U.S. patent application number 13/395668 was filed with the patent office on 2012-07-05 for lubricant composition.
This patent application is currently assigned to NIPPON ITF INC.. Invention is credited to Moritsugu Kasai, Koji Miyake, Masanori Tsujioka, Ryou Yamada.
Application Number | 20120172266 13/395668 |
Document ID | / |
Family ID | 43758561 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120172266 |
Kind Code |
A1 |
Kasai; Moritsugu ; et
al. |
July 5, 2012 |
LUBRICANT COMPOSITION
Abstract
Provided by the present invention is a lubricating oil
composition showing, though containing ZnDTP as an abrasion
resistant agent, a low friction coefficient when used as a
lubricating oil for a low friction sliding material, that is, a
specific lubricating oil composition which is prepared by blending
a lubricant base oil with (A) a specific alkali earth
metal-containing cleaning agent, (B) a specific
boron-non-containing succinimide base ashless dispersant, (C) a
zinc dialkyldithiophosphate and (D) a specific sulfur base compound
and which is used for a low friction sliding material.
Inventors: |
Kasai; Moritsugu;
(Ichihara-shi, JP) ; Yamada; Ryou; (Ichihara-shi,
JP) ; Tsujioka; Masanori; (Kyoto-shi, JP) ;
Miyake; Koji; (Kyoto-shi, JP) |
Assignee: |
NIPPON ITF INC.
Kyoto-shi
JP
IDEMITSU KOSAN CO., LTD.
Tokyo
JP
|
Family ID: |
43758561 |
Appl. No.: |
13/395668 |
Filed: |
September 3, 2010 |
PCT Filed: |
September 3, 2010 |
PCT NO: |
PCT/JP10/65136 |
371 Date: |
March 13, 2012 |
Current U.S.
Class: |
508/185 |
Current CPC
Class: |
C10M 2219/024 20130101;
C10M 2215/064 20130101; C10M 2215/086 20130101; C10N 2030/54
20200501; C10N 2060/14 20130101; C10M 2219/08 20130101; C10N
2040/25 20130101; C10M 2223/047 20130101; C10N 2020/02 20130101;
C10M 2203/1006 20130101; C10M 2223/045 20130101; C10M 2207/027
20130101; C10N 2030/06 20130101; C10M 2207/144 20130101; C10M
2207/026 20130101; C10M 2219/022 20130101; C10M 2207/028 20130101;
C10M 2215/223 20130101; C10M 2219/086 20130101; C10M 2209/084
20130101; C10M 163/00 20130101; C10M 2215/28 20130101; C10M
2207/262 20130101; C10M 2219/046 20130101; C10M 2219/044 20130101;
C10M 2207/028 20130101; C10N 2010/04 20130101; C10M 2207/262
20130101; C10N 2010/04 20130101; C10M 2219/046 20130101; C10N
2010/04 20130101; C10M 2223/045 20130101; C10N 2010/04 20130101;
C10M 2207/027 20130101; C10N 2010/04 20130101; C10M 2219/044
20130101; C10N 2010/04 20130101; C10M 2207/144 20130101; C10N
2010/04 20130101; C10M 2215/28 20130101; C10N 2060/14 20130101;
C10M 2207/028 20130101; C10N 2010/04 20130101; C10M 2207/262
20130101; C10N 2010/04 20130101; C10M 2219/046 20130101; C10N
2010/04 20130101; C10M 2223/045 20130101; C10N 2010/04 20130101;
C10M 2207/027 20130101; C10N 2010/04 20130101; C10M 2219/044
20130101; C10N 2010/04 20130101; C10M 2207/144 20130101; C10N
2010/04 20130101; C10M 2215/28 20130101; C10N 2060/14 20130101 |
Class at
Publication: |
508/185 |
International
Class: |
C10M 169/04 20060101
C10M169/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 15, 2009 |
JP |
2009-213646 |
Claims
1. A lubricating oil composition used for a low friction sliding
material, which is prepared by blending a lubricant base oil with
(A) an alkali earth metal salicylate base and/or alkali earth metal
sulfonate base cleaning agents, (B) a boron-non-containing
succinimide base ashless dispersant having an alkenyl group or an
alkyl group having a number average molecular weight of 500 to
4000, (C) a zinc dialkyldithiophosphate and (D) a sulfur base
compound selected from polysulfide compounds, sulfurized oil &
fats, olefin sulfides, thiophosphoric esters, thiophosphorous
esters and amine salts of the esters, wherein blending amounts
thereof based on a whole amount of the composition are 0.05 to
0.25% by mass of the component (A) in terms of alkali earth metal
concentration, 0.03 to 0.50% by mass of the component (B) in terms
of nitrogen concentration, 0.01 to 0.12% by mass of the component
(C) in terms of phosphorus concentration, 0.02 to 2.0% by mass of
the component (D) in terms of sulfur concentration, 0.10% by mass
or less of an alkali earth metal phenate base cleaning agent in
terms of alkali earth metal concentration and 0.04% by mass or less
of boron-containing succinimide in terms of nitrogen
concentration.
2. The lubricating oil composition according to claim 1, wherein
the blending amount of a zinc dialkyldithiophosphate is 0.03 to
0.10% by mass in terms of phosphorus concentration.
3. The lubricating oil composition according to claim 1, wherein
the blending amount of the boron-non-containing succinimide base
ashless dispersant having an alkenyl group or an alkyl group having
a number average molecular weight of 500 to 4000 is 0.05 to 0.30%
by mass in terms of nitrogen concentration.
4. The lubricating oil composition according to claim 1, wherein
the sulfur base compound is a compound represented by a general
formula (I): R.sup.1--S.sub.n--R.sup.2 (I) (wherein "n" is an
integer selected from 1 to 4; R.sup.1 and R.sup.2 each represent
independently an alkyl group or an aralkyl group).
5. The lubricating oil composition according to claim 4, wherein
"n" in the general formula (I) is 2 or 3.
6. The lubricating oil composition according to claim 1, wherein
the low friction sliding material is a material having a
diamond-like carbon (DLC) film.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricating oil
composition, more specifically to a lubricating oil composition
showing, though containing a zinc dialkyldithiophosphate, a low
frictional coefficient when used as a lubricating oil for a low
friction sliding material.
BACKGROUND ART
[0002] In recent years, it is important to meet environmental
concerns in various fields, and technical development on energy
saving and a reduction in a discharge amount of carbon dioxide is
promoted. In a case of, for example, automobiles, an improvement in
a fuel consumption-saving performance is one of issues, and
technical development of lubricating oils and sliding materials
becomes important.
[0003] In respect to lubricating oils, various base oils and
additives have so far been developed for the purpose of enhancing
various performances. For example, performances required to engine
oils include an appropriate viscosity characteristic, an oxidation
stability, a clean dispersibility, an abrasion preventing property,
a bubbling preventing property and the like, and the above
performances are attempted to be elevated by combination of various
base oils and additives. In particular, zinc dithiophosphate
(ZnDTP) is excellent as an additive for abrasion resistance and
therefore is used well as an additive for engine oils.
[0004] On the other hand, in respect to the sliding materials,
materials forming a hard film such as a TiN film, a CrN film and
the like which contribute to a rise in an abrasion resistance are
known as materials for parts which are exposed to severe friction
and abrasion environment (for example, a sliding part of an
engine). Further, it is known that a friction coefficient can be
reduced in the air under the absence of a lubricating oil by making
use of a diamond-like carbon (DLC) film, and materials having a DLC
film (hereinafter referred to as a DLC material) are expected as a
low friction sliding material.
[0005] However, a friction-reducing effect of a DLC material is
small under the presence of a lubricating oil in a certain case,
and in the above case, a fuel consumption-saving effect is less
liable to be obtained. Accordingly, development of a lubricating
oil composition for a low friction sliding material such as DLC
materials and the like has so far been carried out.
[0006] A lubricating oil composition which contains an ether base
ashless friction-reducing agent and which is used for a low
friction sliding member is disclosed in, for example, a patent
document 1. Disclosed in patent documents 2 and 3 are techniques in
which lubricating oil compositions containing fatty acid ester base
ashless friction-controlling agents and aliphatic amine base
ashless friction-controlling agents are used for a sliding face
between a DLC member and an iron base member and a sliding face
between a DLC member and an aluminum alloy member. Disclosed in a
patent document 4 is a technique in which a low friction agent
composition containing an oxygen-containing organic compound and an
aliphatic amine base compound is used in a low friction sliding
mechanism having a DLC coating sliding member.
[0007] As described above, lubricating oil compositions for low
friction sliding materials have been developed, but even in a case
in which the above techniques are applied, the friction coefficient
tends to grow larger when ZnDTP is blended in order to enhance
further the abrasion resistance and the like. Accordingly, when a
purpose is to obtain a lubricating oil which is excellent in
various performances and well balanced, required is a lubricating
oil composition which shows, though containing ZnDTP, a low
friction coefficient when used as a lubricating oil for a low
friction sliding material.
PRIOR ART DOCUMENTS
Patent Documents
[0008] Patent document 1: JP 2006 36850A [0009] Patent document 2:
JP 2003 238982A [0010] Patent document 3: JP 2004 155891A [0011]
Patent document 4: JP 2005 98495A
OUTLINE OF THE INVENTION
Problems to be Solved by the Invention
[0012] The present invention has been made in light of the
situations, and an object of the present invention is to provide a
lubricating oil composition showing, though containing ZnDTP as an
abrasion resistant agent, a low friction coefficient when used as a
lubricating oil for a low friction sliding material, that is, a
lubricating oil composition for a low friction sliding material in
which an abrasion resistance is consistent with a low frictional
property.
Means for Solving the Problems
[0013] Researches repeated intensively by the present inventors
have resulted in finding that the problems are solved by blending
with specific additives in specific amounts. The present invention
has been completed based on the above knowledge.
[0014] That is, the present invention provides: [0015] 1. a
lubricating oil composition used for a low friction sliding
material, which is prepared by blending a lubricant base oil with
(A) an alkali earth metal salicylate and/or alkali earth metal
sulfonate base cleaning agents, (B) a boron-non-containing
succinimide base ashless dispersant having an alkenyl group or an
alkyl group having a number average molecular weight of 500 to
4000, (C) a zinc dialkyldithiophosphate and (D) a sulfur base
compound selected from polysulfide compounds, sulfurized oil &
fats, olefin sulfides, thiophosphoric esters, thiophosphorous
esters and amine salts of the above esters, wherein blending
amounts thereof based on a whole amount of the composition are 0.05
to 0.25% by mass of the component (A) in terms of alkali earth
metal concentration, 0.03 to 0.50% by mass of the component (B) in
terms of nitrogen concentration, 0.01 to 0.12% by mass of the
component (C) in terms of phosphorus concentration, 0.02 to 2.0% by
mass of the component (D) in terms of sulfur concentration, 0.10%
by mass or less of an alkali earth metal phenate base cleaning
agent in terms of alkali earth metal concentration and 0.04% by
mass or less of boron-containing succinimide in terms of nitrogen
concentration, [0016] 2. the lubricating oil composition according
to the item 1, wherein a blending amount of a zinc
dialkyldithiophosphate is 0.03 to 0.10% by mass in terms of
phosphorus concentration, [0017] 3. the lubricating oil composition
according to the item 1, wherein a blending amount of the
boron-non-containing succinimide base ashless dispersant having an
alkenyl group or an alkyl group having a number average molecular
weight of 500 to 4000 is 0.05 to 0.30% by mass in terms of nitrogen
concentration, [0018] 4. the lubricating oil composition according
to the item 1, wherein the sulfur base compound is a compound
represented by a general formula (I):
[0018] R.sup.1--S.sub.n--R.sup.2 (I)
(wherein "n" is an integer selected from 1 to 4; R.sup.1 and
R.sup.2 each represent independently an alkyl group or an aralkyl
group), [0019] 5. the lubricating oil composition according to the
item 4, wherein "n" in the general formula (I) is 2 or 3, and
[0020] 6. the lubricating oil composition according to the item 1,
wherein the low friction sliding material is a material having a
diamond-like carbon (DLC) film.
Effect by the Invention
[0021] According to the present invention, capable of being
provided is a lubricating oil composition showing, though
containing ZnDTP as an abrasion resistant agent, a low friction
coefficient when used as a lubricating oil for a low friction
sliding material.
MODE FOR CARRYING OUT THE INVENTION
[0022] The lubricating oil composition of the present invention is
prepared by blending a lubricant base oil with (A) an alkali earth
metal salicylate and/or alkali earth metal sulfonate base cleaning
agents, (B) a boron-non-containing succinimide base ashless
dispersant having an alkenyl group or an alkyl group having a
number average molecular weight of 500 to 4000, (C) a zinc
dialkyldithiophosphate and (D) a sulfur base compound selected from
polysulfide compounds, sulfurized oil & fats, olefin sulfides,
thiophosphoric esters, thiophosphorous esters and amine salts of
the esters as essential additives in specific amounts, and it is
used as a lubricating oil for a low friction sliding material.
[0023] The lubricant base oil used in the present invention shall
not specifically be restricted, and there can be used base oils
suitably selected from publicly known mineral base oils and
synthetic base oils which have so far been used.
[0024] In this regard, capable of being listed as the mineral base
oils are, for example, distillate oils obtained by distilling
paraffin base crude oils, intermediate base crude oils or naphthene
base crude oils at atmospheric pressure or subjecting residual oils
obtained by atmospheric distillation to distillation under reduced
pressure, or refined oils obtained by refining the above distillate
oils according to an ordinary method, for example, solvent-refined
oils, hydrogenation-refined oils, dewaxing-treated oils, white
clay-treated oils and the like.
[0025] On the other hand, poly(.alpha.-olefins) which are
.alpha.-olefin oligomers having 8 to 14 carbon atoms, polybutene,
polyol esters, alkylbenzenes and the like can be listed as the
synthetic oils.
[0026] In the present invention, the mineral oils may be used alone
or in combination of two or more kinds thereof as the base oil.
Also, the synthetic oils may be used alone or in combination of two
or more kinds thereof. Further, at least one mineral oil and at
least one synthetic oil may be used in combination.
[0027] It is advantageous that the base oil has a kinetic viscosity
of usually 2 to 50 mm.sup.2/s, preferably 3 to 30 mm.sup.2/s and
particularly preferably 3 to 15 mm.sup.2/s at 100.degree. C. If the
kinetic viscosity at 100.degree. C. is 2 mm.sup.2/s or more, the
vaporization loss is small. On the other hand, if it is 50
mm.sup.2/s or less, the power loss brought about by the viscous
resistance is inhibited, and the fuel consumption-improving effect
is exerted well.
[0028] Further, the above base oil has a viscosity index of
preferably 60 or more, more preferably 70 or more and particularly
preferably 80 or more. If the viscosity index is 60 or more, a
viscosity change of the base oil brought about by temperature is
small, and the stable lubricating performances are exerted.
[0029] Compounds which have so far been publicly known as cleaning
agents such as compounds having an alkyl group can be used as
alkali earth metal salicylate and alkali earth metal sulfonate
which are used as the cleaning agents of the component (A). The
alkali earth metal includes calcium, magnesium and the like, and
calcium is particularly preferred.
[0030] Any of neutral salts, basic salts and perbasic salts can be
used as the cleaning agents, and they may be used alone or in
combination of two or more kinds thereof.
[0031] A whole base number of the cleaning agent can optionally be
selected according to the required performances of the lubricating
oil composition. It is usually 0 to 500 mg KOH/g, preferably 50 to
400 mg KOH/g measured by a perchloric acid method. A blending
amount of the cleaning agent based on a whole amount of the
compositions is 0.05 to 0.25% by mass, preferably 0.06 to 0.25% by
mass and more preferably 0.1 to 0.22% by mass in terms of alkali
earth metal concentration. If the alkali earth metal concentration
exceeds 0.25% by mass, it is difficult to reduce the friction
coefficient.
[0032] Compounds other than the component (A) are also publicly
known as the alkali earth metal-containing cleaning agent, and they
include, for example, alkali earth metal phenate base cleaning
agents. However, if the alkali earth metal phenate base cleaning
agent is blended, it is difficult to reduce the friction
coefficient, and therefore use thereof has to be restricted in the
present invention. A content thereof based on a whole amount of the
compositions is 0.1% by mass or less, preferably 0.05% by mass or
less in terms of alkali earth metal concentration, and it is
particularly preferably not added at all.
[0033] In the present invention, the boron-non-containing
succinimide compound (hereinafter the succinimide compound shall be
referred to as "the succinimide compound of the present invention")
having an alkenyl group or an alkyl group of a number average
molecular weight of 500 to 4000 is blended as the ashless
dispersant of the component (B). If a number average molecular
weight of an alkenyl group or an alkyl group is 500 or more, the
good cleaning effect is exerted, and if it is 4000 or less, the low
temperature fluidity is good.
[0034] The succinimide compound of the present invention includes,
for example, a compound represented by the following a general
formula (II) or a general formula (III):
##STR00001##
R.sup.3 to R.sup.5 in the general formulae (II) and (III) each
represent independently an alkenyl group or an alkyl group of a
number average molecular weight of 500 to 4000, and "m" represents
an integer of 1 to 5. If "m" is an integer of 1 to 5, the cleaning
property is enhanced, and "m" is more preferably an integer of 2 to
4.
[0035] R.sup.3 to R.sup.5 in the general formulae (II) and (III)
include, for example, an alkenyl group or an alkyl group
originating in polybutene and the like obtained by polymerizing
high purity isobutene or a mixture of 1-butene and isobutene by a
boron fluoride base catalyst or an aluminum chloride base
catalyst.
[0036] A production method of the succinimide compound of the
present invention shall not specifically be restricted, and it can
be obtained, for example, by reacting butenylsuccinic acid obtained
by reacting polybutene or chlorinated polybutene with maleic
anhydride at 100 to 200.degree. C. with polyamine such as
diethylenetriamine, triethylenetetraamine, tetraethylenepentaamine,
pentaethylenehexamine and the like. The polybutene and the like
which are precursors of the alkenyl group or the alkyl group are
advantageously used after trace amounts of remaining fluorine
substances and chlorine substances originating in a catalyst used
in a production step have been removed up to usually 50 ppm by mass
or less, preferably 10 ppm by mass or less and particularly
preferably 1 ppm by mass or less by a suitable method such as an
adsorbing method, sufficient washing with water and the like.
[0037] In the present invention, the boron-non-containing
succinimide compound is used as described above. The term
"boron-non-containing" means that a succinimide compound treated by
a boron compound is excluded from the component (B) in the present
application. That is, a boron-containing polybutenylsuccinimide
compound obtained by reacting a polybutenylsuccinimide compound
with a boron compound such as boric acid, borates, boric esters and
the like to neutralize a part or all of a remaining amino group
and/or imino group is known as an ashless dispersant. However,
blending of the above boron-containing polybutenylsuccinimide
compound makes it difficult to reduce the abrasion when it is used
as a lubricating oil for a low friction sliding material.
[0038] In the lubricating oil composition of the present invention,
the succinimide compound in the present invention may be used alone
or in combination of two or more kinds thereof. A blending amount
of the succinimide compound in the present invention is 0.03 to
0.50% by mass, preferably 0.05 to 0.30% by mass in terms of
nitrogen concentration based on a whole amount of the compositions.
If the nitrogen concentration falls in the range, the effects
preferred in terms of a balance between the cleaning property, the
resistance in emulsifying and the economical efficiency are
obtained.
[0039] As described above, blending of the boron-non-containing
succinimide compound makes it difficult to reduce the friction
coefficient, and therefore use thereof has to be limited in the
present invention. A content thereof is 0.04% by mass or less,
preferably 0.02% by mass or less in terms of nitrogen concentration
based on a whole amount of the compositions, and it is particularly
preferably not added at all.
[0040] The zinc dialkyldithiophosphate of the component (C)
includes, for example, a compound represented by a general formula
(IV):
##STR00002##
[0041] In the general formula (IV), R.sup.6 to R.sup.9 each
represent independently an alkyl group, and an alkyl group having 1
to 24 carbon atoms is preferably used.
[0042] The alkyl group having 1 to 24 carbon atoms may be any of
linear, branched and cyclic groups and includes, to be specific,
methyl, ethyl and in addition thereto, various kinds each including
isomers, such as propyl, butyl, pentyl, hexyl, heptyl, octyl,
nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,
hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl,
docosyl, tricosyl and tetracosyl, or cyclopentyl, cyclohexyl,
cycloheptyl and alkyl-substituted groups thereof.
[0043] The specific examples of the zinc dialkyldithiophosphate
represented by the general formula (IV) include, for example, zinc
diisopropyldithiophosphate, zinc diisobutyldithio phosphate, zinc
di-sec-butyldithiophosphate, zinc di-sec-pentyldithiophosphate,
zinc di-n-hexyldithiophosphate, zinc di-sec-hexyldithiophosphate,
zinc di-octyldithiophosphate, zinc di-2-ethylhexyldithiophosphate,
zinc di-n-decyldithio phosphate, zinc di-n-dodecyldithiophosphate,
zinc diisotridecyldithiophosphate and the like. Among them, zinc
di-sec-alkyldithiophosphates are suited in terms of an enhancing
effect of the abrasion resistance.
[0044] In the lubricating oil composition of the present invention,
the zinc dialkyldithiophosphate may be blended alone or in
combination of two or more kinds thereof. A blending amount of the
zinc dialkyldithiophosphate based on a whole amount of the
compositions is 0.01 to 0.12% by mass, preferably 0.03 to 0.10% by
mass in terms of phosphorus concentration. The abrasion resistance
and the high temperature cleaning property are enhancing by
blending the zinc dialkyldithiophosphate, but if it exceeds 0.12%
by mass in terms of phosphorus concentration, it is difficult to
reduce the abrasion coefficient.
[0045] The sulfur base compound of the component (D) is a compound
selected from polysulfide compounds, sulfurized oil & fats,
olefin sulfides, thiophosphoric esters, thiophosphorous esters and
amine salts of the esters. Among them, the polysulfide compounds
are preferred, and a compound represented by the general formula
(I) is particularly preferred:
R.sup.1--S.sub.n--R.sup.2 (I)
In the general formula (I), "n" is an integer selected from 1 to 4,
and "n" is particularly preferably 2 or 3. R.sup.1 and R.sup.2 each
represent independently an alkyl group or an aralkyl group. R.sup.1
and R.sup.2 are preferably a group having 4 to 24 carbon atoms,
more preferably a group having 8 to 18 carbon atoms.
[0046] In the present invention, the sulfur base compound may be
used alone or in combination of two or more kinds thereof as the
base oil. A blending amount of the sulfur base compound based on a
whole amount of the compositions is 0.02 to 2.0% by mass,
preferably 0.02 to 1.0% by mass in terms of sulfur concentration.
Either when the blending amount is less than 0.02% by mass or when
it exceeds 2.0% by mass, it is difficult to reduce the friction
coefficient.
[0047] The lubrication oil composition of the present invention may
be blended with additives which have so far been publicly known as
long as the effects of the present invention are not damaged, and
they include, for example, friction-reducing agents, viscosity
index-improving agents, pour point depressants, antioxidants, rust
preventives and the like.
[0048] The friction-reducing agents include ashless
friction-reducing agents such as fatty acid esters, aliphatic
amines, higher alcohols and the like. Capable of being shown as the
examples of the viscosity index-improving agents are, to be
specific, so-called non-dispersion type viscosity index-improving
agents such as copolymers according to various methacrylic esters
or optional combinations thereof and hydrogenated products thereof
and so-called dispersion type viscosity index-improving agents
obtained by copolymerizing various methacrylic esters including
nitrogen compounds. Also, capable of being shown as the examples
thereof are non-dispersion type or dispersion type
ethylene-.alpha.-olefin copolymers (the .alpha.-olefin includes,
for example, propylene, 1-butene, 1-pentene and the like) and
hydrogenated products thereof, polyisobutylene and hydrogenated
products thereof, styrene-diene hydrogenated copolymers,
styrene-maleic anhydride ester copolymers, polyalkylstyrenes and
the like. The molecular weights of the above viscosity
index-improving agents have to be selected considering the shearing
stability. To be specific, a number average molecular weight of the
above viscosity index-improving agents is 5000 to 1000000,
preferably 100000 to 800000 in a case of, for example, the
dispersion type or non-dispersion type polymethacrylates; 800 to
5000 in a case of polyisobutylene or the hydrogenated products
thereof; and 800 to 300000, preferably 10000 to 200000 in a case of
the ethylene-.alpha.-olefin copolymers and the hydrogenated
products thereof. Also, the viscosity index-improving agents can be
added alone or in optional combination of plural kinds thereof, and
a content thereof is usually 0.1 to 40.0% by mass based on a whole
amount of the lubricating oil composition. The pour point
depressants include, for example, polymethacrylates.
[0049] The antioxidant includes phenol base antioxidants and amine
base antioxidants. The phenol base antioxidants include, for
example, 4,4'-methylenebis(2,6-di-t-butylphenol);
4,4'-bis(2,6-di-t-butylphenol); 4,4'-bis(2-methyl-6-t-butylphenol);
2,2'-methylenebis(4-ethyl-6-t-butylphenol);
2,2'-methylenebis(4-methyl-6-t-butylphenol);
4,4'-butylidenebis(3-methyl-6-t-butylphenol);
4,4'-isopropylidenebis(2,6-di-t-butylphenol);
2,2'-methylenebis(4-methyl-6-nonylphenol);
2,2'-isobutylidenebis(4,6-dimethylphenol);
2,2'-methylenebis(4-methyl-6-cyclohexylphenol);
2,6-di-t-butyl-4-methylphenol; 2,6-di-t-butyl-4-ethylphenol;
2,4-dimethyl-6-t-butylphenol; 2,6-di-t-amyl-p-cresol;
2,6-di-t-butyl-4-(N,N'-dimethylaminomethylphenol);
4,4'-thiobis(2-methyl-6-t-butylphenol);
4,4'-thiobis(3-methyl-6-t-butylphenol);
2,2'-thiobis(4-methyl-6-t-butylphenol);
bis(3-methyl-4-hydroxy-5-t-butylbenzyl)sulfide;
bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide;
n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate;
2,2'-thio[diethyl-bis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]
and the like. Among them, bisphenol base antioxidants and ester
group-containing phenol base antioxidants are particularly
suited.
[0050] The amine base antioxidants include, for example,
monoalkyldiphenylamines such as monooctyldiphenylamine,
monononyldiphenylamine and the like; dialkyldiphenylamines such as
4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine,
4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine,
4,4'-diocyldiphenylamine, 4,4'-dinonyldiphenylamine and the like;
polyalkyldiphenylamines such as tetrabutyldiphenylamine,
tetrahexyldiphenylamine, tetraoctyldiphenylamine,
tetranonyldiphenylamine and the like; naphthyl amine base
antioxidants, to be specific, .alpha.-naphthylamine,
phenyl-.alpha.-naphthylamine; and alkyl-substituted
phenyl-.alpha.-naphthylamines such as
butylphenyl-.alpha.-naphthylamine,
pentylphenyl-.alpha.-naphthylamine,
hexylphenyl-.alpha.-naphthylamine,
heptylphenyl-.alpha.-naphthylamine,
octylphenyl-.alpha.-naphthylamine,
nonylphenyl-.alpha.-naphthylamine and the like. Among them, the
dialkyldiphenylamine base antioxidants and the naphthylamine base
antioxidants are suited.
[0051] The rust preventives include alkylbenzenesulfonates,
dinonylnaphthalenesulfonates, alkenylsuccinic esters, polyhydric
alcohol esters and the like.
[0052] The lubricating oil composition of the present invention is
applied to a sliding face having a low friction sliding material
and can provide it with an excellent low friction property, and
particularly when applied to internal combustion engines, they can
be provided with a fuel consumption-saving effect.
[0053] The sliding face having a low friction sliding material is
particularly preferably a sliding face having a DLC material as the
low friction sliding material at one side thereof. In this case,
the opposite material shall not specifically be restricted, and a
sliding face between, for example, the above DLC material and the
iron base material and a sliding face between the DLC material and
the aluminum alloy material can be listed.
[0054] In this connection, the DLC material has a DLC film on a
surface. The DLC material constituting the above film is an
amorphous material constituted principally from a carbon element,
and a bonding form of carbons themselves comprises both of a
diamond structure (SP.sub.3 bond) and a graphite bond (SP.sub.2
bond). To be specific, it includes a-C (amorphous carbon)
comprising only a carbon element, a-C:H (hydrogen amorphous carbon)
containing hydrogen and MeC containing partially a metal element
such as titanium (Ti), molybdenum (Mo) and the like.
[0055] On the other hand, carburized steel SCM420, SCr420 (JIS) and
the like can be listed as the iron base material. A hypoeutectic
aluminum alloy containing 4 to 20% by mass of silicon and 1.0 to
5.0% by mass of copper or a hypereutectic aluminum alloy is
preferably used as the aluminum alloy material. To be specific,
AC2A, AC8A, ADC12, ADC14 (JIS) and the like can be listed.
[0056] Also, each surface roughness of the DLC material, the iron
base material or the DLC material and the aluminum alloy material
each is suitably 0.1 .mu.m or less in terms of an arithmetic
average roughness Ra from the viewpoint of a stability of sliding.
If it is 0.1 .mu.m or less, local scuffing is less liable to be
formed, and the friction coefficient can be inhibited from growing
larger. Further, the DLC material has preferably a surface hardness
of HV 1000 to 3500 in terms of a micro-Vickers hardness (98 mN
load) and a thickness of 0.3 to 2.0 .mu.m.
[0057] On the other hand, the iron base material has preferably a
surface hardness of HRC 45 to 60 in terms of a Rockwell hardness (C
scale). In this case, a durability of the film can be maintained
even on a sliding condition of about 700 MPa under a high face
pressure as is the case with a cam follower member, and therefore
it is effective.
[0058] Also, the aluminum alloy material has preferably a surface
hardness of HB 80 to 130 in terms of a Brinell hardness.
[0059] If a surface hardness and a thickness of the DLC material
fall in the ranges, abrasion and peeling are inhibited. Further, if
a surface hardness of the iron base material is HRC 45 or more, it
can be inhibited from buckling and peeling under a high face
pressure. On the other hand, if a surface hardness of the aluminum
alloy material falls in the range, the aluminum alloy material is
inhibited from abrading.
[0060] The sliding part to which the lubricating oil composition of
the present invention is applied shall not specifically be
restricted as long as it is a surface in which two metal surfaces
are brought into contact and in which at least one of them has a
low friction sliding material, and a sliding part of an internal
combustion engine can be preferably listed. In the above case, the
very excellent low frictional property as compared with ever is
obtained, and the fuel consumption-saving effect is exerted, so
that it is effective. The DLC member includes, for example, discoid
shims and lifter crestal planes each obtained by coating DLC on a
base plate of a steel material, and the iron base material includes
low alloy chilled cast irons, carburized steels or quenched and
tempered carbon steels and cam lobes prepared by using materials
obtained according to optional combinations thereof.
EXAMPLES
[0061] Hereinafter, the present invention shall be explained in
further details with reference to examples, but the present
invention shall by no means be restricted by these examples.
Examples 1 to 6 and Comparative Examples 1 to 5
[0062] The lubricating oil compositions of the invention 1 each
having compositions shown in Table 1 were prepared and subjected to
a frictional characteristic test shown below to determine a
friction coefficient. The results thereof are shown in Table 2.
<Frictional Characteristic Test>
[0063] A reciprocating friction test equipment (SRV reciprocating
friction test equipment manufactured by Optimal Inc.) was used to
measure the friction coefficient by the following method.
[0064] A disc (.phi.24 mm.times.7.9 mm) on which DLC was coated was
used as a test piece, and several droplets of the sample oil
(lubricating oil composition) were dropped thereon. The friction
coefficient was determined on the conditions of a load of 400N, an
amplitude of 1.5 mm, a frequency of 50 Hz and a temperature of
80.degree. C. in a state in which a cylinder (.phi.15 mm.times.22
mm) made of SCM420 was set on an upper part of the disc.
TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 3 4 5 6 1 2
3 4 5 Lubricant base oil Bal- Bal- Bal- Bal- Bal- Bal- Bal- Bal-
Bal- Bal- Bal- ance ance ance ance ance ance ance ance ance ance
ance (A) Metal Ca sulfonate (1) -- -- 0.50 0.50 0.50 0.50 -- 0.50
0.50 0.50 0.50 base Ca sulfonate (2) -- 1.70 -- -- -- -- -- -- --
-- 2.55 cleaning Ca salicylate (1) -- -- 1.54 1.54 1.54 1.54 --
1.54 1.54 1.54 1.54 agent Ca salicylate (2) 8.70 -- -- -- -- -- --
-- -- -- -- -- Ca phenate -- -- -- -- -- -- 2.20 -- -- -- -- (B)
Ashless Boron-non- 3.62 3.62 3.62 3.62 -- 3.62 3.62 -- 3.62 3.62
3.62 dispersant containing succinimide (1) Boron-non- -- -- -- --
7.84 -- -- -- -- -- -- containing succinimide (2) --
Boron-containing -- -- -- -- -- -- -- 6.18 -- -- -- succinimide (C)
Zinc Zinc dialkyl- 1.00 1.00 1.00 1.00 1.00 1.22 1.00 1.00 1.22
1.50 1.00 dialkyl- dithiophosphate dithio- (1) phosphate Zinc
dialkyl- 0.15 0.15 0.15 0.15 0.15 -- 0.15 0.15 -- 0.23 0.15
dithiophosphate (2) (D) Sulfur Polysulfide 0.20 0.20 0.20 0.20 0.20
0.20 0.20 0.20 -- 0.20 0.20 base compound Other Viscosity index-
3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 3.40 additives
improving agent Pour point 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50
0.50 0.50 0.50 depressant Antioxidant (1) 0.80 0.80 0.80 0.80 0.80
0.80 0.80 0.80 0.80 0.80 0.80 Antioxidant (2) 0.50 0.50 0.50 0.50
0.50 0.50 0.50 0.50 0.50 0.50 0.50 Rust preventive 0.05 0.05 0.05
0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 Total 100 100 100 100 100
100 100 100 100 100 100 Alkali earth metal amount 0.20 0.20 0.20
0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.31 Amount of N originating in
0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 succinimide
Amount of P originating in 0.09 0.09 0.09 0.09 0.09 0.10 0.09 0.09
0.10 0.14 0.09 Zinc dialkyldithiophosphate Amount of S originating
in 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.00 0.04 0.04 sulfur
base compound (unit: % by mass)
[0065] The respective components used for preparing the lubricating
oil compositions are shown below. [0066] Lubricant base oil:
hydrocracked mineral oil (kinematic viscosity at 100.degree. C.:
4.47 mm.sup.2/s) [0067] Ca sulfonate (1): Ca sulfonate (Ca content:
15.2% by mass) [0068] Ca sulfonate (2): Ca sulfonate (Ca content:
12.0% by mass) [0069] Ca salicylate (1): Ca salicylate (Ca content:
7.8% by mass) [0070] Ca salicylate (2): Ca salicylate (Ca content:
2.3% by mass) [0071] Ca phenate: Ca phenate (Ca content: 9.25% by
mass) [0072] Boron-non-containing succinimide (1):
boron-non-containing polybutenylsuccinimide (nitrogen content: 2.1%
by mass, number average molecular weight of a polybutenyl group:
1000) represented by the formula (III) [0073] Boron-non-containing
succinimide (2): boron-non-containing polybutenylsuccinimide
(nitrogen content:0.97% by mass, number average molecular weight of
a polybutenyl group: 1300) represented by the formula (II) [0074]
Boron-containing succinimide: boron-containing
polybutenylsuccinimide (nitrogen content: 1.23% by mass, number
average molecular weight of a polybutenyl group: 1000) represented
by the formula (III) [0075] Zinc dialkyldithiophosphate (1): a
secondary alkyl type zinc dialkyldithiophosphate (phosphorus
content: 8.2% by mass) [0076] Zinc dialkyldithiophosphate (2): a
primary alkyl type zinc dialkyldithiophosphate (phosphorus content:
7.4% by mass) [0077] Sulfur base compound: polysulfide mixture
(R--S.sub.a--R, R is an alkyl group having 12 carbon atoms, "a" is
2 or 3, sulfur content: 22.0% by mass) [0078] Viscosity
index-improving agent: polymethacrylate (weight average molecular
weight Mw: 550,000) [0079] Pour point depressant: polymethacrylate
(weight average molecular weight Mw: 69,000) [0080] Antioxidant
(1): dialkyldiphenylamine (nitrogen content: 4.62% by mass) [0081]
Antioxidant (2): 4,4'-methylenebis(2,6-di-tert-butylphenol) [0082]
Rust preventive: N-alkylbenzotriazole
TABLE-US-00002 [0082] TABLE 2 Example Comparative Example 1 2 3 4 5
6 1 2 3 4 5 DLC DLC DLC DLC DLC W DLC DLC DLC DLC DLC DLC DLC
Reciprocating 0.143 0.146 0.142 0.140 0.145 0.146 0.153 0.160 0.159
0.155 0.156 friction test equipment (friction coefficient)
[0083] The following discs were used as the disc on which DLC was
coated: [0084] DLC: DLC containing 20% of hydrogen [0085] DLC W:
DLC containing (tungsten added) 20% of hydrogen
[0086] It can be found from the results shown in Table 2 that the
compositions prepared in Examples 1 to 6 which are the lubrication
oil compositions of the present invention have a low friction
coefficient and are excellent. On the other hand, Ca phenate and
boron-containing succinimide are blended respectively as the metal
base cleaning agent and the ashless dispersant in Comparative
Examples 1 and 2, and therefore the friction coefficients are high.
In Comparative Example 3, the sulfur base compound is not blended,
and therefore the friction coefficient is high. In Comparative
Examples 4 and 5, the phosphorus amount or the calcium amount is
present to excess, and therefore the friction coefficients are
elevated.
INDUSTRIAL APPLICABILITY
[0087] The lubricating oil composition of the present invention is
applied to a sliding face comprising a low friction sliding
material such as a DLC material and can provide it with an
excellent low friction characteristic, and particularly when
applied to internal combustion engines, they can be provided with a
fuel consumption-saving effect.
* * * * *