U.S. patent application number 14/384112 was filed with the patent office on 2015-02-05 for lubricating oil composition for shock absorber.
This patent application is currently assigned to IDEMITSU KOSAN CO., LTD.. The applicant listed for this patent is IDEMITSU KOSAN CO., LTD.. Invention is credited to Shuichi Sakanoue.
Application Number | 20150038384 14/384112 |
Document ID | / |
Family ID | 49222692 |
Filed Date | 2015-02-05 |
United States Patent
Application |
20150038384 |
Kind Code |
A1 |
Sakanoue; Shuichi |
February 5, 2015 |
LUBRICATING OIL COMPOSITION FOR SHOCK ABSORBER
Abstract
To provide a lubricating oil composition for a shock absorber
for preventing wearing a piston rod and a guide bush in a shock
absorber, which composition lowers the friction coefficient at the
interface between bronze and chromium and reduces wear area of
bronze. The lubricating oil composition for a shock absorber
contains (A) a base oil composed of a mineral oil and/or a
synthetic oil, and (B) a polyhydric alcohol partial ester having a
C10 to C20 fatty acid residue, in an amount of 0.05 mass % to 10
mass %, with respect to the total amount of the composition.
Inventors: |
Sakanoue; Shuichi;
(Ichihara-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IDEMITSU KOSAN CO., LTD. |
Chiyoda-ku, Tokyo |
|
JP |
|
|
Assignee: |
IDEMITSU KOSAN CO., LTD.
Chiyoda-ku, Tokyo
JP
|
Family ID: |
49222692 |
Appl. No.: |
14/384112 |
Filed: |
March 19, 2013 |
PCT Filed: |
March 19, 2013 |
PCT NO: |
PCT/JP2013/057811 |
371 Date: |
September 9, 2014 |
Current U.S.
Class: |
508/370 ;
508/510; 508/519 |
Current CPC
Class: |
C10M 2223/045 20130101;
C10M 141/10 20130101; C10M 2207/283 20130101; C10N 2030/06
20130101; C10M 2203/1006 20130101; C10M 169/04 20130101; C10M
129/76 20130101; C10N 2040/08 20130101; C10M 2207/2895
20130101 |
Class at
Publication: |
508/370 ;
508/510; 508/519 |
International
Class: |
C10M 141/10 20060101
C10M141/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2012 |
JP |
2012-067422 |
Claims
1. A lubricating oil composition for a shock absorber, comprising:
(A) a base oil composed of a mineral oil and/or a synthetic oil,
and; (B) a polyhydric alcohol partial ester having a C10 to C20
fatty acid residue, in an amount of 0.05 mass % to 10 mass %, with
respect to the total amount of the composition.
2. A lubricating oil composition for a shock absorber according to
claim 1, wherein the component (B) is a tetrahydric alcohol partial
ester.
3. A lubricating oil composition for a shock absorber according to
claim 1, wherein the component (B) is pentaerythritol dioleate
and/or pentaerythritol dilaurylate.
4. A lubricating oil composition for a shock absorber according to
claim 1, which further comprises (C) a phosphorus-containing
compound.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricating oil
composition for a shock absorber. More specifically, the present
invention relates to a lubricating oil composition for a shock
absorber mainly used at a sliding part between a guide bush and a
piston rod in a shock-absorber of a four-wheeled vehicle.
BACKGROUND ART
[0002] Lubricating oil for shock absorbers in automobiles is
employed mainly for damping vibration in order to attain optimum
attenuation force and maintain driving stability. Generally, shock
absorbers are disposed in an automobile between the body and the
tires and attenuate vibration of the car body caused by bumps of a
road, jolting generated at quick acceleration or heavy braking, and
other motions.
[0003] Hitherto, lubricating oils for shock absorbers in
automobiles have exhibited enhanced vibration damping effect
through reducing the friction at a sliding interface between an oil
seal and a piston rod, a piston rod and a guide bush, a piston band
and a cylinder, etc. in a shock absorber (see, for example, Patent
Documents 1 and 2).
[0004] Patent Document 3 discloses a lubricating oil composition
containing a base oil and at least one species selected from among
an alkenyl succinimide, an acidic phosphite diester, and a perbasic
sulfonate, phenate, or salicylate of an alkaline earth metal, for
the purposes of enhancing frictional force at the interface between
an oil seal and a piston rod, reducing the friction coefficient
between the piston rod and the guide bush, and suppressing
foaming.
[0005] Generally, a shock absorber is arranged not in a direction
orthogonal to the road but is slanted from the orthogonal
direction, since the slant arrangement provides more excellent
riding comfort. Thus, during expansion and contraction of a shock
absorber, large lateral force attributed to a generated bending
moment is applied to the shock absorber. In order to facilitate
expansion and contraction of the shock absorber under application
of lateral force, a shock absorber oil (shock absorber fluid: SAF)
is required to reduce friction of a bearing (guide bush).
Particularly when the guide bush of a shock absorber has worn, oil
leakage occurs, thereby failing to gain appropriate attenuation
power, which is problematic.
[0006] As described above, the piston rod/guide bush friction has
been reduced by use of a phosphorus-containing additive or a fatty
acid. However, phosphorus-containing additives generally have poor
thermal stability, and fatty acids generally have poor wear
resistance.
PRIOR ART DOCUMENTS
Patent Documents
[0007] Patent Document 1: Japanese Patent Application Laid-Open
(kokai) No. Hei 5-255683
[0008] Patent Document 2: Japanese Patent Application Laid-Open
(kokai) No. 2000-192067
[0009] Patent Document 3: Japanese Patent Application Laid-Open
(kokai) No. 2009-298886
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0010] Under such circumstances, an object of the present invention
is to provide a lubricating oil composition for a shock absorber
that can improve lubricity between bronze and chromium, which are
materials generally used in a guide bush and a piston rod;
specifically, the composition lowers the friction coefficient
therebetween and reduces wear area of bronze, to thereby reduce the
friction coefficient between a piston rod and a guide bush and,
furthermore, to prevent wearing of the guide bush.
Means for Solving the Problems
[0011] The present inventor has conducted extensive studies to
develop a lubricating oil composition for solving the
aforementioned problems, and has found that the object can be
attained by adding a specific amount of a specific polyhydric
alcohol partial ester to a specific base oil. The present invention
has been accomplished on the basis of this finding.
[0012] Accordingly, the present invention provides the
following.
[0013] [1] A lubricating oil composition for a shock absorber,
comprising:
[0014] (A) a base oil composed of a mineral oil and/or a synthetic
oil, and;
[0015] (B) a polyhydric alcohol partial ester having a C10 to C20
fatty acid residue, in an amount of 0.05 mass % to 10 mass %, with
respect to the total amount of the composition.
[0016] [2] A lubricating oil composition for a shock absorber as
described in [1] above, wherein the component (B) is a tetrahydric
alcohol partial ester.
[0017] [3] A lubricating oil composition for a shock absorber as
described in [1] or [2] above, wherein the component (B) is
pentaerythritol dioleate and/or pentaerythritol dilaurylate.
[0018] [4] A lubricating oil composition for a shock absorber as
described in any of [1] to [3] above, which further comprises (C) a
phosphorus-containing compound.
Effects of the Invention
[0019] According to the present invention, there can be provided a
lubricating oil composition for a shock absorber that can improve
lubricity between bronze and chromium, which are materials
generally used in a guide bush and a piston rod; specifically, the
composition lowers the friction coefficient therebetween and
reduces wear area of bronze, to thereby reduce the friction
coefficient between a piston rod and a guide bush and, furthermore,
to prevent wearing of the guide bush. Particularly, the lubricating
oil composition for a shock absorber of the present invention can
provide automobile users with excellent riding comfort through
reduction in friction coefficient. Furthermore, the lubricating oil
composition of the present invention prevents friction in a shock
absorber, to thereby enhance durability of the shock absorber,
whereby the shock absorber can exhibit excellent riding comfort and
high durability.
Modes for Carrying Out the Invention
[0020] The lubricating oil composition for a shock absorber of the
present invention comprises;
[0021] (A) a base oil composed of a mineral oil and/or a synthetic
oil (hereinafter may be referred to simply as "component (A)"),
and;
[0022] (B) a polyhydric alcohol partial ester having a C10 to C20
fatty acid residue (hereinafter may be referred to simply as
"component (B)"), in an amount of 0.05 mass % to 10 mass % with
respect to the total amount of the composition.
[0023] <(A) Base Oil>
[0024] The base oil (A) of the lubricating oil composition of the
present invention is a mineral oil and/or a synthetic oil. No
particular limitation is imposed on the type of the mineral oil and
synthetic oil. Examples of the mineral oil include paraffin-based
mineral oil, intermediate mineral oil, and naphthene-based mineral
oil, which are produced through a routine refining method such as
solvent refining or hydrogenation refining.
[0025] Examples of the synthetic oil include polybutene,
polyolefins [e.g., .alpha.-olefin (co)polymers], esters (e.g.,
polyol-esters, dibasic acid esters, and phosphoric acid esters),
and ethers (e.g., polyphenyl ether), alkylbenzenes, and
alkylnaphthalenes.
[0026] In the present invention, the mineral oil may be used, as
the base oil, singly or in combination of two or more species.
Also, the synthetic oil may be used, as the base oil, singly or in
combination of two or more species. Furthermore, one or more
mineral oils may be combined with one or more synthetic oils.
[0027] Among these oils, mineral oils, particularly paraffin-based
mineral oils; .alpha.-olefin polymers, such as 1-decene oligomers;
and mixtures thereof are preferably employed.
[0028] The lubricating oil composition of the present invention is
mainly employed as an automobile shock absorber oil. Thus, the
viscosity of the base oil is preferably within the range of 2 to 20
mm.sup.2/s, more preferably 3 to 15 mm.sup.2/s, and still more
preferably 4 to 10 mm.sup.2/s in terms of kinematic viscosity at
40.degree. C.
[0029] No particular limitation is imposed on the viscosity index
of the base oil, but it is preferably 95 or higher, more preferably
100 or higher, still more preferably 105 or higher. In the case
where a plurality of base oils are used in combination, properties
of the base oils including viscosity index mean those of the base
oil mixture.
[0030] The base oil preferably has a flash point of 150.degree. C.
or higher, more preferably 155.degree. C. or higher. When the flash
point of the base oil is 150.degree. C. or higher, foaming is
suppressed in use of the oil composition, which may enhance riding
comfort.
[0031] Therefore, it is not preferred to use a base oil to which an
excessive amount of low-viscosity base has been added for the
purpose of enhancement of low-temperature flowability.
[0032] In the present invention, the flash point is generally
measured through JIS K2265 (COC method).
[0033] No particular limitation is imposed on the component (A)
content of the lubricating oil composition of the present
invention. For example, the component (A) content is preferably 50
mass % to 99.9 mass %, with respect to the total amount of the
composition, more preferably 70 mass % to 99.8 mass %, still more
preferably 80 mass % to 99.7 mass %.
[0034] <(B) Polyhydric Alcohol Partial Ester>
[0035] Component (B) is a polyhydric alcohol partial ester having a
C10 to C20 fatty acid residue. As used herein, the term "fatty acid
residue" refers to a residue formed through removal of a carboxyl
group from a fatty acid.
[0036] No particular limitation is imposed on the fatty acid
residue, and the residue may be branched or linear-chain, or may be
an unsaturated aliphatic hydrocarbon residue or a saturated
aliphatic hydrocarbon residue. Specific examples of the fatty acid
residue include decyl, lauryl, palmityl, stearyl, and oleyl.
[0037] Examples of the polyhydric alcohol include dihydric
alcohols, such as ethylene glycol, diethylene glycol, propylene
glycol, and dipropylene glycol; trihydric alcohols, such as
glycerin, trimethylolethane, trimethylolpropane, trimethylolbutane,
1,3,5-pentanetriol, 1,2,4-butanetriol, 1,2,6-hexanetriol;
tetrahydric alcohols, such as pentaerythritol,
1,2,3,4-butanetetrol, and sorbitan; and polyhydric alcohols, such
as adonitol, arabitol, xylytol, sorbitol, and mannitol.
[0038] No particular limitation is imposed on the valency of the
polyhydric alcohol, but the number of hydroxyl groups is preferably
3 or more, more preferably 4.
[0039] The polyhydric alcohol preferably has 1 to 3 ester
substituted sites, more preferably 2 to 3 ester substituted
sites.
[0040] The polyhydric alcohol partial ester preferably has 2 or
more hydroxyl groups.
[0041] Examples of preferred polyhydric alcohol partial esters
include pentaerythritol dioleate, pentaerythritol dilaurylate, and
pentaerythritol distearylate.
[0042] Of these, pentaerythritol dioleate and pentaerythritol
dilaurylate are particularly preferred.
[0043] The component (B) content of the lubricating oil composition
of the present invention is 0.05 mass % to 10 mass %, with respect
to the total amount of the composition, preferably 0.2 mass % to 4
mass %, more preferably 0.3 mass % to 3 mass %.
[0044] <(C) Phosphorus-Containing Compound>
[0045] The lubricating oil composition of the present invention
preferably contains (C) a phosphorus-containing compound
(hereinafter may be referred to simply as "component (C)"). The
phosphorus-containing compound exerts synergistically with
polyhydric alcohol partial ester (B), to thereby provide
considerably enhanced wear resistance.
[0046] Examples of the phosphorus-containing compound (C) include
phospho-ester compounds such as a phosphate ester, an acidic
phosphate monoester amine salt, and an acidic phosphite diester,
and zinc dithiophosphate (ZnDTP).
[0047] The lubricating oil composition of the present invention
preferably contains, as a phosphorus-containing compound among
them, ZnDTP having a C7 to C12 alkyl group. Examples of the ZnDTP
includes compounds represented by the following formula (I)
##STR00001##
(wherein each of R.sup.1 and R.sup.2 represents a C7 to C12
linear-chain, branched, or cyclic alkyl group).
[0048] Specific examples of the alkyl group R.sup.1 or R.sup.2 in
formula (I) include heptyl, isoheptyl, cyclohexylmethyl, octyl,
2-ethylhexyl, isooctyl, cyclooctyl, nonyl, isononyl,
3,5,5-trimethylhexyl, cyclooctylmethyl, decyl, 3,7-dimethyloctyl,
2-propylheptyl, isodecyl, undecyl, dodecyl, 2-butyloctyl, and
isododecyl. Among them, C7 to C10 alkyl groups are more
preferred.
[0049] R.sup.1 and R.sup.2 may be identical to or different from
each other. However, they are preferably the same group, from the
viewpoint of easiness of production.
[0050] Examples of the phosphate ester compound include an acidic
phosphoric acid monoester amine salt formed from an acidic
phosphoric acid monoester having a C1 to C8 alkyl or alkenyl group;
e.g., monomethyl hydrogenphosphate or monoethyl hydrogenphosphate,
and an amine compound having a C8 to C20 alkyl or alkenyl
group.
[0051] The lubricating oil composition of the present invention
preferably has a component (C) content; i.e., a
phosphorus-containing compound content, of 0.3 to 2 mass %, with
respect to the total amount of the composition, more preferably 0.5
to 1.5 mass %.
[0052] <Other Optional Components>
[0053] So long as the object of the present invention is not
impaired, the shock absorber oil of the present invention may
appropriately contain, as an optional additive, at least one
species selected from among an ashless detergent-dispersant, a
metallic detergent, a lubrication improver, an antioxidant, a rust
preventive, a metal deactivator, a viscosity index improver, a pour
point depressant, and a defoaming agent. No particular limitation
is imposed on the optional components, and the amounts of these
components are preferably 0.1 to 20 mass %, with respect to the
total amount of the composition, more preferably 0.3 to 10 mass %,
still more preferably 0.3 to 5 mass %.
[0054] Examples of the ashless detergent-dispersant include
divalent carboxamides, such as a succinimide, a boron-containing
succinimide, a benzylamine, a boron-containing benzylamine, and
succinic acid. Examples of the metallic detergent include a neutral
metal sulfonate, a neutral metal phenate, a neutral metal
salicylate, a neutral metal phosphonate, a basic sulfonate, a basic
phenate, a basic salicylate, a perbasic sulfonate, a perbasic
salicylate, and a perbasic phosphonate.
[0055] Examples of the type of the lubrication improver include an
extreme pressure agent, an antiwear agent, and an oiliness agent,
and examples of the material of the lubrication improver include
organometallic compounds, such as zinc dithiocarbamate (ZnDTC),
oxysulfidomolybdenum organophosphorodithioate (MoDTP), and
oxysulfidomolybdenum dithiocarbamate (MoDTC).
[0056] Examples of the sulfur-containing extreme pressure agent
include sulfurized oils, sulfurized fatty acids, sulfurized esters,
sulfurized olefins, dihydrocarbyl polysulfide, thiadiazole
compounds, alkylthiocarbamoyl compounds, triazine compounds,
thioterpene compounds, and dialkylthio dipropionate compounds.
[0057] Examples of the oiliness agent include aliphatic saturated
and unsaturated monocarboxylic acids, such as stearic acid and
oleic acid; polymerized fatty acids, such as dimer acid and
hydrogenated dimer acid; hydroxy fatty acids, such as ricinoleic
acid and 12-hydroxystearic acid; aliphatic saturated and
unsaturated monoalcohols, such as lauryl alcohol and oleyl alcohol;
aliphatic saturated and unsaturated monoamines, such as
stearylamine and oleylamine; and aliphatic saturated and
unsaturated monocarboxamides, such as lauriamide and oleamide.
[0058] Examples of the antioxidant include polycyclic phenol-based
antioxidants, such as 4,4'-methylenebis(2,6-di-tert-butylphenol)
and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol); amine-based
antioxidants, such as monoalkyldiphenylamine compounds; e.g.,
monooctyldiphenylamine and monononyldiphenylamine,
dialkyldiphenylamine compounds; e.g., 4,4'-dibutyldiphenylamine,
4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine,
4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, and
4,4'-dinonyldiphenylamine, polyalkyldiphenylamine compounds; e.g.,
tetrabutyldiphenylamine, tetrahexyldiphenylamine,
tetraoctyldiphenylamine, and tetranonyldiphenylamine, and
naphthylamine compounds; e.g., .alpha.-naphthylamine,
phenyl-.alpha.-naphthylamine, butylphenyl-.alpha.-naphthylamine,
pentylphenyl-.alpha.-naphthylamine,
hexylphenyl-.alpha.-naphthylamine,
heptylphenyl-.alpha.-naphthylamine,
octylphenyl-.alpha.-naphthylamine, and
nonylphenyl-.alpha.-naphthylamine; and sulfur-containing
antioxidants such as thioterpene compounds; e.g.,
2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol
and a reaction product between phosphorus pentasulfide and pinene,
and dialkyl thiodipropionates; e.g., dilauryl thiodipropionate and
distearyl thiodipropionate.
[0059] Examples of the rust preventive include metal sulfonates and
succinate esters. Examples of the metal deactivator include
benzotriazole and thiadiazole.
[0060] Examples of the viscosity index improver include
polymethacrylates, dispersed polymethacrylates, olefin copolymers
(e.g., ethylene-propylene copolymer), dispersed olefin copolymers,
and styrene copolymers such as (e.g., styrene-diene hydrogenated
copolymer).
[0061] Examples of the pour point depressant which may be used in
the invention include polymethacrylates having a mass average
molecular weight of about 50,000 to about 150,000.
[0062] The defoaming agent is preferably a silicone polymer-based
defoaming agent. Through incorporation of the silicone
polymer-based defoaming agent, defoaming performance can be
effectively attained, whereby riding comfort can be improved.
[0063] Examples of the silicone polymer-based defoaming agent
include organopolysiloxanes. Among them, fluorine-containing
organopolysiloxanes such as trifluoropropylmethylsilicone oil are
particularly preferred.
[0064] The lubricating oil composition of the present invention may
be applied to any of a multi-cylinder shock absorber and a
single-cylinder shock absorber, and shock absorbers of a
four-wheeled vehicle or a two-wheeled vehicle. The composition of
the present invention is particularly suitably used in four-wheeled
vehicles.
[0065] Particularly, the lubricating oil composition of the present
invention lowers friction coefficient at the interface between
bronze and chromium and reduces wear area of bronze. Thus, the
composition of the present invention is suitably used as a
lubricant for a shock absorber which has a guide bush at least
including a bronze surface, and a piston rod at least including a
sliding part which comes into contact with the guide bush and which
is made of chromium (e.g., chromium plating).
EXAMPLES
[0066] The present invention will next be described in more detail
by way of examples, which should not be construed as limiting the
invention thereto.
[0067] Measurement of friction coefficient and a wear test were
carried out through the following procedures.
[0068] (1) Measurement of bronze-chromium friction coefficient
[0069] Tester: Bowden-type reciprocating kinetic friction
tester
[0070] Test conditions:
[0071] Load: 0.5 kgf
[0072] Stroke: 10 mm
[0073] Speed: 0.2 mm/s
[0074] Temperature: 80.degree. C.
[0075] Friction operation: once
[0076] Friction members
[0077] Upper friction member: phosphor bronze ball
[0078] Lower friction member: chromium-plated sheet
[0079] (50.times.1,000.times.5 mm)
[0080] In a specific procedure, a 1/2-inch phosphor bronze was
used. An oil composition sample was supplied to a plate, in an
amount corresponding to several drops. The ball was conditioned on
the plate (8 mm/s, 0.1 kgf for 2 minutes, 0.2 kgf for 2 minutes,
0.3 kgf for 2 minutes, and 0.5 kgf for 2 minutes). Thereafter, the
wear test was performed at 0.2 mm/s.
[0081] (2) Wear test of bronze surface (wear area)
[0082] Tester: Bowden-type reciprocating kinetic friction
tester
[0083] Test conditions:
[0084] Load: 0.5 kgf
[0085] Stroke: 10 mm
[0086] Speed: 8.0 mm/s
[0087] Temperature: 80.degree. C.
[0088] Friction time: 30 minutes
[0089] Friction members
[0090] Upper friction member: phosphor bronze ball
[0091] Lower friction member: chromium-plated sheet
[0092] (50.times.1,000.times.5 mm)
[0093] In the wear test, a 1/2-inch phosphor bronze was used.
[0094] An oil composition sample was supplied to a plate, in an
amount corresponding to several drops. The wear area of the
phosphor bronze ball was measured.
Examples 1 to 6, and Comparative Examples 1 to 4
[0095] Lubricating oil compositions (shock absorber oils)
containing the components given in Table 1 were prepared. Each
composition was subjected to the friction coefficient measurement
and the wear test. Table 1 shows the results.
TABLE-US-00001 TABLE 1 Examples/ Comp. Comp. Comp. Comp.
Comparative Examples Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 1 Ex.
2 Ex. 3 Ex. 4 Compo- (A) Base oil 99.50 90.00 99.50 99.90 99.50
95.00 99.50 99.50 99.50 99.50 nent (B) + .alpha. Pentaerythritol
dioleate 0.50 0.50 0.10 5.00 (mass %) Pentaerythritol dilaurylate
0.50 Pentaerythritol monooleate 0.50 Pentaerythritol tetraoleate
0.50 Stearic acid 0.50 Methyl acid phosphate 0.50 amine salt (C)
Zn-DTP (pri) C8-C10 0.50 0.50 Test results Friction coefficient
0.093 0.105 0.097 0.112 0.115 0.096 0.362 0.084 0.184 0.179 Wear
area (mm.sup.2) 0.176 0.124 0.188 0.203 0.241 0.263 0.560 0.550
0.468 0.193
[0096] The components used in the Examples and Comparative Examples
shown in Table 1 are as follows.
[0097] Base oil: secondary hydro-reformed mineral oil
(paraffin-base) having a kinematic viscosity of 7.83 mm.sup.2/s
measured at 40.degree. C.
[0098] Pentaerythritol dioleate: UNISTER H481D, product of NOF
Corporation
[0099] Pentaerythritol monooleate: EKISUPARU PE-MO
[0100] Pentaerythritol tetraoleate: UNISTER H481R, product of NOF
Corporation
[0101] Methyl acid phosphate amine salt: VANLUBE 672, product of
Vandarbilt
[0102] Zn-DTP(pri): OLOA 5286, C8 to C10 mixed alkyl groups,
product of Ethyl Corporation
[0103] According the oil compositions of the Examples, each
containing (A) a base oil composed of a mineral oil and/or a
synthetic oil and a specific amount of (B) a polyhydric alcohol
partial ester having a C10 to C20 fatty acid residue, friction
coefficient and wear area were found to be reduced. Particularly in
the case of the oil composition of Example 2, containing component
(B) and component (C), wear area was considerably reduced.
[0104] In Comparative Example 1, employing a complete ester of a
polyhydric alcohol, friction coefficient and wear area were at high
levels. In Comparative Example 2, employing stearic acid, friction
coefficient was low, but wear area was large. In Comparative
Example 3, employing ZnDTP instead of component (B), friction
coefficient and wear area were at high levels. In Comparative
Example 4, employing a phosphate amine salt, friction coefficient
was higher than that obtained in the Examples.
INDUSTRIAL APPLICABILITY
[0105] The lubricating oil composition of the present invention can
be used for automobile shock absorbers. The composition is
applicable to both four-wheeled vehicles and two-wheeled
vehicles.
* * * * *