said metal salt having friction characteristics
improving ability.
PRESENT INVENTION
It has been found that it is important for an organic acid metal salt
to have a specific chain-hydrocarbon-group-substituted aromatic structure and
also that an organic acid metal salt, said metal salt being a metal salt of an
aromatic organic acid having a chain hydrocarbon group with the aromatic group
thereof being bonded to the chain hydrocarbon group at a particular position of
the chain hydrocarbon group, is excellent in friction characteristics improving
effects. Based on these findings, the present inventors have come to the
completion of the present invention.
Namely, the present invention relates to a lubricating oil composi-
tion characterized in that said composition comprises:
a lubricating base stock; and
a mixture of metal salts of chain-hydrocarbon-group-substituted
aromatic organic acids, each of said aromatic groups having been substituted by
at least one chain hydrocarbon group, and the number of chain hydrocarbon
groups each carrying at C-2 or C-3 thereof the associated aromatic group being
in a range of from 30% to 90% of the total number of said chain hydrocarbon
groups.
The present invention will hereinafter be described in detail.
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No particular limitation is imposed on the lubricating base stock
which is used as a component of the lubricating oil composition according to thepresent invention. The base stock can be any one of those conventionally used
as base stocks for lubricating oils, for example, any one of mineral base stocks,
synthetic base stocks and vegetable base stocks, or can be a blended base stock
of two or more of these base stocks.
As a mineral base stock, it is possible to use, for example, a
mineral oil obtained by the treatment of a lubricating oil fraction, which is inturn available by vacuum distillation of an atmosphere distillation residue of
paraffin-base, neutral or naphthene-base crude oil, through a refining step suchas solvent refining, hydrocracking, hydrotreatment, hydro-refining, catalytic
dewaxing, solvent dewaxing or clay treatment; a mineral oil obtained by subject-ing a vacuum distillation residue to solvent deasphalting and then treating the
resulting deasphalted oil through the above-described refining step; a mineral oil
obtained by isomerizing wax components; or a blended oil thereof. In the above
solvent refining, an aromatic extraction solvent such as phenol, furfural or
N-methylpyrrolidone can be used, whereas as a solvent for the solvent dewaxing,
liquefied propane, MEK/toluene, MEK/MIBK, or the like can be used. Further,
shape-selective zeolites can also be used in catalytic dewaxing.
Examples of synthetic base stocks, on the other hand, can include
poly(a-olefin) oligomers; polybutene; alkylbenzenes; polyol esters such as
trimethylolpropane esters and pentaerythritol esters; polyoxyalkylene glycols;
polyoxyalkylene glycol esters; polyoxyalkylene glycol ethers; dibasic acid esters;
phosphate esters; and silicone oils.
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Further, usable examples of vegetable base stocks can include
castor oil, rape seed oil, palm oil, coconut oil, olive oil and sunflower oil.
As various lubricating base stock such as those described above, it
is possible to use a blended base stock obtained by suitably blending plural base
stocks so that the blended base stock has a viscosity and other properties desired
for the intended application of the lubricating oil composition. For example, it is
preferred to control the kinematic viscosity at 100~C in a range of from 2 mm2/s
to 30 mm2/s, especially from 3 mm2/s to 10 mm2/s for a lubricating oil for
internal combustion engines, and the kinematic viscosity at 1 00~C in a range of
from 2 mm2/s to 30 mm2/s, especially from 3 mm2/s to 15 mm2/s for an
automatic tr~n~mi~sion fluid.
The organic acid metal salt added in the lubricating oil composi-
tion according to the present invention is composed of an organic acid portion,
which has a chain-hydrocarbon-group-substituted aromatic structure, and a metal
component portion. Specific examples can include metal sulfonates, metal
phenates, metal phenate sulfides, metal salicylates, metal salicylate sulfides,
metal phosphonates, and the like.
The metal component of the organic acid metal salt according to
the present invention can be an alkali metal or an alkaline earth metal.
Generally, a metal of an atomic number in a range of from 3 to 56 can also be
mentioned. Specif1c examples can include sodium, potassium, lithium, calcium,
magnesium and barium. In addition, aluminum, zinc, tin, chromium, copper,
cobalt and the like are also usable. In particular, calcium, magnesium, barium
and the like are preferred.
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Accordingly, preferred examples of the organic acid metal salt
according to the present invention include the sulfonates, phenates, salicylatesand the like of alkaline earth metals such as calcium, magnesium and barium.
The chain-hydrocarbon-group-substituted aromatic structure of the
organic acid metal salt according to the present invention is composed of
aromatic groups, as substituent groups, and a chain hydrocarbon group bonded
together. Each of the aromatic groups bonded to the chain hydrocarbon group
can be either monocyclic or fused polycyclic. Those represented by the follow-
ing formulas (a) to (g), respectively, are effective, with a phenyl group (a) and a
naphthyl group (d) being particularly preferred.
(a)
~> (b)
~>/ (c)
~ (d)
I~
~ (e)
~ (~
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~ (g)
No particular limitation is imposed on the chain hydrocarbon group
of the chain-hydrocarbon-group-substituted aromatic structure, but alkyl and
alkenyl groups and the like with 4-32 carbon atoms are preferred. Specific
examples can include alkyl groups such as butyl, pentyl, hexyl, octyl, nonyl,
decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl,
octadecyl, nonadecyl, eicosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl,
octacosyl, nonacosyl and triacontyl and their corresponding alkenyl groups.
Further, these alkyl and alkenyl groups may contain one or more groups such as
allyl, ester, ketone, ether, amine, amide, imide and/or like groups.
Specific examples of the chain-hydrocarbon-group-substituted
aromatic structure of the organic acid metal salt according to the present
invention can include alkylbenzenes, alkenylbenzenes, alkylnaphthalenes,
alkenylnaphthalenes, alkylanthracenes, alkenylanthracenes, and the like. In the
organic acid metal salt of the present invention, alkylbenzenes, alkenylbenzenes,
alkylnaphthalenes, alkenylnaphthalenes and the like are particularly preferred.
T~he number of substituted alkyl groups in the chain-hydrocarbon-group-
substituted aromatic structure, for example, an alkylbenzene may range from 1 to4, and the particularly-preferred chain-hydrocarbon-group-substituted aromatic
structure is one containing at least 25% of a chain-hydrocarbon-group-
substituted aromatic structure which contains one substituted alkyl group.
In the chain-hydrocarbon-group-substituted aromatic structure of
each organic acid metal salt according to the present invention, the chain
hydrocarbon group may be one carrying an associated aromatic group at C-2,
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C-3, C-4 or another carbon of the chain hydrocarbon group. According to an
investigation by the present inventors, however, it has become evident that a
mixture of chain-hydrocarbon-group-substituted aromatic structures of organic
acid metal salts, in which the sum of the number of chain hydrocarbon groups
each carrying at C-2 thereof an associated aromatic group bonded thereto and thenumber of chain hydrocarbon groups each carrying at C-3 thereof an associated
aromatic group bonded thereto falls within a range of from at least 30%, prefer-ably 30% to 90%, especially from 35% to 70% of the total number of the chain
hydrocarbon groups, is particularly good in friction reducing effects. If the
number of the chain hydrocarbon groups each carrying at C-2 or C-3 thereof the
associated aromatic group bonded thereto does not reach 30%, no sufficient
friction coefficient reducing effects can be brought about. Even if this number
exceeds 90%, the friction coefficient reducing effects cannot be obtained to such
an extent as corresponding to the increased proportion.
Further, if the number of chain hydrocarbon groups each carrying
at C-2 thereof the associated aromatic group bonded thereto accounts for 10% or
more of the total number of the chain hydrocarbon groups, the friction co-
efficient improving effects are improved further. A chain-hydrocarbon-group-
substituted aromatic structure, in which the ratio of the number of chain hydro-carbon group(s) each carrying at C-2 thereof an associated aromatic group
bonded thereto to the number of chain hydrocarbon group(s) each carrying at
C-3 thereof an associated aromatic group bonded thereto falls within a range of
from 10:90 to 90:10, notably from 30:70 to 70:30, brings about still higher
friction reducing effects and moreover, has better rubber compatibility improving
effects.
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Certain representative compounds of the organic acid metal salt
which can be added in the lubricating base stock in the present invention will be
exemplified below.
O O
Il 11
(I) A--S O M O S--B
O O
The above formula (I) exemplifies metal sulfonates. In the
formula, A and B represent chain-hydrocarbon-group-substituted aromatic
structures, which may be the same or different, and M represents an alkaline
earth metal. Each chain-hydrocarbon-group-substituted aromatic structure is
composed of an aromatic group with at least one chain hydrocarbon group
substituted thereon, and the sum of chain hydrocarbon groups each carrying at
C-2 or C-3 thereof the associated aromatic group bonded thereto ranges from
30% to 90% of the total number of chain hydrocarbon groups. Each aromatic
group may preferably be either monocyclic or dicyclic, typically a phenyl group
or a naphthyl group. The chain hydrocarbon groups are alkyl groups each
having 4-32 carbon atoms, preferably linear alkyl groups each having 12-30
carbon atoms.
OH OH
(Rl)n 11--O--M--O~
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OH M OH
(R2) ~ ~ (R2)n
~C--O--M--O--C--
OH OH
(R )n (R3)n
(IV) ~C--O--M--O--C ~
OH M OH
(R4) C--O--M--O--C~
The above formulas (II) to (V) exemplify metal salicylates and
metal salicylate sulfides, and in the respective formulas,
OH O-
(Rl) I (R2)
~ ~,
OH o_
(R3) 1 (R4)
~, and '~
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are chain-hydrocarbon-group-substituted aromatic structures. In the formulas
(II) to (V), Rls to R4s are alkyl groups having 4 to 32 carbon atoms, and in each
formula, these alkyl groups may be the same or different. Preferred alkyl groupsare those containing 12 to 30 carbon atoms, respectively. M represents an
alkaline earth metal, and n indicates the number of alkyl group(s) substituted on
the associated aromatic group. Further, in the formulas (IV) and (V), x stands
for a number of 1 to 5.
In these chain-hydrocarbon-group-substituted aromatic structures,
the sum of the numbers of chain hydrocarbon groups each canying at C-2 or C-3
thereof the associated aromatic group bonded thereto is 30% to 90% of the total
number of the chain hydrocarbon groups.
O M O
(R5)n (Rs)n
O M O
(R6)n (R6)n
(VII) \~ SX ~/
The above fonmulas (VI) and (VII) exemplify metal phenates and
metal phenate sulfides having chain-hydrocarbon-group-substituted aromatic
structures. In the respective formulas, the chain-hydrocarbon-group-substituted
aromatic structures are:
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(R )n (R )n
'~, and ~
In the formulas (VI) and (VII), R5 and R6 are alkyl groups having
4 to 32 carbon atoms, which may be the same or different. Preferred alkyl
groups are those having 12 to 30 carbon atoms. M represents an alkaline earth
metal, and n indicates the number of alkyl group(s) substituted on the associated
aromatic group. In the formula (VII), x stands for a number of 1 to 5.
In these chain-hydrocarbon-group-substituted aromatic structures,
the sum of the numbers of chain hydrocarbon groups each carrying at C-2 or C-3
thereof the associated aromatic group substituted thereon is 30% to 90% of the
total number of the chain hydrocarbon groups.
The organic acid metal salt according to the present invention can
provide friction coefficient reducing effects no matter whether it is a neutral salt
or an over-based salt. An over-based salt is in the form of a colloidal system in
which a metal hydroxide or metal carbonate is primarily dispersed in the form offine particles in an organic acid metal salt. As an over-basing method, a methodknown well to date can be adopted, for example, an acidic substance is reacted
with a reaction mixture of an organic acid or a salt thereof and a metal
compound. As the acidic substance, a gas such as carbon dioxide or sulfur
dioxide can be used. For example, an over-based alkaline earth metal salicylate
can also be produced by treating its neutral salt with carbon dioxide (see, for
example, U.S. Patent No. 3,057,896).
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Concerning the proportion of the organic acid metal salt to be
added in the lubricating oil composition according to the present invention,
sufficient friction reducing effects can be exhibited provided that the organic
acid metal salt is added in a proportion of from 0.01 wt% to 10 wt%, preferably
from 0.05 to 5 wt% based on the whole weight of the lubricating oil composition
or in a proportion of from 1 ppm to 10,000 ppm, preferably from 50 ppm to
5,000 ppm in terms of the content of the metal although the proportion varies
depending on the application purpose of the lubricating.
To the lubricating oil composition according to the present
invention, it is also possible to add selected ones of viscosity index improvers,
ashless dispersants, anti-oxidants, extreme pressure agents, wear inhibitors,
metal deactivators, pour-point depressants, rust inhibitors, other friction
modifiers and other additives as desired.
Illustrative usable examples of the viscosity index improvers can
include polymethacrylates, polyisobutylenes, ethylene-propylene copolymers,
and hydrogenated styrene-butadiene copolymers. These viscosity index
improvers are used generally in a proportion of from 3 wt% to 35 wt%.
Illustrative of the ashless dispersants can be polybutenyl-
succinimides, polybutenylsuccinamides, benzylamines, and succinate esters.
They can be used generally in a proportion of from 0.05 wt% to 7 wt%.
Illustrative examples of the anti-oxidants can include amine-type
anti-oxidants such as alkylated diphenylamines, phenyl-a-naphthylamine and
alkylated phenyl-a-naphthylamines; phenol-type anti-oxidants such as 2,6-di-t-
butylphenol and 4,4'-methylene-bis(2,6-di-t-butylphenol); and zinc
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dithiophosphate. They can be used generally in a proportion of from 0.05 wt%
to 5 wt%.
Illustrative of the extreme pressure agents can be dibenzyl sulfide
and dibutyl disulfide. They can be used generally in a proportion of from
0.05 wt% to 3 wt%.
Illustrative examples of the metal deactivators can include benzo-
triazole, benzotriazole derivatives, and thiadiazole. They can be used generallyin a proportion of from 0.01 wt% to 3 wt%.
Illustrative of the pour-point depressants can be ethylene-vinyl
acetate copolymers, chlorinated paraffin-naphthalene condensation products,
chlorinated paraffin-phenol condensation products, polymethacrylates, and
polyalkylstyrenes. They can be used generally in a proportion of from 0.1 wt%
to 10 wt%.
Illustrative of the wear inhibitors can be phosphate esters, acidic
phosphate esters, phosphite esters, acidic phosphite esters, zinc dialkyldithio-phosphates, and sulfur compounds. They can be used generally in a proportion
of from 0.01 wt% to 5 wt%.
Other additives can also be selectively used as described provided
that they do not inhibit the action of the organic metal salt according to the
present invention.
The organic acid metal salt according to the present invention can
be used in a form dissolved in a solvent such as a mineral oil. It can also be used
as a component of an additive package.
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As preferred embodiments of the present invention, it is possible to
provide:
(i) A lubricating oil composition comprising:
a lubricating base stock; and
a mixture of metal salts of chain-hydrocarbon-group-substituted
aromatic organic acids, each of said aromatic groups having been substituted by
at least one chain hydrocarbon group, and the sum of the number of chain
hydrocarbon groups each carrying at C-2 or C-3 thereof the associated aromatic
group bonded thereto being in a range of from 35% to 70% of the total number
of the chain hydrocarbon groups.
(ii) A lubricating oil composition comprising:
a lubricating base stock; and
a mixture of metal salts of chain-hydrocarbon-group-substituted
aromatic organic acids, each of said aromatic groups having been substituted by
at least one chain hydrocarbon group, the number of chain hydrocarbon groups
each carrying at C-2 thereof the associated aromatic group bonded thereto is at
least 10% of the total number of the chain hydrocarbon groups, and the ratio of
the number of the chain hydrocarbon groups each carrying at C-2 thereof the
associated aromatic group bonded thereto to that of chain hydrocarbon groups
each carrying at C-3 thereof an associated aromatic group bonded thereto is in arange of from 10:90 to 90:10.
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(iii) A lubricating oil composition comprising:
a lubricating base stock; and
a mixture of metal salts of chain-hydrocarbon-group-substituted
aromatic organic acids, each of said aromatic groups having been substituted by
at least one chain hydrocarbon group, the number of chain hydrocarbon groups
each carrying at C-2 thereof the associated aromatic group bonded thereto is
greater than 10% of the total number of the chain hydrocarbon groups, and the
ratio of the number of the chain hydrocarbon groups each carrying at C-2 thereofthe associated aromatic group bonded thereto to that of chain hydrocarbon
groups each carrying at C-3 thereof an associated aromatic group bonded thereto
is in a range of from 10:90 to 65:35.
(iv) A lubricating oil composition comprising:
a lubricating base stock;
a mixture of metal salts of chain-hydrocarbon-group-substituted
aromatic organic acids each substituted by at least one chain hydrocarbon group,the number of chain hydrocarbon groups each carrying at C-2 or C-3 thereof the
associated aromatic group bonded thereto being in a range of from 30% to 90%
of the total number of the chain hydrocarbon groups; and
at least one additive selected from the group consisting of viscosity
index improvers, ashless dispersants, anti-oxidants, wear inhibitors and metal
deactivators.
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EXAMPLES
The present invention will next be described specifically by
Examples and Comparative Examples.
For the structure analysis of each chain-hydrocarbon-group-
substituted aromatic structure in each organic acid metal salt and also for the
evaluation of performance (coefficient of friction) of each lubricating oil
composition, the following measuring methods were adopted.
Structure analysis of chain-hydrocarbon-group-substituted
aromatic structure in organic acid metal salt analyzed by a l3C-NMR
measurement.
Measuring method of friction coefficient:
By a testing method similar to JASO M348-95 entitled "ATF
(Automatic Transmission Fluid) Friction Characteristics Testing Method", a
static friction coefficient after l O c/c was measured by using an SAE No. 2
friction machine. As a friction material, SD1777 was used.
Example 1
Refined mineral oil lOOSN (kinematic viscosity: 4.1 mm2/s at
100~C) was used as a lubricating base stock. To the refined mineral oil, 1.0 wt%(1,000 ppm in terms of Ca content) of an over-based alkylbenzene calcium
sulfonate - in which, as shown in Table 1, the average carbon number of alkyl
groups was 23, the number of alkyl groups each carrying at C-2 thereof an
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associated phenyl group bonded thereto was 27% of the total number of the alkyl
groups, and the sum of the number of alkyl groups each carrying at C-2 or C-3
thereof an associated phenyl group bonded thereto was 53% of the total number
of the [phenyl] alkyl groups - was added as an organic acid metal salt, whereby a
lubricating oil composition was formulated. The friction coefficient of the thus-
obtained lubricating oil composition was measured by the above-described
method. It was found to be 0.133.
Example 2
To the refined mineral oil lOOSN (kinematic viscosity: 4.1 mm2/s
at 100~C), 1.0 wt% (100 ppm in terms of Ca content) of a neutral alkylbenzene
calcium sulfonate - in which the average carbon number of alkyl groups was 22,
the number of alkyl groups each carrying at C-2 thereof an associated phenyl
group bonded thereto was 28% of the total number of the alkyl groups, and the
sum of the number of alkyl groups each carrying at C-2 or C-3 thereof an
associated phenyl group bonded thereto was 45% of the total number of the alkyl
groups - was added, whereby a lubricating oil composition was formulated. As a
result of a measurement of the friction coefficient of the thus-obtained lubricat-
ing oil composition, it was found to be 0.134.
Example 3
To the refined mineral oil lOOSN (kinematic viscosity: 4.1 mm2/s
at 100~C), 1.0 wt% (1,000 ppm in terms of Ca content) of an over-based alkyl-
benzene calcium sulfonate - in which the number of alkyl groups each carrying
at C-2 thereof an associated phenyl group bonded thereto was 14% of the total
number of the alkyl groups, and the number of alkyl groups each carrying at C-2
or C-3 thereof an associated phenyl group bonded thereto was 37% of the total
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number of the alkyl groups - was added, whereby a lubricating oil composition
was formulated. The friction coefficient of the thus-obtained lubricating oil
composition was found to be 0.140.
Comparative Example 1
The refined mineral oil lOOSN (kinematic viscosity: 4.1 mm2/s at
100~C) was used as a lubricating base stock. The friction coefficient of the
lubricating base stock alone was measured without addition of an organic acid
metal salt. It was found to be 0.168.
Comparative Example 2
To the refmed mineral oil lOOSN (kinematic viscosity: 4.1 mm2/s
at 100~C), 1.0 wt% (1,000 ppm in terms of Ca content) of an over-based
alkylbenzene calcium sulfonate - in which the average carbon number of alkyl
groups was 25.5, the number of alkyl groups each carrying at C-2 thereof an
associated phenyl group bonded thereto was 6% of the total number of the alkyl
groups, and the sum of the number of alkyl groups each carrying at C-2 or C-3
thereof an associated phenyl group bonded thereto was 9% of the total number of
the alkyl groups - was added, whereby a lubricating oil composition was
formulated. As a result of a measurement of the friction coefficient of the thus-
obtained lubricating oil composition, it was found to be 0.164.
The structures of the organic acid metal salts used in the Examples
and the Comparative Examples and the performance evaluation results (SAE No.
2 friction coefficient measurement results) of the lubricating oil compositions are
shown in Table 1.
TABLE 1
Comparative Comparative
Example I Example 2 Example 3 Example 1 Example 2
Base stock Refined mineral oil 100SN
Over-based Neutral alkyl- Over-based Notadded Over-based
alkyl-benzene benzene Ca alkyl-benzene alkyl-benzene
Organic acidmetal salt Ca sulfonate sulfonate Ca sulfonate Ca sulfonate ~
Amount added 1.0% 1.0% 1.0% - - 1.0%
Average carbon number of alkyl group 23 22 22 - - 25.5 ~
Percentage of alkyl groups each carrying at 27% 28% l4% 6%
C-2 thereof its associated aromatic group
bonded thereto
Percentage of alkyl groups each carrying at 26% 17% 23% - - 3%
C-3 thereof its associated aromatic group
bonded thereto
Percentage of alkyl groups each carrying at 22% 18% 48% - - 9%
C-4 thereof its associated aromatic group
bonded thereto
TABLE l (continued)
Comparative Comparative
Example 1 Example 2 Example 3 Example 1 Example 2
Base stock Refinedmineral oil lOOSN
Percentage of alkyl groups each carrying at 53% 45% 37% 9% "
C-2 or C-3 thereof its associated aromatic
group bonded thereto i-
Percentage of alkyl groups each carrying at 75% 63% 85% 18% ~,,
C-2, C-3 or C-4 thereof its associated
aromatic group bonded thereto
SAE No. 2 friction coefficient 0.133 0.134 0.140 0.168 0.164
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From the above Examples and Comparative Examples, the friction
coefficient reducing effects by the control of the total percentage of chain
hydrocarbon group(s) each carrying at C-2 thereof an associated aromatic group
bonded thereto and chain hydrocarbon group(s) each carrying at C-3 thereof an
associated aromatic group bonded thereto has been clarified although there is nocorrelation between the individual percentages of the hydrocarbon groups each
carrying at C-3 thereof the associated aromatic group bonded thereto and the
chain hydrocarbon groups each carrying at C-4 thereof an associated aromatic
group bonded thereto and a friction coefficient. Namely, it has been
demonstrated that the friction coefficient is significantly lowered when the
percentage of the number of chain hydrocarbon groups each carrying C-2 or C-3
thereof an associated aromatic group bonded thereto based on the number of all
the chain hydrocarbon groups is 30% or higher.
Thus it is seen that a lubricating oil composition containing a
mixture of organic acid metal salts having chain-hydrocarbon-group-substituted
aromatic structures in which the sum of the number of chain hydrocarbon groups
each carrying at C-2 or C-3 thereof an associated aromatic group bonded thereto
is 30% to 90% of the total number of the chain hydrocarbon groups. For
example, a calcium sulfonate with aromatic group(s) bonded concentrating on a
specific position of C-2 or C-3 of an associated chain hydrocarbon group(s)
exhibits extremely high friction coefficient improving effects. Use of the
enumerated metal salts makes it possible to provide a lubricating oil composition
of improved in friction characteristics.
