Technical Field
[0001] The present invention relates to a lubricant composition, and more specifically,
to a lubricant composition having low viscosity and has a long metal fatigue life,
while being excellent in low-temperature fluidity and oxidation stability, thereby
being particularly suitable as a lubricant for automobile transmissions or the like.
Background Art
[0002] Energy savings, that is, fuel savings in, for example, construction machines, agricultural
machines and automobiles have recently become urgent matters with the advent of the
need to cope with environmental issues, so an apparatus such as an engine, a transmission,
a final reduction gear, a compressor, or a hydraulic systemhas been strongly requested
to contribute to the energy savings. Accordingly, a lubricant to be used in any such
apparatus has been requested to reduce the stirring resistance or frictional resistance
of the apparatus to a larger extent than a conventional lubricant does.
For example, a reduction in viscosity of a lubricant is one method of achieving fuel
savings in each of the transmissions and the final reduction gears. Of the transmissions,
an automatic transmission or continuously variable transmission for automobiles has,
for example, a torque converter, a wet clutch, a gear bearing mechanism, an oil pump,
and a hydraulic control mechanism, and a manual transmission or final reduction gear
has a gear bearing mechanism. A reduction in viscosity of a lubricant to be used in
any such transmission reduces the stirring resistance and frictional resistance of,
for example, each of the torque converter, the wet clutch, the gear bearing mechanism,
and the oil pump, and improves the efficiency of power transmission, thereby enabling
an improvement in fuel efficiency of an automobile.
[0003] However, a lubricant with its viscosity reduced is apt to be lost by evaporation
particularly when used in a high-humidity environment. Moreover, a problem such as
an increase in coefficient of friction of a film composed of the lubricant arises
in association with the reduction in viscosity. As a result, the lubricant has a significantly
reduced fatigue life to cause seizing or the like, so a transmission or the like may
undergo malfunctions. In particular, when a phosphorus-based extreme pressure agent
is blended for improving the extreme-pressure property of a low-viscosity oil, the
fatigue life of the oil remarkably deteriorates, so it is generally difficult to reduce
the viscosity of the oil.
For example, a composition obtained by the following procedure has been disclosed
(see, for example, Patent Documents 1 and 2):
a conventional transmission oil for automobiles is blended with, for example, a synthetic
oil-based lubricant base oil and/or a mineral oil-based lubricant base oil, an anti-wear
agent, an extreme pressure agent, a metal-based detergent, an ashless dispersant,
a friction adj ustor, or a viscosity index improver with the amount of any such additive
optimized so that the composition to be obtained may be able to maintain various properties
such as a transmission characteristic for a long time period. However, no investigation
has been conducted on an influence of any such composition on the fatigue life of
a lubricant when the viscosity of the lubricant is reduced.
Disclosure of the Invention
Problems to be solved by the Invention
[0005] The present invention has been made in view of such circumstances, and an object
of the present invention is to provide a lubricant composition having low viscosity
and a long metal fatigue life, while being excellent in low-temperature fluidity and
oxidation stability, and hence is particularly suitable as a lubricant for automobile
transmissions.
Means for solving the Problems
[0006] The inventors of the present invention have made extensive studies with a view to
developing a lubricant composition having the foregoing excellent performance. As
a result, the inventors have found that the object can be achieved by blending a base
oil having specific properties with an ethylene/α-olefin copolymer having a molecular
weight in a specific range at a predetermined ratio. The present invention has been
completed on the basis of such finding.
That is, the present invention provides:
- (1) a lubricant composition including: a lubricant base oil; and 0. 5 to 10 mass%
of (A) an ethylene/α-olefin copolymer having a number average molecular weight of
2,800 to 8, 000, in which the lubricant base oil used here has a kinematic viscosity
at 100°C of 1.5 to 40 mm2/s, a viscosity index of 100 or more, a pour point of -25°C or lower, and a sulfur
content of 0.01 mass% or less;
- (2) the lubricant composition according to the item (1), further including 0.01 to
2. 0 mass% of (B) a phosphorus-based extreme pressure agent and/or a sulfur-based
extreme pressure agent, the component (B) having a total sulfur content of 0.15 mass%
or less;
- (3) the lubricant composition according to the item (1) or (2), further including
(C) at least one kind of an additive selected from an antioxidant, another extreme
pressure agent, a wear-resisting agent, an oiliness agent, a detergent, a dispersant,
and a pour point depressant; and
- (4) the lubricant composition according to any one of the items (1) to (3), in which
the lubricant composition is used as a lubricant for automobile transmissions.
[0007] According to the present invention, there can be provided a lubricant composition
having low viscosity and a long metal fatigue life, while being excellent in low-temperature
fluidity and oxidation stability, and hence is particularly suitable as a lubricant
for automobile transmissions or the like.
Best Mode for carrying out the Invention
[0008] In a lubricant composition of the present invention, there is used a base oil having
the following properties.
The base oil must have a kinematic viscosity at 100°C in the range of 1.5 to 40 mm
2/s. When the kinematic viscosity is 1.5 mm
2/s or more, the evaporation loss of the lubricant composition is small, so an improving
effect on fuel efficiency canbe obtained. Meanwhile, when the kinematic viscosity
is 40 mm
2/s or less, a power loss due to the viscous resistance of the lubricant composition
does not become very large, so the improving effect on fuel efficiency can be similarly
obtained. The kinematic viscosity is preferably 2 to 25 mm
2/s, or particularly preferably 2 to 10 mm
2/s.
The base oil must have a viscosity index of 100 or more and a pour point of -25°C
or lower. When the viscosity index is 100 or more, a change in viscosity of the lubricant
composition due to a temperature change is small. The viscosity index is preferably
105 or more, or more preferably 110 or more. In addition, when the pour point is -25°C
or lower, the lubricant composition to be obtained has sufficient fluidity even in
a low-temperature environment. The pour point is preferably -30°C or lower, or more
preferably -40°C or lower.
It should be noted that the kinematic viscosity and the viscosity index are each a
value measured in accordance with JIS K 2283, and the pour point is a value measured
in accordance with JIS K 2265.
In addition, the base oil must have a sulfur content of 0.01 mass% or less. When the
sulfur content is 0.01 mass% or less, the oxidation stability of the lubricant composition
to be obtained becomes good. It should be noted that the sulfur content is a value
measured in accordance with JIS K 2541.
[0009] The kind of the base oil is not particularly limited, and each of a mineral oil and
a synthetic oil can be used as the base oil. Here, any one of the various conventionally
known mineral oils can be used as the mineral oil, and examples of the mineral oil
include a paraffin base mineral oil, an intermediate base mineral oil, and a naphthene
base mineral oil. Specific examples of the mineral oil include a light neutral oil,
medium neutral oil, heavy neutral oil, or bright stock obtained by solvent refining,
hydrogenation refining, or the like, and a mineral oil obtained by the isomerization
of a wax.
In addition, any one of the various conventionally known synthetic oils can be also
used as the synthetic oil, and examples of the synthetic oil include poly α-olefin,
polybutene, polyol ester, dibasic acid ester, phosphate, polyphenyl ether, alkyl benzene,
alkyl naphthalene, polyoxyalkylene glycol, neopentyl glycol, silicone oil, trimethylol
propane, and pentaerythritol, and further include hindered ester. Those base oils
may be used alone or in combination of two or more kinds. A mineral oil and a synthetic
oil may be used in combination.
[0010] The lubricant composition of the present invention has the feature of containing
the base oil having the foregoing properties and 0.5 to 10 mass% of (A) an ethylene/α-olefin
copolymer having a number average molecular weight of 2,800 to 8,000.
The ethylene/α-olefin copolymer to be used as the component (A) in the lubricant composition
of the present invention has a number average molecular weight in the range of 2,800
to 8,000. When the number average molecular weight is 2, 800 ormore, an improving
effect on the viscosity index of the lubricant composition to be obtained is exerted.
Meanwhile, when the number average molecular weight is 8,000 or less, the shear stability
of the lubricant composition to be obtained becomes good. The number average molecular
weight is preferably 3,000 to 7,000 from the viewpoints of the improving effect on
the viscosity index and the impartment of good shear stability.
It should be noted that the number average molecular weight is a value measured by
vapor pressure osmometry.
As the α-olefin constituting the ethylene/α-olefin copolymer, an ethylene/α-olefin
copolymer having carbon atoms of preferably 3 to 20, or more preferably 3 to 10 is
used. Examples of the α-olefin include propylene, 1-butene, isobutene, 1-pentene,
1-hexene, 1-octene, and 1-decene. One kind of the α-olefin may be used or two or more
kinds of the α-olefins may be used in combination. Particularly suitable is propylene
in terms of the performance of the composition.
[0011] In addition, the content of an ethylene unit in the ethylene/α-olefin copolymer is
preferably 15 to 85 mol%, or more preferably 20 to 80 mol% in terms of the performance
of the composition. The manner in which the ethylene unit and the α-olefin are copolymerized
is not particularly limited, and the copolymer may be either a random copolymer or
a block copolymer.
In the lubricant composition of the present invention, one kind of the ethylene/α-olefin
copolymer may be used as the component (A), or two or more kinds of the ethylene/α-olefin
copolymers may be used in combination as the component (A). The component (A) is a
component to be blended into the base oil for providing the lubricant composition
of the present invention with low viscosity, excellent low-temperature fluidity and
oxidation stability, and a long metal fatigue life.
Therefore, the content of the component (A) is 0.5 to 10 mass%, preferably 0.5 to
6 mass%, or more preferably 0.5 to 4.5 mass% with respect to the total amount of the
composition from the viewpoints of the foregoing properties.
[0012] A phosphorus-based extreme pressure agent and/or a sulfur-based extreme pressure
agent can be further incorporated as a component (B) into the lubricant composition
of the present invention.
Examples of the phosphorus-based extreme pressure agent include phosphate, acidic
phosphate, acidic phosphate amine salt, phosphite, acidic phosphite, and acidic phosphite
amine salt.
[0013] As the triphosphate, there are given triaryl phosphate, trialkyl phosphate, trialkylaryl
phosphate, triarylalkyl phosphate, and trialkenyl phosphate, and examples thereof
inclue triphenyl phosphate, tricresyl phosphate, benzyldiphenyl phosphate, ethyldiphenyl
phosphate, tributyl phosphate, ethyldibutyl phosphate, cresyldiphenyl phosphate, dicresylphenyl
phosphate, ethylphenyldiphenyl phosphate, di(ethylphenyl)phenyl phosphate, propylphenyldiphenyl
phosphate, di(propylphenyl)phenyl phosphate, triethylphenyl phosphate, tripropylphenyl
phosphate, butylphenyldiphenyl phosphate, di(butylphenyl)phenyl phosphate, tributylphenyl
phosphate, trihexyl phosphate, tri(2-ethylhexyl)phosphate, tridecyl phosphate, trilauryl
phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, and
trioleyl phosphate.
[0014] Examples of the acidic phosphate include di-2-ethylhexyl acid phosphate, didecylacid
phosphate, didodecyl acid phosphate (dilauryl acid phosphate), tridecyl acid phosphate,
dioctadecyl acid phosphate (distearyl acid phosphate), and di-9-octadecenyl acid phosphate
(dioleylacid phosphate). Examples of the phosphite include triethyl phosphite, tributyl
phosphite, triphenyl phosphite, tricresyl phosphite, tri(nonylphenyl)phosphite, tri(2-ethylhexyl)phosphite,
tridecyl phosphite, trilauryl phosphite, triisooctyl phosphite, diphenylisodecyl phosphite,
tristearyl phosphite, and trioleyl phosphite.
[0015] Examples of the acidic phosphite include di-2-ethylhexyl hydrogen phosphite, didecyl
hydrogen phosphite, didodecyl hydrogen phosphite (dilauryl hydrogen phosphite), dioctadecyl
hydrogen phosphite (distearyl hydrogen phosphite), di-9-octadecenyl hydrogen phosphite
(dioleyl hydrogen phosphite), and diphenyl hydrogen phosphite.
As the acidic phosphate amine salt and the acidic phosphite amine salt, salts formed
of the above-mentioned acidic phophates and acidic phosphites and the following amines
are exemplified. As the amines, a monosubstituted amine, a disubstituted amine, or
a trisubstituted amine may be used.
[0016] Examples of the monosubstituted amine include butylamine, pentylamine, hexylamine,
cyclohexylamine, octylamine, laurylamine, stearylamine, oleylamine, and benzylamine.
Examples of the disubstituted amine include dibutylamine, dipentylamine, dihexylamine,
dicyclohexylamine, dioctylamine, dilaurylamine, distearylamine, dioleylamine, dibenzylamine,
stearyl monoethanolamine, decyl monoethanolamine, hexyl monopropanolamine, benzyl
monoethanolamine, phenyl monoethanolamine, and tolyl monopropanol. Examples of the
trisubstituted amine include tributylamine, tripentylamine, trihexylamine, tricyclohexylamine,
trioctylamine, trilaurylamine, tristearylamine, trioleylamine, tribenzylamine, dioleyl
monoethanolamine, dilauryl monopropanolamine, dioctyl monoethanolamine, dihexyl monopropanolamine,
dibutyl propanolamine, oleyl diethanolamine, stearyl dipropanolamine, lauryl diethanolamine,
octyl dipropanolamine, butyl diethanolamine, benzyl diethanolamine, phenyl diethanolamine,
tolyl dipropanolamine, xylyl diethanolamine, triethanolamine, and tripropanolamine.
[0017] In addition, as the acidic phosphate amine salt, a salt formed of the acidic monophosphate
and the above-mentioned amine such as monomethyl hydrogen phosphate, monoethyl hydrogen
phosphate, monopropyl hydrogen phosphate, monobutyl hydrogen phosphate, or mono-2-ethylhexyl
hydrogen phosphate can be used.
In the present invention, one kind of the phosphate-based compound may be used or
two or more kinds of the phosphate-based compounds may be used in combination.
[0018] Meanwhile, the sulfur-based extreme pressure agent has only to have the following
characteristics: the agent has a sulfur atom in any one of its molecules, and is dissolved
or uniformly dispersed in the lubricant base oil so as to be capable of exerting extreme-pressure
property or an excellent friction characteristic. Examples of the sulfur-based extreme
pressure agent having such characteristics include sulfurized fats and oils, a sulfurized
fatty acid, a sulfurized ester, a sulfurized olefin, dihydrocarbyl polysulfide, a
thiadiazole compound, a thiophosphoric acid ester (thiophosphite or thiophosphate),
an alkylthiocarbamoyl compound, a thiocarbamate compound, a thioterpene compound,
and a dialkyl thiodipropionate compound. Here, the sulfurized fats and oils can be
obtained by causing sulfur or a sulfur-containing compound and fats and oils (such
as a lard oil, a whale oil, a vegetable oil, and a fish oil) to react with each other,
and the sulfur content of each of the sulfurized fats and oils, which is not particularly
limited, is suitably 5 to 30 mass% in ordinary cases. Specific examples of such fats
and oils include a sulfurized lard, a sulfurized rapeseed oil, a sulfurized castor
oil, a sulfurized soybean oil, and a sulfurized rice bran oil. The sulfurized fatty
acid is, for example, a sulfurized oleic acid. Examples of the sulfurized ester include
sulfurized methyl oleate and sulfurized rice bran fatty acid octyl.
[0019] The sulfurized olefin is, for example, a compound represented by the following general
formula (I):
R
1-S
q-R
2... (I)
where: R
1 represents an alkenyl group having 2 to 15 carbon atoms; R
2 represents an alkyl or alkenyl group having 2 to 15 carbon atoms; and q represents
an integer of 1 to 8.
The compound is obtained by causing an olefin having 2 to 15 carbon atoms or a dimer,
trimer, or tetramer of the olefin and a sulfurizing agent such as sulfur or sulfur
chloride to react with each other, and the olefin is preferably, for example, propylene,
isobutene, or diisobutene.
The dihydrocarvyl polysulfide is, for example, a compound represented by the following
general formula (II):
R
3-S
r-R
4... (II)
where R
3 and R
4 each represent an alkyl group or a cyclic alkyl group having 1 to 20 carbon atoms,
an aryl group having 6 to 20 carbon atoms, an alkyl aryl group having 7 to 20 carbon
atoms, or an aryl alkyl group having 7 to 20 carbon atoms, which may be identical
to or different from each other; and r represents an integer of 1 to 8.
when both R
3 and R
4 are alkyl groups, the compound is referred to as sulfurized alkyl.
Examples of the dihydrocarbyl polysulfide represented by the general formula (II)
preferably include dibenzyl polysulfide, various dinonyl polysulfides, various didodecyl
polysulfides, various dibutyl polysulfides, various dioctyl polysulfides, diphenyl
polysulfide, and dicyclohexyl polysulfide.
[0020] Examples of the thiadiazole compoundpreferably include 2,5-bis(n-hexyldithio)-1,3,4-thiadiazole,
2,5-bis(n-octyldithio)-1,3,4-thiadiazole, 2,5-bis(n-nonyldithio)-1,3,4-thiadiazole,
2,5-bis(1,1,3,3-tetramethylbutyldithio)-1,3,4-thiadiazole, 3,5-bis(n-hexyldithio)-1,2,4-thiadiazole,
3,6-bis(n-octyldithio)-1,2,4-thiadiazole, 3,5-bis(n-nonyldithio)-1,2,4-thiadiazole,
3,5-bis(1,1,3,3-tetramethylbutyldithio)-1,2,4-thiadiazole, 4,5-bis(n-octyldithio)-1,3,4-thiadiazole,
4,5-bis(n-nonyldithio)-1,2,3-thiadiazole, and 4,5-bis(1,1,3,3-tetramethylbutyldithio)-1,2,3-thiadiazole.
[0021] Examples of the thiophosphoric acid ester include alkyl trithiophosphite, aryl or
alkyl aryl thiophosphate, and zinc dilauryl dithiophosphate. Particularly preferred
are lauryl thiophosphite and triphenyl tiophosphate.
Examples of the alkyl thiocarbamoyl compound include bis(dimethyl thiocarbamoyl)monosulfide,
bis(dibutyl thiocarbamoyl)monosulfide, bis(dimethyl thiocarbamoyl) disulfide, bis(dibutyl
thiocarbamoyl)disulfide, bis(diamyl thiocarbamoyl) disulfide, and bis (dioctyl thiocarbamoyl)
disulfide.
[0022] Further, the thiocarbamate compound is, for example, a zinc dialkyldithiocarbamate,
the thioterpene compound is, for example, a product of a reaction between phosphorus
pentasulfide and pinene, and examples of the dialkyl thiodipropionate compound include
dilauryl thiodipropionate and distearyl thiodipropionate. Of those, the thiadiazole
compound or benzyl sulfide is suitable in terms of, for example, extreme-pressure
property, a friction characteristic, and thermal oxidation stability.
One kind of those sulfur-based extreme pressure agents may be used alone, or two or
more kinds of them may be used in combination.
[0023] In the lubricant composition of the present invention, only the phosphorus-based
extreme pressure agent may be used as the component (B), only the sulfur-based extreme
pressure agent may be used as the component (B), or the phosphorus-based extreme pressure
agent and the sulfur-based extreme pressure agent may be used in combination as the
component (B).
The content of the component (B) is typically about 0.01 to 2.0 mass%, or preferably
0.05 to 1.5 mass% with respect to the total amount of the lubricant composition in
terms of, for example, a balance between the effect and economical efficiency of the
component as an extreme pressure agent.
It should be noted that, when the sulfur-based extreme pressure agent is used, from
the viewpoint of corrosion prevention, the amount in which the agent is blended is
preferably adjusted so that the total sulfur content in the composition may be preferably
0.15 mass% or less, or more preferably 0.10 mass% or less.
At least one kind of an additive selected from an antioxidant, another extreme pressure
agent, a wear-resisting agent, an oiliness agent, a detergent dispersant, and a pour
point depressant can be further incorporated as a component (C) into the lubricant
composition of the present invention.
[0024] Examples of the antioxidants include an amine-based antioxidants, phenol-based antioxidants,
and a sulfur-based antioxidants.
Examples of the amine-based antioxidants include:
monoalkyldiphenylamine-based compounds such as monooctyldiphenylamine and monononyldiphenylamine;
dialkyldiphenylamine-based compounds such as 4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine,
4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine,
and 4,4'-dinonyldiphenylamine; polyalkyldiphenylamine-based compounds such as tetrabutyldiphenylamine,
tetrahexyldiphenylamine, tetraoctyldiphenylamine, and tetranonyldiphenylamine; and
naphthylamine-based compounds such as α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine,
pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine,
octylphenyl-α-naphthylamine, and nonylphenyl-α-naphthylamine. Of those, dialkyldiphenylamine-based
compounds are preferable.
[0025] Examples of the phenol-based antioxidant include monophenol-based compounds such
as 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butyl-4-ethylphenol; and diphenol-based
compounds such as 4,4'-methylenebis(2,6-di-tert-butylphenol) and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol).
Examples of the sulfur-based antioxidant include phenothiazine, pentaerythritol-tetrakis(3-laurylthiopropionate),
bis(3,5-tert-butyl-4-hydroxybenzyl)sulfide, thiodiethylenebis(3-(3,5-di-tert-butyl-4-hydroxyphenyl))propio
nate, and 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazine-2-methy lamino)phenol.
Each of these antioxidants may be used alone or two or more of them may be used in
combination. Further, the blending amounts of those antioxidants are typically in
the range of 0. 01 to 10 mass%, or preferably in a range of 0.03 to 5 mass% on the
basis of the total amount of the lubricant composition.
[0026] As other extreme pressure agents, the wear-resisting agents, and the oiliness agents,
there are exemplified organic metal compounds such as zinc dithiophosphate (ZnDTP),
zinc dithiocarbamate (ZnDTC), oxymolybdenum organo phosphorodithioate sulfide (MoDTP),
and oxymolybdenum dithiocarbamate sulfide (MDTC). The blending amount of those is
typically 0.05 to 5 mass%, or preferably 0.1 to 3 mass% based on the total amount
of lubricant composition.
Further, mentioned are oiliness agents including aliphatic saturated and unsaturatedmonocarboxylic
acids such as stearic acids and oleic acids; polymerized fatty acids such as dimer
acids and hydrogenated dimer acids; hydroxy fatty acids such as ricinoleic acids and
12-hydroxystearic acids; aliphatic saturated and unsaturated monohydric alcohols such
as lauryl alcohol and oleyl alcohol; aliphatic saturated and unsaturated monoamines
such as stearylamine and oleylamine; and aliphatic saturated and unsaturated monocarboxylic
acid amides such as lauric acid amide and oleamide.
The preferable blending amount of those oiliness agents is typically in a range of
0.01 to 10 mass%, or particularly preferably in a range of 0.1 to 5 mass% based on
the total amount of lubricant composition.
[0027] Examples of the detergents and the dispersants include:
ashless dispersants such as succinimides, boron-containing succinimides, benzylamines,
boron-containing benzylamines, succinates, and monovalant or bivalent carboxylic amides
typified by fatty acids or succinic acids; and metal-based detergents such as neutral
metal sulfonate, neutral metal phenate, neutral metal salicylate, neutral metal phosphonate,
basic sulfonate, basic phenate, basic salicylate, over-based sulfonate, over-based
salicylate, and over-based phosphonate. The blending amount of those detergent dispersants
is typically 0.1 to 20 mass%, or preferably 0.5 to 10 mass% based on the total amount
of lubricant composition.
For example, a polymethacrylate having a weight average molecular weight of about
50, 000 to 150,000 can be used as the pour point depressant.
[0028] An additive except those described above such as a rust inhibitor, a metal deactivator,
a defoaming agent, or a surfactant can be incorporated into the lubricant composition
of the present invention as desired.
There are used, for example: as the rust inhibitor, alkenyl succinic acid and partial
esters thereof; as the metal corrosion inhibitor, benzotriazole-based, benzimidazole-based,
benzothiazole-based, and thiadiazole-based ones; and as the metal deactivator, benzotriazole,
benzotriazole derivatives, benzothiazole, benzothiazole derivatives, triazole, triazole
derivatives, dithiocarbamate, dithiocarbamate derivatives, imidazole, and imidazole
derivatives. There are used, for example:
as the defoaming agent, dimethyl polysiloxane and polyacrylate; and as the surfactant,
polyoxyethylene alkylphenyl ether.
[0029] The lubricant composition of the present invention has, for example, the following
characteristics: the lubricant composition has low viscosity, is excellent in low-temperature
fluidity and oxidation stability, and has a long metal fatigue life. Accordingly,
the lubricant composition is suitably used as, for example, an oil for transmissions,
power steering oil, shock absorber oil, or engine oil in automobiles, or a gear oil,
hydraulic oil, or bearing oil for automobiles and industries; the lubricant composition
is particularly suitable as an oil for transmissions such as an automatic transmission,
a manual transmission, and a continuously variable transmission in automobiles.
Examples
[0030] Hereinafter, the present invention will be described in more detail with reference
to Examples and Comparative Examples, but is not limited thereto.
It should be noted that the physical properties of a base oil and a lubricant composition
were determined in accordance with the following methods.
<Base oil and lubricant composition>
[0031]
- (1) Kinematic viscosity (40°C, 100°C)
Measurement was performed in accordance with JIS K 2283.
- (2) Viscosity index (VI)
Measurement was performed in accordance with JIS K 2283.
- (3) Sulfur content
Measurement was performed in accordance with JIS K 2541.
<Base oil>
[0032]
(4) Pour point
Measurement was performed in accordance with JIS K 2265.
<Lubricant composition>
[0033]
(5) Low-temperature viscosity (-40°C)
A Brookfield viscosity at -40°C was measured in accordance with ASTM D 2983.
(6) Fatigue life
A fatigue life was measured with a four-ball rolling fatigue tester in the following
manner.
(Bearing)
[0034]
- Material:
- bearing steel
- Test piece:
- ϕ60×5 mm thick
- Steel ball dimensions:
- ϕ3/8 inch (3/8x2.54 cm)
(Test conditions)
[0035]
- Load:
- 147 N
- Rotational speed:
- 2,200 rpm
- Oil temperature:
- 120°C
[0036] A time period required for flaking to occur in the test piece was defined as a fatigue
life, and an L50 (average) was calculated from the results of the test performed six
times.
(7) Oxidation stability
[0037] A test oil was forcedly deteriorated in an ISOT test (150°C) in accordance with JIS
K 2514. The percentage by which the viscosity changed (40°C, 100°C), an increase in
total acid number, a base number, the amount of n-heptane insoluble matter, and an
increase in copper element were measured 144 hours after the deterioration.
[0038] The kinds of the respective components used in the preparation of a lubricant composition
are as shown below.
Base oils A to F
Table 1 shows the properties of the base oils.
[0039] [Table 1]
Table 1
|
Kind |
Properties |
Kinematic viscosity (mm /s) |
Viscosity index |
Pour point (°C) |
Sulfur content (mass%) |
40°C |
100°C |
Base oil |
A |
Hydrogenation-r efined base oil |
9.79 |
2.686 |
113 |
-42.5 |
0.01> |
B |
Hydrogenation-r efined base oil |
7.976 |
2.252 |
83 |
-10.0 |
0.01> |
C |
Hydrogenation-r efined base oil |
20.54 |
4.412 |
127 |
-22.5 |
0.01> |
D |
Hydrogenation-r efined base oil |
408.8 |
30.86 |
107 |
-15.0 |
0.01> |
E |
Solvent-refined base oil |
458.6 |
30.65 |
96 |
12.5 |
0.43 |
F |
Solvent-refined base oil |
745.8 |
42.52 |
98 |
15.0 |
0.51 |
[0040] thylene/α-olefin copolymer I
A product available under the trade name "Lucant HC600" from Mitsui Chemicals, the
product having a number average molecular weight of 2,600, a kinematic viscosity at
100°C of 600 mm
2/s, a viscosity index of 240, and a sulfur content of less than 0.1 mass% Ethylene/α-olefin
copolymer II
A product available under the trade name "Lucant HC2000" from Mitsui Chemicals, the
product having a number average molecular weight of 3,700, a kinematic viscosity at
100°C of 2,000 mm
2/s, a viscosity index of 300, and a sulfur content of less than 0.1 mass% Ethylene/α-olefin
copolymer III (including diluent oil having a concentration of 50 mass%)
A product available under the trade name "Lucant HS4010M" from Mitsui Chemicals, the
product having a number average molecular weight of 6,600, a kinematic viscosity at
100°C of 2,000 mm
2/s, a viscosity index of 335, and a sulfur content of less than 0.1 mass% Viscosity
index improver I
A polymethacrylate-based product available under the trade name "VISCOPLEX 0-050"
fromRomax, the product having a number average molecular weight of 18,000 and a kinematic
viscosity at 100°C of 450 mm
2/s
Viscosity index improver II
[0041] A polymethacrylate-based product available under the trade name "ACLUBE C728" from
Sanyo Chemical Industries, Ltd. , the product having a number average molecular weight
of 45,000 and a kinematic viscosity at 100°C of 852 mm
2/s
Pour point depressant
[0042] A polymethacrylate-based product available under the trade name "ACLUBE C728" from
Sanyo Chemical Industries, Ltd.
Extreme pressure agent: thiadiazole
ATF additive package
A product available under the trade name "Infineum T4261" from Infineum, the product
containing a phosphorus-based extreme pressure agent, a sulfur-based extreme pressure
agent, a detergent dispersant, a friction adjustor, and an antioxidant
[0043] Examples 1 to 4 and Comparative Examples 1 to 6
Lubricant compositions each having the composition shown in Table 2 were prepared,
and were each evaluated for physical properties except oxidation stability. Table
2 shows the results.
The lubricant compositions of Example 1 and Comparative Example 1 were each evaluated
for oxidation stability. Table 3 shows the results.
[0044] [Table 2]
Table 2-1
|
Example |
Comparative Example |
1 |
2 |
3 |
4 |
1 |
Composition (mass%) |
Base oil |
Kind |
A |
A |
A |
A |
B/C |
Content |
84.2 |
84.2 |
83.5 |
84.1 |
35.7/44.2 |
Sulfur content (mass%) |
0,01> |
0.01> |
0.01> |
0.01> |
0.01> |
Ethylene/propylene copolymer |
I |
- |
- |
2.7 |
- |
- |
II |
4.0 |
- |
2.0 |
4.0 |
- |
III |
- |
4.0 |
- |
- |
- |
Viscosity index improver |
I |
- |
- |
- |
- |
- |
II |
- |
- |
- |
- |
8.3 |
Pour point depressant |
0.3 |
0.3 |
0.3 |
0.3 |
0.3 |
Extreme pressure agent |
- |
- |
- |
0.1 |
- |
ATF additive package |
11.5 |
11.5 |
11.5 |
11.5 |
11.5 |
Physical properties |
Sulfur content (mass%) |
0.06 |
0.06 |
0.06 |
0.06 |
0.06 |
Kinematic viscosity (mm2/s) |
40°C |
25 |
26.11 |
26.07 |
24.95 |
33.1 |
100°C |
5.64 |
5.806 |
5.775 |
5.63 |
7.37 |
Viscosity index |
176 |
176 |
174 |
176 |
198 |
Low-temperature viscosity [-40°C] [Brookfield viscosity] |
7,500 |
7,200 |
9,200 |
7,500 |
14,500 |
Fatigue life [L50] (minutes) |
155 |
160 |
162 |
170 |
95 |
[0045] [Table 3]
Table 2-2
|
Comparative Example |
2 |
3 |
4 |
5 |
6 |
Composition (mass%) |
Base oil |
Kind |
A/C |
A/C/D |
A/E |
A/F |
A |
Content |
19.0/66.2 |
50.0/25.2 /10.0 |
69.2/17.0 |
73.5/14.0 |
82.4 |
Sulfur content (mass%) |
0.01> |
0.01> |
0.08 |
0.08 |
0.01> |
Ethylene/propylene copolymer |
I |
- |
- |
- |
- |
5.8 |
II |
- |
- |
- |
- |
- |
III |
- |
- |
- |
- |
- |
Viscosity index improver |
I |
- |
- |
2.0 |
- |
- |
II |
3.0 |
3.0 |
- |
0.7 |
- |
Pour point depressant |
0.3 |
0.3 |
0.3 |
0.3 |
0.3 |
Extreme pressure agent |
- |
- |
- |
- |
- |
ATF additive package |
11.5 |
11.5 |
11.5 |
11.5 |
11.5 |
Physical properties |
Sulfur content (mass%) |
0.06 |
0.06 |
0.14 |
0.14 |
0.06 |
Kinematic viscosity (mm2/s) |
40 °C |
26.46 |
26.61 |
28.06 |
27.24 |
26.37 |
100 °C |
5.729 |
5.682 |
5.762 |
5.690 |
5.828 |
Viscosity index |
167 |
162 |
153 |
156 |
174 |
Low-temperature viscosity [-40 °C] [Brookfield viscosity] |
8, 100 |
9,900 |
17,200 |
19,200 |
11,000 |
Fatigue life [L50] (minutes) |
110 |
135 |
140 |
155 |
140 |
[0046] [Table 4]
Table 3
|
Example 1 |
Comparative Example 5 |
Oxidation stability [ISOT test 150°C, 144h] |
Percentage by which kinematic viscosity changed (%) |
40 °C |
3.0 |
8.2 |
100 °C |
1.5 |
4.5 |
Increase in total acid number (mgKOH/g) |
-0.05 |
0.12 |
Base number (mgKOH/g) |
0.36 |
0.05 |
Amount of n-pentane insoluble matter (mass%) |
0.01> |
0.05 |
Increase in Cu element (ppm) |
26 |
35 |
[0047] As can be seen from Table 2, each of the lubricant compositions of the present invention
(Examples 1 to 4) has a low-temperature viscosity (-40°C) of less than 10, 000 and
a fatigue life [L50] in excess of 150 minutes, so each of them has good low-temperature
fluidity anda longmetal fatigue life. In contrast, each of the lubricant compositions
of Comparative Examples 1 to 4 and Comparative Example 6 has a fatigue life [L50]
of less than 150 minutes, so each of them has a short metal fatigue life. Moreover,
each of the lubricant compositions of Comparative Examples 1, 4, and 6 has a low-temperature
viscosity (-40°C) in excess of 10,000, so each of them is poor in low-temperature
fluidity.
Meanwhile, the lubricant composition of Comparative Example 5 has a fatigue life [L50]
in excess of 150 minutes, so the lubricant composition has a long metal fatigue life.
However, the lubricant composition has extremely bad low-temperature fluidity. In
addition, as can be seen from Table 3, the lubricant composition is inferior in oxidation
stability to the lubricant composition of Example 1.
Industrial Applicability
[0048] The lubricant composition of the present invention has the following characteristics:
the lubricant composition has low viscosity, is excellent in low-temperature fluidity
and oxidation stability, and has a long metal fatigue life. Accordingly, the lubricant
composition is suitably used as, for example, an oil for transmissions, power steering
oil, shock absorber oil, or engine oil in automobiles, or a gear oil, hydraulic oil,
or bearing oil for automobiles and industries.