U.S. patent application number 12/026670 was filed with the patent office on 2008-06-12 for lubricating oil composition.
This patent application is currently assigned to NIPPON OIL CORPORATION. Invention is credited to Hitoshi KOMATSUBARA, Shigeki MATSUI.
Application Number | 20080139424 12/026670 |
Document ID | / |
Family ID | 37757664 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080139424 |
Kind Code |
A1 |
KOMATSUBARA; Hitoshi ; et
al. |
June 12, 2008 |
LUBRICATING OIL COMPOSITION
Abstract
The present invention provides a lubricating oil composition
which has excellent anti-wear properties for a metal pulley and a
metal belt and initial anti-shudder properties and can retain the
anti-shudder properties for a long period of time, suitable for use
in a continuously variable transmission with a slip-controlled wet
clutch and a metal belt. The lubricating oil composition comprises
a lubricating base oil, (A) an alkylsalicylic acid metal salt
and/or an (overbased) basic salt thereof, wherein the component
ratio of the monoalkylsalicylic acid metal salt is from 85 to 100
percent by mole, the component ratio of the dialkylsalicylic acid
metal salt is from 0 to 15 percent by mole and the component ratio
of the 3-alkylsalicylic acid metal salt is from 40 to 100 percent
by mole; (B) a specific nitrogen compound; and (C) a
phosphorus-containing anti-wear agent.
Inventors: |
KOMATSUBARA; Hitoshi;
(Yokohama-shi, JP) ; MATSUI; Shigeki;
(Yokohama-shi, JP) |
Correspondence
Address: |
PANITCH SCHWARZE BELISARIO & NADEL LLP
ONE COMMERCE SQUARE, 2005 MARKET STREET, SUITE 2200
PHILADELPHIA
PA
19103
US
|
Assignee: |
NIPPON OIL CORPORATION
Yokohama-shi
JP
|
Family ID: |
37757664 |
Appl. No.: |
12/026670 |
Filed: |
February 6, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2006/316274 |
Aug 14, 2006 |
|
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12026670 |
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Current U.S.
Class: |
508/273 ;
508/421; 508/460; 508/518 |
Current CPC
Class: |
C10M 2215/28 20130101;
C10N 2030/00 20130101; C10N 2010/02 20130101; C10N 2030/74
20200501; C10M 2223/041 20130101; C10M 2219/104 20130101; C10M
2207/144 20130101; C10M 2203/10 20130101; C10N 2030/76 20200501;
C10N 2040/04 20130101; C10M 2223/04 20130101; C10M 2207/146
20130101; C10M 2229/041 20130101; C10M 2219/106 20130101; C10M
2215/064 20130101; C10M 2207/262 20130101; C10M 163/00 20130101;
C10M 2223/045 20130101; C10M 2223/049 20130101; C10N 2040/042
20200501; C10N 2040/045 20200501; C10N 2030/06 20130101; C10M
2219/108 20130101; C10M 2223/047 20130101; C10M 2223/042 20130101;
C10M 2223/043 20130101; C10N 2030/52 20200501; C10M 2219/046
20130101; C10M 2203/1006 20130101; C10N 2010/04 20130101; C10M
2207/026 20130101; C10N 2060/14 20130101; C10M 2203/1006 20130101;
C10M 2203/1006 20130101; C10M 2207/144 20130101; C10M 2207/144
20130101; C10M 2207/146 20130101; C10M 2207/146 20130101; C10M
2207/262 20130101; C10M 2207/262 20130101; C10M 2219/046 20130101;
C10N 2010/04 20130101; C10M 2219/046 20130101; C10N 2010/04
20130101 |
Class at
Publication: |
508/273 ;
508/460; 508/518; 508/421 |
International
Class: |
C10M 141/10 20060101
C10M141/10 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 15, 2005 |
JP |
2005-235550 |
Claims
1. A lubricating oil composition suitable for a transmission with a
slip-controlled wet clutch, comprising: a lubricating base oil; (A)
an alkylsalicylic acid metal salt and/or an (overbased) basic salt
thereof, wherein the component ratio of the monoalkylsalicylic acid
metal salt is from 85 to 100 percent by mole, the component ratio
of the dialkylsalicylic acid metal salt is from 0 to 15 percent by
mole and the component ratio of the 3-alkylsalicylic acid metal
salt is from 40 to 100 percent by mole; (B) a nitrogen compound
represented by formula (1) below; and (C) a phosphorus-containing
anti-wear agent: ##STR00004## wherein R.sup.1 is a straight-chain
or branched alkyl group having 1 to 30 carbon atoms, R.sup.2 is
hydrogen or a straight-chain or branched alkyl group having 1 to 24
carbon atoms, and a and b are each independently an integer of 1, 2
or 3.
2. The lubricating oil composition according to claim 1, further
comprising a friction modifier.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to lubricating oil
compositions suitable for a transmission equipped with a
slip-controlled wet clutch and more specifically to transmission
lubricating oil compositions suitable for a continuously variable
transmission equipped with a slip-controlled wet clutch and a metal
belt, in particular a wet starting clutch, which compositions have
excellent anti-wear properties for the metal pulleys and metal belt
of the transmission and excellent initial anti-shudder properties
and can retain the anti-shudder properties for a long period of
time because the compositions contain a specific salicylate
detergent.
BACKGROUND OF THE INVENTION
[0002] Recent automatic transmissions have been demanded to be
light and small and sought to be improved in power transmission
capability in connection with the increased power output of the
engines with which the transmissions are used in combination.
Therefore, lubricating oils used for such transmissions have been
required to have enhanced lubricating properties, i.e., properties
to prevent wear on the surfaces of bearings and gears. Metal belt
type continuously variable transmissions have been also increased
in torque transmitted between the metal pulleys and metal belt due
to the increased power output of the engines. Therefore, the
lubricating oil used for such transmissions have been required to
have higher torque capacity and properties to prevent wear between
the metal surfaces of the metal pulleys and metal belt.
[0003] There are some automatic transmissions or continuously
variable transmissions that control the lock-up clutch built in the
torque converter to be slipped at a low velocity (slip lock-up
control). These transmissions have been improved with the slip
lock-up control so that the drive feeling can be improved by
absorbing a torque variation and the engine torque can be
transmitted to the transmission mechanism efficiently. Some of the
continuously variable transmissions are provided with a wet
starting clutch which is initially allowed to slip and then coupled
so as to start the vehicle smoothly from the halt, that is a
so-called slip control. Lubricating oils used for the transmissions
wherein slip control for the lock-up clutch or starting clutch is
carried out are required to have excellent initial anti-shudder
properties and be able to retain the anti-shudder properties for a
long period of time.
[0004] Under these circumstances, transmission lubricating oil
compositions are disclosed, in which a friction modifier, a
metallic detergent, an ashless dispersant, and an anti-wear agent
are optimally added so as to retain the friction characteristics of
a lock-up clutch in a good condition and provide long-lasting
initial anti-shudder properties (see Patent Documents 1 to 6
below).
[0005] For example, Patent Document 1 discloses a transmission
lubricating oil composition comprising a specific calcium
salicylate, an SP-based extreme pressure additive, a specific
succinimide and a boron-containing ashless dispersant, each in a
specific amount, which composition exhibits excellent properties
such as excellent anti-shudder properties and long-lasting fatigue
life. Patent Document 2 discloses a continuously variable
transmission lubricating oil composition containing an organic acid
metal salt with a specific structure, an anti-wear agent, and a
boron-containing succinimide, as essential components, which
composition has both higher friction coefficient between metals and
anti-shudder properties for a slip control mechanism. Patent
Document 3 discloses a long-lasting continuously variable
transmission lubricating oil composition comprising calcium
salicylate, a phosphorus-containing anti-wear agent, a friction
modifier, and a dispersant type viscosity index improver, which
composition has both a higher friction coefficient between metals
and anti-shudder properties for a slip control mechanism. Patent
Document 4 discloses a lubricating oil composition comprising a
dithiocarbamate compound, a condensate of a branched fatty acid
having 8 to 30 carbon atoms and amine, and an aminic anti-oxidant,
which composition has excellent and long-lasting anti-shudder
properties. Patent Document 5 discloses an automatic transmission
fluid composition comprising calcium sulfonate, phosphorus acid
esters and further a sarcosine derivative or a reaction product of
a carboxylic acid and amine, which composition has long-lasting
anti-shudder properties for a slip lock-up mechanism and
long-lasting properties to prevent scratch noise in a belt type
continuously variable transmission. Patent Document 6 discloses an
automatic transmission fluid composition comprising a specific
alkaline earth metal sulfonate in a specific amount, which
composition is excellent in oxidation stability as a fluid used for
an automatic transmission with a slip control mechanism and has
long-lasting anti-shudder properties.
[0006] However, as the results of studies conducted by the
inventors of the present invention, it was found that the use of a
sulfonate detergent as a metallic detergent was still insufficient
to improve initial anti-shudder properties, and in particular when
a monoalkyl type salicylate detergent was used, the resulting
lubricating oil composition was excellent in initial anti-shudder
properties but was likely to cause wear or elution of metal ions
such as iron ion in a continuously variable transmission wherein
the metal pulleys contact the metal belt under severe conditions
and was difficult in retaining anti-shudder properties even though
blended with the friction modifiers as mentioned in the above
patent documents.
[0007] Patent Document 7 describes that since the monoalkyl type
salicylate detergent inhibits the anti-wear effect of a
phosphorus-containing additive, the use of a specific amide
compound in combination therewith can enhance anti-wear properties
for the valve train of an internal combustion engine. However,
Patent Document 7 does not disclose or even suggest any solution
for preventing wear in a transmission with a slip controlled type
wet clutch, particularly a continuously variable transmission
wherein the metal pulleys contact the metal belt under severe
conditions or preventing shudder peculiar to the slip controlled
type wet clutch for a long period of time. [0008] (1) Patent
Document 1: Japanese Patent Laid-Open Publication No. 2003-113391
[0009] (2) Patent Document 2: Japanese Patent Laid-Open Publication
No. 2001-323292 [0010] (3) Patent Document 3: Japanese Patent
Laid-Open Publication No. 2000-355695 [0011] (4) Patent Document 4:
Japanese Patent Laid-Open Publication No. 11-50077 [0012] (5)
Patent Document 5: Japanese Patent Laid-Open Publication No.
10-306292 [0013] (6) Patent Document 6: Japanese Patent Laid-Open
Publication No. 10-25487 [0014] (7) Patent Document 7: Japanese
Patent Laid-Open Publication No. 2004-67812
DISCLOSURE OF THE INVENTION
[0015] The present invention has an object to provide a lubricating
oil composition suitable for a continuously variable transmission
with a slip-controlled wet clutch, metal pulleys and a metal belt,
particularly such a transmission with a slip-controlled starting
clutch, which composition has excellent anti-wear properties for
the metal pulley and metal belt and initial anti-shudder properties
and can retain the anti-shudder properties for a long period of
time.
[0016] As the results of extensive studies conducted by the
inventors, the present invention was accomplished on the basis of
the finding that the above object was able to be achieved using a
specific salicylate detergent, a specific nitrogen compound and a
phosphorus-containing anti-wear agent in combination.
[0017] That is, according to the present invention, there is
provided a lubricating oil composition suitable for a transmission
with a slip-controlled wet clutch, which composition comprises a
lubricating base oil, (A) an alkylsalicylic acid metal salt and/or
an (overbased) basic salt thereof, wherein the component ratio of
the monoalkylsalicylic acid metal salt is from 85 to 100 percent by
mole, the component ratio of the dialkylsalicylic acid metal salt
is from 0 to 15 percent by mole and the component ratio of the
3-alkylsalicylic acid metal salt is from 40 to 100 percent by mole,
(B) a nitrogen compound represented by formula (1) below, and (C) a
phosphorus-containing anti-wear agent:
##STR00001##
wherein R.sup.1 is a straight-chain or branched alkyl group having
1 to 30 carbon atoms, R.sup.2 is hydrogen or a straight-chain or
branched alkyl group having 1 to 24 carbon atoms, and a and b are
each independently an integer of 1, 2 or 3.
[0018] Preferably, the lubricating oil composition further
comprises a friction modifier, particularly an amine-type friction
modifier and/or a fatty acid-type friction modifier.
[0019] Preferably, the lubricating oil composition further
comprises calcium sulfonate and/or magnesium sulfonate.
[0020] Preferably, the lubricating oil composition further
comprises a boron-free ashless dispersant and/or a boron-containing
ashless dispersant.
[0021] Preferably, the alkylsalicylic acid metal salt is a
secondary alkyl type alkylsalicylic acid metal salt.
[0022] Preferably, the lubricating oil composition is used for a
continuously variable transmission with metal pulleys and a metal
belt.
[0023] Preferably, the slip-controlled wet clutch is a
slip-controlled starting clutch.
[0024] The present invention also relates to a method of
lubricating a continuously variable transmission with metal pulleys
and a metal belt and/or a slip-controlled wet clutch.
[0025] The present invention will be described in more detail
below.
[0026] There is no particular restriction on the lubricating base
oil of the lubricating oil composition of the present invention.
Therefore, the lubricating base oil may be a mineral base oil or a
synthetic base oil.
[0027] Specific examples of the mineral oil include those which can
be produced by subjecting a lubricating oil fraction produced by
vacuum-distilling an atmospheric distillation bottom oil resulting
from atmospheric distillation of a crude oil, to any one or more
treatments selected from solvent deasphalting, solvent extraction,
hydrocracking, solvent dewaxing, and hydrorefining; wax-isomerized
mineral oils; and those produced by isomerizing GTL WAX (Gas to
Liquid Wax).
[0028] Examples of the synthetic lubricating base oil include
polybutenes and hydrogenated compounds thereof;
poly-.alpha.-olefins such as 1-octene oligomer and 1-decene
oligomer, and hydrogenated compounds thereof; diesters such as
ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate,
ditridecyl adipate and di-2-ethylhexyl sebacate; polyol esters such
as neopentyl glycol ester, trimethylolpropane caprylate,
trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate
and pentaerythritol pelargonate; aromatic synthetic oils such as
alkylnaphthalenes, alkylbenzenes, and aromatic esters; and mixtures
of the foregoing.
[0029] Examples of the lubricating base oil which may be used in
the present invention include the above-described mineral base oils
and synthetic base oils and mixtures of two or more oils selected
from these base oils. For example, the base oil used in the present
invention may be one or more of the mineral base oils or synthetic
base oils or a mixed oil of one or more of the mineral base oils
and one or more of the synthetic base oils.
[0030] There is no particular restriction on the kinematic
viscosity of the lubricating base oil of the present invention.
However, the lubricating base oil is preferably so adjusted that
the kinematic viscosity at 100.degree. C. is preferably from 2 to 8
mm.sup.2/s, more preferably from 2.5 to 6 mm.sup.2/s, particularly
preferably from 3 to 4.5 mm.sup.2/s. A base oil with a kinematic
viscosity at 100.degree. C. of greater than 8 mm.sup.2/s is not
preferable because the resulting lubricating oil composition would
be poor in low temperature viscosity characteristics while a base
oil with a kinematic viscosity at 100.degree. C. of less than 2
mm.sup.2/s is not also preferable because the resulting lubricating
oil composition would be poor in lubricity due to its insufficient
oil film formation at lubricating sites and large in evaporation
loss of the lubricating base oil.
[0031] There is no particular restriction on the sulfur content in
the lubricating base oil. However, the sulfur content is preferably
0.1 percent by mass or less, more preferably 0.05 percent by mass
or less, more preferably 0.01 percent by mass or less.
[0032] There is no particular restriction on the evaporation loss
of the lubricating base oil. However, the NOACK evaporation loss is
preferably from 10 to 50 percent by mass, more preferably from 20
to 40 percent by mass, particularly preferably from 22 to 35
percent by mass. The use of a lubricating base oil with a NOACK
evaporation loss adjusted within the above ranges renders it
possible to achieve both low temperature characteristics and
anti-wear properties. The term "NOACK evaporation loss" used herein
denotes an evaporation loss measured in accordance with CEC
L-40-T-87.
[0033] Specifically, the lubricating base oil is preferably a
mixture of a base oil with a kinematic viscosity at 100.degree. C.
of 1.5 to 3.5 mm.sup.2/s, preferably 2 to 3.2 mm.sup.2/s, more
preferably 2.5 to 3 mm.sup.2/s, a sulfur content of 0.05 percent by
mass or less, preferably 0.01 percent by mass or less, more
preferably 0.005 percent by mass or less and a NOACK evaporation
loss of 20 to 80 percent by mass, preferably 30 to 65 percent by
mass, more preferably 30 to 55 percent by mass and a base oil with
a kinematic viscosity at 100.degree. C. of 3.5 to 6 mm.sup.2/s,
preferably 3.8 to 4.5 mm.sup.2/s, more preferably 3.9 to 4.5
mm.sup.2/s, a sulfur content of 0.05 percent by mass or less,
preferably 0.01 percent by mass or less, more preferably 0.005
percent by mass or less, and a NOACK evaporation loss of 5 to 20
percent by mass, preferably 10 to 18 percent by mass, more
preferably 12 to 16 percent by mass, mixed at a mass ratio of 10:90
to 90:10, preferably 25:75 to 75:25, more preferably 40:60 to 60:40
so that the kinematic viscosity at 100.degree. C., sulfur content
and NOACK evaporation loss of the mixed base oils are within the
above-described ranges. As the result, it is rendered possible to
produce a composition having both low temperature characteristics
and lubricating properties suitable for a transmission oil
composition.
[0034] Optionally, the above-described mixed base oil may contain a
base oil with a kinematic viscosity at 100.degree. C. of 6
mm.sup.2/s or greater, preferably 10 to 35 mm.sup.2/s, a sulfur
content of 0.05 to 1 percent by mass, preferably 0.1 to 0.7 percent
by mass, more preferably 0.2 to 0.6 percent by mass, and a NOACK
evaporation loss of 10 percent by mass or less, preferably 5
percent by mass or less, more preferably 3 percent by mass or less,
in a small amount, for example 5 to 30 percent by mass.
[0035] A component specifically defined as Component (A) in the
lubricating oil composition of the present invention is an
alkylsalicylic acid metal salt and/or an (overbased) basic salt
thereof, wherein the component ratio of the monoalkylsalicylic acid
metal salt is from 85 to 100 percent by mole, the component ratio
of the dialkylsalicylic acid metal salt is from 0 to 15 percent by
mole and the component ratio of the 3-alkylsalicylic acid metal
salt is from 40 to 100 percent by mole.
[0036] The term "monoalkylsalicylic acid metal salt" used herein
denotes an alkylsalicylic acid metal salt having one alkyl group,
such as a 3-alkylsalicylic acid metal salt, a 4-alkylsalicylic acid
metal salt, and a 5-alkylsalicylic acid metal salt. The component
ratio of the monoalkylsalicylic acid metal salt is from 85 to 100
percent by mole, preferably from 88 to 98 percent by mole, more
preferably from 90 to 95 percent by mole, on the basis of 100
percent by mole of the alkylsalicylic acid metal salt. The
component ratio of the alkylsalicylic acid metal salt other than
the monoalkylsalicylic acid metal salt, such as dialkylsalicylic
acid metal salts is from 0 to 15 percent by mole, preferably from 2
to 12 percent by mole, more preferably from 5 to 10 percent by
mole.
[0037] The component ratio of the 3-alkylsalicylic acid metal salt
is from 40 to 100 percent by mole, preferably from 45 to 80 percent
by mole, more preferably from 50 to 60 percent by mole, on the
basis of 100 percent by mole of the alkylsalicylic acid metal salt.
The total component ratio of the 4-alkylsalicyclic acid metal salt
and 5-alkylsalicylic acid metal salt corresponds to the component
ratio of the alkylsalicylic acid metal salt excluding the
3-alkylsalicylic acid metal salt and dialkylsalicylic acid metal
salt and is from 0 to 60 percent by mole, preferably from 20 to 50
percent by mole, more preferably from 30 to 45 percent by mole, on
the basis of 100 percent by mole of the alkylsalicylic acid metal
salt. Inclusion of a slight amount of a dialkylsalicylic acid metal
salt renders it possible to produce a composition having both
anti-wear properties and low temperature characteristics. The
component ratio of the 3-alkylsalicylate of 40 percent by mole or
more renders it possible to reduce relatively the component ratio
of the 5-alkylsalicylic acid metal salt and thus enhance the oil
solubility of the resulting composition.
[0038] Examples of the alkyl group of the alkylsalicylic acid metal
salt constituting Component (A) include alkyl groups having 10 to
40, preferably 10 to 19 or 20 to 30, more preferably 14 to 18 or 20
to 26, particularly preferably 14 to 18 carbon atoms. Examples of
alkyl groups having 10 to 40 carbon atoms include those such as
decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,
hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl,
docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl,
octacosyl, nonacosyl, and triacontyl groups. These alkyl groups may
be straight-chain or branched and primary and secondary alkyl
groups. However, secondary alkyl groups are preferable because a
salicylic acid metal salt satisfying the above-described
requirements for Component (A) can be produced easily.
[0039] Examples of the metal of the alkylsalicylic acid metal salt
include alkali metals such as sodium and potassium, and alkaline
earth metals such as calcium and magnesium. The metal is preferably
calcium or magnesium, particularly preferably calcium.
[0040] There is no particular restriction on the method of
producing Component (A) used in the present invention which thus
may be produced by any of the known methods. For example, an
alkylsalicylic acid containing a monoalkylsalicylic acid as the
main component is produced by alkylating 1 mole of a phenol using 1
mole or more of an olefin having 10 to 40 carbon atoms, such as a
polymer or copolymer of ethylene, propylene, or butene, preferably
a straight-chain .alpha.-olefin such as an ethylene polymer, and
then carboxylating the alkylated phenol using carbon dioxide gas,
or alternatively by alkylating 1 mole of salicylic acid using 1
mole or more of such an olefin preferably such a straight-chain
.alpha.-olefin. The alkylsalicylic acid is then reacted with a
metal base such as an alkali metal or alkaline earth metal oxide or
hydroxide or converted to an alkali metal salt such as sodium salt
or potassium salt, which alkali metal salt may be further
substituted with an alkaline earth metal. Particularly preferably,
the reaction ratio of the phenol or salicylic acid to the olefin is
adjusted to preferably 1:1 to 1.15 (molar ratio), more preferably
1:1.05 to 1.1 (molar ratio) because the component ratio of the
monoalkylsalicylic acid metal salt to dialkylsalicylic acid metal
salt is easily adjusted to the desired ratio required for component
(A) specified in the present invention. Further, particularly
preferably a straight-chain .alpha.-olefin is used as the olefin
because the component ratio of the 3-alkylsalicylic acid metal
salt, 5-alkylsalicylic acid metal salt, or the like is easily
adjusted to the desired ratio as required for Component (A), and an
alkylsalicylic acid metal salt having a secondary alkyl group which
is preferable in the present invention can be obtained as the main
component. The use of a branched olefin as the above-mentioned
olefin is not preferable because only the 5-alkylsalicylic acid
metal salt is easily produced, but it is necessary to improve the
oil solubility by mixing the 3-alkylsalicylic acid metal salt so as
to produce Component (A) with the structure specified by the
present invention, making the process variable.
[0041] Component (A) used in the present invention also includes
basic salts produced by heating an alkali metal or alkaline earth
metal salicylate (neutral salt) produced as described above,
together with an excess amount of an alkali metal or alkaline earth
metal salt or an alkali metal or alkaline earth metal base
(hydroxide or oxide of an alkali metal or alkaline earth metal) in
the presence of water; and overbased salts produced by reacting
such a neutral salt with a base such as a hydroxide of an alkali
metal or alkaline earth metal in the presence of carbonic acid gas
and/or boric acid or borate.
[0042] These reactions are generally carried out in a solvent
(aliphatic hydrocarbon solvents such as hexane, aromatic
hydrocarbon solvents such as xylene, and light lubricating base
oil). It is preferred to use a solvent whose metal content is
within the range of 1.0 to 20 percent by mass, preferably 2.0 to 16
percent by mass.
[0043] Most preferred for Component (A) used in the present
invention are alkylsalicylic acid metal salts and/or (overbased)
basic salts thereof, the component ratios of which
monoalkylsalicylic acid metal salt and dialkylsalicylic acid metal
salt are from 85 to 95 percent by mole and from 5 to 15 percent by
mole respectively, and 3-alkylsalicylic acid metal salt, and both
4-alkylsalicylic acid metal salt and 5-alkylsalicylic acid metal
salt are from 50 to 60 percent by mole and from 35 to 45 percent by
mole respectively, because the resulting lubricating oil
composition will be excellent in initial anti-shudder properties.
The alkyl group referred herein is particularly preferably a
secondary alkyl group.
[0044] The base number of Component (A) used in the present
invention is usually from 0 to 500 mgKOH/g, preferably from 20 to
450 mgKOH/g, particularly preferably from 100 to 300 mgKOH/g. One
or more compound with a base number in these ranges may be used.
The term "base number" used herein denotes a base number measured
by the perchloric acid potentiometric titration method in
accordance with section 7 of JIS K2501 "Petroleum products and
lubricants-Determination of neutralization number".
[0045] The content of Component (A) in the lubricating oil
composition of the present invention is preferably from 0.005 to
0.5 percent by mass, more preferably from 0.01 to 0.2 percent by
mass, more preferably from 0.02 to 0.1 percent by mass,
particularly preferably from 0.02 to 0.05 percent by mass in terms
of metal on the basis of the total mass of the composition in view
of anti-wear properties, initial anti-shudder properties and
retainability thereof. Component (A) in a relatively less amount is
better.
[0046] Component (B) used in the present invention is a nitrogen
compound represented by formula (1):
##STR00002##
[0047] In formula (1), R.sup.1 is a straight-chain or branched
alkyl group having 1 to 30, preferably 6 to 24, more preferably 6
to 12 carbon atoms. R.sup.2 is hydrogen or a straight-chain or
branched alkyl group having 1 to 24 carbon atoms, preferably
hydrogen or a straight-chain or branched alkyl group having 1 to 12
carbon atoms, more preferably a straight-chain or branched alkyl
group having 6 to 12 carbon atoms. The letters "a" and "b" each
denote an integer of 1, 2 or 3, preferably 1 or 2, more preferably
both denote an integer of 2.
[0048] Specific examples of the straight-chain or branched alkyl
group having 1 to 30 carbon atoms for R.sup.1 include methyl,
ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,
tert-butyl, pentyl, hexyl, octyl, nonyl, decyl, undecyl, dodecyl,
tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,
nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl,
pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, and
triacontyl groups (these alkyl groups may be straight-chain or
branched). Examples of the straight-chain or branched alkyl groups
having 1 to 24 carbon atoms for R.sup.2 include those having 1 to
24 carbon atoms, exemplified with respect to R.sup.1.
[0049] In a nitrogen compound represented by formula (1) it is
preferred that R.sup.1 is an alkyl group having 6 to 24 carbon
atoms, R.sup.2 is hydrogen or an alkyl group having 1 to 24 carbon
atoms, a and b are each 1 or 2 and particularly preferred that
R.sup.1 and R.sup.2 are each an alkyl group having 6 to 12, more
preferably 6 to 10 carbon atoms, and both a and b are 2.
[0050] Examples of preferred nitrogen compounds represented by
formula (1) include 2,5-bis(alkylthio)-1,3,4-thiadiazole having a
straight-chain or branched alkyl group having 6 to 24 carbon atoms;
2,5-bis(alkyldithio)-1,3,4-thiadiazole having a straight-chain or
branched alkyl group having 6 to 24 carbon atoms;
2-(alkylthio)-5-mercapto-1,3,4-thiadiazole having a straight-chain
or branched alkyl group having 6 to 24 carbon atoms;
2-(alkyldithio)-5-mercapto-1,3,4-thiadiazole having a
straight-chain or branched alkyl group having 6 to 24 carbon atoms,
and mixtures thereof. Among these, particularly preferred are
2,5-bis(alkyldithio)-1,3,4-thiadiazoles.
[0051] The content of the nitrogen compound represented by formula
(1) in the lubricating oil composition of the present invention is
preferably from 0.005 to 0.5 percent by mass, more preferably from
0.01 to 0.2 percent by mass, more preferably from 0.02 to 0.15
percent by mass, particularly preferably from 0.03 to 0.14 percent
by mass on the basis of the total mass of the composition. The
content of the nitrogen compound within the foregoing ranges makes
it easy to retain anti-wear properties and anti-shudder properties
for a long period of time.
[0052] Component (C) used in the present invention is a
phosphorus-containing anti-wear agent.
[0053] There is no particular restriction on the
phosphorus-containing anti-wear agent as long as it contains
phosphorus in its molecules. Examples of the anti-wear agent
include phosphorus compounds represented by formula (2) or (3)
below or salts thereof:
##STR00003##
[0054] In formulas (2) and (3), X.sup.1, X.sup.2, X.sup.3, X.sup.4,
X.sup.5, and X.sup.6 are each independently oxygen or sulfur, and
R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, and R.sup.8 are each
independently hydrogen or a hydrocarbon group having 1 to 30 carbon
atoms.
[0055] Specific examples of the hydrocarbon groups having 1 to 30
carbon atoms for R.sup.3 to R.sup.8 include alkyl, cycloalkyl,
alkenyl, alkyl-substituted cycloalkyl, aryl, alkyl-substituted
aryl, and arylalkyl groups.
[0056] Examples of the alkyl group include those, which may be
straight-chain or branched, such as methyl, ethyl, propyl, butyl,
pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl,
tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl and
octadecyl groups.
[0057] Examples of the cycloalkyl group include those having 5 to 7
carbon atoms, such as cyclopentyl, cyclohexyl and cycloheptyl
groups. Examples of the alkylcycloalkyl group include those, of
which the alkyl group may bond to any position of the cycloalkyl
group, having 6 to 11 carbon atoms, such as methylcyclopentyl,
dimethylcyclopentyl, methylethylcyclopentyl, diethylcyclopentyl,
methylcyclohexyl, dimethylcyclohexyl, methylethylcyclohexyl,
diethylcyclohexyl, methylcycloheptyl, dimethylcycloheptyl,
methylethylcycloheptyl and diethylcycloheptyl groups.
[0058] Examples of the alkenyl group include those which may be
straight-chain or branched and the position of which the double
bond may vary, such as butenyl, pentenyl, hexenyl, heptenyl,
octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl,
tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, and
octadecenyl groups.
[0059] Examples of the aryl group include phenyl and naphtyl
groups. Examples of the alkylaryl group include those of which the
alkyl group may be straight-chain or branched and bond to any
position of the aryl group, having 7 to 18 carbon groups, such as
tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl,
hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl,
undecylphenyl, and dodecylphenyl groups.
[0060] Examples of the arylalkyl group include those of which the
alkyl group may be straight-chain or branched, having 7 to 12
carbon atoms, such as benzyl, phenylethyl, phenylpropyl,
phenylbutyl, phenylpentyl and phenylhexyl groups.
[0061] The hydrocarbon group having 1 to 30 carbon atoms for
R.sup.3 to R.sup.8 is preferably an alkyl group having 1 to 30
carbon atoms or aryl group having 6 to 24 carbon atoms, more
preferably an alkyl group having 4 to 20 carbon atoms, more
preferably an alkyl group having 6 to 18 carbon atoms.
[0062] Examples of phosphorus compounds represented by formula (2)
include phosphorous acid; monothiophosphorus acid; dithiophosphorus
acid; trithiophosphorus acid; phosphorus acid monoesters,
monothiophosphorus acid monoesters, dithiophosphorus acid
monoesters, and trithiophosphorus acid monoesters, each having one
of the above-described hydrocarbon groups having 1 to 30 carbon
atoms; phosphorus acid diesters, monothiophosphorus acid diesters,
dithiophosphorus acid diesters, and trithiophosphorus acid
diesters, each having two of the above-described hydrocarbon groups
having 1 to 30 carbon atoms; phosphorus acid triesters,
monothiophosphorus acid triesters, dithiophosphorus acid triesters,
and trithiophosphorus acid triesters, each having three of the
above-described hydrocarbon groups having 1 to 30 carbon atoms; and
mixtures thereof.
[0063] Examples of phosphorus compounds represented by formula (3)
include phosphoric acid; monothiophosphoric acid; dithiophosphoric
acid; trithiophosphoric acid; tetrathiophosphoric acid; phosphoric
acid monoesters, monothiophosphoric acid monoesters,
dithiophosphoric acid monoesters, trithiophosphoric acid
monoesters, and tetrathiophosphoric acid monoesters, each having
one of the above-described hydrocarbon groups having 1 to 30 carbon
atoms; phosphoric acid diesters, monothiophosphoric acid diesters,
dithiophosphoric acid diesters, trithiophosphoric acid diesters,
and tetrathiophosphoric acid diesters, each having two of the
above-described hydrocarbon groups having 1 to 30 carbon atoms;
phosphoric acid triesters, monothiophosphoric acid triesters,
dithiophosphoric acid triesters, trithiophosphoric acid triesters,
and tetrathiophosphoric acid triesters, each having three of the
above-described hydrocarbon groups having 1 to 30 carbon atoms; and
mixtures thereof.
[0064] In the present invention, preferably one or more, more
preferably two or more, and most preferably all three of X.sup.1,
X.sup.2, and X.sup.3 in formula (2) are oxygen.
[0065] Preferably one or more, more preferably two or more, and
most preferably all three of X.sup.4, X.sup.5, and X.sup.6 in
formula (3) are oxygen.
[0066] Examples of salts of phosphorus compounds represented by
formulas (2) and (3) include salts produced by allowing a
phosphorus compound to react with a nitrogen compound such as
ammonia, an amine compound having in its molecules only a
hydrocarbon group or a hydroxyl group-containing hydrocarbon group,
having 1 to 18, preferably 1 to 8 carbon atoms, or an alkyleneoxide
adduct of such an amine compound, or a metal base such as a metal
oxide, a metal hydroxide, a metal carbonate and a metal chloride
and neutralize the whole or part of the remaining acid
hydrogen.
[0067] Specific examples of the nitrogen compound include ammonia;
alkyl- or alkenyl-amines, of which the alkyl or alkenyl group may
be straight-chain or branched, such as monomethylamine,
monoethylamine, monopropylamine, monobutylamine, monopentylamine,
monohexylamine, monoheptylamine, monooctylamine, monolaurylamine,
monostearylamine, monooleylaminedimethylamine, methylethylamine,
diethylamine, methylpropylamine, ethylpropylamine, dipropylamine,
methylbutylamine, ethylbutylamine, propylbutylamine, dibutylamine,
dipentylamine, dihexylamine, diheptylamine and dioctylamine;
alkanolamines, of which the alkanol group may be straight-chain or
branched, such as monomethanolamine, monoethanolamine,
monopropanolamine, monobutanolamine, monopentanolamine,
monohexanolamine, monoheptanolamine, monooctanolamine,
monononanolamine, dimethanolamine, methanolethanolamine,
diethanolamine, methanolpropanolamine, ethanolpropanolamine,
dipropanolamine, methanolbutanolamine, ethanolbutanolamine,
propanolbutanolamine, dibutanolamine, dipentanolamine,
dihexanolamine, diheptanolamine and dioctanolamine; adducts wherein
an alkyleneoxide such as ethyleneoxide is added to these
alkylamines or alkanolamines; and mixtures thereof.
[0068] Specific examples of the metals of the above-mentioned metal
bases include alkali metals such as lithium, sodium, potassium, and
cesium, alkaline earth metals such as calcium, magnesium, and
barium, and heavy metals such as zinc, copper, iron, lead, nickel,
silver, manganese, and molybdenum. Among these metals, preferred
are alkaline earth metals such as calcium and magnesium, and
zinc.
[0069] One or more Components (C) may be arbitrary blended in the
lubricating oil composition of the present invention.
[0070] Component (C) is preferably one compound or a mixture of two
or more compounds, selected from phosphorous or phosphoric acid,
phosphoric or phosphorus acid esters having an alkyl group having 4
to 20 carbon atoms or an (alkyl)aryl group having 6 to 12 carbon
atoms and amine salts produced by allowing these esters to react
with an alkylamine having an alkyl group having 1 to 18 carbon
atoms, more preferably one compound or a mixture of two or more
compounds, selected from phosphorus acid and phosphorus acid esters
having an alkyl group having 4 to 20 carbon atoms, and particularly
preferably phosphorus acid diesters having an alkyl group having 4
to 8 carbon atoms.
[0071] The content of Component (C) in the lubricating oil
composition of the present invention is usually from 0.01 to 5
percent by mass on the basis of the total mass of the composition,
but is preferably from 0.001 to 0.1 percent by mass, more
preferably from 0.005 to 0.08 percent by mass, more preferably from
0.01 to 0.06 percent by mass, particularly preferably from 0.02 to
0.05 percent by mass in terms of phosphorus. Component (C)
contained in the above ranges renders it possible to produce a
composition which is excellent in anti-wear properties and initial
anti-shudder properties and can easily retain the anti-shudder
properties for a long period of time.
[0072] In the lubricating oil composition of the present invention,
there is no particular restriction on the mass ratio ((M)/(P)) of
the content of Component (A) defined by the metal element
concentration (M) to the content of Component (C) defined by the
phosphorus element concentration (P), on the basis of the total
mass of the composition. However, the mass ratio ((M)/(P)) is
preferably from 0.1 to 250, more preferably from 0.5 to 50, more
preferably from 0.8 to 5, particularly preferably from 1 to 3.
[0073] In the lubricating oil composition of the present invention,
there is no particular restriction on the mass ratio ((B)/(P)) of
the content of Component (B) to the content of Component (C)
defined by the phosphorus element concentration (P), on the basis
of the total mass of the composition. However, the mass ratio
((B)/(P)) is preferably from 0.1 to 250, more preferably from 0.5
to 50, more preferably from 1 to 10, particularly preferably from
1.5 to 5.
[0074] The mass ratio of each of Components (A) and (B) to the
content of Component (C) defined by the phosphorus element
concentration (P) within the above-described ranges renders it
possible to produce a composition which is excellent in anti-wear
properties and initial anti-shudder properties and can easily
retain the anti-shudder properties for a long period of time.
[0075] The use of Components (A), (B) and (C) in combination for
the lubricating oil composition of the present invention renders it
possible to produce a composition which is excellent in anti-wear
properties and initial anti-shudder properties and can easily
maintain the anti-shudder properties for a long period of time.
However, in order to further enhance these properties or impart
further properties necessary for a lubricating oil composition,
conventional lubricating oil additives may be added to the
lubricating oil composition of the present invention. Examples of
such additives include metallic detergents other than Component
(A), ashless dispersants, friction modifiers, anti-oxidants,
extreme pressure additives, anti-wear agents, viscosity index
improvers, rust inhibitors, corrosion inhibitors, pour point
depressants, rubber swelling agents, anti-foaming agents, and dyes.
These additives may be used alone or in combination.
[0076] Examples of metallic detergents other than Component (A)
include salicylate detergents other than Component (A), sulfonate
detergents, and phenate detergents.
[0077] Examples of salicylate detergents other than Component (A)
include alkylsalicylic acid metal salts and/or (overbased) basic
salts thereof, wherein the component ratio of the dialkylsalicylic
acid metal salt having two alkyl groups having 10 to 40 carbon
atoms is 15 percent by mole or more; dialkylsalicylic acid metal
salts having an alkyl group having 1 to 9 carbon atoms and an alkyl
group having 10 to 40 carbon atoms and/or (overbased) basic salts
thereof; and alkylsalicylic acid metal salts and/or (overbased)
basic metal salts thereof, wherein the component ratio of the
3-alkylsalicylic acid metal salt is less than 40 percent by mole.
Examples of the metal include alkali metals and alkaline earth
metals.
[0078] Examples of sulfonate detergents include alkali metal or
alkaline earth metal salts, particularly preferably magnesium
and/or calcium salts, of alkyl aromatic sulfonic acids, produced by
sulfonating an alkyl aromatic compound having a molecular weight of
100 to 1,500, preferably 200 to 700. Specific examples of the alkyl
aromatic sulfonic acids include petroleum sulfonic acids and
synthetic sulfonic acids.
[0079] The petroleum sulfonic acids may be those produced by
sulfonating an alkyl aromatic compound contained in the lubricant
fraction of a mineral oil or may be mahogany acid by-produced upon
production of white oil. The synthetic sulfonic acids may be those
produced by sulfonating an alkyl benzene having a straight-chain or
branched alkyl group, produced as a by-product from a plant for
producing an alkyl benzene used as the raw material of a detergent
or produced by alkylating polyolefin to benzene, or those produced
by sulfonating dinonylnaphthalene. There is no particular
restriction on the sulfonating agent used for sulfonating these
alkyl aromatic compounds. The sulfonating agent may be a fuming
sulfuric acid or sulfuric acid.
[0080] Specific examples of phenate detergents include alkaline
earth metal salts, particularly magnesium salts and/or calcium
salts, of an alkylphenolsulfide produced by reacting an alkylphenol
having at least one straight-chain or branched alkyl group having 4
to 30, preferably 6 to 18 carbon atoms with sulfur or a Mannich
reaction product of an alkylphenol produced by reacting such an
alkylphenol with formaldehyde.
[0081] The base number of metallic detergents other than Component
(A) is usually from 0 to 500 mgKOH/g, preferably from 20 to 450
mgKOH/g.
[0082] When a metallic detergent other than Component (A) is used,
it is particularly preferably used in combination with one or more
compounds selected from calcium sulfonate detergents and magnesium
sulfonate detergents, each having a base number of 0 to 500
mgKOH/g, preferably 100 to 400 mgKOH/g. The use of these sulfonate
detergents in combination renders it possible to produce a
composition which has excellent and highly well-balanced anti-wear
properties, anti-shudder properties and retainability thereof.
[0083] There is no particular restriction on the content of the
metallic detergent other than Component (A) in the lubricating oil
composition of the present invention. However, the content is
usually from 0.01 to 5 percent by mass, preferably from 0.05 to 1
percent by mass, particularly preferably from 0.1 to 0.5 percent by
mass, on the basis of the total mass of the composition.
[0084] The ashless dispersant which may be used in the present
invention may be any compound that is used as an ashless dispersant
for a lubricating oil. Examples of the ashless dispersant include
nitrogen-containing compounds such as succinimides, benzylamines
and polyamines, each having in their molecules at least one alkyl
or alkenyl group having 40 to 400, preferably 60 to 350 carbon
atoms, and derivatives or modified products thereof. The alkyl or
alkenyl group having 40 to 400 carbon atoms may be straight-chain
or branched and is preferably a branched alkyl or alkenyl group
derived from an oligomer of an olefin such as propylene, 1-butene,
or isobutylene, or a cooligomer of ethylene and propylene. An alkyl
or alkenyl group having fewer than 40 carbon atoms would result in
a compound with less dissolubility in a lubricating base oil while
an alkyl or alkenyl group having more than 400 carbon atoms would
cause the resulting composition to be poor in low-temperature
fluidity.
[0085] Specific examples of the derivatives or modified products of
nitrogen-containing compounds exemplified as an example of ashless
dispersants include an acid-modified compound produced by allowing
any of the above-described nitrogen-containing compounds to react
with a monocarboxylic acid having 2 to 30 carbon atoms, such as
fatty acid or a polycarboxylic acid having 2 to 30 carbon atoms,
such as oxalic acid, phthalic acid, trimellitic acid, and
pyromellitic acid, so as to neutralize or amidize the whole or part
of the remaining amino and/or imino groups; a boron-modified
compound produced by allowing any of the above-described
nitrogen-containing compounds to react with boric acid so as to
neutralize or amidize the whole or part of the remaining amino
and/or imino groups; a phosphorus-modified compound produced by
allowing any of the above-described nitrogen-containing compounds
to react with phosphoric or phosphorous acid; a sulfur-modified
compound produced by allowing any of the above-described
nitrogen-containing compounds to react with a sulfuric compound;
and modified products produced by a combination of two or more
selected from the modifications with acid, boron, phosphorus and
sulfur, of the above-described nitrogen-containing compounds.
[0086] The lubricating oil composition of the present invention may
contain any one compound or two or more compounds, selected from
the above-exemplified ashless dispersants in an any amount.
However, the content is usually from 0.1 to 10 percent by mass, on
the basis of the total mass of the composition.
[0087] The lubricating oil composition of the present invention
contains preferably a boron-free ashless dispersant and/or a
boron-containing ashless dispersant, which are preferably
succinimide type ashless dispersants. The content of a boron-free
ashless dispersant and/or a boron-containing ashless dispersant is
preferably from 0.1 to 10 percent by mass, more preferably from 3
to 6 percent by mass, on the basis of the total mass of the
lubricating oil composition. When these ashless dispersants are
used in combination, the boron-free ashless dispersant is contained
in an amount of preferably 10 percent by mass or less, more
preferably 1 to 6 percent by mass, particularly preferably 2 to 4
percent by mass while the boron-containing ashless dispersant is
contained in an amount of preferably 6 percent by mass or less,
more preferably 0.01 to 4 percent by mass, particularly preferably
0.5 to 2 percent by mass. The mass ratio of the content of the
boron-containing ashless dispersant to the total amount of the
boron-containing ashless dispersant and the boron-free ashless
dispersant is preferably from 0.1 to 1, more preferably from 0.15
to 0.5, particularly preferably from 0.2 to 0.3. Inclusion of a
boron-containing ashless dispersant can enhance anti-wear
properties and renders it easy to produce a composition having
anti-shudder properties and retainability thereof that are
excellent in a well-balanced manner and shifting
characteristics.
[0088] The friction modifier which may be used in the present
invention may be any compound that is usually used as a friction
modifier for a lubricating oil. Specific examples include amine-,
imide-, amide-, and fatty acid-type friction modifiers, each having
in their molecules at least one alkyl or alkenyl group having 6 to
30 carbon atoms, particularly a straight-chain alkyl or alkenyl
group having 6 to 30 carbon atoms.
[0089] Examples of amine-type friction modifiers include those such
as straight-chain or branched, preferably straight-chain aliphatic
monoamines, alkanolamines, and aliphatic polyamines, each having 6
to 30 carbon atoms, and alkyleneoxide adducts of these aliphatic
amines.
[0090] Examples of imide-type friction modifiers include
succinimide-type friction modifiers such as mono and/or bis
succinimides having one or two straight-chain or branched,
preferably branched hydrocarbon group having 6 to 30, preferably 8
to 18 carbon atoms, and succinimide-modified compounds produced by
allowing such succinimides to react with one or more compounds
selected from boric acid, phosphoric acid, a carboxylic acid having
1 to 20 carbon atoms, and sulfur-containing compounds.
[0091] Examples of amide-type friction modifiers include fatty acid
amide-type friction modifiers such as amides of straight-chain or
branched, preferably straight-chain fatty acids having 7 to 31
carbon atoms and ammonia, aliphatic monoamines, or aliphatic
polyamines.
[0092] Examples of fatty acid-type friction modifiers include
straight-chain or branched, preferably straight-chain fatty acids,
fatty acid esters of such fatty acids and aliphatic monohydric
alcohols or aliphatic polyhydric alcohols, fatty acid metal salts
such as alkaline earth metal salts of such fatty acids (magnesium
and calcium salts) and zinc salts of such fatty acids.
[0093] In the present invention, the above-described imide-type
friction modifiers, in particular succinimide-type friction
modifiers not only can enhance the friction coefficient of a wet
clutch and thus improve power transmission efficiency but also are
effective in significantly improving the anti-shudder
durability.
[0094] Among the above-described friction modifiers, aliphatic
amine-type friction modifiers and fatty acid-type friction
modifiers, particularly fatty acid metal salts are particularly
preferably used because they can significantly improve initial
anti-shudder properties. Particularly preferably, the lubricating
oil composition of the present invention contains such an aliphatic
amine-type friction modifier and/or a fatty acid-type friction
modifier. When an aliphatic amine-type friction modifier is used in
combination with a fatty acid-type friction modifier, there is no
particular restriction on the mass ratio therebetween. However, the
mass ratio is preferably from 1:5 to 5:1, more preferably from 1:3
to 3:1, particularly preferably from 1:2 to 2:1 because more
excellent shifting characteristics can be attained.
[0095] The lubricating oil composition of the present invention may
contain any one compound or two or more compounds selected from the
above-exemplified friction modifiers in an any amount. However, the
content is usually from 0.01 to 5.0 percent by mass, preferably
from 0.03 to 3.0 percent by mass, on the basis of the total mass of
the composition.
[0096] The anti-oxidant which may be used in the present invention
may be any anti-oxidant that is usually used in a lubricating oil,
such as phenolic or aminic compounds.
[0097] Specific examples of anti-oxidants include alkylphenols such
as 2-6-di-tert-butyl-4-methylphenol; bisphenols such as
methylene-4,4-bisphenol(2,6-di-tert-butyl-4-methylphenol);
naphthylamines such as phenyl-.alpha.-naphthylamine;
dialkyldiphenylamines; esters of
(3,5-di-tert-butyl-4-hydroxyphenyl) fatty acid (propionic acid)
with a monohydric or polyhydric alcohol such as methanol,
octadecanol, 1,6-hexanediol, neopentyl glycol, thiodiethylene
glycol, triethylene glycol and pentaerythritol; phenothiazines;
organic metal anti-oxidants such as molybdenum, copper, and zinc;
and mixtures thereof.
[0098] One or more of these compounds may be blended in any amount
in the lubricating oil composition of the present invention.
However, the content of the anti-oxidants is usually from 0.01 to
5.0 percent by mass, on the basis of the total amount of the
composition.
[0099] In the present invention, it is preferred to use a phenolic
anti-oxidant and/or an aminic anti-oxidant and particularly
preferred to use a phenolic anti-oxidant and an aminic anti-oxidant
in combination because anti-shudder properties can be easily retain
for a long period of time. When a phenolic anti-oxidant is used in
combination with an aminic anti-oxidant, the mass ratio
therebetween is preferably from 1:5 to 10:1, more preferably from
1:1 to 8:1, more preferably from 2:1 to 6:1.
[0100] The extreme pressure additive which may be used in the
present invention may be any compound that is used as an extreme
pressure additive for a lubricating oil. Examples of the extreme
pressure additive include sulfuric compounds such as
dithiocarbamates, disulfides, sulfurized olefins, and sulfurized
fats and oils. One or more of these compounds may be blended in any
amount in the lubricating oil composition of the present invention.
However, the content is usually from 0.01 to 5.0 percent by mass,
on the basis of the total mass of the composition.
[0101] Specific examples of viscosity index improvers include
non-dispersant type viscosity index improvers such as polymers or
copolymers of one or more monomers selected from various
methacrylic acid esters or hydrogenated compounds thereof; and
dispersant type viscosity index improvers such as copolymers of
various methacrylic acid esters further containing nitrogen
compounds. Specific examples of other viscosity index improvers
include non-dispersant- or dispersant-type ethylene-.alpha.-olefin
copolymers of which the .alpha.-olefin may be propylene, 1-butene,
or 1-pentene, or a hydrogenated compound thereof; polyisobutylenes
or hydrogenated compounds thereof; styrene-diene hydrogenated
copolymers; styrene-maleic anhydride ester copolymers; and
polyalkylstyrenes.
[0102] It is necessary to select the molecular weight of these
viscosity index improvers, taking account of the shear stability
thereof. Specifically, the number-average molecular weight of the
non-dispersant or dispersant type polymethacrylate is from 5,000 to
150,000, preferably from 5,000 to 35,000. The number-average
molecular weight of polyisobutylenes or hydrogenated compounds
thereof is from 800 to 5,000, preferably from 1,000 to 4,000. The
number-average molecular weight of ethylene-.alpha.-olefin
copolymers or hydrogenated compounds thereof is from 800 to
150,000, preferably from 3,000 to 12,000.
[0103] Among these viscosity index improvers, the use of
ethylene-.alpha.-olefin copolymers or hydrogenated compounds
thereof renders it possible to produce a lubricating oil
composition which is particularly excellent in shear stability.
[0104] One or more compounds selected from these viscosity index
improvers may be blended in any amount in the lubricating oil
composition of the present invention. However, the content of the
viscosity index improver is usually from 0.1 to 20.0 percent by
mass, on the basis of the total amount of the composition.
[0105] Examples of rust inhibitors include alkenyl succinic acids,
alkenyl succinic acid esters, polyhydric alcohol esters, petroleum
sulfonates, and dinonylnaphthalene sulfonates.
[0106] Examples of corrosion inhibitors include benzotriazole-,
tolyltriazole-, and imidazole-type compounds.
[0107] Examples of pour point depressants include polymethacrylate
conforming with a lubricating base oil to be used.
[0108] Examples of rubber swelling agents include aromatic- or
ester-type rubber swelling agents.
[0109] Examples of anti-foaming agents include silicones such as
dimethylsilicone and fluorosilicone.
[0110] Although the contents of these additives are optional, the
content of the corrosion inhibitor is from 0.005 to 0.2 percent by
mass, the content of anti-foaming agent is from 0.0005 to 0.01
percent by mass, and the content of the other additives is from
0.005 to 10 percent by mass, on the basis of the total amount of
the lubricating oil composition of the present invention.
[0111] The kinematic viscosity at 100.degree. C. of the lubricating
oil composition of the present invention is usually from 2 to 25
mm.sup.2/s, preferably from 3 to 8 mm.sup.2/s, more preferably from
4 to 7 mm.sup.2/s, more preferably from 5 to 6 mm.sup.2/s.
[0112] The lubricating oil composition of the present invention is
a lubricating oil composition which has excellent anti-wear
properties for metal pulleys and metal belts and initial
anti-shudder properties and can retain the anti-shudder properties
for a long period of time, thus suitable for a continuously
variable transmission with a slip-controlled wet clutch and a metal
belt, particularly a wet starting clutch. Further, the lubricating
oil composition is suitably used as a lubricating oil that is
required to be improved in anti-wear properties and improve the
characteristics of a wet clutch, specifically used for the
automatic or manual transmission and the differential gears, of
automobiles, construction machines and agricultural machines.
Moreover, the lubricating oil composition can be used as gear oils
for industrial uses; lubricating oils for the gasoline engines,
diesel engines or gas engines of automobiles such as two- and
four-wheeled vehicles, power generators, and ships; turbine oils;
and compressor oils.
APPLICABILITY IN THE INDUSTRY
[0113] Monoalkyl-type salicylate detergents are excellent in
initial anti-shudder properties but inhibit the anti-wear effect of
a phosphorus-containing additive and fail to retain anti-shudder
properties for a slip-controlled wet clutch. However, the
combination of Component (A) with Components (B) and (C) according
to the present invention renders it possible to inhibit wear in a
continuously variable transmission wherein the metal pulleys and
metal belt contact each other under severe conditions and prevent
shudder peculiar to a slip-controlled wet clutch.
BEST MODE FOR CARRYING OUT THE INVENTION
[0114] Hereinafter, the present invention will be described in more
details by way of the following examples and comparative examples,
which should not be construed as limiting the scope of the
invention.
EXAMPLES 1 TO 6 AND COMPARATIVE EXAMPLES 1 to 3
[0115] Lubricating oil compositions of Examples 1 to 6 and
Comparative Examples 1 to 3 set forth in Table 1 were prepared to
evaluate (1) initial anti-shudder properties, (2) retainability of
the anti-shudder properties, and (3) anti-wear properties, as
described below. The results are also set forth in table 1. The
ratio of base oils was on the basis of the total base oil mass, and
the amount of each additive was on the basis of the total mass of
the composition.
(1) Initial Anti-Shudder Properties
[0116] Evaluation of initial anti-wear properties was carried out
using LVFA at a surface pressure of 1.5 MPa in accordance with JASO
M349-98 with regard to the other conditions so as to measure
d.mu./dV in a range of 2 rpm to 200 rpm. The d.mu./dV value is an
index that if it is positive and larger it indicates excellent
initial anti-shudder properties while if it is negative it
indicates that anti-shudder properties are extremely poor.
(2) Retainability of Anti-Shudder Properties
[0117] It was found that in a continuously variable transmission
wherein the metal pulleys and metal belt contact each other under
severe conditions, wear of metals and elution of iron ion occurred
quite often and significant when Component (A) of the present
invention was used and thus it was difficult for the resulting
composition to retain anti-shudder properties. Each of the
lubricating oil compositions was deteriorated at 150.degree. C. for
72 hours in accordance with JIS-K2514 and then 300 ppm by mass of
organic iron containing iron ion were dissolved in each composition
in order to prepare lubricating oils having been used for a long
period of time to be evaluated. Each oil was evaluated by measuring
the d.mu./dV in the same manner as (1). A positive and larger
d.mu./dV value indicates that the composition can retain
anti-shudder properties for a wet clutch even though irons of the
metal pulleys and metal belt elute into the lubricating oil due to
the long time use.
(3) Anti-Wear Properties
[0118] A four ball wear scar diameter resulting from the use of
each composition was measured in accordance with ASTM-D4172. The
smaller the scar diameter, the composition is more excellent in
anti-wear properties.
[0119] As apparent from the results set forth in Table 1, each of
the compositions of Examples 1 to 6 indicated a positive and larger
d.mu./dV value that is a reference of initial anti-shudder
properties and was remarkable in the retainability thereof. It is
also confirmed that these compositions formed a scar the diameter
of which was 0.50 mm or smaller and were also excellent in
anti-wear properties. On the other hand, the compositions
(Comparative Examples 1 to 3) not containing any of Components (A)
to (C) are significantly poor in initial anti-shudder properties or
anti-wear properties.
TABLE-US-00001 TABLE 1 Com- par- Compar- Compar- ative Exam- Exam-
Exam- ative ative Exam- Example 1 Example 2 Example 3 ple 4 ple 5
ple 6 Example 1 Example 2 ple 3 Lubricating base oil (on the basis
of total mass of base oil, mass %) Mineral oil A.sup.1) 50 50 50 50
50 50 50 50 50 Mineral oil B.sup.2) 50 50 50 50 50 50 50 50 50
Additives (on th basis of total mass of composition, mass %) (A)
Salicylate detergent.sup.3) 0.6 0.6 0.6 0.4 1.2 0.6 0.6 -- 0.6 (B)
Nitrogen compound.sup.4) 0.05 0.10 0.05 0.05 0.05 0.05 -- 0.05 0.05
(C) Phosphorus-containing anti-wear 0.18 0.18 0.18 0.18 0.18 --
0.18 0.18 -- agent A.sup.5) Phosphorus-containing anti-wear -- --
-- -- -- 0.28 -- -- -- agent B.sup.6) Other Ashless dispersant
A.sup.7) 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 additives Ashless
dispersant B.sup.8) 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Metallic
detergent A.sup.9) 0.21 0.21 0.21 0.21 0.21 0.21 0.21 0.21 Metallic
detergent B.sup.10) -- -- 0.80 -- -- -- -- -- -- Friction modifier
A.sup.11) 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 Friction
modifier B.sup.12) 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30
Anti-oxidant A.sup.13) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Anti-oxidant B.sup.14) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
Anti-foaming agent.sup.15) 0.002 0.002 0.002 0.002 0.002 0.002
0.002 0.002 0.002 Amount of Ca originating from (A) mass % 0.04
0.04 0.04 0.03 0.08 0.04 0.04 0.00 0.04 Amount of P originating
from (C) mass % 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.00
Initial anti-shudder properties (d.mu./dV) 0.007 0.007 0.006 0.005
0.009 0.007 0.007 -0.003 -- Anti-shudder properties after
deterioration (d.mu./dV) 0.004 0.005 0.005 0.002 0.006 0.004 -0.004
-0.006 -- Anti-wear properties 0.45 0.43 0.47 0.43 0.49 0.45 0.65
0.43 0.65 (Four-ball test wear-scar diameter) mm
.sup.1)Hydrocracked base oil (100.degree. C. kinematic viscosity:
2.6 mm.sup.2/s, viscosity index: 105, NOACK evaporation loss: 52
mass %, S: 0.1 mass % or less) .sup.2)Hydrocracked base oil
(100.degree. C. kinematic viscosity: 4.0 mm.sup.2/s, viscosity
index: 125, NOACK evaporation loss: 16 mass %, S: 0.1 mass % or
less) .sup.3)Calcium carbonate overbased salt of alkylsalicylic
acid calcium salt having C14 to C18 secondary alkyl group (Base
number: 170 mg KOH/g, Ca: 6 mass %), Sructure of alkylsalicylic
carbonate: 3-alkyl: 53 mol %, 4-alkyl: 4 mol %, 5-alkyl: 35 mol %,
3,5-dialkyl: 8 mol % .sup.4)2.5-bis(alkyldithio)-1,3,4-thiaziazole,
alkyl group: C6-C8 alkyl group .sup.5)dibutylphosphite (phosphorus
content: 16.4 mass %) .sup.6)di-2-ethylhexylphosphite (phosphorus
content: 10.6 mass %) .sup.7)polybutenyl succinimide .sup.8)boric
acid-modified polybutenyl succinimide .sup.9)calcium sulfonate
(total base number: 300 mgKOH/g) .sup.10)magnesium sulfonate (total
base number: 100 mgKOH/g) .sup.11)amine-type friction modifier
.sup.12)fatty acid-type friction modifier .sup.13)dialkyl
diphenylamine .sup.14)bisphenolic anti-oxidant
.sup.15)polydimethylsiloxane
* * * * *