DESCRIPTION
LUBRICANT OIL COMPOSITION
5 TECHNICAL FIELD
[0001] This invention relates to a lubricant oil composition, more specifically to a
lubricant oil composition preferably used in an application such as a lubricant oil
composition for an internal combustion engine.
10 BACKGROUND ART
[0002] To a lubricant oil composition for internal combustion engines, in order to
improve fuel saving property, an organic molybdenum compound, particularly
molybdenum ditbiocarbamate (MoDTC) is often added as a friction modifier (e.g., see
Patent Documents 1 to 3 below). However, since MoDTC is poor at maintaining effect
15 and is likely to poison an exhaust gas treatment catalyst with the metal content, a friction
modifier to replace MoDTC has been sought.
[0003] Thus, in particular, as a friction modifier having no influence on an exhaust
gas treatment catalyst, development of an amphipathic molecule having a polar portion
and an oil soluble portion, more specifically an oil soluble surfactant type ashless friction
20 modifier has been attempted. However, while ashless friction modifiers which have
been developed so far have an effect to some extent, one with a similar or better
performance than MoDTC has not yet been discovered.
[0004] On the other hand, to a lubricant oil composition for internal combustion
engines, in order to improve high temperature detergency and acid neutralizing property,
25 various additives are added (e.g., see Patent Documents 4 to 5 below). However, these
additives generally act in the direction of increasing fkiction, and inhibit the fuel saving
effect.
PRIOR ART DOCUMENTS
30 Patent Documents
[0005] Patent Document 1: JP-A-H06-336592
Patent Document 2: JP-A-H06-336593
Patent Document 3: WO-A-20091104682
Patent Document 4: JP-A-2004-067808
Patent Document 5: JP-A-2003-277782
SUMMARY OF INVENTION
(Technical Problem)
5 [0006] Under such circumstances, the object of the invention is to provide a lubricant
oil composition capable of maximizing the friction reducing effect by optimizing a base
oil and an additive other than a friction modifier used in a lubricant oil composition,
particularly a lubricant oil composition for an internal combustion engine.
(Solution to Problem)
10 [0007] The inventors have, as a result of devoted studies for achieving the above
object, found that a lubricant oil composition capable of maximizing the friction reducing
effect can be obtained by optimizing the sulfur content and the aromatic content of a base
oil, and a certain metal-based detergent, and completed the invention.
[0008] Thus, the invention is a lubricant oil composition containing:
15 a base oil (A), wherein the sulfur content is not less than 0.03 mass%, and the
mass ratio [%CA (mass%)/sulfur content (mass%)] between the aromatic content (%C.A.)
and the sulfur content is not more than 30, and;
a metal salicylate-based detergent (B) in not more than 3 mass% as an alkali
metal or alltali earth metal amount based on the total amount of the composition.
20 [0009] In a preferred example of the lubricant oil composition of the invention, the
carbon number of an alkyl chain of a soap group of the metal salicylate-based detergent
(B) is not less than 10 as an average.
[0010] In another preferred example of the lubricant oil composition of the invention,
the metal salicylate-based detergent (B) is an overbased calcium carbonate salicylate.
25 [0011] The lubricant oil composition of the invention is preferable to be a lubricant
oil composition for an internal combustion engine.
[0012] Also, the invention is a method for improving the fuel saving property of an
internal combustion engine by using the above lubricant oil composition.
(Advantageous Effect of Invention)
30 [0013] According to the invention, it is possible to provide a lubricant oil
composition, particularly a lubricant oil composition for an intemal combustion engine,
excellent in fuel saving property and capable of sufficiently reducing friction under
boundary lubrication conditions and under mixed lubrication conditions even without a
friction modifier.
P0124052-PCT (2120)
DESCRIPTION OF EMBODIMENTS
[0014] Preferred embodiments of the invention will be described in detail below.
The lubricant oil composition of the invention contains a base oil (A) wherein the sulfur
5 content is not less than 0.03 mass%, and the mass ratio [%CA (rnass%)/sulfur content
(mass%)] between the aromatic content (%CA) and the sulfur content is not more than 30,
and a metal salicylate-based detergent (B) in not more than 3 mass% as an allcali metal or
alkali earth metal amount based on the total amount of the composition.
[0015] In the base oil (A) of the lubricant oil composition of the invention, the sulfur
10 content is not less than 0.03 mass%, preferably not less than 0.1 mass%, further
preferably not less than 0.2 mass%, further more preferably not less than 0.3 mass%,
particularly preferably not less than 0.4 mass%, most preferably not less than 0.5 mass%.
Also, in the based oil (A), the sulfur content is preferably not more than 1.2 mass%,
further preferably not more than 1 mass%, further more preferably not more than 0.8
15 mass%, particularly preferably not more than 0.7 mass%. With the sulfur content of the
base oil (A) of not less than 0.03 mass%, friction is reduced, and when it is used as a
lubricant oil for an internal combustion engine, a lubricant oil composition excellent in
fuel saving property can be obtained. However, with the sulfur content of the base oil
(A) of more than 1.2 mass%, oxidation stability of the lubricant oil composition
20 deteriorates, sludge and the lilce easily occur, which are not preferable.
[0016] It should be noted that the "sulfur content" herein refers to a value measured
according to JIS I< 2541-4 "Energy Dispersive X-ray Fluorescence Method" (normally,
within a range of 0.01 to 5 mass%) or JIS K 2541-5 "General Bomb Method,
Supplementary Notes (Rules), Inductively Coupled Plasma Atomic Emission
25 Spectrometry" (normally, not less than 0.05 mass%).
[0017] In the base oil (A) of the lubricant oil composition of the invention, the mass
ratio [%CA (mass%)/sulfur content (mass%)] between the aromatic content (%CA) and the
sulfur content is not more than 30, preferably not more than 15, more preferably not more
than 12, and also, preferably not less than 5, more preferably not less than 7. With
30 the %C.~./dfur content of the base oil (A) of not more than 30, the friction reducing effect
increases, while with that of less than 5, the influence of sulfur becomes too much, and
the friction coefficient is concerned to be large conversely.
[0018] Moreover, although the %CA of the above base oil (A) is not particularly
limited as long as it meets the ranges of the mass ratio [%CA (mass%)/sulfur content
P0124052-PCT (3120)
(mass%)] between the aromatic content (%CA) and the sulfur content as described above,
it is preferably not more than 20, more preferably not more than 15, particularly
preferably not more than 10, in terms of oxidation stability. It should be noted that
the %CA is obtained by a method according to ASTM D 3238 (n-d-M ring analysis).
5 [0019] The base oil (A) of the lubricant oil composition of the invention is not
limited as long as the sulfur content is not less than 0.03 mass% and the mass ratio [%CA
(mass%)/sulfur content (mass%)] between the aromatic content (%CA) and the sulfur
content is not more than 30. Therefore, the base oil (A) may contain at least one land of
sulfur containing mineral base oils shown below, alone or in combination with one land
10 or two or more ltinds of other mineral base oils or synthetic base oils.
[0020] The above mineral base oil specifically includes one formed by vacuum
distilling an atmospheric residue obtained by atmospheric distilling a crude oil to obtain a
lubricant oil fraction, and refining it in one or more treatments such as solvent
deasphalting, solvent extraction, hydrogenolysis, solvent dewaxing and hydrogenation
15 refining.
[0021] Also, as an example of a base oil hardly containing sulfur, a wax isomerized
mineral oil, a base oil produced by a method of isomerizing GTL WAX (gas-to-liquid
wax), a synthetic base oil, and the like can be exemplified.
[0022] As the above synthetic base oil, specifically, polybutene or hydride thereof;
20 poly-a-olefin such as 1-octene oligomer and 1-decene oligomer or hydride thereof;
diester such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl
adipate, di-2-ethylhexyl sebacate; polyol ester such as neopentyl glycol ester, trimethylol
propane caprylate, trimethylol propane pelargonate, pentaerythritol-2-ethylhexanoate and
pentaerythritol pelargonate; aromatic synthetic oil such as allcylnaphthalene, alkylbenzene,
25 and aromatic ester or mixture thereof, and the like can he exemplified.
[0023] Moreover, although the ltinematic viscosity of the above base oil (A) is not
particularly limited, its liinematic viscosity at 100°C is preferably not more than 20 mm2/s,
more preferably not more than 15 mm2/s, particularly preferably not more than 10 mm2/s.
On the other hand, the ltinematic viscosity at 100°C of the base oil (A) is preferably not
30 less than 1 mm2/s, more preferably not less than 2 mm2/s. With the ltinematic viscosity
at 100°C of the base oil (A) of more than 20 mm2/s, low temperature viscosity property
deteriorates, while with the ldnematic viscosity at 100°C of less than I d s , lubricity is
poor due to insufficient oil film formation at a lubrication point, and also the evaporation
loss of a lubricant base oil is large, which are both not preferable.
[0024] Furthermore, although the viscosity index of the above base oil (A) is not
particularly limited and is normally not more than 200, its viscosity index is preferably
not less than 80, further preferably not less than 100, particularly preferably not less than
120, so that excellent viscosity property can be obtained from a low temperature to a high
5 temperature. When the viscosity index of the base oil (A) is less than 80, low
temperature viscosity property tends to deteriorate. Also, the viscosity index of the base
oil (A) is preferable to be not more than 160.
[0025] The lubricant oil composition of the invention contains a metal salicylatebased
detergent (B). Here, as the metal salicylate-based detergent (B), a metal salicylate
10 represented by the following general formula (I), andlor its (over)basic salt are preferable.
[0026]
[Chem. 11
[0027] In the above general formula (I), R' is an allcyl group or alkenyl group, M
15 represents an alkali metal or allcali earth metal, preferably calcium or magnesium,
particularly preferably calcium, and n is 1 or 2.
[0028] Moreover, as the above metal salicylate-based detergent (B), alkali metal or
allcali earth metal salicylate preferably having one allcyl group or allenyl group within a
molecule, andlor its (over)basic salt are preferable.
20 [0029] The method for producing the above alltali metal or alkali earth metal
salicylate is not particularly limited, and a publicly known method for producing
monoallcyl salicylate and the lilte can be used. For example, the above alkali earth metal
salicylate can be obtained by subjecting a monoalkylsalicylic acid obtained by using a
phenol as a starting raw material, alkylating it using olefm and carboxylating it with a
25 carbon dioxide gas and the lilte, a monoalkylsalicylic acid obtained by using a salicylic
acid as a starting raw material and alkylating it using an equivalent of the above olefin, or
the like, to a reaction with a metal base such as an oxide and hydroxide of an alkali metal
or alkali earth metal, conversion to an alkali metal salt such as a sodium salt and
potassium salt once, then substitution it with an alltali earth metal salt, or the lilte.
30 [0030] The metal salicylate-based detergent (B) for use in the lubricant oil
composition of the invention includes, not only a neutral salt as obtained above, but also a
basic salt obtained by heating the neutral salt and an additional excessive alltali metal or
alltali earth metal salt or alkali metal or alltali earth metal base (hydroxide or oxide of
alkali metal or alltali earth metal) in the presence of water, or an overbased salt obtained
by reacting the neutral salt with a base such as hydroxide of alkali metal or allcali earth
5 metal in the presence of a carbon dioxide gas, or boric acid or borate.
[0031] In the lubricant oil composition of the invention, the content of the metal
salicylate-based detergent (B) is not more than 3 mass%, preferably 0.05 to 2 mass%,
W e r preferably 0.05 to 1.5 mass%, further more preferably 0.05 to 0.8 mass%,
particularly preferably 0.05 to 0.5 mass%, most preferably 0.05 to 0.25 mass% as an
10 alltali metal or alltali earth metal amount based on the total amount of the composition.
With the content of the metal salicylate-based detergent (B) based on the total amount of
the composition of less than 0.05 mass% as an alkali metal or allcali earth metal amount, a
friction reducing effect is not sufficiently exerted, which is not preferable, while with that
of more 3 mass%, a friction reducing effect is decreased.
15 [0032] As the metal salicylate-based detergent (B) for use in the lubricant oil
composition of the invention, it is preferable to use one with a metal ratio of normally 1.0
to 30. A metal salicylate-based detergent with a metal ratio of less than 1.0 has an acid
remained and is likely to have corrosive property, while a metal salicylate-based detergent
with a metal ratio of not less than 30 is unstable and is likely to generate aprecipitate,
20 which are not preferable. Here, the metal ratio of the metal salicylate-based detergent
(B) is represented by the valence number of a metal-based element in a salicylate-based
detergent x metal element content (mol%) 1 soap group content (mol%), the metal
element means calcium, magnesium and the lilte, and the soap group means a salicylic
acid group and the like.
25 [0033] In the above general formula (I), the carbon number of R' is preferably 10 to
40, more preferably 14 to 30, further preferably not less than 20. Also, R' is preferably
an alkyl group, more preferably a secondary alkyl group. With the carbon number of R'
of less than 10, a sufficient friction reducing effect cannot be obtained, while with the
carbon number of R' of more than 40, the low temperature flow property as a lubricant oil
30 composition deteriorates, which is not preferable.
[0034] In the metal salicylate-based detergent (B) for use in the lubricant oil
composition of the invention, the carbon number of an alliyl chain of a soap group is
preferable to be not less than 10 as an average. When the carbon number of an alliyl
chain of a soap group is not less than 10 as an average, a sufficient friction reducing effect
can be obtained.
[0035] As the metal salicylate-based detergent (B) for use in the lubricant oil
composition of the invention, an overbased calcium carbonate salicylate is preferable.
The overbased calcium carbonate salicylate is one obtained by overbasing with calcium
5 carbonate a neutral calcium salicylate which is obtained by a method of neutralizing a
hydrocarbon group substituted salicylic acid with an equivalent of a calcium base such as
calcium hydroxide and calcium oxide, and the like.
[0036] To the lubricant oil composition of the invention, other than the metal
salicylate-based detergent (B) describe above, in order to further improve its acid
10 neutralizing property, high temperature detergency and anti-wear property, a metal-based
detergent such as a sulfonate-based detergent, phenate-based detergent and carboxylatebased
detergent can be added. Here, the metal-based detergent other than the metal
salicylate-based detergent (B) includes, for example, alkali metal sulfonate or allcali earth
metal sulfonate, alkali metal phenate or alkali earth metal phenate, allcali metal
15 carboxylate or allcali earth metal carboxylate, mixture thereof, or the like.
[0037] As the above alkali metal or allcali earth metal sulfonate, more specifically,
for example an alkali metal salt or alkali earth metal salt, particularly a magnesium salt
andlor calcium salt of an alkyl aromatic sulfonic acid obtained by sulfonating an alliyl
aromatic compound with a molecular weight of 100 to 1500, preferably 200 to 700 is
20 preferably used, and as the alkyl aromatic sulfonic acid, a so-called petroleum sulfonic
acid, synthetic sulfonic acid and the like are specifically included.
[0038] As the above alkali metal or alkali earth metal phenate, more specifically, an
allcali metal salt or alkali earth metal salt, particularly a magnesium salt andlor calcium
salt of alkylphenol having at least one linear or branched alkyl group with a carbon
25 number of 4 to 30, preferably 6 to 18, alkylphenol sulfide obtained by reacting this
allcylphenol with an elemental sulfur, or a Mannich reaction product of alkylphenol
obtained by reacting this allylphenol with formaldehyde, and the like are preferably used.
[0039] As the above allcali metal or allcali earth metal carboxylate, more specifically,
an alkali metal salt or alkali earth metal salt, particularly a magnesium salt andlor calcium
30 salt of an alkyl benzoic acid having at least one linear or branched alkyl group with a
carbon number of 4 to 30, preferably 6 to 18, and the like are preferably used.
[0040] Moreover, metal-based detergents are normally on market and also available
in a state of being diluted by a light lubricant base oil and the like. Generally, it is
desirable to use one with ametal content of 1.0 to 20 mass%, preferably 2.0 to 16 mass%.
Furthermore, the total base number of the metal-based detergents is normally 0 to 500 mg
KOHlg, preferably 20 to 450 mg ICOHlg. It should be noted that the total base number
herein refers to a total base number measured by a perchloric acid method according to 7.
of JIS K2501 "Petroleum Products and Lubricants - Determination of Neutralization
5 Number".
[0041] Also, the lubricant oil composition of the invention is preferable to further
contain an ashless dispersant. As the ashless dispersant, an optional ashless dispersant
for use in lubricant oils can be used, and for example, a nitrogen containing compound
having at least one linear or branched allyl group or allcenyl group with a carbon number
10 of 40 to 400 within a molecule or its derivative, a modified product of allcenylsuccinimide,
benzylamine, polyamine, or the like is included. To the lubricant oil composition of the
invention, one kind or two or more kinds optionally selected from them can be formulated.
[0042] The carbon number of an allyl group or allcenyl group of alkenylsuccinimide
is preferably 40 to 400, more preferably 60 to 350. With the carbonnumber of an alkyl
15 group or alkenyl group of less than 40, the solubility of a compound in a lubricant base oil
tends to decrease, while with the carbon number of an allcyl group or alkenyl group of
more than 400, the low temperature flow property of a lubricant oil composition tends to
deteriorate. Although this alkyl group or alkenyl group may be linear or branched,
specifically, a branched alkyl group or branched alkenyl group derived from an oligomer
20 of olefm such as propylene, 1-butene and isobutylene or a cooligomer of ethylene and
propylene, and the lilce are preferably included.
[0043] The lubricant oil composition of the invention may contain either or both of
monotype or bistype succinimides.
[0044] The method for producing succinimide is not particularly limited, and it can
25 be obtained by, for example reacting an allcylsuccinic acid or alkenylsuccinic acid
obtained by reacting a compound having an alkyl group or alkenyl group with a carbon
number of 40 to 400 with maleic anhydride at 100 to 200°C with a polyamine. As the
polyamine, specifically, diethylene triamine, triethylene tetramine, tetraethylene
pentamine, pentaethylene hexamine, and the lilce can be exemplified.
30 [0045] As the above benzylamine, more specifically, a compound represented by the
following general formula (2), and the lilce can be exemplified.
[Chem. 21
C%NH-(CH&%NH),-H . . . (2)
[0046] In the above general formula (2), R2 represents an alkyl group or alkenyl
group with a carbon number of 40 to 400, preferably 60 to 350, and p represents an
integer of 1 to 5, preferably 2 to 4.
5 [0047] Although the method for producing the above benzylamine is not
particularly limited, for example, it can be obtained by reacting apolyolefin such as a
propylene oligomer, polybutene, and ethylene-a-olefin copolymer with a phenol into
alkylphenol, and then reacting it with formaldehyde and polyamine such as diethylene
triamine, triethylene tetramine, tetraethylene pentamine, and pentaethylene hexamine by a
10 Mannich reaction.
[0048] As the above polyamine, more specifically, a compound represented by the
following general formula (3), and the like can be exemplified.
R3-NH-(CH~CH~NH),-H . . . (3)
[0049] In the above general formula (3), R3 represents an alkyl group or alkenyl
15 group with a carbon number of 40 to 400, preferably 60 to 350, and q represents an
integer of 1 to 5, preferably 2 to 4.
[0050] Although the method for producing the above polyamine is not particularly
limited, for example, it can be obtained by chlorinating a polyolefin such as a propylene
oligomer, polybutene, and ethylene-a-olefin copolymer, and then reacting it with
20 ammonia and polyamine such as ethylene diamine, diethylene triamine, triethylene
tetramine, tetraethylene pentamine and pentaethylene hexamine.
[0051] Moreover, the derivative of the nitrogen containing compound exemplified as
one example of the ashless dispersant specifically includes, for example, a so-called acid
modified compound formed by reacting the nitrogen containing compound described
25 above with a monocarboxylic acid with a carbon number of 1 to 30 (fatty acid, etc.) and a
polycarboxylic acid with a carbon number of 2 to 30 such as an oxalic acid, phthalic acid,
trimellitic acid and pyromellitic acid to partially or totally neutralize, or amidate a
remaining amino group andlor imino group; a so-called boron modified compound
formed by reacting the nitrogen containing compound described above with a boric acid
30 to partially or totally neutralize, or amidate a remaining amino group andor imino group;
a sulfur modified compound formed by reacting the nitrogen containing compound
described above with a sulfur compound; a modified compound formed by subjecting the
nitrogen containing compound described above to two or more lunds of modifications
selected from acid modification, boron modification and sulfur modification in
combination; and the like. Among these derivatives, a boron modified compound of
allcenylsuccinimide is excellent in heat resistance property and anti-oxidizing property,
5 and is also effective for improving base number maintaining property and high
temperature detergency in the lubricant oil composition of the invention.
[0052] When an ashless dispersant is contained in the lubricant oil composition of
the invention, its content is normally 0.01 to 20 mass%, preferably 0.1 to 10 mass% based
on the total amount of the lubricant oil composition. With the content of the ashless
10 dispersant in the lubricant oil composition of less than 0.01 mass%, an effect on base
number maintaining property under a high temperature is small, while with that of more
than 20 mass%, the low temperature flow property of the lubricant oil composition hugely
deteriorates, which are both not preferable.
[0053] Also, the lubricant oil composition of the invention is preferable to further
15 contain a radical scavenger type antioxidant. By containing a radical scavenger type
antioxidant, anti-oxidizing property of a lubricant oil composition is further improved,
and therefore base number maintaining property and high temperature detergency in the
invention can further be improved.
[0054] As the above radical scavenger type antioxidant, a phenol-based antioxidant,
20 mine-based antioxidant, metal-based antioxidant and the like which are generally used in
lubricant oils can be used. Further, the above phenol-based antioxidant and amine-based
antioxidant may be used in combination.
[0055] When the radical scavenger type antioxidant is contained in the lubricant oil
composition of the invention, its content is normally not more than 5.0 mass%, preferably
25 not more than 3.0 mass%, further preferably not more than 2.5 mass% based on the total
amount of the lubricant oil composition. When the content of the radical scavenger type
antioxidant is more than 5.0 mass%, a sufficient anti-oxidizing property corresponding to
the content cannot be obtained, which is not preferable. On the other hand, the content
of the radical scavenger type antioxidant is, in order to further improve the base number
30 maintaining property and the high temperature detergency in a lubricant oil deterioration
process, preferably not less than 0.1 mass%, more preferably not less than 1 mass% based
on the total amount of the lubricant oil composition.
[0056] To the lubricant oil composition of the invention, in order to fnrther improve
its performance, an optional additive which is generally used in lubricant oils depending
on its purpose can be added. Such an additive can include, for example, an additive such
as anti-wear additive, friction modifier, viscosity index improver, anti-corrosive additive,
anti-rust additive, anti-emulsifying additive, metal deactivating additive, anti-foaming
additive and coloring additive, and the like.
5 [0057] As the above anti-wear additive, a phosphorous compound or sulfur
conlpound can be used. Although zinc carbyldithiophosphate is a representative
example as the phosphorous compound, other than that, a phosphate or phosphite
containing no sulfur, and a metal salt thereof are also preferably used. Moreover, the
sulfur compound includes, for example, a sulfur containing compound such as a disulfide,
10 sulfwized olefin, sulfurized grease, metal dithiophosphate salt (zinc salt, molybdenum
salt, etc.), metal dithiocarbamate salt (zinc salt, molybdenum salt, etc.), dithiophosphate
ester and derivative thereof (reaction product with olefin cyclopentadiene,
(methy1)methacrylic acid, propionic acid and the like; an addition product at a position
is preferable in the case of a propionic acid), hithiophosphate ester and dithiocarbamate
15 ester, and the like. While they can normally be contained within a range of 0.005 to 5
mass% unless they largely deteriorate the performance of the lubricant oil composition of
the invention, the content is preferably not more than 0.1 mass%, more preferably not
more than 0.05 mass % as a sulfur conversion value, in terms of low sulfurization and
long drain property.
20 [0058] As the above friction modifier, an optional compound which is nornlally used
as a friction modifier for lubricant oils can be used, and for example, a molybdenumbased
friction modifier such as molybdenum disulfide, molybdenum dithiocarbamate,
molybdenum dithiophosphate and molybdenum mine complex can be used within a
range having no influence on an exhaust gas treatment apparatus as a composition. Also,
25 an ashless friction modifier such as an amine compound, fatty acid ester, fatty acid amide,
fatty acid, aliphatic alcohol, aliphatic ether, hydrazide (oleyl hydrazide, etc.),
semicarbazide, urea, weide and biuret, having at least one alkyl group or alkenyl group
with a carbon number of 6 to 30, particularly linear dcyl group or linear allcenyl group
with a carbon number of 6 to 30 within a molecule, and the like are included. The
30 content of these frictionmodifiers is normally 0.1 to 5 mass%.
[0059] The above viscosity index improver, specifically, includes a so-called nondispersed
type viscosity index improver such as a polymer or copolymer of one lund or
two or more kinds of monomers selected from various methacrylate esters or
hydrogenated product thereof, or a so-called dispersed type viscosity index improver
having various methacrylate esters further containing a nitrogen compound
copolymerized, a non-dispersed type or dispersed type ethylene-a-olefin copolymer (as
a-olefin, propylene, 1-butene, 1-pentene, and the like can be exemplified) or hydride
thereof, polyisobutylene or a hydrogenated product thereof, a hydride of a styrene-diene
5 copolymer, a styrene-maleic anhydride ester copolymer, polyallylstyrene, and the like.
[0060] The molecular weight of the above viscosity index improver is preferable to
be selected by considering shear stability. Specifically, the number average molecular
weight of the viscosity index improver is, for example, normally 5,000 to 1,000,000,
preferably 100,000 to 900,000 in the case of dispersed type and non-dispersed type
10 polymethacrylates, normally 800 to 5,000, preferably 1,000 to 4,000 in the case of
polyisobutylene or hydride thereof, normally 800 to 500,000, preferably 3,000 to 200,000
in the case of an ethylene-a-olefin copolymer or hydride thereof.
[0061] Moreover, among the above viscosity index improvers, when an ethylene-ccolefin
copolymer or hydride thereof is used, a lubricant oil composition particularly
15 excellent in shear stability can be obtained. In the lubricant oil composition of the
invention, one kind or two or more ltinds of compounds optionally selected from the
above viscosity index improvers can be contained in an optional amount. The content of
the viscosity index improver is normally 0.1 to 20 mass% based on the lubricant oil
composition.
20 [0062] The above anti-corrosive additive includes, for example, benzotriazole-based,
tolyltriazole-based, thiadiazole-based and imidazole-based compounds, and the like.
[0063] The above anti-rust additive includes, for example, petroleum sulfonate,
alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenylsuccinate ester, polyhydric
alcohol ester, and the like.
25 [0064] The above anti-emulsifying additive includes, for example, a polyalkylene
glycol-based nonionic surfactant such as a polyoxyethylene alkylether, polyoxyethylene
alkylphenylether and polyoxyethylene alkylnaphthylether, and the like.
[0065] The above metal deactivating additive includes, for example, an imidazoline
or pyrimidine derivative, allcylthiadiazole, mercaptobenzoihiazole, benzotriazole or a
30 derivative thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,sbisdialkyldithiocarbamate,
2-(alkyldithio)benzoimidazole, P-(0-
carboxybenzylthio)propionitrile, and the like.
[0066] The above anti-foaming additive includes, for example, silicone,
fluorosilicone, fluoroalkylether, and the like.
[0067] When these additives are contained in the lubricant oil composition of the
invention, the content is normally selected within arange of 0.005 to 5 mass% for the
anti-corrosive additive, anti-rust additive and anti-emulsifying additive, 0.005 to 1 mass%
for the metal deactivating additive, 0.0005 to 1 mass% for the anti-foaming additive.
5 EXAMPLES
[0068] Although the invention will be further specifically described based on
Examples and Comparative Examples below, the invention is not limited to the following
examples.
[0069] In the Examples and Comparative Examples below, the friction reducing
10 effect was evaluated by using a TE77 reciprocating friction testing machine manufactured
by Phoenix Tribology (here, the test plate has a material of BS4659 and a shape of 58 rnm
length x 38 mm width x 4 mm thickness, and the test cylinder pin has a material of ENlA
and a shape of 6 mm diameter x 16 mm length), running in at a stroke of 15 mm, 20 Hz,
an oil temperature of 150°C and a load of 300 N for 30 minutes, and then measuring the
15 friction coefficient at a stroke of 15 mm, 1 Hz, an oil temperature of 150°C and a load of
200 N.
[0070] Characteristics of base oils used in the Examples and Comparative Examples
are shown in Table 1, and characteristics of metal salicylate-based detergents used in the
Examples and Comparative Examples are shown in Table 2. It should be noted that in
20 Tables 3 to 6, the amount of a base oil is the content ratio in the base oil, while the
amount of salicylate is the content based on the total amount of the composition.
100711 [Table I1
I1 Base Oil A-1 1 Base Oil A-2 Base Oil A 3 Base Oil A-4
76.16 93.86
[0072] [Table 21
5 [0073] [Examples 1 to 6 and Comparative Examples 1 to 21
Alkyl ChChain Length
(Cxbon Number)
Salicylate B-1
Lubricant oil compositions with formulations shown in Table 3 were prepared
and measured for the friction coefficient.
Base Number @N)
(mgImwg)
20-30
Salicylate B-2
Metal Ratio
320
Ca Content
(mass%)
14-18
7.3 11.4
280 14.9 10.0

[0075] Table 3 shows the influence of the sulfur content of a base oil in Examples 1
to 6 and Comparative Examples 1 to 2. From Table 3, it is clear that when the sulfur
content of a base oil is not less than 0.03 mass%, the friction coefficient becomes small.
[0076] [Examples 3,7 and 8, and Comparative Example 31
5 Lubricant oil compositions with formulations shown in Table 4 were prepared
and measured for the friction coefficient.
[0077] [Table 41
[0078] Table 4 shows the influence of the ratio between the aromatic content (%CA)
10 and the sulfur content (S) of a base oil in Examples 3,7 and 8, and Comparative Example
3. From Table 4, it is clear that when the %CAIS of a base oil is not more than 30, the
friction coefficient becomes small.
[0079] [Examples 6,9 and 10, and Comparative Examples 1 and 4 to 71
Lubricant oil compositions with formulations shown in Table 5 were prepared
15 and measured for the friction coefficient.
Sulfur Content of Base Oil (S)
%CAIS of Base Oil
Friction Coefficient
mass%
200N 1Hz
0.15
11
0.064
0.15
25
pp
0.065
---0.15 -
29
0.068
0.15
36
0.074

[0081] Table 5 shows the influence of the calcium amount of a lubricant oil
composition in Examples 6,9 and 10, and Comparative Examples 1 and 4 to 7. From
Examples 6,9 and 10, and Comparative Example 4 in Table 5, it is clear that when the
5 sulfur content of a base oil is not less than 0.03 mass%, a lubricant oil composition with a
smaller calcium amount has a lower friction coefficient.
[0082] [Examples 6 and 1 I]
Lubricant oil compositions with formulations shown in Table 6 were prepared
and measured for the friction coefficient.
10 [0083] [Table 61
[0084] Table 6 shows the influence of the alkyl chain length of the metal salicylate
based detergent (B) in Examples 6 and 11. From Table 6, it is clear that the metal
salicylate-based detergent (B) has a higher friction reducing effect with a longer alkyl
15 chain length.
INDUSTRIAL APPLICABILITY
[0085] The lubricant oil composition of the invention can be used as a general
lubricant oil, can preferably be used in petrol engines, diesel engines, gas engines, and the
like for two wheeled vehicles, four wheeled vehicles, power generation, cogeneration and
20 the like, and is also useful in various engines for ships and outboard engines.
[0086] Moreover, the lubricant oil composition of the invention can also preferably
be used as lubricant oils requiring friction reduction, for example, lubricant oils for drive
systems such as automatic or manual transmissions, and lubricant oils such as grease, wet
type brake oil, hydraulic oil, turbine oil, compressor oil, bearing oil and refrigerator oil.

CLAIMS
1. A lubricant oil composition containing:
a base oil (A), wherein a sulfur content is not less than 0.03 mass%> and a
mass ratio [%CA (mass%)/sulfur content (mass%)] between an aromatic content (%CA)
and the sulfur content is not more than 30, and;
a metal salicylate-based detergent (B) in not more than 3 mass% as an alkali
metal or alkali earth metal amount based on the total amount of the composition.
2. A lubricant oil composition according to Claim 1, wherein a carbon
number of an alkyl chain of a soap group of the metal salicylate-based detergent (B) is not
less than 10 as an average.
3. A lubricant oil composition according to Claim 1 or 2, wherein the metal
salicylate-based detergent (B) is an overbased calcium carbonate salicylate.
4. A lubricant oil composition according to any one of Claims 1 to 3, being
a lubricant oil for an internal combustion engine.
5. A method for improving a fuel saving property of an internal combustion
engine by using a lubricant oil composition according to any one of Claims 1 to 3.