U.S. patent application number 15/541152 was filed with the patent office on 2018-01-18 for lubricating oil composition.
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 Masato KANEKO.
Application Number | 20180016518 15/541152 |
Document ID | / |
Family ID | 56416926 |
Filed Date | 2018-01-18 |
United States Patent
Application |
20180016518 |
Kind Code |
A1 |
KANEKO; Masato |
January 18, 2018 |
LUBRICATING OIL COMPOSITION
Abstract
A lubricating oil composition according to one embodiment of the
present invention contains an oxygen-containing synthetic base oil
having an oxygen content (A) of from 15 to 40 mass % and a kinetic
viscosity at 100.degree. C. of from 0.5 to 50 mm.sup.2/s, and a
viscosity index improver that is an oxygen-containing compound
having an oxygen content (B) of from 15 to 40 mass % and a kinetic
viscosity at 100.degree. C. of 11,000 mm.sup.2/s or more, a mass
ratio of the oxygen-containing synthetic base oil and the viscosity
index improver being from 99.5:0.5 to 75:25, and a ratio (A/B) of
the oxygen content (A) of the oxygen-containing synthetic base oil
to the oxygen content (B) of the viscosity index improver being in
a range of from 0.5 to 2.
Inventors: |
KANEKO; Masato;
(Ichihara-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IDEMITSU KOSAN CO., LTD. |
Chiyoda-ku |
|
JP |
|
|
Assignee: |
IDEMITSU KOSAN CO., LTD.
Chiyoda-ku
JP
|
Family ID: |
56416926 |
Appl. No.: |
15/541152 |
Filed: |
January 7, 2016 |
PCT Filed: |
January 7, 2016 |
PCT NO: |
PCT/JP2016/050404 |
371 Date: |
June 30, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10N 2030/02 20130101;
C10M 2203/003 20130101; C10N 2040/25 20130101; C10N 2040/08
20130101; C10M 2209/104 20130101; C10M 145/28 20130101; C10M 145/32
20130101; C10N 2030/70 20200501; C10M 2209/1033 20130101; C10M
2209/084 20130101; C10M 2205/026 20130101; C10N 2040/30 20130101;
C10M 2207/2835 20130101; C10M 2209/1045 20130101; C10N 2040/04
20130101; C10N 2040/02 20130101; C10M 2209/043 20130101; C10M
169/04 20130101; C10M 2205/024 20130101; C10M 2209/105 20130101;
C10M 2209/106 20130101; C10N 2020/04 20130101; C10M 171/02
20130101; C10M 169/041 20130101; C10M 2205/223 20130101; C10N
2030/08 20130101; C10M 105/00 20130101; C10M 2205/02 20130101; C10M
145/30 20130101; C10M 2209/103 20130101; C10N 2040/12 20130101;
C10M 2203/1006 20130101; C10N 2020/011 20200501; C10N 2020/02
20130101; C10M 2209/1045 20130101; C10M 2209/1055 20130101; C10M
2209/1085 20130101; C10M 2209/1045 20130101; C10M 2209/1085
20130101; C10M 2209/105 20130101; C10M 2209/108 20130101; C10M
2209/104 20130101; C10M 2209/105 20130101; C10M 2209/108 20130101;
C10M 2209/106 20130101; C10M 2209/108 20130101; C10M 2205/024
20130101; C10M 2205/04 20130101; C10N 2060/02 20130101; C10M
2205/024 20130101; C10M 2205/04 20130101; C10N 2060/02
20130101 |
International
Class: |
C10M 169/04 20060101
C10M169/04; C10M 105/00 20060101 C10M105/00; C10M 145/32 20060101
C10M145/32; C10M 145/28 20060101 C10M145/28; C10M 145/30 20060101
C10M145/30 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 2015 |
JP |
2015-007965 |
Claims
1. A lubricating oil composition, comprising: an oxygen-containing
synthetic base oil having an oxygen content (A) of from 15 to 40
mass % and a kinetic viscosity at 100.degree. C. of from 0.5 to 50
mm.sup.2/s; and a viscosity index improver that is an
oxygen-containing compound having an oxygen content (B) of from 15
to 40 mass % and a kinetic viscosity at 100.degree. C. of 11,000
mm.sup.2/s or more, wherein: a mass ratio of the oxygen-containing
synthetic base oil and the viscosity index improver is from
99.5:0.5 to 75:25; and a ratio (AB) of the oxygen content (A) of
the oxygen-containing synthetic base oil to the oxygen content (B)
of the viscosity index improver ranges from 0.5 to 2.
2. The lubricating oil composition according to claim 1, wherein
the viscosity index improver is at least one oxygen-containing
compound selected from the group consisting of a polyvinyl ether
compound, a polyoxyalkylene glycol compound, and a copolymer having
a structure of a poly(oxy)alkylene glycol or a monoether thereof
and a polyvinyl ether.
3. The lubricating oil composition according to claim 2, wherein
the viscosity index improver is a polyoxyalkylene glycol
compound.
4. The lubricating oil composition according to claim 1, wherein
the oxygen-containing synthetic base oil is at least one selected
from the group consisting of a polyvinyl ether compound, a
polyoxyalkylene glycol compound, a polyol ester compound, and a
copolymer having a structure of a poly(oxy)alkylene glycol or a
monoether thereof and a polyvinyl ether.
5. The lubricating oil composition according to claim 1, wherein
the lubricating oil composition is selected from the group
consisting of a hydraulic oil, a turbine oil, a compressor oil, a
bearing gear oil, an engine oil, and a refrigerator oil.
6. A method for producing a lubricating oil composition, the method
comprising blending a viscosity index improver that is an
oxygen-containing compound having an oxygen content (B) of from 15
to 40 mass % and a kinetic viscosity at 100.degree. C. of 11,000
mm.sup.2/s or more, with an oxygen-containing synthetic base oil
having an oxygen content (A) of from 15 to 40 mass % and a kinetic
viscosity at 100.degree. C. of from 0.5 to 50 mm.sup.2/s, wherein:
a mass ratio of the oxygen-containing synthetic base oil and the
viscosity index improver is from 99.5:0.5 to 75:25; and a ratio
(A/B) of the oxygen content (A) of the oxygen-containing synthetic
base oil to the oxygen content (B) of the viscosity index improver
ranges from 0.5 to 2.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricating oil
composition which can be applied to a refrigerator oil and various
purposes.
BACKGROUND ART
[0002] In recent years, as a base oil of a lubricating oil, an
oxygen-containing synthetic base oil, such as a polyalkylene
glycol, a polyvinyl ether, and a polyol ester, is being used in
various fields including a refrigerator oil, a hydraulic oil, and
the like.
[0003] The base oil used for a refrigerator oil, a hydraulic oil,
and the like has been variously improved, and for example, it has
been known in PTL 1 that for improving the lubrication capability
and the like, a high-viscosity base oil having a kinetic viscosity
at 100.degree. C. of from 300 to 10,000 mm.sup.2/s selected from
polyvinyl ether, a polycarbonate derivative, polyether ketone, and
polyalkylene glycol is blended with a low-viscosity base oil having
a kinetic viscosity at 100.degree. C. of from 1 to 100 mm.sup.2/s.
It has also been known in PTL 2 that for improving the
low-temperature fluidity, the wear resistance, and the like, a
high-viscosity polyalkylene glycol having a viscosity at 40.degree.
C. of from 170 to 30,000 cSt is blended with a base oil having a
viscosity at 40.degree. C. of from 170 to 1,000 cSt.
[0004] As for a lubricating oil used in fields including an engine
oil and the like, it has been widely known that a viscosity index
improver is used for the purpose of improving the viscosity index.
As the viscosity index improver, polymer materials, such as a
polymethacrylate (PMA) and an olefin copolymer (OCP), have been
widely known as one that improves the viscosity index of a mineral
oil.
CITATION LIST
Patent Literatures
[0005] PTL 1: Japanese Patent No. 3,983,328
[0006] PTL 2: Japanese Patent No. 2,952,044
SUMMARY OF INVENTION
Technical Problem
[0007] In the case where an oxygen-containing synthetic base oil is
used, there is a demand for improving the viscosity index, as
similar to the mineral oil. The viscosity index is generally
improved by blending the high-viscosity base oil components
described in PTLs 1 and 2, with an oxygen-containing synthetic base
oil, but these high-viscosity base oil components may not
sufficiently exhibit the effect of improving the viscosity index in
some cases.
[0008] Furthermore, in the case where PMA or OCP which is
conventionally used as the viscosity index improver is blended with
an oxygen-containing synthetic base oil having a large oxygen
content, PMA or OCP may be separated from the base oil and may not
sufficiently exhibit the performance as the viscosity index
improver in some cases. In particular, PMA and OCP having a large
molecular weight have a large effect of improving the viscosity
index, but have insufficient compatibility with an
oxygen-containing synthetic base oil, resulting in a tendency of
separation from the base oil. Moreover, a viscosity index improver
having a large molecular weight may raise the pour point of the
lubricating oil, resulting in decrease of the low-temperature
fluidity in some cases.
[0009] The present invention has been made in view of the
aforementioned problems, and an object thereof is to provide a
lubricating oil composition, in which even though a viscosity index
improver having a large effect of improving a viscosity index is
applied to an oxygen-containing synthetic base oil, the viscosity
index improver is hardly separated from the base oil while
retaining a good low-temperature fluidity.
Solution to Problem
[0010] As a result of earnest investigations made by the present
inventors, it has been found that the problem can be solved by
blending a viscosity index improver having an oxygen content and a
kinetic viscosity that are in prescribed ranges with an
oxygen-containing synthetic base oil having a certain oxygen
content, and thus the present invention shown below has been
completed. Accordingly, one embodiment of the present invention
provides the following.
[0011] (1) A lubricating oil composition containing an
oxygen-containing synthetic base oil having an oxygen content (A)
of from 15 to 40 mass % and a kinetic viscosity at 100.degree. C.
of from 0.5 to 50 mm.sup.2/s, and a viscosity index improver that
is an oxygen-containing compound having an oxygen content (B) of
from 15 to 40 mass % and a kinetic viscosity at 100.degree. C. of
11,000 mm.sup.2/s or more, a mass ratio of the oxygen-containing
synthetic base oil and the viscosity index improver being from
99.5:0.5 to 75:25, and a ratio (A/B) of the oxygen content (A) of
the oxygen-containing synthetic base oil to the oxygen content (B)
of the viscosity index improver being in a range of from 0.5 to
2.
[0012] (2) A method for producing a lubricating oil composition,
including: blending a viscosity index improver that is an
oxygen-containing compound having an oxygen content (B) of from 15
to 40 mass % and a kinetic viscosity at 100.degree. C. of 11,000
mm.sup.2/s or more, with an oxygen-containing synthetic base oil
having an oxygen content (A) of from 15 to 40 mass % and a kinetic
viscosity at 100.degree. C. of from 0.5 to 50 mm.sup.2/s, a mass
ratio of the oxygen-containing synthetic base oil and the viscosity
index improver being from 99.5:0.5 to 75:25, and a ratio (A/B) of
the oxygen content (A) of the oxygen-containing synthetic base oil
to the oxygen content (B) of the viscosity index improver being in
a range of from 0.5 to 2.
Advantageous Effects of Invention
[0013] According to the present invention, a lubricating oil
composition can be provided, in which even though a viscosity index
improver having a large effect of improving a viscosity index is
applied to an oxygen-containing synthetic base oil, the viscosity
index improver is hardly separated from the base oil while
retaining a good low-temperature fluidity.
DESCRIPTION OF EMBODIMENTS
[0014] The present invention will be described with reference to
embodiments below.
[0015] A lubricating oil composition according to one embodiment of
the present invention contains an oxygen-containing synthetic base
oil, and a viscosity index improver that is an oxygen-containing
compound. The components contained in the lubricating oil
composition will be described in more detail below.
[Oxygen-Containing Synthetic Base Oil]
[0016] The oxygen-containing synthetic base oil has an oxygen
content (A) of from 15 to 40 mass % and a kinetic viscosity at
100.degree. C. of from 0.5 to 50 mm.sup.2/s.
[0017] When the oxygen-containing synthetic base oil has a kinetic
viscosity at 100.degree. C. within the range, a good lubrication
performance is exhibited. When the oxygen content (A) is 40 mass %
or less, the base oil is prevented from being solidified, and when
it is 15 mass % or more, the ratio (A/B) described later can be
easily within the prescribed range, thereby facilitating the
improvement of the solubility of the viscosity index improver.
Furthermore, when the oxygen content (A) is within the range, the
compatibility with a refrigerant can be easily ensured in the case
where the lubricating oil composition is used as a refrigerator
oil, for example.
[0018] In these points of view, the oxygen content (A) is
preferably from 16 to 38 mass %, and more preferably from 19 to 32
mass %.
[0019] The kinetic viscosity at 100.degree. C. of the
oxygen-containing synthetic base oil is preferably from 1.0 to 30
mm.sup.2/s, and more preferably from 1.0 to 15 mm.sup.2/s. When the
kinetic viscosity at 100.degree. C. of the base oil is thus
lowered, the pour point can be decreased to improve the
low-temperature fluidity and the energy saving property, and thus
the lubricating oil composition can be favorably applied to various
purposes.
[0020] For example, the oxygen-containing synthetic base oil used
is selected from a polyvinyl ether compound (PVE), a
polyoxyalkylene glycol compound (PAG), a copolymer having a
structure of a poly(oxy)alkylene glycol or a monoether thereof and
a polyvinyl ether (ECP), and a polyol ester compound (POE). The use
of these base oils as the oxygen-containing synthetic base oil may
facilitate the improvement of the lubrication capability of the
lubricating oil composition. In the present embodiment, among
these, PVE, PAG, and POE are preferred, and PVE and PAG are more
preferred. The oxygen-containing synthetic base oil may be used
solely or as a combination of two or more kinds thereof. These
compounds, which can be used as the oxygen-containing synthetic
base oil, will be described in detail later.
[0021] The number average molecular weight (Mn) of the
oxygen-containing synthetic base oil is not particularly limited,
as far as the kinetic viscosity thereof is in the range, may be 100
or more, and is more preferably 150 or more. The upper limit of the
number average molecular weight is also not particularly limited,
but it is generally approximately 6,000 or less.
[0022] The oxygen-containing synthetic base oil preferably has a
volume resistivity of 10.sup.6 .OMEGA.m or more, more preferably
10.sup.7 .OMEGA.m or more, and further preferably 10.sup.8 .OMEGA.m
or more. When the volume resistivity of the base oil is increased
as above, good electric insulation property thereof may be obtained
to facilitate the application of the lubricating oil composition to
the purposes including an electric car air-conditioner and the
like. The upper limit of the volume resistivity of the base oil is
not particularly limited, but it is generally 10.sup.15 .OMEGA.m or
less. The volume resistivity is measured at room temperature of
25.degree. C. according to JIS C2101-24 (volume resistivity
test).
[0023] The saturated water content of the oxygen-containing
synthetic base oil is preferably 5 mass % or less, more preferably
3 mass % or less, and further preferably 1 mass % or less. When the
saturated water content is decreased in this way, the
hygroscopicity of the lubricating oil composition may be decreased,
and the electric insulation property and the thermal stability
thereof can be retained good for a prolonged period of time.
[0024] The saturated water content is measured in such a manner
that a specimen oil and water are mixed at a mass ratio of 1/1 and
shaken for 5 minutes, the mixture is separated to a specimen oil
layer and an aqueous layer by centrifugal separation, and the
specimen oil layer is measured for the water content by the Karl
Fischer titration method according to JIS K0113-2005.
[0025] The content of the oxygen-containing synthetic base oil in
the lubricating oil composition is preferably 70 mass % or more,
more preferably from 80 to 99.5 mass %, and further preferably from
85 to 99.5 mass %, based on the total amount of the lubricating oil
composition.
[0026] The base oil contained in the lubricating oil composition
may consist of the oxygen-containing synthetic base oil, but a
mineral oil or a synthetic base oil other than the
oxygen-containing synthetic base oil may be contained in such a
range that does not impair the effects of the present invention.
The content of mineral oil and the synthetic base oil other than
the oxygen-containing synthetic base oil is generally 10 mass % or
less, preferably 5 mass % or less, and more preferably 3 mass % or
less, based on the total amount of the lubricating oil composition.
Examples of the mineral oil include a paraffin mineral oil, a
naphthene mineral oil, and an intermediate base mineral oil, and
examples of the synthetic base oil include a poly-.alpha.-olefin,
an .alpha.-olefin copolymer, a polybutene, an alkylbenzene, and a
GTL by-product wax isomerized oil.
[Viscosity Index Improver]
[0027] In the present embodiment, the oxygen-containing compound
used as the viscosity index improver has an oxygen content (B) of
from 15 to 40 mass % and a kinetic viscosity at 100.degree. C. of
11,000 mm.sup.2/s or more. When the oxygen content (B) of the
viscosity index improver is in such a range, a ratio (A/B)
described later can be easily adjusted in the prescribed range, and
thus the viscosity index improver can be easily dissolved in the
base oil. When the oxygen content is 40 mass % or less, the
viscosity index improver can be prevented from precipitating in the
lubricating oil composition. When the kinetic viscosity is 11,000
mm.sup.2/s or more, the viscosity index of the lubricating oil
composition can be sufficiently improved.
[0028] In these points of view, the oxygen content (B) is
preferably from 16 to 38 mass %, and more preferably from 19 to 32
mass %.
[0029] The kinetic viscosity at 100.degree. C. of the viscosity
index improver is preferably from 11,000 to 120,000 mm.sup.2/s, and
more preferably from 11,000 to 100,000 mm.sup.2/s.
[0030] The number average molecular weight (Mn) of the
oxygen-containing compound used as the viscosity index improver is
appropriately determined to provide the aforementioned kinetic
viscosity range, and is generally appropriately selected from
70,000 to 1,000,000, and preferably appropriately selected from
100,000 to 1,000,000. The degree of dispersion (Mw/Mn) of the
oxygen-containing compound used as the viscosity index improver is
not particularly limited, and is generally approximately from 1.0
to 6.
[0031] For example, the oxygen-containing compound used as the
viscosity index improver is selected from a polyvinyl ether
compound (PVE), a polyoxyalkylene glycol compound (PAG), and a
copolymer having a structure of a poly(oxy)alkylene glycol or a
monoether thereof and a polyvinyl ether (ECP). The use of these
compounds may facilitate the improvement of the solubility in the
oxygen-containing synthetic base oil. Among these, PAG and PVE are
preferred, and PAG is most preferred from the standpoint that the
viscosity index can be further easily improved. The
oxygen-containing compound may be used solely or as a combination
of two or more kinds thereof. The oxygen-containing compound that
can be used as the viscosity index improver will be described in
detail later.
[0032] In the lubricating oil composition, the mass ratio of the
oxygen-containing synthetic base oil and the viscosity index
improver (oxygen-containing synthetic base oil:viscosity index
improver) is 99.5:0.5 to 75:25. In the present embodiment, when the
mass ratio is 99.5:0.5 or over, i.e., the viscosity index improver
is contained in an amount of 0.5 part by mass or more per 99.5
parts by mass of the oxygen-containing synthetic base oil, the
viscosity index of the lubricating oil composition can be
sufficiently improved. When the mass ratio is 75:25 or below, the
pour point of the lubricating oil composition can be decreased to
improve the low-temperature fluidity. In these points of view, the
mass ratio is preferably from 99.5:0.5 to 80:20, and more
preferably from 99.5:0.5 to 88:12.
[0033] The ratio (A/B) of the oxygen content (A) of the
oxygen-containing synthetic base oil to the oxygen content (B) of
the viscosity index improver is in a range of from 0.5 to 2. When
the ratio (A/B) is 0.5 or more and 2 or less, the viscosity index
improver can be prevented from being separated from the base oil,
and the viscosity index improver having a large molecular weight
can sufficiently exhibit the capability thereof.
[0034] In these points of view, the ratio (A/B) is preferably from
0.55 to L7, and more preferably from 0.65 to 1.4.
[0035] The oxygen content (A) and the oxygen content (B) are values
that are calculated from the molecular formulae of each
compound.
[0036] The compounds used in the oxygen-containing synthetic base
oil will be described in more detail below.
<Polyvinyl Ether Compound (PVE)>
[0037] The polyvinyl ether compound (PVE) used in the
oxygen-containing synthetic base oil is a polymer having a vinyl
ether-derived constituent unit, and specifically, examples thereof
include a polyvinyl-based compound having a constituent unit
represented by the following general formula (A-1).
##STR00001##
[0038] In the general formula (A-1), R.sup.1a, R.sup.2a, and
R.sup.3a each independently represent a hydrogen atom or a
hydrocarbon group having 1 to 8 carbon atoms, and they may be the
same as or different from each other. Here, specifically, examples
of the hydrocarbon group include an alkyl group, such as a methyl
group, an ethyl group, an n-propyl group, an isopropyl group, an
n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl
group, a pentyl group of every kind, a hexyl group of every kind, a
heptyl group of every kind, an octyl group of every kind, etc.; a
cycloalkyl group, such as a cyclopentyl group, a cyclohexyl group,
a methylcyclohexyl group of every kind, an ethylcyclohexyl group of
every kind, a dimethylcyclohexyl group of every kind, etc.; an aryl
group, such as a phenyl group, a methylphenyl group of every kind,
an ethylphenyl group of every kind, a dimethylphenyl group of every
kind, etc.; and an arylalkyl group, such as a benzyl group, a
phenylethyl group, a methylbenzyl group of every kind, etc. Of
those, an alkyl group is preferred. In addition, R.sup.1a,
R.sup.2a, and R.sup.3a are each more preferably a hydrogen atom or
an alkyl group having 3 or less carbon atoms, and for making the
oxygen content (A) within the aforementioned range, all R.sup.1a,
R.sup.2a, and R.sup.3a are further preferably hydrogen atoms. In
the general formula (2), r represents a repeating number, and an
average value thereof is a number ranging from 0 to 10, and
preferably from 0 to 5.
[0039] R.sup.4a represents a divalent hydrocarbon group having 2 to
10 carbon atoms. Here, specifically, examples of the divalent
hydrocarbon group having 2 to 10 carbon atoms include a divalent
aliphatic hydrocarbon group, such as an ethylene group, a
phenylethylene group, a 1,2-propylene group, a
2-phenyl-1,2-propylene group, a 1,3-propylene group, a butylene
group of every kind, a pentylene group of every kind, a hexylene
group of every kind, a heptylene group of every kind, an octylene
group of every kind, a nonylene group of every kind, a decylene
group of every kind, etc.; an alicyclic hydrocarbon group having
two bonding sites in an alicyclic hydrocarbon such as cyclohexane,
methylcyclohexane, ethylcyclohexane, dimethylcyclohexane,
propylcyclohexane, etc.; a divalent aromatic hydrocarbon group,
such as a phenylene group of every kind, a methylphenylene group of
every kind, an ethylphenylene group of every kind, a
dimethylphenylene group of every kind, a naphthylene group of every
kind, etc.; an alkyl aromatic hydrocarbon group having a monovalent
bonding site in each of an alkyl group moiety and an aromatic
moiety of an alkyl aromatic hydrocarbon such as toluene,
ethylbenzene, etc.; an alkyl aromatic hydrocarbon group having
bonding sites in an alkyl group moiety of a polyalkyl aromatic
hydrocarbon, such as xylene, diethylbenzene, etc.; and the like. Of
those, the aliphatic hydrocarbon group having 2 to 4 carbon atoms
is more preferred. Plural R.sup.4aOs may be the same as or
different from each other.
[0040] Furthermore, in the general formula (A-1), R.sup.5a
represents a hydrocarbon group having 1 to 10 carbon atoms.
Specifically, this hydrocarbon group represents an alkyl group,
such as a methyl group, an ethyl group, an n-propyl group, an
isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl
group, a tert-butyl group, a pentyl group of every kind, a hexyl
group of every kind, a heptyl group of every kind, an octyl group
of every kind, a nonyl group of every kind, a decyl group of every
kind, etc.; a cycloalkyl group, such as a cyclopentyl group, a
cyclohexyl group, a methylcyclohexyl group of every kind, an
ethylcyclohexyl group of every kind, a propylcyclohexyl group of
every kind, a dimethylcyclohexyl group of every kind, etc.; an aryl
group, such as a phenyl group, a methylphenyl group of every kind,
an ethylphenyl group of every kind, a dimethylphenyl group of every
kind, a propylphenyl group of every kind, a trimethylphenyl group
of every kind, a butylphenyl group of every kind, a naphthyl group
of every kind, etc.; or an arylalkyl group, such as a benzyl group,
a phenylethyl group, a methylbenzyl group of every kind, a
phenylpropyl group of every kind, a phenylbutyl group of every
kind, etc. Of those, a hydrocarbon group having 1 to 8 carbon atoms
is preferred, and for making the oxygen content within the
aforementioned range, an alkyl group having 2 to 4 carbon atoms is
more preferred. The alkyl groups may be any of straight-chain,
branched, and cyclic groups.
[0041] In the polyvinyl-based compound having a constituent unit
represented by the general formula (A-1), a compound containing a
constituent unit, in which all R.sup.1a, R.sup.3a, and R.sup.3a
represent hydrogen atoms, R.sup.5a represents an alkyl group having
2 to 4 carbon atoms, and r represents 0, in an amount of 80 mol %
or more is preferred, and in an amount of 100 mol % is more
preferred. Examples of the alkyl group of R.sup.5a include an ethyl
group, a n-propyl group, an isopropyl group, a n-butyl group, an
isobutyl group, a sec-butyl group, and a tert-butyl group.
Furthermore, a polymer or a copolymer containing from 50 to 100
mass % of a constituent unit in which Rya represents an ethyl
group, and from 0 to 50 mass % of a constituent unit in which Rya
represents an alkyl group having 3 or 4 carbon atoms, is
preferred.
[0042] The polyvinyl ether compound is a polymer having the
constituent unit represented by the general formula (A-1), and the
repeating number thereof may be properly chosen according to a
desired kinematic viscosity, and is generally from 3 to 80. The
aforementioned polyvinyl ether compound can be produced through
polymerization of a corresponding vinyl ether-based monomer. The
vinyl ether-based monomer that can be used herein is one
represented by the following general formula (A-2).
##STR00002##
[0043] In the formula, R.sup.1a, R.sup.2a, R.sup.3a, R.sup.4a,
R.sup.5a, and r are the same as those mentioned above.
[0044] As this vinyl ether-based monomer, there are various
monomers corresponding to the aforementioned polyvinyl ether
compounds. Examples thereof include vinyl methyl ether, vinyl ethyl
ether, vinyl n-propyl ether, vinyl isopropyl ether, vinyl n-butyl
ether, vinyl isobutyl ether, vinyl sec-butyl ether, vinyl
tert-butyl ether, vinyl n-pentyl ether, vinyl n-hexyl ether, vinyl
2-methoxyethyl ether, vinyl 2-ethoxyethyl ether, vinyl
2-methoxy-1-methylethyl ether, vinyl 2-methoxypropyl ether, vinyl
3,6-dioxaheptyl ether, vinyl 3,6,9-trioxadecyl ether, vinyl
1,4-dimethyl-3,6-dioxaheptyl ether, vinyl
1,4,7-trimethyl-3,6,9-trioxadecyl ether, vinyl 2,6-dioxa-4-heptyl
ether, vinyl 2,6,9-trioxa-4-decyl ether, 1-methoxypropene,
1-ethoxypropene, 1-n-propoxypropene, 1-isopropoxypropene,
1-n-butoxypropene, 1-isobutoxypropene, 1-sec-butoxypropene,
1-tert-butoxypropene, 2-methoxypropene, 2-ethoxypropene,
2-n-propoxypropene, 2-isopropoxypropene, 2-n-butoxypropene,
2-isobutoxypropene, 2-sec-butoxypropene, 2-tert-butoxypropene,
1-methoxy-1-butene, 1-ethoxy-1-butene, 1-n-propoxy-1-butene,
1-isopropoxy-1-butene, 1-n-butoxy-1-butene, 1-isobutoxy-1-butene,
1-sec-butoxy-1-butene, 1-tert-butoxy-1-butene, 2-methoxy-1-butene,
2-ethoxy-1-butene, 2-n-propoxy-1-butene, 2-isopropoxy-1-butene,
2-n-butoxy-1-butene, 2-isobutoxy-1-butene, 2-sec-butoxy-1-butene,
2-tert-butoxy-1-butene, 2-methoxy-2-butene, 2-ethoxy-2-butene,
2-n-propoxy-2-butene, 2-isopropoxy-2-butene, 2-n-butoxy-2-butene,
2-isobutoxy-2-butene, 2-sec-butoxy-2-butene,
2-tert-butoxy-2-butene, and the like. These vinyl ether-based
monomers can be produced by a known method.
[0045] In an end moiety of the polymer represented by the general
formula (A-1), a monovalent group derived from a saturated
hydrocarbon, an ether, an alcohol, a ketone, an amide, a nitrile,
or the like may be introduced by a known method.
[0046] Above all, as the polyvinyl ether compound, those having an
end structure of each of the following (1) to (4) are suitable.
[0047] (1) A compound in which one end thereof is represented by
the following general formula (A-1-i), and the remaining end is
represented by the following general formula (A-1-ii).
##STR00003##
[0048] In the formula, R.sup.6a, R.sup.7a, and R.sup.8a each
independently represent a hydrogen atom or a hydrocarbon group
having 1 to 8 carbon atoms, and they may be the same as or
different from each other; R.sup.9a represents a divalent
hydrocarbon group having 2 to 10 carbon atoms; R.sup.10a represents
a hydrocarbon group having 1 to 10 carbon atoms; r1 represents a
number of 0 to 10 in terms of an average value thereof, and in the
case where plural R.sup.9aOs are present, the plural R.sup.9aOs may
be the same as or different from each other.
##STR00004##
[0049] In the formula, R.sup.11a, R.sup.12a, and R.sup.13a each
independently represent a hydrogen atom or a hydrocarbon group
having 1 to 8 carbon atoms, and they may be the same as or
different from each other; R.sup.14a represents a divalent
hydrocarbon group having 2 to 10 carbon atoms; R.sup.15a represents
a hydrocarbon group having 1 to 10 carbon atoms; r2 represents a
number of 0 to 10 in terms of an average value thereof; and in the
case where plural R.sup.14aOs are present, the plural R.sup.14aOs
may be the same as or different from each other.
[0050] (2) A compound in which one end thereof is represented by
the foregoing general formula (A-1-i), and the remaining end is
represented by the following general formula (A-1-iii);
##STR00005##
[0051] In the formula, R.sup.16a, R.sup.17a, and R.sup.18a each
independently represent a hydrogen atom or a hydrocarbon group
having 1 to 8 carbon atoms, and they may be the same as or
different from each other; R.sup.19a and R.sup.21a each
independently represent a divalent hydrocarbon group having 2 to 10
carbon atoms, and they may be the same as or different from each
other; R.sup.20a and R.sup.22a each independently represent a
hydrocarbon group having 1 to 10 carbon atoms, and they may be the
same as or different from each other; r3 and r4 each represent a
number of 0 to 10 in terms of an average value thereof, they may be
the same as or different from each other; in the case where plural
R.sup.19aOs are present, the plural R.sup.19aOs may be the same as
or different from each other; and in the case where plural
R.sup.21aOs are present, the plural R.sup.21aOs may be the same as
or different from each other.
[0052] (3) A compound in which one end thereof is represented by
the foregoing general formula (A-1-i), and the remaining end has an
olefinic unsaturated bond:
[0053] (4) A compound in which one end thereof is represented by
the foregoing general formula (A-1-i), and the remaining end is
represented by the following general formula (A-1-iv):
##STR00006##
[0054] In the formula, R.sup.23a, R.sup.24a, and R.sup.25a each
represent a hydrogen atom or a hydrocarbon group having 1 to 8
carbon atoms, and they may be the same as or different from each
other.
[0055] The polyvinyl ether compound may also be a mixture of two or
more selected from those having an end structure of each of the
foregoing (1) to (4). Suitable examples of such a mixture may
include a mixture of the compound having the end structure of the
foregoing (1) and the compound having the end structure of the
foregoing (4); and a mixture of the compound having the end
structure of the foregoing (2) and the compound having the end
structure of the foregoing (3).
[0056] As for the polyvinyl ether compound, it is preferred to
choose a degree of polymerization, an end structure, and so on so
as to have a desired viscosity range. The polyvinyl ether compound
may be used solely, or it may be used in combination of two or more
thereof.
[0057] Among the polyvinyl-based compounds having the constituent
unit represented by the general formula (A-1), a compound in which
one end thereof is represented by the general formula (A-1-i), and
the remaining end is represented by the general formula (A-1-ii) is
preferred.
[0058] Above all, it is more preferred that in the formulae (A-1-i)
and (A-1-ii), all of R.sup.6a, R.sup.7a, R.sup.8a, R.sup.11a,
R.sup.12a, and R.sup.13a are a hydrogen atom, all of r1 and r2 are
0, and R.sup.10a and R.sup.15a are each an alkyl group having 1 to
4 carbon atoms.
[0059] Particularly preferred specific examples of the PVE include
a polyisobutyl vinyl ether, a polyethyl vinyl ether, an isobutyl
vinyl ether-ethyl vinyl ether copolymer, and mixtures of two or
more kinds thereof.
<Polyoxyalkylene Glycol Compound (PAG)>
[0060] Examples of the polyoxyalkylene glycol compound (PAG) used
in the oxygen-containing synthetic base oil include a compound
represented by the following general formula (B-1). The PAG may be
used either solely or in combination of two or more kinds
thereof.
R.sup.1b[--(OR.sup.2b).sub.m--OR.sup.3b].sub.n (B-1)
[0061] In the formula, R.sup.1b represents a hydrogen atom, a
monovalent hydrocarbon group having 1 to 10 carbon atoms, an acyl
group having 2 to 10 carbon atoms, a hydrocarbon group having 2 to
6 bonding sites and having 1 to 10 carbon atoms, or an
oxygen-containing hydrocarbon group having 1 to 10 carbon atoms;
R.sup.2b represents an alkylene group having 2 to 4 carbon atoms;
R.sup.3b represents a hydrogen atom, a hydrocarbon group having 1
to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, or
an oxygen-containing hydrocarbon group having 1 to 10 carbon atoms;
n represents an integer of 1 to 6; and m represents a number of 6
to 80 in terms of an average value of (m.times.n).
[0062] In the general formula (B-1), the monovalent hydrocarbon
group having 1 to 10 carbon atoms in each of R.sup.1b and R.sup.3b
may be any of straight-chain, branched, and cyclic groups. The
hydrocarbon group is preferably an alkyl group, and specific
examples thereof may include a methyl group, an ethyl group, an
n-propyl group, an isopropyl group, a butyl group of every kind, a
pentyl group of every kind, a hexyl group of every kind, a heptyl
group of every kind, an octyl group of every kind, a nonyl group of
every kind, a decyl group of every kind, a cyclopentyl group, a
cyclohexyl group, and the like. As for the aforementioned
monovalent hydrocarbon group, when the number of carbon atoms is 10
or less, the oxygen content (A) can be easily within the prescribed
range, and the compatibility with the refrigerant becomes good when
the lubricating oil composition is used as a refrigerator oil. From
such a viewpoint, the number of carbon atoms of the monovalent
hydrocarbon group is more preferably 1 to 4.
[0063] The hydrocarbon group moiety which the acyl group having 2
to 10 carbon atoms in each of R.sup.1b and R.sup.3b has may be any
of straight-chain, branched, and cyclic groups. The hydrocarbon
group moiety of the acyl group is preferably an alkyl group, and
specific examples thereof include those having 1 to 9 carbon atoms
among the alkyl groups which may be chosen as the aforementioned
Rib and R.sup.3b. When the number of carbon atoms of the acyl group
is 10 or less, the oxygen content (A) can be easily within the
prescribed range, and the compatibility with the refrigerant
becomes good when the lubricating oil composition is used in a
refrigerator oil. The number of carbon atoms of the acyl group is
preferably 2 to 4.
[0064] In the case where all of R.sup.1b and R.sup.3b are a
hydrocarbon group or an acyl group, R.sup.1b and R.sup.3b may be
the same as or different from each other.
[0065] In the case where R.sup.1b is the hydrocarbon group having 2
to 6 bonding sites and having 1 to 10 carbon atoms, this
hydrocarbon group may be either linear or cyclic. The hydrocarbon
group having 2 bonding sites is preferably an aliphatic hydrocarbon
group, and examples thereof include an ethylene group, a propylene
group, a butylene group, a pentylene group, a hexylene group, a
heptylene group, an octylene group, a nonylene group, a decylene
group, a cyclopentylene group, a cyclohexylene group, and the like.
Examples of the other hydrocarbon groups may include residues
resulting from removing a hydroxyl group from a bisphenol compound
such as bisphenol, bisphenol F, bisphenol A, etc. The hydrocarbon
group having 3 to 6 bonding sites is preferably an aliphatic
hydrocarbon group, and examples thereof may include residues
resulting from removing a hydroxyl group from a polyhydric alcohol,
such as trimethylolpropane, glycerin, pentaerythritol, sorbitol,
1,2,3-trihydroxycyclohexane, 1,3,5-trihydroxycyclohexane, etc.
[0066] When the number of carbon atoms of this aliphatic
hydrocarbon group is 10 or less, the oxygen content (A) can be
easily within the prescribed range, and the compatibility with the
refrigerant becomes good when the lubricating oil composition is
used as a refrigerator oil. The number of carbon atoms of this
aliphatic hydrocarbon group is preferably 2 to 6.
[0067] Furthermore, examples of the oxygen-containing hydrocarbon
group having 1 to 10 carbon atoms in each of R.sup.1b and R.sup.3b
may include an ether bond-containing linear or cyclic aliphatic
group (for example, a tetrahydrofurfuryl group), and the like.
[0068] At least one of R.sup.1b and R.sup.3b is preferably an alkyl
group, especially an alkyl group having 1 to 4 carbon atoms.
[0069] R.sup.2b in the general formula (B-1) is an alkylene group
having 2 to 4 carbon atoms, and examples of the oxyalkylene group
as a repeating unit include an oxyethylene group, an oxypropylene
group, and an oxybutylene group. The oxyalkylene groups in one
molecule may be the same as each other, and two or more kinds of
oxyalkylene groups may also be contained. It is preferred that at
least an oxypropylene unit is contained in one molecule, and it is
more preferred that 50 mol % or more of an oxypropylene unit is
contained in the oxyalkylene unit, and it is more preferred that 70
mol % or more of an oxypropylene unit is contained therein. When
the content of the oxypropylene unit is large, for example, the
saturated moisture content can be lower to decrease the
hygroscopicity, and the oxygen content (A) can be easily within the
prescribed range.
[0070] In the general formula (B-1), n is an integer of 1 to 6 and
is determined according to the number of bonding sites of Rib. For
example, in the case where R.sup.1b is an alkyl group or an acyl
group, then n is 1; and in the case where R.sup.1b is an aliphatic
hydrocarbon group having 2, 3, 4, 5, or 6 bonding sites, then n is
2, 3, 4, 5, or 6, respectively.
[0071] m is a number providing an average value of m.times.n of 6
to 80. When the average value is 80 or less, the base oil can
exhibit the lubrication performance, and the compatibility with a
refrigerant may be improved when the lubricating oil composition is
used as a refrigerator oil. The average value of m.times.n is
determined in such a manner that the viscosity of the base oil is
in the desired range.
[0072] n is preferably an integer of 1 to 3, and more preferably 1.
In the case where n is 1, it is preferred that any one of R.sup.1b
and R.sup.3b represents an alkyl group, and it is more preferred
that both of them each represent an alkyl group. Similarly, in the
case where n is 2 or more, it is preferred that any one of plural
R.sup.3bs in one molecule represents an alkyl group, and it is more
preferred that all of them each represent an alkyl group.
[0073] In the case where n is 2 or more, plural R.sup.3bs in one
molecule may be the same as or different from each other.
[0074] Preferred examples of the PAG used as the base oil include a
mono- or dialkyl ether of a polyoxypropylene glycol, a mono- or
dialkyl ether of a polyoxyethylene glycol polyoxypropylene glycol,
and a mixture of two or more kinds of these compounds; namely ones
represented by the general formula (B-1), in which R.sup.2b
represents a propylene group or a combination of an ethylene group
and a propylene group, n is 1, and one or both of R.sup.1b and
R.sup.3b are an alkyl group having 1 to 4 carbon atoms with the
balance being a hydrogen atom, and more specifically include a
polyoxypropylene glycol dimethyl ether, a polyoxypropylene glycol
monobutyl ether, a polyoxyethylene glycol polyoxypropylene glycol
dimethyl ether, and a mixture of two or more kinds of these
compounds.
<Copolymer Having Structure of Poly(Oxy)Alkylene Glycol or
Monoether Thereof and Polyvinyl Ether (ECP)>
[0075] In the lubricating oil composition according to the present
embodiment, examples of the copolymer having a structure of a
poly(oxy)alkylene glycol or a monoether thereof and a polyvinyl
ether (ECP) that can be used as the oxygen-containing synthetic
base oil include a copolymer represented by the following general
formula (C-1) and a copolymer represented by the following general
formula (C-2) (hereinafter referred to as "polyvinyl ether
copolymer I" and "polyvinyl ether copolymer II", respectively). The
poly(oxy)alkylene glycol refers to both a polyalkylene glycol and a
polyoxyalkylene glycol.
##STR00007##
[0076] In the general formula (C-1), R.sup.1c, R.sup.2c, and
R.sup.3c each independently represent a hydrogen atom or a
hydrocarbon group having 1 to 8 carbon atoms, and they may be the
same as or different from each other; R.sup.5c represents a
divalent hydrocarbon group having 2 to 4 carbon atoms; R.sup.6c
represents an aliphatic or alicyclic hydrocarbon group having 1 to
20 carbon atoms, an aromatic hydrocarbon group having 1 to 20
carbon atoms which may have a substituent, an acyl group having 2
to 20 carbon atoms, or an oxygen-containing hydrocarbon group
having 2 to 50 carbon atoms; R.sup.4c represents a hydrocarbon
group having 1 to 10 carbon atoms; and in the case where a
plurality of each of R.sup.1c to R.sup.6c are present, they may be
each the same as or different from each other.
[0077] Here, specifically, the hydrocarbon group having 1 to 8
carbon atoms in R.sup.1c to R.sup.3c represents an alkyl group,
such as a methyl group, an ethyl group, an n-propyl group, an
isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl
group, a tert-butyl group, a pentyl group of every kind, a hexyl
group of every kind, a heptyl group of every kind, an octyl group
of every kind, etc.; a cyclopentyl group, a cyclohexyl group, a
methylcyclohexyl group of every kind, an ethylcyclohexyl group of
every kind, a dimethylcyclohexyl group of every kind, an aryl group
such as a dimethylphenyl group of every kind, etc.; or an arylalkyl
group, such as a benzyl group, a phenylethyl group, a methylbenzyl
group of every kind, etc. R.sup.1c, R.sup.2c, and R.sup.3c are each
preferably a hydrogen atom for making the oxygen content (B) within
the aforementioned range.
[0078] Meanwhile, specifically, the divalent hydrocarbon group
having 2 to 4 carbon atoms as represented by R.sup.5c is a divalent
alkylene group, such as a methylene group, an ethylene group, a
propylene group of every kind, a butylene group of every kind,
etc.
[0079] In the general formula (C-1), v represents a repeating
number of R.sup.5cO, and is a number ranging from 1 to 50,
preferably from 1 to 20, more preferably from 1 to 10, and
especially preferably from 1 to 5 in terms of an average value
thereof. In the case where plural R.sup.5cOs are present, the
plural R.sup.5cOs may be the same as or different from each other.
v may be the same as or different from each other in every
constituent unit.
[0080] w represents a number of 1 to 50, preferably 1 to 10, more
preferably 1 to 2, and especially preferably 1; u represents a
number of 0 to 50, preferably 2 to 25, and more preferably 5 to 15;
and in the case where a plurality of each of w and u are present,
they may be either block or random.
[0081] Furthermore, in the general formula (C-1), R.sup.6c
preferably represents an alkyl group having 1 to 10 carbon atoms,
an acyl group having 2 to 10 carbon atoms, or an oxygen-containing
hydrocarbon group having 2 to 50 carbon atoms.
[0082] Specifically, this alkyl group having 1 to 10 carbon atoms
represents a methyl group, an ethyl group, an n-propyl group, an
isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl
group, a tert-butyl group, a pentyl group of every kind, a hexyl
group of every kind, a heptyl group of every kind, an octyl group
of every kind, a nonyl group of every kind, a decyl group of every
kind, a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl
group of every kind, an ethylcyclohexyl group of every kind, a
propylcyclohexyl group of every kind, a dimethylcyclohexyl group of
every kind, or the like.
[0083] Examples of the acyl group having 2 to 10 carbon atoms
include an acetyl group, a propionyl group, a butyryl group, an
isobutyryl group, a valeryl group, an isovaleryl group, a pivaloyl
group, a benzoyl group, a toluoyl group, and the like.
[0084] Furthermore, a methoxymethyl group, a methoxyethyl group, a
methoxypropyl group, a 1,1-bismethoxypropyl group, a
1,2-bismethoxypropyl group, an ethoxypropyl group, a
(2-methoxyethoxy)propyl group, a (1-methyl-2-methoxy)propyl group,
and the like are preferably exemplified as specific examples of the
oxygen-containing hydrocarbon group having 2 to 50 carbon
atoms.
[0085] In the general formula (C-1), specifically, the hydrocarbon
group having 1 to 10 carbon atoms as represented by R.sup.4c
represents an alkyl group, such as a methyl group, an ethyl group,
an n-propyl group, an isopropyl group, an n-butyl group, an
isobutyl group, a pentyl group of every kind, a hexyl group of
every kind, a heptyl group of every kind, an octyl group of every
kind, a nonyl group of every kind, a decyl group of every kind,
etc.; a cycloalkyl group, such as a cyclopentyl group, a cyclohexyl
group, a methylcyclohexyl group of every kind, an ethylcyclohexyl
group of every kind, a propylcyclohexyl group of every kind, a
dimethylcyclohexyl group of every kind, etc.; an aryl group, such
as a phenyl group, a methylphenyl group of every kind, an
ethylphenyl group of every kind, a dimethylphenyl group of every
kind, a propylphenyl group of every kind, a trimethylphenyl group
of every kind, a butylphenyl group of every kind, a naphthyl group
of every kind, etc.; an arylalkyl group, such as a benzyl group, a
phenylethyl group of every kind, a methylbenzyl group of every
kind, a phenylpropyl group of every kind, a phenylbutyl group of
every kind, etc.; or the like.
[0086] The polyvinyl ether copolymer I having the constituent unit
represented by the general formula (C-1) is able to improve
lubricating properties, insulating properties, hygroscopicity, and
so on while improving the compatibility with the refrigerant when
the lubricating oil composition is used in a refrigerator oil,
through formation of the copolymer.
[0087] Meanwhile, in the polyvinyl ether copolymer II represented
by the general formula (C-2), R.sup.1c to R.sup.5c and v are the
same as those mentioned above. In the case where a plurality of
each of R.sup.4c and R.sup.5c are present, they may be each the
same as or different from each other. x and y each represent a
number of 1 to 50, and in the case where a plurality of each of x
and y are present, they may be either block or random. X.sup.c and
Y.sup.c each independently represent a hydrogen atom, a hydroxyl
group, or a hydrocarbon group having 1 to 20 carbon atoms.
[0088] It is preferred that the repeating numbers u, w, x, and y in
the general formulae (C-1) and (C-2) are properly chosen such that
a desired viscosity as mentioned later is obtained. A production
method of each of the polyvinyl ether copolymers I and II is not
particularly limited so long as it is a method for which each of
the polyvinyl ether copolymers I and II is obtained.
[0089] The vinyl ether-based copolymers I and II represented by the
general formulae (C-1) and (C-2) can be formed into the polyvinyl
ether copolymer I having a structure in which one end thereof is
represented by the following general formula (C-3) or (C-4), and
the remaining end is represented by the following general formula
(C-5) or (C-6).
##STR00008##
[0090] In the aforementioned (C-3) and (C-4), R.sup.1c to R.sup.6c
and v are the same as those as mentioned above.
##STR00009##
[0091] In the aforementioned (C-5) and (C-6), R.sup.1c to R.sup.6c
and v are the same as those as mentioned above.
<Polyol Ester Compound (POE)>
[0092] In the lubricating oil composition, examples of the polyol
ester compound (POE) that can be used as the oxygen-containing
synthetic base oil include an ester of a diol or a polyol having 3
to 20 hydroxyl groups and a fatty acid having 1 to 24 carbon atoms.
However, the fatty acid for forming the polyol ester generally
needs to contain a fatty acid having 12 or less carbon atoms in
such a manner that the oxygen content (A) is 15 mass % or more.
[0093] Here, examples of the diol include ethylene glycol,
1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol,
2-methyl-1, 3-propanediol, 1,5-pentanediol, neopentyl glycol,
1,6-hexanediol, 2-ethyl-2-methyl-1,3-propane, 1, 7-heptanediol,
2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol,
1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol,
1,12-dodecanediol, and the like. Examples of the polyol include a
polyhydric alcohol, such as trimethylolethane, trimethylolpropane,
trimethylolbutane, ditrimethylolpropane, tritrimethylolpropane,
pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, a
polyglycerin (e.g., dimer to icosamer of glycerin),
1,3,5-pentanetriol, sorbitol, sorbitan, a sorbitol glycerin
condensate, adonitol, arabitol, xylitol, mannitol, etc.; a
saccharide, such as xylose, arabinose, ribose, rhamnose, glucose,
fructose, galactose, mannose, sorbose, cellobiose, maltose,
isomaltose, trehalose, sucrose, raffinose, gentianose, merenditose,
etc.; a partially etherified product thereof; methyl glucoside
(e.g. glucosides); and the like. Above all, hindered alcohols, such
as neopentyl glycol, trimethylolethane, trimethylolpropane,
trimethylolbutane, ditrimethylolpropane, tritrimethylolpropane,
pentaerythritol, dipentaerythritol, tripentaerythritol, etc., are
preferred as the polyol.
[0094] As for the fatty acid, those having 1 to 24 carbon atoms are
used as described above, and those having 3 or more carbon atoms
are preferred, those having 4 or more carbon atoms are more
preferred, and those having 5 or more carbon atoms are still more
preferred from standpoint of lubricating properties. For the fatty
acid for making the oxygen content (A) of 15 mass % or more, those
having 12 or less carbon atoms are preferred, and those having 9 or
less carbon atoms are more preferred.
[0095] The fatty acid may be any of a straight-chain fatty acid and
a branched fatty acid, a straight-chain fatty acid is preferred
from the standpoint of lubricating properties, and a branched fatty
acid is preferred from the standpoint of hydrolysis stability.
Furthermore, the fatty acid may be any of a saturated fatty acid
and an unsaturated fatty acid.
[0096] Examples of the fatty acid include a straight-chain or
branched fatty acid, such as isobutyric acid, pentanoic acid,
hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid,
decanoic acid, undecanoic acid, dodecanoic acid, etc.; a so-called
neo acid in which an .alpha.-carbon atom is quaternary; and the
like. More specifically, isobutyric acid, valeric acid (n-pentanoic
acid), caproic acid (n-hexanoic acid), enanthic acid (n-heptanoic
acid), caprylic acid (n-octanoic acid), pelargonic acid (n-nonanoic
acid), capric acid (n-decanoic acid), isopentanoic acid
(3-methylbutanoic acid), 2-methylhexanoic acid, 2-ethylpentanoic
acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, and the
like are preferred.
[0097] The polyol ester may be a partial ester in which some of the
hydroxyl groups of a polyol remain without being esterified, may be
a complete ester in which all of the hydroxyl groups of the polyol
are esterified, or may be a mixture of the partial ester and the
complete ester, but the polyol ester is preferably the complete
ester.
[0098] Among the polyol esters, due to the excellent hydrolysis
stability, esters of a hindered alcohol, such as neopentyl glycol,
trimethylolethane, trimethylolpropane, trimethylolbutane,
ditrimethylolpropane, tritrimethylolpropane, pentaerythritol,
dipentaerythritol, and tripentaerythritol, are preferred, and
esters of neopentyl glycol, trimethylolethane, trimethylolpropane,
trimethylolbutane, and pentaerythritol are more preferred.
[0099] Specific examples of the preferred polyol ester include a
diester of neopentyl glycol and one or more kinds of fatty acids
selected from isobutyric acid, valeric acid, caproic acid, enanthic
acid, caprylic acid, pelargonic acid, capric acid, isopentanoic
acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic
acid, and 3,5,5-trimethylhexanoic acid; a triester of
trimethylolethane and one or more kinds of fatty acids selected
from isobutyric acid, valeric acid, caproic acid, enanthic acid,
caprylic acid, pelargonic acid, capric acid, isopentanoic acid,
2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid,
and 3,5,5-trimethylhexanoic acid; a triester of trimethylolpropane
and one or more kinds of fatty acids selected from isobutyric acid,
valeric acid, caproic acid, enanthic acid, caprylic acid,
pelargonic acid, capric acid, isopentanoic acid, 2-methylhexanoic
acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and
3,5,5-trimethylhexanoic acid; a triester of trimethylolbutane and
one or more kinds of fatty acids selected from isobutyric acid,
valeric acid, caproic acid, enanthic acid, caprylic acid,
pelargonic acid, capric acid, isopentanoic acid, 2-methylhexanoic
acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and
3,5,5-trimethylhexanoic acid; and a tetraester of pentaerythritol
and one or more kinds of fatty acids selected from isobutyric acid,
valeric acid, caproic acid, enanthic acid, caprylic acid,
pelargonic acid, capric acid, isopentanoic acid, 2-methylhexanoic
acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and
3,5,5-trimethylhexanoic acid. As a more preferred specific example
among the above, pentaerythritol tetra-2-ethylhexyl ester is
particularly preferred.
[0100] The ester of two or more kinds of fatty acids may be a
mixture of two or more kinds of esters, each of which is an ester
of one kind of fatty acid and a polyol, or may be an ester of a
mixed fatty acid of two or more kinds thereof and a polyol.
Particularly, an ester of a mixed fatty acid and a polyol is
excellent in low-temperature properties, and is excellent in
compatibility with the refrigerant when the lubricating oil
composition is used as a refrigerator oil.
[0101] The compound used as the viscosity index improver will be
described in detail.
[0102] A polyvinyl ether compound (PVE) used as the viscosity index
improver is a polymer having a vinyl ether-derived constituent
unit, and specifically, examples thereof include a polyvinyl-based
compound having a constituent unit represented by the general
formula (A-1), as similar to the oxygen-containing synthetic base
oil. However, the repeating number of the constituent unit
represented by the general formula (A-1) is appropriately selected
depending on the desired kinetic viscosity, and the repeating
number is sufficiently larger than that used as the
oxygen-containing synthetic base oil, and is generally
approximately from 1,000 to 14,000. The detailed explanations of
the PVE used as the viscosity index improver are same as those for
the PVE used in the oxygen-containing synthetic base oil, except
for the repeating number, and the explanations thereof are omitted
herein.
[0103] Incidentally, specific examples of the PVE used as the
viscosity index improver include the same kinds as for the
oxygen-containing synthetic base oil, and among them, a polyethyl
vinyl ether is most preferred.
[0104] Examples of the polyoxyalkylene glycol compound (PAG) used
as the viscosity index improver include a compound represented by
the general formula (B-1), as similar to the oxygen-containing
synthetic base oil. The detailed explanations of R.sup.1b,
R.sup.2b, n, and R.sup.3b in the general formula (B-1) are the same
as above except for the following differences. Only the differences
are described below, but the others are the same and not described
herein.
[0105] Specifically, while m in the general formula (B-1) for the
oxygen-containing synthetic base oil is a number providing an
average value of m.times.n of 6 to 80, m for the viscosity index
improver is a number providing an average value of m.times.n of
approximately 1,800 to 20,000. However, m is appropriately changed
corresponding to the kinetic viscosity and the number average
molecular weight of the viscosity index improver described
above.
[0106] Moreover, in the viscosity index improver, at least one of
R.sup.1b and R.sup.3b preferably represents a hydrogen atom. For
example, in the case where n is 1, any one of R.sup.1b and R.sup.3b
preferably represents a hydrogen atom, and in the case where n is 2
or more, any one of plural R.sup.3bs in one molecule preferably
represents a hydrogen atom.
[0107] In the case where both the oxygen-containing synthetic base
oil and the viscosity index improver are PAG, both the
oxygen-containing synthetic base oil and the viscosity index
improver used are generally ones represented by the general formula
(B-1), and in both the compounds, n in the general formula (B-1) is
preferably an integer of from 1 to 3, and more preferably 1. By
using the oxygen-containing synthetic base oil and the viscosity
index improver having structures of the same kind, the
aforementioned various effects can be easily obtained.
[0108] Specific particularly preferred examples of the PAG used as
the viscosity index improver include a polyoxypropylene glycol, a
polyoxyethylene glycol polyoxypropylene glycol, polyoxybutylene
glycol, and monoalkyl ethers of these compounds; namely, ones
represented by the general formula (B-1), in which R.sup.2b
represents a propylene group, a butylene group, or a combination of
an ethylene group and a propylene group, n is 1, and one or both of
R.sup.1b and R.sup.3b are a hydrogen atom with the balance being an
alkyl group having 1 to 4 carbon atoms, and more specifically
include a polyoxypropylene glycol diol (both ends are hydroxyl
groups), a polyoxypropylene glycol monobutyl ether, a
polyoxyethylene glycol polyoxypropylene glycol olio' (both ends are
hydroxyl groups), and a polyoxybutylene glycol monobutyl ether.
[0109] While the production method of the PAG used as the viscosity
index improver is not particularly limited, the PAG is preferably
produced, for example, by polymerizing an alkylene oxide by using a
composite metal catalyst, from the standpoint of easily producing
one having a large viscosity.
[0110] The composite metal catalyst is preferably a composite metal
cyanide complex catalyst. Specific examples of the composite metal
cyanide complex catalyst include a compound having a structure
represented by the following general formula (A).
M.sub.a[M'.sub.x(CN).sub.y].sub.b(H.sub.2O).sub.c(R).sub.d (A)
[0111] In the general formula, M represents Zn(II), Fe(III),
Ni(II), Sr(II), Cu(II), Sn(II), Mo(IV), Mo(VI), W(IV), W(VI), or
the like; M' represents Fe(II), Fe(III), Cr(II), Mn(II), Mn(III),
V(IV), V(V), or the like; R represents an organic ligand; a, b, x,
and y each are a positive integer that vary depending on the
valency and the coordination number of the metal; and c and d each
are a positive number that vary depending on the coordination
number of the metal.
[0112] In the general formula (A), M preferably represents Zn(II),
and M' preferably represents Fe(II), Co(III), or the like. Examples
of the organic ligand include a ketone, an ether, an aldehyde, an
ester, an alcohol, and an amide, and an alcohol is preferred.
[0113] The composite metal cyanide complex represented by the
general formula (A) may be produced in such a manner that: a metal
salt MX.sub.a (wherein M and a are the same as above, and X
represents an anion forming a salt with M); and a
polycyanometallate (salt) Z.sub.e[M'.sub.x(CN).sub.y].sub.f
(wherein M', x, and y are the same as above, Z represents hydrogen,
an alkali metal, an alkaline earth metal, or the like, and e and f
each represent a positive integer determined by the valency and the
coordination number of M'), each of which is in aqueous solution or
mixed solvent solution of water and an organic solvent, are mixed
to obtain a composite metal cyanide complex, the organic ligand R
is made contact with the obtained composite metal cyanide complex,
and then the excessive solvent and the excessive organic ligand R
are removed.
[0114] In the polycyanometallate (salt)
Z.sub.e[M'.sub.x(CN).sub.y].sub.f, hydrogen and various metals,
such as an alkali metal, can be used as Z, and a lithium salt, a
sodium salt, a potassium salt, a magnesium salt, and a calcium salt
are preferred. What are particularly preferred are normal alkali
metal salts, i.e., a sodium salt and a potassium salt.
[0115] The PAG used as the viscosity index improver is generally
produced by making a mixture of the alkylene oxide and an initiator
in contact with the catalyst, and a particular amount of an organic
solvent is preferably present in the reaction. The presence of an
organic solvent may increase the molecular weight of the PAG. The
reaction may also be performed by adding the alkylene oxide
gradually to the reaction system, and an organic solvent may be
added along with the alkylene oxide. While the reaction may occur
under ordinary temperature, the reaction system may be heated or
cooled, and a large molecular weight can be easily obtained by
cooling. The specific reaction temperature is preferably from -20
to 100.degree. C. The amount of the catalyst used is not
particularly limited, and is suitably from 1 to 5,000 ppm based on
the initiator used. The catalyst may be introduced to the reaction
system at one time at the beginning of the reaction or may be
divided and introduced sequentially.
[0116] The amount of the organic solvent present in the reaction is
preferably 10 to 90 mass % based on the amount of the PAG finally
obtained. When the amount of the organic solvent is 10 mass % or
more, the molecular weight of the PAG can be further increased.
When the amount thereof is 90 mass % or less, the PAG can be
produced with good economic efficiency.
[0117] The organic solvent used may be various organic solvents,
and is preferably an ether compound. Examples of the ether compound
include a monoether, a diether, a polyether compound, a polyvinyl
ether compound, and a polyalkylene glycol compound.
[0118] Examples of the monoether include a dialkyl ether, in which
the alkyl group is a branched or straight-chain alkyl group having
1 to 12 carbon atoms, and specific examples thereof include a
symmetrical ether, such as di-2-ethylhexyl ether and
di-3,5,5-trimethylhexyl ether, and an asymmetrical ether, such as
2-ethylhexyl n-octyl ether and 3,5,5-trimethylhexyl n-nonyl
ether.
[0119] The diether used may be, for example, a dialkyl ether of
various diols. Examples of the diol used include a
straight-chain-alkane diol, such as an alkylene glycol, e.g.,
ethylene glycol, propylene glycol, and butylene glycol,
1,3-propanediol, and 1,4-butanediol; and a branched-alkene diol,
such as neopentyl glycol. Examples of the polyether used include
alkyl ethers of a polyhydric alcohol, such as glycerin,
tetramethylolethane, tetramethylolpropane, pentaerythritol, and
dipentaerythritol.
[0120] The alkyl group used in the dialkyl ether and the alkyl
ether of a polyhydric alcohol may be a branched or straight-chain
alkyl group having 1 to 12 carbon atoms. The alkyl group of the
diether and the polyether may be used solely, or it may be used in
combination of two or more thereof.
[0121] The polyvinyl ether compound and the polyalkylene glycol
compound used as the organic solvent can be similar to those used
as the oxygen-containing synthetic base oil. However, the
polyalkylene glycol compound that has a --OH group at the end
thereof may have a possibility of reaction with a monomer, and
therefore the compound having the end that is etherified with an
alkyl group having 1 to 4 carbon atoms can be used. Specifically,
in the case where n in the formula (B-1) is 1, the compound in
which both R.sup.1b and R.sup.3b each represent an alkyl group
having 1 to 4 carbon atoms can be used. Similarly, in the case
where n is 2 or more, the compound in which all of plural R.sup.3bs
in one molecule each represent an alkyl group having 1 to 4 carbon
atoms can be used. Similarly, as the polyvinyl ether compound, the
compound having the end that has no --OH group may be used.
[0122] After completing the reaction, the organic solvent may be
removed partially or entirely, and may not be removed. In the case
where at least a part of the organic solvent is not removed after
the reaction, the organic solvent is contained in the lubricating
oil composition along with the viscosity index improver (PAG), and
used as at least a part of the oxygen-containing synthetic base
oil. Accordingly, in the case where the organic solvent is used as
at least a part of the base oil, the organic solvent used is
preferably a polyvinyl ether compound or a polyalkylene glycol
compound capable of being used as the oxygen-containing synthetic
base oil.
[0123] The initiator may be appropriately selected depending on the
structure of the PAG to be produced, and in the case where the
resulting PAG is represented by the general formula (B-1), the
initiator is preferably an alcohol compound represented by the
general formula, R.sup.1b(OH).sub.n or HO--R.sup.2b--OH (wherein
Rib, n, and R.sup.2b are the same as above).
[0124] The alkylene oxide may be appropriately selected
corresponding to R.sup.2b in the general formula (B-1), and
examples thereof include ethylene oxide, propylene oxide, and a
butylene oxide.
[0125] The PAG thus obtained after the reaction contains the
catalyst and the organic solvent, and thus at least the catalyst is
necessarily removed. The processing method therefor is preferably,
for example, such a method that a catalyst deactivator, such as an
alkali metal compound, is added to deactivate the catalyst, and
then the compound is purified.
[0126] Examples of the copolymer having a structure of a
poly(oxy)alkylene glycol or a monoether thereof and a polyvinyl
ether (ECP) used as the viscosity index improver include a
copolymer represented by the general formula (C-1) and a copolymer
represented by the general formula (C-2). However, in the ECP used
as the viscosity index improver, the repeating number of the
constituent unit is larger than that of the ECP used as the base
oil, and w, u, v, x, and y in the general formulae (C-1) and (C-2)
are not limited to the aforementioned ranges, and are appropriately
determined corresponding to the viscosity of the viscosity index
improver. The detailed explanations of ECP used as the viscosity
index improver are the same as the oxygen-containing synthetic base
oil except for the repeating numbers, and the explanations thereof
are omitted herein.
[Other Additives]
[0127] The lubricating oil composition according to the present
embodiment may further contain various additives. The additives are
contained preferably in an amount of about 20 mass % or less, and
more preferably about 0 to 10 mass %, based on the total amount of
the lubricating oil composition. Various materials may be used as
the additives, and examples thereof include an antioxidant, an acid
scavenger, an oxygen scavenger, an extreme pressure agent, an
oiliness agent, a copper deactivator, a rust preventive, and a
defoaming agent.
[0128] Examples of the antioxidant include a phenol-based
antioxidant, such as 2,6-di-tert-butyl-4-methylphenol,
2,6-di-tert-butyl-4-ethylphenol,
2,2'-methylenebis(4-methyl-6-tert-butylphenol), etc.; and an amine
type antioxidant, such as phenyl-.alpha.-naphthylamine,
N,N'-di-phenyl-p-phenylenediamine, etc., and a phenol-based
antioxidant is preferred. From the standpoints of effects and
economy, and so on, the content of the antioxidant is typically
0.01 to 5 mass %, and preferably 0.05 to 3 mass %, based on the
total amount of the lubricating oil composition.
[0129] Examples of the acid scavenger may include an epoxy
compound, such as phenyl glycidyl ether, an alkyl glycidyl ether,
an alkylene glycol glycidyl ether, cyclohexene oxide, an
.alpha.-olefin oxide, an epoxidized soybean oil, etc. Above all,
from the standpoint of compatibility, phenyl glycidyl ether, an
alkyl glycidyl ether, an alkylene glycol glycidyl ether,
cyclohexene oxide, and an .alpha.-olefin oxide are preferred.
[0130] Regarding the alkyl group in the alkyl glycidyl ether and
the alkylene group in the alkylene glycol glycidyl ether, the
branched is also acceptable, and the number of carbon atoms thereof
is typically 3 to 30, preferably 4 to 24, and especially preferably
6 to 16. As for the .alpha.-olefin oxide, one having a total number
of carbon atoms of generally 4 to 50, preferably 4 to 24, and
especially 6 to 16 is used. In the present embodiment, the acid
scavenger may be used solely, or may be used in combination of two
or more thereof. The content thereof is typically 0.005 to 5 mass
%, and preferably 0.05 to 3 mass %, based on the total amount of
the lubricating oil composition, from the standpoints of effects
and inhibition of sludge generation. The lubricating oil
composition may be improved in stability by containing the acid
scavenger.
[0131] Examples of the oxygen scavenger include a sulfur-containing
aromatic compound, such as 4,4'-thiobis(3-methyl-6-t-butylphenol),
diphenyl sulfide, dioctyldiphenyl sulfide, a dialkyldiphenylene
sulfide, benzothiophene, dibenzothiophene, phenothiazine,
benzothiapyrane, thiapyrane, thianthrene, dibenzothiapyrane,
diphenylene disulfide, etc., an aliphatic unsaturated compound,
such as various olefins, dienes, and trienes, etc.; a terpene
compound having a double bond; and the like.
[0132] Examples of the extreme pressure agent may include a
phosphorus-based extreme pressure agent, such as a phosphate ester,
an acidic phosphate ester, a phosphite ester, an acidic phosphite
ester, and an amine salt thereof, etc.
[0133] As such a phosphorus-based extreme pressure agent, tricresyl
phosphate, trithiophenyl phosphate, tri(nonylphenyl) phosphite,
dioleyl hydrogenphosphite, 2-ethylhexykliphenyl phosphite, and the
like are exemplified from the standpoint of the extreme pressure
property, the frictional characteristics, and the like.
[0134] In addition, examples of the extreme pressure agent include
a metal salt of a carboxylic acid. The metal salt of a carboxylic
acid as referred to herein is preferably a metal salt of a
carboxylic acid having 3 to 60 carbon atoms, and more preferably a
metal salt of a fatty acid having 3 to 30 carbon atoms, and
especially preferably 12 to 30 carbon atoms. In addition, examples
thereof may include a metal salt of a dimer acid or a trimer acid
of the aforementioned fatty acid, and a dicarboxylic acid having 3
to 30 carbon atoms. Of those, a metal salt of a fatty acid having
12 to 30 carbon atoms and a dicarboxylic acid having 3 to 30 carbon
atoms is especially preferred.
[0135] Meanwhile, the metal constituting the metal salt is
preferably an alkali metal or an alkaline earth metal, and in
particular, an alkali metal is optimum.
[0136] In addition, examples of the extreme pressure agent other
than those as mentioned above may include a sulfur-based extreme
pressure agent, such as sulfurized fats and oils, a sulfurized
fatty acid, a sulfurized ester, a sulfurized olefin, a
dihydrocarbyl polysulfide, a thiocarbamate compound, a thioterpene
compound, a dialkyl thiodipropionate compound, etc.
[0137] The content of the extreme pressure agent is typically 0.001
to 5 mass %, and especially preferably 0.005 to 3 mass % on the
basis of the whole amount of the lubricating oil composition from
the standpoints of lubricating properties and stability.
[0138] The extreme pressure agent may be used solely, or may be
used in combination of two or more thereof.
[0139] Examples of the oiliness agent include an aliphatic
saturated or unsaturated monocarboxylic acid, such as stearic acid,
oleic acid, etc.; a polymerized fatty acid, such as a dimer acid, a
hydrogenated dimer acid, etc.; a hydroxy fatty acid, such as
ricinoleic acid, 12-hydroxystearic acid, etc.; an aliphatic
saturated or unsaturated monoalcohol, such as lauryl alcohol, oleyl
alcohol, etc.; an aliphatic saturated or unsaturated monoamine,
such as stearylamine, oleylamine, etc.; an aliphatic saturated or
unsaturated monocarboxylic acid amide, such as lauric acid amide,
oleic acid amide, etc.; a partial ester of a polyhydric alcohol,
such as glycerin, sorbitol, etc., and an aliphatic saturated or
unsaturated monocarboxylic acid; and the like.
[0140] Such an oiliness agent may be used solely, or may be used in
combination of two or more thereof. The content thereof is chosen
within the range of typically from 0.01 to 10 mass %, and
preferably from 0.1 to 5 mass %, on the basis of the whole amount
of the lubricating oil composition.
[0141] Examples of the copper deactivator may include an
N--[N,N'-dialkyl(alkyl group having 3 to 12 carbon
atoms)aminomethyl]triazole, and the like.
[0142] Examples of the defoaming agent may include a silicone oil,
a fluorinated silicone oil, and the like. The content of the
defoaming agent is typically 0.005 to 2 mass %, and preferably 0.01
to 1 mass %, relative to the whole amount of the lubricating oil
composition.
[0143] Examples of the rust preventive may include a metal
sulfonate, an aliphatic amine compound, an organic phosphite ester,
an organic phosphate ester, an organic sulfonic acid metal salt, an
organic phosphoric acid metal salt, an alkenyl succinate ester, a
polyhydric alcohol ester, and the like.
[0144] The lubricating oil composition according to the present
embodiment may further contain various other known additives within
the range where the object of the present invention is not
impaired.
[0145] The lubricating oil composition according to the present
embodiment can be used as a hydraulic oil, a turbine oil, a
compressor oil, a bearing gear oil, an engine oil, a refrigerator
oil, and the like, and among these, is preferably used as a
refrigerator oil.
[0146] The lubricating oil composition used as a refrigerator oil
is used under a refrigerant environment, and specifically used by
filling in a refrigerator along with a refrigerant. The
refrigerator as referred to herein has a refrigeration cycle
constituted of a compressor, a condenser, an expansion mechanism
(e.g., an expansion valve, etc.), and an evaporator as the
essential components, or constituted of a compressor, a condenser,
an expansion mechanism, a dryer, and an evaporator as essential
components. The lubricating oil composition is used, for example,
for lubricating a sliding portion provided in a compressor,
etc.
[0147] More specifically, the lubricating oil composition used as a
refrigerator oil can be used for, for example, various refrigerator
systems, hot water systems, and heating systems, such as various
car air conditioners, e.g., an open type car air-conditioner and an
electric car air-conditioner, a gas heat pump (GHP), an air
conditioner, a fridge, an automatic vending machine, a showcase, a
hot water supply machine, a floor heater, and the like.
[Method for Producing Lubricating Oil Composition]
[0148] The method for producing a lubricating oil composition
according to the present embodiment includes: blending a viscosity
index improver with an oxygen-containing synthetic base oil, so as
to provide a lubricating oil composition. In the production method,
various additives may be blended with the oxygen-containing
synthetic base oil in addition to the viscosity index improver. The
details of the oxygen-containing synthetic base oil, the viscosity
index improver, and the additives, and the details of the
lubricating oil composition are the same as above, and the detailed
explanations are omitted herein.
EXAMPLES
[0149] The present invention will be described more specifically
with reference to examples below, but the present invention is not
limited to the examples.
[0150] The properties and the evaluation of the lubricating oil
compositions were obtained by the procedures shown below.
(1) Kinetic Viscosity (40.degree. C., 100.degree. C.)
[0151] The kinematic viscosity was measured with a glass capillary
viscometer according to JIS K2283.
(2) Number Average Molecular Weight (Mn) and Weight Average
Molecular Weight (Mw)
[0152] The number average molecular weight (Mn) and the weight
average molecular weight (Mw) were measured with gel permeation
chromatography (GPC). In the GPC, the measurement was performed by
using two columns of Shodex KF-402HQ and chloroform as an eluent
with an RI detector, and the number average molecular weight (Mn)
and the weight average molecular weight (Mw) were obtained with the
standard polystyrene.
(3) Storage Stability Test
[0153] 100 mL of the lubricating oil composition was stirred with a
magnetic stirrer at 60.degree. C. for 30 minutes, and after
allowing to stand at room temperature (23.degree. C.) for 1 day, it
was visually observed whether or not the viscosity index improver
was dissolved in the base oil.
(4) Pour Point
[0154] The pour point was measured according to JIS K2269.
Examples 1 to 14 and Comparative Examples 1 to 7
[0155] The base oils shown in Table 1 and the viscosity index
improvers shown in Table 2 were blended in the blending amounts
shown in Table 3, so as to provide lubricating oil compositions of
Examples and Comparative Examples. The properties and the results
of the evaluation tests of the lubricating oil compositions of
Examples and Comparative Examples are shown in Table 3.
TABLE-US-00001 TABLE 1 40.degree. C. Kinetic 100.degree. C. Kinetic
viscosity viscosity Oxygen Number average Weight average Base oil
(mm.sup.2/s) (mm.sup.2/s) content molecular weight molecular weight
A1 Polyoxypropylene glycol dimethyl ether 3.72 1.5 28% 250 270 A2
Polyoxypropylene glycol dimethyl ether 46.1 10 28% 1,200 1,300 A3
Polyoxypropylene glycol monobutyl ether 125 20 28% 2,800 3,000 A4
Polyoxyethylene glycol polyoxypropylene 12.2 3.5 32% 550 600 glycol
dimethyl ether A5 Polyisobutyl vinyl ether 11.1 2.7 16% 300 350 A6
Polyethyl vinyl ether 41.5 6.3 22% 650 710 A7 Pentaerythritol
tetra-2-ethylhexyl ester 39.5 6.1 20% 640 700 A8 Paraffin mineral
oil 42.3 6.5 0 580 630 A9 Alkylbenzene 25.4 3.8 0 430 470 * The
molar ratio of the oxypropylene unit and the oxyethylene unit in A4
was 5:5. * The number average molecular weight of A7 shows the
molecular weight calculated from the chemical formula (formula
weight).
TABLE-US-00002 TABLE 2 40.degree. C. Kinetic 100.degree. C. Kinetic
viscosity viscosity Oxygen Number average Weight average Viscosity
index improver (mm.sup.2/s) (mm.sup.2/s) content molecular weight
molecular weight B1 Polyoxypropylene glycol diol 45,000 11,000 28%
150,000 345,000 (hydroxyl groups at both ends) B2 Polyoxypropylene
glycol monobutyl ether 100,000< 36,000 28% 460,000 1,932,000 B3
Polyoxyethylene glycol polyoxypropylene 100,000< 23,000 32%
300,000 1,110,000 glycol diol (hydroxyl groups at both ends) B4
Polyoxybutylene glycol monobutyl ether 87,000 18,000 22% 210,000
546,000 B5 Polyethyl vinyl ether 100,000< 35,000 22% 320,000
1,280,000 B6 PMA (polymethacrylate, polymer of alkyl 100,000<
33,000 13% 470,000 2,162,000 methacrylate, alkyl group:
C.sub.12H.sub.25) B7 OCP (olefin copolymer) 100,000< 27,000 0
200,000 560,000 B8 PIB (polyisobutylene) 100,000< 19,000 0
250,000 750,000 B9 SDC (hydride of styrene-isoprene block polymer)
100,000< 37,000 0 280,000 980,000 * The molar ratio of the
oxypropylene unit and the oxyethylene unit in B3 was 5:5.
TABLE-US-00003 TABLE 3 Example 1 2 3 4 5 6 7 8 9 10 11 Base oil A1
95 A2 95 95 95 95 95 A3 95 A4 95 A5 95 A6 95 A7 95 A8 A9 Viscosity
B1 5 5 5 5 5 5 5 index B2 5 improver B3 5 B4 5 B5 5 B6 B7 B8 B9
Oxygen content ratio (A/B) 1.0 1.0 1.0 1.3 0.6 0.8 0.8 1.0 0.7 1.2
1.2 100.degree. C. Kinetic viscosity (mm.sup.2/s) 1.7 12 24 4.1 3.2
7.1 7.3 12 12 12 12 Storage stability dis- dis- dis- dis- dis- dis-
dis- dis- dis- dis- dis- solved solved solved solved solved solved
solved solved solved solved solved Pour point (.degree. C.) -50>
-45 -40 -50> -50> -50> -50> -45 -45 -45 -45 Example
Comparative Example 12 13 14 1 2 3 4 5 6 7 Base oil A1 A2 99.5 90
80 95 95 95 95 70 A3 A4 A5 A6 A7 A8 95 A9 95 Viscosity B1 5 5 index
B2 improver B3 0.5 10 20 30 B4 B5 B6 5 B7 5 B8 5 B9 5 Oxygen
content ratio (A/B) 1.0 1.0 1.0 0.0 0.0 2.2 1.0 100.degree. C.
Kinetic viscosity (mm.sup.2/s) 10 15 23.6 7.3 3.5 12 12 12 12 38
Storage stability dis- dis- dis- sepa- sepa- sepa- sepa- sepa-
sepa- dis- solved solved solved rated rated rated rated rated rated
solved Pour point (.degree. C.) -50> -45 -40 -- -- -- -- -- --
-15 * In Table 3, "-50>" shows that the pour point is lower than
-50.degree. C.
[0156] As shown by Examples, even though a viscosity index improver
having a large molecular weight and thus having a large effect of
improving a viscosity index was used, a good low-temperature
fluidity could be obtained, and the viscosity index improver was
hard to be separated from the base oil, by making the oxygen
contents (A) and (B) and the ratio (A/B) within the prescribed
ranges. In Comparative Examples 1, 2, and 4 to 6, on the other
hand, since a base oil or a viscosity index improver containing no
oxygen was used, the base oil and the viscosity improver were
separated from each other to fail to exhibit a sufficient effect of
improving a viscosity index. Similarly, in Comparative Example 3,
since the viscosity index improver had a low oxygen content and the
ratio (A/B) exceeded 2, the base oil and the viscosity improver
were separated from each other to fail to exhibit a sufficient
effect of improving a viscosity index. In Comparative Example 7,
furthermore, since the viscosity index improver was blended in a
large amount outside the mass ratio of from 99.5:0.5 to 75:25, the
pour point was increased and the low-temperature fluidity could not
be improved.
* * * * *