U.S. patent application number 14/384085 was filed with the patent office on 2015-02-26 for lubricating oil composition and device using same.
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 Toshiyuki Tsubouchi.
Application Number | 20150057203 14/384085 |
Document ID | / |
Family ID | 49222542 |
Filed Date | 2015-02-26 |
United States Patent
Application |
20150057203 |
Kind Code |
A1 |
Tsubouchi; Toshiyuki |
February 26, 2015 |
LUBRICATING OIL COMPOSITION AND DEVICE USING SAME
Abstract
A lubricating oil composition contains a base oil containing a
compound (A) and a compound (B) below and a compound (C). The
lubricating oil composition exhibits a kinematic viscosity at 40
degrees C. in a range of 20 mm.sup.2/s to 40 mm.sup.2/s, a density
at 15 degrees C. of 1.1 g/cm.sup.3 or more, a flash point of 200
degrees C. or more, and a viscosity index of 100 or more. The
compound (A) is an ester or an ether having two or more aromatic
rings. The compound (B) is an ester or an ether having a kinematic
viscosity at 40 degrees C. of 12 mm.sup.2/s or less, a density at
15 degrees C. of 0.9 g/cm.sup.3 or more and a flash point of 100
degrees C. or more. The compound (C) is a poly(meth)acrylate having
a mass average molecular weight of 50000 or less.
Inventors: |
Tsubouchi; Toshiyuki;
(Sodegaura-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: |
49222542 |
Appl. No.: |
14/384085 |
Filed: |
March 12, 2013 |
PCT Filed: |
March 12, 2013 |
PCT NO: |
PCT/JP2013/056809 |
371 Date: |
September 9, 2014 |
Current U.S.
Class: |
508/482 ;
508/463; 508/479 |
Current CPC
Class: |
C10N 2040/08 20130101;
C10M 2207/2805 20130101; C10M 111/04 20130101; C10N 2030/02
20130101; C10N 2030/06 20130101; C10N 2020/02 20130101; C10M
2207/2825 20130101; C10N 2050/10 20130101; C10M 2207/2835 20130101;
C10M 2209/084 20130101; C10N 2020/04 20130101; C10M 169/041
20130101; C10N 2030/58 20200501; C10M 2207/2855 20130101; C10N
2040/02 20130101; C10M 2209/1045 20130101; C10M 2207/0406 20130101;
C10M 2209/1045 20130101; C10M 2209/1085 20130101; C10M 2209/1045
20130101; C10M 2209/1095 20130101; C10M 2209/1045 20130101; C10M
2209/1085 20130101; C10M 2209/1095 20130101 |
Class at
Publication: |
508/482 ;
508/463; 508/479 |
International
Class: |
C10M 111/04 20060101
C10M111/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2012 |
JP |
2012-067763 |
Claims
1. A lubricating oil composition comprising: a base oil comprising
a compound (A) and a compound (B); and a compound (C), wherein the
compound (A) is an ester or an ether having two or more aromatic
rings, the compound (B) is an ester or an ether having a kinematic
viscosity at 40 degrees C. of 12 mm.sup.2/s or less, a density at
15 degrees C. of 0.9 g/cm.sup.3 or more and a flash point of 100
degrees C. or more, the compound (C) is a poly(meth)acrylate having
a mass average molecular weight of 50000 or less, and the
lubricating oil composition has a kinematic viscosity at 40 degrees
C. in a range of 20 mm.sup.2/s to 40 mm.sup.2/s, a density at 15
degrees C. of 1.1 g/cm.sup.3 or more, a flash point of 200 degrees
C. or more, and a viscosity index of 100 or more.
2. The lubricating oil composition according to claim 1, wherein
the compound (A) is represented by any one of formulae (1), (2) and
(3) below, ##STR00007## wherein n and m are each independently 0 or
1; p and q are each independently an integer of 0 to 3; and X and Y
are each independently an alkyl group having 1 to 30 carbon atoms
that optionally comprises a cycloalkyl group or an aromatic group,
a cycloalkyl group or an aromatic group having 5 to 12 carbon
atoms, an alkyloxycarbonyl group having 2 to 30 carbon atoms that
optionally comprises a cycloalkyl group or an aromatic group, or an
alkylcarbonyloxy group having 2 to 30 carbon atoms that optionally
comprises a cycloalkyl group or an aromatic group, ##STR00008##
wherein n and m are each independently 0 or 1; p and q are each
independently an integer of 0 to 3; X and Y are each independently
an alkyl group having 1 to 10 carbon atoms; and A is an alkylene
group having 2 to 18 carbon atoms that optionally comprises oxygen
in a main chain and/or optionally comprises a side chain,
##STR00009## wherein j, k, n and m are each independently 0 or 1; p
and q are each independently an integer of 0 to 3; X and Y are each
independently an alkyl group having 1 to 10 carbon atoms; and Z is
an alkylene group having 1 to 18 carbon atoms that optionally
comprises a side chain.
3. The lubricating oil composition according to claim 1, wherein
the compound (B) is one selected from the group consisting of
adipic acid diester of ethyleneglycolmonobutylether, adipic acid
diester of diethyleneglycolmonobutylether, 2-ethyl hexanoic acid
diester of triethyleneglycol, dibutyl sebacate, dioctyl adipate,
dioctyl azelate, dioctyl sebacate, dimethyl phthalate, diethyl
phthalate, tetraethyl eneglycoldimethylether, and diethyl
succinate.
4. The lubricating oil composition according to claim 1, wherein a
ratio of the compound (A) to the compound (B) in the base oil is
from 2 to 10 by a mass ratio ((A)/(B)).
5. The lubricating oil composition according to claim 1, wherein a
total amount of the compound (A) and the compound (B) is 85 mass %
or more of the base oil.
6. The lubricating oil composition according to claim 1, wherein a
ratio of the compound (A) is from 40 mass % to 95 mass % of a total
amount of the composition.
7. The lubricating oil composition according to claim 1, wherein a
ratio of the compound (B) is from 5 mass % to 60 mass % of the
total amount of the composition.
8. The lubricating oil composition according to claim 1, wherein
the lubricating oil composition is a lubricating oil composition or
grease in a hydraulic device, a rotary device, a bearing or a
gear.
9. A device applied with the lubricating oil composition according
to claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricating oil
composition, more specifically, a lubricating oil composition
applicable to a hydraulic device, a rotary device, a bearing, a
gear and the like, and a device using the lubricating oil
composition.
BACKGROUND ART
[0002] A variety of hydraulic devices using hydraulic fluids such
as a construction machine, an injection molding machine, a press
machine, a crane and a machining center have been widely used. A
variety of oils have been used in these hydraulic devices (see, for
instance, Patent Literature 1 or 2).
[0003] Patent Literature 1 discloses a hydraulic fluid for a
vibration suppression damper, the hydraulic fluid having a
viscosity index of 110 or more and a pour point of minus 25 degrees
C. or less, and specifically containing poly .alpha.-olefin, polyol
ester and polyether. Patent Literature 2 discloses a lubricating
oil such as a compressor oil, a turbine oil and a hydraulic fluid,
which is used for a lubricating system requiring a large working
load, and contains alkyl diphenyl and alkyl diphenyl ether.
[0004] However, since a bulk modulus of elasticity of each of the
above lubricating oils of Patent Literatures 1 and 2 is not so
high, the above lubricating oils do not sufficiently function as a
pressure transmission medium.
[0005] In view of this point, a hydraulic fluid and a pressure
transmission medium with a high bulk modulus of elasticity and
containing an ester or an ether having two aromatic rings as a base
oil have been proposed (see Patent Literatures 3 and 4). These base
oils are characterized by having a density at 15 degrees C. as high
as 1.0 g/cm.sup.3 or more. Since the density and the bulk modulus
of elasticity are correlative, when the density at 15 degrees C. is
1.1 g/cm.sup.3 or more, a tangent bulk modulus of elasticity at 40
degrees C. and 50 MPa becomes about 1.8 GPa or more, which means
that the hydraulic fluid and the pressure transmission medium
respectively in Patent Literatures 3 and 4 are an excellent
lubricating oil having a tangent bulk modulus of elasticity that is
higher by 20% than a tangent bulk modulus of elasticity (about 1.5
GPa) of a mineral oil.
CITATION LIST
Patent Literature(s)
[0006] Patent Literature 1: JP-A-2000-119672 [0007] Patent
Literature 2: JP-A-6-200277 [0008] Patent Literature 3:
WO2008/133233 [0009] Patent Literature 4: WO2010/005022
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0010] However, even the lubricating oils described in Patent
Literatures 1 and 2 are low in viscosity index and there are not a
well-balanced lubricating oil.
[0011] An object of the invention is to provide a lubricating oil
composition having a high density, a low viscosity and a high
viscosity index, and a device using the lubricating oil
composition.
Means for Solving the Problems
[0012] In order to solve the above problems, the invention provides
a lubricating oil composition described below and a device using
the lubricating oil composition.
[0013] (1) A lubricating oil composition according to an aspect of
the invention contains: a base oil containing a compound (A) and a
compound (B); and a compound (C), in which the compound (A) is an
ester or an ether having two or more aromatic rings, the compound
(B) is ester or ether having a kinematic viscosity at 40 degrees C.
of 12 mm.sup.2/s or less, a density at 15 degrees C. of 0.9
g/cm.sup.3 or more and a flash point of 100 degrees C. or more, and
the compound (C) is a poly(meth)acrylate having a mass average
molecular weight of 50000 or less, and the lubricating oil
composition has a kinematic viscosity at 40 degrees C. in a range
of 20 mm.sup.2/s to 40 mm.sup.2/s, a density at 15 degrees C. of
1.1 g/cm.sup.3 or more, a flash point of 200 degrees C. or more,
and a viscosity index of 100 or more.
[0014] (2) In the lubricating oil composition according to the
above aspect of the invention, the compound (A) is represented by
any one of formulae (1), (2) and (3) below.
##STR00001##
[0015] n and m are each 0 or 1; p and q are each an integer of 0 to
3; and X and Y are each an alkyl group having 1 to 30 carbon atoms
that optionally includes a cycloalkyl group or an aromatic group, a
cycloalkyl group or an aromatic group having 5 to 12 carbon atoms,
an alkyloxycarbonyl group having 2 to 30 carbon atoms that
optionally includes a cycloalkyl group or an aromatic group, or an
alkylcarbonyloxy group having 2 to 30 carbon atoms that optionally
includes a cycloalkyl group or an aromatic group.
##STR00002##
[0016] n and m are each 0 or 1; p and q are each an integer of 0 to
3; X and Y are each an alkyl group having 1 to 10 carbon atoms; and
A represents an alkylene group having 2 to 18 carbon atoms that
optionally includes oxygen in a main chain and/or optionally
includes a side chain.
##STR00003##
[0017] j, k, n and m are each 0 or 1; p and q are each an integer
of 0 to 3; X and Y are each an alkyl group having 1 to 10 carbon
atoms; and Z is an alkylene group having 1 to 18 carbon atoms that
optionally includes a side chain.
[0018] (3) In the lubricating oil composition according to the
above aspect of the invention, the compound (B) is one selected
from adipic acid diester of ethyleneglycolmonobutylether, adipic
acid diester of diethyleneglycolmonobutylether, 2-ethyl hexanoic
acid diester of triethyleneglycol, dibutyl sebacate, dioctyl
adipate, dioctyl azelate, dioctyl sebacate, dimethyl phthalate,
diethyl phthalate, tetraethyleneglycoldimethylether, and diethyl
succinate.
[0019] (4) In the lubricating oil composition according to the
above aspect of the invention, a ratio of the compound (A) to the
compound (B) in the base oil is in a range of 2 to 10 by a mass
ratio ((A)/(B)).
[0020] (5) In the lubricating oil composition according to the
above aspect of the invention, a total amount of the compound (A)
and the compound (B) is 85 mass % or more of the base oil.
[0021] (6) In the lubricating oil composition according to the
above aspect of the invention, a ratio of the compound (A) is in a
range of 40 mass % to 95 mass % of a total amount of the
composition.
[0022] (7) In the lubricating oil composition according to the
above aspect of the invention, a ratio of the compound (B) is in a
range of 5 mass % to 60 mass % of the total amount of the
composition.
[0023] (8) In the lubricating oil composition according to the
above aspect of the invention, the lubricating oil composition is a
lubricating oil composition or grease used in a hydraulic device, a
rotary device, a bearing or a gear.
[0024] (9) A device applied with the lubricating oil composition
according to the above aspect of the invention.
[0025] According to the invention, a lubricating oil composition
having a high density and a high viscosity index can be provided.
Accordingly, the lubricating oil composition of the invention is
suitably applicable to devices such as a hydraulic device, a rotary
device, a bearing and a gear.
DESCRIPTION OF EMBODIMENT(S)
[0026] A lubricating oil composition according to an exemplary
embodiment is provided by blending a compound (C) in a base oil
containing a compound (A) and a compound (B) described below. The
lubricating oil composition will be described below in detail.
[0027] The compound (A) is an ester or an ether having two or more
aromatic rings.
[0028] The compound (B) is an ester or an ether having a kinematic
viscosity at 40 degrees C. of 12 mm.sup.2/s or less, a density at
15 degrees C. of 0.9 g/cm.sup.3 or more and a flash point of 100
degrees C. or more.
[0029] The compound (C) is a poly(meth)acrylate having a mass
average molecular weight of 50000 or less.
Compound (A)
[0030] The compound (A) in the exemplary embodiment is an ester or
an ether having two or more aromatic rings. A manufacturing method
of the compound is not particularly limited. A variety of typical
manufacturing methods for esterification or etherification are
applicable.
[0031] For instance, carboxylic acid, carboxylic acid ester,
carboxylic acid chloride or a derivative thereof, alcohol or a
derivative thereof are used as the material. Specific examples of
usable dicarboxylic acid include oxalic acid, malonic acid,
succinic acid, adipic acid, azelaic acid, sebacic acid and
dodecanedioic acid. Specific examples of a usable carboxylic acid
are benzoic acid, toluic acid, phenylacetic acid, phenoxyacetic
acid, anisic acid, and salicylic acid. Examples of usable alcohol
include phenol, cresol, xylenol, benzyl alcohol, phenethyl alcohol,
phenoxyethanol, benzyl oxyethanol, diethylene glycol monobenzyl
ether, and ethylene glycol monobenzyl ether.
[0032] Examples of a substituent include an aromatic ring group
optionally substituted by an alkyl group, a nitro group, a hydroxyl
group or an alkoxy group. A material containing these substituents
is typically used. However, when being substituted by an alkyl
group, the material may be alkylated after esterification.
Alternatively, an initially alkylated material may be used. An
esterification catalyst is not particularly limited. Alternatively,
no catalyst may be used for esterification.
[0033] A manufacturing method of an ether compound is not limited
to a typical Williamson synthesis method. A carboxylic acid having
an ether bond such as phenoxyacetic acid, phenoxyethanol, benzyl
oxyethanol and diethylene glycol monobenzyl ether, or alcohol
having an ether bond may be used as a material for
esterification.
[0034] Among the above esters, the compound (A) is preferably an
ester represented by one of formulae (1), (2) and (3) below.
##STR00004##
[0035] n and m are each 0 or 1. p and q are each an integer of 0 to
3. X and Y are each an alkyl group having 1 to 30 carbon atoms that
may include a cycloalkyl group or an aromatic group, a cycloalkyl
group or an aromatic group having 5 to 12 carbon atoms, an
alkyloxycarbonyl group having 2 to 30 carbon atoms that may include
a cycloalkyl group or an aromatic group, or an alkylcarbonyloxy
group having 2 to 30 carbon atoms that may include a cycloalkyl
group or an aromatic group.
##STR00005##
[0036] n and m are each 0 or 1. p and q are each an integer of 0 to
3. X and Y are each an alkyl group having 1 to 10 carbon atoms. A
is an alkylene group having 2 to 18 carbon atoms that may contain
oxygen in a main chain and/or include a side chain.
##STR00006##
[0037] j, k, n and m are each 0 or 1. p and q are each an integer
of 0 to 3. X and Y are each an alkyl group having 1 to 10 carbon
atoms. Z is an alkylene group having 1 to 18 carbon atoms that may
include a side chain.
[0038] In the carboxylic acid ester including the aromatic ester
skeleton structure represented by the formula (1), when n or m is a
natural number of 2 or more, a bulk modulus of elasticity may be
unfavorably decreased. For this reason, a carboxylic acid ester in
which n and m are 0 or 1 is preferably used.
[0039] When p or q is a natural number of 4 or more in the formula
(1), a kinematic viscosity may become excessively high. For this
reason, a carboxylic acid ester in which p and q are each an
integer of 0 to 3 is preferably used.
[0040] In the formula (1), X and Y are each an alkyl group having 1
to 30 carbon atoms that may include a cycloalkyl group or an
aromatic group, a cycloalkyl group or an aromatic group having 5 to
12 carbon atoms, an alkyloxycarbonyl group having 2 to 30 carbon
atoms that may include a cycloalkyl group or an aromatic group, or
an alkylcarbonyloxy group having 2 to 30 carbon atoms that may
include a cycloalkyl group or an aromatic group. When each of X and
Y has 31 carbon atoms or more, the kinematic viscosity may become
excessively high. When each of X and Y has 13 carbon atoms or more,
the kinematic viscosity may become excessively high and a
low-temperature fluidity may be deteriorated.
[0041] In the carboxylic acid ester including the aromatic
carboxylic acid diester a skeleton structure of diol represented by
the formula (2), when n or m is an integer of 2 or more, the bulk
modulus of elasticity may be unfavorably decreased. For this
reason, a carboxylic acid ester in which n and m are 0 or 1 is
preferably used.
[0042] When p or q is a natural number of 4 or more in the formula
(2), the kinematic viscosity may become excessively high. For this
reason, a carboxylic acid ester in which p and q are each an
integer of 0 to 3 is preferably used.
[0043] Moreover, in the formula (2), X and Y are each an alkyl
group having 1 to 10 carbon atoms. When X and Y are each an alkyl
group having 11 carbon atoms or more, the kinematic viscosity may
become excessively high. When A is an alkylene group having 19
carbon atoms or more, the kinematic viscosity may become
excessively high.
[0044] In the carboxylic acid ester including the aromatic alcohol
diester skeleton structure of the dibasic acid represented by the
formula (3), when j or k is a natural number of 2 or more and n or
m is a natural number of 3 or more, the bulk modulus of elasticity
may be unfavorably decreased. For this reason, a carboxylic acid
ester in which j and k are 0 or 1 and n and m are an integer of 0
to 2 is preferably used.
[0045] When p or q is a natural number of 4 or more in the formula
(3), the kinematic viscosity may become excessively high. For this
reason, a carboxylic acid ester in which p and q are each an
integer of 0 to 3 is preferably used.
[0046] Moreover, in the formula (3), X and Y are each an alkyl
group having 1 to 10 carbon atoms. When X and Y are each an alkyl
group having 11 carbon atoms or more, the kinematic viscosity may
become excessively high. When Z has 19 carbon atoms or more, the
kinematic viscosity may become excessively high.
[0047] A content of the compound (A) is preferably in a range of 40
mass % to 95 mass % of a total amount of the lubricating oil
composition, more preferably in a range of 50 mass % to 95 mass %,
further preferably in a range of 60 mass % to 95 mass %. When the
content of the compound (A) is less than 40 mass %, the density
(bulk modulus of elasticity) may be hardly increased. On the other
hand, when the content of the compound (A) is more than 95 mass %,
the kinematic viscosity is also hardly decreased even by mixing the
compound (A) with the compound (B). Rather, the kinematic viscosity
of the composition may be increased.
Compound (B)
[0048] The compound (B) is an ester or ether having a kinematic
viscosity at 40 degrees C. of 12 mm.sup.2/s or less, a density at
15 degrees C. of 0.9 g/cm.sup.3 or more and a flash point of 100
degrees C. or more. The base oil in the exemplary embodiment can be
provided by blending the compound (B) with the compound (A).
[0049] When the kinematic viscosity at 40 degrees C. of the
compound (B) is more than 12 mm.sup.2/s, it is difficult to obtain
a predetermined performance of the lubricating oil composition
described below even by mixing the compound (B) with the compound
(A). When the density at 15 degrees C. of the compound (B) is less
than 0.9 g/cm.sup.3, the base oil provided by mixing the compound
(B) with the compound (A) may not have a high density (high bulk
modulus of elasticity). When the flash point of the compound (B) is
less than 100 degrees C., the flash point of the resulting
lubricating oil composition may be excessively low.
[0050] Examples of the compound (B) include adipic acid diester of
ethyleneglycolmonobutylether, adipic acid diester of
diethyleneglycolmonobutylether, 2-ethyl hexanoic acid diester of
triethyleneglycol, dibutyl sebacate, dioctyl adipate, dioctyl
azelate, dioctyl sebacate, dimethyl phthalate, diethyl phthalate,
tetraethyleneglycoldimethylether, and diethyl succinate.
[0051] A content of the compound (B) is preferably in a range of 5
mass % to 60 mass % of the total amount of the lubricating oil
composition, more preferably in a range of 5 mass % to 50 mass %,
further preferably in a range of 5 mass % to 40 mass %. When the
content of the compound (B) is less than 5 mass %, the kinematic
viscosity may not be unfavorably decreased. On the other hand, when
the content of the compound (B) is more than 60 mass %, the base
oil provided by mixing the compound (B) with the compound (A) may
have a low density (low bulk modulus of elasticity).
[0052] A total amount of the components (A) and (B) is preferably
85 mass % or more of the base oil in terms of advantages of the
invention, more preferably 87 mass % or more, further preferably 90
mass % or more.
[0053] A ratio of the compound (A) to the compound (B) in the base
oil is preferably in a range of 2 to 10 by a mass ratio ((A)/(B)),
more preferably in a range of 2.1 to 9.5. When the ratio is less
than 2, the base oil may have a low density (low bulk modulus of
elasticity). On the other hand, when the ratio is more than 10, the
base oil may have a high kinematic viscosity.
Compound (C)
[0054] The compound (C) in the exemplary embodiment is a
poly(meth)acrylate having a mass average molecular weight of 50000
or less.
[0055] The compound (C) advantageously increases the viscosity
index in the lubricating oil composition according to the exemplary
embodiment. However, when the mass average molecular weight is more
than 50000, the molecular weight is significantly reduced by shear,
so that the viscosity index of the composition is reduced by use of
the composition for a long time. On the other hand, when the mass
average molecular weight is less than 10000, the viscosity index of
the composition is not sufficiently improved.
[0056] Examples of the poly(meth)acrylate include non-dispersed
polymethacrylate and dispersed polymethacrylate. One of the
poly(meth)acrylates may be used alone or a combination of two or
more thereof may be used. A content of the compound (C) is
preferably in a range of 1 mass % to 15 mass % of the total amount
of the lubricating oil composition, more preferably in a range of 1
mass % to 10 mass %. When the content of the compound (C) is 1 mass
% or more, the viscosity index of the composition is sufficiently
improved. When the content of the compound (C) is 15 mass % or
less, the kinematic viscosity of the composition can be
reduced.
[0057] The lubricating oil composition according to the exemplary
embodiment is provided by blending the base oil containing the
compound (A) and the compound (B) with the compound (C), and
exhibits the kinematic viscosity at 40 degrees C. in a range of 20
mm.sup.2/s to 40 mm.sup.2/s, the density at 15 degrees C. of 1.1
g/cm.sup.3 or more, the flash point of 200 degrees C. or more, and
the viscosity index of 100 or more.
[0058] When the kinematic viscosity at 40 degrees C. is less than
20 mm.sup.2/s, the fluidity of the lubricating oil composition is
unfavorably excessively high. For instance, the liquid is easily
leaked from a sealed part. On the other hand, when the kinematic
viscosity is more than 40 mm.sup.2/s, flow resistance is
excessively high, which unfavorably increases consumption energy.
When the density at 15 degrees C. is less than 1.1 g/cm.sup.3, the
bulk modulus of elasticity is unfavorably excessively low. When the
flash point is less than 200 degrees C., danger of fire in a
working site is unfavorably increased. The viscosity index of less
than 100 shows an unfavorably high temperature-dependency of the
viscosity.
[0059] The lubricating oil composition according to the exemplary
embodiment can contain various additives as needed. For instance,
an antioxidant, a detergent dispersant, a friction reducer, a metal
deactivator, a pour point depressant, an antiwear agent, an
antifoaming agent, and an extreme pressure agent are usable as
needed.
[0060] Examples of the antioxidant include a phenol antioxidant
such as 2,6-di-t-butyl-4-methylphenol and
4,4'-methylenebis-(2,6-di-t-butylphenol), an amine antioxidant such
as alkylated diphenylamine, phenyl-.alpha.-naphthylamine and
alkylated-.alpha.-naphthylamine, dialkylthiodipropionate,
dialkyldithiocarbamate derivative (except for a metal salt),
bis(3,5-di-t-butyl-4-hydroxybenzyesulfide, mercaptobenzothiazole, a
reaction product of phosphorus pentasulfide and olefin and a sulfur
antioxidant such as dicetyl sulfide. One of the antioxidants is
used alone or a two or more thereof are used in combination.
Particularly, the phenol antioxidant, the amine antioxidant or zinc
alkyldithio phosphate, and a mixture thereof are preferably used. A
content of the antioxidant is preferably in a range of 0.1 mass %
to 10 mass % of the total amount of the composition.
[0061] The detergent dispersant is exemplified by alkenyl
succinimide. A content of the detergent dispersant is preferably in
a range of 0.1 mass % to 10 mass % of the total amount of the
composition.
[0062] Examples of the metal deactivator include benzotriazole and
thiadiazole, which are used either alone or in combination of two
or more thereof A content of the metal deactivator is preferably in
a range of 0.1 mass % to 5 mass %.
[0063] The pour point depressant is exemplified by a
polymethacrylate. A content of the pour point depressant is
preferably in a range of 0.5 mass % to 10 mass %.
[0064] The antiwear agent is exemplified by zinc
alkyldithiophosphate. A content of the antiwear agent is preferably
in a range of 0.1 mass % to 10 mass %.
[0065] Examples of the antifoaming agent include a silicone
compound and an ester compound, which may be used alone or in a
combination of two or more. A content of the antifoaming agent is
preferably in a range of 0.01 mass % to 1 mass %.
[0066] The extreme pressure agent is exemplified by tricresyl
phosphate. A content of the extreme pressure agent is preferably in
a range of 0.1 mass % to 10 mass %.
[0067] With this arrangement, a lubricating oil composition having
a high density (a high bulk modulus of elasticity) and a high
viscosity index can be provided. Accordingly, the lubricating oil
composition of the exemplary embodiment is preferably applicable to
various devices: hydraulic devices such as a construction machine,
injection molding machine, press machine, crane, machining center,
hydraulic continuously variable transmission, robot, machine tool,
hydraulic circuit of a hydraulic device, servo hydraulic control
circuit, damper, shock absorber, brake system, power steering and
rolling machine; rotary devices such as a pump and a compressor;
bearings such as a hydrostatic bearing, slide bearing and ball
bearing; and gears such as a spur gear, bevel gear and worm
gear.
[0068] Because of a high density and a high bulk modulus of
elasticity, the lubricating oil composition of the exemplary
embodiment particularly exhibits a high-pressure hydraulic
performance described below.
[0069] 1) An energy loss due to compression of the lubricating oil
composition is small to achieve energy saving.
[0070] 2) Response of the lubricating oil composition to hydraulic
pressure is excellent to achieve a high-speed operation in
hydraulic circuit.
[0071] 3) Stability of lubricating oil composition to the hydraulic
pressure is excellent to achieve a high precision of control in the
hydraulic pressure.
[0072] Further, due to a high density, the lubricating oil
composition of the exemplary embodiment also exhibits a
low-pressure hydraulic performance described below.
[0073] 1) Since a difference between a concentration of dissolved
gas under increased pressure and a concentration of dissolved gas
under ordinary pressure is small, less air bubbles are formed in a
reservoir tank, so that a decline of the hydraulic performance
caused by the air bubbles is significantly small.
[0074] 2) Since a difference in relative density between the air
bubbles and the lubricating oil is large, air bubbles are separated
at a high speed in a reservoir tank, so that a decline of the
hydraulic performance caused by the air bubbles is significantly
small.
[0075] 3) Since the solubility of air in the lubrication oil
composition is about one digit smaller than that in mineral oil, an
amount of dissolved gas is small, so that cavitation and erosion
are unlikely to occur (i.e., a lifetime of a hydraulic valve and
pump is prolonged).
Example(s)
[0076] Next, the above invention will be described in more detail
below with reference to Examples and Comparatives. The invention
should not be construed as limited to what is described in the
examples and the like.
Synthesis of Base Oil A-1 (Compound (A))
[0077] To a 1-L four necked flask equipped with Dean Stark, 490 g
of methyl benzoate (manufactured by Tokyo Chemical Industry Co.,
Ltd.: reagent), 233 g of polyethylene glycol 200 (manufactured by
Tokyo Chemical Industry Co., Ltd.: reagent), and 0.2 g of titanium
tetraisopropoxide (manufactured by Tokyo Chemical Industry Co.,
Ltd.: reagent) were added and reacted with stirring at 150 degrees
C. for four hours under nitrogen stream while distilling methanol.
Subsequently, the reactant was washed three times each by saturated
saline and by 0.1 N aqueous sodium hydroxide and then dried by
anhydrous magnesium sulfate (manufactured by Tokyo Chemical
Industry Co., Ltd.: reagent). After magnesium sulfate was filtered,
excessive methyl benzoate (material) was distilled to obtain 440 g
of dibenzoate of polyethylene glycol 200.
Synthesis of Base Oil A-2 (Compound (A))
[0078] A base oil A-2 was synthesized in the same manner as in
synthesis of the above base oil A-1, except for using 82 g of
diethylene glycol (manufactured by Tokyo Chemical Industry Co.,
Ltd.: reagent), 34 g of dipropylene glycol (manufactured by Tokyo
Chemical Industry Co., Ltd.: reagent) and 28 g of triethylene
glycol (manufactured by Tokyo Chemical Industry Co., Ltd.: reagent)
in place of 233 g of polyethylene glycol 200 (manufactured by Tokyo
Chemical Industry Co., Ltd.: reagent). Consequently, 320 g of an
ester mixture containing 65 mass % of dibenzoate of diethylene
glycol, 20 mass % of dibenaorte of dipropylene glycol and 15 mass %
of dibenzoate of triethylene glycol was obtained.
Preparation for Base Oils B-1 to B-7 (Compounds (B))
[0079] 500 g of each of the following commercially available
reagents was prepared. Properties are shown in Table 1.
Base Oil B-1
[0080] Adipic acid diester of diethylene glycol monobutyl ether
(manufactured by Tokyo Chemical Industry Co., Ltd.: reagent)
Base Oil B-2
[0081] Adipic acid diester of ethylene glycol monobutyl ether
(manufactured by Tokyo Chemical Industry Co., Ltd.: reagent)
Base Oil B-3
[0082] Dioctyl sebacate (manufactured by Tokyo Chemical Industry
Co., Ltd.: reagent)
Base Oil B-4
[0083] Dibutyl sebacate (manufactured by Tokyo Chemical Industry
Co., Ltd.: reagent)
Base Oil B-5
[0084] Dioctyl adipate (manufactured by Tokyo Chemical Industry
Co., Ltd.: reagent)
Base Oil B-6
[0085] Tetraethylene glycol dimethyl ether (manufactured by Tokyo
Chemical Industry Co., Ltd.: reagent)
Base Oil B-7
[0086] Diethyl phthalate (manufactured by Tokyo Chemical Industry
Co., Ltd.: reagent)
TABLE-US-00001 TABLE 1 B-1 B-2 B-3 B-4 B-5 B-6 B-7 Kinematic
viscosity at 40.degree. C., mm.sup.2/s 11.43 6.997 11.65 5.779 7.76
2.426 5.872 Kinematic viscosity at 100.degree. C., mm.sup.2/s 3.212
2.247 3.271 2.069 2.35 1.046 1.721 Viscosity index 157 141 160 188
123 -- -- Density at 15.degree. C., g/cm.sup.3 1.0256 1.0003 0.9172
0.9401 0.929 1.0153 1.1226 Flash point, .degree. C. 207 199 222 190
205 141 162
Examples 1 to 11
[0087] The base oil A-1 or A-2 was blended with the base oils B-1
to B-7 and PMA (manufactured by KURARAY CO., LTD.:
polymethylmethacrylate LW1000P in a form of beads and having 33,500
of mass average molecular weight: compound (C)) at a predetermined
ratio to be dissolved, thereby preparing sample oils. Properties of
the samples oils are shown in Tables 2 and 3.
Comparatives 1 and 2
[0088] 2 mass % of PMA (same the above) was dissolved in the base
oils A-1 and A-2, thereby preparing sample oils. Properties of the
samples oils are shown in Tables 2 and 3.
TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 Example 7 Comparative 1 A-1 (Compound A) 69 74
79 79 79 86 77 98 A-2 (Compound A) -- -- -- -- -- -- -- -- B-1
(Compound B) 29 -- -- -- -- -- -- -- B-2 (Compound B) -- 24 -- --
-- -- -- -- B-3 (Compound B) -- -- 19 -- -- -- -- -- B-4 (Compound
B) -- -- -- 19 -- -- -- -- B-5 (Compound B) -- -- -- -- 19 -- -- --
B-6 (Compound B) -- -- -- -- -- 12 -- -- B-7 (Compound B) -- -- --
-- -- -- 21 -- PMA (Compound C) 2 2 2 2 2 2 2 2 Kinematic viscosity
34.42 31.3 37.01 31.02 34.07 32.3 34.71 56.66 at 40.degree. C.,
mm.sup.2/s Kinematic viscosity 6.265 5.822 6.384 5.861 6.009 5.809
5.779 7.866 at 100.degree. C., mm.sup.2/s Viscosity index 133 131
124 135 123 123 107 104 Density at 15.degree. C., 1.1239 1.1236
1.1092 1.116 1.1121 1.1482 1.1578 1.168 g/cm.sup.3 Flash point,
.degree. C. 230 238 244 235 240 220 218 256
TABLE-US-00003 TABLE 3 Example 8 Example 9 Example 10 Example 11
Comparative 2 A-1 (Compound A) -- -- -- -- -- A-2 (Compound A) 69
74 79 78 98 B-1 (Compound B) 29 -- -- -- -- B-2 (Compound B) -- 24
-- -- -- B-3 (Compound B) -- -- 19 -- -- B-4 (Compound B) -- -- --
9.5 -- B-5 (Compound B) -- -- -- 9.5 -- B-6 (Compound B) -- -- --
-- -- B-7 (Compound B) -- -- -- -- -- PMA (Compound C) 2.5 3 2 3 2
Kinematic viscosity 32.44 31.61 29.7 31.52 43.37 at 40.degree. C.,
mm.sup.2/s Kinematic viscosity 5.743 5.646 5.119 5.56 5.896 at
100.degree. C., mm.sup.2/s Viscosity index 119 119 100 115 67
Density at 15.degree. C., 1.1239 1.1242 1.1081 1.1141 1.1667
g/cm.sup.3 Flash point, .degree. C. 224 218 230 212 236
Evaluation Results
[0089] The sample oils of Examples 1 to 7 shown in Table 2 were
provided by blending (mixing) the base oils B-1 to B-7 with the
base oil A-1 (a base material). Each of the sample oils exhibits a
high viscosity index with a high density while the viscosity of the
base oil A-1 is reduced. On the other hand, the sample oil of
Comparative 1, which was provided by adding PMA only to the base
oil A-1, exhibits a high kinematic viscosity and a low viscosity
index.
[0090] The sample oils of Examples 8 to 11 shown in Table 3 were
provided by blending the base oils B-1 to B-5 with the base oil A-2
(the base material). Each of the sample oils keeps a high density
and exhibits a high viscosity index while the viscosity of the base
oil A-2 is reduced. On the other hand, the sample oil of
Comparative 2, which was provided by adding PMA only to the base
oil A-2, exhibits a high kinematic viscosity and a low viscosity
index.
[0091] From the above results, each of the sample oils of Examples
1 to 11 is a composition having a high density (a high bulk modulus
of elasticity) and a high viscosity index within a low density
zone, from which advantages of the invention can be understood.
* * * * *