U.S. patent application number 15/128407 was filed with the patent office on 2018-06-21 for lubricating oil composition for gas engines.
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 Hirotaka YAMASAKI.
Application Number | 20180171259 15/128407 |
Document ID | / |
Family ID | 54240101 |
Filed Date | 2018-06-21 |
United States Patent
Application |
20180171259 |
Kind Code |
A1 |
YAMASAKI; Hirotaka |
June 21, 2018 |
LUBRICATING OIL COMPOSITION FOR GAS ENGINES
Abstract
The lubricating oil composition for gas engine of the present
invention contains (A) a base oil, (B1) an overbased calcium
salicylate, (B2) an overbased sodium sulfonate, (C1) an amine-based
antioxidant, and (C2) a phenol-based antioxidant, a total content
of the amine-based antioxidant (C1) and the phenol-based
antioxidant (C2) being 4 mass % or more on a basis of the whole
amount of the composition.
Inventors: |
YAMASAKI; Hirotaka;
(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: |
54240101 |
Appl. No.: |
15/128407 |
Filed: |
March 13, 2015 |
PCT Filed: |
March 13, 2015 |
PCT NO: |
PCT/JP2015/057579 |
371 Date: |
September 22, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 125/22 20130101;
C10M 2215/221 20130101; C10M 2215/28 20130101; C10M 2207/026
20130101; C10M 2227/09 20130101; C10M 2215/064 20130101; C10M
2219/082 20130101; C10M 2223/045 20130101; C10N 2010/02 20130101;
C10N 2010/04 20130101; C10N 2030/10 20130101; C10N 2030/52
20200501; C10M 2207/289 20130101; C10M 2215/065 20130101; C10N
2030/08 20130101; C10N 2010/12 20130101; C10M 133/40 20130101; C10M
167/00 20130101; C10M 2209/084 20130101; C10N 2030/02 20130101;
C10M 2227/066 20130101; C10N 2030/40 20200501; C10M 2203/1025
20130101; C10M 2207/262 20130101; C10M 163/00 20130101; C10M
2219/046 20130101; C10N 2040/255 20200501; C10N 2020/02 20130101;
C10M 2203/1025 20130101; C10N 2020/02 20130101; C10M 2227/09
20130101; C10N 2010/12 20130101; C10M 2209/084 20130101; C10N
2020/02 20130101; C10M 2215/28 20130101; C10N 2060/14 20130101;
C10M 2223/045 20130101; C10N 2010/04 20130101; C10M 2227/09
20130101; C10N 2010/12 20130101; C10M 2203/1025 20130101; C10N
2020/02 20130101; C10M 2209/084 20130101; C10N 2020/02 20130101;
C10M 2223/045 20130101; C10N 2010/04 20130101; C10M 2215/28
20130101; C10N 2060/14 20130101 |
International
Class: |
C10M 167/00 20060101
C10M167/00; C10M 163/00 20060101 C10M163/00; C10M 133/40 20060101
C10M133/40; C10M 125/22 20060101 C10M125/22 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2014 |
JP |
2014-073485 |
Claims
1: A lubricating oil composition for gas engine, comprising (A) a
base oil, (B1) an overbased calcium salicylate, (B2) an overbased
sodium sulfonate, (C1) an amine-based antioxidant, and (C2) a
phenol-based antioxidant, a total content of the amine-based
antioxidant (C1) and the phenol-based antioxidant (C2) being 4 mass
% or more on a basis of the whole amount of the composition.
2: The lubricating oil composition for gas engine according to
claim 1, further comprising (D) a heterocyclic compound selected
from the group consisting of at least one a compound represented by
the following general formula (I) and at least one compound
represented by the following general formula (II): ##STR00006##
wherein R.sup.1 represents a linear or branched alkyl group having
7 to 17 carbon atoms; and n represents 6 to 18.
3: The lubricating oil composition for gas engine according to
claim 1, further comprising (C3) a molybdenum-based
antioxidant.
4: The lubricating oil composition for gas engine according to
claim 1, wherein the total content of the amine-based antioxidant
(C1) and the phenol-based antioxidant (C2) is 5 mass % or more on a
basis of the whole amount of the composition.
5: The lubricating oil composition for gas engine according to
claim 1, further comprising (B3) a basic calcium sulfonate.
6: The lubricating oil composition for gas engine according to
claim 1, further comprising (E1) a polymethacrylate as (E) a
viscosity index improver.
7: The lubricating oil composition for gas engine according to
claim 1, wherein a calcium content is 0.05 to 0.4 mass %, and a
sodium content is 0.005 to 0.1 mass % on a basis of the whole
amount of the composition.
8: The lubricating oil composition for gas engine according to
claim 1 that is suitable for use in a gas heat pump.
9: A method for producing a lubricating oil composition for gas
engine, comprising blending (B1) an overbased calcium salicylate,
(B2) an overbased sodium sulfonate, (C1) an amine-based
antioxidant, and (C2) a phenol-based antioxidant in (A) a base oil
to produce a lubricating oil composition for gas engine, a total
blending amount of the amine-based antioxidant (C1) and the
phenol-based antioxidant (C2) being 4 mass % or more on a basis of
the whole amount of the composition.
10: A composition comprising a base oil, an overbased calcium
salicylate, an overbased sodium sulfonate, an amine-based
antioxidant, and a phenol-based antioxidant, a total content of the
amine-based antioxidant and the phenol-based antioxidant being 4
mass % or more based on the total mass of the composition.
11: A gas engine comprising the composition of claim 10.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricating oil
composition for gas engine, particularly an engine oil to be used
for gas heat pumps.
BACKGROUND ART
[0002] For air conditioning of buildings and constructions, a gas
engine heat pump system and a cogeneration system are put to
practical use. In such a system, gas engines utilizing a fuel, such
as natural gas, liquefied petroleum gas (LPG), etc., are generally
used. In these systems, a maintenance and inspection work is
burdensome, and therefore, improvements of the maintenance, such as
simplification of inspection, prolongation of maintenance work
interval, etc., are an important issue.
[0003] Conventionally, in a variety of engine oils, it is general
to extend the lifetime by mainly employing a calcium-based
detergent or a magnesium-based detergent as a metal detergent and
subjecting an antioxidant to optimization or the like, thereby
enabling an initial base number to be increased and the base number
to be maintained over a long period of time. However, in the metal
detergent, it is difficult to increase its quantity due to a
restriction of sulfated ash, or the like, and according to the
action of the antioxidant alone, it is difficult to increase the
base number or drastically improve the base number retention.
Furthermore, in gas engines, the combustion temperature is high,
and nitrogen oxides are liable to be generated. Thus, the gas
engine oil is liable to cause NOx-degradation or high-temperature
oxidation degradation, and the base number tends to decrease. For
that reason, even if it is contemplated to extend the lifetime of a
gas engine oil by a general technique applied to engine oils, it is
difficult to make oil change unnecessary over a long period of
time.
[0004] In addition, as the metal detergent, besides the
calcium-based detergent and the magnesium-based detergent, a sodium
sulfonate is also known (see, for example, PTLs 1 to 3).
CITATION LIST
Patent Literature
[0005] PTL 1: JP 6-33083 A
[0006] PTL 2: JP 5-194978 A
[0007] PTL 3: JP 5-508181 A
SUMMARY OF INVENTION
Technical Problem
[0008] However, since the sodium sulfonate is low in water
resistance, its use for automotive engine oils might be avoided.
Actually, the sodium sulfonate is not practically used for gas
engine oils.
[0009] In addition, conventionally, a replacement cycle of gas
engine oils was 4,000 hours to 10,000 hours. In recent years,
long-drain properties such that the oil change is unnecessary for a
period of time of two times or more of the aforementioned
replacement cycle are desired.
[0010] In view of the foregoing circumstances, the present
invention has been made. A problem of the present invention is to
increase an initial base number even without increasing the
quantity of a metal and also to suppress the degradation by NOx,
thereby maintaining the base number even under contact with NOx
over a long period of time at a fixed level or more to extend the
lifetime of a gas engine oil.
Solution to Problem
[0011] In order to solve the foregoing problem, the present
inventor made extensive and intensive investigations. As a result,
it has been found that the problem can be solved by not only
blending, as a metal detergent, an overbased sodium sulfonate in
addition to an overbased calcium salicylate but also blending both
a phenol-based antioxidant and an amine-based antioxidant such that
a total content thereof becomes large, in a lubricating oil
composition for gas engine, leading to accomplishment of the
present invention.
[0012] Specifically, the present invention provides the following
(1) to (10).
(1) A lubricating oil composition for gas engine, containing (A) a
base oil, (B1) an overbased calcium salicylate, (B2) an overbased
sodium sulfonate, (C1) an amine-based antioxidant, and (C2) a
phenol-based antioxidant, a total content of the amine-based
antioxidant (C1) and the phenol-based antioxidant (C2) being 4 mass
% or more on a basis of the whole amount of the composition. (2)
The lubricating oil composition for gas engine as set forth above
in (1), further containing (D) a heterocyclic compound selected
from a compound represented by the following general formula (I)
and a compound represented by the following general formula
(II).
##STR00001##
[0013] In the foregoing formulae, R.sup.1 represents a linear or
branched alkyl group having 7 to 17 carbon atoms; and n represents
6 to 18.
(3) The lubricating oil composition for gas engine as set forth
above in (1) or (2), further containing (C3) a molybdenum-based
antioxidant. (4) The lubricating oil composition for gas engine as
set forth above in any of (1) to (3), wherein the total content of
the amine-based antioxidant (C1) and the phenol-based antioxidant
(C2) is 5 mass % or more on a basis of the whole amount of the
composition. (5) The lubricating oil composition for gas engine as
set forth above in any of (1) to (4), further containing (B3) a
basic calcium sulfonate. (6) The lubricating oil composition for
gas engine as set forth above in any of (1) to (5), further
containing (E1) a polymethacrylate as (E) a viscosity index
improver. (7) The lubricating oil composition for gas engine as set
forth above in any of (1) to (6), wherein a calcium content is 0.05
to 0.4 mass %, and a sodium content is 0.005 to 0.1 mass % on a
basis of the whole amount of the composition. (8) The lubricating
oil composition for gas engine as set forth above in any of (1) to
(7), which is used for gas heat pumps. (9) A method for producing a
lubricating oil composition for gas engine, including blending (B1)
an overbased calcium salicylate, (B2) an overbased sodium
sulfonate, (C1) an amine-based antioxidant, and (C2) a phenol-based
antioxidant in (A) a base oil to produce a lubricating oil
composition for gas engine,
[0014] a total blending amount of the amine-based antioxidant (C1)
and the phenol-based antioxidant (C2) being 4 mass % or more on a
basis of the whole amount of the composition.
(10) A lubricating method for lubricating parts therebetween in a
gas engine with the lubricating oil composition for gas engine as
set forth above in any of (1) to (8).
Advantageous Effects of Invention
[0015] In accordance with the present invention, there is provided
a lubricating oil composition for gas engine capable of increasing
an initial base number even without increasing the quantity of a
metal and also suppressing the degradation by NOx, thereby
maintaining the base number even under contact with NOx over a long
period of time at a fixed level or more.
DESCRIPTION OF EMBODIMENTS
[0016] Embodiments of the present invention are hereunder described
in detail.
[0017] The lubricating oil composition for gas engine (hereinafter
may be referred to simply as "lubricating oil composition") of the
present invention contains (A) a base oil; (B1) an overbased
calcium salicylate and (B2) an overbased sodium sulfonate as (B) a
metal detergent; and (C1) an amine-based antioxidant and (C2) a
phenol-based antioxidant as (C) an antioxidant.
[(A) Base Oil]
[0018] The base oil (A) that is used in the present invention is
not particularly limited, and an arbitrary mineral oil or synthetic
oil conventionally used as a base oil of lubricating oil can be
appropriately selected and used.
[0019] Examples of the mineral oil include a mineral oil refined by
subjecting a lubricating oil distillate that is obtained by
distilling under reduced pressure an atmospheric residue given by
atmospheric distillation of crude oil, to one or more treatments of
solvent deasphalting, solvent extraction, hydro-cracking, solvent
dewaxing, catalytic dewaxing, hydrorefining, and the like; a
mineral oil produced by isomerizing a wax; and the like. Of those,
a mineral oil treated by hydrorefining is preferred. The mineral
oil treated by hydrorefining readily improves a % Cp, a sulfur
content, and a viscosity index as described later.
[0020] Examples of the synthetic oil include polyolefins, such as
polybutene, an .alpha.-olefin homopolymer or copolymer (e.g., an
ethylene-.alpha.-olefin copolymer), etc.; various esters, such as a
polyol ester, a dibasic acid ester, a phosphate ester, etc.;
various ethers, such as a polyphenyl ether, etc.; polyglycols;
alkylbenzenes; alkylnaphthalenes; base oils produced by isomerizing
GTL WAX; and the like. Of those synthetic oils, polyolefins and
polyol esters are especially preferred.
[0021] In the present invention, the mineral oils may be used
singly or in combination of two or more thereof as the base oil. In
addition, the synthetic oils may be used singly or in combination
of two or more thereof as the base oil. Furthermore, one or more
mineral oils and one or more synthetic oils may be used in
combination.
[0022] In addition, the lubricating base oil serves as a main
component in the lubricating oil composition and is contained in an
amount of typically 50 mass % or more, preferably 60 to 97 mass %,
and more preferably 65 to 95 mass % relative to the whole amount of
the lubricating oil composition.
[0023] Although a viscosity of the base oil (A) is not particularly
limited, a kinematic viscosity thereof at 100.degree. C. is
preferably in the range of from 2 to 15 mm.sup.2/s, more preferably
in the range of from 2.5 to 12 mm.sup.2/s, and still more
preferably in the range of from 3 to 6 mm.sup.2/s. In the present
invention, by regulating the kinematic viscosity of the base oil
(A) to a relatively low viscosity as described above, the viscosity
of the lubricating oil composition may also be made low, and fuel
consumption-saving properties are readily realized. In the present
specification, the kinematic viscosity is one measured by the
method described in the Examples as described later.
[0024] The base oil (A) has a % Cp as measured by ring analysis of
preferably 70% or more, and more preferably 80% or more. A sulfur
content in the base oil is preferably 300 ppm by mass or less, more
preferably 100 ppm by mass or less, and especially preferably 20
ppm by mass or less. The term "% Cp as measured by ring analysis"
refers to a proportion (percentage) of paraffin components as
calculated by the ring analysis n-d-M method and is measured in
conformity with ASTM D-3238. The sulfur content is measured in
conformity with JIS K 2541.
[0025] In the present invention, as described above, by making the
proportion of the paraffin components high and the sulfur content
low, the high-temperature oxidation stability of the lubricating
oil composition is enhanced, and the oxidation degradation under
contact with NOx is readily prevented from occurring.
[0026] A viscosity index of the base oil is preferably 100 or more,
more preferably 120 or more, and especially preferably 125 or more.
When the viscosity index is made high as 100 or more, a change in
viscosity of the lubricating base oil with a change in temperature
becomes small. In the present specification, the viscosity index is
one measured by the method described in the Examples as described
later.
[(B) Metal Detergent]
[0027] The lubricating oil composition of the present invention
contains at least (B1) an overbased calcium salicylate and (B2) an
overbased sodium sulfonate as (B) a metal detergent.
[0028] Although the overbased calcium salicylate (B1) may make the
detergency relatively good, when it is used singly, the base number
of a new oil may not be thoroughly enhanced without increasing the
quantity of a metal. Furthermore, in the case where the composition
is, for example, used under a high-temperature environment upon
contact with NOx, the decrease of the base number may not be
thoroughly suppressed. In addition, when the overbased calcium
salicylate (B1) is used singly, the increase in viscosity is liable
to be caused due to NOx-degradation, and it is difficult to realize
the desired fuel consumption-saving properties.
[0029] Meanwhile, in the present invention, when in addition to the
component (B1), the overbased sodium sulfonate (B2) is combined and
used, the base number of the new oil can be increased without
increasing the quantity of a metal in the lubricating oil
composition, and even when used under a high-temperature
environment upon contact with NOx, the decrease of the base number
can be suppressed. In addition, the increase in viscosity to be
caused due to NOx-degradation can be suppressed, and the fuel
consumption-saving properties are readily realized.
[0030] A total base number (TBN) of the overbased calcium
salicylate (B1) is preferably 100 to 400 mgKOH/g. By regulating the
TBN to such a range, the formation of a precipitate can be
suppressed while making the detergency good. Furthermore, the
initial base number is readily relatively increased, and the
decrease of the base number to be caused due to NOx-degradation or
the like can be appropriately inhibited. From these viewpoints, the
TBN of the overbased calcium salicylate (B1) is more preferably 150
to 300 mgKOH/g. The TBN refers to a total base number as measured
by perchloric acid method in conformity with JIS K2501.
[0031] Specific examples of the overbased calcium salicylate that
is the component (B1) include those obtained by overbasing a
calcium salt of an alkyl salicylic acid, such as a monoalkyl
salicylic acid, a dialkyl salicylic acid, etc. The alkyl group
constituting the alkylsalicylic acid is a linear or branched alkyl
group having typically about 1 to 100 carbon atoms, preferably
about 4 to 30 carbon atoms, and more preferably about 6 to 20
carbon atoms.
[0032] A TBN of the overbased sodium sulfonate (B2) is typically
higher than the TBN of the overbased calcium salicylate (B1), and
it is preferably 300 to 600 mgKOH/g. By regulating the TBN to such
a range, the base number of a new oil can be enhanced with a
relatively small amount of the component (B2) without forming a
precipitate or the like. In addition, the decrease of the base
number or the increase in viscosity to be caused due to
NOx-degradation or high-temperature oxidation degradation is
readily inhibited. From these viewpoints, the TBN of the overbased
sodium sulfonate (B2) is more preferably 350 to 550 mgKOH/g.
[0033] The lubricating oil composition may further contain (B3) a
basic calcium sulfonate as the metal detergent (B). A TBN of the
basic calcium sulfonate that is used as the component (B3) is
preferably 100 mgKOH/g or less, more preferably 5 to 80 mg/g, and
still more preferably 10 to 70 mgKOH/g. By containing the basic
calcium sulfonate (B3), the detergency of the lubricating oil
composition can be made good.
[0034] As the overbased sodium sulfonate (B2), those obtained by
overbasing a sodium salt of a sulfonic acid of every kind may be
used. As the basic calcium sulfonate (B3), those obtained by
basifying a calcium salt of a sulfonic acid of every kind may be
used. Examples of the sulfonic acid that is used in each of the
overbased sodium sulfonate (B2) and the basic calcium sulfonate
(B3) include aromatic petroleum sulfonic acids, alkyl sulfonic
acids, aryl sulfonic acids, alkylaryl sulfonic acids, and the like.
Specific examples thereof may include dodecylbenzenesulfonic acid,
dilaurylcetylbenzenesulfonic acid, paraffin wax-substituted
benzenesulfonic acid, polyolefin-substituted benzenesulfonic acid,
polyisobutylene-substituted benzenesulfonic acid,
naphthalenesulfonic acid, and the like.
[0035] The overbased calcium salicylate (B1) is contained in an
amount of preferably 0.5 to 8.0 mass %, and more preferably 1.0 to
6.0 mass % on a basis of the whole amount of the composition. When
the overbased calcium salicylate (B1) is contained in an amount of
0.5 mass % or more, the function as the detergent is exhibited, and
furthermore, when used in combination with the component (B2), the
decrease of the base number or the increase in viscosity, which is
caused due to the use, is readily suppressed while making the
initial base number high. When the amount of the component (B1) is
controlled to 8.0 mass % or less, the function corresponding to the
addition amount is exhibited.
[0036] A content of the overbased sodium sulfonate (B2) may be
smaller than the content of the component (B1), and it is
preferably 0.05 to 2.0 mass %, and more preferably 0.10 to 0.80
mass % on a basis of the whole amount of the composition. When the
component (B2) is contained in an amount of 0.05 mass % or more and
used in combination with the component (B1), the initial base
number is readily made high, and the decrease of the base number or
the increase in viscosity is readily suppressed. When the amount of
the component (B2) is controlled to 2.0 mass % or less, the
function corresponding to the addition amount can be exhibited.
[0037] In addition, in the case where the basic calcium sulfonate
(B3) is contained in the lubricating oil composition, its content
is preferably 0.5 to 5.0 mass %, and more preferably 0.7 to 2.5
mass % on a basis of the whole amount of the composition. When the
component (B3) is contained in an amount of 0.5 mass % or more, the
function as the metal detergent can be exhibited, and the
detergency of the lubricating oil composition can be made good.
When the amount of the component (B3) is controlled to 5.0 mass %
or less, the function corresponding to the addition amount can be
exhibited.
[0038] A calcium content of the lubricating oil composition is
preferably 0.05 to 0.4 mass %, more preferably 0.08 to 0.38 mass %,
and still more preferably 0.25 to 0.35 mass % on a basis of the
whole amount of the composition by incorporating the component (B1)
or the components (B1) and (B3) as described above.
[0039] A sodium content of the lubricating oil composition is
preferably 0.005 to 0.1 mass %, more preferably 0.015 to 0.1 mass
%, and still more preferably 0.02 to 0.09 mass % on a basis of the
whole amount of the composition, by incorporating the overbased
sodium sulfonate as the component (B2). In the light of the above,
according to the present invention, the NOx-degradation or
high-temperature oxidation degradation can be inhibited while
controlling each of the calcium and sodium contents to a relatively
low value.
[0040] A ratio (Ca/Na ratio) of the calcium content to the sodium
content is preferably 2 to 20, more preferably 3 to 15, and still
more preferably 5 to 10. When the Ca/Na ratio is allowed to fall
within such a range, by using appropriate amounts of the components
(B1) and (B2), the decrease of the base number and the increase in
viscosity, each of which is caused due to the use, are readily
suppressed while making the initial base number good.
[(C) Antioxidant]
[0041] The lubricating oil composition of the present invention
contains (C1) an amine-based antioxidant and (C2) a phenol-based
antioxidant as (C) an antioxidant. In view of the fact that the
lubricating oil composition of the present invention contains, in
addition to the aforementioned component (B), these two components
as the antioxidant, the oxidation stability is increased, and even
when used under a high-temperature environment upon contact with
NOx, the decrease of the base number or the increase in viscosity
can be suppressed, and the extension of lifetime and the saving of
fuel consumption can be realized.
[0042] In the present invention, a total content of these
amine-based antioxidant (C1) and phenol-based antioxidant (C2) is 4
mass % or more relative to the whole amount of the lubricating oil
composition. When the aforementioned total content is less than 4
mass %, in the case of being used at a high temperature upon
contact with NOx, the oxidation degradation is liable to be caused,
whereby the high base number might be hardly maintained and the
increase in viscosity might be caused, and therefore, the fuel
consumption-saving properties or extension of lifetime would be
hardly realized. In order to maintain the high base number over a
longer period of time and realize fuel consumption-saving
properties and extension of lifetime, the total content of the
amine-based antioxidant (C1) and the phenol-based antioxidant (C2)
is preferably 5 mass % or more.
[0043] The total content of the amine-based antioxidant (C1) and
the phenol-based antioxidant (C2) is preferably 10 mass % or less,
and more preferably 8 mass % or less relative to the whole amount
of the lubricating oil composition in order to exhibit the
performance corresponding to the blending amount, although it is
not particularly limited to these.
[0044] In addition, though a mass ratio (C2/C1) of the phenol-based
antioxidant (C2) to the amine-based antioxidant (C1) is not
particularly limited, it is preferably about 1/3 to 3/1, and more
preferably about 1/2 to 2/1. When the lubricating oil composition
contains the both components in amounts to some extent,
respectively, the aforementioned performances are readily
exhibited.
[0045] Examples of the amine-based antioxidant (C1) include
monoalkyldiphenylamines having an alkyl group having about 3 to 10
carbon atoms, such as mono-t-butyldiphenylamine,
monooctyldiphenylamine, monononyldiphenylamine, etc.;
dialkyldiphenylamines, in which each alkyl group has about 3 to 10
carbon atoms, such as 4,4'-dibutyldiphenylamine,
4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine,
4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine,
4,4'-dinonyldiphenylamine, 4-butyl-4'-octyldiphenylamine, etc.;
polyalkyldiphenylamines having 3 or more alkyl groups, in which
each alkyl group has about 1 to 10 carbon atoms, such as
tetrabutyldiphenylamine, tetrahexyldiphenylamine,
tetraoctyldiphenylamine, tetranonyldiphenylamine,
di(2,4-diethylphenyl)amine, di(2-ethyl-4-nonylphenyl)amine, etc.;
phenyl-.alpha.-naphthylamine types as exemplified by
alkyl-substituted phenyl-.alpha.-naphthylamines having at least one
alkyl group having about 1 to 12 carbon atoms, such as
methylphenyl-.alpha.-naphthylamine,
ethylphenyl-.alpha.-naphthylamine,
butylphenyl-.alpha.-naphthylamine,
hexylphenyl-.alpha.-naphthylamine,
heptylphenyl-.alpha.-naphthylamine,
octylphenyl-.alpha.-naphthylamine,
nonylphenyl-.alpha.-naphthylamine,
t-dodecylphenyl-.alpha.-naphthylamine, etc.;
phenyl-.alpha.-naphthylamine; and the like.
[0046] Among those, it is preferred that a
phenyl-.alpha.-naphthylamine type and a dialkyldiphenylamine are
used singly or in combination of two or more thereof as the
amine-based antioxidant. It is more preferred that both a
phenyl-.alpha.-naphthylamine type (particularly
phenyl-.alpha.-naphthylamine) and a dialkyldiphenylamine are used
in combination. By using the both in combination in this way, the
base number or viscosity of the lubricating oil composition is
maintained good over a long period of time, and the lifetime is
readily extended. In addition, in the case of using a
phenyl-.alpha.-naphthylamine type and a dialkyldiphenylamine in
combination, it is preferred that the content of the
dialkyldiphenylamine is higher than the content of the
phenyl-.alpha.-naphthylamine type on a mass basis.
[0047] Examples of the phenol-based antioxidant (C2) include
bisphenol-based antioxidants, such as
4,4'-methylenebis(2,6-di-t-butylphenol),
4,4'-bis(2,6-di-t-butylphenol), 4,4'-bis(2-methyl-6-t-butylphenol),
2,2'-methylenebis(4-ethyl-6-t-butylphenol),
2,2'-methylenebis(4-methyl-6-t-butylphenol),
4,4'-butylidenebis(3-methyl-6-t-butylphenol),
4,4'-isopropylidenebis(2,6-di-t-butylphenol),
2,2'-methylenebis(4-methyl-6-nonylphenol),
2,2'-isobutylidenebis(4,6-dimethylphenol),
2,2'-methylenebis(4-methyl-6-cyclohexylphenol),
4,4'-thiobis(2-methyl-6-t-butylphenol),
4,4'-thiobis(3-methyl-6-t-butylphenol),
2,2'-thiobis(4-methyl-6-t-butylphenol),
bis(3-methyl-4-hydroxy-5-t-butylbenzyl)sulfide,
bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide,
thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],
etc.; and monophenol-based antioxidants, such as
2,6-d-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol,
2,4-dimethyl-6-t-butylphenol, 2,6-di-t-amyl-p-cresol,
n-octyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate,
6-methylheptyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate,
n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, etc.
Among those, it is preferred to use an ester group-containing
phenol.
[0048] In addition, the bisphenol-based antioxidant and the
monophenol-based antioxidant may be used singly, or the both may be
used in combination. From the viewpoint of maintaining the base
number or viscosity of the lubricating oil composition good over a
long period of time, thereby enabling the lifetime to be extended,
it is preferred to use the both in combination. In the case of
using both the bisphenol-based antioxidant and the monophenol-based
antioxidant, it is better that the content of the monophenol-based
antioxidant is higher than the content of the bisphenol-based
antioxidant on a mass basis.
[0049] It is preferred that the lubricating oil composition of the
present invention further contains (C3) a molybdenum-based
antioxidant as the antioxidant (C). In the present invention, when
in addition to the aforementioned components (C1) and (C2), the
molybdenum-based antioxidant (C3) is contained as the antioxidant
(C), the degradation by NOx or high-temperature oxidation
degradation is more prevented from occurring, whereby the decrease
of the base number or the increase in viscosity is more readily
inhibited.
[0050] As the molybdenum-based antioxidant, molybdenum compounds
which have hitherto been known as an antioxidant may be used, and
for example, mononuclear molybdenum compounds may be used.
[0051] More specifically, there is preferably exemplified a
molybdenum/amine complex as the molybdenum-based antioxidant. As
this molybdenum/amine complex, a hexavalent molybdenum compound,
for example, a compound obtained by allowing molybdenum trioxide
and/or molybdic acid to react with an amine compound, for example,
a compound obtained by a production method described in JP
2003-252887 A, may also be used. Although the amine compound with
which the hexavalent molybdenum compound is allowed to react is not
particularly limited, specific examples thereof include a
monoamine, a diamine, a polyamine, and an alkanolamine. More
specifically, examples of the amine compound may include an
alkylamine having an alkyl group having 1 to 30 carbon atoms, such
as methylamine, ethylamine, dimethylamine, diethylamine,
methylethylamine, methylpropylamine, etc. (these alkyl groups may
be either linear or branched); an alkenylamine having an alkenyl
group having 2 to 30 carbon atoms, such as ethenylamine,
propenylamine, butenylamine, octenylamine, oleylamine, etc. (these
alkenyl groups may be either linear or branched); an alkanolamine
having an alkanol group having 1 to 30 carbon atoms, such as
methanolamine, ethanolamine, methanolethanolamine,
methanolpropanolamine, etc. (these alkanol groups may be either
linear or branched); an alkylenediamine having an alkylene group
having 1 to 30 carbon atoms, such as methylenediamine,
ethylenediamine, propylenediamine, butylenediamine, etc.; a
polyamine, such as diethylenetriamine, triethylenetetramine,
tetraethylenepentamine, pentaethylenehexamine, etc.; compounds that
are the aforementioned monoamines, diamines or polyamines into
which alkyl or alkenyl group(s) having 8 to 20 carbon atoms is
further introduced, such as undecyldiethylamine,
undecyldiethanolamine, dodecyldipropanolamine, oleyldiethanolamine,
oleylpropylenediamine, stearyltertraethylenepentamine, etc., a
heterocyclic compound, such as imidazoline etc.; an alkylene oxide
adduct of such a compound; a mixture thereof; and the like.
[0052] In addition, as the molybdenum-based antioxidant, organic
molybdenum compounds including a compound of the following general
formula (III) and/or a compound of the following general formula
(IV) may also be exemplified. A mixture of the compound of the
general formula (III) and the compound of the general formula (IV)
is obtained by allowing a fatty oil, diethanolamine, and a
molybdenum source to react successively with each other through a
condensation method described in, for example, JP 62-108891 A.
##STR00002##
[0053] In the formulae (III) and (IV), R represents a fatty oil
residue, and the fatty oil is a glycerol ester of a higher fatty
acid that contains at least 12 carbon atoms and may contain 22 or
more carbon atoms. Such an ester is generally known as vegetable
and animal oils and fats. Examples of the useful vegetable oils and
fats are derived from coconut, corn, cotton seeds, linseed oil,
peanuts, soybeans, and sunflower kernels. Similarly, animal oils
and fats, such as tallow, etc., may be used.
[0054] The molybdenum source may be an oxygen-containing molybdenum
compound capable of reacting with an intermediate reaction product
of the fatty oil and the diethanolamine to form an ester-type
molybdenum complex. In particular, examples of the molybdenum
source include ammonium molybdate, molybdenum oxide, and a mixture
thereof.
[0055] Furthermore, examples of the molybdenum-based antioxidant
may include a sulfur-containing molybdenum complex of a succinimide
described in JP 3-22438 B and JP 2004-2866 A; and the like.
[0056] The lubricating oil composition of the present invention
contains the molybdenum-based antioxidant (C3) in an amount of
preferably 0.01 to 1 mass %, and more preferably 0.04 to 0.5 mass %
relative to the whole amount of the composition. When the
molybdenum-based antioxidant is contained in an amount of 0.01 mass
% or more, the oxidation degradation or NOx degradation of the
lubricating oil composition can be appropriately prevented from
occurring. In addition, when the molybdenum-based antioxidant is
contained in an amount of 1 mass % or less, the effect
corresponding to the addition amount can be exhibited.
[0057] When the lubricating oil composition contains the
aforementioned molybdenum-based oxidant (C3), the molybdenum
content in the composition is preferably 20 to 800 ppm, more
preferably 40 to 400 ppm, and still more preferably 50 to 200 ppm
on a mass basis.
[0058] In addition, the lubricating oil composition may contain, as
the antioxidant (C), other antioxidants than the aforementioned
components (C1) to (C3), such as a phosphorus-based antioxidant,
etc.
[(D) Heterocyclic Compound]
[0059] It is preferred that the lubricating oil composition of the
present invention further contains (D) a heterocyclic compound
selected from a compound represented by the following general
formula (I) and a compound represented by the following general
formula (II). In the present invention, when the heterocyclic
compound (D) is contained, the base number is readily enhanced
without increasing the metal content in the composition. In
addition, even when the lubricating oil composition is used at a
high temperature upon contact with NOx, the enhanced base number is
readily maintained, and the increase in viscosity is readily
suppressed.
##STR00003##
[0060] In the general formula (I), R.sup.1 represents a linear or
branched alkyl group having 7 to 17 carbon atoms. In the general
formula (II), n represents an integer of 6 to 18. The
aforementioned alkyl group is one composed of, for example, 7, 8,
9, 10, 11, 12, 13, 14, 15, 16, or 17 carbon atoms. n is preferably
6, 8, 10, 12, 14, 16, or 18.
[0061] The heterocyclic compound (D) may be produced by a
well-known method. Examples of the heterocyclic compound (D)
include a 2,2,6,6-tetramethylpiperidino-4-ol ester of an aliphatic
carboxylic acid, or esters of lauric acid or stearic acid. As the
heterocyclic compound (D), a hindered amine represented by the
following formula (I-I) or (II-I) is preferred.
##STR00004##
[0062] In the lubricating oil composition of the present invention,
it is preferred that the heterocyclic compound (D) is contained in
an amount of 0.1 to 8 mass % on a basis of the whole amount of the
composition. When the content of the heterocyclic compound (D) is
0.1 mass % or more, the base number of the lubricating oil
composition is readily improved, and the decrease of the base
number or the increase in viscosity is readily inhibited. In
addition, when the content of the heterocyclic compound (D) is 8
mass % or less, the effect corresponding to the content can be
exhibited. The content of the heterocyclic compound (D) is more
preferably 0.3 to 5 mass %, and still more preferably 0.5 to 3 mass
%.
[(E) Viscosity Index Improver]
[0063] It is preferred that the lubricating oil composition of the
present invention further contains (E) a viscosity index improver.
Examples of the viscosity index improver (E) include (E1) a
polymethacrylate.
[0064] As the polymethacrylate (E1), those which have hitherto been
known as a viscosity index improver can be used. The
polymethacrylate (E1) may be either a dispersion type or a
non-dispersion type.
[0065] A weight average molecular weight of the polymethacrylate
(E1) is typically 10,000 to 1,000,000, preferably 30,000 to
800,000, and more preferably 40,000 to 500,000. When the
polymethacrylate is used as the viscosity index improver (E), the
viscosity properties are improved, whereby the fuel
consumption-saving properties of the lubricating oil composition
are readily improved. In addition, in the present invention, in
view of the fact that the aforementioned components (B) and (C) are
appropriately blended, it becomes possible to prevent a reduction
of detergency by the polymethacrylate (E1) from occurring.
[0066] The weight average molecular weight is a value measured by
GPC using polystyrene as a calibration curve. In detail, the weight
average molecular weight is, for example, measured under the
following conditions.
[0067] Column: Two TSK gel GMH6 columns
[0068] Measurement temperature: 40.degree. C.
[0069] Sample solution: 0.5 mass % THF solution
[0070] Detector: Refractive index detector
[0071] Standard: Polystyrene
[0072] A content of the viscosity index improver (E) in the
lubricating oil composition is preferably 0.1 to 10 mass %, more
preferably 0.5 to 8 mass %, and still more preferably 1.0 to 5 mass
% relative to the whole amount of the composition.
[Ashless Dispersant]
[0073] The lubricating oil composition may further contain an
ashless dispersant. Examples of the ashless dispersant include a
non-boronated imide-based dispersant, a boronated imide-based
dispersant, and a mixture thereof. The non-boronated imide-based
dispersant is typically called an imide-based dispersant. As the
imide-based dispersant, it is suitable to use a
polybutenylsuccinimide. Examples of the polybutenylsuccinimide
include compounds represented by the following general formulae (V)
and (VI).
##STR00005##
[0074] In these general formulae (V) and (VI), PIB represents a
polybutenyl group, and its number average molecular weight is
typically 900 or more and 3,500 or less, and preferably 1,000 or
more and 2,000 or less. When the number average molecular weight is
900 or more, there is no concern that the dispersibility is
inferior, and when it is 3,500 or less, there is no concern that
the storage stability is inferior. In the general formulae (V) and
(VI), n is typically an integer of 1 to 5, and more preferably an
integer of 2 to 4.
[0075] Although a production method of the polybutenylsuccinimide
is not particularly limited, the polybutenylsuccinimide can be
produced by a known method. For example, the polybutenylsuccinimide
can be obtained by allowing a polybutenylsuccinic acid obtained
through a reaction between polybutene and maleic anhydride at
100.degree. C. or higher and 200.degree. C. or lower to react with
a polyamine, such as diethylenetriamine, triethylenetetramine,
tetraethylenepentamine, pentaethylenehexamine, etc.
[0076] As the boronated imide-based dispersant, it is preferred to
use a boronated polybutenylsuccinimide obtained by allowing a boron
compound to act on the non-boronated imide-based dispersant
exemplified by the foregoing general formula (V) or (VI).
[0077] Examples of the boron compound include a boric acid, a boric
acid salt, a boric acid ester, and the like. Examples of the boric
acid include orthoboric acid, metaboric acid, paraboric acid, and
the like. Suitable examples of the boric acid salt include ammonium
salts, such as ammonium borates, for example, ammonium metaborate,
ammonium tetraborate, ammonium pentaborate, ammonium octaborate,
etc., and the like. Suitable examples of the boric acid ester
include esters between a boric acid and an alkyl alcohol (desirably
having 1 to 6 carbon atoms), such as monomethyl borate, dimethyl
borate, trimethyl borate, monoethyl borate, diethyl borate,
triethyl borate, monopropyl borate, dipropyl borate, tripropyl
borate, monobutyl borate, dibutyl borate, tributyl borate, etc.
[0078] A mass ratio B/N of a boron content B to a nitrogen content
N in the boronated polybutenylsuccinimide is typically 0.05 to 3,
and preferably 0.2 to 2.
[0079] Although a content of each of the boronated
succinimide-based dispersant and the non-boronated
succinimide-based dispersant (imide-based dispersant) is not
particularly limited, it is preferably 0.1 to 15 mass %, and more
preferably 0.5 to 8 mass %, respectively relative to the whole
amount of the lubricating oil composition. When the content is 0.1
mass % or more, good detergency and dispersibility are obtained,
and when it is 15 mass % or less, the effects of detergency and
dispersibility corresponding to the content are obtained.
[Anti-Wear Agent]
[0080] The lubricating oil composition may further contain an
anti-wear agent. Examples of the anti-wear agent include
sulfur-containing compounds, such as zinc dithiophosphate, zinc
phosphate, zinc dithiocarbamate, molybdenum dithiocarbamate,
molybdenum dithiophosphate, disulfides, thiocarbonates,
thiocarbamates, etc.; phosphorus-containing compounds, such as
phosphite esters, phosphate esters, phosphonate esters, and amine
salts or metal salts thereof, etc.; sulfur- and
phosphorus-containing compounds, such as thiophosphite esters,
thiophosphate esters, thiophosphonate esters, and amine salts or
metal salts thereof, etc.; and the like. Of those, zinc
dithiophosphate is preferred. More specific examples thereof
include zinc dialkyldithiophosphate, and for example, a zinc
dialkyldithiophosphate having a primary or secondary alkyl group
having 3 to 22 carbon atoms or an alkylaryl group substituted with
an alkyl group having 3 to 18 carbon atoms is used.
[0081] The anti-wear agent is contained in an amount of typically
about 0.1 to 5 mass %, and preferably about 0.3 to 3 mass % on a
basis of the whole amount of the composition.
[Pour-Point Depressant]
[0082] The lubricating oil composition may contain a pour-point
depressant. Examples of the pour-point depressant include an
ethylene-vinyl acetate copolymer, a condensate of a chlorinated
paraffin and naphthalene, a condensate of a chlorinated paraffin
and phenol, a polymethacrylate, a polyalkylstyrene, and the
like.
[0083] The pour-point depressant is contained in an amount of
typically about 0.05 to 3 mass %, and preferably about 0.1 to 1
mass % on a basis of the whole amount of the composition.
[Other Additives]
[0084] The lubricating oil composition may further contain, in
addition to the aforementioned components, one or more additives,
such as a metal deactivator, a demulsifier, an antifoaming agent,
etc.
[0085] Examples of the metal deactivator include a
benzotriazole-based compound, a tolyltriazole-based compound, a
thiadiazole-based compound, an imidazole-based compound, a
pyrimidine-based compound, and the like.
[0086] As the demulsifier, a surfactant is used. Examples thereof
include polyalkylene glycol-based nonionic surfactants, such as a
polyoxyethylene alkyl ether, a polyoxyethylene alkyl phenyl ether,
a polyoxyethylene alkyl naphthyl ether, etc.; and the like.
[0087] Examples of the antifoaming agent include a silicone oil, a
fluorosilicone oil, a fluoroalkyl ether, and the like.
[0088] In order to ensure the fuel consumption-saving properties,
it is preferred that the lubricating oil composition of the present
invention is low in viscosity. Specifically, the viscosity is
preferably less than 16.3 mm.sup.2/s, more preferably 5.6
mm.sup.2/s or more and less than 12.5 mm.sup.2/s, and still more
preferably 6.1 mm.sup.2/s or more and less than 9.3 mm.sup.2/s in
terms of a kinematic viscosity at 100.degree. C. In addition, a
viscosity index of the lubricating oil composition is preferably
130 or more, more preferably 150 or more, and still more preferably
approximately from 170 to 250.
[0089] It is preferred that the lubricating oil composition of the
present invention is a multi-grade oil capable of being used even
at a low temperature while maintaining a lubricating performance at
a high temperature. Specifically, it is preferred that a CCS
viscosity at -35.degree. C. is 6,200 mPas or less, a kinematic
viscosity at 100.degree. C. is 6.1 mm.sup.2/s or more and less than
9.3 mm.sup.2/s, and a high-temperature high-shear viscosity (HTHS
viscosity) at 150.degree. C. is 2.6 mPas or more. Specific examples
of such a lubricating oil composition include those of a 0W-20
grade defined in the Society of Automotive Engineers classification
system SAE (J300).
[0090] The CCS viscosity means a viscosity as measured in
conformity with JIS K2010-1993. The HTHS viscosity at 150.degree.
C. is a viscosity as measured using a TBS viscometer (tapered
bearing simulator viscometer) by the method of ASTM D4683 under
conditions of shear rate: 10.sup.6 sec-1, rotational rate (motor):
3,000 rpm, rotor/stator clearance: 3 .mu.m, and oil temperature:
150.degree. C.
[0091] The lubricating oil composition for gas engine of the
present invention is one used as an engine oil that lubricates
parts therebetween in a gas engine. The gas engine is one to be
used for a gas heat pump, a gas engine cogeneration system, and the
like, and it is preferably used for a gas heat pump.
[Production Method of Lubricating Oil Composition]
[0092] A production method of lubricating oil composition of the
present invention is a method including blending at least the
aforementioned components (B1) and (B2) and components (C1) and
(C2) in the base oil (A) to obtain a lubricating oil composition.
In this production method, one or more components selected from the
component (B) other than the components (B1) and (B2), the
component (C) other than the components (C1) and (C2), the
component (D), the component (E), and other components may be
further blended in the base oil (A). The amounts (blending amounts)
of these respective components are the same as the aforementioned
contents of the respective components, and the properties of the
lubricating oil composition and the details of the respective
components are the same as those described above, and hence, their
descriptions are omitted. In the present production method, the
respective components may be blended in the base oil by any method,
and a technique thereof is not limited.
[0093] The lubricating oil composition that is prepared by blending
the components (B1) and (B2) and the components (C1) and (C2), and
furthermore, optionally one or more components selected from the
component (B) other than the components (B1) and (B2), the
component (C) other than the components (C1) and (C2), the
component (D), the component (E), and other components is generally
one containing these blended materials; however, as the case may
be, at least a part of the blended additives may be converted to
another compound through a reaction or the like.
EXAMPLES
[0094] Next, the present invention is described in more detail with
reference to Examples, but it should be construed that the present
invention is by no means limited by these Examples.
[0095] Various properties were those determined according to the
following procedures.
(1) Kinematic Viscosity
[0096] The kinematic viscosity is a value as measured using a
glass-made capillary viscometer in conformity with JIS
K2283-2000.
(2) Viscosity Index
[0097] The viscosity index is a value as measured in conformity
with JIS K2283.
(3) CCS Viscosity and HTHS Viscosity
[0098] The CCS viscosity and HTHS viscosity are each a value as
measured according to the method described in the
specification.
(4) Base Number
[0099] The base number of the lubricating oil composition was
measured by a hydrochloric acid method in conformity with JIS
K2501-2003.
(5) Calcium, Molybdenum, and Sodium Contents
[0100] The calcium, molybdenum, and sodium contents were measured
in conformity with JPI-5S-38-03.
(6) Nitrogen Content
[0101] The nitrogen content was measured in conformity with JIS
K2609-1998.
[Evaluation Method]
[0102] The lubricating oil composition of each of the Examples and
Comparative Examples was evaluated by the following NOx degradation
test.
[0103] In a flask used for the test of oxidation stability of
internal combustion engine lubricating oils defined in JIS K2514, 6
L/hr of a nitrogen gas containing nitric oxide (NO) in a
concentration of 8,000 mass ppm and 6 L/hr of air were blown into
250 mL of a sample oil (lubricating oil composition) in the
presence of iron and a copper catalyst (a specimen of an oxidation
test of JIS K2514). The base number and the kinematic viscosity at
40.degree. C. were measured, when the oil was subjected to forced
degradation for 144 hours and 240 hours while holding the
temperature of the sample oil at 140.degree. C. A ratio of the base
number after the forced degradation to the base number of a new oil
was calculated as a base number retention rate (%) in terms of a
percentage. In addition, a ratio of the kinematic viscosity at
40.degree. C. of the oil that was subjected to forced degradation
to the kinematic viscosity at 40.degree. C. of the new oil was
calculated as a kinematic viscosity ratio.
Examples 1 to 11 and Comparative Examples 1 to 2
[0104] Lubrication oil compositions of the Examples and Comparative
Examples, were prepared with a formulation shown in Table 1, and
properties of each of the lubrication oil compositions were
measured. In addition, the lubricating oil composition in each of
the Examples and Comparative Examples was evaluated according to
the aforementioned evaluation methods.
TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 Blending of
lubricating oil composition (A) Base oil mass % 77.07 76.07 77.37
78.07 78.17 77.10 78.07 (B1) Metal detergent mass % 3.24 3.24 3.24
3.24 3.24 3.00 3.24 (B2) Metal detergent mass % 0.24 0.24 0.24 0.24
0.24 0.45 0.24 (B3) Metal detergent mass % 2.00 2.00 2.00 2.00 2.00
2.00 2.00 (C1) Amine-based antioxidant 1 mass % 0.20 0.20 0.20 0.20
0.20 0.20 0.20 (C1) Amine-based antioxidant 2 mass % 2.50 2.50 2.50
2.50 2.50 2.50 2.50 (C2) Phenol-based antioxidant 1 mass % 2.00
2.00 2.00 2.00 2.00 2.00 1.00 (C2) Phenol-based antioxidant 2 mass
% 0.50 0.50 0.50 0.50 0.50 0.50 0.50 (C3) Molybdenum-based
antioxidant mass % 0.10 0.10 0.10 0.10 0.10 0.10 (D) Hindered amine
1 mass % 1.00 2.00 1.00 1.00 (D) Hindered amine 2 mass % 0.70 (E)
Viscosity index improver 1 mass % 2.60 2.60 2.60 2.60 2.60 2.60
2.60 (E) Viscosity index improver 2 mass % (E) Viscosity index
improver 3 mass % (E) Viscosity index improver 4 mass % Ashless
dispersant 1 mass % 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Ashless
dispersant 2 mass % 2.50 2.50 2.50 2.50 2.50 2.50 2.50 Ashless
dispersant 3 mass % 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Anti-wear
agent mass % 1.00 1.00 1.00 1.00 1.00 1.00 1.00 Pour-point
depressant mass % 0.20 0.20 0.20 0.20 0.20 0.20 0.20 Others mass %
0.85 0.85 0.85 0.85 0.85 0.85 0.85 Total mass % 100.00 100.00
100.00 100.00 100.00 100.00 100.00 Properties of composition (new
oil) Kinematic viscosity at 40.degree. C. mm.sup.2/s 35.17 35.53
35.22 36.25 35.22 35.98 35.73 Kinematic viscosity at 100.degree. C.
mm.sup.2/s 7.846 8.11 7.859 8.090 7.873 8.037 7.978 Viscosity index
-- 204 213 204 206 205 206 206 CCS viscosity at -35.degree. C. mPa
s 4900 4850 4850 4950 4800 4950 4950 HTHS viscosity at 150.degree.
C. mPa s 2.62 2.70 2.65 2.64 2.60 2.65 2.63 Base number
(hydrochloric acid method) mgKOH/g 11.7 12.7 11.8 11.8 11.5 12.2
11.6 Calcium content mass % 0.30 0.27 0.31 0.31 0.31 0.29 0.31
Molybdenum content ppm 73 66 72 70 2> 71 69 Sodium content mass
% 0.04 0.04 0.04 0.04 0.04 0.08 0.04 Nitrogen content mass % 0.27
0.31 0.27 0.23 0.21 0.19 0.21 Evaluation results NOx degradation
after 144 hours Base number retention rate (HCL) % 38 40 39 32 28
36 30 Kinematic viscosity ratio (40.degree. C.) -- 1.26 1.20 1.20
1.21 1.18 1.19 1.28 NOx degradation after 240 hours Base number
retention rate (HCL) % 17 16 14 14 13 18 8 Kinematic viscosity
ratio (40.degree. C.) -- 1.30 1.28 1.34 1.35 1.39 1.35 1.75 Example
Comparative Example 8 9 10 11 1 2 Blending of lubricating oil
composition (A) Base oil mass % 77.97 79.34 75.92 78.67 77.92 79.07
(B1) Metal detergent mass % 3.24 3.24 3.24 3.24 3.63 3.24 (B2)
Metal detergent mass % 0.24 0.24 0.24 0.24 0.24 (B3) Metal
detergent mass % 2.00 2.00 2.00 2.00 2.00 2.00 (C1) Amine-based
antioxidant 1 mass % 0.20 0.20 0.20 0.20 0.20 0.20 (C1) Amine-based
antioxidant 2 mass % 2.50 2.50 2.50 2.50 2.50 1.50 (C2)
Phenol-based antioxidant 1 mass % 1.00 1.00 1.00 1.00 2.00 1.00
(C2) Phenol-based antioxidant 2 mass % 0.50 0.50 0.50 0.50 0.50
0.50 (C3) Molybdenum-based antioxidant mass % 0.20 0.10 0.10 0.10
0.10 0.10 (D) Hindered amine 1 mass % 1.00 1.00 1.00 1.00 1.00 (D)
Hindered amine 2 mass % (E) Viscosity index improver 1 mass % 2.60
2.60 2.60 (E) Viscosity index improver 2 mass % 1.33 (E) Viscosity
index improver 3 mass % 4.75 (E) Viscosity index improver 4 mass %
2.00 Ashless dispersant 1 mass % 2.00 2.00 2.00 2.00 2.00 2.00
Ashless dispersant 2 mass % 2.50 2.50 2.50 2.50 2.50 2.50 Ashless
dispersant 3 mass % 2.00 2.00 2.00 2.00 2.00 2.00 Anti-wear agent
mass % 1.00 1.00 1.00 1.00 1.00 1.00 Pour-point depressant mass %
0.20 0.20 0.20 0.20 0.20 0.20 Others mass % 0.85 0.85 0.85 0.85
0.85 0.85 Total mass % 100.00 100.00 100.00 100.00 100.00 100.00
Properties of composition (new oil) Kinematic viscosity at
40.degree. C. mm.sup.2/s 35.22 35.49 38.66 32.34 35.22 36.15
Kinematic viscosity at 100.degree. C. mm.sup.2/s 7.872 7.779 7.848
8.183 7.859 8.070 Viscosity index -- 205 199 180 244 204 206 CCS
viscosity at -35.degree. C. mPa s 4800 4750 4900 5000 5450 5550
HTHS viscosity at 150.degree. C. mPa s 2.59 2.58 2.64 2.70 2.58
2.64 Base number (hydrochloric acid method) mgKOH/g 12.0 11.8 11.6
11.5 9.92 11.1 Calcium content mass % 0.31 0.31 0.31 0.31 0.34 0.31
Molybdenum content ppm 139 71 69 73 69 68 Sodium content mass %
0.04 0.04 0.04 0.04 0.01> 0.04 Nitrogen content mass % 0.27 0.27
0.27 0.27 0.22 0.17 Evaluation results NOx degradation after 144
hours Base number retention rate (HCL) % 40 39 38 36 23 18
Kinematic viscosity ratio (40.degree. C.) -- 1.22 1.19 1.28 1.26
1.25 1.31 NOx degradation after 240 hours Base number retention
rate (HCL) % 10 11 10 15 9 4 Kinematic viscosity ratio (40.degree.
C.) -- 1.29 1.25 1.40 1.38 1.65 1.89
[0105] *: The respective components in Table 1 are shown below.
(A) Base Oil:
[0106] Group III (API classification), hydrorefined mineral oil,
kinematic viscosity at 100.degree. C.: 4.1 mm.sup.2/s, viscosity
index: 131, n-d-M ring analysis % Cp: 87.6%, sulfur content: 10
mass ppm or less
(B1) Metal Detergent:
[0107] Overbased calcium salicylate, TBN (perchloric acid method):
225 mgKOH/g, calcium content: 7.8 mass %
(B2) Metal Detergent:
[0108] Overbased sodium sulfonate, TBN (perchloric acid method):
450 mgKOH/g, sodium content: 19.5 mass %
(B3) Metal Detergent:
[0109] Basic calcium sulfonate, TBN (perchloric acid method): 17
mgKOH/g, calcium content: 2.35 mass %
(C1) Amine-Based Antioxidant 1:
[0110] N-Phenyl-1-naphthylamine
(C1) Amine-Based Antioxidant 2:
[0111] Dinonyldiphenylamine (IRGANOX L67, manufactured by BASF
SE)
(C2) Phenol-Based Antioxidant 1:
[0112]
6-Methylheptyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate
(IRGANOX L135, manufactured by BASF SE)
(C2) Phenol-Based Antioxidant 2:
[0113]
Thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate](-
IRGANOX L115, manufactured by BASF SE)
(C3) Molybdenum-Based Antioxidant:
[0114] Trade name: MOLYVAN 855 (manufactured by R.T. Vanderbilt
Company Inc.), a mixture of
[2,2'-(dodecanoylimino)diethanolato]dioxomolybdenum(VI) and
[3-(dodecanoyloxy)-1,2-propanediolato]dioxomolybdenum(VI),
molybdenum content: 7.9 mass %, nitrogen content: 2.8 mass %
(D) Hindered Amine 1:
[0115] Compound represented by the foregoing formula (I-I) (XPDL
590, manufactured by BASF SE)
(D) Hindered Amine 2:
[0116] Compound represented by the foregoing formula (II-I)
(TINUVIN 770, manufactured by BASF SE)
(E) Viscosity Index Improver 1:
[0117] Polymethacrylate, weight average molecular weight:
400,000
(E) Viscosity Index Improver 2:
[0118] Polymethacrylate, weight average molecular weight:
420,000
(E) Viscosity Index Improver 3:
[0119] Polymethacrylate, weight average molecular weight:
45,000
(E) Viscosity Index Improver 4:
[0120] Polymethacrylate, weight average molecular weight:
370,000
Ashless Dispersant 1:
[0121] Polybutenylsuccinimide, nitrogen content: 2.1 mass %
Ashless Dispersant 2:
[0122] Polybutenylsuccinimide, nitrogen content: 1.15 mass %
Ashless Dispersant 3:
[0123] Boron-modified polybutenylsuccinimide, nitrogen content:
1.76 mass %, boron content: 2.0 mass %
Anti-Wear Agent:
[0124] Zinc secondary-dialkyldithiophosphate, phosphorus content:
8.2 mass %, zinc content: 9.0 mass %, sulfur content: 17.1 mass
%
Pour-Point Depressant:
[0125] Acrylic acid copolymer
Others:
[0126] Metal deactivator, antifoaming agent, demulsifier, and other
components
[0127] As is evident from the foregoing Examples, by blending the
components (B1), (B2), (C1), and (C2) and regulating the total
content of the components (C1) and (C2) to 4 mass % or more, the
base number of the new oil could be increased, and even when the
composition was brought into contact with NOx at a high temperature
over a long period of time, the decrease of the base number or the
increase in viscosity could be inhibited. In addition, as is
evident from Examples 1 to 6, by regulating the total content of
the components (C1) and (C2) to 5 mass % or more, the decrease of
the base number or the increase in viscosity could be inhibited
over a longer period of time. In addition, it can be understood
that by blending the component (C3) or the component (D), the
decrease of the base number or the increase in viscosity is readily
inhibited.
[0128] On the other hand, in Comparative Example 1, since the
component (B2) was not blended, even though the amount of the
component (B1) was increased, the base number of the new oil was
not thoroughly increased, and when brought into contact with NOx at
a high temperature, the base number was decreased for a relatively
short time, and the satisfactory performance was not obtained. In
addition, in Comparative Example 2, in view of deceasing the total
content of the components (C1) and (C2), when brought into contact
with NOx at a high temperature, the base number was decreased for a
relatively short time, and the satisfactory performance was not
obtained.
INDUSTRIAL APPLICABILITY
[0129] The lubricating oil composition for gas engine of the
present invention is able to increase an initial base number even
without increasing the quantity of a metal and also to suppress the
degradation by NOx, thereby maintaining the base number even under
contact with NOx over a long period of time at a fixed level or
more, and it is suitably useful for gas engines, such as a gas heat
pump, a gas engine cogeneration system, etc.
* * * * *