LUBRICATING OIL COMPOSITION FOR INTERNAL COMBUSTION
ENGINE
Technical Field
[OOOl] Thepresentinventionrelatestolubricating
o i l c o m p o s i t i o n s f o r i n t e r n a l c o m b u s t i o n e n g i n e s
( h e r e i n a f t e r a l s o r e f e r r e d t o a s " e n g i n e o i l " ) . More
s p e c i f i c a l l y , t h e p r e s e n t i n v e n t i o n r e l a t e s t o an
e n g i n e o i l w i t h e x c e l l e n t f u e l s a v i n g p r o p e r t i e s ,
s u i t a b l e f o r d i e s e l e n g i n e s .
Background Art
[0002] I n t e r n a l c o m b u s t i o n e n g i n e s have b e e n
r e q u i r e d t o f u r t h e r i m p r o v e t h e f u e l s a v i n g p r o p e r t i e s
f o r r e c e n t e n v i r o n m e n t a l m e a s u r e s s u c h a s c o n t r o l o f
C 0 2 e m i s s i o n s .
An improvement i n f u e l economy by a
l u b r i c a t i n g o i l h a s b e e n c a r r i e d o u t by r e d u c i n g t h e
w o r k i n g v i s c o s i t y t o r e d u c e t h e v i s c o u s r e s i s t a n c e ( f o r
e x a m p l e , see P a t e n t L i t e r a t u r e 1 ) . However, t h e r e
e x i s t s a c e r t a i n v i s c o s i t y n e c e s s a r y f o r l u b r i c a t i o n
o f a n i n t e r n a l c o m b u s t i o n e n g i n e t h a t l i m i t s t h e
i m p r o v e m e n t . I n t e r n a l c o m b u s t i o n e n g i n e o i l s h a v e
been u s e d a s h y d r a u l i c p r e s s u r e s o u r c e s f o r d r i v i n g
v a l v e s and t h u s need t o h a v e a c e r t a i n d e g r e e o f
v i s c o s i t y t o m a i n t a i n t h e h y d r a u l i c p r e s s u r e . A l s o f o r
this reason, the engine oils have a limitation to the
reduction ofthe viscosity. In order to overcome these
limitations, heat management for an internal
combustion engine is being introduced. For example,
the required viscosityof an internal combustion engine
oil can be further reduced by lowering the maximum
working temperature thereof or by improving pumps of
an internal combustion engine to decrease the hydraulic
pressure required for the pumps, depending on the
purposes or use conditions of the internal combustion
engine. Whereby, further fuel saving can be achieved.
C i t a t i o n L i s t
P a t e n t L i t e r a t u r e
[0003] Patent Literature 1: Japanese Patent
Application Laid-Open Publication No. 2010-31082
Summary of I n v e n t i o n
T e c h n i c a l Problem
[0004] Conventional engine oils comprise a
lubricating base oil blended with a viscosity index
improver, a detergent dispersant, a friction modifier
and the like to fulfill their required properties.
However, the engine oils has caused a problem that with
the conventional blend balance, they cannot be reduced
in viscosity sufficiently as engines oils for an
internal combustion engine employing the
above-described heat management. That is, if the
necessary additives are used in their conventional
amount ratios, the viscosity increase caused by the
additives is significant, and thus the base oil
viscosity must be significantly reduced to reduce the
viscosity of the lubricating oil composition. Such
significant reduction of the base oil viscosity causes
an increase in engine oil consumption due to an increase
in evaporation loss and also leadsto failure to secure
the viscosity necessary for a high shear speed region
and thus increases the risk of defective lubrication.
The present invention has been made in view
of the above-described current situations and has an
object to provides a lubricating oil composition for
an internal combustion engine that is excellent in
functions as an engine oil for an internal combustion
engine employing heat management and in particular fuel
saving properties and detergency.
S o l u t i o n t o Problem
[0005] The present invention has been completed as
the results of extensive studies to achieve the above
object .
That is, the present invention relates to a
lubricating oil composition for an internal combustion
engine comprising (A) a base oil having 100°C kinematic
viscosity of 3.0 to 5.0 mm2/s and (B) a boronated
succinimide in an amount of 0.007 percent by mass or
more as boron and in an amount of 5 percent by mass or
less as the succinimide ashless dispersant, on the
basis of the total mass of the composition, (C) a
phenol-based antioxidant in an amount of 0.5 percent
bymass ormore and (D) aviscosityindeximproverhaving
a ratio of the weight average molecular weight and PSSI
of 1.2 x LO4 or greater in an amount of 0.1 to 5 percent
by mass, the composition having a 150°C HTHS viscosity
of 2.0 to 2.8 mPaes, a 100°C HTHS viscosity of 4.8 mPa.
s or lower and a viscosity index of 180 or greater.
[0006] The present invention also relates to the
foregoing lubricating oil composition for an internal
combustion engine wherein the ratio of the boronated
succinimide to the non-boronated succinimide is from
1.0 to 3.0 by weight.
The present invention also relates to the
foregoing lubricating oil composition for an internal
combustion engine wherein the ratio of the total
contentoftheboronated succinimide, Component (B) and
a non-boronated succinimide to the content of the
viscosity index improver, Component (D) is 6 or less.
Advantageous Effect of Invention
[0007] According to the present invention, a
lubricating oil composition for an internal combustion
engine is provided, which is excellent in functions as
an engine oil for an internal combustion engine
employing heat management and in particular fuel saving
properties and detergency.
The lubricating oil composition of the
present invention is suitably usedin gasoline engines,
diesel engines and gas engines for two- and
four-wheeled vehicles, power generators and
cogenerations and further not only those using fuel
with a sulfur content of 50 ppm by mass or less but also
various engines of ships and outboard motors.
Description of Embodiments
[OOOS] The present invention will be described in
detail.
The lubricating base oil of the lubricating
oil composition of the present invention may be a
mineral base oil or a synthetic base oil.
[0009] Examples of the mineral lubricating base
oils include those having a 100°C kinematic viscosity
satisfying the above-described requirement selected
from: paraffinic mineral base oils which can be
produced by subjecting a lubricating oil fraction
producedbyatmospheric- and/orvacuum-distillation of
crude oil, to any one of or any suitable combination
of refining processes selected from solvent
deasphalting, solvent extraction, hydrocracking,
solvent dewaxing, catalytic dewaxing, hydrorefining,
sulfuric acid treatment, and clay treatment;
n-paraffinic base oils; and iso-paraffinic base oils.
[OOlO] Examples of preferred lubricating base oils
include base oils produced using the following base
oils (1) to (8) as a feedstock by refining the feedstock
and/or a lubricating oil fraction recovered therefrom
in a given refining process and recovering a
lubricating oil fraction:
(1) a distillate oilproducedby atmospheric
distillation of a paraffin-base crude oil and/or a
mixed-base crude oil;
(2) a whole vacuum gas oil (WVGO) produced
by vacuum distillation of the topped crude of a
paraffin-base crude oil and/or a mixed-base crude oil;
(3) awaxproducedbydewaxing of lubricating
oil (slackwax) and/or a synthetic wax producedthrough
a gas to liquid (GTL) process (Fischer-Tropsch wax, GTL
wax) ;
(4) a mixed oil of one or more types selected
from base oils (1) to (3) and/or an oil produced by
mild-hydrocracking the mixed oil;
(5) a mixed oil of two or more types selected
from base oils (1) to (4) above;
(6) a deasphalted oil (DAO) produced by
deasphalting base oil (l), (2) ( 3 ) , (4) or (5);
(7) an oil produced by mild-hydrocracking
(MHC) base oil (6); and
(8) a mixed oil of two or more types selected
from base oils (1) to (7) above.
[OOll] The above-mentioned given refining process
is preferably hydro-refining such as hydrocracking or
hydrofinishing, solvent refining such as furfural
extraction, dewaxing such as solvent dewaxing and
catalytic dewaxing, clay refining with acidic clay or
active clay or chemical (acid or alkali) refining such
as sulfuric acid treatment and sodium hydroxide
treatment. In the present invention, any one or more
of these refining processes may be used in any
combination and order.
[0012] The lubricating base oil used in the present
invention is particularly preferably the following
base oil (9) or (10) produced by subjecting a base oil
selected from the above-described base oils (1) to (8)
or a lubricating oil fraction recovered therefrom to
a specific treatment:
(9) a hydrocracked base oil produced by
hydrocracking a base oil selected from base oils (1)
to (8) or a lubricating oil fraction recovered from the
base oil, and subjecting the resulting product or a
lubricating oil fraction recovered therefrom by
distillation, to a dewaxing treatment such as solvent
or catalytic dewaxing, optionally followed by
distillation; or
(10) a hydroisomerized base oil produced by
hydroisomerizing a base oil selected frombase oils (1)
to (8) or a lubricating oil fraction recovered from the
base oil, and subjecting the resulting product or a
lubricating oil fraction recovered therefrom by
distillation, to a dewaxing treatment such as solvent
or catalytic dewaxing, optionally followed by
distillation.
[0013] If necessary, a solvent refining process
and/or a hydrofinishing process may be carried out at
appropriate timing upon production of lubricating base
oil (9) or (10).
[0014] No particular limitation is imposed on the
catalyst usedinthe above-described hydrocracking and
hydroisomerizing. However, the catalyst is
preferably a hydrocracking catalyst comprising any one
of complex oxides having crackingactivity (for example,
silica-alumina, alumina boria, or silica zirconia) or
one or more types of such complex oxides bound with a
binder, usedas a support and ametalwithhydrogenation
capability (for example, one or more types of metals
of Groups VIa and VIII ofthe periodic table) supported
on the support, or a hydroisomerizing catalyst
comprising a support containing zeolite (for example,
ZSM-5, zeolite beta, or SAPO-11) and a metal with
hydrogenation capability, containing at least one or
more types of metals of Group VIII of the periodic table
and supported on the support. The hydrocracking and
hydroisomerizing catalysts may be laminated or mixed
so as to be used in combination.
[0015] No particular limitation is imposed on the
conditions under which the hydrocracking and
hydroisomerizing are carried out. Preferably, the
hydrogen partial pressure is from 0.1 to 20 MPa, the
average reaction temperature is from 150 to 450°C, the
LHSV is from 0.1 to 3.0 hr-l, and the hydrogen/oil ratio
is from 50 to 20000 scf/b.
[0016] The 100°C kinematic viscosity of the
lubricating base oil of the present invention is
necessarily 5.0 mm2/s or lower, preferably 4.5 mm2/s
or lower, particularly preferably 4.2 mm2/s or lower.
Whilst, the kinematic viscosity is necessarily 3.0
mm2/s or higher, preferably 3.4 mm2/s or higher, more
preferably 3.7 mm2/s or higher.
The 100°C kinematic viscosity used herein
refers to the 100°C kinematic viscosity determined in
accordance with ASTM D-445.
If the 100°C kinematic viscosity of the
lubricating base oil exceeds 5 mm2/s, the resulting
composition would be degraded in low temperature
viscosity characteristics and may not obtain
sufficiently improved fuel saving properties. If the
100°C kinematic viscosity is lower than 3.0 mm2/s, the
resulting lubricating oil composition would be poor in
lubricity due to its insufficient oil film formation
at lubricating sites and would be large in evaporation
loss of the composition.
[0017] The viscosity index of the lubricating base
oil of the present invention is preferably 120 or
greater, more preferably 125 or greater, more
preferably 130 or greater, most preferably 140 or
greater. Whilst, theviscosityindexis preferably160
or less.
A viscosity index of less than 120 would not
only cause the viscosity-temperature characteristics,
thermal/oxidation stability, anti-evaporation
properties to degrade but also cause the friction
coefficient to increase and likely cause the friction
coefficient to increase and cause the antiwear
p r o p e r t i e s t o d e g r a d e . A v i s c o s i t y i n d e x o f g r e a t e r
t h a n 160 would t e n d t o d e g r a d e t h e low t e m p e r a t u r e
v i s c o s i t y c h a r a c t e r i s t i c s .
The v i s c o s i t y i n d e x r e f e r r e d h e r e i n d e n o t e s
t h e v i s c o s i t y i n d e x m e a s u r e d i n a c c o r d a n c e w i t h J I S K
2283-1993.
[ 0 0 1 8 ] The s u l f u r c o n t e n t of t h e l u b r i c a t i n g b a s e
o i l u s e d i n t h e p r e s e n t i n v e n t i o n d e p e n d s on t h e s u l f u r
c o n t e n t o f t h e raw m a t e r i a l t h e r e o f . F o r e x a m p l e , when
a raw m a t e r i a l c o n t a i n i n g s u b s t a n t i a l l y no s u l f u r s u c h
a s a s y n t h e t i c wax component p r o d u c e d b y
F i s c h e r - T r o p s c h r e a c t i o n i s u s e d , a l u b r i c a t i n g b a s e
o i l c o n t a i n i n g s u b s t a n t i a l l y no s u l f u r c a n b e p r o d u c e d .
The l u b r i c a t i n g b a s e o i l u s e d i n t h e p r e s e n t
i n v e n t i o n c o n t a i n s s u l f u r i n an amount of p r e f e r a b l y
10 mass ppm o r l e s s , more p r e f e r a b l y 5 mass ppm o r l e s s ,
andparticularlypreferably c o n t a i n s no s u l f u r w i t h t h e
o b j e c t i v e of f u r t h e r i m p r o v i n g t h e r m a l / o x i d a t i o n
s t a b i l i t y and l o w e r i n g t h e s u l f u r c o n t e n t .
[ 0 0 1 9 ] The %Cp of t h e l u b r i c a t i n g b a s e o i l u s e d i n
t h e p r e s e n t i n v e n t i o n i s p r e f e r a b l y 70 o r g r e a t e r , more
p r e f e r a b l y 80 o r g r e a t e r , more p r e f e r a b l y 85 o r g r e a t e r ,
most p r e f e r a b l y 90 o r g r e a t e r a n d p r e f e r a b l y 95 o r l e s s .
I f t h e % C p o f t h e l u b r i c a t i n g b a s e o i l i s l e s s
t h a n 7 0 , t h e r e s u l t i n g c o m p o s i t i o n would t e n d t o be
degraded in viscosity-temperature characteristics,
thermal/oxidation stability and friction
characteristics and when blendedwith additives, would
tend to degrade the efficacy thereof. The %Cp is
preferably 95% or less because the %CN of the base oil
is preferably on the order of 5% in view of solubility
of additives.
[0020] The %CA of the lubricating base oil used in
the present invention is preferably 2 or less, more
preferably 1 or less, more preferably 0.8 or less,
particularly preferably 0.5 or less, most preferably
0. If the %CA of the lubricating base oil exceeds 2,
the resulting composition would tend to be degraded in
viscosity-temperature characteristics,
thermal/oxidation stability and fuel saving
properties.
[0021] The %Cp and %CA referred in the present
invention denote the percentage of paraffin carbon
number in the total carbon number and the percentage
ofthe aromatic carbonnumber in the total carbon number,
respectively, determined by a method (n-d-M ring
analysis) in accordance with ASTM D 3238-85.
[0022] Examples of the synthetic base oil include
poly-a-olefins and hydrogenated compounds thereof;
isobutene oligomers and hydrogenated compounds
thereof; isoparaffins; alkylbenzenes; and
alkylnaphthalenes, among which poly-a-olefins are
preferable.
Typical examples of poly-a-olefins include
oligomers or cooligomers of a-olefins having 2 to 32,
preferably 6 to 16 carbon atoms, such as 1-octene
oligomer, decene oligomer, oligomers or cooligomers of
1-dodecene, and hydrogenated compounds thereof.
These synthetic base oils may be those that
are commercially available if their viscosityis within
the same range as the aforesaid mineral base oils.
These synthetic base oils may be each used alone or in
combination with the above-describedmineralbase oils.
No particular limitation is imposed on the mix ratio
of these bases oils.
[0023] The engine oil of the present invention
contains a boronated succinimide as Component (B).
In the present invention, the boronated
succinimide is preferably mixed with a non-boronated
succinimide. The non-boronated succinimide denotes
succinimide before being boronated.
[00241 Examples of the succinimide include
succinimides having at least one alkylor alkenylgroup
having 40 to 400, preferably 60 to 350 carbon atoms per
molecule or derivatives thereof. If the carbon number
ofthe alkylor alkenylgroupis fewerthan 40, Component
(B) would tend to be degraded in solubility in the
lubricating base oil. Whereas, if the carbon number
of the alkyl or alkenyl group is more than 400, the
resulting lubricating oil composition would be
degraded in low-temperature fluidity. The alkyl or
alkenyl group may be straight-chain or branched but is
preferably a branched alkyl or alkenyl group derived
from oligomers of olefins such as propylene, l-butene
or isobutylene or a cooligomer of ethylene and
propylene. The succinimide is preferably a mono- or
bis-succinimide.
[0025] No particular limitation is imposed on the
method for producing the succinimide. For example, a
method may be used, wherein an alkyl or alkenyl
succinimide produced by reacting a compound having an
alkyl or alkenyl group having 40 to 400 carbon atoms
with maleic anhydride at a temperature of 100 to 200°C
is reacted with a polyamine. Examples of the polyamine
include diethylene triamine, triethylene tetramine,
tetraethylene pentamine, and pentaethylene hexamine.
[0026] Boronation is generally carried out by
allowing succinimide to react with boric acid to
neutralize the whole or part of the remaining amino
and/or imino groups.
Examples of amethodofproducing aboronated
succinimide are those disclosed in Japanese Patent
Publication Nos. 42-8013 and 42-8014 and Japanese
Laid-Open Patent Publication Nos. 51-52381 and
51-130408. More specifically, a boronated
succinimide may be produced by mixing polyamine and
polybutenylsuccinic acid (anhydride) with a boron
compound such as boric acid, a boric acid ester, or a
borate in a solvent including alcohols, organic solvent
such as hexane or xylene, or a light fraction
lubricating base oil and by heating the mixture under
appropriate conditions. Theboron content oftheboron
acid-modified succinimide produced in this manner is
generally from 0.1 to 45 percent by mass.
[0027] No particular limitation is imposed on the
boron content of the boronated succinimide used in the
present invention, which is, however, usually from 0.1
to 3 percent by mass, preferably 0.2 percent by mass
or more, more preferably 0.3 percent by mass or more,
more preferably 0.5 percent by mass or more. The boron
content is preferably 2 percent by mass or less, more
preferably1.5 percent by mass or less, more preferably
1 percent by mass or less.
The boronated succinimide is preferably a
boronated succinimide, particularly desirously a
b o r o n - c o n t a i n i n g b i s - t y p e s u c c i n i m i d e , w i t h a b o r o n
c o n t e n t w i t h i n t h e a b o v e - d e s c r i b e d r a n g e . I f t h e b o r o n
c o n t e n t i s m o r e t h a n 3 p e r c e n t b y m a s s , n o t o n l y c o n c e r n s
a b o u t s t a b i l i t y a r e a r i s e n , b u t a l s o c o n c e r n s a b o u t
i n f l u e n c e s on an e x h a u s t - g a s a f t e r - t r e a t m e n t s y s t e m
would be a r i s e n a c c o m p a n i e d w i t h an i n c r e a s e i n
s u l f a t e d a s h c o n t e n t due t o t h e t o o much b o r o n i n t h e
c o m p o s i t i o n . I f t h e b o r o n c o n t e n t i s l e s s t h a n 0 . 1
p e r c e n t by mass, e f f e c t s of a d d i t i o n of t h e b o r o n a t e d
s u c c i n i m i d e c a n n o t be e x p e c t e d .
[ 0 0 2 8 ] I n t h e p r e s e n t i n v e n t i o n , t h e b o r o n a t e d
s u c c i n i m i d e i s p r e f e r a b l y u s e d i n t h e form of a m i x t u r e
w i t h a n o n - b o r o n a t e d s u c c i n i m i d e . The r a t i o of t h e
a b o v e - d e s c r i b e d b o r o n a t e d s u c c i n i m i d e and t h e
n o n - b o r o n a t e d s u c c i n i m i d e ( b o r o n a t e d
succinimide/non-boronated s u c c i n i m i d e ) i s p r e f e r a b l y
w i t h i n t h e r a n g e of 1 . 0 t o 3 . 0 , more p r e f e r a b l y 1 . 2 o r
g r e a t e r a n d p r e f e r a b l y 2 . 6 o r l e s s , more p r e f e r a b l y 2 . 0
o r l e s s , more p r e f e r a b l y 1 . 5 o r l e s s by w e i g h t r a t i o .
I f t h e r a t i o o f t h e b o r o n a t e d s u c c i n i m i d e and
t h e n o n - b o r o n a t e d s u c c i n i m i d e e x c e e d s 3 . 0 , n o t o n l y
c o n c e r n s a b o u t s t a b i l i t y a r e a r i s e n , b u t a l s o c o n c e r n s
a b o u t i n f l u e n c e s on an e x h a u s t - g a s a f t e r - t r e a t m e n t
s y s t e m would be a r i s e n a c c o m p a n i e d w i t h an i n c r e a s e i n
s u l f a t e d a s h c o n t e n t due t o t h e t o o much b o r o n i n t h e
c o m p o s i t i o n . W h i l s t , t h e r a t i o i s l e s s t h a n 1 . 0 ,
e f f e c t s of a d d i t i o n o f t h e b o r o n a t e d s u c c i n i m i d e c a n n o t
b e e x p e c t e d .
The r e a s o n w h y t h e m i x t u r e i s p r e f e r a b l y u s e d
i n c o m b i n a t i o n i s t h a t t h e b o r o n a t e d s u c c i n i m i d e a l o n e
r e s u l t s i n a n u n s t a b l e b o r o n a t e d compound, w h i c h w o u l d
o f t e n p r e c i p i t a t e and t h e m i x t u r e i s e x c e l l e n t i n t h e
b a l a n c e o f d e t e r g e n c y .
[ 0 0 2 9 ] The c o n t e n t o f Component ( B ) o f t h e
l u b r i c a t i n g o i l c o m p o s i t i o n f o r a n i n t e r n a l c o m b u s t i o n
e n g i n e a c c o r d i n g t o t h e p r e s e n t i n v e n t i o n i s
n e c e s s a r i l y 0 . 0 0 7 p e r c e n t b y m a s s o r m o r e , p r e f e r a b l y
0 . 0 1 p e r c e n t b y m a s s o r more a n d p r e f e r a b l y 0 . 1 p e r c e n t
by mass o r l e s s , more p r e f e r a b l y 0 . 0 5 p e r c e n t by mass
o r l e s s , more p r e f e r a b l y 0 . 0 2 p e r c e n t by mass o r l e s s
a s b o r o n on t h e b a s i s of t h e t o t a l mass of t h e
l u b r i c a t i n g o i l c o m p o s i t i o n f o r a n i n t e r n a l c o m b u s t i o n
e n g i n e .
T h i s i s b e c a u s e i f t h e c o n t e n t i s l e s s t h a n
0 . 0 0 7 p e r c e n t by mass o r l e s s , e f f e c t s b y b o r o n c a n n o t
be e x p e c t e d and i f t h e c o n t e n t e x c e e d s 0 . 1 p e r c e n t by
m a s s , t h e c o m p o s i t i o n would l a c k i n s t a b i l i t y .
I n t h e p r e s e n t i n v e n t i o n , t h e t o t a l c o n t e n t
of t h e b o r o n a t e d s u c c i n i m i d e a n d t h e n o n - b o r o n a t e d
s u c c i n i m i d e i s 5 p e r c e n t by mass o r l e s s on t h e b a s i s
o f t h e t o t a l mass o f t h e c o m p o s i t i o n .
[ 0 0 3 0 ] The m o l e c u l a r w e i g h t o f Component ( B ) i s
d e t e r m i n e d by t h e c a r b o n number of a l k y l o r a l k e n y l
g r o u p a n d s t r u c t u r e o f t h e p o l y a m i n e b u t i s p r e f e r a b l y
2500 o r g r e a t e r , more p r e f e r a b l y 3000 o r g r e a t e r , more
p r e f e r a b l y 3500 o r g r e a t e r . W h i l s t , t h e m o l e c u l a r
w e i g h t i s p r e f e r a b l y 10000 o r l e s s , more p r e f e r a b l y
7000 o r l e s s , more p r e f e r a b l y 5000 o r l e s s . I f t h e
m o l e c u l a r w e i g h t i s l e s s t h a n 2500, t h e r e s u l t i n g
compositionwouldbelessindetergencyeffect. W h i l s t ,
if t h e m o l e c u l a r w e i g h t e x c e e d s 1 0 0 0 0 , t h e r e s u l t i n g
c o m p o s i t i o n would be d e t e r i o r a t e d i n low t e m p e r a t u r e
v i s c o s i t y .
[ 0 0 3 1 ] The b o r o n a t e d s u c c i n i m i d e a n d n o n - b o r o n a t e d
s u c c i n i m i d e a r e g e n e r a l l y p r o v i d e d i n a s t a t e where
t h e y a r e d i s s o l v e d i n a s o l v e n t e q u i v a l e n t t o a
l u b r i c a t i n g b a s e o i l f o r m a n u f a c t u r i n g r e a s o n s . The
c o n t e n t r e f e r r e d i n t h e p r e s e n t i n v e n t i o n d e n o t e s t h e
n e t c o n t e n t of t h e compound e x c l u d i n g t h e s o l v e n t .
T h e r e f o r e , f o r e x a m p l e , when s u c c i n i m i d e
d i s s o l v e d i n a s o l v e n t i s u s e d , t h e e f f e c t i v e
c o n c e n t r a t i o n o f t h e s u c c i n i m i d e i s c a l c u l a t e d a n d t h e n
s u c c i n i m i d e i s a d d e d i n s u c h an amount t o be t h e n e t
a m o u n t .
For e x a m p l e , t h e e f f e c t i v e c o n c e n t r a t i o n m a y
be calculated in the following manner. Into a 50 ml
volume sack-like rubber made from natural rubber is
accurately weighed out 1 to 2 grams of an additive
solution containingthe succinimide. An upper portion
of the rubber is tied with thread or the like so that
the content does not spills out from the rubber sack.
The rubber sack is then placed in a Soxhlet extractor
into which a piece of filter paper has been put to
extract the solvent using heptane as an extract solvent
at 50°C for 24 hours. After completion of the
extraction, the rubber sack containing the sample is
allowed to stand at room temperature for 24 hours and
measured. The sample remaining in the rubber sack is
the succinimide and the effective concentration can be
calculated from the weight of the sample when placed
initially in the rubber sack.
[0032] The engine oil of the present invention
contains a phenol-based antioxidant as Component (C) .
Examples of the phenol-based ashless
antioxidant include: phenol-based antioxidants
containing no sulfur as a constitution element such as
4,4'-rnethylenebis(2,6-di-tert-buty1phenol),
4,4'-bis(2,6-di-tert-butylphenol),
4,4'-bis(2-methyl-6-tert-butylphenol),
2,2'-methy1enebis(4-ethy1-6-tert-buty1phen01),
2,2'-methylenebis(4-methy1-6-tert-butylphenol),
4,41-butylidenebis(3-methyl-6-tert-butylphen01),
4,4'-isopropylidenebis(2,6-di-tert-butylphenol),
2,21-methylenebis(4-methyl-6-nonylphenol),
2,21-isobutylidenebis(4,6-dimethylphenol),
2,21-methylenebis(4-methyl-6-cyclohexylphen01),
2,6-di-tert-butyl-4-methylphenol,
2,6-di-tert-butyl-4-ethylphenol,
2,4-dimethyl-6-tert-butylphenol,
2,6-di-tert-a-dimethylamino-p-cresol,
2,6-di-tert-butyl-4(N,N1-dimethy1amin0methy1phen01),
octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)
propionate,
tridecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)
propionate,
pentaerythrityl-tetraquis[3-(3,5-di-tert-butyl-4-
hydroxyphenyl)propionate],
octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)
propionate,
octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)
propionate, and
octyl-3-(3-methyl-5-tert-butyl-4-hydroxyphenyl)
propionate; phenol-based ashless antioxidants
containing sulfur as a constitutional elements such as
4,41-thiobis(2-methyl-6-tert-butylphenol),
4,4'-thiobis(3-methyl-6-tert-butylphenol),
2,2'-thiobis(4-methyl-6-tert-butylphenol),
bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)sulfide,
bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide, and
2,2'-thio-diethylenebis[3-(3,5-di-tert-butyl-4-
hydroxypheny1)propionatel; and mixtures thereof.
[0033] Among these, preferred examples include
hydroxyphenyl-substituted ester-based antioxidants
that are esters of hydroxyphenyl group-substituted
fatty acids and alcohols having 4 to 12 carbon atoms
such as octyl-3-
(3,5-di-tert-butyl-4-hydroxypheny1)propionate and
octyl-3-(3-metyl-5-tert-butyl-4-hydroxyphenyl)
propionate) and bisphenol-based ashless antioxidants.
More preferred examples include
hydroxyphenyl-substituted ester-based antioxidants.
Phenolic compounds with a molecular weight of 240 or
greater are preferable because they are high in
decomposition temperature and thus can exhibit their
effects under higher temperature conditions.
[0034] The engine oil may further contain an
amine-based ashless antioxidant. Examples of the
amine-based ashless antioxidant include
phenyl-a-naphthylamine,
alkylphenyl-a-naphthylamines and
dialkyldiphenylamines.
[0035] The engine oil of the present invention
contains a viscosity index improver having a
weight-average molecular weight and PSSI ratio of
1. 2x104 or greater as Component (D) .
[0036] The weight-average molecular weight (MW) of
the viscosity index improver used in the present
invention is preferably 600,000 or less, more
preferably 500, 000 or less, more preferably 460,000 or
less. The Mw is preferably 10,000 or greater, more
preferably 50,000 or greater, more preferably 100,000
or greater, particularly preferably 200,000 or
greater.
If the viscosity index improver has a weight
average molecular weight of less than 10,000, it would
be less effective in viscosity index enhancement when
it is dissolved in a lubricating base oil and the
resulting composition would not only be poor in fuel
saving properties and low temperature viscosity
characteristics but also be high in production cost.
If the viscosity index improver has a weight-average
molecular weight of greater than 600,000, it would
exert the viscosityincreasing effect too much and thus
the resulting compositionwouldnotonlybepoorin fuel
saving properties and low temperature viscosity
characteristics but alsobe degraded in shear stability,
solubility in a lubricating base oil and storage
stability.
[0037] The viscosity index improver used in the
present inventionhas a PSSI (permanent shear stability
index) of necessarily 20 or less, more preferably 17
or less, more preferably 16 or less, particularly
preferably 15 or less. If the PSSI exceeds 20, the
resulting composition would be degraded in shear
stability and thus needed to be enhanced in initial
kinematic viscosity, possibly resulting in degraded
fuel saving properties. If the PSSI is less than 1,
the viscosity index improver would be less effective
in viscosity index enhancement when it is dissolved in
a lubricating base oil and thus the resulting
composition would not only be poor fuel saving
properties and low temperature viscosity
characteristics but also increased in production cost.
The PSSI is, therefore, preferably 1 or greater.
[0038] The ratio of the weight-average molecular
weight and PSSI (MW/PSSI) of the viscosity index
improver used in the present invention is necessarily
1. 2x104 or greater, preferably 1 . 5 ~ 1 o0r~ g reater, more
preferably 2 . 0 ~ 1 0or~ g reater. If the MW/PSSI is less
than 1.2x104, the resulting composition would be
degraded in fuel saving properties and low temperature
startability, i.e., viscosity temperature
characteristics and low temperature viscosity
characteristics.
[I30391 Specific examples of the compound include
non-dispersant type or dispersant type ester
group-containing viscosity index improvers,
non-dispersant type or dispersant type
poly(meth)acrylate viscosity index improvers,
styrene-dienehydrogenated copolymers, non-dispersant
type or dispersant type ethylene-a-olefin copolymers
or hydrogenated compoundsthereof, polyisobutylene and
hydrogenated compounds thereof, styrene-maleic
anhydride ester copolymer, polyalkylstyrenes,
(meth)acrylate-olefin copolymers and mixtures
thereof.
[0040] The content of Component (D) in the
lubricating oil composition of the present invention
is preferably from 0.1 to 5 percent by mass, more
preferably 0.5 percent by mass or more, more
preferably froml.O percent bymass or more on the basis
of the total mass of the composition. The content of
Component (D) is preferably 3 percent by mass or less,
more preferably 2 percent by mass or less. If the
content is less than 0.1percent by mass, the resulting
composition would be insufficient in low temperature
characteristics. If the content exceeds 5 percent by
mass, the resulting composition would be degraded in
shear stability.
As with the above-described succinimide, a
viscosity index improver is generally provided in a
state where it is dissolved in a solvent equivalent to
a lubricating base oil, the content of the viscosity
index improver referred herein denote the net content
excluding the solvent.
[0041] In the present invention, the ratio of the
total content of the boronated succinimide, Component
(B) and the non-boronated succinimide to the content
of the viscosity index improver, Component (D) is 6 or
less.
That is, this indicates that there is a
certain limit to the ratio of the total content of the
boronated succinimide, Component (B) and the
non-boronated succinimide to the content of the
viscosity index improver, Component (D). This is
because although both Component (D) and Component (B)
involve an effect on the increase of the composition
viscosity, Component (B) in particular involve an
effect largely on the increase of the low temperature
viscosity and thus it is necessary to restrain
Component (B) from contributing to the viscosity
increase rate of the composition.
Therefore, the ratio of the total content of
the boronated succinimide, Component (B) and the
non-boronated succinimide to the content of the
viscosity index improver, Component (D) is 6 or less,
preferably 5 or less, more preferably 4 or less, more
preferably 3.5 or less, most preferably 3 or less.
[0042] The lubricating oil composition for an
internal combustion engines of the present invention
may be blended with any additives that have been
generally used in a lubricating oil depending on the
purposes in order to further enhance the properties.
Examples of such additives include metallic detergents,
friction modifiers, ashless dispersants other than
Component (B), antiwear agents (or extreme pressure
additives), antioxidants other than Component (C),
corrosion inhibitors, rust inhibitors, demulsifiers,
metal deactivators, and anti-foaming agents.
[0043] Examples of the metallic detergent include
normal salts and/or basic salts of alkali
metal/alkaline earth metal sulfonates, alkali
metal/alkaline earth metal phenates, and alkali
metal/alkaline earth metal salicylates. Examples of
the alkali metal include sodium and potassium.
Examples ofthe alkaline earthmetal include magnesium,
calcium and barium. Preferred are magnesium and
calcium, and particularly preferred is calcium.
[0044] Examples of the friction modifier include
any compounds that are usually used as a friction
modifier for lubricating oils, for example organic
molybdenum compounds and ashless friction modifiers.
Examples of the organic molybdenum compound
include molybdenum dithiocarbamate, molybdenum
dihiophosphate, molybdenum-amine complex,
molybdenum-succinimide complex, molybdenum salts of
organic acids, and molybdenum salts of alcohols.
Examples of the ashless friction modifier
include ashless friction modifiers such as amine
compounds, fatty acid esters, fatty acid amides, fatty
acids, aliphatic alcohols, and aliphatic ethers, each
having at least one alkyl or alkenyl group having 6 to
30 carbon atoms, in particular straight-chain alkyl or
alkenyl group having 6 to 30 carbon atoms per molecule.
Alternative examples include various ashless friction
modifiers as exemplified in International Publication
No. 2005/037967 Pamphlet.
In the present invention, most preferred is
molybdenum dithiocarbamate because it can mostly
reduce friction.
[0045] The antiwear agent (or extreme pressure
additive) may be any antiwear agents or extreme
pressure additives that are used for lubricating oil.
For example, sulfuric-, phosphoric- and
sulfuric-phosphoric extreme pressure additives may be
used. Specific examples include zinc
dialkyldithiophosphate (ZnDTP), phosphorus acid
esters, thiophosphorus acid esters, dithiophosphorus
acid esters, trithiophosphorus acid esters, phosphoric
acid esters, thiophosphoric acid esters,
dithiophosphoric acid esters, trithiophosphoric acid
esters, amine salts, metal salts or derivatives thereof,
dithiocarbamates, zinc dithiocaramates, disulfides,
polysulfides, sulfurized olefins and sulfurized fats
and oils. Among these antiwear agents, preferred are
sulfuric extreme pressure additives, and particularly
preferred are zinc dialkyldithiophosphate.
[0046] Examples of the corrosion inhibitor include
benzotriazole-, tolyltriazole-, thiadiazole-, and
imidazole-types compounds.
[00471 Examples of the rust inhibitor include
petroleum sulfonates, alkylbenzene sulfonates,
dinonylnaphthalene sulfonates, alkenyl succinic acid
esters, and polyhydric alcohol esters.
[0048] Examples of the demulsifier include
polyalkylene glycol-based non-ionic surfactants such
as polyoxyethylenealkyl ethers,
polyoxyethylenealkylphenyl ethers, and
polyoxyethylenealkylnaphthyl ethers.
[0049] Examples of the metal deactivator include
imidazolines, pyrimidine derivatives,
alkylthiadiazoles, mercaptobenzothiazoles,
benzotriazoles and derivatives thereof,
1,3,4-thiadiazolepolysulfide,
1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamatef
2-(alkyldithio)benzoimidazole, and
P-(0-carboxybenzylthio)propionitrile.
[0050] Examples of the anti-foaming agent include
silicone oil with a 25°C kinematic viscosity of 1000
to 100,000 mm2/s, alkenylsuccinic acid derivatives,
esters of polyhydroxy aliphatic alcohols and
long-chain fatty acids, aromatic amine salts of
methylsalicylate and o-hydroxybenzyl alcohol.
[ 0 0 5 1 ] When these additives are contained in the
lubricating oil composition for an internal combustion
engine of the present invention, they are contained in
an amount of 0.01 to 10 percent by mass on the total
composition mass basis.
[0052] The 150°C HTHS viscosity of the lubricating
oil composition for an internal combustion engine of
t h e p r e s e n t i n v e n t i o n i s 2.8 mPaas o r l o w e r , p r e f e r a b l y
2.6 mPaas o r l o w e r , more p r e f e r a b l y 2.4 mPaSs o r l o w e r
and 2.0 mPaSs o r h i g h e r , p r e f e r a b l y 2 . l m P a . s o r h i g h e r ,
more p r e f e r a b l y 2.2 mPaSs o r h i g h e r .
I f t h e 150°C HTHS v i s c o s i t y e x c e e d s 2.8 mPas
s, t h e c o m p o s i t i o n may n o t o b t a i n s u f f i c i e n t f u e l
s a v i n g p r o p e r t i e s . I f it i s l o w e r t h a n 2.0 m P a - s , t h e
c o m p o s i t i o n would l a c k l u b r i c i t y .
The 150°C HTHS v i s c o s i t y r e f e r r e d h e r e i n
d e n o t e s t h e h i g h t e m p e r a t u r e h i g h s h e a r v i s c o s i t y a t
100°C d e f i n e d i n a c c o r d a n c e w i t h ASTM D4683.
[0053] The 100°C HTHS v i s c o s i t y o f l u b r i c a t i n g o i l
c o m p o s i t i o n f o r an i n t e r n a l c o m b u s t i o n e n g i n e of t h e
p r e s e n t i n v e n t i o n i s 4.8 mPaSs o r l o w e r , p r e f e r a b l y 4.7
mPa-s o r l o w e r , more p r e f e r a b l y 4.6 mPaSs o r l o w e r ,
p a r t i c u l a r l y p r e f e r a b l y 4.5 mPaWs o r l o w e r .
I f t h e 100°C HTHS v i s c o s i t y e x c e e d s 4.8 mPa*
s , t h e r e s u l t i n g c o m p o s i t i o n would n o t o b t a i n
s u f f i c i e n t f u e l s a v i n g p r o p e r t i e s . I f t h e 100°C HTHS
v i s c o s i t y i s l o w e r t h a n 3.9 m P a S s , it c o u l d c a u s e t h e
e n g i n e h y d r a u l i c p r e s s u r e t o be i n s u f f i c i e n t and t h u s
i s p r e f e r a b l y 3.9 mPaSs o r h i g h e r .
The 100°C HTHS v i s c o s i t y r e f e r r e d h e r e i n
d e n o t e s t h e h i g h t e m p e r a t u r e h i g h s h e a r v i s c o s i t y a t
100°C d e f i n e d i n a c c o r d a n c e w i t h ASTM D6616.
[0054] The HTHS viscosity (150°C)/HTHS viscosity
(100°C) is preferably 0.45 or higher, more preferably
0.047 or higher, more preferably 0.049 or higher, most
preferably 0.51or higher. This is because if the HTHS
viscosity (100°C) is lower than the HTHS viscosity
(150°C), the composition would be excellent in fuel
saving properties.
[0055] The 100°C kinematic viscosity of the
lubricating oil composition for an internal combustion
engine of the present invention is preferably 8 mm2/s
or lower, more preferably 7.5 mm2/s or lower, more
preferably 7 mm2/s or lower, most preferably 6.8 mm2/s
or lower. The 100°C kinematic viscosity of the
lubricating oil composition for an internal combustion
engine of the present invention is preferably 4 mm2/s
or higher, more preferably 5 mm2/s or higher, more
preferably 6 mm2/s or higher, most preferably 6.3 mm2/s
or higher. The 100°C kinematic viscosity used herein
refers to the 100°C kinematic viscosity determined in
accordance with ASTM D-445. If the 100°C kinematic
viscosity is lower than 4 mm2/s, the resulting
lubricating oil composition would lack lubricity. If
the 100°C kinematic viscosity exceeds 8 mm2/s, the
resulting composition would not obtain the requiredlow
temperature viscosity and sufficient fuel saving
properties.
[00561 The viscosity index of the lubricating oil
composition for an internal combustion engine of the
present invention is 180 or greater, more preferably
190 or greater, more preferably 200 or greater,
particularly preferably 210 or greater, most
preferably 220 or greater. If the lubricating oil
composition of the present invention has a viscosity
index of less than 180, it would be difficult to improve
the fuel saving properties while maintainingthe 150°C
HTHS viscosity and to reduce the low temperature
viscosity at -35OC. If the viscosity index of the
lubricating oil composition of the present invention
is greater than 300, the resulting composition would
be degraded in evaporability and cause malfunctions
caused by the lack of solubility of additives and the
incompatibility with seal materials and the viscosity
index is, therefore, preferably 300 or less.
Examples
[0057] The present invention will be described in
more detail below with reference to the following
Examples and Comparative Examples but are not limited
thereto.
[0058] (Examples 1 to 5, Comparative Examples 1 to
Lubricating oil compositions of the present
invention (Example 1 to 5) and those for comparison
(Comparative Examples 1 to 5) were each prepared to
carry out a hot tube test. The results are set forth
in Table 1 below.
The test was carried out in accordance with
JPI 5s-55-99 under conditions where the amount of
samples was 1-0 g, the test temperature was 300°C, and
the test time was 16 hours.
[0059]
[Table 11
40°C: 15.6 mm2/s, 1 0 0 k 3.8mm2/s, VI: 142, sulfur content: